Delivery Biology Room Daily

New Breeding Ground For Endangered Whales? High Numbers Of Right Whales Seen In Gulf Of Maine

2009-01-05T22:27:00.004+07:00

A large number of North Atlantic right whales have been seen in the Gulf of Maine in recent days, leading right whale researchers at NOAA’s Northeast Fisheries Science Center to believe they have identified a wintering ground and potentially a breeding ground for this endangered species.

Three North Atlantic right whales are visible at the surface on Jordans Basin.
A fourth whale is visible just below the surface at lower left. (Credit: NOAA/Misty Niemeyer)

The NEFSC’s aerial survey team saw 44 individual right whales on Dec. 3 in the Jordan Basin area, located about 70 miles south of Bar Harbor, Maine. Weather permitting, the team regularly surveys the waters from Maine to Long Island and offshore 150 miles to the Hague Line (the U.S.-Canadian border), an area about 25,000 square nautical miles.

“We’re excited because seeing 44 right whales together in the Gulf of Maine is a record for the winter months, when daily observations of three to five animals are much more common,” said Tim Cole, who heads the team. “Right whales are baleen whales, and in the winter spend a lot of time diving for food deep in the water column. Seeing so many of them at the surface when we are flying over an area is a bit of luck.”

Just a few days later, on Dec. 6, the team observed only three right whales on Cashes Ledge, about 80 miles east of Gloucester, Mass. Cole says the whales are known to be in the region, but actually seeing them on any given aerial survey is unpredictable. On Dec. 14, the team saw 41 right whales just west of Jordan Basin.

An estimated 100 female North Atlantic right whales head south in winter to give birth in the waters off Florida and Georgia, but little is known about where other individual right whales in the population go in winter, largely due to difficult surveying conditions.

Given the large geographical area over which North Atlantic right whales can occur, Cole and NEFSC colleagues developed an aerial grid system a few years ago for the Gulf of Maine and waters around Cape Cod to ensure complete coverage of the region. The grid resulted in consistent surveys of areas infrequently surveyed in the past, like Jordan Basin and the Great South Channel, and have shown that whales congregate in certain areas at certain times.

With a population estimated to be about 325 whales, knowing where the whales are at any time is critical to protect them. Finding an aggregation of whales can trigger a management action affording protection, such as slowing ship speeds in the vicinity of the whales. On Dec. 9, new federal speed rules for large ships went into effect to reduce ship strikes, to which North Atlantic right whales are particularly vulnerable.

NOAA understands and predicts changes in the Earth's environment, from the depths of the ocean to the surface of the sun, and conserves and manages our coastal and marine resources.

SOURCE : National Oceanic And Atmospheric Administration

Hot Southern Summer Threatens Coral With Massive Bleaching Event

2009-01-05T22:14:00.006+07:00

A widespread and severe coral bleaching episode is predicted to cause immense damage to some of the world’s most important marine environments over the next few months.

A widespread and severe coral bleaching episode
is predicted to cause immense damage to some of the world's
most important marine environments over the next few months.
(Credit: iStockphoto/Tammy Peluso)

A report from the US Government’s National Oceanic and Atmospheric Administration (NOAA) predicts severe bleaching for parts of the Coral Sea, which lies adjacent to Australia’s Great Barrier Reef, and the Coral Triangle, a 5.4 million square kilometre expanse of ocean in the Indo-Pacific which is considered the centre of the world’s marine life.

“This forecast bleaching episode will be caused by increased water temperatures and is the kind of event we can expect on a regular basis if average global temperatures rise above 2 degrees,” said Richard Leck, Climate Change Strategy Leader for WWF’s Coral Triangle Program.

The bleaching, predicted to occur between now and February, could have a devastating impact on coral reef ecosystems, killing coral and destroying food chains. There would be severe impacts for communities in Australia and the region, who depend on the oceans for their livelihoods.

The Coral Triangle, stretching from the Philippines to Malaysia and Papua New Guinea, is home to 75 per cent of all known coral species. More than 120 million people rely on its marine resources.

“Regular bleaching episodes in this part of the world will have a massive impact on the region’s ability to sustain local communities,” said Leck. “In the Pacific many of the Small Island Developing States, such as the Solomon Islands, rely largely on the coast and coastal environments such as coral reefs for food supply. This is a region where alternative sources of income and food are limited.

“Time is crucial and Australia needs to step up to the plate. Following the government’s lack of resolve to seriously reduce future domestic carbon emissions, Australia has a huge role to play in assisting Coral Triangle countries and people to adapt to the changes in their climate.“

The Australian government this week announced a 2020 target for reducing its greenhouse gas pollution by 5 per cent, which WWF criticised as completely inadequate. Reductions of at least 25 per cent by 2020 are needed to set the world on a pathway to meaningful cuts in greenhouse pollution.

Australia’s Coral Sea, which will also be affected by coral bleaching and climate change, is a pristine marine wilderness covering almost 1,000,000 square kilometres and is extraordinarily rich in marine life, including sharks and turtles, with a series of spectacular reefs rising thousands of metres from the sea floor.

WWF is urging the Australian government to declare the Coral Sea a marine protected area, as well as working to establish a network of marine protected areas that will assist ocean environments to adapt to the changes caused by rising temperatures, and to absorb the impacts from human activity.

SOURCE : World Wildlife Fund

Structure Of New Botulism Nerve Toxin Subtype Revealed

2009-01-03T11:45:00.006+07:00

Computer-generated “ribbon” representations of the molecular structure of botulinum neruotoxin subtypes E (left) and B (right). The accompanying schematics show that in subtype E, both the binding domain (yellow) and the catalytic domain (red — which cleaves cellular proteins to block the release of neurotransmitters) lie on one side of the translocation domain (green). On subtype B, the binding and catalytic domains flank the central translocation domain. This structural difference may explain why subtype E is a faster-acting toxin. (Credit: Image courtesy of DOE/Brookhaven National Laboratory)

Scientists at the U.S. Department of Energy’s (DOE) Brookhaven National Laboratory have determined the atomic-level structure of a third subtype of botulinum neurotoxin — a deadly toxin produced by certain bacteria that causes the disease botulism, and is also used in cosmetic and therapeutic applications such as reducing wrinkles and calming a hyperactive bladder.

The detailed structure, published online December 22, 2008, by the Journal of Molecular Biology, reveals a unique arrangement of the active components that may help explain why botulinum neruotoxin subtype E (one of seven distinct subtypes) is faster-acting than other subtypes previously studied at Brookhaven Lab — and may have implications for improving vaccines and/or therapeutic agents.

“Understanding the differences among the seven botulinum neurotoxin subtypes is particularly imperative at a time of heightened concern about the potential use of these toxins as bioterror weapons,” said Brookhaven biologist and lead author Subramanyam Swaminathan, who has conducted extensive research on botulinum neurotoxins supported by DOE, the U.S. Army, and the National Institutes of Health. Although experimental vaccines administered prior to exposure can inhibit the neurotoxin’s destructive action, no effective pharmacological treatment exists.

All seven neurotoxin subtypes cause their deadly effects using a common mechanism, with each step being activated by a different portion, or domain, of the toxin protein. First the neurotoxin binds to a nerve cell; then it moves into the cell; and then it cleaves specific proteins that block the release of neurotransmitters, the chemicals nerve cells use to communicate with one another and with muscles. Without that communication, muscles, including those used to breathe, become paralyzed.

“Blocking any of these steps could thwart the toxins’ deadly action,” Swaminathan said. “But to do that, we need to understand the details of the proteins’ structures.”

Swaminathan and his team had previously analyzed the molecular-level structures of various fragments of botulinum neurotoxin subtypes A to F, and that of the whole neurotoxin B, using x-ray crystallography at the National Synchrotron Light Source (NSLS) at Brookhaven Lab. In this technique, scientists beam high-intensity x-rays at a crystalline sample of the protein and measure how the x-rays scatter off the sample to locate the positions of individual atoms.

These studies revealed that in subtypes A and B, the three domains were arranged in the same way: with the binding and protein-cleaving domains “flanking” a longer central region known as the translocation domain, essential for moving the toxin into the cell.

“Because the genes that code for these proteins have a large degree of similarity and all the subtypes incapacitate nerve cells in a very similar way, many biologists had assumed that all seven botulinum neurotoxins would have a similar structural arrangement,” Swaminathan said.
The current study of botulinum subtype E, also conducted at the NSLS, disproved that assumption, taking the scientists by surprise. Instead of the flanking arrangement, the binding and protein-cleaving domains of subtype E are both on the same side of the translocation domain. In addition, while all other subtypes are made of two protein chains, subtype E is a single-chain molecule.

“This arrangement may have an effect on translocation, with the molecule strategically positioned for quick entry into the cell,” Swaminathan said. Though he emphasizes that further confirming research is essential, this could be a plausible explanation for why botulism caused by subtype E sets in faster than that caused by other subtypes.

This finding may help scientists develop faster-acting vaccines and therapeutic agents.
For example, in the treatment of hyperactive bladder disorders, botulinum neurotoxin subtype A is currently used to inhibit neurotransmitter release and control bladder muscles. But it can take days or a week for the drug to be effective. A faster-acting neurotoxin might improve the response.

Additionally, patients sometimes develop resistance to botulinum treatments, developing antibodies that break down the toxin. So having an additional subtype for therapeutic use could be of benefit in situations where treatments must be repeated.

Finally, considering the threat of botulinum neurotoxin being used as a bioterror weapon, Swaminathan said, “The finding of a significant variation in the structural arrangement of subtype E also makes it clear that we must study the structures of the four remaining subtypes to gain a better understanding of their individual characteristics so that appropriate countermeasures can be developed for all seven forms.”

This study was funded by grants from the Defense Threat Reduction Agency/Joint Science and Technology Office for Chemical and Biological Defense. Data for this study were measured at beamline X25 of the NSLS, which is supported by the Offices of Biological and Environmental Research and of Basic Energy Sciences of DOE’s Office of Science, and from the National Center for Research Resources of the National Institutes of Health.

SOURCE : DOE/Brookhaven National Laboratory

Grape-seed Extract Kills Laboratory Leukemia Cells, Proving Value Of Natural Compounds

2009-01-03T01:51:00.001+07:00

An extract from grape seeds forces laboratory leukemia cells to commit cell suicide, according to researchers from the University of Kentucky. They found that within 24 hours, 76 percent of leukemia cells had died after being exposed to the extract.
The investigators, who report their findings in the January 1, 2009, issue of Clinical Cancer Research, a journal of the American Association for Cancer Research, also teased apart the cell signaling pathway associated with use of grape seed extract that led to cell death, or apoptosis. They found that the extract activates JNK, a protein that regulates the apoptotic pathway.

While grape seed extract has shown activity in a number of laboratory cancer cell lines, including skin, breast, colon, lung, stomach and prostate cancers, no one had tested the extract in hematological cancers nor had the precise mechanism for activity been revealed.

"These results could have implications for the incorporation of agents such as grape seed extract into prevention or treatment of hematological malignancies and possibly other cancers," said the study's lead author, Xianglin Shi, Ph.D., professor in the Graduate Center for Toxicology at the University of Kentucky.

"What everyone seeks is an agent that has an effect on cancer cells but leaves normal cells alone, and this shows that grape seed extract fits into this category," he said.

Shi adds, however, that the research is not far enough along to suggest that people should eat grapes, grape seeds, or grape skin in excess to stave off cancer. "This is very promising research, but it is too early to say this is chemo-protective."

Hematological cancers – leukemia, lymphoma and myeloma – accounted for an estimated 118,310 new cancer cases and almost 54,000 deaths in 2006, ranking these cancers as the fourth leading cause of cancer incidence and death in the U.S.

Given that epidemiological evidence shows that eating vegetables and fruits helps prevent cancer development, Shi and his colleagues have been studying chemicals known as proanthocyanidins in fruits that contribute to this effect. Shi has found that apple peel extract contains these flavonoids, which have antioxidant activity, and which cause apoptosis in several cancer cell lines but not in normal cells. Based on those studies, and findings from other researchers that grape seed extract reduces breast tumors in rats and skin tumors in mice, they looked at the effect of the compound in leukemia cells.

Using a commercially available grape seed extract, Shi exposed leukemia cells to the extract in different doses and found the marked effect in causing apoptosis in these cells at one of the higher doses.

They also discovered that the extract does not affect normal cells, although they don't know why.

The researchers then used pharmacologic and genetic approaches to determine how the extract induced apoptosis. They found that the extract strongly activated the JNK pathway, which then led to up-regulation of Cip/p21, which controls the cell cycle.

They checked this finding by using an agent that inhibited JNK, and found that the extract was ineffective. Using a genetic approach – silencing the JNK gene – also disarmed grape seed extract's lethal attack in leukemia cells.

"This is a natural compound that appears to have relatively important properties," Shi said.

SOURCE : American Association for Cancer Research

Four Years After Tsunami, Coral Reefs Recovering

2009-01-03T01:31:00.005+07:00

A team of scientists from the New York-based Wildlife Conservation Society (WCS) has reported a rapid recovery of coral reefs in areas of Indonesia, following the tsunami that devastated coastal regions throughout the Indian Ocean on December 26, 2004.

The WCS team, working in conjunction with the Australian Research Council Centre of Excellence for Coral Reef Studies (ARCCoERS) along with government, community and non-government partners, has documented high densities of “baby corals” in areas that were severely impacted by the tsunami.

The team, which has surveyed the region’s coral reefs since the December 26, 2004 tsunami, looked at 60 sites along 800 kilometers (497 miles) of coastline in Aceh, Indonesia. The researchers attribute the recovery to natural colonization by resilient coral species, along with the reduction of destructive fishing practices by local communities.

“On the 4th anniversary of the tsunami, this is a great story of ecosystem resilience and recovery,” said Dr, Stuart Campbell, coordinator of the Wildlife Conservation Society’s Indonesia Marine Program. “Our scientific monitoring is showing rapid growth of young corals in areas where the tsunami caused damage, and also the return of new generations of corals in areas previously damaged by destructive fishing. These findings provide new insights into coral recovery processes that can help us manage coral reefs in the face of climate change.”

While initial surveys immediately following the tsunami showed patchy (albeit devastating) damage to coral reefs in the region, surveys in 2005 indicated that many of the dead reefs in the study area had actually succumbed long ago to destructive fishing practices such as the use of dynamite and cyanide to catch fish. It is also possible that the crown of thorns starfish—a marine predator—had caused widespread coral mortality.

Since then, some communities have moved away from destructive fishing and have even begun transplanting corals to recover damaged areas.

For example, Dodent Mahyiddin, a dive operator on Weh Island, leads an effort to transplant corals onto hand-laid underwater structures to restore a badly damaged reef in front of the remains of his dive shop, which was also destroyed by the tsunami. Already he is seeing widespread colonization of young corals.

On a larger scale, the WCS team is working to establish community-based coral reef protected areas based on customary marine laws that were first established in the 1600’s and maintained throughout Dutch colonial rule. The laws empower local communities to manage their own local marine resources rather than adhere to nationalized protected areas.

Healthy coral reefs are economic engines for Acehnese communities, according to WCS, supplying commercially valuable food fish as well as tourism dollars from recreational diving.

“The recovery, which is in part due to improved management and the direct assistance of local people, gives enormous hope that coral reefs in this remote region can return to their previous condition and provide local communities with the resources they need to prosper,” said Dr. Campbell. “The recovery process will be enhanced by management that encourages sustainable uses of these ecosystems and the protection of critical habitats and species to help this process.”

The study area is adjacent to the “Coral Triangle,” a massive region containing 75 percent of the world’s coral species shared by Indonesia, Malaysia, Papua New Guinea, Philippines, Solomon Islands, and Timor-Leste.

SOURCE : Wildlife Conservation Society.

In Promiscuous Antelopes, The 'Battle Of The Sexes' Gets Flipped

2008-08-20T20:21:00.000+07:00

In some promiscuous species, sexual conflict runs in reverse, reveals a new study. Among African topi antelopes, females are the ones who aggressively pursue their mates, while males play hard to get.

The classical view of sexual conflict holds that males, for whom reproducing is cheap, will mate as much as possible. On the other hand, females, who must pay a heftier price, are choosier about their mating partners.

Mother nursing baby topi antelope in Serengeti National Park in Tanzania,
East Africa. (Credit: iStockphoto/Bruce Block)

"When biologists talk about the 'Battle of the Sexes,' they often tacitly assume that the battle is between persistent males who always want to mate and females who don't," said Jakob Bro-Jørgensen of University of Jyväskylä in Finland. "However, in topi antelopes, where females are known to prefer to mate with males in the center of mating arenas, we've found a reversal of these stereotypic sex roles."

Such role reversals may occur in species where females benefit from mating multiply, either because it increases their chances of conception with high-quality males or simply because it increases the probability that they conceive at all, Bro-Jørgensen added. He noted that this reversed sexual conflict might not be a rarity in the animal kingdom, as topi are "in many ways a very typical mammalian species characterized by male mate competition and female choice."

In promiscuous species--those in which individuals mate with multiple partners within a short time period--Bro-Jørgensen's group suspected that females might sometimes have higher optimum mating rates than their mating partners. Topi antelope offered an ideal opportunity for studying the dynamics of sex roles in promiscuous mammals, Bro-Jørgensen said, because over a month and a half, individual females become receptive to mating for roughly one day, when they mate several times with each of about four males on average. Females prefer to mate with those males who have succeeded in acquiring territories in the center of "mating arenas," known as leks. But the majority of females also mate with other males as well, resulting in intense sperm competition.

Indeed, they have now shown that aggressive female topis compete with one another for a limited supply of sperm from the most desirable members of the opposite sex, even attacking their fellow mating pairs. Meanwhile, resistant males grow choosier about their mating partners, deliberately selecting the least mated females and launching counterattacks against aggressive females with whom they've already mated.

The bottom-line of the findings, according to Bro-Jørgensen: "We should not regard coyness as the only natural female sex role just as we should not expect that it is always the natural male sex role to mindlessly accept any mating partner," he said. "Nature favors a broader range of sex roles."

This research was published online on November 29th in Current Biology.

The researcher is Jakob Bro-Jørgensen, of the Department of Biological University of Jyva¨ skyla, Jyva¨ skyla¨, Finland; and the Institute of Zoology, Zoological Society, Regent's Park, London, UK.

SOURCE : Cell Press

Protein Translation In Sperm

2008-08-20T11:19:00.001+07:00

A new paper in the February 15th issue of Genes & Development lends novel insight into the cellular changes that occur in sperm while they reside in the female reproductive tract -- providing a new understanding of the molecular genetics of successful fertilization.

It had been believed for decades that spermatozoa are translationally silent. However, Dr. Yael Gur and Haim Breitbart (Bar-Ilan University, Israel) now show that, in fact, protein translation does take place in mammalian sperm prior to fertilization.

Their paper has been released online ahead of print at www.genesdev.org.

After ejaculation, sperm reside in the female reproductive tract for several hours. During this time, a number of biochemical changes take place within sperm, collectively known as "capacitation," that render the sperm competent to penetrate and fertilize the female oocyte.

In their new report, Drs. Gur and Breitbart demonstrate that human, rat, bovine and mouse sperm all incorporate labeled amino acids into polypeptides during the capacitation phase. They identify that mitochondrial translation machinery (as opposed to cytoplasmic) directs translation of nuclear-encoded genes in sperm, and that its inhibition leads to a marked decrease in sperm motility, actin polymerization, the acrosome reaction and in vitro fertilization rates.

Thus, protein translation in sperm is essential for sperm functions that directly contribute to fertilization. Dr. Breitbart is confident that "The new findings would give us better understanding for treatment of male infertility and developing new male or female contraceptives."

SOURCE : Cold Spring Harbor Laboratory

Male Deer Are Born To Live Fast, Die Young

2008-08-19T20:51:00.002+07:00

In the September issue of The American Naturalist, Juan Carranza (Biology and Ethology Unit, University of Extremadura, Spain) and Javier Pérez-Barbería (Macaulay Institute, United Kingdom) offer a new explanation for why males of ungulate species subjected to intense competition are born with lower survival expectancies than females.

The research reveals that male ungulates have smaller molars relative to their body size -- and hence less durable teeth that will wear out sooner, which might contribute to their shorter lives compared with females.

Natural selection favors reproduction rather than survival; the cost of reproduction compromises survival. Males of species subjected to intense male-male competition for access to females are known to have shorter life expectancies than females. Earlier aging in males might be related to higher reproductive costs, especially when lifetime reproductive success in males takes place within the few years when they can win contests and maintain their dominance.

By comparing body and dental size of males and females of 123 species of ungulates, the authors offer another compelling explanation for why male ungulates lead shorter lives. They estimated the pattern of change of these traits along the evolutionary development of the group and found that for species where a single male has many females and where the males and females are different sizes, the rate of increase of dental size was lower than that of body size.

As a result, smaller teeth (in comparison to body size) are produced in males. It is possible that natural selection did not produce larger, more durable teeth because there was no reproductive return from it, since males in these species do not generally increase their success by living longer after prime age.

"These findings," the authors state, "provide us with interesting insights into how natural and sexual selection design our bodies and their longevity."

Reference: Juan Carranza and F. Javier Pérez-Barbería, "Sexual selection and senescence: male size-dimorphic ungulates evolved relatively smaller molars than females", The American Naturalist (2007) volume 170:370--380. DOI: 10.1086/519852

SOURCE : University of Chicago Press Journals

The Cost Of Keeping Eggs Fresh For Mother Cockroaches

2008-08-19T18:54:00.002+07:00

Tiny multiple sperm can be long lived, while large "expensive" eggs degenerate quickly if they are not fertilized. This conundrum -- there should be selection for females to keep their eggs fresh until they are used -- has recently been studied in a cockroach where some choosy females have genes that allow them to maintain eggs while looking for the best mate. Perhaps, however, these genes are limited because they are harmful in some environments.

One of the defining differences between the sexes is in the size of their gametes. Males make many tiny sperm while females make only a few large eggs. This suggests that sperm are cheap while eggs are expensive. Yet sperm can be very long lived, while eggs degenerate quickly after they are made if they are not fertilized.

Why don't females take better care of their expensive eggs? After all, if the females don't use their eggs they have fewer offspring, whereas males make more sperm then they will use anyway. This evolutionary conundrum -- there should be selection for females to keep their eggs fresh until they are used -- has recently been studied by Dr. Trish Moore and her colleagues at the Cornwall Campus of the University of Exeter, with support from NERC, and is published in the March issue of The American Naturalist.

Moore and colleagues examined why females don't keep their eggs fresh in a cockroach where females mate only once during a reproductive cycle, give live birth, and therefore are choosy about the male with which they will mate. Females can't be too choosy, however. If they wait too long to mate they lose good quality oocytes through programmed cell death. But Moore's team finds that some females have genes that would allow them to maintain eggs even if they delay mating. So why aren't all females delaying cell death and holding onto their eggs? Moore speculates that perhaps these genes play a dual role and while they may be beneficial under one environment, when females don't mate, they might be harmful under another, such as when food is limiting. "When females are starving, hanging on to yolky eggs full of nutrients is bad.

Instead a female could recycle those nutrients into her survival. So females face a decision between keeping eggs fresh for producing offspring now, or using those nutrients herself and taking the chance she can reproduce later." The group is currently investigating this trade-off arising from a conflict over food or sex. Although this is a new twist in the conflict over food or sex, the result is a familiar one in evolutionary biology; it is hard to be best at everything.

SOURCE : University of Chicago Press Journals

Male Chimpanzees Prefer Mating With Old Females

2008-08-18T20:40:00.003+07:00

Researchers studying chimpanzee mating preferences have found that although male chimpanzees prefer some females over others, they prefer older, not younger, females as mates.

Imoso, the highest-ranking male in the Kanyawara community of Kibale National Park,
Uganda, grooms Outamba, a middle-aged female. Male chimpanzees at Kanyawara consistently prefer the oldest females in their community as mating partners, suggesting that the preference that human men exhibit for youthful women is a recent evolutionary phenomenon. For more information, see the Report by Muller et al. in the November 21 Current Biology. (Credit: Photograph by Jean-Michel Krief)

The findings uncover a stark contrast between chimpanzee behavior and that of humans, their primate cousins. The basis for this difference may lie in the fact that whereas chimpanzees participate in a relatively promiscuous mating system, humans form unusually long-term mating bonds, thereby making young females more valuable as mates with greater reproductive potential. The findings, reported by Martin Muller of Boston University and colleagues at Harvard University, appear in the November 21st issue of Current Biology.

Theoretical explanations for the preference of human males for young females as mates include the facts that humans tend to form long-term mating partnerships, and that female fertility is limited by menopause and, therefore, age. The converse of such an explanation suggests that species that appear to lack long-term pair bonding and menopause (such as chimpanzees) should not exhibit such strong preferences by males for young females.

In the new work, researchers examined this idea by studying male mate preferences within the Kanyawara chimpanzee community in Kibale National Park in Uganda. The researchers found that, in contrast to humans, male chimpanzees prefer older females to younger ones. They found that, compared to younger females, older females were more likely to be approached for copulation, were more often in association with males during estrous periods, copulated more frequently with high-ranking males, and gave rise to higher rates of male-on-male aggression in mating contests.

The findings, in addition to supporting the idea that long-term pair bonding and menopause may contribute to the preference of human males for young females, also suggest that this characteristic may be an evolutionarily derived trait that arose in the human lineage sometime after the lineages giving rise to humans and chimpanzees diverged.

The researchers include Martin N. Muller of Boston University in Boston, MA; Melissa Emery Thompson and Richard W. Wrangham of Harvard University in Cambridge, MA. The research at Kibale was supported by grants from the United States National Science Foundation (grant no. 0416125), the L.S.B. Leakey Foundation, the National Geographic Society, and the Wenner-Gren Foundation.

Muller et al.: "Male Chimpanzees Prefer Mating with Old Females." Publishing in Current Biology 16, 2234--2238, November 21, 2006 DOI 10.1016/j.cub.2006.09.042.

SOURCE : Current Biology

Mouse Ovaries And Testes Age In Unique Ways

2008-08-18T08:47:00.002+07:00

Aging leads to large changes in gene activity in the ovaries of mice, but only limited changes in testes, according to new research. A lifespan-extending calorie-restricted diet reversed some of the aging effects -- but, unlike the widespread changes observed in somatic organs, it had an impact only in a small number of gonad-specific genes.

As well as tackling one of the key questions of ageing -- by exploring if reproductive organs age in the same way as other body organs -- this research is important in the light of the trend for some women in developed countries to put off childbearing until later in life.

A research team led by Minoru Ko, MD, PhD, from the National Institute on Aging, Baltimore, USA used whole-genome DNA microarrays to study the effects of age, sex and diet on the global gene expression in mouse ovaries and testes. They found that reproductive organs age in a different way to other body tissues and, furthermore, that ovaries age in a different way from testes.

Age-related changes in gene expression occurred in gonads -- as they are known to in other body tissues -- but these changes tended to be in different classes of genes. Only two of the six categories of genes previously associated with aging in muscle, kidney and brain were associated with aging in the ovary; none were associated with aging in the testis. The changes seen in ovaries could be influenced by changes in the tissue composition of ovaries as females age and ovulation ceases.

The researchers also found that calorie restriction in females reduced the expression of genes involved in metabolism and follicle growth, which seems to be consistent with a popular view that the calorie restriction causes a shift in energy use away from reproduction towards general body maintenance and repair. However, male mice on the same diet did not appear to sacrifice reproductive function, suggesting an evolutionary difference between males and females when coping with a food shortage.

SOURCE : BioMed Central

Alarm Pheromone Causes Aphids To Sprout Wings

2008-08-17T19:14:00.000+07:00

Chemical communication within insect species is often much more sophisticated than expected. When aphids are attacked by predators such as ladybird beetles, they release an alarm pheromone, (E)-β-farnesene, that has long been known to cause other aphids to walk around or drop from the plant.

In a paper soon to appear in Ecology Letters, researchers at the University and Max-Planck-Institute in Jena, Germany, now show that exposure to alarm pheromone also causes pea aphids to produce winged offspring that leave their host plant when mature. Because some plants can also release (E)-β-farnesene, they could in theory manipulate aphids into flying away.

However, aphids were shown to react mainly to the frequency of pheromone release and not the actual quantity present, possibly to avoid manipulation by plants. Thus, to reduce damage caused by aphids, the major insect pests in Europe, it may prove effective to apply pulses of alarm pheromone to infested fields.

SOURCE : Blackwell Publishing Ltd.

Men And Women May Need Different Diets

2008-08-17T09:34:00.003+07:00

Diet can strongly influence how long you live and your reproductive success, but now scientists have discovered that what works for males can be very different for females.

In the first study of its kind, the researchers have shown that gender plays a major role in determining which diet is better suited to promoting longer life or better reproductive success.

In the evolutionary "battle of the sexes", traits that benefit males are costly when expressed in females and vice versa. This conflict may have implications for human diet, aging and reproduction, says a team of scientists from UNSW, the University of Sydney and Massey University.

"When it comes to choosing the right diet, we need to look more closely to the individual, their sex and their reproductive stage in life," says Associate Professor Rob Brooks, Director of the Evolution and Ecology Research Centre at the University of New South Wales. "It may be, for example, that women in their child-bearing years need a different diet to those who are post-menopausal.

"It also underlines the important lesson that what we want to eat or, if you like, what we're programmed to eat, is not necessarily best for us." The researchers are conducting long-term studies on Australian black field crickets and have discovered that the lifespan of both males and females is maximised on high-carbohydrate, low-protein diets, they say in the latest issue of Current Biology.

But reproductive success differs dramatically between the sexes when the carbohydrate-protein balance is changed: males live longest and have the greatest reproductive success with a diet that favours carbohydrates to protein by eight-to-one, whereas females have greatest success when the ratio is just one-to-one. Given a choice, however, females eat only a small amount more protein than males. The shared ability to sense and choose food dooms both males and females to eat a diet that is a compromise between what is best for each sex.

"Male and female crickets maximise their fitness on different diets," says UNSW's Dr Alexei Maklakov, the study's lead author. "Despite that, the dietary preferences of the sexes are very similar. Instead of selecting foods in a sex-specific manner, males and females select 'intermediate' diets that are less than optimal for both sexes.

The researchers believe the sexes share most of their genes and this fact can constrain the evolution of sex differences in traits such as diet choice, because many of the same genes are likely to be responsible for trait expression in both sexes.

Significance for humans -- "Men and women invest differently in reproduction, a difference that is even more marked than that between male and female crickets," says Rob Brooks. "Think of the tremendous amounts of energy and protein required of a mother in carrying a baby to term and breastfeeding. We also know that men and women need to eat different diets - think of the careful attention we pay to what expectant mothers eat.

"What men and women need to eat might be more dramatically different than we had realised. However, men and women eat very similar diets and our results suggest that our tastes and food preferences could be a shared compromise, as they are in crickets."

SOURCE : University of New South Wales

Rodent Sperm Work Together For Better Results

2008-08-17T09:00:00.002+07:00

Individual sperm in promiscuous rodents have learned to work together in order to compete against sperm of rival males, according to new research carried out at the University of Sheffield

Although, sperm are inseminated in millions each sperm goes it alone. However, under some circumstances it might be advantageous for sperm to cooperate with one another. This is especially likely to be the case when females are promiscuous and sperm of one male have to compete against those of rival males. New research by Dr Simone Immler and colleagues from the University's Department of Animal and Plant Sciences shows that in promiscuous rat and mice, where competition is high, individual sperm cooperate with one another in order to out-compete sperm of rival males.

The research shows that this cooperation is possible only because of to the highly specialised design of rat and mouse sperm. Promiscuous species have a particularly well developed 'hook shaped' sperm head which helps individual sperm to hook up to each other and form a 'group'. These groups of sperm contain five to 100 sperm and they swim faster and stronger than individual sperm which makes them better competitors in the race for the fertilisation of the egg.

Dr Simone Immler said: "It was previously believed that sperm not only competed against rival males but that they also competed against each other in order to fertilise the female egg. However, this research shows that when the pressure from rival males is high, individual sperm will cooperate with one another to ensure that at least one of their siblings successfully reaches the female egg."

The results will be published on Wednesday 24th January in the freely available, open-access journal -- online at http://www.plosone.org.

Citation: Immler S, Moore HDM, Breed WG, Birkhead TR (2007) By Hook or by Crook? Morphometry, Competition and Cooperation in Rodent Sperm. PLoS ONE 2(1): e170. doi:10.1371/journal.pone.0000170 (http://dx.doi.org/10.1371/journal.pone.0000170)

SOURCE : Public Library of Science

A Little Bit Of Egg Makes Tracking Aphids Easier

2008-08-16T19:14:00.000+07:00

The green peach aphid, despite its name, is a pest of potatoes. Besides siphoning off juices from potato plants, the aphid can infect the plants with viruses that cause an estimated $100 million annually in yield losses.

An alate (winged) green peach aphid, Myzus persicae. (Credit: Photo by Scott Bauer)

Now, tracking where and when the aphid is likely to transmit potato viruses could be easier to do, thanks to a new marker technique devised by Agricultural Research Service (ARS) entomologist Tom Unruh. His approach--which uses egg whites, plastic-mesh screens and an antibody-based test--is still experimental. But, ultimately, information derived from its use could help potato growers improve the timing of insecticide application to deter virus-laden aphids from feeding on plants.

Unruh devised the technique to support studies to determine whether virus-carrying aphids are flying into potato fields from nearby weed patches. Existing methods of capturing and marking the dash-sized pests have been difficult and unreliable, according to Unruh, with the ARS Yakima Agricultural Research Laboratory in Wapato, Wash.

His solution involved mixing egg-white proteins with water to create a solution that can be sprayed onto potato plants or associated weeds like nightshade. Aphids pick up the egg proteins while crawling over treated areas. To track them, Unruh relies on wide-mesh screens secured below a teepee-like scaffold that can be placed in or near potato fields. An adhesive holds the aphids so they can be returned to the laboratory for analysis using an immunological assay, which employs antibodies to detect egg proteins if they're present.

In fields near Wapato, more than 50 percent of green peach aphids that contacted treated potato plants tested positive for egg proteins. More field tests are under way.

SOURCE : US Department of Agriculture

Climate Change And Species Distributions

2008-08-16T15:12:00.000+07:00

Scientists have long pointed to physical changes in the Earth and its atmosphere, such as melting polar ice caps, sea level rise and violent storms, as indicators of global climate change.

But changes in climate can wreak havoc in more subtle ways, such as the loss of habitat for plant and animal species. In a series of talks at the Ecological Society of America (ESA) 93rd Annual Meeting, climate change scientists will discuss how temperature-induced habitat loss can spell disaster for many living things.

Climate models project that rising temperatures over time can lead to an increase in dry, desert-like conditions, which will affect not only the survivorship of particular species, but also the natural resources they have adapted to use in their natural environment. Species are thus forced to move elsewhere to find places to live and food to eat.

"Impacts on individual species indicate wider changes at the biome level that will potentially change conditions for many plant and animal species, in addition to ecosystem services to humans," says Patrick Gonzalez, a researcher at The Nature Conservancy and a member of the Intergovernmental Panel on Climate Change (IPCC).

One species whose habitat may be in danger is the Canada lynx, which is listed as threatened in the United States. The feline's main prey, the snowshoe hare, lives in deep snow cover in boreal forest. Because they rely so heavily on hares for food, lynx are adapted to live in areas with snow cover at least four months out of the year. The cats are so specialized to life on snow that their paws are much wider than is required to support their weight; the large paws help them stalk hares over deep snow without falling in.

Gonzalez, who has worked with USDA Forest Service scientists to analyze lynx habitat, projects that a temperature increase of 2.5 to 4 degrees Celsius in the coming century across the U.S. and Canada—the range of warming under the scenarios reported by the IPCC—may diminish snow cover suitable for lynx by 10 to 20 percent and reduce boreal forest cover by half in the contiguous U.S. Together, these changes could shift lynx habitat northward and decrease the area of habitat in the lower 48 states by two-thirds. This potentially extensive loss of habitat signals serious changes in boreal and alpine ecosystems, says Gonzalez.

Climate change can result in animals and plants migrating northward to escape the heat, but in many cases suitable habitat becomes scarce or unavailable farther away from the species' natural range. The Propertius duskywing butterfly lives throughout the West Coast of the U.S., and during its caterpillar stage is specialized to live on oak trees. Shannon Pelini, a graduate student at the University of Notre Dame, conducted experiments revealing that warmer temperatures increased the survivorship and body size of caterpillars in its most northern habitats. A lack of oak trees in more northern climes, however, would preclude them from moving further north. The range shift of oak trees will happen much slower than the shift for the butterflies, leading to a contracted range, says Pelini.

As if the direct effects of rising temperatures weren't enough, climate change also has impacts that could make climate patterns less consistent over time. Michael Notaro, a scientist at the University of Wisconsin-Madison, used climate data from the past century to model vegetation changes over time. He found that large variability in climate causes an increasing number and intensity of fires and droughts, as well as extreme weather events that could kill long-lived trees and allow short-lived grasses to colonize the leftover space. His models predict that year-to-year variability in precipitation and temperature reduces the Earth's total vegetation cover, expanding its relative grass cover and diminishing its relative tree cover.

"The central U.S. is characterized by an ecotone that's the intersection of forest in the East and grassland in the West," says Notaro. "The border between these ecosystems is largely determined by climate variability and it is likely that climate change will shift the location of this and other ecological boundaries worldwide."

Gonzalez agrees that the research results presented at the ESA Annual Meeting indicate serious vulnerabilities of both individual species and global biomes to climate change.

"Climate change threatens to alter extensive areas of habitat," says Gonzalez. "Lynx is one species that is vulnerable, but the potential impacts of climate change on entire ecosystems are even more alarming."

The researchers will present their results in the following oral sessions:

Shannon Pelini and Patrick Gonzalez - Climate Change: Range and Phenology, Monday, Aug. 4, Midwest Airlines Center
Michael Notaro - Climate Change and Plants I, Tuesday, Aug. 5, Midwest Airlines Center

SOURCE : Ecological Society of America

Prions Show Their Good Side

2008-08-16T08:07:00.000+07:00

Prions, the infamous agents behind mad cow disease and its human variation, Creutzfeldt-Jakob Disease, also have a helpful side. According to new findings from Gerald Zamponi and colleagues, normally functioning prions prevent neurons from working themselves to death.

Diseases such as mad cow result when the prion protein adopts an abnormal conformation. This infectious form creates a template that induces normal copies of the protein to misfold as well. Scientists have long assumed that prions must also have a beneficial side but have been unable to pinpoint any such favorable traits.

In the new work, the authors found that mice lacking the prion protein had overactive brain cells. Their neurons responded longer and more vigorously to electrical or drug-induced stimulation than did neurons that had normal prion protein. This hyperactivity eventually led to the neurons' death. The results might help explain why misfolded prions cause dementia: in the wrong conformation, the prion can no longer protect brain cells from deadly overexcitement.

The findings appear in the May 5th issue of the Journal of Cell Biology.

SOURCE : Rockefeller University

In A Bug-eat-bug World, Researchers Use Unique Chinese Wasp To Battle Soybean Aphids

2008-08-15T19:25:00.000+07:00

The days of soybean aphids feasting on soybean fields may be numbered, thanks to a unique import from China.

University of Minnesota scientists are field testing a beneficial insect, a stingless wasp from China also known as Binodoxys communis, that kills soybean aphids. A successful field test would be a major breakthrough in controlling a damaging crop pest. The U of M received permission from the federal government to conduct this test and is the leading institution in the testing.

Researchers look for mummies, the darker brown objects on the soybean leaf shown above,
to gauge the effectiveness of the beneficial insect in controlling soybean aphids.
The light green spots on the soybean leaf are soybean aphids.
(Credit: David Hansen, Minnesota Agricultural Experiment Station)

The soybean aphid first appeared in Minnesota fields in 2000 and today costs soybean growers an estimated $200 million annually in lost crop yields and spraying costs in Minnesota alone. The national cost is much higher.

"The soybean aphid was imported without any of its natural enemies, the organisms that keeps aphids in check in China," said Dave Ragsdale, U of M entomologist. "Our researchers and Extension experts are working to provide that check and balance system."

Multiple stages of evaluation and testing have been completed at the Insect Quarantine Facility, a joint effort between the Minnesota Department of Agriculture and the Minnesota Agricultural Experiment Station on the U of M's St. Paul Campus. Special security and air filtration systems ensure the insects being evaluated don't venture out on their own. Field testing will take place in a limited number of grower fields and at Research and Outreach Centers.

Binodoxys communis was approved for release based upon four years of laboratory safety testing. It is an especially promising species for control of soybean aphid, because it comes from a region in China that is a good climate match to Minnesota. The stingless wasp specializes in soybean aphid and has been observed apparently controlling it in China.

A cooperative effort between the U of M, the state and soybean growers, like New Richland farmer Larry Muff, have made this experiment possible.

"The soybean check off is committed to supporting research that will mitigate this devastating pest," said Muff, co-chair of the Minnesota Soybean Research and Tech Transfer Committee. "Organic growers will also benefit from this biological control of aphids."

University researchers and Minnesota Department of Agriculture scientists will monitor the ability of Binodoxys communis to kill soybean aphids this summer and continue the attack this fall when soybean aphids move to buckthorn plants and survive the winter to battle soybean aphids in 2008.

The researchers also have a backup plan. Eleven other species and strains of stingless wasps are under evaluation and some of these that have shown promise from both a safety and efficacy standpoint may be field tested in 2008.

SOURCE : University of Minnesota

Selection On Sex Cells Favors A Recombination Gender Gap

2008-08-15T19:01:00.000+07:00

Males and females of the same species can be strikingly different. Peacocks strut around with flashy feathers to attract mates, while peahens blend into their surroundings with more subdued colors. But differences are not always as obvious or easily explainable as in this classic example. Even the amount of genetic reshuffling that goes on during egg and sperm production differs between males and females in most species. An evolutionary reason for this has eluded researchers since the phenomenon was originally discovered in fruitflies, Chinese silk worms, and amphipods almost 100 years ago.

Genetic diversity among organisms is promoted when genetic information is rearranged during meiosis, the cell division process that yields sperm and eggs (generically called gametes). During this genetic reshuffling, chromosome pairs overlap, forming structures called chiasmata (“crosses” in Greek), and physically recombine. This process does not just create diversity, it is also an example of diversity—recombination rates vary across chromosomes, sexes, and species.

An early 20th century hypothesis to explain the sex difference in recombination proposed that recombination is restrained within a pair of unlike sex chromosomes (X and Y, for example) and that the suppression spills over to the rest of the chromosomes. Under this idea, the sex with dissimilar sex chromosomes (XY instead of XX, for example) should be the one with the least amount of recombination in all chromosomes. But that is not always the case. Some hermaphroditic species of flatworms, for example, lack sex chromosomes altogether but still display marked differences in male and female recombination rates. In one salamander genus, more reshuffling unexpectedly occurs in the sex with two different sex chromosomes.

In a new study analyzing an updated dataset of 107 plants and animals, Thomas Lenormand and Julien Dutheil bolster the argument against the recombination suppression hypothesis by showing that in species with sex chromosomes, the sex with two dissimilar sex chromosomes doesn’t necessarily have a reduced recombination rate. Additionally, they found that, as a trait, the sex difference in recombination rate is not a lot more similar between two species in the same genus than between two species in different genera, suggesting that the difference evolves quickly.

An alternative hypothesis suggests that sexual selection might play a role in recombination differences. Reproductive success among males is often highly influenced by selection, so mixing up successful genetic combinations in males could be evolutionarily counterproductive. But in past studies, sexual selection was not related to variation in recombination rates.

Putting a new twist on this hypothesis, Lenormand and Dutheil realized that selection was not necessarily limited to the adult stage and that differences in selection among eggs or sperm might help account for recombination differences between the sexes. The authors reasoned that more opportunity for selection on sperm than egg should correspond to less recombination during sperm than egg production (and vice versa), consistent with the idea that genetic combinations surviving selection should remain more intact in the sex experiencing the strongest selection at the gametic stage.

Though male gametes might be expected to be under stronger selection in many species, in true pines it seems to be the female gametes. The ovules compete with each other for resources over an entire year before being fertilized, and, indeed, from the dataset analysis, ovule production involves low recombination rates compared with male pollen in this group. In males, the opportunity for pollen competition was indirectly estimated using self-fertilization rates. The authors assumed that pollen grains competing for ovules of a self-fertilizing plant would be genetically similar and therefore experience less selection. Again, in the analysis, low selection correlated with less recombination in female gamete production, as predicted.

Is selection among eggs and sperm the evolutionary force generating sex-based variation in genetic shuffling? By demonstrating that differences may be influenced by gamete selection in plants, this work has added clarity to otherwise contradictory observations.

SOURCE : Public Library Of Science

In Bowerbirds, Young Females Go More For Blue, Less For Strutting

2008-08-15T07:09:00.000+07:00

ARLINGTON, Va.- When looking for sex partners, younger females prefer males who decorate their place with a little extra blue, be it plastic or feathers. They also prefer males who tone down the intensity of their courtship behavior. At least, that's how it looks for satin bowerbirds, according to research findings published this week in the journal Nature.

The study - conducted in New South Wales, Australia, in 1999-2000 - found that not all females find the same traits attractive in mates. As they choose a mate, females make a series of complex decisions related to male courtship behavior and to the colored decorations males collect and place around the bower, a stick structure that protects females during courtship display. Older females focus more on the male's intense courtship display while younger females are attracted by the blue bower decorations.

The research, funded by the National Science Foundation's Animal Behavior Program, was conducted by biologists Gerald Borgia, Seth Coleman and Gail Patricelli of the University of Maryland. NSF is an independent U.S. federal agency that supports fundamental research and education across all fields of science and engineering.

According to Borgia, learning more about such sophisticated courtship behavior can increase our understanding of mate choice, a fundamental process that affects the genetics of most animal species. Thus, clues to courtship can also aid wildlife conservation and species propagation.

"It's very important," he said, "because it helps us develop a general model of mate choice. We show experimentally that females in a population may choose males for different reasons. This, in turn, explains why males have complex displays - that is to accommodate the different mating preferences of females they engage in courtship."

A male bowerbird's intense performance of "Pick me! Pick me!" involves loud buzzing calls, raising its feathers on end, and running vigorously back and forth, with its wings extended, across its platform stage - the bower. Males build their bowers primarily from sticks, creating a U-shaped chute that they adorn with blue decorations, such as feathers, blue clothespins, and scraps of plastic.

To see if bluer-is-better interior decorating affects females' preferences, the researchers supplemented some bowers with blue plastic tiles and strands. Because male bowerbirds commonly steal from each other, researchers anchored these extra accoutrements with screws and glue.

According to Jane Brockmann of NSF's animal behavior program, "This is an excellent system for studying mate choice. Dr. Borgia watches the bowers by using video cameras that are tripped when a female enters a male's bower, so he has a very accurate record of whether a female just visits a male or mates with him. He has also been studying the same large group of marked birds for years, so he knows when a female's choice changes with age and experience."

Very few studies have this sort of long-term data, and most studies of mate choice treat females as if their decisions do not vary or change, said Brockmann.

"Males of most species show a lot of variation in their behavior," she said. "It is unreasonable to think that females would not similarly show variation. Yet we know very little about variation in how females choose mates. It does matter."

Particularly to males.

Michael Greenfield, who co-directs NSF's animal behavior program with Brockmann, said, "As males are under some pressure to be attractive to and mate with as many females as possible, their display is a means of covering all possibilities in luring potential mates. We still don't really know why female preference varies with age, but one possibility inherent in this study is that learning - which is generally disregarded in studies of sexual selection - plays a role."

As scientists learn more about how females choose mates, biologists will be better able to test various models of how courtship displays evolve among males, Borgia said.

In a previous study, his group found that female satin bowerbirds will return the next year to attractive mates, but "females which fail to encounter very attractive males typically reject their previous mates and search for more attractive males in the following year."

SOURCE : National Science Foundation

Behavioural Ecologists Elucidated How Peahens Choose Their Mates, And Why

2008-08-14T18:52:00.000+07:00

Since Darwin, the peacock exhibiting an elongated tail composed of ocelli has been considered a prime example of the strength of sexual selection. Professor Marion Petrie's classical studies have shown that females prefer males with a high number of ocelli. However, a remaining question concerning the role played by ocelli is how peahens value their number. New research published today in Ethology describes that females may actually assess ocelli density.

Adeline Loyau, Michel Saint Jalme and Gabriele Sorci of the National Museum of Natural History and the Laboratory of Evolutive Parasitology, Paris, have been studying sexual selection on free-ranging common peafowl to elucidate how females choose their mate. They took pictures of displaying peacocks to count the number of ocelli, and captured them to measure tail length. They also made behavioural observations to value male displaying activity and male mating success.

"Preferred males were those exhibiting the higher number of ocelli in the train, but surprisingly females seemed to prefer males with shorter tails. This was unpredictable because we also found that the longer the train, the more dominant the male," they say. The female preference for both high number of ocelli and shorter tail gave the idea that females may actually prefer the visual perception of a dense cluster of ocelli than a diluted number of ocelli over a large surface. "We calculated the ocelli density and found that it did explain female choice."

In the peacock, the ocelli density of the train can only be assessed by females when males spread their trains during the courtship display. "In this species, the expression of the ornament is modulated by the expression of the behaviour. To be chosen, a peacock has to be beautiful but also has to be able to show how beautiful he is. It is not surprising that female preference is also driven by male behaviour." Indeed, they showed that male success was determined by both his ocelli density and his displaying activity. They investigated this preference further and demonstrated that these two cues provide peahens with information about male health. "In other words, it's beneficial for a female to mate with handsome and sportive mates," they conclude with humour, "because these males are in better health."

SOURCE : Blackwell Publishing Ltd.

Researchers Find Resistance To Soybean Fungus

2008-08-14T14:28:00.001+07:00

The first soybean line with genetic resistance to charcoal rot has been released by Agricultural Research Service scientists in Mississippi.

Charcoal rot, caused by the soilborne fungus Macrophomina phaseolina, is a major yield-limiting disease of the Mid-South and other soybean-producing regions throughout the world.

The new line, DT97-4290, developed by scientists in the ARS Crop Genetics and Production Research Unit at Stoneville, is a potentially valuable source of resistance to charcoal rot for soybean breeders and producers in areas experiencing yield losses due to the disease.

Charcoal rot symptoms usually appear when weather conditions are hot and dry, causing the soybean plant to lose vigor. In more advanced stages, petioles and leaves may turn yellow and wilt, while remaining attached to the plant. No chemical controls currently exist for charcoal rot, and resistance has been hard to identify.

Field studies were conducted at Stoneville to find charcoal rot resistance among 24 selected soybean genotypes. The researchers identified three breeding lines with genetic resistance, according to Bob Paris, the research geneticist who developed the line with Alemu Mengistu, a soybean pathologist.

The new line was selected for its adaptation to the clay soils of the lower Mississippi River valley, and for its field resistance to charcoal rot, soybean mosaic virus and stem canker, and moderate resistance to frogeye leafspot.

Genetic material of this release will be deposited in the National Plant Germplasm System, where it will be available for soybean researchers and breeders.

ARS is the U.S. Department of Agriculture's chief scientific research agency.

SOURCE : USDA / Agricultural Research Service

Nano-sensor For Better Detection Of Mad Cow Disease Agent

2008-08-14T08:03:00.000+07:00

In an advance in food safety, researchers in New York are reporting development of a nano-sized sensor that detects record low levels of the deadly prion proteins that cause Mad Cow Disease and other so-called prion diseases.

Scientists report a new device to detect prion proteins
that cause Mad Cow Disease and other prion diseases.
The finding could lead to a reliable blood test for those illnesses in both animals and humans.
(Credit: Courtesy of USDA-Agricultural Research Service, Photo by Keith Weller)

The sensor, which detects binding of prion proteins by detecting frequency changes of a micromechanical oscillator, could lead to a reliable blood test for prion diseases in both animals and humans, the researchers say.

Prions are infectious proteins that can cause deadly nerve-damaging diseases such as Mad Cow Disease in cattle, scrapie in sheep, and a human form of Mad Cow Disease called variant Creutzfeldt-Jakob Disease. Conventional tests are designed to detect the proteins only upon autopsy and the tests are time-consuming and unreliable.

In the new study, Harold G. Craighead and colleagues describe a high-tech, nano-sized device called a nanomechanical resonator array. The device includes a silicon sensor, which resembles a tiny tuning fork, that changes vibrational resonant frequency when prions bind. Its vibration patterns are then measured by a special detector. In experimental trials, the sensor detected prions at concentrations as low as 2 nanograms per milliliter, the smallest levels measured to date, the researchers say.

The article "Prion Protein Detection Using Nanomechanical Resonator Arrays and Secondary Mass Labeling" is scheduled for the April 1 issue of ACS' Analytical Chemistry.

SOURCE : American Chemical Society

Changing Fashions Govern Mating Success In Lark Buntings, Study Finds

2008-08-13T18:37:00.000+07:00

A study of how female lark buntings choose their mates, published in Science, adds a surprising new twist to the evolutionary theory of sexual selection. Researchers at the University of California, Santa Cruz, discovered that female lark buntings show strong preferences for certain traits in the males, but those preferences change from year to year.

Classic examples of sexual selection involve elaborate ornaments, such as the peacock's tail, that evolve as a result of consistent female preferences, so that males with the most exaggerated traits have the most success mating and produce more offspring than less flamboyant competitors. In the case of lark buntings, however, the flexibility shown by females in choosing their mates dampens the trend toward more elaborate ornamentation and may instead maintain variability in male plumage.

"It's counter to the conventional view of female choice as static," said Bruce Lyon, associate professor of ecology and evolutionary biology at UCSC and coauthor of the paper. "These females are capable of very sophisticated behavior, and they appear to benefit from their flexibility in mate choice by gaining enhanced nesting success."

The study suggests that the male's plumage somehow serves as a signal to the female that he possesses certain traits that will affect the pair's nesting success. Shifting environmental conditions may determine which male traits matter most in any given year, said Alexis Chaine, who worked on the study as a UCSC graduate student and is now a postdoctoral researcher at the Centre National de la Recherche Scientifique (National Center for Scientific Research) in France. Chaine is first author of the paper, which appears in the January 25 issue of Science.

"The traits the female is choosing somehow predict how successful the pair will be in nesting," Chaine said. "One possibility is that certain traits are associated with the male being a good forager, and other traits predict how well he could defend the nest from predators. So, if there are lots of ground squirrels, which are a major nest predator, she wants a good defender, but in a year when grasshopper populations are low, she needs a good provider. These are ideas we still need to test."

With a mostly black body and bright white wing patches, the male lark bunting is a distinctive bird of the Great Plains. Females choose a new mate every year, and parenting duties are shared by both members of the pair. The males are territorial during the breeding season, flying up over their territory and singing as they descend to attract a mate. Once they acquire a mate, however, they no longer defend the territory. The researchers found no correlation between the quality of a male's territory and his success in attracting a mate.

The white wing patches and other male plumage traits serve as signals in aggressive interactions between territorial males, Chaine said, meaning that female mate choice is not the only factor influencing those traits. But the researchers found that the role of those signals in competitive interactions between males was consistent from year to year. The level of aggression didn't vary between years either.

"Male competition can't explain the overall pattern, but it may be an important factor in the evolution of male plumage traits," Chaine said.

The variability of the male plumage was one of the first things Lyon noticed when he began studying lark buntings on the Pawnee National Grasslands in Colorado. (The lark bunting is the state bird of Colorado.) Chaine joined Lyon the following year and began an exhaustive long-term study, gathering data from 1999 to 2003.

"We had to conduct studies every year over several years before we could see what was going on," Lyon said. "We saw two patterns of variation in the correlations between male traits and female mate choice. In some cases, it was either on or off--a trait was important to females one year and not important in other years. We also saw reversals--for example, one year the females preferred males with bigger wing patches, and the next year they preferred smaller wing patches."

Lyon cautioned that additional experiments are needed to provide definitive evidence of female preferences. The study was based on statistical correlations, which provide clear evidence that the traits of mated males differ from those of males without mates. "We suspect it's because females are choosing males with particular traits," Lyon said. "Ideally, we would like to test that with field experiments."

The dynamic sexual selection seen in lark buntings is probably occurring in other species as well, he added. That has implications for theoretical models of how sexual selection influences the evolution of male traits.

"The assumption that sexual selection is static is something we've all taken for granted," Chaine said. "This study might cause some people to rethink their systems and take another look at their data."

This research was supported by grants from the National Geographic Society, National Science Foundation, American Museum of Natural History, Sigma Xi, and the American Ornithologist's Union.

SOURCE : University of California - Santa Cruz

Test To Protect Food Chain From Human Form Of Mad Cow Disease

2008-08-13T13:49:00.000+07:00

Scientists are reporting development of the first test for instantly detecting beef that has been contaminated with tissue from a cow's brain or spinal cord during slaughter — an advance in protecting against possible spread of the human form of Mad Cow Disease.

Jürgen A. Richt and colleagues point out that removal of brain, spinal and other central nervous tissue after slaughter is "one of the highest priority tasks to avoid contamination of the human food chain with bovine spongiform encephalopathy," better known as Mad Cow Disease. "No currently available method enables the real-time detection of possible central nervous system (CNS) tissue contamination on carcasses during slaughter," the report states.

They describe a test based on detection of the fluorescent pigment lipofuscin, a substance that appears in high concentrations in the nervous tissue of cattle. The researchers found that it was a dependable indicator for the presence of brain and spinal tissue in bovine carcasses and meat cuts.

"Small quantities of bovine spinal cord were reliably detected in the presence of raw bovine skeletal muscle, fat and vertebrae. The research lays the foundation for development of a prototype device allowing real-time monitoring of CNS tissue contamination on bovine carcasses and meat cuts," the report says.

It was done with colleagues from the National Animal Disease Center of the USDA-Agricultural Research Service and Iowa State University.

SOURCE : American Chemical Society

Evolution Of Male-female Differences Within A Shared Genome

2008-08-13T11:56:00.000+07:00

One of the major components of the world's biological diversity are the differences between males and females in traits related to mating, including weapons used when competing for mates and display traits used to seduce them. Such gender differences are thought to arise because selection acts differently on each sex. The conflicting interests of males and females in reproduction are thought to be a key source of sex-specific selection on such traits.

The evolution of sexual dimorphism is hampered, however, because the sexes share the majority of their genomes; an adaptive response to selection in one sex may therefore cause nonadaptive changes in the other as a correlated response.

In a recent study, Steve Chenoweth and colleagues Howard Rundle and Mark Blows from the University of Queensland, Australia, tackle the combined issues of genetic control and sex-specific selection in a comprehensive investigation of the evolution of male-female differences in a set of sexual display traits in the Australian fruit fly, Drosophila serrata.

Both male and female Drosophila serrata use a set of pheromonal displays during mating, but differ in the relative concentrations of the individual compounds. Using a series of natural populations collected across a wide latitudinal gradient along the east coast of Australia, the authors show that the amount of sexual dimorphism varies and that these differences among populations are genetic. Using classic quantitative genetic methods, they demonstrate that the relaxation of genetic constraints appears to have occurred largely via genes on the X chromosome.

"There are a number of mechanisms by which genetic constraints can be overcome," says Dr. Steve Chenoweth, "Our results suggest that sex-linkage may be key." By manipulating both natural and sexual selection and observing the evolutionary response in the laboratory, the authors also show that, as expected, sexual selection appears to generate sex-specific optima for these pheromones. Contrary to expectation, however, females and not males responded to sexual selection.

"This suggests that the classic scenario of males as the sole target of sexual selection may be overly simplistic," states Dr. Howard Rundle. "If you want to know why males and females differ, you need to consider all forms of selection on both sexes."

This research was published in the January issue of the American Naturalist.

SOURCE : University of Chicago Press Journals

Aphids Are Sentinels Of Climate Change

2008-08-12T18:44:00.001+07:00

Aphids are emerging as sentinels of climate change, researchers at BBSRC-supported Rothamsted Research have shown. One of the UK's most damaging aphids – the peach-potato aphid (Myzus persicae) – has been found to be flying two weeks earlier for every 1°C rise in mean temperature for January and February combined.

This year, the first aphid was caught on 25 April, which is almost four weeks ahead of the 42-year average.

Dr Richard Harrington of the Rothamsted Insect Survey said: "One of the most noticeable consequences of climate change in the UK is the frequency of mild winters. As a direct result of this, aphids seeking new sources of food are appearing significantly earlier in the year and in significantly higher numbers. We have been studying the seasonal biology of aphids for a long time now and we know that populations can continue to grow over the winter and spring provided that conditions are warm enough. After a warm winter, there are much larger numbers flying and they are hence detected much earlier. This means that there are more aphids flying in spring and early summer, when crops are particularly vulnerable to damage."

Scientists at Rothamsted Research have been monitoring the flying form of all aphid species for 42 years. They use a network of 16 suction traps (12 in England and 4 in Scotland), placed at various sites, to collect a representative sample of all flying insects. The long term data on aphids can be used to understand the wider implications of climate change, and also to prepare for the season ahead by determining the need for and timing of aphid control measures (based on preceding winter temperatures).

As well as being important indicators of a changing climate, aphids can cause devastating damage to crops. They extract large amounts of sap, weakening the plant, and also spread plant viruses. In addition, because the sap is very high in sugars the aphids excrete very sticky honeydew, which can encourage the growth of sooty moulds that build up and prevent sunlight from reaching the leaves, causing further weakening.

Professor Nigel Brown, Director of Science and Technology, BBSRC said: "Environmental change is one of the big challenges facing the world today. These long-term data on the seasonal appearance of flying aphids not only show that there are already noticeable changes in the UK climate, but they also provide the knowledge which will help to mitigate the consequences."

This work is reported in BBSRC Business, the quarterly research highlights magazine of BBSRC (the Biotechnology and Biological Sciences Research Council).

SOURCE : Biotechnology and Biological Sciences Research Council

Are Pronghorns Smarter Than Classical European Royalty?

2008-08-12T18:08:00.000+07:00

Over the past two decades, John Byers has proven that female pronghorns are smarter than many humans when it comes to mate selection. Rather than going for the male with the biggest body or most impressive horns, female pronghorns expend a ton of energy searching for the most vigor and best stamina; traits that will give their offspring the greatest chance of success.

An American pronghorn male chases an intruder away from his territory.

Pronghorns are commonly accepted as the second fastest land animal

in the world--behind only the cheetah--reaching speeds in excess of 45 miles per hour.

(Credit: John Byers, Department of Biological Sciences, University of Idaho)

But are they smarter than classical European royalty? When pronghorns select a mate, can they factor in what many historians believe doomed the famous Hapsburg dynasty – inbreeding?

Thanks in part to a four-year, $600,000 grant from the National Science Foundation, Byers will be able to answer that exact question.

“We’ve shown the pronghorns know the benefit of selecting the best males,” said Byers, a professor of biological sciences at the University of Idaho. “Now we’re trying to show whether females can balance the cost benefits of selecting a strong male versus a closely related one. Will they accept mating with a relative if the projected cost of inbreeding is not too high? Or reject the male because the cost is way off the chart? Or will they breed without any regard to genealogy?”

Because Byers has worked with the same pronghorn herds in eastern Montana since the early 1990s, and can identify each pronghorn by sight, he is in a unique position to carry out this study. During that time, he has proven female pronghorns expend 50 percent more energy while searching for the strongest males, and that offspring sired by the chosen few are stronger, have a much higher chance of survival and strike out from their mothers much sooner. Because of this mate testing, nearly all offspring are sired by a small subset of males.

As a result of his research, Byers has a complete pedigree of the entire population. When a fawn is born, genetic testing removes any doubt which male is the father.

When a drought in 2003 killed off most of the males and about 30 percent of the females, Byers knew he was in a unique place to study mate selection based on inbreeding.

“I realized we were going to be in an incredibly interesting position,” he said. “We now know females select males for their vigor with a real benefit in survival for their offspring. But today, about three years after the weather caused a bottleneck in the population, they’re faced with a different set of choices.”

Byers’ research will be two-fold. First, the research team will test the paternity of new fawns, measure their living conditions and monitor their survival rate to see what, if any, negative effects occur in pronghorns from inbreeding. Once that is determined, scientists will study female behavior to see if females avoid closely related males – even the best choices for mates – if the benefits of strong genes are outweighed by the average negative effects of inbreeding.

“I think they’ll be able to discern the best choice,” said Byers. “But only time will tell.”

The results of Byers’ study should help conservationists keep the population of pronghorns – and perhaps many other types of hoofed animals – healthy in the future.

SOURCE : University of Idaho

Red Flour Beetle's 'Selfish' Gene Sequenced

2008-08-12T15:54:00.003+07:00

Tracking the red flour beetle in grain storage facilities could become easier, thanks to research to identify a key gene in this grain-feeding pest.

Determining the genetic code of a key gene could make the red flour beetle (Tribolium castaneum), a major problem.in grain storage facilities, easier to track and may offer new ways to control this pest. (Credit: Photo by Peggy Greb)

Researchers with the Agricultural Research Service (ARS), Purdue University, the Human Genome Sequencing Center at Baylor College of Medicine, Kansas State University, and Exelixis, Inc. in South San Francisco, Calif., have determined the genetic code of the so-called "selfish" gene in the red flour beetle (Tribolium castaneum).

This genetic information may offer a potential tracking tool for facilities where grain is stored. Operators could use the information to determine whether beetles are local or from a distant location--and even to develop a plan to control infestations.

ARS entomologist Richard Beeman and molecular biologist Marcé D. Lorenzen at the agency's Grain Marketing and Production Research Center in Manhattan, Kan., deciphered the genetic code of the "selfish" gene. The research was reported in the Proceedings of the National Academy of Sciences.

The selfish gene is important because red flour beetles that don't inherit it from their mother don't survive. It is called the selfish gene because, whether beneficial or deleterious, it ensures its own perpetuation through the population. These genes are widespread in natural populations of red flour beetles, but are otherwise unknown in the invertebrate world.

According to Beeman, the discovery in red flour beetle may provide a useful vehicle for driving desirable genes into populations, since the gene spreads almost like a disease, and since hitchhiker genes can be attached to it. Malaria researchers think other, similar genes introduced into mosquito populations could reduce the spread of mosquito-borne malaria infections. It may be possible to "attach" another gene to the malaria gene that could negate or minimize its function, thus impeding mosquitoes from spreading the disease.

SOURCE : USDA - Agricultural Research Service

Global Warming's Effects Extend To World's Smallest Butterfly

2008-08-02T17:46:00.000+07:00

The latest issue of Conservation Biology examines the viability of the Sinai baton blue and the results of human population pressures. The study predicts that in the absence of global warming, grazing, and plant collection (three activities directly linked to humans) the world's smallest butterfly would persist for at least 200 years.

The population could withstand small increases in grazing intensity that would decrease their climate, but not increases in temperature. As the level of global warming raises its impact, extinction rapidly accelerates. This implies "... that there may be an annual average temperature, specific to each endangered species, above which extinction becomes much more likely," authors Martin Hoyle and Mike James state. There is no such threshold of grazing pressure.

The authors mapped the entire global range of this butterfly and obtained data on the intensity of livestock grazing. The Sinai baton blue is one of only two endemic animals in St. Katherine's Protectorate, one of Egypt's most recently designated protected areas. Based on the authors' model, the effect of global warming on the chance of extinction does not depend on the future level of habitat destruction due to this grazing; the growing number of families that live on the protectorate keep a small herd of goats and sheep that graze on the plants the butterflies thrive on. Global warming is the deadly culprit.

"If the areas of habitat patches individually fall below certain prescribed levels, the butterfly is likely to go extinct,"the authors conclude.

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This study is published in the August issue of Conservation Biology. Media wishing to receive a PDF of this article please contact journalnews@bos.blackwellpublishing.net

Conservation Biology is a top-ranked journal in the fields of Ecology and Environmental Science and has been called, "required reading for ecologists throughout the world." It is published on behalf of the Society for Conservation Biology.

Martin Hoyle is at the School of Biological and Chemical Sciences at the University of Exeter, Hatherly Laboratories. He has performed research on metapopulation dynamics and has been published in numerous journals.

SOURCE : Blackwell Publishing Ltd.

Amber Specimen Captures Ancient Chemical Battle

2008-08-01T18:57:00.000+07:00

It appears that chemical warfare has been around a lot longer than poison arrows, mustard gas or nerve weapons -- about 100 million years, give or take a little.

A new study by researchers at Oregon State University has identified a soldier beetle, preserved almost perfectly in amber, which was in the process of using chemical repellents to fight off an attacker when an oozing flow of sap preserved the struggle for eternity.

An ancient example of “chemical warfare” about 100 million years old is captured in this sample of amber, in which a soldier beetle is exuding a certain toxin to protect itself from an attacker.
(Credit: Image courtesy of Oregon State University)

The discovery is the earliest fossil record of a chemical defense response, scientists say, and indicates that this type of protective mechanism -- now common in the insect world and among other animal species -- has been around for more than 100 million years. It's a sophisticated form of defense that clearly was in good working order while dinosaurs still roamed the Earth.

"The chance of these circumstances all coming together at the exact right second was pretty slim," said George Poinar, Jr., a courtesy professor of zoology at OSU and one of the world's leading experts on distant life forms preserved in amber. "You have a prehistoric insect being attacked, using its defenses to ward off the predator and the whole event becoming captured in action as sap flowed down a tree. It's quite remarkable."

The beetle was a small insect, about one-quarter inch long, which may have been in the process of becoming lunch for a giant roach or some other larger insect that apparently was 2-3 inches long, judging by the length of an antenna from the other insect also found in the specimen. The other insect either escaped the sap or was preserved in a different piece of amber, in these samples of Burmese amber that came from the Hukawng Valley in Myanmar.

"This particular insect is now extinct, but the broader family of soldier beetles still exists, and they still use this same type of chemical defense mechanism," Poinar said. "That this type of defense has been preserved through 100 million years of evolution is evidence that it works pretty well."

At the time of this event in the Early Cretaceous Period, huge animals such as dinosaurs still dominated the Earth, but scurrying beneath them were early mammals and large numbers of terrestrial invertebrates, such as these insects. Soldier beetles, then as now, were omnivores that lived on things like aphids, other tiny insects or plant pollen. Among other things, this finding pushes back the known existence of this type of beetle by about 60 million years. And at that distant time, they had already evolved ways to defend themselves.

"This beetle was able to exude a sticky chemical substance that was irritating to potential predators, and caused them to go away or leave it alone," Poinar said. "It could even conserve its excretions and control the direction of the defense; in other words, produce the substance only on its left rear side if that was where the attack was coming from."

Building on these types of early defense mechanisms, Poinar said, modern insects now have a wide range of defensive chemical arsenals -- things that are distasteful, nauseating or caustic, from chemicals such as phenols, aldehydes and ketones. Some contemporary soldier beetles can produce types of carboxylic acid, as well as triglycerides and glyceride esters.

In insects, these types of defensive mechanisms are often a key to their survival.

Amber provides a unique mechanism to preserve specimens such as this. Beginning as viscous sap from certain kinds of trees, it can trap small animals or other materials, acts as a natural embalming agent, and eventually can turn into a semi-precious stone that displays these ancient life forms in nearly perfect, three-dimensional form. The phenomena has been invaluable in scientific and other ecological research, allowing experts to help re-create more accurate pictures of ancient ecosystems based on the insect life that lived then.

"Insects give us a fascinating window to the world, and they are survivors," Poinar said. "This particular species lived right on through the K-T Boundary at 65 million years ago, when the dinosaurs and many other species disappeared."

"These insects were here a long time before humans, and we can learn a great deal from their remains," he said. "And they'll probably still be here a long time after our species is gone."

The findings were just published in the Journal of Chemical Ecology.

SOURCE : Oregon State University

Amber Fossils Reveal Ancient France Was A Jungle

2008-07-31T19:18:00.000+07:00

Research on a treasure trove of amber has yielded evidence that France once was covered by a dense tropical rainforest with trees similar to those found in the modern-day Amazon. The 55-million-year-old pieces of amber was discovered in the Oise River area in northern France.

In the new study, Akino Jossang and colleagues used
laboratory instruments to analyze the fossilized tree sap in an effort to link specific samples of amber to specific kinds of trees. The amber remained intact over the ages, while the trees from which it oozed disappeared. Efforts to make such connections have been difficult because amber from different sites tended to have very similar chemical compositions.

The report describes discovery of a new organic compound in amber called "quesnoin," whose precursor exists only in sap produced by a tree currently growing only in Brazil's Amazon rainforest.

Researchers say that amber probably seeped out of a similar tree growing in a tropical forest that covered France millions of years ago before Earth's continents drifted into their current positions.

"The region corresponding to modern France could have been found in a geographically critical marshy zone belonging to Africa and a tropical zone 55 million years ago extending through North Africa to the Amazon," the report states.

The study "Quesnoin, a Novel Pentacyclic ent-Diterpene from 55 Million Year Old Oise Amber" is scheduled for the Jan. 4 issue of ACS' Journal of Organic Chemistry.

SOURCE : American Chemical Society

Gorillas In The Midst Of Extinction

2008-07-31T18:45:00.000+07:00

Satellites provide a bird's eye view of planet Earth, and the space-based vantage can be extremely useful to people interested in viewing out-of-the-way places. Conservationists, for example, must monitor far-flung areas in need of protection. Wars, poverty, remoteness, lack of government involvement, and uncertainty over the best places and ways to focus limited resources can all hinder conservation efforts. Now, NASA satellite imagery is giving scientists and conservationists some of the tools they need to get valuable information on land cover and land use changes in wild areas.

This map shows the location of the Virunga Conservation area within Africa,
and highlights an area in the "Mikeno" sector of the park where rapid deforestation occurred in June 2004. (Credit: Nadine Laporte/ Tiffany Lin)

NASA satellite imagery helps scientists better understand land changes in the Virunga Conservation Area which covers the Virunga National Park in the Democratic Republic of Congo (DRC), the Mgahinga Gorilla National Park in Uganda and the Volcanoes National Park in Rwanda. In Swahili, the word virunga means volcano. The Virunga Conservation Area offers habitat to 380 of the world's 700 remaining mountain gorillas. The other 320 gorillas reside in the nearby Bwindi Impenetrable National Park in Uganda.

In a single week in June of 2004, farmers created pasture for their cattle by clearing 15 square kilometers (5.8 square miles), or 6 percent, of the 264-square kilometers (102 square miles) of mountain gorilla habitat in the southern "Mikeno" sector of Virunga National Park. Because mountain gorilla numbers had increased by close to 56 individuals over the last 10 years, the recent loss of land was a considerable step backward.

In a race against time for the mountain gorillas and many other species indigenous to these natural areas, scientists at the Woods Hole Research Center (WHRC) in Woods Hole, MA, are working with NASA and conservationists in the Virunga National Park to stave off further destruction of the lands.

"Remote sensing is the only tool that we have to efficiently monitor these remote parks," says Nadine Laporte, head of the Africa Program at WHRC. "Satellite imagery allows park managers to update park property boundaries, map forest habitat, and look at encroachment of the park by comparing images from two different dates."

Laporte is working with conservation groups to create a monitoring system that combines NASA satellite imagery with aerial flight and field surveys, all of which can be relayed to and coordinated with local park rangers on the ground. Currently, park workers are building a three-foot wall along key park borders to keep out cattle and people seeking to alter the land.

NASA now provides free Landsat images, which researchers and rangers are using as base maps for field surveys. "We still have to integrate remote sensing with traditional surveys on the ground," said Laporte. "They really complement each other. The rate of change is so rapid that we need satellite imagery in a timely fashion to address the problems in the area. Aerial imagery is too expensive."

Since gorilla habitat crosses three different countries, satellite imagery provides data and perspectives that are not bound by political borders. The satellite images can create a convenient method for exchanging information among the three parks that make up the Virunga Conservation Area.

Along with mapping and monitoring changes in forest cover, a time-sensitive series of images can allow researchers to estimate rates and patterns of deforestation in and around protected areas. These patterns are also studied in relation to trends in human migration.

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The Africa Program at the Woods Hole Research Center is funded though NASA's Land Cover Land Use Change program, the US Agency for International Development (USAID), and the Wildlife Conservation Society.

SOURCE : National Aeronautics And Space Administration

Brown Argus Butterfly Sees Positive Effects Of Climate Change

2008-07-31T17:41:00.003+07:00

ScienceDaily (June 9, 2008) — Global warming is generally thought to have a negative affect on the habitats of many animals and plants. Not for the Brown Argus butterfly, however. This insect seems to be bucking the trend and expanding its numbers quicker and more effectively, according to new research. agestis has expanded northwards in Britain during the last 30 years. It is thought that the recent expansion of the species is due to the increasing summer temperatures caused by global warming.

The Brown Argus butterfly Aricia agestis has expanded northwards in Britain during the last 30 years.
It is thought that the recent expansion of the species is due to the increasing summer temperatures caused
by global warming. (Credit: iStockphoto/Pauline Mills)

Research carried out by scientists in the UK and Spain reveals that by moving into new areas, the Brown Argus may be escaping from some of its 'natural enemies' (parasitoids).

This is not because natural enemies are absent from the new areas, but that the parasitoids are not able to locate the Brown Argus. Instead, the parasitoids rely on the common blue butterfly Polyommatus icarus in these northern habitats. This species has a long-established range throughout Britain and suffers a larger amount of parasitism than the Brown Argus in these northern habitats.

Although the researchers cannot yet say for certain why the Brown Argus has fewer parasites in its new range, they suggest it could be due to the differences between the plants that the caterpillars eat. The common blue and brown argus feed on different plants and therefore the parasitoids are used to looking for caterpillars on the common blue's favourite plants.

Dr Rosa Menendez said: "Climate change can have unpredicted consequences by altering the interaction between species and their enemies, whilst in this case the butterfly may be a welcome addition in other cases the release from enemies might favour pests or other unwanted species".

SOURCE : Wiley-Blackwell

Insect Attack May Have Finished Off Dinosaurs

2008-07-30T17:16:00.000+07:00

Asteroid impacts or massive volcanic flows might have occurred around the time dinosaurs became extinct, but a new arguemet is that the mightiest creatures the world has ever known may have been brought down by a tiny, much less dramatic force -- biting, disease-carrying insects.

An important contributor to the demise of the dinosaurs, experts say, could have been the rise and evolution of insects, especially the slow-but-overwhelming threat posed by new disease carriers. And the evidence for this emerging threat has been captured in almost lifelike-detail -- many types of insects preserved in amber that date to the time when dinosaurs disappeared.

"There are serious problems with the sudden impact theories of dinosaur extinction, not the least of which is that dinosaurs declined and disappeared over a period of hundreds of thousands, or even millions of years," said George Poinar Jr., a courtesy professor of zoology at Oregon State University. "That time frame is just not consistent with the effects of an asteroid impact. But competition with insects, emerging new diseases and the spread of flowering plants over very long periods of time is perfectly compatible with everything we know about dinosaur extinction."

Tick found in Burmese amber. (Credit: Image courtesy of Oregon State University)

This concept is outlined in detail in "What Bugged the Dinosaurs? Insects, Disease and Death in the Cretaceous," a book by George and Roberta Poinar, just published by Princeton University Press.

In it, the authors argue that insects provide a plausible and effective explanation for the slow, inexorable decline and eventual extinction of dinosaurs over many thousands of years. This period is known as the famous "K-T Boundary," or the line between the Cretaceous and Tertiary Period about 65 million years ago. There is evidence that some catastrophic events, such as a major asteroid or lava flows, also occurred at this time -- but these provide no complete explanation for the gradual decline of dinosaur populations, and even how some dinosaurs survived for thousands of years after the K-T Boundary.

Insects and disease, on the other hand, may have been a lot slower, but ultimately finished the job.

"We don't suggest that the appearance of biting insects and the spread of disease are the only things that relate to dinosaur extinction," Poinar said. "Other geologic and catastrophic events certainly played a role. But by themselves, such events do not explain a process that in reality took a very, very long time, perhaps millions of years. Insects and diseases do provide that explanation."

Poinar and his wife, Roberta, have spent much of their careers studying the plant and animal life forms found preserved in amber, using them to re-create the biological ecosystems that were in place millions of years ago. They are also authors of "The Amber Forest: A Reconstruction of a Vanished World."

As a semi-precious gem that first begins to form as sap oozing from a tree, amber has the unique ability to trap very small animals or other materials and -- as a natural embalming agent -- display them in nearly perfect, three-dimensional form millions of years later. This phenomenon has been invaluable in scientific and ecological research, and among other things, formed the scientific premise for the movie Jurassic Park, for the "dinosaur DNA" found in mosquitoes.

"During the late Cretaceous Period, the associations between insects, microbes and disease transmission were just emerging," Poinar said. "We found in the gut of one biting insect, preserved in amber from that era, the pathogen that causes leishmania -- a serious disease still today, one that can infect both reptiles and humans. In another biting insect, we discovered organisms that cause malaria, a type that infects birds and lizards today.

"In dinosaur feces, we found nematodes, trematodes and even protozoa that could have caused dysentery and other abdominal disturbances. The infective stages of these intestinal parasites are carried by filth-visiting insects."

In the Late Cretaceous, Poinar said, the world was covered with warm-temperate to tropical areas that swarmed with blood-sucking insects carrying leishmania, malaria, intestinal parasites, arboviruses and other pathogens, and caused repeated epidemics that slowly-but-surely wore down dinosaur populations. Ticks, mites, lice and biting flies would have tormented and weakened them.

"Smaller and separated populations of dinosaurs could have been repeatedly wiped out, just like when bird malaria was introduced into Hawaii, it killed off many of the honeycreepers," Poinar said. "After many millions of years of evolution, mammals, birds and reptiles have evolved some resistance to these diseases. But back in the Cretaceous, these diseases were new and invasive, and vertebrates had little or no natural or acquired immunity to them. Massive outbreaks causing death and localized extinctions would have occurred."

In similar fashion, the researchers suggest, insects would have played a major role in changing the nature of plant life on Earth -- the fundamental basis for all dinosaur life, whether herbivore, omnivore or carnivore. As the dinosaurs were declining, their traditional food items such as seed ferns, cycads, gingkoes and other gymnosperms were largely being displaced by flowering plants, which insects helped spread by their pollination activities. These plants would have spread to dominate the landscape. Also, insects could have spread plant diseases that destroyed large tracts of vegetation, and the insects could have been major competitors for the available plant food supply.

"Insects have exerted a tremendous impact on the entire ecology of the Earth, certainly shaping the evolution and causing the extinction of terrestrial organisms," the authors wrote in their book. "The largest of the land animals, the dinosaurs, would have been locked in a life-or-death struggle with them for survival."

The confluence of new insect-spread diseases, loss of traditional food sources, and competition for plants by insect pests could all have provided a lingering, debilitating condition that dinosaurs were ultimately unable to overcome, the researchers say. And these concerns -- which might have pressured the dinosaurs for thousands of years -- may have finished the job, along with the changing environment, meteor impacts and massive lava flows.

"We can't say for certain that insects are the smoking gun, but we believe they were an extremely significant force in the decline of the dinosaurs," Poinar said. "Our research with amber shows that there were evolving, disease-carrying vectors in the Cretaceous, and that at least some of the pathogens they carried infected reptiles. This clearly fills in some gaps regarding dinosaur extinctions."

SOURCE : Oregon State University

Leaf Age May Contribute To Contamination Of Lettuce With E. Coli And Salmonella

2008-07-30T16:21:00.000+07:00

A new study presents the first evidence that harmful pathogens frequently linked with food-borne illnesses are more commonly found on younger inner leaves than on older outer leaves of romaine lettuce. The researchers from the Produce Safety and Microbiology Research Unity, Albany, California and the University of California, Berkley report their findings in the journal Applied and Environmental Microbiology.

Lettuce (Lactuca sativa) is the fresh produce item most commonly implicated in epidemics of food-borne illness, while Escherichia coli O157:H7 and Salmonella enterica are the most frequently attributed bacterial agents. Although previous studies have focused on E. coli O157:H7 colonization on cut or shredded lettuce leaves, little is known of its ability to colonize whole lettuce leaves in both pre- and post-harvest environments.

In the study researchers investigated the growth of E. coli O157:H7 and S. enterica on romaine lettuce leaves both pre- and post-harvest. The increased population size of E. coli O157:H7 on young lettuce plants ranged from 16- to 100-fold in the presence of warm temperatures and free water on the leaves.

The increase in population size also varied significantly with leaf age, however the colonization was consistently 10-fold higher on the young (inner) leaves than on the middle leaves. Growth rates of S. enterica were found to be similarly leaf age dependent. Both bacterial pathogens also displayed higher population rates on younger leaves than on middle leaves harvested from mature lettuce heads.

"Our results indicate that leaf age and nitrogen content contribute to shaping the bacterial communities of preharvest and postharvest lettuce and that young lettuce leaves may be associated with a greater risk of contamination with E. coli O157:H7.

Journal reference: M.T. Brandl, R. Amundson. 2008. Leaf age as a risk factor in contamination of lettuce with Escherichia coli O157:H7 and Salmonella enterica. Applied and Environmental Microbiology, 74. 8: 2298-2306.

SOURCE : American Society for Microbiology

How Cranberry Juice Can Prevent Urinary Tract Infections

2008-07-30T15:13:00.000+07:00

For generations, people have consumed cranberry juice, convinced of its power to ward off urinary tract infections, though the exact mechanism of its action has not been well understood. A new study by researchers at Worcester Polytechnic Institute (WPI) reveals that the juice changes the thermodynamic properties of bacteria in the urinary tract, creating an energy barrier that prevents the microorganisms from getting close enough to latch onto cells and initiate an infection.

The study, published in the journal Colloids and Surfaces: B, was conducted by Terri Camesano, associate professor of chemical engineering at WPI, and a team of graduate students, including PhD candidate Yatao Liu. They exposed two varieties of E. coli bacteria, one with hair-like projections known as fimbriae and one without, to different concentrations of cranberry juice. Fimbriae are present on a number of virulent bacteria, including those that cause urinary tract infections, and are believed to be used by bacteria to form strong bonds with cells.

For the fimbriaed bacteria, they found that even at low concentrations, cranberry juice altered two properties that serve as indicators of the ability of bacteria to attach to cells. The first factor is called Gibbs free energy of attachment, which is a measure of the amount of energy that must be expended before a bacterium can attach to a cell. Without cranberry juice, this value was a negative number, indicating that energy would be released and attachment was highly likely. With cranberry juice the number was positive and it grew steadily as the concentration of juice increased, making attachment to urinary tract cells increasingly unlikely.

Surface free energy also rose, suggesting that the presence of cranberry juice creates an energy barrier that repels the bacteria. The researchers also placed the bacteria and urinary tract cells together in solution. Without cranberry juice, the fimbriaed bacteria attached readily to the cells. As increasing concentrations of cranberry juice were added to the solution, fewer and fewer attachments were observed.

Cranberry juice had no discernible effect on E. coli bacteria without fimbriae, suggesting that compounds in the juice may act directly on the molecular structure of the fimbriae themselves. This reinforces previous work by the WPI team that showed that exposure to cranberry juice alters the shape of the fimbriae, causing them to become compressed. Using an atomic force microscope as a minute strain gauge, the team also showed that the adhesive force exerted by bacteria on urinary tract cells declined in direct proportion to the concentration of cranberry juice in the solution.

"Our results show that, at least for urinary tract infections, cranberry juice targets the right bacteria--those that cause disease--but has no effect on non-pathogenic organisms, suggesting that cranberry juice will not disrupt bacteria that are part of the normal flora in the gut," Camesano says. "We have also shown that this effect occurs at concentrations of cranberry juice that are comparable to levels we would expect to find in the urinary tract."

Camesano notes that unpublished work has shown that while cranberry juice has potent effects on disease-causing bacteria, those effects are transitory. "When we takes E. coli. bacteria that have been treated with cranberry juice and place them in normal growth media, they regain the ability to adhere to urinary tract cells," she says. "This suggests that to realize the antibacterial benefits of cranberry, one must consume cranberry juice regularly--perhaps daily."

For those watching calories, Camesano says other recent work in her lab has shown that the effects of regular cranberry juice cocktail and diet (sugar-free) cranberry juice are identical. "That's good news for people who do not like to consume a lot of sugary juice," she says.

SOURCE : Worcester Polytechnic Institute

New Invention Effectively Kills Foodborne Pathogens In Minutes

2008-07-29T16:36:00.000+07:00

Scanning electron micrograph of highly magnified Salmonella infantis bacteria.
(Credit: CDC/Janice Carr)

University of Georgia researchers have developed an effective technology for reducing contamination of dangerous bacteria on food. The new antimicrobial wash rapidly kills Salmonella and E. coli O157:H7 on foods ranging from fragile lettuce to tomatoes, fruits, poultry products and meats. It is made from inexpensive and readily available ingredients that are recognized as safe by the U.S. Food and Drug Administration.

The new technology, which has commercial application for the produce, poultry, meat and egg processing industries, is available for licensing from the University of Georgia Research Foundation, Inc., which has filed a patent application on the new technology.

The Centers for Disease Control and Prevention estimates that, in the U.S. alone, foodborne pathogens are responsible for 76 million illnesses every year. Of the people affected by those illnesses, 300,000 are hospitalized and more than 5,000 die. These widespread outbreaks of food-borne illnesses are attributed, in part, to the fast-paced distribution of foods across the nation. Recently, raw tomatoes caused an outbreak of salmonellosis that sickened more than 300 people in at least 28 states and Canada.

Currently, a chlorine wash is frequently used in a variety of ways to reduce harmful bacteria levels on vegetables, fruits and poultry, but because of chlorine's sensitivity to food components and extraneous materials released in chlorinated water treatments, many bacteria survive. Chlorine is toxic at high concentrations, may produce off-flavors and undesirable appearance of certain food products, and it can only be used in conjunction with specialized equipment and trained personnel. In addition, chlorine may be harmful to the environment.

"We can't rely on chlorine to eliminate pathogens on foods," said Michael Doyle, one of the new technology's inventors and director of UGA's Center for Food Safety. "This new technology is effective, safe for consumers and food processing plant workers, and does not affect the appearance or quality of the product. It may actually extend the shelf-life of some types of produce."

Doyle is an internationally recognized authority on food safety whose research focuses on developing methods to detect and control food-borne bacterial pathogens at all levels of the food continuum, from the farm to the table. He has served as a scientific advisor to many groups, including the World Health Organization, the Food and Drug Administration, the U.S. Department of Agriculture, the U.S. Department of Defense and the U.S. Environmental Protection Agency.

The new antimicrobial technology, developed by Doyle and Center for Food Safety researcher Tong Zhao, uses a combination of ingredients that kills bacteria within one to five minutes from application. It can be used as a spray and immersion solution, and its concentration can be adjusted for treatment of fragile foods such as leafy produce, more robust foods such as poultry, or food preparation equipment and food transportation vehicles.

"The effectiveness, easy storage and application, and low cost of this novel antibacterial make it applicable not only at food processing facilities, but also at points-of-sale and at home, restaurants and military bases. The development of this technology is timely, given the recent, sequential outbreaks of foodborne pathogens," said Gennaro Gama, UGARF technology manager in charge of licensing this technology.

SOURCE : University of Georgia

Protozoa May Enable Food-Borne Pathogens On Leafy Vegetables

2008-07-29T15:02:00.000+07:00

Protozoa found on lettuce and spinach may sequester harmful food-borne pathogens ultimately contributing to their survival on produce surfaces say researchers from Tennessee Technological University, Cookeville and the Produce Safety and Microbiology Research Unit, Albany, California.

Several outbreaks of food-borne illnesses attributed to Escherichia coli O157:H7 and Salmonella enterica have received national attention in recent years. The Centers for Disease Control and Prevention reported that fresh produce was the most significant source of food-borne illness in 2005.

Protozoa are single-celled organisms whose main function is bacterial consumption. They are commonly found in the natural microflora of plants and several species of amoebae have been associated with fresh salad vegetables. The recent occurrence of multiple outbreaks has encouraged researchers to further examine the interaction between food-borne pathogens and protozoa.

In the study protozoa (Glaucoma sp., Colpoda steinii, and Acanthamoeba palestinensis) as well as the soil-borne strain, Tetrahymena pyriformis, were cultured from store-bought spinach and lettuce and washed and allowed to graze on green fluorescent protein- or red fluorescent protein-labeled enteric pathogens including E. coli O157:H7, S. enterica, and Listeria monocytogenes.

They were then monitored for their ability to sequester the bacteria and for vesicle production (food vacuoles released by protozoa offering a means of protection to some bacteria). Results showed Glaucoma produced vesicles with all bacterial strains and Tetrahymena also displayed vesicle production, but only of E. coli O157:H7 and S. enterica, not L. monocytogenes. Further studies of E. coli O157:H7 following vesicle production revealed that 4 hours after the addition of spinach extract, the bacteria had multiplied and escaped the vesicles. C. steinii did not produce any vesicles from any of the pathogens.

"The presence of protozoa on leafy vegetables and their sequestration of enteric bacteria in vesicles indicate that they may play an important role in the ecology of human pathogens on produce," say the researchers.

Journal reference: P. Gourabathini, M.T. Brandl, K.S. Redding, J.H. Gunderson, S.G. Berk. 2008. Interactions between food-borne pathogens and protozoa isolated from lettuce and spinach. Applied and Environmental Microbiology, 74. 8: 2518-2525.

SOURCE : American Society for Microbiology

Milkweed's Evolutionary Approach To Caterpillars: Counter Appetite With Fast Repair

2008-07-29T10:09:00.000+07:00

The adage that your enemies know your weaknesses best is especially true in the case of plants and predators that have co-evolved: As the predators evolve new strategies for attack, plants counter with their own unique defenses.

Milkweed is the latest example of this response, according to Cornell research suggesting that plant may be shifting away from elaborate defenses against specialized caterpillars toward a more energy-efficient approach. Genetic analysis reveals an evolutionary trend for milkweed plants away from resisting predators to putting more effort into repairing themselves faster than caterpillars -- particularly the monarch butterfly caterpillar -- can eat them.

"An important question with co-evolution is where does it end?" said Anurag Agrawal, Cornell associate professor of ecology and evolutionary biology and lead author of a paper in the current issue of the Proceedings of the National Academy of Sciences. "One answer is when it becomes too costly. Some plants seem to have shifted away from resisting herbivory [plant eating] and have taken that same energy and used it to repair themselves."

The paper is important because it sheds light on key theories of co-evolution, claiming that pressure by foraging insects makes plants diversify as they evolve new defensive strategies and that such diversification follows trends in one direction or another, said Agrawal.

Milkweed species have evolved elaborate resistance strategies to fight off caterpillars that eat their leaves. These include hairs on their leaves, heart poisons called cardenolides in their tissues and milky-white toxic latex that pours from the plants' tubes. A caterpillar's bite into a milkweed leaf leads to a flood of latex that is "like getting a gallon of sticky paint thrown into your face," said Agrawal.

Some caterpillars, in turn, have adapted by shaving the leaf, cutting a leaf's veins in a circle and then eating in the middle where the latex doesn't flow. Also, the monarch caterpillar has become immune to the cardenolides.

Using DNA sequence data to look at relationships between 38 species of milkweed, Agrawal and colleague Mark Fishbein, a Portland State University biologist, found evolutionary declines in milkweed's three most important resistance traits (hairs, cardenolides and latex) and an escalation in the plant's ability to regrow.

Agrawal was surprised, he said, to find that the plant became more tolerant rather than more diverse in its defenses. The reason, he speculated, could be because as its predators have become so specialized, the plant was better off choosing a new defensive tactic "to tolerate the herbivory damage instead of resisting it." It is unknown whether such strategies have also evolved in animals trying to evade parasites.

The findings address questions about plant evolution, biodiversity and keystone species and may give plant scientists clues about profitable pest control strategies.

The study was funded by the National Science Foundation.

SOURCE : Cornell University

Dinosaurs Did Not Evolve Quickly In Last 50 Million Years, New Dinosaur Super-tree Shows

2008-07-28T17:01:00.000+07:00

It has long been debated whether dinosaurs were part of the ‘Terrestrial Revolution’ that occurred some 100 million years ago during the Cretaceous when birds, mammals, flowering plants, insects and reptiles all underwent a rapid expansion.

Super-tree of dinosaurs with 440 species listed.
(Credit: Image courtesy of Graeme Lloyd, Bristol University)

An international study, led by the University of Bristol, shows that during their last 50 million years of existence, dinosaurs were not expanding as actively as had been previously thought and that the apparent explosion of dinosaur diversity may be largely explained by sampling bias.

The team produced a ‘supertree’ of dinosaurs, showing the most likely pattern of evolution for 440 of the 600 known species of dinosaur. "Supertrees are very large family trees made using sophisticated computer techniques that carefully stitch together several smaller trees which were previously produced by experts on the various subgroups”, explained lead author Graeme Lloyd.

“Our supertree summarises the efforts of two decades of research by hundreds of dinosaur workers from across the globe and allows to look for unusual patterns across the whole of dinosaurs for the first time." It is the most comprehensive picture ever produced of how dinosaurs evolved.

Professor Mike Benton from Bristol University said: "It's not complete, but it's the most detailed and comprehensive single evolutionary tree produced for dinosaurs, and indeed for almost any other group.

"Up until now, most studies of the evolution of dinosaurs were not tested numerically against an accurate and comprehensive database. We hope our study will mark the first of a new wave of such thorough, quantitative studies in palaeontology."

The new study uses statistical techniques to distinguish unusually high rates of diversification from normal rates. The results show that all the bursts of diversification happened in the first fifty million years of the evolution of dinosaurs. Later expansions were not distinguishable from normal rates. This suggests dinosaurs did not take advantage of the new food supplies available during the Cretaceous Terrestrial Revolution – such as flowering plants, lizards, snakes, birds and mammals.

The work was done using the High Performance Computing facilities of the National University of Ireland, Maynooth. It was based on a combination of 155 published dinosaur ‘trees’ and took approximately 5,000 hours of calculation time.

The key focus was to see whether dinosaurs had been part of a major phase of evolution on land – the Cretaceous Terrestrial Revolution (between 125–80 million years ago) – when many new groups of plants and animals expanded rapidly. During this time, the flowering plants and social insects arose and became more and more common. Many backboned animals also expanded to take advantage of the new sources of food.

SOURCE : Bristol University

Pollination Habits Of Endangered Texas Rice Revealed To Help Preservation

2008-07-28T11:47:00.000+07:00

A type of wild rice that only grows in a small stretch of the San Marcos River is likely so rare because it plays the sexual reproduction game poorly, a study led by the Lady Bird Johnson Wildflower Center at The University of Texas at Austin has revealed.

Aerial stems (culms) of Texas wild-rice.
(Credit: Flo Oxley, director of conservation at the Lady Bird Johnson Wildflower Center
at The University of Texas at Austin.)

The first study of breeding habits of this endangered, aquatic grass (Zizania texana) found that the pollen of Texas wild-rice can only travel about 30 inches away from a parent plant. If pollen doesn't land on a receptive female flower within that distance, no seeds will be produced. No seeds means no new plants to replenish a population that faces other survival threats.

"It would be great to introduce more of these plants into the San Marcos River so that we can build up its population, said Flo Oxley, conservation director at the Wildflower Center, and lead author of the study.

"This information will be useful when reintroduction efforts begin, because we now know that lots of new plants must be planted close together in order for seeds to be produced."

The findings were published in June in The Southwestern Naturalist journal of the Southwestern Association of Naturalists, and shared with staff at the U.S. Fish and Wildlife Service and the Texas Parks and Wildlife Department.

The U.S. Fish and Wildlife Service is the principal federal agency responsible for federally listed species conservation. Texas has about 25 percent of the plant biodiversity nationally, including 23 endangered and five threatened plant species.

Texas wild-rice prefers the clean, clear water of the San Marcos River and is not found anywhere else. The plant spends most of its life submerged, emerging only to flower. Recreation on the river can stir up sediments that prevent sunlight from reaching the plants, and swimmers, tubers and canoers often submerge the plants' flowers so they can't pollinate. This foot traffic isn't expected to go away soon, and the flow of underground water into springs that feed the river is also decreasing as the Central Texas population expands and drinking water needs increase.

"Nobody intends to shut down access to the river because of these plants" Oxley said, "and I've been surprised at how respectful of the plant people are when they learn that it is an endangered species that grows only in the San Marcos River and nowhere else in the world. Texans are very proud and protective of their natural history, and I believe they will take care of Texas wild-rice if we just let them know about it."

It doesn't hurt, she added, that Texas wild-rice serves as home for tiny invertebrates that have nasty feeding habits.

"People who swim through Texas wild-rice risk picking up these aquatic hitchhikers and may end up with itchy behinds for their efforts," she said.

Texas wild-rice is a food source and home for endangered fish called fountain darters, and is a cousin to several rice species cultivated for food purposes. But it is among more than 200 plant species of concern in Texas whose fundamental value isn't understood because so little information has been available to guide conservation or other decisions.

"We don't know what overall purpose this plant serves in the ecosystem, and we don't know what's going to happen if this plant goes away, Oxley said.

"To paraphrase what Aldo Leopold once said, ‘Whenever you tinker with Nature, be sure to keep all the parts.' Texas wild-rice is definitely one of those important parts."

SOURCE : University of Texas at Austin

Controlling Invasive Cane Grass With Wasps?

2008-07-28T11:22:00.000+07:00

Researchers at The University of Texas at Austin will work with the U.S. Department of Agriculture, Agricultural Research Service (USDA-ARS) to investigate biological control for an invasive cane grass that is choking waterways across North America.

Also known as Carrizo and giant cane, the grass is growing along extensive stretches of the Rio Grande in Texas and can be found along Austin waterways such as Shoal Creek. It grows up to 20 feet tall, uses large amounts of water and may crowd out other plant species and affect wildlife.

Dr. Larry Gilbert and his colleagues at the Brackenridge Field Laboratory (BFL) will study wasps that attack the cane under the direction of USDA research entomologists Drs. John Goolsby and Patrick Moran.

The wasps create growths called galls that could stress the plants and reduce their competitive advantage.

"The very basic biology of these wasps and how they interact with the plants is not known," says Gilbert, director of BFL. "We're just beginning to work it out."

Gilbert's team will be researching effective means for mass rearing the wasps and studying basics of the plant-wasp interaction inside a new greenhouse being completed at BFL.

The field lab is home to other biocontrol research—controlling imported fire ants using a small fly—and Gilbert says that experience has prepared the BFL researchers for their work investigating biocontrol of the giant cane, which has also invaded the station property.

The wasps are one of the many aspects of the cane's biology and ecology being studied by the USDA's Goolsby and Moran.

SOURCE : The University of Texas at Austin

New Satellite Imaging Research Could Save The Lemur In Madagascar

2008-07-27T22:04:00.000+07:00

New satellite imaging research may help save the dwindling lemur population in the African nation of Madagascar.

Using satellite imagery, GIS and ecological and demographic data from the field, Robert W. Sussman, Ph.D., professor of anthropology in Arts & Sciences at Washington University in St. Louis, has studied the effects of deforestation on the ringtailed lemur population in Madagascar during the last forty years.

Lemur population in Madascar has declined sharply since the 1950s.
Through education and conservation, a WUSTL expert hopes the trend will one day be reversed.
(Credit: Image courtesy of Washington University in St Louis)

He has determined that while causes of deforestation vary in different parts of the African island nation, the total lemur (lemur catta) population has dropped by more than half since the 1950s. Sussman discussed his long-term field research project in "Habitat Monitoring by GPS in Madagascar" during the "From Global to Local: Impact of Field Research in Biological Anthropology" session Sunday, Feb. 17, at the annual meeting of the American Association for the Advancement of Science in Boston, Mass.

Sussman, who first began studying lemur populations in Madagascar in 1969, continues to conduct and coordinate long-term research of the demography, ecology and social organization of lemurs at the Beza Mahafaly Reserve and in southern Madagascar.

He is co-founder of the reserve, which began as part of a cooperative program in research, conservation, education and development between Washington University in St. Louis, Yale University and the University of Madagascar (currently University of Antananarivo), which also manages the reserve.

In the years since its development in 1978, hundreds of research papers have been written about the flora, fauna and people of Madagascar. Education programs on the local animals and conservation have been developed for the local people. Many non-Malagasy students have completed their doctoral field work in the area, and more than 100 local students have earned graduate degrees based on research done at and around the reserve.

Sussman now uses the reserve as a base for his GIS and satellite imagery studies of southwestern Madagascar — the entire range of the ringtailed lemurs. He is looking at the relationship between deforestation, land use by the human population, and the density and distribution of ringtailed lemurs.

While sifting through satellite data going back to 1950, Sussman and colleagues have determined a measure of "greenness" of the land over time. There is an 80 percent correlation between the level of greenness and the lemur population density, said Sussman. The lemurs congregate in the greener areas, but those areas are also the ones being deforested at the fastest rate.

While it is estimated that the lemur population in Madagascar has dropped to a total of approximately 750,000 from more than 1.5 million in the 1950s, Sussman hopes the trend will one day be reversed.

"Through education and conservation, we can make positive steps," he said. "We must work with the local people to help stop the damaging effects of deforestation, not only to the animal populations, but to the human population as well."

SOURCE : Washington University in St Louis

Antimicrobials Target Pathogens On Fruits And Vegetables

2008-07-27T14:49:00.000+07:00

A novel food safety treatment tested by Agricultural Research Service (ARS) scientists could become an asset to the fast-growing fresh-cut produce industry.

Bacteriophages are showing promise as a way to control E. coli on lettuce and fresh cantaloupe.
(Credit: iStockphoto/Zoran Kolundzija)

The antimicrobial treatment involves the use of submicroscopic agents that are unable to reproduce or grow outside bacterial host cells. The purified viral agents are called bacteriophages, which means "bacteria eater," and they can wreak havoc on deadly bacteria, such as E. coli O157:H7, that sicken consumers.

The bacteriophage research is being conducted by microbiologist Manan Sharma, with the ARS Food Safety Laboratory, in Beltsville, Md., in collaboration with researchers at Intralytix, Inc., based in Baltimore, Md.

Interest in bacteriophages is ramping up with the emergence of antibiotic-resistant organisms. These "phages" are present in the environment and only attack bacteria; they do not have an adverse effect on humans and animals.

Sharma tested a group of phages (ECP-100) on refrigerated samples of fresh-cut cantaloupe. The treatments reduced pathogens on the samples of fresh-cut cantaloupe by 100-fold in comparison to untreated samples.

Sharma also tested the phages on refrigerated fresh-cut lettuce. The results indicate that bacteriophage treatments can kill E. coli O157:H7 on the surface of leafy green commodities with the same level of efficiency seen in the fresh-cut cantaloupe.

Phages reproduce by latching onto bacteria. The viral DNA is injected into the bacterial hosts' cells, where it directs the production of progeny phages. These phages kill bacterial host cells on exit, and then move on to infect more bacterial cells.

The trials indicated that the phage treatments could be effective in killing E. coli O157:H7 in produce.

SOURCH : USDA/Agricultural Research Service

Botanists Identify New Species Of North American Bamboo

2008-07-27T12:35:00.000+07:00

Two Iowa State University botanists and their colleague at the University of North Carolina have discovered a new species of North American bamboo in the hills of Appalachia. It is the third known native species of the hardy grass. The other two were discovered more than 200 years ago.

ISU botanists Lynn Clark and Jimmy Triplett study bamboo diversity and evolution. They first heard about "hill cane" from University of North Carolina botanist Alan Weakley. As soon as they saw it, they knew it was different.

'Hill cane'

Lynn Clark, Iowa State professor of ecology, evolution and organismal biology, and Ph.D. student Jimmy Triplett study bamboo diversity and evolution. They first heard about "hill cane" from Alan Weakley, a botanist at the University of North Carolina. Although the plant was known to the people in the area, its distinctiveness was not recognized.

Hill cane differs from the other two native North American bamboo species -- commonly known as switch cane and river cane -- in an important way: It drops its leaves in the fall.

"That's why it was recognized locally as being different," Clark said. "It's pretty uncommon for bamboos to drop their leaves."

Clark should know. She's an internationally recognized bamboo expert. She had previously discovered 74 new species of bamboo.

"All the other new ones came from Central and South America," she said. "It's so exciting to find a new species in our own backyard!"

Her 75th species discovery has been named Arundinaria appalachiana. Clark, Triplett and Weakley recently completed the intricate process botanists are obliged to follow to officially name and describe a newfound species. Following rules laid out in the International Code of Botanical Nomenclature, they prepared a short description of the plant in Latin and a longer one in English, and provided drawings and other information to make a strong case for the recognition of A. appalachiana as a distinct species of bamboo. They submitted their evidence in a manuscript to the scientific journal Sida, Contributions to Botany, convincing the peer reviewers that the bamboo they discovered was new. Their study was published last fall.

Bamboos of North America

There are 1,400 known species of bamboo. Of those, about 900 are tropical and 500 are temperate. The bamboos of North America are found in the Eastern and Southeastern United States, from New Jersey south to Florida and west to Texas. River cane (Arundinaria gigantea) occurs in low woods and along riverbanks. Switch cane (Arundinaria tecta) is found in non-alluvial swamps, moist pine barrens, live oak woods and along sandy margins of streams.

"Most people have no idea that we have native bamboo in the U.S.," Clark said. "But it has been a very important plant ecologically. And there's recent interest in using it for re-vegetation projects because it's native and was used for habitat by so many different animals, especially birds."

Building a bamboo family tree

Clark and Triplett began looking at the North American bamboos as part of a larger collaboration with botanists worldwide to develop an evolutionary family tree of bamboo species. They're using modern DNA sequencing technologies together with traditional plant taxonomy, which involves observation and description of a plant's form, anatomy, ecology and other characteristics.

"We want to get the big picture of how all the temperate bamboos are related to each other. That means taking inventory of what exists, then comparing notes," Clark said.

They already know that the closest relatives of native North American bamboos are not in Central or South America, but are in East Asia.

"That's a well-known pattern of diversity in plants and animals. Plants known to be closely related that were previously found across a large area of the earth are only in those two areas now. For various reasons, the Eastern U.S. and East Asia are a repository for a lot of diversity," Clark said.

"But we still don't understand exactly how long it has been since our bamboos separated from their Asiatic cousins. And we don't know how we ended up with three species in North America and 500 in East Asia," she said.

Although botanists had previously studied the North American bamboos, no one had done extensive fieldwork to study and collect the plants in the wild, and questions remained as to whether there was really more than just a single species. In 2003, with funding from the National Geographic Society, Clark and Triplett set off for the Southeast to find the switch cane and river cane in their native habitats.

They knew it was different

"Once we actually saw the plants in the field, we knew quickly that there were two distinct species," Clark said. "But we kept hearing about a third plant, called hill cane."

And as soon as they saw it, they knew it was different.

SOURCE : Iowa State University

Reclaimed Wastewater Benefits Florida's Citrus Orchards

2008-07-26T23:26:00.000+07:00

he Sunshine State has seen rapid growth in population during the last 50 years. The 1997 U.S. Census showed that the population of Florida increased more than five-and-a-half times from 1950 to 2000. Naturally, along with population increases, Florida is experiencing an increase in the amount of municipal waste. Studies confirm that the amount of wastewater generated by cities in Florida has increased more than fivefold since 1950.

Environmental concerns about pollution of surface waters by treated wastewater have caused many communities to consider alternate ways to use secondary-treated, or reclaimed, wastewater. Before 1986, the city of Orlando and Orange County were discharging wastewater into a creek that flows into Lake Tohopekaliga in central Florida. To address concerns that the process would affect the quality water in the lake, city and county officials, along with the U.S. Environmental Protection Agency, devised a plan to use the wastewater for agricultural irrigation.

According to a 2005 report by the Florida Department of Environmental Protection, there are currently 440 "reclaimed water reuse systems" in Florida, irrigating thousands of acres of golf courses, public land, and residential landscapes with 2,385 million liters of reclaimed water per day. Reclaimed wastewater is also being used to irrigate some of Florida's world-renowned citrus orchards. Because yearly rainfall in Florida is seasonal, with 75% of annual rainfall usually occurring between June and September, citrus growers rely on supplemental irrigation for healthy citrus crops.

In a study supported by the City of Orlando and Orange County (FL), researchers set out to determine whether long-term irrigation with treated municipal wastewater reduced citrus tree health, (appearance and leaf nutrient content), decreased fruit loads, impacted fruit quality, or created increases in soil contaminants. Dr. Kelly T. Morgan, a scientist at the University of Florida's, Southwest Florida Research and Education Center, published the study report in the April, 2008 issue of HortScience.

Dr. Morgan explained, "Increased water use by the growing population and localized water shortages during low rainfall years have resulted in the development of water use restrictions and decreases in permitted water use for agriculture. Increased use of reclaimed water for agricultural irrigation would not only reduce the wastewater disposal problem for urban areas, but could also reduce the amount of water withdrawn from Florida's aquifers used for irrigation."

The yearly monitoring project, which began in the 1990s and ended in 2004, concluded that using reclaimed water for irrigation of citrus orchards showed few detrimental effects on the orchards. Morgan commented, "Appearance of trees irrigated with reclaimed water was usually better, with higher canopy, leaf color, and fruit crop ratings than orchards irrigated with groundwater. Although there was higher weed growth in reclaimed water-irrigated orchards due to higher soil water content, growers apparently have made adequate adjustments to their herbicide practices."

Researchers concluded that long-term citrus irrigation with high-quality reclaimed water on well-drained sandy soils did not significantly reduce tree viability or yield and required relatively little adjustment in crop production practices: good news for the environment and citrus producers alike.

SOURCE : American Society for Horticultural Science

New Coral Bleaching Prediction System Calls For Low Level Of Bleaching In Caribbean This Year

2008-07-26T22:11:00.001+07:00

A new NOAA coral bleaching prediction system indicates that there will be some bleaching in the Caribbean later this year, but the event will probably not be severe. NOAA issued the first-ever seasonal coral bleaching outlook this week at the 11th International Coral Reef Symposium in Ft. Lauderdale, Fla.

Large colony of bleached Montastrea annularis. (Credit: NOAA)

The system also suggests that there is a risk of widespread bleaching in the Northwestern Hawaiian Islands in August, but little bleaching elsewhere during the northern hemisphere summer.

"The ability to predict coral bleaching events and provide advance warning is critically important to sustaining healthy reefs," said Tim Keeney, deputy assistant secretary of commerce for oceans and atmosphere and co-chair of the United States Coral Reef Task Force. "When coral reef managers and reef users are alerted, they can mobilize monitoring efforts, develop response strategies, and educate reef users and the public on coral bleaching and possible effects on reef resources."

The new prediction system uses NOAA experimental sea surface temperature forecasts to develop maps of anticipated coral bleaching severity during the upcoming bleaching season (August to October). While NOAA's Coral Reef Watch Program uses satellite sea surface temperature data to alert managers and scientists around the world of the risk of coral bleaching, the new prediction system includes longer range temperature forecasts up to three-months.

Coral bleaching is associated with a variety of stresses, especially increased ocean temperatures. This causes the coral to expel symbiotic micro-algae living in their tissues -- algae that provide corals with food. Losing their algae leaves coral tissues devoid of color, and thus they appear bleached. Prolonged coral bleaching of over a week can lead to coral death and the loss of coral reef habitats for a range of marine life.

A major coral bleaching event occurred in the Caribbean in 2005, resulting in significant coral death in much of the region.

"As global temperatures continue to climb, predicting coral bleaching becomes even more critical," said C. Mark Eakin, Ph.D., coordinator of NOAA's Coral Reef Watch Program. "Our goal is to issue bleaching forecasts for coral reefs worldwide."

The new system was developed by scientists of NOAA's Coral Reef Watch in Silver Spring, Md. and NOAA's Earth Science Research Laboratory in Boulder, Colo., with funding from the NOAA Climate Program Office's Sectoral Applications Research Program and NOAA's Coral Reef Conservation Program.

SOURCE : National Oceanic And Atmospheric Administration

'Snapshots' Of Eyes Could Serve As Early Warning Of Diabetes

2008-07-26T10:19:00.000+07:00

A new vision screening device, already shown to give an early warning of eye disease, could give doctors and patients a head start on treating diabetes and its vision complications, a new study shows.

The instrument, invented by two scientists at the University of Michigan Kellogg Eye Center, captures images of the eye to detect metabolic stress and tissue damage that occur before the first symptoms of disease are evident.

For people with diabetes -- diagnosed or not -- the new device could offer potentially significant advantages over blood glucose testing, the "gold standard" for diabetes detection.

The device takes a specialized photograph of the eye and is non-invasive, taking about five minutes to test both eyes.

In the July issue of Archives of Ophthalmology, Victor M. Elner, M.D., Ph.D., and Howard R. Petty, Ph.D., report on the potential of the new instrument to screen for diabetes and determine its severity. If further testing confirms the results to date, the new instrument may be useful for screening people who are at risk of diabetes but haven't been diagnosed.

"Our objective in performing this study was to determine whether we could detect abnormal metabolism in the retina of patients who might otherwise remain undiagnosed based on clinical examination alone," says Elner, professor, Department of Ophthalmology and Visual Sciences at U-M Medical School.

Metabolic stress, and therefore disease, can be detected by measuring the intensity of cellular fluorescence in retinal tissue. In a previous study, Petty and Elner reported that high levels of flavoprotein autofluorescence (FA) act as a reliable indicator of eye disease.

In their new study, Elner and Petty measured the FA levels of 21 individuals who had diabetes and compared the results to age-matched healthy controls. The Kellogg scientists found that FA activity was significantly higher for those with diabetes, regardless of severity, compared to those who did not have the disease. The results were not affected by disease severity or duration and were elevated for diabetics in each age group: 30 to 39 years, 40 to 49 years, and 50 to 59 years.

Given the increasing prevalence of diabetes, the FA device holds the potential to help address a leading and growing public health concern.

Some 24 million Americans have diabetes and an additional 57 million individuals have abnormal blood sugar levels that qualify as pre-diabetes, according to the latest report from the Centers for Disease Control and Prevention. In addition, 4.1 million people over the age of 40 suffer from diabetic retinopathy, an eye-related complication of diabetes that is the leading cause of blindness among working-age adults.

Twelve individuals in the study were known to have diabetic retinopathy, a disease in which blood vessels in the eye are damaged. The individuals with diabetic retinopathy in at least one eye had significantly greater FA activity than people with diabetes who do not have any visible eye disease.

"The abnormal readings indicated that it may be possible to use this method to monitor the severity of the disease," says Elner.

Petty, a biophysicist and imaging expert, explains that hyperglycemia -- or high blood sugar -- is known to induce cell death in diabetic tissue soon after the onset of disease but before symptoms can be detected clinically.

"Increased FA activity is the earliest indicator that cell death has occurred and tissue is beginning to break down," says Petty, professor of Ophthalmology and Visual Sciences, and professor of Microbiology and Immunology at the U-M Medical School. "FA serves as a 'spectral-biomarker' for metabolism gone awry, and we can use the results to detect and monitor disease."

Petty also observes that unlike glucose monitoring, elevation of FA levels reflects ongoing tissue damage. That knowledge, he says, could motivate patients to intensify their efforts to manage the disease.

The Michigan researchers also note that elevated FA does not always mean that an individual has diabetes. "Because of the prevalence of diabetes in our population, individuals with abnormally high FA would be prompted to undergo glucose tolerance testing," says Elner. "If the findings were negative for diabetes, we would look for other causes of ocular tissue dysfunction."

Both Elner and Petty agree that the device has great potential as a tool for diabetes screening and management. "So much damage occurs before the disease can be detected by a doctor," says Elner. "Early diagnosis will allow us to reduce organ damage and prevent many complications that accompany this disease."

Elner and Petty have filed for patents and have formed a company, OcuSciences, Inc., to commercialize the metabolic imaging instrument.

SOURCE : University of Michigan Health System

Bees Go 'Off-color' When They Are Sickly

2008-07-25T23:41:00.000+07:00

Bumble-bees go 'off colour' and can't remember which flowers have the most nectar when they are feeling under the weather, a new study from the University of Leicester reveals.

The behaviour of the bumbling bees reveals that, like humans who are ill, bees are often not at their most astute and clever when they feel poorly.

Lecturer in Animal Biology at the University of Leicester Dr. Eamonn Mallon, who lead the research group, said: "Disease can influence different behaviours including foraging, mate choice, and predator avoidance. Several recent papers have shown reduced learning abilities in infected insects. However, it is difficult to separate the effects of the immune response from the direct effects of the parasite. That was the purpose of our study"

Bees were divided into a control group and a group that were injected with lipopolysaccharide, a substance that stimulated an immune response without a need for the bee to be infected with a disease. Bees were offered the choice of blue and yellow artificial flowers only one type of which contained sugar water. An individual's flight was recorded over ninety visits to these flowers. Eventually the bees spent almost all of their time going to the rewarding flowers, but it took the immune stimulated bees longer to reach this point.

Dr Mallon added: "This work has two important applications. Firstly, there is a lot of interest in the connections between the immune system and the nervous system in human biology. The Mallon lab was the first to show that these interactions also exist in the much more experimentally tractable insects.

"Secondly, there is concern about both the decline in wild bumble-bee species and the effects of disease on the honeybee industry. It has been shown that learning is vitally important to how well a colony prospers. This effect of immunity on learning highlights a previously unconsidered effect of disease on colony success."

Future work will look at the basis of this neuro-immune interaction. Is it due to the immune system using up some resource required to form memories or is it due to the damaging effects of the immune response on the nervous system?

The research was conducted in the Department of Biology, in collaboration with the Department of Genetics, at the University of Leicester. The Leicester team consisted of A. Alghamdi, L. Dalton, A. Phillis, E. Rosato and E. B. Mallon

SOURCE : University of Leicester

Mysterious Mountain Dinosaur May Be New Species

2008-07-25T22:40:00.002+07:00

A partial dinosaur skeleton unearthed in 1971 from a remote British Columbia site is the first ever found in Canadian mountains and may represent a new species, according to a recent examination by a University of Alberta researcher.

This composite shows what bones were found
and what the Sustut dinosaur may have looked like 70 million years ago.
(Credit: University of Alberta, Edmonton, Canada)

Discovered by a geologist in the Sustut Basin of north-central British Columbia 37 years ago, the bones, which are about 70 million years old, were tucked away until being donated to Dalhousie University in 2004 and assigned to then-undergraduate student Victoria Arbour to research as an honours project. She soon realized that the bones were a rare find: they are very well-preserved and are the most complete dinosaur specimen found in B.C. to date. They are also the first bones found in B.C.'s Skeena mountain range.

"There are similarities with two other kinds of dinosaurs, although there's also an arm bone we've never seen before. The Sustut dinosaur may be a new species, but we won't know for sure until more fossils can be found," said Arbour, who finished researching the bones while studying for her master's degree at the University of Alberta. "It's very distinct from other dinosaurs that were found at the same time in southern Alberta."

The seven shin, arm, toe and possible skull bones were found nestled in a dip between mountains in the Skeena range, and while the fragments resemble those from a small two-legged, plant-eating dinosaur, the rest of the creature's identity is a mystery, Arbour says.

The fossils are currently in the collection of the Royal British Columbia Museum in Victoria and Arbour hopes to lead a U of A team to the site for future investigation.

Arbour's findings were published recently in the Canadian Journal of Earth Sciences. The research was funded by NSERC and Alberta Ingenuity.

SOURCE : University of Alberta

More People Are Getting Sick From Eating Fresh Fruits

2008-07-25T16:17:00.001+07:00

St. Paul, MN (January 27, 2003) -- Salmonella, E. coli, shigellosis, hepatitis A, and Norwalk -- these food-borne diseases can produce symptoms that run from the mild to life-threatening. The young and old are particularly vulnerable and while consumption of beef and poultry have been the most common sources of such infections, fresh fruits and vegetables are being increasingly implicated in such outbreaks. So much so, that plant disease scientists are now taking a closer look at this issue.

"Historically, human pathogens like E. coli and Salmonella have rarely been associated with plants, so plant disease scientists have not looked at them directly," says J.W. Buck, a plant pathologist at the University of Georgia. But that is changing, says Buck, as such incidences continue to increase.

Buck says there is no single reason why the number of reported produce-related outbreaks in the U.S. per year doubled between 1973-1987 and 1988-1992 and why they continue to rise. Possible explanations include the simple fact that we are eating more fruits and vegetables than ever before. But experts agree that there is more to it than that and that our food production practices likely bear some responsibility.

But identifying the exact point along the way, from field to grocery store, where a strawberry or head of lettuce, for example, might have become contaminated can be difficult, if not impossible. Unlike other commodities such as beef and chicken, which are rigorously inspected, methods to detect pathogens on fresh produce are less advanced and the sporadic nature of most contamination further limits the effectiveness of testing.

"Plant disease scientists know a lot about how other microorganisms interact with plants and the environment to create an outbreak," says Buck. "This same knowledge can be applied to human pathogens as well. An exchange of research tools and experiences between plant pathologists and food microbiologists could result in tremendous advances towards managing food-borne diseases related to produce consumption."

According to Buck, one impediment to this kind of research, however, is that plant pathology laboratories currently lack the appropriate facilities for working with human pathogens, which are considered biosafety hazards. Until such changes can be made, says Buck, plant pathology models and practices, such as integrated pest management, that have worked well in controlling other plant diseases would likely work in helping to minimize the risk of human disease as well. Says Buck, "No doubt plant disease scientists can, and should, play a more significant role in food safety issues in the future."

The microbiological safety of fruits and vegetables is the subject of this month's APS feature story and can be found at APS website at: http://www.apsnet.org . The American Phytopathological Society (APS) is a non-profit, professional scientific organization dedicated to the study and control of plant disease with 5,000 members worldwide.

SOURCE : American Phytopathological Society

Spinal Cord Stem Cells Could Be Basis Of Nonsurgical Treatment For Spinal-cord Injuries

2008-07-24T15:26:00.002+07:00

A researcher at MIT's Picower Institute for Learning and Memory has pinpointed stem cells within the spinal cord that, if persuaded to differentiate into more healing cells and fewer scarring cells following an injury, may lead to a new, non-surgical treatment for debilitating spinal-cord injuries.

The work is by Konstantinos Meletis, a postdoctoral fellow at the Picower Institute, and colleagues at the Karolinska Institute in Sweden. Their results could lead to drugs that might restore some degree of mobility to the 30,000 people worldwide afflicted each year with spinal-cord injuries.

Coronal sections of injured adult spinal cord, anterior to posterior.
The labeling shows recombined ependymal cells and their progeny (white)
migrating out to the injury area in the dorsal funiculus,
as a response to the injury (injury is in the image on the right hand corner).
(Credit: Image / Konstantinos Meletis)

In a developing embryo, stem cells differentiate into all the specialized tissues of the body. In adults, stem cells act as a repair system, replenishing specialized cells, but also maintaining the normal turnover of regenerative organs such as blood, skin or intestinal tissues.

The tiny number of stem cells in the adult spinal cord proliferate slowly or rarely, and fail to promote regeneration on their own. But recent experiments show that these same cells, grown in the lab and returned to the injury site, can restore some function in paralyzed rodents and primates.

The researchers at MIT and the Karolinska Institute found that neural stem cells in the adult spinal cord are limited to a layer of cube- or column-shaped, cilia-covered cells called ependymal cells. These cells make up the thin membrane lining the inner-brain ventricles and the connecting central column of the spinal cord.

"We have been able to genetically mark this neural stem cell population and then follow their behavior," Meletis said. "We find that these cells proliferate upon spinal cord injury, migrate toward the injury site and differentiate over several months."

The study uncovers the molecular mechanism underlying the tantalizing results of the rodent and primate and goes one step further: By identifying for the first time where this subpopulation of cells is found, they pave a path toward manipulating them with drugs to boost their inborn ability to repair damaged nerve cells.

"The ependymal cells' ability to turn into several different cell types upon injury makes them very interesting from an intervention aspect: Imagine if we could regulate the behavior of this stem cell population to repair damaged nerve cells," Meletis said.

Upon injury, ependymal cells proliferate and migrate to the injured area, producing a mass of scar-forming cells, plus fewer cells called oligodendrocytes. The oligodendrocytes restore the myelin, or coating, on nerve cells' long, slender, electrical impulse-carrying projections called axons. Myelin is like the layer of plastic insulation on an electrical wire; without it, nerve cells don't function properly.

"The limited functional recovery typically associated with central nervous system injuries is in part due to the failure of severed axons to regrow and reconnect with their target cells in the peripheral nervous system that extends to our arms, hands, legs and feet," Meletis said. "The function of axons that remain intact after injury in humans is often compromised without insulating sheaths of myelin."

If scientists could genetically manipulate ependymal cells to produce more myelin and less scar tissue after a spinal cord injury, they could potentially avoid or reverse many of the debilitating effects of this type of injury, the researchers said.

This study was supported by grants from the Swedish Research Council, the Swedish Cancer Society, the Foundation for Strategic Research, the Karolinska Institute, EuroStemCell and the Christopher and Dana Reeve Foundation.

SOURCE : Massachusetts Institute of Technology

Brain Morphology Of Homo Liujiang Cranium Fossil Detailed With 3-D CT Scan

2008-07-24T12:17:00.000+07:00

High-resolution industrial computed tomography was used to scan the Homo Liujiang cranium fossil, and the three-dimensional virtual brain image was reconstructed. More information for the phyletic evaluation of the Homo Liujiang was derived from this new research.

Hominin fossils are the most important materials to explore human origins and evolution. Since most hominin fossils are incomplete, or filled with a heavy calcified matrix, it is difficult or often impossible to reconstruct the endocast in a real fossil without destroying it. Accordingly, traditional methods limited the study of human brain evolution.

CT can explore fossils in a noninvasive way by transforming a real fossil into a virtual object, and make it possible for paleoanthropologists to extend the study of fossil specimens from the exterior to the interior. Using high-resolution industrial CT, the Homo Liujiang brain image was reconstructed.

The Liujiang cranium is the most complete and well-preserved late Pleistocene human fossils ever unearthed in South China. Because the endocranial cavity is filled with hard stone matrix, earlier studies focused only on the exterior morphology of the specimen using the traditional methods. Arguments about the phyletic evaluation of the Liujiang hominin fossil have existed for a long time.

The new research was led by Wu Xiujie from Institute of Vertebrate Paleontology and Paleoanthropology (IVPP).

In this study, the authors used high-resolution industrial CT to scan the Liujiang cranium, and reconstruct the three-dimensional (3-D) brain image. Compared with the endocasts of the hominin fossils and modern Chinese, most morphological features of the Liujiang brain are in common with modern humans, including a round brain shape, bulged and wide frontal lobes, an enlarged brain height, a full orbital margin and long parietal lobes.

There are a few differences between Liujiang and the modern Chinese in our sample, including a strong posterior projection of the occipital lobes, and a reduced cerebellar lobe. The measurement of the virtual endocast shows that the endocranial capacity of Liujiang is 1567 cc, which is in the range of Late Homo sapiens and much beyond the mean of modern humans. The brain morphology of Liujiang is assigned to Late Homo sapiens.

IVPP is the only special institute mainly dealing with the research of origin and evolutionary history of hominin fossils. In the past 80 years, a few complete hominin crania fossila were found in China. "With CT scanning and 3D visualization techniques to reconstruct virtual specimens, it is now possible for Chinese hominin paleontologists to conduct paleoneurological studies of our national treasures", said Dr. Wu Xiujie.

The study is supported by the National Natural Science Foundation of China.

SOURCE : Science in China Press

Long-term Cannabis Users May Have Structural Brain Abnormalities

2008-07-24T09:57:00.000+07:00

Long-term, heavy cannabis use may be associated with structural abnormalities in areas of the brain known as the hippocampus and amygdala, according to a new article.

Conflicting evidence exists regarding the long-term effects of cannabis use, according to background information in the article. "Although growing literature suggests that long-term cannabis use is associated with a wide range of adverse health consequences, many people in the community, as well as cannabis users themselves, believe that cannabis is relatively harmless and should be legally available," the authors write. "With nearly 15 million Americans using cannabis in a given month, 3.4 million using cannabis daily for 12 months or more and 2.1 million commencing use every year, there is a clear need to conduct robust investigations that elucidate the long-term sequelae of long-term cannabis use."

Murat Yücel, Ph.D., M.A.P.S., of ORYGEN Research Centre and the Melbourne Neuropsychiatry Centre at the University of Melbourne, Australia, and colleagues from the University of Wollongong performed high-resolution structural magnetic resonance imaging on 15 men (average age 39.8 years) who smoked more than five joints daily for more than 10 years. Their results were then compared with images from 16 individuals (average age 36.4) who were not cannabis users. All participants also took a verbal memory test and were assessed for subthreshold (below the standard of disease diagnosis) symptoms of psychotic disorders, which include schizophrenia and mania.

The hippocampus, thought to regulate emotion and memory, and the amygdala, involved with fear and aggression, tended to be smaller in cannabis users than in controls (volume was reduced by an average of 12 percent in the hippocampus and 7.1 percent in the amygdala). Cannabis use also was associated with sub-threshold symptoms of psychotic disorders. "Although cannabis users performed significantly worse than controls on verbal learning, this did not correlate with regional brain volumes in either group," the authors write.

"There is ongoing controversy concerning the long-term effects of cannabis on the brain," the authors write. "These findings challenge the widespread perception of cannabis as having limited or no neuroanatomical sequelae. Although modest use may not lead to significant neurotoxic effects, these results suggest that heavy daily use might indeed be toxic to human brain tissue. Further prospective, longitudinal research is required to determine the degree and mechanisms of long-term cannabis-related harm and the time course of neuronal recovery after abstinence."

SOURCE : JAMA and Archives Journals

Lionfish Decimating Tropical Fish Populations, Threatening Coral Reefs

2008-07-23T21:14:00.000+07:00

The invasion of predatory lionfish in the Caribbean region poses yet another major threat there to coral reef ecosystems -- a new study has found that within a short period after the entry of lionfish into an area, the survival of other reef fishes is slashed by about 80 percent.

Aside from the rapid and immediate mortality of marine life, the loss of herbivorous fish also sets the stage for seaweeds to potentially overwhelm the coral reefs and disrupt the delicate ecological balance in which they exist, according to scientists from Oregon State University.

Following on the heels of overfishing, sediment depositions, nitrate pollution in some areas, coral bleaching caused by global warming, and increasing ocean acidity caused by carbon emissions, the lionfish invasion is a serious concern, said Mark Hixon, an OSU professor of zoology and expert on coral reef ecology.

The study is the first to quantify the severity of the crisis posed by this invasive species, which is native to the tropical Pacific and Indian Ocean and has few natural enemies to help control it in the Atlantic Ocean. It is believed that the first lionfish -- a beautiful fish with dramatic coloring and large, spiny fins -- were introduced into marine waters off Florida in the early 1990s from local aquariums or fish hobbyists. They have since spread across much of the Caribbean Sea and north along the United States coast as far as Rhode Island.

"This is a new and voracious predator on these coral reefs and it's undergoing a population explosion," Hixon said. "The threats to coral reefs all over the world were already extreme, and they now have to deal with this alien predator in the Atlantic. These fish eat many other species and they seem to eat constantly."

The lead author is Mark Albins, a doctoral student working with Hixon.

In studies on controlled plots, the OSU scientists determined that lionfish reduced young juvenile fish populations by 79 percent in only a five-week period. Many species were affected, including cardinalfish, parrotfish, damselfish and others. One large lionfish was observed consuming 20 small fish in a 30-minute period.

Lionfish are carnivores that can eat other fish up to two-thirds their own length, while they are protected from other predators by long, poisonous spines. In the Pacific Ocean, Hixon said, other fish have learned to avoid them and they also have more natural predators, particularly large groupers. In the Atlantic Ocean, native fish have never seen them before and have no recognition of danger. There, about the only thing that will eat lionfish is another lionfish -- they are not only aggressive carnivores, but also cannibals.

"In the Caribbean, few local predators eat lionfish, so there appears to be no natural controls on them," Hixon said. "And we've observed that they feed in a way that no Atlantic Ocean fish has ever encountered. Native fish literally don't know what hit them."

When attacking another fish, Hixon said, the lionfish will use its large, fan-like fins to herd smaller fish into a corner and then swallow them in a rapid strike. Because of their natural defense mechanisms they are afraid of almost no other marine life. And the poison released by their sharp spines can cause extremely painful stings to humans -- even leading to fatalities for some people with heart problems or allergic reactions.

"These are pretty scary fish, and they aren't timid," Hixon said. "They will swim right up to a diver in their feeding posture, looking like they're ready to eat. That can be a little spooky."

Their rapid reproduction potential, Hixon said, must now be understood in context with their ability to seriously depopulate coral reef ecosystems of other fish. Parrotfishes and other herbivores prevent seaweeds from smothering corals. A major, invasive predator such as lionfish could disrupt the entire system.

Options to manage the lionfish threat are limited, Hixon said. They can be collected individually, which may be of localized value, but that approach offers no broad solution. Recovery or introduction of effective predators might help. Groupers, a fish that has been known to eat lionfish in the Pacific Ocean, have been heavily over-fished in the tropical Atlantic Ocean, Hixon said.

"We have to figure out something to do about this invasion before it causes a major crisis," Hixon said. "We basically had to abandon some studies we had under way in the Atlantic on population dynamics of coral reef fish, because the lionfish had moved in and were eating everything."

OSU scientists say they hope to continue research on lionfish in their native Pacific Ocean habitats for information that may be of use in their control.

SOURCE : Oregon State University

New Population Of Highly Threatened Greater Bamboo Lemur Found In Madagascar

2008-07-23T14:49:00.001+07:00

Researchers in Madagascar have confirmed the existence of a population of greater bamboo lemurs more than 400 kilometers (240 miles) from the only other place where the Critically Endangered species is known to live, raising hopes for its survival.

The discovery of the distinctive lemurs with jaws powerful enough to crack giant bamboo, their favorite food, occurred in 2007 in the Torotorofotsy wetlands of east central Madagascar, which is designated a Ramsar site of international importance under the 1971 Convention on Wetlands.

Updated information on the species will be presented at the upcoming International Primatological Society 2008 Congress in Edinburgh, Scotland, on Aug. 3-8, as part of a new assessment of the world's primates that shows the state of mankind's closest living relatives.

For years, scientists believed but were unable to prove that greater bamboo lemurs (Prolemur simus) lived in the Torotorofotsy area. A collaborative effort between the Malagasy non-government organization MITSINJO and the Henry Doorly Zoo in the United States supported by the Margot Marsh Biodiversity Foundation and Conservation International (CI) resulted in researchers finding and immobilizing several to attach radio collars for further monitoring.

The researchers believe there are 30-40 greater bamboo lemurs in the Torotorofotsy wetland, which is far to the north of the isolated pockets of bamboo forest where the rest of the known populations of the species live. Habitat destruction from slash-and-burn agriculture and illegal logging threatens the previously known populations that total about 100 individuals, making the existence of the newly found lemurs in a distinct region especially valuable.

"This finding confirmed what we knew before but couldn't prove," said Rainer Dolch of MITSINJO, which manages the Torotorofotsy site. "Our hope is that the presence of these critically threatened creatures will increase efforts to protect their habitat and keep them alive."

"Finding the extremely rare Prolemur simus in a place where nobody expected it was probably more exciting than discovering a new lemur species," said conservation geneticist Edward Louis of Henry Doorly Zoo, who coordinated the joint research mission that found the new population.

The scientists will publish their discovery in Lemur News, the newsletter of the Primate Specialist Group of the IUCN Species Survival Commission.

"The greater bamboo lemur is a unique species and the only member of an entire primate genus, making it probably the most endangered primate genus in the world, so this discovery is a real blessing for our efforts to save it from extinction," said CI President Russell A. Mittermeier, the long-time chairman of the Primate Specialist Group. "It also shows the importance for conservation of collaboration between local villagers, local organizations such as MITSINJO and international groups like the Henry Doorly Zoo."

SOURCE : Conservation International

Why Cannabis Stems Inflammation

2008-07-23T09:37:00.000+07:00

Cannabis has long been accredited with anti-inflammatory properties. ETH Zurich researchers, however, have now discovered that it is not only the familiar psychoactive substances that are responsible for this; a compound we take in every day in vegetable nutriment also plays a significant role.

People not only rate cannabis sativa L. highly because of its intoxicating effects; it has also long been used as a medicinal plant. Although the plant has been scrutinized for years, surprising new aspects keep cropping up. For example, researchers from ETH Zurich and Bonn University examined a component in the plant’s essential oil that until then had largely been ignored and found it to have remarkable phar- macological effects. The findings open up interesting perspectives, especially for the prevention and treatment of inflammations.

Completely different molecule structure

The hemp plant contains over 450 different substances, only three of which are responsible for its intoxicating effect. They activate the two receptors in the body CB1 and CB2. Whilst the CB1 receptor in the central nervous system influences perception, the CB2 receptor in the tissue plays a crucial role in inhibiting inflammation. If the receptor is activated, the cell releases fewer pro-inflammatory signal substances, or cytokines. The scientists have now discovered that the substance beta-carophyllene, which composes between 12 and 35 percent of the cannabis plant’s essential oil, activates the CB2 receptor selectively.

Unlike the three psychoactive substances, however, beta-carophyllene does not latch onto the CB1 receptor and consequently does not trigger the intoxicating effect. “Due to the various effects of cannabis, we had suspected for quite some time that other substances could come into play besides the psychoactive ones”, explains Jürg Gertsch from the Institute of Pharmaceutical Sciences at ETH Zurich. “However, astonishingly we didn’t know what substances these were until now.”

Gertsch finds it remarkable that beta-carophyllene has a very different molecule structure to that of the classical cannabinoids. “This is presumably why no one realized that the substance can also activate the CB2 receptor.” The scientists were not only able to prove that beta-carophyllene binds with the CB2 receptor in vitro but also in animal tests, where they treated mice that were suffering from an inflammatory swelling on their paws with orally administered doses of the substance. The swelling declined in up to 70 percent of the animals, even for deep doses. For mice lacking the gene for the CB2 receptor, however, the substance did not make an impact.

Common substance

The results are encouraging for the prevention or treatment of ailments in which the CB2 receptor plays a positive role. However, Gertsch explains that we are still very much in the early stages on that score. That said, the scientist can conceive that some day the compound will not only help heal certain forms of inflammation, but also be instrumental in treating chronic illnesses, such as liver cirrhosis, Morbus Crohn, osteoarthritis and arteriosclerosis. In all of these diseases, the CB2 receptor and the associated endocannabinoid system play a crucial role.

The beauty is that beta-carophyllene is not only found in cannabis but also often in plants as a whole and we consume the substance in our diet. The non-toxic compound, which incidentally has been used as a food additive for many years, can be found in spice plants like oregano, basil, cinnamon and black pepper. “Whether we have found a new link between the vegetable diet and the prevention of so-called lifestyle diseases in our study remains to be seen in future studies”, adds Gertsch.

SOURCE : ETH Zurich/Swiss Federal Institute of Technology

Animal Parenting, Personality And Pair-ups

2008-07-22T21:30:00.000+07:00

Parenting. Establishing life partnerships. Getting to know someone else's personality. These experiences feel profoundly human, but they have more in common with the animal world than one might think, researchers said today at the 2005 Annual Meeting of the American Association for the Advancement of Science (AAAS).

Animal lovers may not be surprised by this news.

"I get the most skepticism from scientists," said Samuel Gosling of the University of Texas, Austin. "It's really the human behavior researchers who object most."

Gosling and his colleagues have determined that dogs and hyenas have clear personality traits that can be measured like they are in humans. The researchers have studied characteristics such as fearfulness and anxiety, curiosity, and sociability.

"Personality is not just unique to humans," Gosling said.

Personality measurements have implications for animal welfare, for example when dogs are matched with owners or selected for various types of work. This information should also allow researchers to explore the various biological, genetic and environmental causes for an individual animal's temperament.

But, all traits do not appear in all species. Conscientiousness and dependability are only present in chimps and humans, according to Gosling.

Some of the parenting behaviors by monkey also resemble human parenting, Dario Maestripieri of the University of Chicago said. In his research on the development of maternal responsiveness he has found that both young girls and young female rhesus monkeys actively seek out opportunities to interact with infants, which males are much less inclined to do.

"It's a way to acquire parenting skills," Maestripieri said.

Many studies have shown that early social stress can accelerate puberty in girls, Maestripieri said. "We have now shown that early stress can also accelerate the development of maternal responsiveness in both humans and monkeys," he said. Adolescent girls who grow up without a father at home reach puberty earlier and are more attracted to pictures of infants than girls who have a father at home, Maestripieri and his colleagues recently reported in Developmental Science.

Female rhesus monkeys exposed to harsh and unpredictable maternal care in infancy also showed earlier interest in infants as well as higher levels of stress hormones during development, Maestripieri said. These findings are due to be published in Proceedings B, a journal of the Royal Society.

When it comes to the tiny tamarin and marmoset monkeys, some females behave in ways that don't translate so directly to humans.

The socially subordinate female monkeys in these groups become infertile in response to social interactions with a dominant female, according to Wendy Saltzman of the University of California, Riverside. Instead of breeding, these females help to rear the dominant females' infants. Researchers think this hormonally-mediated change benefits the subordinate females, because even though these monkeys will not be passing along their own genes, they will be helping to rear closely related infants.

When subordinate females do breed, their infants are likely to be killed by the dominant female, Saltzman and her colleagues have found more recently. So, by switching off their fertility, subordinate females may avoid investing in infants that aren't likely to survive.

These monkeys have very specialized social structures that aren't common in humans, Saltzman explained.

"But, in humans too, there can be social influences on reproductive physiology. The exact phenomenon of social suppression of fertility doesn't map onto humans but can help us understand how human fertility can be influenced by social and psychological factors," she said.

Curiously, reproductive suppression doesn't seem to involve stress or aggression between the females, according to Saltzman.

In the case of small rodents called voles, researchers have delved deeper into the biological mechanisms underlying the animals' mating behavior. Prairie voles mate for life, while a closely related species, the meadow mole, is promiscuous.

The difference seems to be that the receptors for a hormone called vasopressin are concentrated in different brain areas for each species, according to Larry Young of Emory University. Young and his colleagues have found that the receptors are located in the same areas involved in reward and addiction in the monogamous voles, but they're not present there in other vole species.

The researchers have also determined that the location of the receptors is determined by a single gene, which contains stretches of extra DNA in the monogamous voles but not in the promiscuous ones. Similar variations in this gene have also been found in humans.

"Other studies have found associations between this genetic variability and autism, which is a disease that affects social bonding and behavior. So, there's an interesting question there," Young said.

SOURCE : American Association For The Advancement Of Science

Female Monkeys More Dominant In Groups With Relatively More Males

2008-07-22T19:37:00.003+07:00

Female monkeys are more dominant when they live in groups with a higher percentage of males. This is caused by self-organisation. This surprising discovery was made by researchers at the University of Groningen. What makes the study particularly interesting is that the researchers used a computer model which can simulate interaction between monkeys.

Ring-tailed lemurs. Unlike most monkey species,
among the lemurs of Madagascar the females are dominant.
(Credit: iStockphoto/Dawn Nichols)

Many animals living in groups have a social hierarchy, a so-called 'pecking order'. Monkeys, too, have a social hierarchy. Highest in the pecking order is the most dominant monkey, who consistently wins aggressive interactions (such as biting) with other group members. At the bottom of the hierarchy is the lowest-ranking monkey, who consistently loses interactions with other members of the group. Monkeys have to fight for their place in this hierarchy every day.

Simulation

The position of females in the hierarchy varies among different monkey species. In most species females are ranking below the males. This is no wonder, because they are usually much smaller than males. However, in the case of the Lemur species of Madagascar the females are dominant, in bonobos, males and females roughly equal each other in dominance, and among a lot of other species (macaques and the grivet, for instance) females are weakly dominant.

"This means that the most dominant females rank above approximately a third of the males," says Charlotte Hemelrijk, theoretical biologist at the University of Groningen and the first author of the article (which she wrote together with her former PhD student, Dr. Jan Wantia and a Swiss anthropologist, Dr. Karin Isler).

Until now, it was unknown how this female dominance develops. Researchers in Groningen therefore created a virtual world, Domworld, with which they could simulate the interactions between monkeys.

Large amount of literature

Surprisingly, the computer model predicted females to be more dominant in a group with a relatively large number of males. To verify this prediction, the researchers analyzed data of aggression of a large amount of literature in which primate behaviour is described in order to calculate for the first timefemale-dominance among many different groups and monkey species. Their analysis showed the predictions of the computer model to be accurate. "This is an interesting way of conducting research," says Hemelrijk. "You discover something unexpected in the virtual world and then you test your findings in the real world."

Inborn or self-organisation?

So why are females more dominant in groups with a higher percentage of males? Two competing theories about the development of dominance exist, explains Hemelrijk. "According to the first theory, dominance is inborn. A monkey with good genes is bigger and will therefore win aggressive interactions more easily. The second theory states that dominance develops through self-organisation. An individual monkey wins an aggressive interaction by chance. As a consequence, the monkey's self-confidence grows and it also wins other aggressive interactions. It's a self-reinforcing effect," says Hemelrijk.

More complex than thought

If the first theory were correct, one would expect dominant females to be relatively bigger in size compared to male members of their species than less dominant females of other species. The researchers found this not to be the case. Instead, the second theory turns out to perfectly explain female dominance, as the relation between female dominance and the percentage of males can only be found among monkey species living in groups with aggressive behaviour that is sufficiently intense and frequent.

"Male aggression is more intense than that of females. In groups with more males, males are more often defeated by other males. Consequently, high-ranking females may be victorious over these losers. Furthermore, the presence of more males in the group leads to more interactions between males and females, causing more chance winnings by females. Through a self-reinforcing effect, these females will go on to win more frequently in later interactions and grow more dominant," says Hemelrijk.

According to the researcher, the study casts new light on monkeys. "The assumption was always that the degree of female dominance over males -or male dominance over females- was static, but it turns out to be much more dynamic and complex than expected." Dominance also plays a factor of importance in human interaction, says Hemelrijk. "It would not surprise me if self-organisation would prove to play a role in the development of dominance between the sexes among human beings too."

SOURCE : Public Library of Science

Scientists Integrate Data In Three Dimensions To Study Climate Effects On Young Fish

2008-07-17T01:36:00.000+07:00

From the surface, the two areas of ocean off the coasts of northern New Jersey and Long Island, New York look the same. But to NOAA scientists, the four-square-mile patches could not be more different as they view real-time underwater images and environmental data to try to figure out what lives there and how climate change is affecting marine life, especially very young fish.

“These areas are much more dynamic than terrestrial landscapes and not what we are used to thinking about the ocean,” said John Manderson, a fishery biologist with NOAA’s Northeast Fisheries Science Center (NEFSC) at the James J. Howard Marine Sciences Laboratory in Sandy Hook, N.J. “People look at the ocean floor as the habitat, but don’t think about the connection with the water column above it and how ocean fronts, like atmospheric weather, move through to create a constantly changing environment that affects fish and other marine life. It is a seascape, a moving 3-D environment.”

Manderson and colleagues in the NEFSC’s Behavioral Ecology Branch recently completed their first two-week cruise to the study area for the 2008 Ecology of Coastal Ocean Seascapes (ECOS) project. Another two-week cruise will be conducted in July, a third in September. There were some scientific surprises on the first cruise, and an unexpected event. On June 9, near the end of the first cruise, they rescued three teenagers from a swamped boat (see rescue story at end of article).

The goal of ECOS is to view the two seascapes in an integrated way using real-time data, focusing on the distribution and condition of early life stages of fishes, and develop models to aid fisheries research and management. For example, the models could ultimately be used to support fisheries managers to make informed decisions regarding the importance of habitat type for managed fish species, and to help answer questions about effects of climate change on the success of fish stocks.

One ECOS study site is south of the Hudson – Raritan River estuary and plume, the other about 20 kilometers (12 miles) north and east off Long Island. The scientists aboard the NEFSC’s 50-foot research vessel Nauvoo for the first cruise were surprised by what they saw, especially the differences in bottom life in study areas just a few miles apart with similar bottom structure.

“Based on side-scan sonar data and other information, we selected two study areas that had similar sandy bottoms because we were towing a video camera close to the seafloor,” Manderson said. “You would think they would look similar on video because they were not far apart, but what we found was more temperate marine life species like fluke, anchovies and sea robins off New Jersey, and scallops, squid egg mops and winter flounder more typical of New England off Long Island. The differences in the two seascapes were striking.”

Technology has been a huge help to the ECOS project. The Nauvoo is equipped with side-scan sonar, fisheries hydroacoustics, a Wi-Fi link to shore that receives real-time satellite and high-frequency radar imagery of data collected by a regional ocean observing system, GPS, an underwater video camera, and environmental sensors that measure water temperature, salinity and other conditions.

Each day during the two-week cruises, the team of six scientists and ship’s crew head out from the Atlantic Highlands Marina to the study sites, approximately 5 to 10 miles offshore. Working in depths up to 60 meters (about 100 feet), they use the various real-time data they receive from above and below the surface to develop a track line or sampling route of the ocean floor within their study areas. They tow a small video camera sled, stop at stations along the track to sample from the surface to the seafloor with a CTD (conductivity, temperature, density) recorder, and collect other environmental data. A beam trawl is used to collect specimens and to groundtruth the video imagery. Tissue and diet samples are collected from the animals and brought back to the laboratory.

“Right now we are characterizing the living marine resources and their habitats. We’re mainly interested in how the early life histories of fish effect the survival and productivity of the commercially and recreationally important species of our region,” Manderson said. “We hope to expand the studies to examine habitat effects on growth and mortality and the reproduction of adults. We will also be developing integrated laboratory and field experiments, allowing us to model distribution of species, recruitment of year classes, and other useful information.”

Manderson says the ECOS project, funded by NOAA, is a step forward in coastal fisheries research because they are looking at fish habitats holistically and dynamically in areas close to shore that have not been well studied.

“We’re using a variety of real and near real-time data that integrate information and present a three-dimensional view of the environment,” he said. “We’re able to move with a moving ocean, sampling with advanced technology and seeing it as it happens so we can adjust our sampling strategies as necessary. It is exciting to think of the possibilities.”

SOURCE : NOAA National Marine Fisheries Service

Big Brains Arose Twice In Higher Primates

2008-07-15T22:49:00.000+07:00

After taking a fresh look at an old fossil, John Flynn, Frick Curator of Paleontology at the American Museum of Natural History, and colleagues determined that the brains of the ancestors of modern Neotropical primates were as small as those of their early fossil simian counterparts in the Old World. This means one of the hallmarks of primate biology, increased brain size, arose independently in isolated groups--the platyrrhines of the Americas and the catarrhines of Africa and Eurasia.

Fossil Chilecebus from South America.
(Credit: John Weinstein, The Field Museum)

"Primatologists have long suspected that increased encephalization may have arisen at different points in the primate evolutionary tree, but this is the first clear demonstration of independent brain size increase in New and Old World anthropoids," says Flynn of the paper that appeared in the Museum's publication Novitates this June. Encephalization is the increase in brain size relative to body size. Animals with large encephalization quotients (E.Q.'s) are those with bigger brains relative to their body size in comparison to the average for an entire group. Most primates and dolphins have high E.Q.'s relative to other mammals, although some primates (especially apes and humans) have higher E.Q.'s than others.

At the heart of the new paper is the development of more accurate equations for estimating body size in platyrrhines, or New World "monkeys." Most fossils are fragments of skulls or teeth so, to help in estimating their body size (and then E.Q.), Flynn and colleagues collected 80 measurements of the skulls, jaws, and teeth of 17 different species of living New World monkeys that ranged across the full spectrum of body sizes. This study is one of the first to estimate body size with platyrrhines instead of their better-studied counterparts from the Old World, and this detailed analysis uses new statistical approaches to tease out which characteristics correlate best with body size. The goal is to apply this equation to fossilized specimens.

Chilecebus, found high in the Andes and described by Flynn and collaborators in 1995 in Nature, is one such fossil. The skull dates to 20 million years ago and is the oldest and most complete well-dated primate skull from the New World. In the Novitates paper, Flynn and colleagues more accurately estimate that Chilecebus weighed about 583 grams and had an E.Q. of only 1.11--a much smaller relative brain size than any living New or Old World anthropoid, which have E.Q.'s ranging from 1.39-2.44 (and even higher for humans).

"The result is clear: early fossil members of both the New World and Old World anthropoid lineages had small brain sizes, thus the larger brain sizes seen in both groups today must have arisen independently," says Flynn. "Documenting that large brains evolved separately several times within Primates will enhance understanding of the timing and pathways of brain expansion and its effects on skull growth and shape, and may lead to new insights into the genetic controls on encephalization."

Eric Delson, the Chair of Anthropology at Lehman College, City University of New York and a Research Associate at the Museum, concurs. "This work confirms that brain size increase may be one of the common characteristics of all primates," he says. "The relatively small brain of Chilecebus contrasts with that of the slightly younger (16.5 million years ago), larger brained fossil Killikaike found in Argentina and described two years ago. It is probable that brain size also increased independently in the lemurs of Madagascar, as well as in the apes (of which humans are the extreme case) and the cercopithecid monkeys of Africa and Asia."

Other researchers on the study include lead author Karen E. Sears of the Department of Animal Biology at The University of Illinois at Urbana-Champaign, John A. Finarelli of the Department of Geological Sciences at the University of Michigan, and Andre R. Wyss of the Department of Geological Sciences at the University of California at Santa Barbara. This research was supported by the National Science Foundation, the John S. Guggenheim Memorial Foundation, and fellowships from The Field Museum, the University of Chicago and the University of Michigan.

SOURCE : American Museum of Natural History

Insects Use Plants Like A Telephone

2008-07-15T01:15:00.000+07:00

Dutch ecologist Roxina Soler and her colleagues have discovered that subterranean and aboveground herbivorous insects can communicate with each other by using plants as telephones. Subterranean insects issue chemical warning signals via the leaves of the plant. This way, aboveground insects are alerted that the plant is already ‘occupied’.

llustration of communication between subterranean and aboveground herbivorous insects.
(Credit: Image courtesy of Netherlands Organization for Scientific Research)

Aboveground, leaf-eating insects prefer plants that have not yet been occupied by subterranean root-eating insects. Subterranean insects emit chemical signals via the leaves of the plant, which warn the aboveground insects about their presence. This messaging enables spatially-separated insects to avoid each other, so that they do not unintentionally compete for the same plant.

In recent years it has been discovered that different types of aboveground insects develop slowly if they feed on plants that also have subterranean residents and vice versa. It seems that a mechanism has developed via natural selection, which enables the subterranean and aboveground insects to detect each other. This avoids unnecessary competition.

Green telephone lines

Via the 'green telephone lines', subterranean insects can also communicate with a third party, namely the natural enemy of caterpillars. Parasitic wasps lay their eggs inside aboveground insects. The wasps also benefit from the volatile signals emitted by the leaves, as these reveal where they can find a good host for their eggs. The communication between subterranean and aboveground insects has only been studied in a few systems. It is still not clear how widespread this phenomenon is.

This research was carried out at the Netherlands Institute for Ecology (NIOO-KNAW) by Roxina Soler, Jeffrey Harvey, Martijn Bezemer, Wim van der Putten and Louise Vet. The PhD project, in which this study was carried out, was funded by the Free Competition of NWO Earth and Life Sciences.

SOURCE : Netherlands Organization for Scientific Research

Caribbean Corals In Danger Of Extinction: Climate Change, Warmer Waters Cited As Leading Cause

2008-07-14T12:49:00.000+07:00

Caribbean coral species are dying off, indicating dramatic shifts in the ecological balance under the sea, a new scientific study of Caribbean marine life shows.

The study found that 10 percent of the Caribbean's 62 reef-building corals were under threat, including staghorn and elkhorn corals. These used to be the most prominent species but are now candidates to be listed as Critically Endangered on the IUCN Red List of Threatened Species.

"One of the Atlantic Ocean's most beautiful marine habitats no longer exists in many places because of dramatic increases in coral diseases, mostly caused by climate change and warmer waters," said Dr. Michael L. Smith, director of the Caribbean Biodiversity Initiative at Conservation International.

A gathering of 23 scientists in Dominica in March 2007 analyzed data on Western Tropical Atlantic corals, seagrasses, mangroves and algae, which are fundamental components of marine ecosystems providing food and shelter for numerous other organisms and local communities. The study was funded in part by the Royal Caribbean Cruises' Ocean Fund.

This was the first in a series of Global Marine Species Assessments (GMSA) of key marine primary-producers on a global scale. The GMSA is headquartered at Old Dominion University in Norfolk, Virginia, USA, and is a partnership between Conservation International (CI) and the World Conservation Union (IUCN). It aims to dramatically increase the number of marine species assessed under the rigorous criteria of the IUCN Red List of Threatened Species to provide up-to-date information for marine policy and conservation efforts.

After a final review, the species assessed during the Dominica workshop will be added to the 2008 IUCN Red List.

"Coral reefs support some of the richest areas of biodiversity in the world. When the coral reefs disappear, so will many other species which rely on reefs for shelter, reproduction and foraging," said Dr. Suzanne Livingstone, GMSA program officer.

The threats to corals and other marine species include coastal pollution and human development; increased sedimentation in run-off water; thermal stress and heightened severity of hurricanes from climate change; and shifts in species dynamics due to over-fishing, according to the study. Scientists explained that the Caribbean has undergone the longest and most sustained impacts from human development since the colonization of the Americas.

Next to corals, mangroves appear to be the hardest hit. Mangrove cover in the region has declined by 42% over the past 25 years, with two of the eight mangrove species now considered Vulnerable to extinction and two more in Near Threatened status.

"Mangroves protect shorelines, shelter fish, and filter pollution," said Aaron Ellison of Harvard University. "The Caribbean was blessed with an abundance of these useful plants, but the consensus of this workshop is that mangroves are in trouble everywhere and need to be protected and restored," he added. Mangrove forests are being cut down to make way for coastal housing, tourism, and aquaculture development.

Beds of sea-grasses in shallow coastal waters, like mangroves, provide a vital nursery habitat for fish, including many commercially important species and are subject to similar threats. They are in equal need of protection to safeguard the wealth of marine life they support.

Unlike corals, seagrasses and mangroves, Caribbean algae appear to be surviving well and perhaps are taking advantage of the corals' demise. Algae thrive on dead or dying coral reefs and can overgrow and smother newly settled corals. In addition, the fishes that feed on algae are being overexploited and their reduced populations enable algae to form dense growths that prevent corals from re-colonizing.

The scientists noted that some healthy Caribbean coral reefs still exist in well-managed marine protected areas such as Bonaire Marine Park in the Netherlands Antilles. Direct human impacts are reduced in these areas allowing most corals to thrive; however, thermal stress from global warming affects all corals in the Caribbean and must be reversed if these refuges of Caribbean beauty are to survive, they added.

"The Caribbean tourism industry relies heavily on the beauty and health of its sea life," said Dr. Kent Carpenter, GMSA Director. "Concentrated marine conservation and a global effort to halt man-induced climate change are necessary to preserve this vital economic engine in the region."

SOURCE : Conservation International

Distribution Of A Species Of Butterfly Predicted Using Geometric Variables

2008-07-14T02:39:00.005+07:00

Biologists have recently explored the distribution of the butterfly Iolana iolas, one of the endangered species in the Madrid region whose population dynamics are determined by its host plant. The study, prepared by scientists from the King Juan Carlos University in Madrid, proposes a new path for designing conservation plans for the species using geometric variables.

The research has made it possible to determine the relative importance of the area which the butterfly Iolana iolas inhabits, as well as the connectivity between the different areas of the habitat (at a maximum distance of two kilometres from each other) in a network of 75 patches (population centres) situated in the south of the province of Madrid (Chinchón). Three researchers from the King Juan Carlos University in Madrid have presented the line of study on the spatial structure and dynamics of the butterfly different to other quality characteristics in the habitat.

The results of the study, prepared between 2003 and 2006, show that in the Iolana iolas and other species of monophagous butterflies (with clearly delimited habitat requirements), it is possible to predict the dynamics of their populations from the geometric variables of patches, “since most of the characteristics of the habitat are related to the patch area”, explained Sonia García Rabasa, the main author of the article, to SINC.

Researchers have concentrated on factors that determine the distribution, extinction and density of Iolana iolas populations in relation to the habitat patches formed by an endemic plant of the Iberian Peninsular, and host to butterflies, the Colutea hispanica (leguminous plant).

“The study may be of major importance for designing conservation plans for the species, and shows the relevance of geometric characteristics compared to other habitat quality properties which are frequently more difficult to achieve in field conditions”, commented the researcher.

To predict the distribution patterns it has also been important to study the synchrony between populations: “The spatial study and population dynamics of butterflies may also affect the incidence and probability of the extinction of the species”, García Rabasa pointed out.

Study of population dynamics

The fragmentation or division of the species’ habitat areas is one of the main causes of the decline of the fauna and flora, as it produces an increase in local extinctions and a reduction in recolonisation rates. Knowing the situation of the Iolana iolas, which depends on plant extension for survival, scientists have shown the effects of the characteristics of the habitat (topographic factors, microclimate, amount of resources) and the standard geometric measurements (area and connectivity) of the patches.

During the four years of the study, “the extinction, density and occupation rate of butterflies in different areas was purely determined by their size, without affecting the remoteness between the areas or the quality measurements of the habitat”, added the researcher.

Consequently, the scientists only recorded nine extinctions in nine different patches and 15 colonisations in 13 patches over four years. According to the study, all the extinctions were linked to patches or areas with a low or poor production of fruit which would “inevitably” lead to a failure in the local recruitment of butterflies.

As a result, the smallest habitat patches had lower butterfly population sizes and higher rates of extinction, irrespective of their quality of habitat. The population sizes were small, with only tens of individuals in the “best” years, and were even smaller in smaller patches, with fewer than ten individuals.

Variation in the amount of resources, in this case the production of fruit from the host plant (Colutea hispanica), from which the larvae feed, and changes in population density during these years have made it possible to detect a high level of synchrony between different habitat fragments. This high level of synchrony is a risk to populations which might experience mass extinction in all areas experiencing adverse conditions, such as the effects of climate change.

SOURCE : Plataforma SINC

One-third Of Reef-building Corals Face Extinction

2008-07-14T00:08:00.000+07:00

A third of reef-building corals around the world are threatened with extinction, according to the first-ever comprehensive global assessment to determine their conservation status. The study findings were published today by Science Express.

Leading coral experts joined forces with the Global Marine Species Assessment (GMSA) -- a joint initiative of the International Union for Conservation of Nature (IUCN) and Conservation International (CI) -- to apply the IUCN Red List Categories and Criteria to this important group of marine species.

"The results of this study are very disconcerting," stated Kent Carpenter, lead author of the Science article, GMSA Director, IUCN Species Programme. "When corals die off, so do the other plants and animals that depend on coral reefs for food and shelter, and this can lead to the collapse of entire ecosystems."

Built over millions of years, coral reefs are home to more than 25 percent of marine species, making them the most biologically diverse of marine ecosystems. Corals produce reefs in shallow tropical and sub-tropical seas and have been shown to be highly sensitive to changes in their environment.

Researchers identified the main threats to corals as climate change and localized stresses resulting from destructive fishing, declining water quality from pollution, and the degradation of coastal habitats. Climate change causes rising water temperatures and more intense solar radiation, which lead to coral bleaching and disease often resulting in mass coral mortality.

Shallow water corals have a symbiotic relationship with algae called zooxanthellae, which live in their soft tissues and provide the coral with essential nutrients and energy from photosynthesis and are the reason why corals have such beautiful colors. Coral bleaching is the result of a stress response, such as increased water temperatures, whereby the algae are expelled from the tissues, hence the term "bleaching." Corals that have been bleached are weaker and more prone to attack from disease. Scientists believe that increased coral disease also is linked to higher sea temperatures and an increase in run-off pollution and sediments from the land.

Researchers predict that ocean acidification will be another serious threat facing coral reefs. As oceans absorb increasing amounts of carbon dioxide from the atmosphere, water acidity increases and pH decreases, severely impacting corals' ability to build their skeletons that form the foundation of reefs.

The 39 scientists who co-authored this study agree that if rising sea surface temperatures continue to cause increased frequency of bleaching and disease events, many corals may not have enough time to replenish themselves and this could lead to extinctions.

"These results show that as a group, reef-building corals are more at risk of extinction than all terrestrial groups, apart from amphibians, and are the most vulnerable to the effects of climate change," said Roger McManus, CI's vice president for marine programs. "The loss of the corals will have profound implications for millions of people who depend on coral reefs for their livelihoods."

Coral reefs harbor fish and other marine resources important for coastal communities. They also help protect coastal towns and other near-shore habitats from severe erosion and flooding caused by tropical storms.

Staghorn (Acroporid) corals face the highest risk of extinction, with 52 percent of species listed in a threatened category. The Caribbean region has the highest number of highly threatened corals (Endangered and Critically Endangered), including the iconic elkhorn coral (Acropora palmata) which is listed as Critically Endangered. The high biodiversity "Coral Triangle" in the western Pacific's Indo-Malay-Philippine Archipelago has the highest proportions of Vulnerable and Near-Threatened species in the Indo-Pacific, largely resulting from the high concentration of people living in many parts of the region.

Corals from the genera Favia and Porites were found to be the least threatened due to their relatively higher resistance to bleaching and disease. In addition, 141 species lacked sufficient information to be fully assessed and were therefore listed as Data Deficient. However, researchers believe that many of these species would have been listed as threatened if more information were available.

The results emphasize the widespread plight of coral reefs and the urgent need to enact conservation measures. "We either reduce our CO2 emission now or many corals will be lost forever," says Julia Marton-Lefèvre, IUCN Director General. "Improving water quality, global education and the adequate funding of local conservation practices also are essential to protect the foundation of beautiful and valuable coral reef ecosystems."

Coral experts participated in three workshops to analyze data on 845 reef-building coral species, including population range and size, life history traits, susceptibility to threats, and estimates of regional coral cover loss.

The reef-building corals assessment is one group of a number of strategic global assessments of marine species the GMSA has been conducting since 2006 at Old Dominion University in Norfolk, Virginia. Other assessments are being conducted on seagrasses and mangroves that are also important habitat-forming species, all marine fishes, and other important keystone invertebrates. By 2012, the GMSA plans to complete its comprehensive first stage assessment of the threat of extinction for over 20,000 marine plants and animals, providing an essential baseline for conservation plans around the world, and tracking the extinction risk of marine species.

The results of the coral species assessment will be placed on the IUCN Red List of Threatened Species in October 2008. Currently, the assessments can be found at http://www.sci.odu.edu/gmsa/about/corals.shtml.

SOURCE : Conservation International

Insect Warning Colors Aid Cancer And Tropical Disease Drug Discovery

2008-07-13T23:50:00.002+07:00

Brightly colored beetles or butterfly larvae nibbling on a plant may signal the presence of chemical compounds active against cancer cell lines and tropical parasitic diseases, according to researchers at Smithsonian's Tropical Research Institute in Panama. Such clues could speed drug discovery and provide insight into the ecological relationships between tropical-forest plants and insects that feed on them.

"These findings are incredibly exciting and important," said Todd Capson, STRI research chemist, who directed the project. "The results of this study could have direct and positive impacts on the future of medical treatment for many diseases around the world."

For this research scientists used plants already known to have anti-cancer compounds; those proven to be active against certain disease-carrying parasites; and plants without such activity. The study showed that beetles and butterfly larvae with bright warning coloration were significantly more common on plants that contained compounds active against certain diseases, such as breast cancer and malaria. There was no significant difference in the number of plain-colored insects between plants with and without activity, according to the study by the Smithsonian's Panama International Cooperative Biodiversity Group Program.

"We put two and two together," said researcher Julie Helson. "We knew that brightly colored insects advertise to their predators that they taste bad and that some get their toxins from their host plants. But because other insects cheat by mimicking the toxic ones, we weren't sure if insect color was really going to work to identify plants containing toxins--it did!" Helson was a student at McGill University when she conducted this research in 2005.

The Smithsonian's PICBG program first demonstrated that theories about chemical defense in rainforest plants--such as the idea that young leaves tend to be richer in defense chemicals--can significantly improve the efficiency and lower the cost of drug discovery, when compared with a random screening approach.

Although the idea that brightly colored insects could facilitate the search for medicinally active plants has been discussed for decades, the concept had never been rigorously tested. This new work at the Smithsonian provides another example of how ecology can contribute to the discovery of novel medicines. The study suggests that a quick screen for insects with warning coloration on tropical plants may increase the efficiency of the search for compounds active against cancer and tropical parasitic disease by four-fold. "It's very gratifying to see that it works in the field." said Capson. "I am hopeful that other investigators will follow our lead and test our theory that insects can lead us to plants with disease-fighting properties."

This work also demonstrates that protecting tropical forests¯not just the insects and plants, but at every level--has the potential to provide immeasurable benefits to human health.

The authors thank staff at Panama's Institute of Advanced Scientific Research and High Technology Services, Panama's National Authority of the Environment and the University of Panama.

Funding for the study was provided by the U.S. National Institutes of Health, the U.S. National Science Foundation, the U.S. Department of Agriculture through the International Cooperative Biodiversity Groups program, grant numbers 1U01 TW01021-01 and 1U01 TW006634-01, the National Science and Engineering Research Council of Canada and a Levinson Fellowship from the STRI-McGill NEO program.

SOURCE : Smithsonian Tropical Research Institute

Outdoor Enthusiasts Scaring Off Native Carnivores In Parks

2008-07-01T18:24:00.000+07:00

Even a quiet stroll in the park can dramatically change natural ecosystems, according to a new study by conservation biologists from the University of California, Berkeley. These findings could have important implications for land management policies.

Coyote in the wild, in California.
Even a quiet stroll in the park can dramatically change natural ecosystems.
(Credit: iStockphoto/Graeme Purdy)

The study compared parks in the San Francisco Bay Area that allow only quiet recreation such as hiking or dog walking with nearby nature reserves that allow no public access. Evidence of some native carnivore populations - coyote and bobcat - was more than five times lower in parks that allow public access than in neighboring reserves where humans don't tread, the researchers report.

The dearth of these animals in the parks carries implications beyond just these species. Since the carnivores in the study are often the top predators in their areas, these animals also shape the rest of their surrounding ecosystems. The flight of large animals from heavily visited parks for more serene surroundings could, in turn, influence populations of small animals and plants, the researchers said.

"Carnivores are sensitive indicators of human disturbance," said Sarah Reed, postdoctoral scholar in UC Berkeley's Department of Environmental Science, Policy and Management and the study's lead author. "Their presence or absence can be a good, early clue to how the ecosystem is doing."

To measure carnivore numbers, Reed studied the droppings of six native and non-native mammalian carnivores in 28 parks and preserves in northern California. The parks in her study allow public access, but don't allow motorized vehicles or hunting and fishing. Most visitors to these parks hike or walk their dogs, Reed said. The preserves in the study have limited or no public access.

Reed found more than five times as much coyote and bobcat scat in preserves with no public access than she did in the parks. Coyotes and bobcats are both native carnivores. She also found more scat from the native gray fox and the non-native red fox in unvisited areas, and more dog and cat droppings in visited parks.

Reed said she did not expect these findings. She and many other conservation biologists assumed that activities such as hiking or horseback riding were relatively benign, she said. "I was surprised that the difference was so dramatic," Reed said.

Adina Merenlender, cooperative extension specialist in the Department of Environmental Science, Policy and Management and senior author on the study, said the findings "are probably the most surprising results that have come out of my lab to date."

The differences in carnivore populations are even more surprising when you consider that these animals are most active at night, dawn and dusk, and that people visit parks during the day, Reed said. "We assumed that carnivores and people were avoiding each other in time and space," she said.

Reed was initially conducting a different study on carnivores when she realized that the differences in their numbers between sites with and without public access were so large that they obscured the data she was looking for. "The evidence I was seeing was strong enough that it warranted a study of its own," Reed said.

For her study, which will be published in the September 2008 issue of the journal Conservation Letters but is now available online, Reed chose 14 parks in Marin, Sonoma and Napa counties and paired them with 14 nearby preserves with no public access. Each paired park and preserve had to have similar characteristics, such as size and amount of nearby development. The 14 parks include Jack London and Annadel state parks and Shiloh Ranch and Spring Lake regional parks in Sonoma County.

Historically, people have tended to view recreation and conservation efforts as tightly linked, especially when it comes to land management. Parks aim to both protect natural resources and allow visitors to enjoy them. But if this enjoyment is actually detrimental to conservation, as Reed's findings suggest, park agencies may have to change how they think about preservation, the researchers said. Reed feels that, in some cases, it may be necessary to create separate sites for conservation and recreation. That could mean separate areas within large parks or designating small parks, such as the ones Reed surveyed, as either for conservation or recreation,

"People used to think, 'Well, just keep everyone on the trail.' Before this study, that would have been a reasonable assumption," Merenlender said. "But now that we're showing this larger scale effect, we're going to have to shift our working paradigm on how we address land management."

To look at carnivore populations, Reed walked one to two miles in each park or preserve, picking up and bagging every carnivore dropping she saw. Because it's difficult to identify droppings visually, she used genetic analyses to determine each scat's owner.

Reed was surprised to find that coyotes and bobcats were avoiding parks with public access entirely, not just their trails. The parks she visited are small enough that the animals can't find a peaceful spot, Reed said.

Reed thinks the carnivores are leaving the parks for calmer neighboring areas. Her study didn't address the reason for their flight, but she thinks it likely that the mere presence of humans disturbs the animals. The noise of humans traipsing and chatting through parks, our smell or just the sight of us could frighten animals away from their homes, Reed said.

Between urban sprawl, agriculture and outdoor enthusiasts, coyotes, bobcats and foxes may be hard pressed to find undisturbed areas. Outdoor recreation is on the rise around the world, especially in natural areas surrounding large urban centers, such as in the San Francisco Bay Area. For example, the number of Americans day hikers jumped nearly 800 percent between 1960 and 2000, according to national surveys.

These extra hikers, bird-watchers and mountain bikers put pressure on park agencies to open government land and private preserves for public access. "This level of recreational activities in parks is just one of the many ways that the growing human population is squeezing the habitat for these more sensitive species," Reed said.

Reed said her findings affected her on a personal level, because she enjoys hiking and other outdoor activities. "For many of us, as conservation biologists, as environmentalists, this is a pretty uncomfortable result," she Reed.

The National Science Foundation, Sigma Xi, the Phi Beta Kappa Society, the Budweiser Conservation Scholarship Program and the Robert and Patricia Switzer Foundation provided funding for this study.

SOURCE : University of California - Berkeley

Common cooking spice shows promise in combating diabetes and obesity

2008-06-30T22:48:00.000+07:00

Turmeric, an Asian spice found in many curries, has a long history of use in reducing inflammation, healing wounds and relieving pain, but can it prevent diabetes? Since inflammation plays a big role in many diseases and is believed to be involved in onset of both obesity and Type 2 diabetes, Drew Tortoriello, M.D., an endocrinologist and research scientist at the Naomi Berrie Diabetes Center at Columbia University Medical Center, and his colleagues were curious what effect the herb might have on diabetic mice.

Dr. Tortoriello, working with pediatric resident Stuart Weisberg, M.D., Ph.D., and Rudolph Leibel, M.D., fellow endocrinologist and the co-director of the Naomi Berrie Diabetes Center, discovered that turmeric-treated mice were less susceptible to developing Type 2 diabetes, based on their blood glucose levels, and glucose and insulin tolerance tests. They also discovered that turmeric-fed obese mice showed significantly reduced inflammation in fat tissue and liver compared to controls. They speculate that curcumin, the anti-inflammatory, anti-oxidant ingredient in turmeric, lessens insulin resistance and prevents Type 2 diabetes in these mouse models by dampening the inflammatory response provoked by obesity.

Their findings are the subject of a soon-to-be published paper in Endocrinology and were presented at ENDO 2008, the Endocrine Society's annual meeting in San Francisco this week.

Turmeric (Curcuma longa) has no known dose-limiting toxicities in doses of up to at least 12 grams daily in humans. The researchers tested high-doses of a dietary curcumin in two distinct mouse models of obesity and Type 2 diabetes: high-fat-diet-fed male mice and leptin-deficient obese female mice, with lean wild-type mice that were fed low-fat diets used as controls.

The inflammation associated with obesity was shown several years ago by researchers in the Naomi Berrie Diabetes Center to be due in part to the presence of immune cells called macrophages in fat tissues throughout the body. These cells produce "cytokine" molecules that can cause inflammation in organs such as the heart, and islets of the pancreas, while also increasing insulin resistance in muscle and liver. Researchers hypothesized that by suppressing the number and activity of these cells, with turmeric or a drug with similar actions, it may be possible to reduce some of the adverse consequences of obesity.

Curcumin administration was also associated with a small but significant decline in body weight and fat content, despite level or higher calorie consumption, suggesting that curcumin beneficially influences body composition.

"It's too early to tell whether increasing dietary curcumin [through turmeric] intake in obese people with diabetes will show a similar benefit," Dr. Tortoriello said. "Although the daily intake of curcumin one might have to consume as a primary diabetes treatment is likely impractical, it is entirely possible that lower dosages of curcumin could nicely complement our traditional therapies as a natural and safe treatment."

For now, the conclusion that Dr. Tortoriello and his colleagues have reached is that turmeric – and its active anti-oxidant ingredient, curcumin – reverses many of the inflammatory and metabolic problems associated with obesity and improves blood-sugar control in mouse models of Type 2 diabetes.

In addition to exploring novel methods of curcumin administration to increase its absorption, they are also interested in identifying novel anti-inflammatory processes invoked by curcumin and in adapting those processes in the development of more potent curcumin analogues.

SOURCE : Columbia University Medical Center

DNA study unlocks mystery to diverse traits in dogs

2008-06-30T21:57:00.000+07:00

What makes a pointer point, a sheep dog herd, and a retriever retrieve? Why do Yorkshire terriers live longer than Great Danes? And how can a tiny Chihuahua possibly be related to a Great Dane?

Dogs vary in size, shape, color, coat length and behavior more than any other animal and until now, this variance has largely been unexplained. Now, scientists have developed a method to identify the genetic basis for this diversity that may have far-reaching benefits for dogs and their owners.

In the cover story of tomorrow's edition of the science journal Genetics, research reveals locations in a dog's DNA that contain genes that scientists believe contribute to differences in body and skull shape, weight, fur color and length – and possibly even behavior, trainability and longevity.

"This exciting breakthrough, made possible by working with leaders in canine genetics, is helping us piece together the canine genome puzzle which will ultimately translate into potential benefit for dogs and their owners," said study co-author Paul G. Jones, PhD, a Mars Veterinary™ genetics researcher at the Waltham® Centre for Pet Nutrition – part of Mars® Incorporated, a world leader in pet care that has been studying canine genetic science for the past eight years. "By applying this research approach, we may be able to decipher how genes contribute to physical or behavioral traits that affect many breeds."

Dogs originally derived from the wolf more than 15,000 years ago – a blink of the eye in evolutionary terms. Selective breeding produced dogs with physical and behavioral traits that were well suited to the needs or desires of their human owners, such as herding or hunting ability, coat color and body and skull shape and size. This resulted in the massive variance seen among the more than 350 distinct breeds that make up today's dog population. Until now, the genetic drivers of this diversity have intrigued scientists who have been trying to explain how and why the difference in physical and behavioral traits in dogs changed so rapidly from its wolf origins.

An international team of researchers, which included scientists at the National Human Genome Research Institute, the University of Utah, Sundowners Kennels in Gilroy, California and Mars' Waltham Center for Pet Nutrition in the United Kingdom, studied simple genetic markers known as Single Nucleotide Polymorphisms, or SNPs, to find places in the dog genome that correlate with breed traits. Because many traits are "stereotyped" – or fixed within breeds – researchers can zero in on these "hot spots" to see what specific genes are in the area that might contribute to differences in traits.

The research used 13,000 dog DNA samples provided by Mars Veterinary, which holds one of the most comprehensive canine DNA banks in the world. This collection has been built up with the help of pet owners who have consented to their pets providing cheek swabs and blood samples for the database. Mars' DNA bank allowed the study to cover most of the American Kennel Club recognized breeds that span a wide variety of physical and behavioral traits and differences in longevity.

"With further refinement and additional data, this method could be used to tailor products that may benefit the health of pets," Jones said. "Pet owners and veterinarians may be able to develop better care regimes based on this knowledge. In addition, genetic information about behavioral traits, such as trainability and temperament, could also help veterinarians identify the most lifestyle-appropriate pet for an owner."

This research may also have implications for human health, as dogs suffer from many of the same diseases that we do.

Source : Weber Shandwick Worldwide

Nitric Oxide Regulates Plants As Well As People

2008-06-29T22:44:00.000+07:00

Nitric oxide has emerged as an important signaling molecule in plants - as in mammals including people. In studies of a tropical medicinal herb as a model plant, researchers have found that nitric oxide targets a number of proteins and enzymes in plants.

In collaborative work with the research group of Renu Deswal, a faculty member, and her doctoral student at the Botany Department, University of Delhi, India, Agricultural Research Service (ARS) scientist Autar Mattoo has identified 19 such targeted proteins and enzymes in Kalanchoe pinnata, also known as "miracle leaf"

These proteins and enzymes are involved in regulating processes from seed germination to cell development to plant death. Notably, they also regulate many other important processes including photosynthesis, sugar metabolism, disease- and stress tolerance in plants.

Mattoo is a plant physiologist with the ARS Sustainable Agricultural Systems Laboratory at Beltsville, Md.

The collaborative research suggests that the effects of nitric oxide, a sometimes toxic byproduct of nitrogen oxidation in soil, may have broader implications in plant processes than realized. Its modification of proteins, a process called S-nitrosylation, is increasingly recognized as an ubiquitous regulatory reaction in plants and mammals.

Mattoo and Deswal have shown for the first time that nitric oxide inactivates Rubisco, a major enzyme involved in carbon dioxide fixation and photosynthesis in plants.

Kalanchoe represents plants that have a unique method of carbon dioxide fixation that is shared by succulent plants. Kalanchoe has diverse possible medicinal benefits suggesting the presence of interesting processes at work. Mattoo hopes to do similar studies with major crops grown in different production systems, with an eye toward improving both crop yields and quality, including nutritional benefits.

Other scientists have studied nitric oxide targets in the most common model plant, Arabidopsis. Mattoo and collaborators found that Kalanchoe had some nitric oxide targets in common with Arabidopsis, such as Rubisco and drought-protective proteins. They also found new protein targets in Kalanchoe that have not been reported previously.

A paper discussing these results will be published in FEBS Journal.

SOURCE : Wiley-Blackwell

Potential Key To Better Drugs To Fight Toxoplasmosis Parasite Discovered

2008-06-29T21:01:00.000+07:00

Discoveries by Indiana University School of Medicine scientists have opened a promising door to new drugs for toxoplasmosis and other parasites that now can evade treatments by turning dormant in the body.

Their findings help explain how the parasite that causes toxoplasmosis transforms into a cyst form that resists drugs and the body's immune system, yet can emerge from its dormant state to strike when a patient's immune system is weakened.

Led by William J. Sullivan Jr., Ph.D., assistant professor of pharmacology and toxicology, and Ronald C. Wek, Ph.D., professor of biochemistry and molecular biology, the research team found a cellular signaling system that takes hold when the parasite is stressed, enabling it to transform into the cyst surrounded by a protective barrier.

The signaling system identified by the IU team could serve as a target to block the transformation into the cyst form or to attack the parasite while in the cyst form. Their report was published in the June 13 issue of the Journal of Biological Chemistry.

The Toxoplasma gondii parasite converts from an active state to the inactive cyst state when it is stressed, for example, by heat from fever. Stress response mechanisms have been well studied in yeast and other organisms, but the pathways used by the toxoplasmosis parasite had not been determined.

"We found a cellular signal that appears to put the parasite to sleep, which in turn tells us something new about how opportunistic pathogens such as Toxoplasma awaken to cause disease during immunosuppression," said Dr. Sullivan.

An estimated 60 million people in the United States are infected with the toxoplasmosis parasite, but for most infection produces flu-like symptoms or no symptoms at all. However, for people with immune system problems -- such as those undergoing chemotherapy or people with AIDS -- the disease can cause serious effects including lung problems, blurred vision and seizures. Also, infants born to mothers who are infected during or shortly before pregnancy are at risk for severe complications, miscarriages or stillbirths.

Medications to treat Toxoplasma gondii are effective but too toxic for extended use, and they don't affect the cyst form, said Dr. Sullivan.

"A healthy immune system can keep this parasite in the cyst state. Without a healthy immune system, this organism can run rampant," said Dr. Sullivan. "This can be a very serious problem for people with AIDS."

The discovery linking this stress-response mechanism to cyst formation and maintenance not only offers a possible target for new drugs, but it could also lead to a preventative vaccine -- for animals.

The Toxoplasma gondii parasite can infect most animals and birds, but it reproduces in cats, which can shed the parasite in their feces. Humans can be infected through contact with the infected feces or litter. People can also become infected by consuming undercooked meat.

A vaccine to prevent infection in cats and livestock could prevent a significant proportion of human infections, Dr. Sullivan said.

The research of Drs. Sullivan and Wek is supported by the National Institutes of Health and the American Heart Association.

SOURCE : Indiana University

Database shows effects of acid rain on microorganisms in Adirondack Lakes

2008-06-29T11:45:00.000+07:00

Prior to the federal Clean Air Act, unhindered industrial emissions were released into the air throughout the Midwestern and Eastern United States for decades. Many of those harmful chemicals came right back down to earth in the form of acid rain, a chemical concoction that includes nitric and sulfuric acid.

Researchers have long known that acid rain can severely decrease the diversity of plant and animal communities in fresh water lakes and ponds. However, little is known about how microscopic bacteria, which form the foundation of freshwater ecosystems, respond to acidification.

To address this knowledge gap, researchers at the Darrin Fresh Water Institute of Rensselaer Polytechnic Institute have developed one of the most comprehensive databases in existence on the impacts of acid rain at the foundation of the biological community.

The team found a general link between increased acidity and decreased bacterial diversity, but surprisingly, most of the dominant species of bacteria were not directly impacted by acidification. However, some rarer types of bacterial populations were significantly or strongly correlated to acidity, rising and falling with fluctuations in water pH. The findings could eventually allow scientists to use these bacteria as indicators of lake recovery, according to Sandra Nierzwicki-Bauer, director of the Darrin Fresh Water Institute and professor of biology.

The research is part of a much broader study on how Adirondack lakes are recovering from the impacts of acidification. "Thanks in large part to the federal Clean Air Act and increased state focus on improving air quality here in New York, we are seeing a number of these lakes on a trajectory to recovery, but up until now we have had little understanding of the changing biodiversity of microbial communities within the impacted lakes as they recover," Nierzwicki-Bauer said. "I hope this study will help other scientists expand on the research and use this data to uncover additional information on how acid-impacted lakes and their ecosystems are recovering and how we can hasten that process."

The study was published in a recent edition of the journal Applied and Environmental Microbiology and was undertaken in partnership with the Skidaway Institute of Oceanography. The study is part of what has been a 12-year analysis on the recovery of Adirondack lakes from the effects of acid rain funded by the U.S. Environmental Protection Agency's Adirondack Effects Assessment Program (AEAP). The study included bacterial samples from 18 lakes, ponds, and reservoirs in various stages of recovery from acidification in the Adirondack mountain region of New York state.

For the current study, 31 physical and chemical parameters were examined for each water body, ranging from water clarity and temperature to aluminum and hydraulic retention time for a one-year period. Clone "libraries" representing the bacteria were developed from the lake samples and analyzed. The researchers found that the species diversity in acid-impacted Adirondack lakes were similar to bacterial communities in other, non-impacted freshwater systems

The impacts of acidity on most types of bacteria, including the freshwater classes of Actinobacteria and Betaproteobacteria, were found to be indirect, and population levels appeared more directly linked to a combination of acidity along with other environmental factors such as lake depth and carbon content. Several less abundant types of bacteria, including a species known as Alphaproteobacteria, were strongly correlated to acidity and might someday be used as indicators of lake recovery from acidification, according to Nierzwicki-Bauer.

The researchers are in the process of expanding their study to include an additional 13 Adirondack lakes. They also plan to further investigate the role of specific types of bacteria in the ecosystem to better understand why certain bacteria are so directly impacted by acidity while others appear relatively unaffected.

Source : Rensselaer Polytechnic Institute

Refusal of suicide order: Why tumor cells become resistantCells with irreparable DNA damage normally induce programmed cell death, or apoptosis. Howev

2008-06-28T20:47:00.000+07:00

Cells with irreparable DNA damage normally induce programmed cell death, or apoptosis. However, this mechanism often fails in tumor cells so that transformed cells are able to multiply and spread throughout the body. Scientists at the German Cancer Research Center (Deutsches Krebsforschungszentrum, DKFZ) have now discovered a possible cause of this failure. Tumor cells simply degrade a protein that triggers apoptosis in the case of DNA damage. Blocking this protein degradation might set apoptosis back in operation and, thus, increase the effectiveness of radiotherapy or chemotherapy. The researchers have now published their results in Nature Cell Biology.

Human Tumor Cells

Green fluorescent human breast cancer cells

Proteins that trigger programmed cell death, or apoptosis, must be kept under careful control. After all, a cell should induce its own death only if its genetic material is damaged so severely that there is a danger of its transformation into a malignantly growing tumor cell. However, minor damages in the DNA can be corrected by the cell's special repair mechanisms – hence, no reason to commit suicide!

Among the proteins that trigger apoptosis after severe DNA damage is the HIPK2 molecule. Scientists in Dr. Thomas Hofmann's research group at the German Cancer Research Center (DKFZ) have now shown that although HIPK2 is continuously produced in healthy cells, it is instantly degraded again. An enzyme called Siah-1 attaches labels to HIPK2 marking it as "garbage". Thus, the cell prevents that apoptosis is induced "accidentally".

Slightly damaged cells enter a kind of alarm status: They block degradation of HIPK2 by Siah-1 for a short time. But as soon as the damage is repaired, the cell immediately resumes labeling HIPK2 as garbage and degrades the molecule. Only in severely damaged cells, such as by a broken DNA double strand, degradation of HIPK2 by the Siah-1 enzyme is blocked permanently. As a result, HIPK2 accumulates, apoptosis is triggered, and the cell commits suicide.

Researchers assume that this could be one of the reasons why radiation therapy or chemotherapy is sometimes ineffective. Both treatment methods cause severe damage to tumor cells, which eventually leads to programmed cell death. "If resistances occur, this is often caused by tumor cells 'refusing' to take the order to commit suicide," Thomas Hofmann explains.

To prevent HIPK2 degradation, Hoffmann and his colleagues conducted experiments in which they blocked the Siah-1 enzyme. As a result, HIPK2 was able to accumulate even in cells that were only slightly damaged, and apoptosis was induced. "Cancer medicine might be able to make use of our discovery," speculates Hofmann. "For example, we could use a Siah-1 blocker simultaneously with chemotherapy or radiotherapy to get the cells back into the apoptosis program."

Source : Helmholtz Association of German Research Centres

Desert Plant May Hold Key To Surviving Food Shortage

2008-06-28T14:25:00.000+07:00

Scientists at the University of Liverpool are investigating how a Madagascan plant could be used to help produce crops in harsh environmental conditions.

The plant, Kalanchoe fedtschenkoi, is unique because, unlike normal plants, it captures most of its carbon dioxide at night when the air is cooler and more humid, making it 10 times more water-efficient than major crops such as wheat. Scientists will use the latest next-generation DNA sequencing to analyse the plant’s genetic code and understand how these plants function at night.

The project will generate a genome sequence database that will be used as an Internet resource for plant biologists throughout the world.

The research comes at a time when farmland across the globe normally used for growing food such as rice and wheat is being taken over by bio-fuel crops used for bioethanol production as a petrol substitute. Scientists believe that the novel genes found in Kalanchoe could provide a model of how bio-fuel plants could be grown on un-utilised desert and semi-arid lands, rather than on fertile farmland needed for producing food.

Biological scientist, Dr James Hartwell, said: “There is a lot of concern over food shortage at the moment, with more farmland being commandeered for bio-fuels. As a result of changes in our climate the Intergovernmental Panel on Climate Change has predicted a large expansion of arid regions so there is an increasing need for new crop varieties that can be productive in deserts.

“Kalanchoe is a good example of how plants can flourish in harsh environments. If we can understand how it is able to photosynthesise using much less water than current crops, we may be able to use its genetic code to develop a crop able to withstand harsh environmental conditions. It is essential that farmland be returned to food production.”

The genetic code of the plant will be deciphered using a DNA sequencing machine that uses an enzyme found in fireflies as a flash light to help read the DNA strand.

Liverpool is one of only two universities in the UK with the technology, which can read up to half a billion DNA letters in a few hours compared to more widely used technology that can only process 50,000.

The project is funded by the Biotechnology and Biological Sciences Research Council (BBSRC).

SOURCE : University of Liverpool

Gene silencer and quantum dots reduce protein production to a whisper

2008-06-28T09:35:00.000+07:00

More than 15 years ago scientists discovered a way to stop a particular gene in its tracks. The Nobel Prize-winning finding holds tantalizing promise for medical science, but so far it has been difficult to apply the technique, known as RNA interference, in living cells.

Each of these jars contains the same substance.
The difference is the size of the particles. Quantum dots, suspended in liquid,
absorb white light and then reemit it in a specific color that depends on the particle's size.
Each quantum dot is about one ten-millionth of an inch in diameter
and is composed of a few hundred atoms of material. Credit: Xiaohu Gao, University of Washington

Now scientists at the University of Washington in Seattle and Emory University in Atlanta have succeeded in using nanotechnology known as quantum dots to address this problem. Their technique is 10 to 20 times more effective than existing methods for injecting the gene-silencing tools, known as siRNA, into cells.

"We believe this is going to make a very important impact to the field of siRNA delivery," said Xiaohu Gao, a UW assistant professor of bioengineering and co-author of a study published online this week in the Journal of the American Chemical Society.

"This work helps to overcome the longstanding barrier in the siRNA field: How to achieve high silencing efficiency with low toxicity," said co-author Shuming Nie, a professor in the Wallace H. Coulter Department of Biomedical Engineering, jointly affiliated with the Georgia Institute of Technology and Emory University.

Other co-authors are Maksym Yezhelyev and Ruth O'Regan at Emory and Lifeng Qi at the UW.

Short pieces of RNA, the working copy of DNA, can disable production of a protein by silencing, or deactivating, a stretch of genetic code. Research laboratories regularly use the technique to figure out what a particular gene does. In the body, RNA interference could be used to treat conditions ranging from breast cancer to deteriorating eyesight.

The recent experiments used quantum dots, fluorescent balls of semiconductor material just six nanometers across (lining up 9,000 dots end to end would equal the width of a human hair). Quantum dots' unique optical properties cause them to emit light of different colors depending on their size. The dots are being developed for cellular imaging, solar cells and light-emitting diodes.

This paper describes one of the first applications of quantum dots to drug delivery.

Each quantum dot was surrounded by a proton sponge that carried a positive charge. Without any quantum dots attached, the siRNA's negative charge would prevent it from penetrating a cell's wall. With the quantum-dot chaperone, the more weakly charged siRNA complex crosses the cellular wall, escapes from the endosome (a fatty bubble that surrounds incoming material) and accumulates in the cellular fluid, where it can do its work disrupting protein manufacture.

Key to the newly published approach is that researchers can adjust the chemical makeup of the quantum dot's proton-sponge coating, allowing the scientists to precisely control how tightly the dots attach to the siRNA.

Quantum dots were dramatically better than existing techniques at stopping gene activity. In experiments, a cell's production of a test protein dropped to 2 percent when siRNA was delivered with quantum dots. By contrast, the test protein was produced at 13 percent to 51 percent of normal levels when the siRNA was delivered with one of three commercial reagents, or reaction-causing substances, now commonly used in laboratories.

Central to the finding is that fluorescent quantum dots allow scientists to watch the siRNA's movements. Previous siRNA trackers gave off light for less than a minute, while quantum dots, developed for imaging, emit light for hours at a time. In the experiments the authors were able to watch the process for many hours to track the gene-silencer's path.

The new approach is also five to 10 times less toxic to the cell than existing chemicals, meaning the quantum dot chaperones are less likely to harm cells. The ideal delivery vehicle would have no effect; the only biological change would be siRNA blocking cells' production of an unwanted protein.

The exact reason that the quantum dots were more effective than previous techniques is, however, still a mystery.

"We believe the improvement is caused by the endosome escape, and the ability of the quantum dots to separate from the siRNA," Gao said.

Quantum dots are not yet approved for use in humans. The authors are now transferring their techniques to particles of iron oxide, several types of which have been approved by the Food and Drug Administration for use in humans. They are also working to target cancer cells by attaching to specific markers on the cells' surface. "Looking forward, this work will have important implications in in-vivo siRNA therapeutics, which will require the use of nontoxic iron oxide and biodegradable polymeric carriers rather than quantum dots," Nie said.

Source : University of Washington