June 7, 2007, 7:36 PM CT

How bacteria to resist human immune defenses

Researchers at the National Institute of Allergy and Infectious Diseases (NIAID), a component of the National Institutes of Health, have discovered a survival mechanism in a common type of bacteria that can cause illness. The mechanism lets the bacteria protect itself by warding off attacks from antimicrobial peptides (AMPs), which are defense molecules sent by the body to kill bacteria.

Bacteria are divided into two types, gram-positive and gram-negative, with the primary difference being the nature of the bacterial cell wall. Little is known about how gram-positive bacteriasuch as those that can lead to food poisoning, skin disorders and toxic shockavoid being killed by AMPs. AMPs are made by virtually all groups of organisms, including amphibians, insects, several invertebrates and mammals, including humans.

Gram-positive bacteria are major threats to human health, especially due to increasing problems with drug resistance, and these findings may help chart a path to designing new drugs to bolster our antimicrobial treatment options, notes NIAID Director Anthony S. Fauci, M.D.

Led by Michael Otto, Ph.D., of NIAIDs Rocky Mountain Laboratories (RML), the scientists used the gram-positive bacterium Staphylococcus epidermidis to study its response to a specific human AMP, human beta defensin 3. S. epidermidis is one of several hard-to-treat infectious agents that can be transmitted to patients in hospitals via contaminated medical implants. Findings by Dr. Ottos research group are published in the May 29 issue of the Proceedings of the National Academy of Science. Other well-known types of gram-positive bacteria include agents that cause anthrax, strep throat, flesh-eating disease and various types of food poisoning......... Posted by: Janet      Read more         Source

June 6, 2007, 9:54 PM CT

Organic Food Miles take toll on environment

Organic fruit and vegetables may be healthier for the dinner table, but not necessarily for the environment, a University of Alberta study shows.

The study, conducted by a team of student scientists in the Department of Rural Economy at the University of Alberta in Edmonton, Canada, showed that the greenhouse gas emitted when the produce is transported from great distances mitigates the environmental benefits of growing the food organically.

If youre buying green, you should consider the distance the food travels. If its travelling further, then some of the benefits of organic crops are cancelled out by extra environmental costs, said researcher Vicki Burtt.

Burtt and her fellow scientists compared the cost of food miles between organic and conventionally grown produce, and observed that there was little difference in the cost to the environment.

Food miles are defined as the distance that food travels from the field to the grocery store. The study observed that the environmental cost of greenhouse gas (CO2) emitted to transport 20 tonnes of organically grown produce was comparable to that of bringing the same amount of conventional fruit and vegetables to market.

For the study, the team collected retail price data from six grocery stores and interviewed suppliers about their shipping methods. They created comparable food baskets of both organic and conventionally-grown fruit and vegetables being transported to Edmonton stores by truck, train or ship, and observed that most travels by truck. Since 1970 truck shipping has increased, replacing more energy-efficient rail and water transport......... Posted by: Erica      Read more         Source

June 6, 2007, 9:33 PM CT

Caribbean Frogs Started From South America

Nearly all of the 162 land-breeding frog species on Caribbean islands, including the coqui frogs of Puerto Rico, originated from a single frog species that rafted on a sea voyage from South America about 30-to-50-million years ago, as per DNA-sequence analyses led by a research group at Penn State, which would be reported in the 12 June 2007 issue of the Proceedings of the National Academy of Sciences and posted in the journal's online early edition this week. Similarly, the researchers observed that the Central American relatives of these Caribbean frogs also arose from a single species that arrived by raft from South America.

"This discovery is surprising because no prior theories of how the frogs arrived had predicted a single origin for Caribbean terrestrial frogs and because groups of close relatives rarely dominate the fauna of an entire continent or major geographic region," explained Penn State's Blair Hedges, the evolutionary biologist and professor of biology who directed the research. "Because land connections among continents have allowed land-dwelling animals to disperse freely over millions of years, the fauna of any one continent is commonly a composite of a number of types of animals".

The field work for the study mandatory nearly three decades to complete because a number of of the species are restricted to remote and isolated mountain tops or other inaccessible areas. Some species included in the study now are thought to beextinct because of habitat degradation and possibly other causes such as climate change......... Posted by: Kelly      Read more         Source

June 6, 2007, 9:21 PM CT

Loss of Stem Cells Correlates with Premature Aging

Researchers at the Abramson Family Cancer Research Institute of the University of Pennsylvania have found that deleting a gene important in embryo development leads to premature aging and loss of stem cell reservoirs in adult mice. This gene, ATR, is essential for the body's response to damaged DNA, and mutations in proteins in the DNA damage response underlie certain types of cancer and other disorders in humans. This work appears in the inaugural issue of Cell Stem Cell.

"The reason these mice age prematurely is that we're exhausting their ability to renew tissues," says Eric J. Brown, PhD, Assistant Professor of Cancer Biology. "These findings may be helpful to the aging and oncology fields since premature aging syndromes and many cancers involve the loss of DNA repair genes".

When the researchers deleted ATR in the tissues of adult mice, they noticed that the mice showed signs of premature aging, such as hair graying, hair loss, and osteoporosis, within three to four months.

To be able to renew itself, most tissues have a reservoir of specific adult stem cells. These stem cells don't divide as frequently as other cell types since they need to maintain the integrity of their DNA, and multiple divisions lead to natural breaks in DNA. But when these stem cells are needed, their progeny can rapidly divide and are able to replenish the tissue with new cells......... Posted by: Janet      Read more         Source

June 5, 2007, 0:16 AM CT

How Spores Break Out Of Dormant State

Tapping into the unknown world of awakening dormant bacterial spores, scientists have revealed through atomic force microscopy (AFM) the alterations of spore coat and germ cell wall that accompany the transformation from a spore to a vegetative cell.

When starved of nutrients Bacillus (rod-shaped bacteria) cells initiate a series of genetic, biochemical and structural events that result in the formation of metabolically dormant spores. They can remain dormant for extended periods and, partly because of their tough spore coat, have a significant resistance to extreme environmental factors including heat, radiation and toxic chemicals. However, once in favorable conditions, spores break the dormant state through germination and reenter the vegetative mode of replication.

Eventhough significant progress has been made in understanding the biochemical and genetic bases of the spore germination process, it is still unclear how a spore breaks out of its dormant state.

But a new in vitro study of single germinating Bacillus atrophaeus spores details how the spore coat structures break down, and it shows with unprecedented resolution how the new bacterium emerges from the disintegrating spore. The new research, led by Lawrence Livermore National Laboratory scientists, appears in the May 28-June 1 early online edition of the Proceedings of the National Academy of Sciences. The research appears in this weeks (June 4) issue of PNAS......... Posted by: Janet      Read more         Source

May 31, 2007, 11:54 PM CT

Threats to wild tigers growing

The wild tiger now occupies a mere 7 percent of its historic range, and the area known to be inhabited by tigers has declined by 41 percent over the past decade, as per an article reported in the June 2007 issue of BioScience. Growing trade in folk medicines made from tiger parts and tiger skins, along with habitat loss and fragmentation, is thought to bethe chief reason for the losses. The assessment, by Eric Dinerstein of the World Wildlife Fund and 15 coauthors, describes the wild tiger's population trajectory as "catastrophic" and urges international cooperation to ensure the animal's continued existence in the wild.

Despite the discouraging numbers--there are thought to beonly about 5,000 wild tigers left--some conservation programs have been successful. Dinerstein and his coauthors highlight a program in the Terai-Arc Landscape of northwestern India and southern Nepal as a notable victory. The scheme features wildlife corridors that connect 12 reserves. Tiger conservation efforts have also been successful in the Russian Far East. A number of tiger reserves in the India, in contrast, have been mismanaged and have failed to protect the animals, as per the article.

Plans to make use of tiger parts harvested from farmed tigers in China represent an emerging threat, the authors argue. Any trade in tiger parts encourages poaching, because products made from animals farmed at great expense cannot be distinguished from products made from wild tigers......... Posted by: Kelly      Read more         Source

May 30, 2007, 0:07 AM CT

Sharks Use Their Noses And Bodies To Locate Smells

Sharks are known to have a keen sense of smell, which in a number of species is critical for finding food. However, as per new research from Boston University marine biologists, sharks can not use just their noses to locate prey; they also need their skin specifically a location called the lateral line. The lateral line is an organ used by all fish to detect, with exquisite sensitivity, movement and vibration in the surrounding water. As per the research team, this is similar to how humans can sense air flow with the small hairs on the face. Until now, it had not been demonstrated that the lateral line also aids in the tracking of odor plumes.

"Odor plumes are complex, dynamic, three-dimensional structures used by a number of animal species to locate food, mates, and home sites. However, odor itself has no directional properties, so animals must use a variety of senses to get the directional information for a smell," said Jelle Atema, professor of biology at Boston University and co-author of study.

The new study examined the contribution of the olfactory system, the lateral line, and vision in odor source detection and localization in the smooth dogfish shark. The results, which appear in the June 1 issue of the Journal of Experimental Biology, show that this shark is severely handicapped in its ability to locate the source of an odor when deprived of information from its lateral line, especially in the dark......... Posted by: Kelly      Read more         Source

May 30, 2007, 0:00 AM CT

Eavesdropping comes naturally to young song sparrows

Long before the National Security Agency began eavesdropping on the phone calls of Americans, young song sparrows were listening to and learning the tunes sung by their neighbors.

University of Washington scientists exploring how male song sparrows (Melospiza melodia) acquire their song repertoires have found the first evidence that young birds choose a number of of their songs by eavesdropping on the tuneful interactions between other sparrows.

In laboratory experiments, the young sparrows were exposed to two adult "tutors," one of which they directly interacted with vocally and a second one that they only overheard singing with another young bird. Even though they learned from both tutors, the young birds acquired more than twice as a number of songs from the tutor on which they eavesdropped, said Michael Beecher, lead author of the study and a UW psychology and biology professor.

Researchers study song learning in songbirds in part because it has many parallels with human language learning, and Beecher thinks eavesdropping also could play a role in how infants learn language.

Sparrows in the wild are thought to learn their songs in two phases. The first phase occurs in their first summer, when they hear and memorize songs sung by adult birds. The following spring, when the young birds are establishing their own territory, they modify and prune their repertoire so their songs are more similar to their neighbors. A song sparrows repertoire crystallizes at around 10 to 11 months of age and does not change......... Posted by: Kelly      Read more         Source

May 23, 2007, 9:48 PM CT

4-leaf Clovers

I find four-leaf clovers frequently, even when not explicitly looking.

A number of find this "gift" extraordinary, and even though this mutation is reported to only occur once in about 10,000 clovers, getting lucky isn't as hard as one would think......... Posted by: Falaco Soliton      Read more         Source

May 23, 2007, 8:11 PM CT

No sex please, we're female sharks!

Female sharks can reproduce without having sex, researchers have found. A female hammerhead shark has given birth without mating with a male and its offspring has no paternal DNA.

An international team of scientists from Queen's University Belfast, the Guy Harvey Research Institute at Nova Southeastern University in Florida and the Henry Doorly Zoo in Nebraska has found evidence that sharks can reproduce asexually by an unusual method known as "parthenogenesis". This is the first scientific report of asexual reproduction in sharks.

Head of the Queen's research team and co-author of study, Dr Paulo Prodohl, from the School of Biological Sciences, said: "The findings were really surprising because as far as anyone knew, all sharks reproduced only sexually by a male and female mating, requiring the embryo to get DNA from both parents for full development, just like in mammals".

"The discovery that sharks can reproduce asexually by parthenogenesis now changes this paradigm, leaving mammals as the only major vertebrate group where this form of reproduction has not been seen".

The long-term study was prompted by the unexpected birth of a baby hammerhead shark in an aquarium at the Henry Doorly Zoo in December 2001. The astonishing thing about the birth was that none of the three candidate mother hammerheads in the tank, all of whom been caught in Florida waters as babies themselves, had been exposed to any male hammerhead sharks for the three years since their captivity......... Posted by: Kelly      Read more         Source