June 10, 2006, 4:57 PM CT

the Pulse of a Gene in Living Cells

Scientists at the Albert Einstein College of Medicine of Yeshiva University have observed for the first time that gene expression can occur in the form of discrete "pulses" of gene activity. The researchers used pioneering microscopy techniques, developed by Dr. Robert Singer and colleagues at Einstein, that for the first time allow scientists to directly watch the behavior of a single gene in real time. Their findings appeared in the current issue of Current Biology.

When a gene is expressed or "turned on," genetic information is transferred from DNA into RNA. This process, known as transcription, is crucial for translating the gene's message into a functional protein. Diseases such as cancer can result when genes turn on at the improper time or in the wrong part of the body.

Researchers customarily use microarrays (also known as "gene chips") to assess gene expression in tumors and other tissues. But with millions of cells involved, microarrays reflect only "average" gene expression. Just how a gene is transcribed in a single cell-continuously, intermittently or some other way-has largely been a mystery.

Now, in observing a gene that plays a major role in how an organism develops, the Einstein researchers observed a phenomenon that until now has been indirectly observed and only in bacteria: pulses of transcription that turn on and off at irregular intervals. Dr. Singer and his co-workers used a fluorescent marker that sticks to the gene only when it is active. Under a microscope, this fluorescent marker appears when the gene turns on, then disappears (gene "off") and then appears again (gene "on").........

Posted by: Kelly      Permalink         Source

June 9, 2006, 0:37 AM CT

Climate Change Is Driving Evolution Of Species

Rapid climate changes over the past several decades have led to heritable, genetic changes in animals as diverse as squirrels, birds and mosquitoes, as per University of Oregon evolutionary geneticists.

Writing in the "Perspectives" section of the June 9 issue of SCIENCE, William E. Bradshaw, professor of biology, and Christina Holzapfel, biology research associate, show that diverse animal populations have changed genetically in response to rapid climate change. These genetic changes are in response to altered seasonal events and not to the expected direct effects of increased summer temperatures.

Global warming is proceeding fastest at the most northern latitudes, resulting in longer growing seasons while simultaneously alleviating winter cold stress without imposing summer heat stress. In short, northern climates are becoming more like those in the south.

"Over the past 40 years, animal species have been extending their range toward the poles and populations have been migrating, developing or reproducing earlier," said Bradshaw. "These expansions and changes have often been attributed to 'phenotypic plasticity,' or the ability of individuals to modify their behavior, morphology or physiology in response to altered environmental conditions."

However, adds Holzapfel, "phenotypic plasticity is not the whole story. Studies show that over the past several decades, rapid climate change has led to heritable, genetic changes in animal populations."........

Posted by: Kelly      Permalink         Source

June 9, 2006, 0:11 AM CT

How Gazelles Adapt To Drought

How do gazelles and other large desert mammals adjust their physiology to survive when food and water are in short supply? A fascinating new study from the July/recent issue of Physiological and Biochemical Zoology reveals that gazelles in the deserts of Saudi Arabia have evolved the ability to shrink oxygen-demanding organs such as the liver and heart, allowing them to breathe less. Fewer breaths reduce the amount of water lost to respiratory evaporation during prolonged periods of drought.

"We found that gazelles had the lowest total evaporative water loss ever measured in an arid zone ungulate [hoofed animal]," write Stephane Otrowski (National Wildlife Research Center, Saudi Arabia), Pascal Mesochina (National Wildlife Research Center, Saudi Arabia), and Joseph B. Williams (Ohio State University).

Sand gazelles' livers and hearts--which are important determinants of metabolic rate--decrease significantly in mass during four months of food and water restriction. Conversely, the gut walls, which are responsible in ruminants for 28-46% of whole-body protein synthesis, an energy demanding process, did not decrease significantly in mass. There are few sources of drinking water in the desert, so sand gazelles must rely on vegetation for both food and water requirements.........

Posted by: Kelly      Permalink         Source

June 8, 2006, 7:24 PM CT

Sugar Required For Healthy Brain Development

New approaches to preventing birth defects from a rare metabolic disorder could result from research completed at Washington University School of Medicine in St. Louis. The findings also may have implications for patients with neurodegenerative diseases such as Parkinson's.

To learn more about how glucose affects human development, Mary Carayannopoulos, Ph.D., instructor in pediatrics, developed the first vertebrate model of glucose homeostasis and embryonic development using the zebrafish. Their transparent embryos develop similarly to humans, except that they grow outside of the mother's body, where development can be more easily observed. The model provides the foundation for and insight into the roles of nutrition and genetics in human birth defects.

Carayannopoulos used the zebrafish model to study Glut1 deficiency. Glut1 is a protein that transports glucose in cerebrospinal fluid to the brain. Glut1 deficiency syndrome in humans is linked to microcephaly, epilepsy, developmental delays and other neurologic abnormalities.

Results of the study appear in the recent issue of the Journal of Biological Chemistry, but are available now online. Penny J. Jensen, Ph.D., staff scientist in the Department of Pediatrics, was lead author of the study.

Carayannopoulos lowered Glut1 levels in the zebrafish embryo. Over 72 hours of observing the developing fish, she found that Glut1 deficiency led to cell death in the brain, which uses glucose as its energy source. When injecting the zebrafish with another protein, Bad, which normally activates cell death, the Glut1 and Bad seemed to cancel each other out, correcting brain defects and promoting cell survival.........

Posted by: Kelly      Permalink         Source

June 8, 2006, 0:02 AM CT

Brain Region Linked To Fly Slumber

Scientists at Northwestern University have pinpointed a brain area in flies that is crucial to sleep, raising interesting speculation over the purpose of sleep and its possible link with learning and memory.

In a paper would be published June 8 by the journal Nature, a team led by Ravi Allada, assistant professor of neurobiology and physiology, shows that the so-called mushroom bodies are essential for sleep regulation in the fruitfly Drosophila melanogaster. (In the same issue, a second study, led by Amita Sehgal of the Howard Hughes Medical Institute, produced similar results using different methods.)

How the mushroom bodies control sleep is uncertain, but Allada and his colleagues show that if the area is destroyed chemically, flies sleep less.

Mushroom bodies are known to have a role in learning and memory, raising the possibility that sleep and learning are somehow linked in the fly brain. This lends weight to the notion that, in flies, sleep may function to consolidate memories that are formed during the day -- something that is known to occur in vertebrates.

Sleeping flies are similar to sleeping humans. Both are groggy when woken suddenly and need extra slumber if sleep deprived. It's therefore possible, the authors argue, that a mechanism regulating both sleep and learning could be evolutionarily conserved. So studying the mushroom bodies may help to throw light on the mechanisms governing vertebrate and invertebrate sleep.........

Posted by: Kelly      Permalink         Source

June 7, 2006, 11:47 PM CT

Why Female Birds Boost Up Their Eggs?

In a new study reported in the latest issue of Ethology scientists show that female songbirds can alter the size of eggs and possibly the sex of their chicks as per how they perceive their mate's quality.

The scientists played back attractive ("sexy") songs and less attractive control songs of male canaries to female domesticated canaries. When the females started egg-laying they varied the size of their eggs in the nest as per the attractiveness of the male's song. That is, the more attractive the song, the larger the eggs. However it is remarkable that while larger eggs were more likely to contain male offspring in natural environments, in the experiment there was no difference in brood sex ratio between the different songs played to the females, which suggests different levels of female control. Male birdsong has long been known to attract females and influence mate choice decisions and even induce an alteration in the offspring's sex ratio. This study by Leitner et al. now shows experimentally that hearing attractive song also has a selective impact on female physiology.

45 female domesticated canaries participated in this study that was a collaboration of Royal Holloway, University of London and the Max Planck Institute for Ornithology in Seewiesen and Radolfzell in Gera number of. The birds were kept in large aviaries where their daily behaviour was monitored in a colony before they were tested in the song experiments. The females showed a remarkable consistency in their behavioural and reproductive performance and the song stimuli alone were sufficient to elicit a profound physiological change. This study further highlights the importance of behavioural stimuli for reproductive physiology. Bathroom Pavarottis beware.........

Posted by: Kelly      Permalink         Source

June 6, 2006, 11:34 PM CT

Rediscovery Of Endangered Colombian Frogs

The rediscovery of two frog species feared extinct has made a new Colombian protected area the focal point for efforts to save amphibians from a deadly fungus decimating their populations in Central and South America.

Researchers recently found the two Critically Endangered frogs - the Santa Marta harlequin frog (Atelopus laetissimus) and the San Lorenzo harlequin frog (Atelopus nahumae) - for the first time in 14 years in the El Dorado Nature Reserve established in March on the northwest slope of the Sierra Nevada de Santa Marta massif, on the Caribbean coast of Colombia.

The reserve is an important home for threatened species, and its protection was a top priority of the Alliance for Zero Extinction - a 62-member group of conservation organizations battling global extinctions. In March, alliance members Conservation International (CI) and American Bird Conservancy (ABC) helped Fundacion ProAves of Colombia purchase the 1,600-acre site to protect it as a nature reserve.

Neither of the rediscovered frog species had the deadly fungal disease chytridiomycosis, raising hopes that the species can be saved in the new protected area or through captive breeding. The fungus has been found as close as 40 kilometers (25 miles) away on the other side of the Sierra Nevada mountains, and researchers will study the frogs to learn how they have avoided it.........

Posted by: Kelly      Permalink         Source

June 5, 2006, 11:43 PM CT

Evolution Of Hot Springs Microorganisms

Since their discovery in the late 1970s, microorganisms known as archaea have fascinated researchers with their ability to thrive where no other life can - in conditions that are extremely hot, acidic or salty.

In the 1990s, however, researchers discovered that archaea occur widely in more mundane, low-temperature environments such as oceans and lakes. Now, scientists from the University of Georgia and Harvard University find evidence that these low-temperature archaea might have evolved from a moderate-temperature environment rather than from their high-temperature counterparts - as most researchers had believed. The results appear in the June 2006 issue of the journal Applied and Environmental Microbiology.

"Archaea represent one of the three domains of life on Earth," said Chuanlun Zhang, lead author of the study and associate professor of marine sciences at UGA. "Understanding their evolution may shed light on how all life forms evolve and interact with the environment through geological history."

Zhang and colleagues examined a common group of archaea known as Crenarchaeota. He explains that the Crenarchaeota's low-temperature success may involve a unique molecule known as crenarchaeol that allows the organism's cell membrane to remain flexible in cooler environments.........

Posted by: Erica      Permalink         Source

June 5, 2006, 9:30 PM CT

About Beaver Dams

Beavers, long known for their beneficial effects on the environment near their dams, are also critical to maintaining healthy ecosystems downstream. Scientists have found that ponds created by beaver dams raised downstream groundwater levels in the Colorado River valley, keeping soil water levels high and providing moisture to plants in the otherwise dry valley bottom. The results will be published 8 June in Water Resources Research, a journal of the American Geophysical Union.

Cherie Westbrook of Colorado State University and his colleagues there and at the U.S. Geological Survey in Fort Collins, Colorado, conducted a three-year study in Rocky Mountain National Park, examining valley ecosystems downstream in the Colorado River. They noted that water diverted by beaver dams is forced out of the natural stream channel and spreads across and down the valley for hundreds of meters [yards]. In addition, dams built on the river changed the direction of groundwater flow in the valley. The changes caused water to infiltrate the river banks and flow underground toward the sides of the valley, instead of down the center of the valley.

The scientists suggest that the elevated moisture levels found in soil surrounding the dams would otherwise require water from a very large natural flood, which they estimate as the 200-year flood, to achieve the same expansive water availability to the valley bottom. Additionally, beaver dams built away from natural river channels further redirect water across the valley, enhancing the depth, extent, and duration of inundation associated with smaller floods; they also elevate the water table to sustain plant and animal life during the dry summer season.........

Posted by: Kelly      Permalink         Source

June 3, 2006, 6:47 PM CT

Eardrum Could Lead To Tiny Microphones

Being able to hear the smallest of noises is a matter of life or death for a number of insects, but for the researchers studying their hearing systems understanding how insect ears can be so sensitive could lead to new microphones able to capture and analyse extremely faint sounds.

A multidisciplinary team at the University of Bristol have used funding from the Biotechnology and Biological Sciences Research Council (BBSRC) to explore the workings of the 'ears' of a locust. These are micrometre thick membranes with complex and varying structural properties. The thickness of the membrane varies at different points and this affects how it responds to sounds - and in the case of ambient noise the team have discovered the membrane oscillates by only a few nanometres. The thickness of a human hair is about 80,000 nanometres across.

Professor Daniel Robert is the research leader at Bristol: "We have found that different sound frequencies elicit very different mechanical responses in the locust hearing system. By studying these tiny nanoscale movements and understanding how sound waves are turned into mechanical responses we may be able to develop microphones based on the functions of natural hearing. These could detect very faint sounds and analyse their frequency, something that current microphones cannot pick up."........

Posted by: Kelly      Permalink         Source