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Archive - Sep 29, 2011

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Australian Tree Frogs Endure Cold to Collect Precious Water

Research published in the October issue of The American Naturalist shows that Australian green tree frogs survive the dry season with the help of the same phenomenon that fogs up eyeglasses in the winter. According to researchers from Charles Darwin University in Australia, tree frogs often plop themselves down outside on cool nights during the dry season in tropical Australia. When they return to their dens, condensation forms on their cold skin—just like it does on a pair of glasses when we come in from the cold. The researchers found that frogs absorb this moisture through their skin, which helps to keep them hydrated during periods of little or no rain. Before this study, the frogs' dry-season excursions were a bit mysterious. "Every once in a while, we would find frogs sitting on a stick under the open sky, on nights when it was so cold they could barely move," said Dr. Chris Tracy, who led the research. "It was a real puzzle." Dr. Tracy and his colleagues thought this behavior might enable the frogs to collect condensation, but the hypothesis had never been tested. The researchers designed a series of experiments using real frog dens in eucalyptus trees and artificial ones made from PVC pipe. They wanted to see if the frogs could collect enough moisture through condensation to compensate for what they lost being in the cold. They found that a cold night out cost a frog as much as .07 grams of water. However, a frog could gain nearly .4 grams, or nearly 1 percent of its total body weight, in water upon returning to the warm den. The researchers also tested how well a frog's skin could absorb water, and found that as much as 60 percent of each water drop could be absorbed. The results show that frogs can use condensation to hydrate themselves.

“Alarm Clock” Gene Identified

Ever wondered why you wake up in the morning ---- even when the alarm clock isn't making jarring noises? Wonder no more. Researchers at the Salk Institute for Biological Studies have identified a new component of the biological clock, a gene responsible for starting the clock from its restful state every morning. The biological clock ramps up our metabolism early each day, initiating important physiological functions that tell our bodies that it's time to rise and shine. Discovery of this new gene and the mechanism by which it starts the clock everyday may help explain the genetic underpinnings of sleeplessness, aging, and chronic illnesses, such as cancer and diabetes, and could eventually lead to new therapies for these illnesses. "The body is essentially a collection of clocks," says Dr. Satchindananda Panda, an associate professor in Salk's Regulatory Biology Laboratory, who led the research along with Dr. Luciano DiTacchio, a post-doctoral research associate. "We roughly knew what mechanism told the clock to wind down at night, but we didn't know what activated us again in the morning. Now that we've found it, we can explore more deeply how our biological clocks malfunction as we get older and develop chronic illness." In a report published online on September 30, 2011, in the journal Science, the Salk researchers and their collaborators at McGill University and Albert Einstein College of Medicine describe how the gene KDM5A encodes a protein, JARID1a, that serves as an activation switch in the biochemical circuit that maintains our circadian rhythm. The discovery fills in a missing link in the molecular mechanisms that control our daily wake-sleep cycle. The central player of our biological clock is a protein called PERIOD (PER). The number of PER proteins in each of our cells rises and falls every 24 hours.