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     Volume 4 Issue 64 | September 23, 2005 |

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How do defensins stop viruses?
Compounds called defensins -- known to stop viruses from entering cells -- appear to do so by preventing the virus from merging to cells' outer membrane. This discovery provides a basic understanding of a first-line defense against such viruses as HIV and the influenza virus, said Dr. Duane Alexander, director of the National Institute of Child Health and Human Development. This finding may ultimately lead to new strategies for preventing viral illness, and to increased understanding of why some individuals are more resistant to certain kinds of viral infection than are other individuals. The discovery was made by researchers at the National Institute of Health and the University of California at Los Angeles.

Global Warming makes Tundra Greener
Satellite images taken over decades show two seemingly contradictory events that indicate global warming is affecting Alaska. Thousands of satellite images show Alaskan tundra becoming greener, while also indicating that forests stretching from Alaska's interior into northeast Canada are becoming less green. Everyone (assumed) these forests were (also) going to continue to green, and it turns out that there may be other factors that are causing unexpected results, Scott Goetz, a senior scientist at Woods Hole Research Centre in Massachusetts and one of four scientists analysing the satellite data. Alaskan snow researcher Matthew Sturm said some scientists theorise tundra bushes that grow above the snow make the surface darker, accelerating heating by up to 70 percent and, therefore, increasing tundra greening. Ecologist Glenn Juday says that forests are becoming less green because the trees are rapidly drying in the increasing warmth.

Mechanics of foot travel are studied
Despite having the bones and muscles to perform varying gaits, human beings have developed an overwhelming preference for just two: walking and running. Now, scientists analysing simulations of infinite two-legged locomotion have shown the favoured modes of bi-pedal travel use the least amount of energy. Cornell University engineers Andy Ruina and Manoj Srinivasan compared the mechanics of walking and running with other strange and unpracticed gaits. They hoped the study would determine how a person can get from one place to another with the least muscle work, and why people do not walk or run with a smooth level gait. The engineers concluded walking is simply most energy efficient for low speed travel, and running is best at higher speeds. They say a third walk-run gait is optimal for intermediate speeds, but humans do not take advantage of it. The scientists say their findings help to explain why the preposterous -- although possible -- gaits demonstrated in the Monty Python sketch, Ministry of Silly Walks, have never caught on in human locomotion.

Solar System's Baby Pic
Astronomers report detecting gaps ringing the dusty disks around two very young stars, suggesting gas-giant planets have formed there. A team of astronomers using NASA's Spitzer Space Telescope a year ago found evidence of the first baby planet around a young star, challenging most astrophysicists' models of giant-planet formation. The new findings not only reinforce the idea that giant planets, such as Jupiter, form much faster than scientists have traditionally expected, but one of the gas-enshrouded stars, called GM Aurigae, is analogous to our own solar system.
At only 1 million years of age, the star gives a unique window into how our own world may have come into being. The results pose a challenge to existing theories of giant-planet formation, especially those in which planets build up gradually over millions of years, said Nuria Calvet, professor of astronomy at the University of Michigan and lead author of the paper. Studies like this one will ultimately help us better understand how our outer planets, as well as others in the universe, form.

Frozen whole ovaries produce embryos
Israeli scientists working with sheep say they have, for the first time, developed embryos from previously frozen whole ovaries. And the researchers at Israel's Institute of Animal Science believe the procedure could one day work with humans. Scientists seeking to preserve the fertility of women undergoing aggressive cancer treatment have been limited to two options: harvesting, fertilising and then freezing a woman's eggs or freezing and then transplanting strips of ovarian tissue. In both options, the rate of successful pregnancies is low. Human whole ovary transplants have already been attempted twice in women, but neither experiment involved freezing and then thawing the ovary. Dr. Amir Arav and his team tested whether ovaries from eight sheep, together with their blood vessels, could survive a freezing-thawing process, the BBC said, noting sheep ovaries are similar to those of humans. Five of the eight frozen and thawed ovaries were successfully transplanted and two of those ovaries yielded the eggs that made sheep embryos. The scientists say the method must now be tried with humans.

Source: Wired, Science and Webindia123

Compiled by IMRAN H. KHAN


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