anthropology: rats help track human migration patterns

Posted on June 8, 2004 by agnieszka

Thanks to genetic analysis and the rat-eating habits of ancient Polynesians, researchers are determining the routes prehistoric humans used to colonize the Western Pacific. The Pacific rat (Rattus exulans) is believed to have been a food source for the Lapita, a seafaring culture that existed about 3500 years ago and thought to be the ancestors of Polynesians and other Pacific islanders. In this week’s Proceedings of the National Academy of the Sciences Online Early Edition, E. Matisoo-Smith and J. H. Robins of New Zealand’s University of Auckland note that since the rat does not swim, the only way it could have reached any of the islands was by human canoe, and therefore an analysis of the rat’s DNA could shed light on the origins of both the Polynesians and the Lapita peoples. The researchers compared mitochondrial DNA taken from ancient skeletal remains and modern rats found in the Pacific and Island Southeast Asia. Their results suggest a slower and more complicated pattern of human migration than previously proposed. The researchers write, “Integrating these results with those from other fields such as archeology, comparative linguistics, and molecular biology of human populations will be the only way we can fully understand the complex prehistory of this region.”

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 6/08/2004.
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biomedicine: link between aging and eating found

Posted on June 8, 2004 by agnieszka

Scientists have long known that calorie-restricted diets can extend the lives of creatures ranging from yeast to fruit flies to mice. (A few, very hungry people are trying to see if it works for humans, too.) But exactly why near-starvation diets make animals live longer remains unclear. Now MIT’s Leonard Guarente and colleagues offer a first step in explaining how two such different processes as eating and aging could be related in the June 2 online issue of Nature. In yeast, longevity is promoted by a gene called SIR2. The researchers studied the mouse version of this gene called Sirt1 and discovered that it is activated by scarcity of food. During times of hunger, Sirt1 turns off receptors that lay down fat deposits, preventing the body from storing fat and releasing it to be metabolized. So long life through dieting may involve the body’s fat-deposition machinery. “We’d like to think this applies to people as well as mice, but we don’t know for sure,” stated Guarente in a press release. “If we could make this happen in people, it wouldn’t just make them live longer; it might also help prevent diseases of aging, like cancer, diabetes and heart disease.”

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 6/08/2004.
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epidemiology: stressed caregivers don’t face higher risk of breast cancer

Posted on June 1, 2004 by agnieszka

It’s long been thought that stress might be a factor in the development of breast cancer, but a study in the June 1 issue of the American Journal of Epidemiology suggests otherwise. Candyce Kroenke of Brigham and Women’s Hospital and Harvard Medical School presents evidence that the long-term stress of caregiving does not appear to increase the risk of breast cancer. She and her colleagues tracked 69,886 women ages 46 to 71 over a period of eight years. Out of that number, 1,700 developed breast cancer. The team found that women who spent more hours caring for a disabled or ill adult or child, and reported higher levels of stress, did not have a higher incidence of breast cancer. Instead, they found that women who were caregivers more than 15 hours a week had relatively low levels of sex steroid hormones, suggesting that chronic stress could possibly lower breast cancer risk. Kroenke stated in a press release that she hoped the research would “be reassuring to women.”

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 6/01/2004.
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astrophysics: dark energy fuels expanding universe

Posted on May 25, 2004 by agnieszka

A new study using NASA’s orbiting Chandra X-ray Observatory seems to confirm the existence of dark energy, which may have implications for the ultimate fate of the universe. Dark energy is a mysterious force pushing the universe apart as well as accelerating its expansion, and remains “perhaps the biggest mystery in physics,” according to study leader Steve Allen from the Institute of Astronomy at the University of Cambridge in England. Allen and his team used the Chandra telescope to study 26 clusters of galaxies located 1 billion to 8 billion light years away. The researchers measured the distances to the clusters, and then by plotting those distances over time, they determined that the expansion of the universe started speeding up about 6 billion years ago. This acceleration, they state, is due to dark energy. Study coauthor Andy Fabian, also from the Institute of Astronomy, stated in a press release: “The new Chandra results suggest the dark energy density does not change quickly with time and may even be constant.” If it does remain constant, the universe is expected to expand forever. The team’s findings also agree with other estimates that dark energy makes up about 75 percent of the universe. The study will appear in a forthcoming issue of the Monthly Notices of the Royal Astronomy Society.

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 5/25/2004.
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reproduction: frozen sperm works as well as fresh in IVF

Posted on May 18, 2004 by agnieszka

Researchers have long been concerned that using frozen sperm instead of fresh to create test-tube babies might reduce the chances of a successful pregnancy for an infertile couple. But a Mayo Clinic study presented last week at the annual meeting of the American Urological Association reveals that frozen sperm is just as effective for in vitro fertilization, or IVF, where sperm is allowed to fertilize an egg in a lab dish, and the resulting embryo is implanted within a woman’s uterus. After reviewing 10 years of data collected at the Mayo Clinic and comparing birth rates from IVF attempts, researchers found that the likelihood of a successful pregnancy was the same, whether the sperm used was fresh or frozen. Though the clinic’s doctors still prefer to use fresh sperm, since freezing and thawing reduces sperm number and motility, couples can now rest easily, knowing they’re not jeopardizing their chances of pregnancy if fresh is not available. “The in vitro process is long and can be difficult — emotionally, physically and financially. These results make the process just a little bit easier,” the study’s senior author, Alan Thornhill, director of the clinic’s IVF lab, stated in a press release.

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 5/18/2004.
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astronomy: photo may show another world

Posted on May 18, 2004 by agnieszka

Astronomers from Pennsylvania State University may have taken the first photo of a planet circling a distant star. Though many planets outside our solar system have already been discovered, this would be the first time another world has ever been photographed directly. The difficulty is that the much brighter light of host stars usually obscures fainter objects, such as planets. So, using the Hubble Space Telescope’s infrared camera, the researchers looked for planets circling white dwarfs, dimmer stars near the end of their lives. They hope that the small blob (white dot at upper right) circling the star in the photo they’ve taken is a planet, and not just a background object in the same field of view. However, the researchers won’t be able to confirm their discovery until more observations are done over the next six months. If it is a planet, the object is 5- to 10-times the mass of Jupiter, and orbits a star about 100 light years away. Nature News Service reports that the astronomers won’t reveal the star’s precise location because they fear other researchers may scoop their results.

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 5/18/2004.
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environment: microscopic plastic contaminating oceans

Posted on May 11, 2004 by agnieszka

Plastic trash washing up on the remotest islands and accumulating on sea floors is, unfortunately, nothing new, but British researchers have found that even microscopic plastic fibers and fragments are contaminating ocean waters and sediments. In the May 7 Science, Richard Thompson of the UK’s University of Plymouth and colleagues report sampling sediments collected from beaches and estuaries in the northeast Atlantic Ocean. The researchers identified microscopic fragments of nylon, polyester, acrylic, and other types of plastic, which they believe come from the breakdown of larger items, such as clothing, packaging, and rope. Though the researchers acknowledge that more work is needed to establish the actual environmental impact of this debris, they also note that marine organisms, such as barnacles and lugworms, are able to ingest the microscopic plastic fragments, with unknown consequences to the animals or food chains. Thompson and colleagues also have found a significant increase in the presence of plastic fragments compared to samples taken 40 years ago. “Given the rapid increase in plastic production, the longevity of plastic, and the disposable nature of plastic items,” they wrote, “this contamination is likely to increase.”

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 5/11/2004.
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neuroscience: lack of serotonin may mean lack of flexibility in behavior

Posted on May 11, 2004 by agnieszka

Serotonin, an important neurotransmitter, has almost become a household word, thanks to antidepressants such as Prozac and Zoloft, which work to increase serotonin levels in the brain. Yet its precise role in the prefrontal cortex, an area of the brain involved in learning and decision-making, remains poorly understood. Scientists have long thought that there was a link between the brain’s inability to properly regulate serotonin in the prefrontal cortex and various psychiatric disorders, such as schizophrenia and obsessive-compulsive disorder. A study by British researchers in the May 7 Science offers evidence that this may be the case, showing that a lack of serotonin leads to inflexible and repetitive behavior, a symptom of many of these disorders. Hannah Clarke of Cambridge University and colleagues depleted serotonin in the prefrontal cortex of marmoset monkeys. They found that those monkeys tended to repeat certain actions instead of adapting them to new circumstances.

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 5/11/2004.
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archeology: earliest evidence of fire use found

Posted on May 4, 2004 by agnieszka

Israeli researchers have discovered what could be the oldest-known remnants from fires made by humans, suggesting mankind controlled fire nearly 790,000 years ago. In a study published in the April 30 Science, Naama Goren-Inbar of Hebrew University and colleagues report analyzing burned seeds, wood, and flint found at Gesher Benot Ya’aqov, an archeological site in Israel. The distribution and clustering of the burned small flint fragments hints that the fires occurred in specific spots, which may have been hearths. The researchers believe the fires were set intentionally because most of the flint andwood at the site is unburned, suggesting that wildfires were not the cause. Although it’s unclear exactly what species of human set the fires, whether Homo erectus, Homo ergaster or archaic Homo sapiens, the evidence at the site suggests the fire users hunted and processed meat, gathered plant foods, quarried rock, and made stone tools. As the authors write, in what could be construed as an understatement, “The domestication of fire . . . surely led to dramatic changes in behavior connected with diet, defense, and social interaction.”

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 5/04/2004.
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neuroscience: learning from other people’s mistakes

Posted on May 4, 2004 by agnieszka

It appears there’s a reason why watching someone fumble a ball or give the wrong answer on “Jeopardy” can be so annoying. Dutch researchers report in the May issue of Nature Neuroscience that people’s brains react the same way, whether they’re actually making an error or just observing someone erring. Hein van Schie of the University of Nijmegen and colleagues measured the electrical activity of volunteers’ brains as the subjects performed a simple task. The participants had to look at an arrow that appeared briefly on a computer screen, then judge in which direction it was pointing. After each test, the volunteers were told whether they were right or not. When a person realized he or she had made a mistake, a distinctive electrical signal from a part of the brain called the anterior cingulate cortex was recorded, but the researchers found that they got the same brain signal even from people who simply watched the person make the mistake during the same task. The authors hope the finding will help shed light on how we learn from observing our own and others’ mistakes, since, after all, “errors are crucial for learning and adjusting future behavior.”

This news brief appeared in the Discoveries column of the Boston Globe’s Health/Science section on 5/04/2004.
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