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WASHINGTON, June 16 (Xinhua) -- Cells in the human body are constantly being exposed to stress from environmental chemicals or errors in routine cellular processes. While stress can cause damage, it can also provide the stimulus for undoing the damage. New research by a team of scientists at the University of Rochester has unveiled an important new mechanism that allows cells to recognize when they are under stress and prime the DNA repair machinery to respond to the threat of damage.Their findings will be published Friday in journal Science. Cells in the human body are constantly being exposed to stress from environmental chemicals or errors in routine cellular processes. While stress can cause damage, it can also provide the stimulus for undoing the damage.The scientists, led by biologists Vera Gorbunova and Andrei Seluanov, focused on the most dangerous type of DNA damage -- double strand breaks. Unrepaired, this type of damage can lead to premature aging and cancer. They studied how oxidative stress affects efficiency of DNA repair. Oxidative stress occurs when the body is unable to neutralize the highly-reactive molecules, which are typically produced during routine cellular activities.The research team found that human cells undergoing oxidative stress synthesized more of a protein called SIRT6. By increasing SIRT6 levels, cells were able to stimulate their ability to repair double strand breaks. When the cells were treated with a drug that inactivated SIRT6, DNA repair came to a halt, thus confirming the role of SIRT6 in DNA repair. Gorbunova notes that the SIRT6 protein is structurally related to another protein, SIR2, which has been shown to extend lifespan in multiple model organisms."SIRT6 also affects DNA repair when there is no oxidative stress," explains Gorbunova. "It's just that the effect is magnified when the cells are challenged with even small amounts of oxidative stress."SIRT6 allows the cells to be economical with their resources, priming the repair enzymes only when there is damage that needs to be repaired. Thus SIRT6 may be a master regulator that coordinates stress and DNA repair activities, according to Gorbunova.

TAIYUAN, May 29 (Xinhua) -- Parents of children with cerebral palsy are going to have a place to turn for help, as the first public foundation to provide aid has been set up in northern Shanxi Province.The Brain Rehabilitation Fund was established on Saturday by the China Population Welfare Foundation (CPWF), which is headquartered in Beijing. The CPWF will cooperate with the Shanxi Cerebral Palsy Hospital, which specializes in curing the brain disease with therapies such as acupuncture and massage.Lan Ye, the deputy secretary general of the CPWF, said the fund aims to relieve the burden of affected families by providing financial assistance and training so parents are able to do the therapy at home. In addition, the fund hopes to reduce the incidence of cerebral palsy by publicizing preventative measures to thwart the disease.More than 6 million suffer from cerebral palsy in China, and among them more than 2 million are children, said Guo Xinzhi, vice president of the Shanxi's Federation of the Disabled."A family needs to spend more than 500,000 yuan (77,000 U.S. dollars) to cure a child with the disease," Guo said. "As 70 percent of the children with cerebral palsy are from poor, mountainous areas, more than 25.7 percent of families cannot afford to pay the medical expenses."On Saturday, 25 parents from Xinjiang Uygur Autonomous Region, Fujian, Henan and Shanxi provinces came to the hospital for free training on helping their children to recover at home.

WASHINGTON, Aug. 31 (Xinhua) -- Astronomers using NASA's Chandra X-ray Observatory discovered the first pair of supermassive black holes in a spiral galaxy similar to the Milky Way, NASA announced Wednesday.Approximately 160 million light years from Earth, the pair is the nearest known such phenomenon.The black holes are located near the center of the spiral galaxy NGC 3393. Separated by only 490 light years, the black holes are likely the remnant of a merger of two galaxies of unequal mass a billion or more years ago.Both of the supermassive black holes are heavily obscured by dust and gas, which makes them difficult to observe in optical light. Because X-rays are more energetic, they can penetrate this obscuring material. Chandra's X-ray spectra show clear signatures of a pair of supermassive black holes."If this galaxy weren't so close, we'd have no chance of separating the two black holes the way we have," said Pepi Fabbiano of the Harvard-Smithsonian Center for Astrophysics, who led the study that appeared Wednesday in on-line issue of the journal Nature. "Since this galaxy was right under our noses by cosmic standards, it makes us wonder how many of these black hole pairs we've been missing."Previous observations in X-rays and at other wavelengths indicated that a single supermassive black hole existed in the center of NGC 3393. However, a long look by Chandra allowed the researchers to detect and separate the dual black holes. Both black holes are actively growing and emitting X-rays as gas falls towards them and becomes hotter.When two equal-sized spiral galaxies merge, astronomers think it should result in the formation of a black hole pair and a galaxy with a disrupted appearance and intense star formation. A well-known example is the pair of supermassive black holes in NGC 6240, which is located about 330 million light years from Earth.However, NGC 3393 is a well-organized spiral galaxy, and its central bulge is dominated by old stars. These are unusual properties for a galaxy containing a pair of black holes.

BEIJING, Aug. 11 (Xinhuanet) -- Next year will bring a doubling in the size of the words that appear on cigarette packages to warn consumers of the dangers of smoking. Starting in April 2012, cigarettes produced and sold in China will bear a new warning label containing letters that will be no less than 4 millimeters in height. That will be twice the size of the current minimum, which stipulates that the letters be at least 2 mm from bottom to top, according to a notice written by the China National Tobacco Corp and published on the State Tobacco Monopoly Administration's website. Despite the intentions, many tobacco-control experts said the step is "minor" and that it fails to deal with the chief issue. "There is no use in making the font size even 100 times bigger if the warning is pointless," said Wu Yiqun, deputy director of the ThinkTank Research Center for Health Development, a Beijing-based non-governmental organization that advocates for the adoption of stronger smoking-control measures. Both Wu and Yang Gonghuan, director of the tobacco control office of the Chinese Center for Disease Control and Prevention, said the warning that now appears on cigarette packs is too weak. It says: "Smoking is harmful to your health. Quitting early is good for your health." "The package should inform consumers of the dangers of smoking in accordance with requirements adopted by the World Health Organization Framework Convention on Tobacco Control. (It should say that) smoking causes lung cancer, coronary disease and makes people grow old," Yang said. China decided in 2005 to ratify the convention, which also requires that tobacco warnings cover a third of the surface of cigarette packs. "Even if the size of the words is doubled, it still doesn't meet those standards," Yang said. "The Chinese practice is to draw a line to demarcate a third of a cigarette package, where the warning should be, but the words put on it are still very small." Experts said graphic health warnings could be printed on cigarette packs and used as a "scientific, direct and shocking" deterrent to smoking.Throughout the world, more than 1 billion people in 19 countries live under laws that require the packaging of various types of tobacco products to bear large, graphic health warnings. They often show pictures of black lungs and festering mouth sores, according to the World Health Organization. China, though, is excluded from those rules. Both Wu and Yang said the fundamental barrier to better control of tobacco use in the country is the fact that the China National Tobacco Corp, the country's largest cigarette-maker, is a subsidiary of the State Tobacco Monopoly Administration, China's tobacco regulatory body.

WASHINGTON, June 6 (Xinhua) -- The tropics and much of the Northern Hemisphere are likely to experience an irreversible rise in summer temperatures within the next 20 to 60 years if atmospheric greenhouse gas concentrations continue to increase, according to a new climate study by Stanford University scientists. The results will be published later this month in the journal Climatic Change.In the study, the Stanford team concluded that many tropical regions in Africa, Asia and South America could see "the permanent emergence of unprecedented summer heat" in the next two decades. Middle latitudes of Europe, China and North America -- including the United States -- are likely to undergo extreme summer temperature shifts within 60 years, the researchers found."According to our projections, large areas of the globe are likely to warm up so quickly that, by the middle of this century, even the coolest summers will be hotter than the hottest summers of the past 50 years," said the study's lead author, Noah Diffenbaugh, an assistant professor of environmental Earth system science and fellow at the Woods Institute for the Environment at Stanford. The study is co-authored by Stanford research assistant Martin Scherer."When scientists talk about global warming causing more heat waves, people often ask if that means that the hottest temperatures will become 'the new normal,'" Diffenbaugh said. " That got us thinking -- at what point can we expect the coolest seasonal temperatures to always be hotter than the historically highest temperatures for that season?"To determine the seasonal impact of global warming in coming decades, Diffenbaugh and Scherer analyzed more than 50 climate model experiments -- including computer simulations of the 21st century when global greenhouse gas concentrations are expected to increase, and simulations of the 20th century that accurately " predicted" the Earth's climate during the last 50 years. The analysis revealed that many parts of the planet could experience a permanent spike in seasonal temperatures within 60 years."We also analyzed historical data from weather stations around the world to see if the projected emergence of unprecedented heat had already begun," Diffenbaugh said. "It turns out that when we look back in time using temperature records, we find that this extreme heat emergence is occurring now, and that climate models represent the historical patterns remarkably well."According to both the climate model analysis and the historical weather data, the tropics are heating up the fastest. "We find that the most immediate increase in extreme seasonal heat occurs in the tropics, with up to 70 percent of seasons in the early 21st century (2010-2039) exceeding the late-20th century maximum," the authors wrote.Tropical regions may see the most dramatic changes first, but wide swaths of North America, China and Mediterranean Europe are also likely to enter into a new heat regime by 2070, according to the study.This dramatic shift in seasonal temperatures could have severe consequences for human health, agricultural production and ecosystem productivity, Diffenbaugh said. As an example, he pointed to record heat waves in Europe in 2003 that killed 40,000 people. He also cited studies showing that projected increases in summer temperatures in the Midwestern United States could reduce the harvest of staples, such as corn and soybeans, by more than 30 percent.

来源：资阳报