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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.

SAN FRANCISCO, June 9 (Xinhua) -- Hewlett-Packard Co. (HP) on Thursday announced that its tablet computer, HP TouchPad, will go on sale in the United States on July 1.Two versions of HP TouchPad, with the option of either 16 gigabytes or 32 gigabytes of internal storage, and both only with Wi-Fi connection, will be available in the United States for 499. 99 U.S. dollars and 599.99 dollars respectively, the company said in a statement.The product will hit stores in Britain, Ireland, France and Germany a few days later and in Canada in mid-July, with availability scheduled to follow later this year in Italy, Spain, Australia, China's Hong Kong, New Zealand and Singapore.Preorders in North America and Europe will begin on June 19, HP said.HP did not release the price details when it introduced TouchPad on Feb. 9. The black device, with a 9.7-inch touch screen, runs webOS operating system, a mobile platform developed by Palm, a smartphone maker acquired by HP last April for 1.8 billion dollars.

WASHINGTON, June 20 (Xinhua) -- The U.S. Food and Drug Administration (FDA) on Monday unveiled in a report a new strategy to meet the challenges posed by rapidly rising imports of FDA- regulated products and a complex global supply chain.The report, titled "Pathway to Global Product Safety and Quality," calls on the agency to transform the way it conducts business and to act globally in order to promote and protect the health of U.S. consumers.According to the report, the FDA will partner with its counterparts worldwide to create global coalitions of regulators focused on ensuring and improving global product safety and quality. The coalitions of regulators will develop international data information systems and networks, and increase the regular and proactive sharing of data and regulatory resources across world markets.The FDA will build in additional information gathering and analysis capabilities with an increased focus on risk analytics and information technology. It increasingly will leverage the efforts of public and private third parties and industry and allocate FDA resources based on risk."FDA regulated imports have quadrupled since 2000. The FDA and our global regulatory partners recognize this new reality and realize we must work proactively and collaboratively to address the challenges we face," FDA Commissioner Margaret Hamburg said in a statement. "The FDA must further collaborate and leverage in order to close the gap between our import levels and our regulatory resources. This report is an important step in ensuring we are able to fulfill our critical public health mission."

LOS ANGELES, June 20 (Xinhua) -- NASA's Cassini spacecraft has successfully completed its second-closest encounter with Saturn's icy moon Helene, beaming down raw images of the small moon, the Jet Propulsion Laboratory (JPL) said on Monday.At closest approach on June 18 Cassini flew within 4,330 miles (6,968 kilometers) of Helene's surface, the second closest approach to Helene of the entire mission, said JPL in Pasadena, Los Angeles.This flyby will enable scientists to finish creating a global map of Helene, so they can better understand the history of impacts to the moon and gully-like features seen on previous flybys, according to JPL.Passing from Helene's night side to the moon's sunlit side, Cassini also captured images of the Saturn-facing side of the moon in sunlight, a region that was only illuminated by sunlight reflected off Saturn the last time Cassini closely encountered with the moon in March 2010.The closest Helene encounter of the mission took place on March 10, 2010, when Cassini flew within 1,131 miles (1,820 kilometers) of the moon.The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.JPL, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL, while the imaging team is based at the Space Science Institute in Boulder, Colorado.

SHENZHEN, June 4 (Xinhua) -- Chinese scientists who have fully sequenced the genome of the new E. Coli spreading through Europe said Saturday they found genes in the bacteria that gave it resistance to eight classes of antibiotics.Researchers with the Beijing Genomics Institute, the world's largest DNA sequencing center, have found genes in the newly identified 0104 strain of E. Coli bacteria that made it resistant to major classes of antibiotics including sulfonamide, cephalothin, penicillin and streptomycin.This helped explain why doctors in Europe had difficulties in fighting the bug that has killed 18 people and sickened nearly 2,000, BGI's major research arm in Shenzhen said on its website Saturday.This would help doctors choose right medicines for the treatment, it said.The researchers are developing a diagnostic kit which will be used to detect the bacteria and prevent the epidemic from spreading further.The Chinese researchers obtained DNA samples of the bacteria from collaborating scientists in Germany and fully sequenced its genome in three days this week.They announced on Thursday the E. Coli spreading through Europe was "a new strain of bacteria that is highly infectious and toxic".The 0104 strain of E. Coli was not previously involved in any E. Coli outbreaks. However, it has 93 percent sequence similarity with the EAEC 55989 E. Coli strain which was isolated in the Central African Republic and known to cause seriously diarrhea, BGI said.The source of the outbreak is unknown, but scientists say it is highly likely to have originated in contaminated vegetables or salad in Germany.

来源：资阳报