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WASHINGTON, June 6 (Xinhua) -- A new University of Missouri study shows that the exposure to the controversial chemical Bisphenol A (BPA) through diet has been underestimated by previous lab tests.The findings were published on Monday in Environmental Health Perspectives.In the study, researchers compared BPA concentrations in mice that were given a steady diet supplemented with BPA throughout the day, compared to the more common lab method of single exposure, and found an increased absorption and accumulation of BPA in the blood of the mice.The authors continuously exposed the mice to BPA through their feed, which is considered the primary route of exposure to this chemical in animals and humans. In previous studies examining the effects of BPA, mice were exposed to BPA only through a one-time administration.Following the exposure through the diet, a significantly greater increase in the active form of BPA, which is the greatest threat as it is the form that can bind to sex steroid receptors and exert adverse effects, was absorbed and accumulated in the animals."People are primarily and unknowingly exposed to BPA through the diet because of the various plastic and paper containers used to store our food are formulated with BPA," said Cheryl Rosenfeld, associate professor in biomedical sciences and corresponding lead author. "We know that the active form of BPA binds to our steroid receptors, meaning it can affect estrogen, thyroid and testosterone function. It might also cause genetic mutations. Thus, this chemical can hinder our ability to reproduce and possibly cause behavioral abnormalities that we are just beginning to understand."The study notes that more than eight billion pounds of BPA are produced every year, and more than 90 percent of people in the United States have measurable amounts of BPA in their bodies."When BPA is taken through the food, the active form may remain in the body for a longer period of time than when it is provided through a single treatment, which does not reflect the continuous exposure that occurs in animal and human populations," said Rosenfeld. "We need to study this further to determine where the ingested BPA becomes concentrated and subsequently released back into the bloodstream to be distributed throughout the body."

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, Sept. 12 (Xinhua) -- Amazon.com Inc. is talking with book publishers to launch a rental subscription service for digital books, U.S. media reported on Monday.Several publishing executives said they aren't enthusiastic about the idea because it could lower the value of books and it could also strain their relationships with other retailers that sell their books, The Wall Street Journal quotes people familiar with the matter in a report.The Seattle-based company is considering a digital book library featuring old titles, which would be available to Amazon Prime subscribers, who currently pay 79 U.S. dollars a year for access to digital library of movies and TV shows and unlimited two-day shipping, said the report.Amazon would offer book publishers a substantial fee and could limit the amount of books that Amazon Prime customers could read for free every month, the report cited some sources as saying.The online retailing giant makes the popular electronic reader Kindle and is also reported to launch a color touchscreen tablet before October to compete with Apple's iPad and other devices in the increasingly crowded tablet computer market.The proposal is another sign that retailers are looking for more ways to deliver content digitally as customers increasingly read book and watch TV on personal computers, tablets and other electronic devices, said The Wall Street Journal report.

New York, Sept. 23 (Xinhua) -- A Chinese scientist was presented a prestigious U.S. award on Friday for the discovery of artemisinin, a drug therapy for malaria that has saved millions of lives across the globe, especially in the developing world.Pharmacologist Tu Youyou, 81, became the first scientist on the Chinese mainland to win Lasker Award, known as "America's Nobels" for their knack of gaining future recognition by the Nobel committee.Tu, a scientist at the China Academy of Chinese Medical Sciences in Beijing, pioneered a new approach to malaria treatment that has benefited hundreds of millions of people and promises to benefit many times more. By applying modern techniques and rigor to a heritage provided by 5000 years of Chinese traditional practitioners, she has delivered its riches into the 21st century."Not often in the history of clinical medicine can we celebrate a discovery that has eased the pain and distress of hundreds of millions of people and saved the lives of countless numbers of people, particularly children, in over 100 countries," Lucy Shapiro, a member of the award jury and professor of Stanford University, said while describing Tu' s discovery.Shapiro said the discovery, chemical identification, and validation of artemisinin, a highly effective anti-malarial drug, is largely due to the "scientific insight, vision and dogged determination" of Professor Tu and her team. She thought Professor Tu's work has provided the world with arguably the most important pharmaceutical intervention in the last half century."The discovery of artemisinin is a gift to mankind from traditional Chinese medicine," Tu said while receiving the award. "Continuous exploration and development of traditional medicine will, without doubt, bring more medicines to the world."