医学补充阅读：Cancer Study Sheds Light on Gray Hair[1]

　　by keay davidson

　　friday, december 24, 2004

　　scientists studying a deadly skin cancer have inadvertently found a possible explanation for why hair turns gray.

　　but don't throw out that hair dye. by itself, the finding does not immediately point to a way to prevent graying hair, caution the boston scientists who made the discovery. moreover, the researchers said they're more interested in curing cancer.

　　the finding, published thursday in sciencexpress, the online journal run by science magazine, was an unexpected spin-off of research on melanoma, the deadliest form of skin cancer. the researchers found that hair begins to turn gray when the pigment-producing cells in skin and hair —— also involved in melanoma —— start dying off.

　　"preventing the graying of hair is not our goal," said one team member, oncologist dr. david e. fisher of dana-farber cancer institute. "our goal really is to kill melanoma," he said. but "at this point we still are very early" in our understanding of melanoma, he said.

　　melanoma is the most serious form of skin cancer, one that causes almost 8,000 deaths a year in the united states. overexposure to the sun is a major cause of melanoma, and the disease is known to be particularly resistant to chemotherapy and radiation.　　still, the scientists' discovery is a reminder of how one of life's most familiar and usually lamented events —— the graying of hair —— lacked a clear-cut scientific explanation until now.

　　"hair graying is the most obvious sign of aging in man, yet its mechanism is largely unknown," the scientists wrote in their paper.

　　the other authors are dermatologist dr. emi k. nishimura, also of dana-farber, and pathologist dr. scott r. granter of brigham and women's hospital in boston.

　　historically, some scientists have blamed gray hair on causes that range from stress to genetic factors to smoking and thyroid imbalances. there are many英语口语