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Oddly, the higher energy radiation also triggered premature graying in the mice, compared to mice exposed to gamma rays. Researchers plan follow-up studies to compare genetic and chromosomal changes from the two types of radiation. In related developments, researchers report progress in developing countermeasures for lower-energy radiation damage. The findings have implications for the treatment of cancer. University of California-Irvine researchers, for example, discussed a protocol involving a cancer-fighting agent called DFMO and a low dose of an anti-inflammatory drug that reduced the risk of reoccurring colorectal polyps, an early sign of colon cancer, by as much as 95 percent with fewer toxic side effects. Colon cancer is the third leading cause of cancer in men and fourth in women in the United States. Fornace said his team focused on colon cancer risks from spaceflight because the disease is already so prevalent in our society that even a slightly elevated risk from radiation exposure could be significant. In finding ways to fight cancer, it is important to understand on a molecular level how different types of radiation damage the body. For example, some compounds show promise in combating damage from conventional radiation but might actually promote malignant cell growth in tissues damaged by high-energy cosmic rays. That's because conventional radiation, like gamma rays or X-rays break down bonds in DNA, the cell's blueprint for reproduction, allowing for interaction with water, which produces free radicals. Cosmic rays behave more like bullets that blast through cells or tissue, creating tracks, as well as surrounding penumbras around the holes that resemble damage from conventional radiation. Medicines and protocols to aid cell healing, such as what would be attempted to repair conventional radiation damage, might also then keep mutated cells alive, triggering tumors, Vazquez said. "One of the main focuses of NASA's program is to attack this problem at different angles," he said. In addition to biological studies, the U.S. space agency is flying instruments on its upcoming Lunar Reconnaissance Orbiter mission to the moon as well as the next Mars rover, slated for launch in 2009, to assess the radiation risks. NASA plans to land astronauts on the moon by 2020. The agency is retiring the shuttle fleet in two years and intends to shift the country's human exploration program beyond the space station, which orbits about 200 miles above the planet, to the moon and beyond. "The big issue is the uncertainty of radiation risks," Fornace said. "We know about Earth-type radiation. What we don't know is what happens in space." Related Links: Irene Klotz's blog: Free Space National Space Biomedical Research Institute |
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