Web Date: November 16, 2010
New Tool for Studying Radiation's Effects
Most research on the ecological and human health effects of ionizing radiation has focused on high doses over short periods of time. But chronic exposure to low doses may cause problems too. Researchers presented a new tool to study the consequences of such exposures in living animals at the annual meeting of the Society of Environmental and Toxicological Chemistry (SETAC) in Portland, Oregon on November 10: a transgenic fish that fluoresces in response to radiation-induced changes
Scientists currently have a data gap on how organisms respond to chronic radiation levels in the range of 50 to 70 millisieverts per year. For humans, this range includes the annual maximum allowed for U.S. nuclear workers. For animals, exposures of relatively low radiation levels may occur in environments such as uranium mines and legacy nuclear waste sites. In the U.S. Southwest, bats often nest in abandoned mines.
Recent research has identified a number of effects in cells of doses in this range, including DNA strand breaks. These changes may not kill an animal but they can lead to tissue and organ malfunction. And there is almost no whole-animal data, says Wendy Kuhne, a radiation ecologist at Savannah River National Laboratory's Environmental Science and Biotechnology branch.
So a team of researchers at the Medical College of Georgia led by William Dynan, including Kuhne when she was a postdoctoral scholar at the college, decided to develop an animal model using medaka (Oryzias latipes) fish. They created a transgenic version of the fish in which activation of a gene called 53BP1 leads to expression of a fluorescent protein. The gene, a reporter for DNA strand breaks, becomes active when a cell repairs itself after radiation exposure. The gene is highly conserved among animals, so data collected on the fish will likely apply to human and animal responses to low-level radiation, Kuhne says.
Using the fluorescent proteins as markers, the researchers hope to follow what happens in a living organism to collections of cells after DNA repair. Dynan and his team will focus on identifying mutations or gene rearrangements that occur as the cells grow and undergo division. The medaka model also could help scientists understand how radiation-damaged cells affect nearby cells.
Research biologist Greg Linder of the U.S. Geological Survey hopes that the medaka model can provide results that researchers can extrapolate to animals exposed in the field. He says that data could allow biologists and ecologists to work proactively when making wildlife management decisions near radiation sites.
- Chemical & Engineering News
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