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. Contaminants May Cause Renal Lesions In Polar Bears

File photo: A Polar Bear.
by Staff Writers
Washington DC (SPX) May 16, 2006
Polar bears from East Greenland contain the highest recorded concentrations of organohalogen contaminants (OHCs)--more than any mammalian species in the world. Researchers in a new study suggest that these air- and seaborne chemicals could be part of the reason why this subpopulation has developed renal lesions. The study is published in the Environmental Toxicology and Chemistry.

The significance of the renal lesions is not well understood. This study provides the first evidence of adverse effects to polar bears from long-term exposure to OHCs, which include DDT, polychlorinated biphenyls (PCBs), and polybrominated diphenylethers (PBDEs).

PCBs and PBDEs are known for their ability to act as flame retardants. These compounds have hundreds of uses in such products as electronic circuit boards and cases, furniture, building materials, pesticides and lubricants.

Among the 75 polar bears examined in the study, seven different types of renal lesions were found. Six of the seven types were related to age.

However, because the lesions were similar to those of OHC-contaminated Baltic seals and other exposed laboratory animals, the authors decided that OHCs were a cofactor in the development of the renal lesions. Metals and recurrent infections were not ruled out as other possible factors.

In polar bears, OHCs are transferred from mother to fetus and to offspring by lactation. The study forms the basis for research on other OHC-contaminated wildlife and raises the possibility of OHC transfer to human populations who rely on what may be contaminated food sources in the Arctic.

Related Links
Society of Environmental Toxicology and Chemistry

Non-Coding RNAs Help Silence The Mammalian Transcription
Cold Spring Harbor NY (SPX) May 15, 2006
Dr. Shirley Tilghman and colleagues (Princeton University) lend new insight into the mechanism of genomic imprinting, demonstrating a necessary role for a non-coding RNA transcript in the silencing of an imprinted gene cluster in mice.

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