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Volume 9, Number 15Space holderApril 15, 2005

Mutation allows clams to accumulate more paralytic toxins

Exposure to toxins that cause paralytic shellfish poisoning can result in a mutation that makes some clams more resistant to the toxin and of greater danger to humans, according to a study published in the April 7 issue of the journal Nature.

Paralytic shellfish toxins (PSTs) are produced by algae that appear in certain coastal areas in an event known as an algal bloom, commonly called a red tide. People who eat clams exposed to the PSTs can suffer the paralytic effects of the toxins. There is no cure for the poisoning.

A collaborative team of scientists found that the toxins cause a small mutation that prevents the poisons from binding to sodium ion channels in the clam's nerve tissue. Instead of binding to the ion channels, the toxins build up in the clam. About 100 times more toxin accumulates in the mutated clams than in clams without the mutation.

The toxins could serve as selective agents for sodium ion channel mutations that can prevent toxin binding without otherwise changing the ion channel functions, according to the study.

William Catterall, professor and chair of pharmacology, is one of the study's co-authors. Also participating in the study were other scientists from the University of Washington and the National Oceanic and Atmospheric Administration Northwest Fisheries Science Center in Seattle, the University of Maine, and the Institute for Marine Biosciences in Halifax, Nova Scotia.

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