Sound hazard

May 12, 2000

DNA inside living cells may be damaged by low levels of ultrasound. Preliminary research by a team at University College, Dublin, found that some particularly sensitive cells in the guts of mice were affected by the sort of scan used in human medical imaging.

The work, to be published in the journal Life Sciences, raises questions about the safety of a standard procedure that has long been considered harmless.

However, a more detailed investigation by the scientists has failed to attract further funding. The Wellcome Trust recently turned down a grant for Pounds 500,000.

Patrick Brennan, who led the project with Marie Stanton and Raj Ettarh, said: "The exposure to ultrasound has shown an effect on cells. The suggestion that ultrasound is completely harmless needs looking at."

The researchers exposed 12 mice to an 8-megahertz scan for 15 minutes. They then studied what had happened to cells in the small intestine, a particularly sensitive area, as a result of the ultrasound.

The study found that four and a half minutes after exposure, cell division had fallen by 22 per cent while programmed cell death, or apoptosis, had roughly doubled.

Both of these effects could be indications of natural safety mechanisms to deal with genetic damage.

"The fact that ultrasound had slowed up these cells going into mitosis would suggest that there might be DNA damage. The reason for the increased apoptosis could be exactly the same," Dr Brennan said.

In effect, after its DNA has been damaged, a cell might choose to destroy itself rather than create a line of mutants or delay its reproduction in order to correct new genetic errors.

However, Dr Brennan said that the research merely indicated the possibility of an effect and that further work is needed to look at whether cells other than those in the gut were altered before the potential impact on humans is explored.

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