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Officials last week revealed that the U.S. contribution to ITER could cost $3.9 billion by 2034—roughly four times the...
An experimental hepatitis B drug that looked safe in animal trials tragically killed five of 15 patients in 1993. Now,...
Using the two high-quality genomes that exist for Neandertals and Denisovans, researchers find clues to gene activity...
A new report from the Intergovernmental Panel on Climate Change (IPCC) concludes that humanity has done little to slow...
Astronomers have discovered an Earth-sized planet in the habitable zone of a red dwarf—a star cooler than the sun—500...
Three years ago, Jennifer Francis of Rutgers University proposed that a warming Arctic was altering the behavior of the...
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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Radiation's Long Reach
7 September 2005 (All day)
Zapping human tissue with radiation damages even cells surprisingly far away from those directly hit, a new study shows. The experiment is the first to show that a mysterious "bystander effect," first seen in cell culture, also happens in tissue. The findings may bolster the view that low dose radiation is more dangerous than has been assumed.
In 1992, radiation biologists first noticed in experiments with cultured cells that ionizing radiation harms more than the cells it hits--nearby cells also suffer chromosomal damage. Later work suggested that a DNA-harming substance formed by radiation was diffusing through the culture medium to other cells. But it wasn't known whether the same thing happens in tissue, in which cells are packed close together in three dimensions and communicate through different mechanisms. To find out, David Brenner and coworkers at Columbia University in New York City applied alpha-particle radiation to a tiny volume in samples of artificially grown human skin. They then measured two endpoints for radiation effects: apoptosis, or programmed cell death; and micronuclei, which are fragments of damaged chromosomes that have broken off from a cell's nucleus.
These signs of damage were found in cells up to 1 millimeter, or 50 to 75 cell diameters, from the targeted cells--"which is a jolly long way," says Brenner, whose study appears online this week online in Proceedings of the National Academy of Sciences. The bystander cells suffered less damage than those directly hit, but the average rate of apoptosis in the bystanders was still 2.8 fold higher compared to control tissue and 1.7-fold higher for micronuclei. Brenner suspects a distress signal triggered by radiation moves from cell to cell through "some type of relay system."
"It's quite interesting and important" to see the bystander effect in tissue, says radiation biologist William Morgan of the University of Maryland, Baltimore. The results suggest that low dose radiation may be more dangerous than has been estimated from calculations based only on directly hit cells. Nobody yet knows whether bystander effects are beneficial or harmful overall, however, Morgan notes. Cells with mutations could eventually turn cancerous, but if all the damaged cells die, then the bystander effect could protect against cancer.
For now, Morgan says, the Columbia group--which used relatively high doses of radiation--needs to see if the results hold up at much lower radiation doses. Brenner's team is doing just that by irradiating skin tissue with a single alpha particle.
Information on low dose radiobiology from the Department of Energy
Recent report on low dose radiation risks from the National Academies
Site on the debate about whether low dose radiation is beneficial