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5 December 2013 11:26 am ,
Vol. 342 ,
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Radiation's Collateral Damage
26 April 1999 7:00 pm
Ionizing radiation can do scary things to a cell's nucleus, shuffling or deleting large chunks of DNA in ways that can turn cells cancerous. Radiation that misses the nucleus and hits only the cell's cytoplasm, however, has seemed harmless. But a study in tomorrow's Proceedings of the National Academy of Sciences suggests ionizing radiation can stir up chemical changes in cytoplasm that lead to DNA damage.
For most people, the risk of absorbing excess ionizing radiation comes mainly through breathing radon, a gas released by uranium and thorium in soils. It may cause up to 21,600 cases of lung cancer each year in the United States. For decades, experts thought the alpha particles released by radon didn't affect the cell's cytoplasm. Then, in the early 1990s, scientists noticed that when they blasted cells with alpha particles, mutations cropped up even in cells that had not been directly hit. Called the "bystander effect," the findings led to speculation that the radiation was creating some agent in the cytoplasm--an unidentified chemical--that then damaged nuclear DNA.
Now scientists have homed in on what seems to be happening. Columbia University's Tom Hei and collaborators dyed hybrid human-hamster cells so they could see the nuclei, then sent a microbeam of alpha particles only to the cell's cytoplasm. Tests showed that the DNA of the cells was damaged, but that the mutations were smaller than would be expected with a nuclear hit--resembling spontaneous mutations. Hei's group suspected that the radiation creates reactive oxygen species that somehow damage DNA. And indeed, adding a solvent to the cells that scarfed up oxygen prevented the mutations.
This kind of injury might be more dangerous than direct nuclear damage because a higher fraction of cells survive, so more cells could eventually turn cancerous, Hei says. But the results don't necessarily mean that radon is any more dangerous than previously estimated. That's because the risk level is set using studies of cancer rates among people exposed to radon--not cellular studies.
"It's an interesting paper. Thought-provoking," muses Helen Evans, a radiation biologist at Case Western Reserve University in Cleveland, Ohio. But she's baffled by how free radicals--which have very short lifetimes and travel short distances--could reach the nucleus of even adjacent cells in time to inflict DNA damage.