Capsules

EXONERATING X RAYS

Does exposure to medical X rays cause cancer, in particular leukemia, a form of the disease long known to be linked with radiation? Doctors have never been able to give a conclusive answer because they lacked records showing how much radiation patients had received. Last week researchers at the Mayo Clinic in Rochester, Minn., said that they have finally overcome this difficulty. Turning to the centralized medical records of Minnesota's Olmsted County, they compared the X-ray dosages of 138 people who developed leukemia between the years 1955 and 1974 and those of 276 other people who had received about the same amount of radiation during routine checkups and minor treatment. The team's finding, reported in the New England Journal of Medicine: medical X rays did not appear to increase the risk of leukemia.

TOO THIN, TOO BAD

"No woman is ever too slim or too rich," goes a popular adage. It may be wrong. Though the obese definitely run greater risks of hypertension, heart attacks, diabetes and other ills, the very thin are not necessarily any healthier. Studying data collected on 5,209 men and women during a 24-year study, National Institutes of Health Epidemiologist Paul Sorlie and his colleagues confirmed that the obese had higher death rates than those of average weight, but they were surprised by similar high mortality rates for the underweight. The finding could not be explained by such factors as the amount of smoking or undiagnosed illness. These results, Sorlie writes in the Journal of the American Medical Association, "raise questions as to the health benefits from weight reduction in persons of average or near average weight."

TRICKY BUG

The bug was so elusive that it took months for scientists to identify it after it struck at an American Legion convention in Philadelphia in 1976. Now, it turns out, the bacterium Legionella pneumophila is even tricker than anyone suspected. Researchers Marcus Horwitz and Samuel Silverstein of Manhattan's Rockefeller University have found that it belongs to a select group of bacteria that evade the body's immune system by turning it to their own advantage. Like the microbes that cause tuberculosis and leprosy, the bug is what scientists dub an intracellular pathogen. It invades white blood cells called monocytes, which normally kill bacteria, and uses material within these cells to propagate--in droves. In one experiment at Rockefeller, Legionella added to a culture of monocytes increased 100,000-fold within days.

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