Cocaine's effect on brain brings nearly instant addiction.(Chicago Tribune)

The reason some people become addicted to cocaine after a brief exposure is that the narcotic has an uncanny ability to alter brain-cell connections, according to researchers at the University of California at San Francisco.

The pattern of activity produced by a single injection of cocaine lasts 5 to 10 days and is similar to the kinds of changes involved in learning and memory, Dr. Antonello Bonci reported in the British journal Nature. The experiments were conducted in rodents.

"The significance of this finding is that a single dose of cocaine usurped a cellular mechanism involved in a normally adaptive learning process, which may help to explain cocaine's ability to take control of incentive-motivational systems in the brain and produce compulsive drug-seeking behavior," he said.

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Small particles from automobile exhausts, power plants, refineries, smelters and other industry can increase the risk of a heart attack.

A study of 772 Boston area residents who suffered heart attacks found that the attacks were up to 48 percent more frequent when levels of the small particles increased in the air, said Dr. Murray A. Mittleman of the Beth Israel Deaconess Medical Center.

The particles, which measure less than 2.5 micrometers in diameter, ...