Capsules

MEMORY HORMONE?

Can a chemical restore lost or weakened memory? In reports to the journal Lancet, scientists suggest that a hormone found in the pituitary gland may have that effect. The remarkable mnemonic is vasopressin, which was previously known to help regulate the body's water content. The levels of vasopressin in the blood appear to decrease after about the age of 50, just when many people begin to complain of failing memories.

The researchers gave male volunteers aged 50 to 65 three sprays of vasopressin in each nostril every day for three days. Similar volunteers who received whiffs of a dummy spray showed no response. But the concentration and memory of those who got the vasopressin improved markedly. Three patients who had suffered impaired memories after auto accidents were given doses for four weeks. One man, 55, was able to remember the dates of his accident, his marriage and other important events that he had been unable to recall before treatment.

SKULL TELEMETRY

The human brain and the rest of the central nervous system are immersed in a bath of cerebrospinal fluid, which must remain at a constant pressure. Anything that causes a significant increase in that pressure--a brain tumor, a hemorrhage, a bad head injury--may be fatal unless the fluid can be drained off in time.

Dr. Nicholas T. Zervas, chief of neurosurgery at the Massachusetts General Hospital, M.I.T. Physicist Eric R. Cosman, and colleagues at Boston's Beth Israel Hospital have now constructed a remarkable sensor that warns of pressure increases by means of radio telemetry. As the investigators explain in the Journal of Neurosurgery, they drill a small hole in the patient's skull and insert a piston so that its base rests on the brain's outer casing. Built into the piston is a miniature induction tuner. If pressure inside the cranium increases, it pushes the piston up a fraction of an inch, thus transmitting a signal to the telemetry receiver at the patient's bedside.

EXERCISE AND INSULIN

An estimated 1.25 million Americans take insulin injections daily. With too little of the life-saving hormone, a diabetic's blood sugar can rise to dangerous levels (hyperglycemia); with too much, the sugar level falls too low (hypoglycemia), and the diabetic may go into a coma.

Still, some diabetics have found that after vigorous exercise their regular injections have the effect of an insulin overdose. Two Yale University researchers, Drs. Philip Felig and Veikko A. Koivisto, offer an explanation for that phenomenon in the New England Journal of Medicine. During exercise, hard-worked muscles need more fuel in the form of blood sugar. But insulin injected in a working muscle defeats that need; the hormone is so rapidly absorbed into the bloodstream that it causes the blood sugar level to drop. The Yale researchers demonstrated this by having patients exercise on a stationary bicycle for an hour after a shot in the leg. Their insulin was absorbed more than twice as fast as it normally would have been. But when these patients were injected in the arm or abdomen, their insulin levels remained normal. The investigators' conclusion: insulin users who plan to exercise should, after checking with their doctors, inject themselves at a site where the muscles will not be heavily taxed. For those in sports like tennis, basketball or skiing, in which leg and arm muscles work hard, the best site is the belly.

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