Itching to know why man ages? Mosquitoes may help us find out - up front - free radical theories

A University of Louisville biochemist by the name of John P. Richie Jr. has lengthened the average life span of female mosquitoes from 29 to 45 days. Why? Surely not to give them more time to suck our blood? What a terrible idea -- unless, in the process, Richie can find a way to give people greater longevity, too.

The mosquito Aedes aegypti was fed nordihydroguaiaretic acid (NDGA), a substance that's plentiful in the creosote bush, a desert shrub with an unusually long life span. In both bush and mosquito, NDGA is thought to lengthen life by trapping potentially pernicious free radicals. These are chemically active molecules or atoms with an unpaired outermost electron, and are generated in several ways -- by radiation, various drugs, excessive iron in the diet, sunlight, ozone, and even

pure oxygen.

While many free radicals in living organisms are stable, others react indiscriminately with components of cells -- causing mutations in DNA by tangling its base pairs, for example, or breaking down cell walls by reacting with the fats and proteins in them. An organism's repair mecha- nisms undo some of the damage done by radicals. And scavengers -- vitamin E, for one -- neutralize some free radicals by passing them the electron they're missing. But other radicals slip by and continue their dirty work.

In fact, enough radicals slip by that some scientists hold them responsible for the aging process. This is far from an established view, to be sure. Theories of aging are numerous and varied: there are theories that blame aging on the deterioration of DNA and bodily proteins; theories that attribute aging to the decline of the endocrine or immune systems; theories that posit that aging is genetically programmed into our development from birth; and composite theories, which combine elements of the other ideas.

But now the free radical theory has an advantage over the rest: the evidence of about 1,200 long-lived mosquitoes that have spent their extra days of life in

Richie's laboratory.

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