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  health > aging > story pageAIDSAgingAlternative MedicineCancerChildrenDiet & FitnessMenWomen

Science takes cellular approach to explore aging process

January 4, 2000
Web posted at: 11:57 a.m. EST (1657 GMT)


In this story:

What it takes to stop aging

Research: new life for old cells

Cells damaged through oxidation

Preventing cell damage


(CNN) -- Carl Nolting, still working and vigorous at 78, seems to have found the fountain of youth and in the coming millennium, experts say, many more of us will join him with long, active lives. Immortality, though, may take a little longer.

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Living with aging

Nolting, a financial planner from Florida, follows a regimen of exercise and healthy eating, combined with vitamins and hormones, that he credits with keeping him in good shape.

"I can't wait to get to work, I really enjoy it," he told CNN. "And of course, in order to stay young, you've got to have an active body and an active mind."

Nolting hopes his daily routine of physical activity and proper diet will slow down the changes that come with age.

Science, meantime, hopes to discover if anything else will work.

"The real challenge is for us to understand the nature of these changes well enough to try to promote lifestyle behaviors (and) interventions, that will encourage optimal preservation of function and health as aging continues and then try to minimize or interfere with those processes which are detrimental to health," said Richard Hodes, director of the National Institute on Aging.

What it takes to stop aging

But to stop aging, medical science would have to accomplish two very difficult feats, experts maintain.

Firstly, it would need to prevent or repair all accumulated damage in the body.

It would also have to stop or reverse any biological clocks that might set a maximum life-span.

Such clocks exist within our cells, many researchers believe. They're called telomeres -- the tips of chromosomes, the genetic material that determine almost all of our inherited traits.

Telomeres normally wear away each time a cell divides. As a person ages, and their cells have divided many times, the chromosome shortens past the telomere, and starts cutting into working genes.

This interferes with the function of the nucleus, and the cell dies.

Most researchers agree the telomere system evolved to prevent cancer. When cancer cells develop, they divide very rapidly, effectively killing themselves.

But some cancers do keep growing, because they have mutated to produce an enzyme, telomerase, that regrows the telomeres.

Nolting eats right and gets plenty of exercise  

Research: new life for old cells

Researchers at the University of Tennessee-Memphis are using telomerase to give old cells new life. They are growing artificial corneas from real cornea cells. Telomerase allows these cells to keep replicating over and over, something they couldn't do in nature.

Some scientists hope to use the same approach in the cells of the human body. They think it may grant us some youth -- but not eternal youth.

"I don't think that preventing telomere shortening is going to make human beings immortal," says Dr. Woody Wright, a researcher at the University of Texas Southwestern Medical Center at Dallas.

"All that it could do, if we're lucky, and if our hypothesis are correct, is extend the period of vigor, and perhaps the entire human life span," he told CNN.

But most scientists believe the telomere theory does not provide a complete explanation of cellular aging and death.

"Most of the tissues that age ... that we're interested in -- the brain, the heart, the muscle, the kidney, etc. -- those cells never divide at all and they never replicate their nuclear DNA so their telomeres can't get shorter and, therefore, that couldn't affect their longevity," says Dr. Doug Wallace, a molecular biologist.

Cells damaged through oxidation

Wallace and his team of researchers at Emory University in Atlanta are studying another theory of aging based on mitochondria -- the energy-producing portion of a cell.

"The mitochondria make energy by burning hydrogen in the foods that we eat -- our carbohydrates and fats -- with oxygen that we breath from the atmosphere, to make water," Wallace explains.

"In that process they convert that chemical energy into a usable form, which is a carrier molecule called adenosine triphosphate, or ATP," he said.

The instructions on how to make ATP are contained within DNA on the mitochondria's own ring-shaped chromosomes.

Free radicals, a byproduct of making ATP, can damage or kill mitochondria. When one is killed, another mitochondria must divide to replace it. But this process of replication can accumulate mutations throughout all of the replicated mitochondria.

Think of the child's game "telephone," where a short phrase is whispered to the first youngster in a circled group who then turns to the next person and whispers what he thinks he heard.

By the time the message-passing around the circle is complete and the final child repeats the phrase, as he understands it, the wording of the phrase may have been corrupted -- changed along the way -- because a child didn't whisper it clearly, or didn't hear it right.

In this example, the passing of the message from person to person represents mitochondria dividing and reproducing itself.

On the cellular level, such "corruption" might be damage from a stray oxygen molecule.

Each time the cell reproduces itself -- just like when one child repeats the whispered phrase to the next child in the circle -- new errors may arise, and previous errors are repeated.

If enough errors build up as the mitochondria reproduce, the cell will die.

Preventing cell damage

But just restoring defective mitochondria isn't enough to make human beings immortal, says Wallace. "We don't have any way of replacing all the mitochondria, of all the cells in the body. And I don't see any good way of doing that in the near future," he says.

For longer lives, then, we have to prevent the damage from occurring in the first place. "One of the things that we feel might be very important is trying to control the amount of oxygen radical toxicity that occurs from our mitochondria," Wallace says.

For Nolting and health-conscious people like him, the best way to do that is to take anti-oxidants like vitamins C and E, which help clean up free radicals. In short, they may already be doing all they can.

Most aging researchers don't believe we'll find the key to individual immortality any time soon. All we can do for now is live healthy and enjoy our brief lives as much as possible.

Medical correspondent Dr. Steve Salvatore contributed to this report, written by Jim Morris

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