Word: hayflick
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...science cured every known disease of the elderly, you'd add only 15 years to current life expectancy," says Dr. Leonard Hayflick, professor of anatomy at the University of California, San Francisco, and author of How and Why We Age. Accidents and age-related loss of organ function would then start claiming the old--though some, at least in theory, would reach the 125-year mark...
Eight years ago, scientists discovered that the tips of chromosomes in tissue cells shorten each time the cells replicate--until a point is reached where the cells stop dividing altogether. That point, called the Hayflick limit, comes after about 50 replications, and may be at the heart of the process we call aging...
...reactivate the enzyme that lengthens the tips, known as telomeres. Last January they succeeded: Andrea Bodnar and colleagues from the Geron Corp. in Menlo Park, Calif., activated the enzyme telomerase, extended the telomeres and lengthened the life-span of cells in culture by at least 20 divisions past the Hayflick limit. In November, Geron scored another first by reconstituting the telomeres of embryonic stem cells, which are renowned for their ability to turn into any type of cell, making it theoretically possible to rejuvenate parts of any organ with a simple injection...
...telomeres weren't completely inert. One thing they almost always appeared to do was grow shorter. Each time a cell divided, the daughter cells it produced had a little less telomere to play with. Finally, when the cell reached its Hayflick limit of 100 or so replications, the telomere was reduced to a mere nub. At that point, the cell quit replicating. Once it did, researchers theorized, the genes previously covered by the telomere became exposed and active, producing proteins that triggered the tissue deterioration associated with aging...
...moment telomerase was discovered," says Hayflick, "it was clear that for immortal cells at least, this was a way to circumvent the inevitability of aging and dying." Telomerase has now been found in the precursor cells that give rise to human eggs, in the stem cells that give rise to blood cells and in up to 95% of cancer cells...