From the NY Times (may have to register), more biomedical news:
quote:
Whatever your age, your body is many years younger. In fact, even if you're middle aged, most of you may be just 10 years old or less.
This heartening truth, which arises from the fact that most of the body's tissues are under constant renewal, has been underlined by a novel method of estimating the age of human cells. Its inventor, Jonas Frisen, believes the average age of all the cells in an adult's body may turn out to be as young as 7 to 10 years.
But Dr. Frisen, a stem cell biologist at the Karolinska Institute in Stockholm, has also discovered a fact that explains why people behave their birth age, not the physical age of their cells: a few of the body's cell types endure from birth to death without renewal, and this special minority includes some or all of the cells of the cerebral cortex.
Estimates of tissue aging are based on Carbon-14 enrichment, calibrated against tree rings.
The story also speculates on mechanisms of aging:
quote:
But if the body remains so perpetually youthful and vigorous, and so eminently capable of renewing its tissues, why doesn't the regeneration continue forever?
Some experts believe the root cause is that the DNA accumulates mutations and its information is gradually degraded. Others blame the DNA of the mitochondria, which lack the repair mechanisms available for the chromosomes. A third theory is that the stem cells that are the source of new cells in each tissue eventually grow feeble with age.
Inching ever closer to discovering the fountain of youth...
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I was surprised not to see telomeres mentioned. For any who don't know, telomeres are bits of repetitive DNA at the end of chromosomes. As cells divide, the telomeres shorten, so you can estimate a persons age by the length of their telomeres. I don't know much more than that, except that at least some scientists believe the shortening of telomeres actually has a role in producing old age and in cancer prevention.
Dolly, the cloned sheep, had telomeres of the same length as the 6-year-old sheep she was cloned from. Some scientists believe that this is why she developped arthritis at an early age and died young of complications from lung disease - something more typical for older sheep.
