Andy - my point is that, until proven differently, aging should be considered
universal. Some cells may divide quite a few times, but will eventually stop
and die. Strange enough, evolution has not shown an escape from this route.
When aging would depend on a single gene this gene should have become mutated
sooner or later, producing a real immortal line. This seems not to have
happened. So aging could either depend on a lot of genes or there is
some unknown factor limiting the potential to divide and live forever.
I understand that in a nematode (Caenorhabditis elegans) some mutants have been
found that live longer, which was correlated with increased free radical
scavenging. Free radical damage thus could be the factor limiting the
lifespan of the wildtype, but the individuals of the mutants still die which
suggests (a series of) other limiting factors.
Wouter van Doorn
ATO-DLO, Wageningen, Holland
