Must an AGING PROCESS be universal? was Defining...
Andrew K. Groves
grovesa at starbase1.caltech.edu
Sat Apr 1 17:28:02 EST 1995
In article <LmcfvATLBh107h at chambers.ak.planet.co.nz>,
steve at chambers.ak.planet.co.nz (Steve Chambers) wrote:
> > But such diseases are not ageing.
> This is exactly the point of my original post. Why not?
> > I think that there is confusion therefore, between ageing, which could
> > very well be a single process with pleiotropic effects, and the
> > accumulation of environmental wear and tear which is cleary multifactorial
> Why should wear and tear processes not be considered aging? I think you
> may have missed the point - if there are enough of these "second law" and
> "imperfect gene" type processes (are certainly more than 100 of these)
> then we have no need of a single underlying aging process. There MAY
> be one, but why should we assume it? That's not good science.
I think there is a confusion here between biological ageing and
pathological conditions which lower life span - between cellular and
organismal aging, if you will. If you place a population of human
fibroblasts in culture, they will divide for a certain number of times and
stop. They will not die, they'll just sit there. If you're skilful, you
can maintain such senescent cultures for months and even years. But the
point is that those cells have all stopped dividing after a seemingly
pre-programmed period of time. How could random wear and tear account for
such an impressive synchrony of withdrawal from the cell cycle?
I'm not suggesting that senscence has a single cause - indeed, the work of
Olivia Pereira-Smith would suggest that there are several mechanisms on
the basis of genetic complementation in somatic cell fusion experiments.
Your "100+" mechanisms of wera and tear may well explain why people die,
or get cancer or whatever, but they may not be able to account for the
reproducible obseravtion of cellular senescence.
Division of Biology, 216-76
California Institute of Technology
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