Vaughn Gehle has explained that C. Elegans has no cell division in
the adult form (except in the germ cells); and he comments that this
makes it a good model for the ageing of the mammalian brain.
I would add also for mammalian muscle tissue.
However, I would still qualify this with the observation that
in both tissues there are supporting cells, such as glia and
astrocytes which do divide, and which may contribute to the decrease
in functional ability of the ageing brain. But, essentially I think
that his point is very strong. It really does give pause for thought
for the telomerase hypothesis.
It also raises the question of what do we say about the rest
of the mammalian body, in which there is active cell turnover. My
response is that we should view ageing in mammals as two partly
separate problems; ageing of post-mitotic tissues like brain and
muscle, on the one hand, and ageing of all the other tissues in which
there is cell reolication and tissue turnover. Fot the non-dividing,
post-mitotic tissues like the neurones and muscle there are good
models in C. elegans and Drosophila melanogaster. For the tissues
that can regenerate, that is in which the cells continuously are
dividing, the best current model may be the growth of normal, mortal
cell strains in vitro; by which I mean the study of the so-called
Hayflick limit.
Finally, I should like to ask the C. elegans people the
specific question; in the long-lived C. elegans mutants have you
looked to see whether there is (unexpectedly) any cell division? It
seems to me very important to establish experimentally that in C.
elegans one is *ALWAYS* looking at post-mitotic cells. A
sub-question would be whether the number of cells in the adults of
long-lived mutants are different to the wild-type; the question is
whether the mutant gene has an execution point in the larval stages.
Sydney
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Sydney SHALL,
Laboratory of Cell and Molecular Biology,
Biology Building,
University of Sussex,
Brighton,
East Sussex BN1 9QG,
ENGLAND.
Telephone: +44.273.67.83.03
FAX: +44.273.67.84.33
E-Mail:
Janet: S.Shall at uk.ac.sussex
Elsewhere: S.Shall at sussex.ac.uk
EARN/BITNET: S.Shall%sussex at ukacrl
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