Earlier, I wrote:
>So if this and similar definitions for an aging process won't cut it,
>then what will? I'm not sure, but I offer this as a basis for further
>discussion:
> Any common process with potentially degenerative effects in the
> longer-term.
>There are hundreds, probably thousands of processes that fit this
>definition - and I believe that aging IS this complex.
Many Processes
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This thread appears to have mirrored the vaguaries of evolution and
suffered some form of semantic drift. I originally proposed that
aging (of whole individual organisms) might better be seen as a
complex interaction of many (not-necessarily universal) processes -
many of which are known.
The contention has remained essentially unchallenged and I'm not sure
whether to be flattered by the apparent acceptance of it or disheartened
by the lack of interest.
In the hope of stimulating further debate, I'm going to play devil's
advocate. The following might be seen as evidence against such a
multiple process model of aging:
1) It seems that homo sapiens' maximum lifespan may be double that of
his most immediate ancestor. Some might argue (notably Cutler) that
150,000 years is such a short period of evolutionary history that
advantagous mutations could only have influenced a FEW aging processes.
2) Calorie Restriction has a significant life-extending influence, and it
influences MANY age-related changes. The effect seems to be universal.
Some might offer this as evidence that there are only a FEW (and maybe
only one) underlying aging processes.
3) Recent evidence (eg. Carey et al, 1992; Curtsinger et al, 1992)
suggests that mortality rates may decline in late life of many species.
Some might suggest that this argues against there being MANY aging
processes.
I have no difficulty accomodating these within a multiple process model
but I would be curious to see the opinions of other molbio.ageing readers.
Definition
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My earlier definition of an aging process may have been too all-
encompassing to be useful. I offer this as another option for discussion:
Any common process with the capacity to increase adult mortality,
or degrade adult function, in an age-dependant manner.
Your collective thoughts?
Steve
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(I_lurk,_therefore_I_am!_\ ,,, Steve Chambers
(o o) steve at chambers.ak.planet.co.nz
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(c) Steve Chambers 1995. All rights reserved
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