X-Message-Number: 8439
From:  (Thomas Donaldson)
Subject: Re: C57BL/6J mice and aging
Date: Mon, 4 Aug 1997 00:26:18 -0700 (PDT)

Hi again!

I sit here and write this by memory alone, with a bit of consultation of
my own book. 

1. It is not strictly correct to call one set of animals, which live for a 
   long time, "controls" in other experiments. Yes, C57BL/6J mice do live
   a long time. A significant number of the experiments Doug cites were
   NOT done with C57BL/6J mice, so that the MEANING of his bibliography
   becomes obscure. 

2. Although work to identify the genes which affect lifespan in mammals has
   as yet not gone long enough for any conclusions, it's clear that genetics
   plays a large role. The easiest way to see this is to observe other
   species all of which live for widely varying lifespans. Moreover the 
   number of genes affecting lifespans is probably small, since closely 
   related species can have wide differences in lifespan. Chimpanzees only
   live half as long as human beings, for instance.

3. OK, so C47BL/6J mice live a long time, for mice. This is likely to be
   caused by their inheritance of alleles for lifespan genes which make
   them live longer. Similar genes may well work with human beings. 
   However a drug can still act against aging even if it does not increase
   the lifespan of someone with very good lifespan genes: it makes up
   for their absence in most people who take it, and may very well do 
   so by affecting the same metabolic events that good lifespan genes
   affect. (There's lots of research to be done here, people ... its not
   enough just to show that a drug increases lifespan. We want to  know
   WHY).

   Naturally if the drug partially substitutes for the lack of good
   genes, someone who had such genes would not be affected by it. The
   same, of course, may be said of mice.

4. Such drugs may also help people (or mice?) who aren't as resistant
   as others to common pollutants, etc etc. That issue slides off into the
   issue of aging, but can still be distinguished from it intellectually.
   And since no one can live in a perfectly clean unpolluted environment,
   extra antioxidants etc may be very useful --- even if they DON'T
   act directly against aging.

			Best and long long life,

				Thomas Donaldson

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