X-Message-Number: 8502
From:  (Thomas Donaldson)
Subject: Re: CryoNet #8476 - #8482
Date: Fri, 29 Aug 1997 10:16:04 -0700 (PDT)

Hi again!

About Geron and telomerase, etc:

If we assume that the Hayflick limit (normal cells only divide a maximum of
about 45 times, after which they die off) relates to our own aging and 
death, then discoveries about telomerase do have lots of weight.

HOWEVER as yet that is not a justified assumption. For instance, David
Harrison, not using cell cultures but transplanting from mouse to mouse 
instead, has kept mouse skin alive for much longer than any cell culture, 
and with more cell divisions.

Furthermore, when we start talking about organs (including skin) rather
than cell cultures, some obvious possibilities need to be taken into 
account. For instance, considering skin, we may have a very small proportion
of "stem cells" which CAN divide indefinitely, and as skin cells die off
they are replaced by others which are younger and have had many fewer 
divisions. Such cells may prove hard to find, other than by examining 
the results. It's interesting that stem cells even exist close to our brains,
and produce new neurons when properly stimulated. (I discuss this work, with
references, in the July 1997 PERIASTRON). 

All this is beside the possibility that the cell cultures simply don't
receive required hormonal stimulation etc etc. 

I remain optimistic that we will make many inroads into the problem of
aging and death within the next 10 years. But we should not nail our banners
to one particular notion of why they happen just yet. Geron may end up 
decisively DISPROVING Hayflick's theory --- not that their results may 
prove useless at all, but they may only help us against cancers.

			Long long life,

				Thomas Donaldson

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