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From: levy@ttrdc.UUCP
Newsgroups: sci.bio,sci.med,comp.ai,sci.misc
Subject: Re: Models of biological aging
Message-ID: <1756@ttrdc.UUCP>
Date: Sun, 14-Jun-87 01:20:21 EDT
Article-I.D.: ttrdc.1756
Posted: Sun Jun 14 01:20:21 1987
Date-Received: Sun, 14-Jun-87 21:39:13 EDT
References: <622@unicus.UUCP> <1343@sigi.Colorado.EDU>
Organization: AT&T, Skokie, IL
Lines: 20
Xref: utgpu sci.bio:370 sci.med:2079 comp.ai:476 sci.misc:278

In article <1343@sigi.Colorado.EDU>, eddy@boulder.Colorado.EDU (Sean Eddy) writes:
< Hayflick (1965) did an experiment in which he took cells from
< human embryos and grew them in vitro. He observed that the cells
< would go through about 50 divisions (40-60) and then die. Thus
< this limit of 50 CPD (cell population doublings) is called the
< Hayflick limit. In actual practice, it is not thought that any
< human cell approaches 50 divisions during the human lifetime.

Is this true even for skin cells?  Where DOES all the new skin come
from as the old skin cells constantly die and flake off, then?  (At
least I was under the impression that skin cells do this.  I also once read
an article [Scientific American?] which said, as best as I could understand
it, that intestinal cells continually regenerate and get sloughed off during
the normal digestive process.  That's a lot of cell division, or am I
mistaken?)
-- 
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