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From: chiaraviglio@husc4.UUCP
Newsgroups: sci.bio,sci.med,comp.ai,sci.misc
Subject: Re: Taking AI models and applying them to biology...
Message-ID: <2222@husc6.UUCP>
Date: Sat, 6-Jun-87 20:28:36 EDT
Article-I.D.: husc6.2222
Posted: Sat Jun  6 20:28:36 1987
Date-Received: Sun, 7-Jun-87 08:42:47 EDT
References: <622@unicus.UUCP>
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Reply-To: lucius%tardis@harvard.harvard.edu (Lucius Chiaraviglio)
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Xref: utgpu sci.bio:343 sci.med:2034 comp.ai:454 sci.misc:269
Summary: Mammalian cells (at least some types) do have a hard limit.

In article <622@unicus.UUCP> craig@unicus.UUCP (Craig D. Hubley) writes:
>I've heard that mammal cells appear to suffer a "hard" reproductive limit
>of 52 mitosis operations, and that meiosis "resets this counter" to 0.
>
>- any comment on this, bio-med types?  Is it true?
>- Would a theory assuming a simple variable or random "counter" in each cell
>limiting its reproductive span better explain aging (programmed cells...)

	Random failure may be a significant factor in aging, but a hard limit
on the number of times a cell may divide before it self-destructs has been
observed in tissue culture, where the cells are for the most part not
dependant on each other.  Those cells which manage to get past the hard limit
are abnormal (although not necessarily cancerous) in ways beyond their mere
ability to keep dividing after they were supposed to self-destruct.  I don't
remember most of the details of this, but I do remember that they tend to
become tetraploid (I think also aneuploid) due to an increase in the rate of
mitotic failure.

	-- Lucius Chiaraviglio
	   lucius%tardis@harvard.harvard.edu
	   seismo!tardis.harvard.edu!lucius