Re: cancer rates

From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Sun Sep 14 2003 - 15:09:36 MDT

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    On Sun, 14 Sep 2003, Charles Hixson wrote:

    > I thought that skin and gut cells needed the capability to divide
    > indefinitely. I.e., that unpredictable environmental insults might
    > cause any particular skin or gut cell to need to divide an extremely
    > large number of times, sufficiently numerous that teleomere maintenance
    > was necessary.

    Replacement of epithelial cells varies from tissue to tissue --
    in part depending on how difficult the environment they are
    exposed to is -- air is a less difficult environment than say
    stomach acid. Replacement times of the surface area cells can
    be as little as 3 days or as much as a few weeks I believe.

    > If so, then *SOME* cells had better not have their ability to regenerate
    > teleomeres knocked out.

    My impression is that the stem cells in epithelial tissues have a limited
    ability to regenerate their telomeres. Whether this is "optimal"
    is questionable. This may explain why wound healing becomes slower
    with age or why it becomes more difficiult to absorb sufficient
    nutrients as one ages.

    Too much telomere regeneration probably ups the cancer rate.
    Too little telomere regeneration has various negative consequences
    as the cells become senescent and cease to renew themselves.
    One ends up caught between a rock and a hard place.

    R.



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