Rate of aging of young adults

[Excelife]

In article <3620365c.122538298 at nntp.ix.netcom.com>, ufotruth at ix.netcom.com 
says...
>
>Thomas Mahoney,
>
>From what I understand it seems to me that the aging of an individual
>would not have to be caused by a build up of senescent cells for the
>telomeric theory of aging to be valid. We know for a fact that as a
>cell divides up to the limit of around 32 divisions that it "ages".
>Its division rate slows down, several changes takes place, and it
>generally "ages" in negative ways. So it seems to me that a human
>could age, because his cells are aging, without ONE SINGLE SENESCENT
>cell in his body.
>
>Of course a build up of senescent cells could still occur and
>contribute to aging. But it would not be required for telomere
>shortening to be causing aging.
>
>Do you agree or disagree with me?



In discussing replicating cellular systems I would have to disagree.  

In doing a literature search I was unable to find any research that suggest 
there is an age related change in these cells until they, or at least a 
subset of the cells, were of sufficient age or had replicated enough times to 
have reached senescence.

Now relatively few of these studies actually "controlled" for senescence or 
replicative capacity but the age related changes were all within the time 
frames that we would expect senescence to occur.

In vivo studies of cells in culture do show a "build up" in in-appropriate 
phenotype expression.  "Moreover, senescent cells express genes that have
long-range, pleiotropic effects - degradative enzymes, growth factors, and
inflammatory cytokines. ...the altered differentiation may be critical for
compromising the function and integrity of organs like the skin during
aging.", (Campisi J, J Investig Dermatol Symp Proc 1998 Aug;3(1):1-5, "The 
role of cellular senescence in skin aging.").

This phenomena and the increased time between doublings of a culture are 
consistent with an accumulation of senescent cells.  No other "aging" 
mechanism is necessary to explain these results.

Are there other ways of analyzing this same data?  Of course there are and 
research into many of them are continuing.  From what I can see the telomeric 
theory of aging has the best fit for the available data and has few if any 
contradictory results.  Most other aging theories can not explain all of the 
phenomena seen and/or have contradictory findings in-consistent with their 
premise.


(Note:see my next post regarding aging in non-replicating cells.)




Thomas Mahoney, Pres.
Lifeline Laboratories, Inc.
http://home.earthlink.net/~excelife/index.html