Peter Parsons in Biogerontology

[Muckerheide <muckerheide@attbi.com>]

Friends,



Our friend Peter Parsons has published the following paper.

 

Regards, Jim Muckerheide

Radiation, Science, and Health

===============================



Biogerontology 2002;3(4):233-41



Life span: does the limit to survival depend upon metabolic efficiency

under stress?



Parsons PA.

La Trobe University, Bundoora, Vic. 3083, Australia; Author for

correspondence: P.O. Box 906, Unley, SA 5061, Australia (e-mail:

pparsons@senet.com.au; fax: +61-8-8373-5557)



Survival to old age in natural populations is enhanced by high vitality

and resilience which depends upon substantial homeostasis and energetic

and metabolic efficiency underlain by genes for stress resistance. Under

this assumption increased longevity follows from primary selection for

stress resistance where stress targets energy carriers. Furthermore old

and young fitness should be correlated irrespective of age under the

stressful selection regime of natural populations. In contrast,

antagonistic pleiotropy is most likely under the less rigorous selection

regime of well-nourished humans and laboratory populations surviving to

old age. Similarly, hormesis for longevity, for example from a mild

temperature stress or restricted food intake is most likely under benign

environmental conditions. Assuming that aging in natural populations

depends upon ecological circumstances, large evolutionary increases in

life span are unlikely under the stress theory of aging since organisms

are frequently close to their limits of survival where metabolic

efficiency is at a premium. Exceptions can occur in island populations

and for mutants under laboratory conditions since the risks from

environmental hazards are reduced, and life span becomes extended as a

consequence. In modern human populations, selection for stress

resistance is less intense than in earlier times which should be

permissive of the accumulation of stress-sensitive mutants under the

mutation-accumulation theory of aging. However, this process is

ultimately likely to restrict the evolution of life-span extensions in

the future especially if abiotic conditions deteriorate, when survival

would depend more directly on metabolic efficiency under stress.



http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&;

list_uids=12232505&dopt=Abstract





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