RE: Additional nematode - heat stress

[Jack_Earley@RL.GOV]

One of the early thoughts on hormesis was that cells perform one of two

functions: repair or rejuvenation. If they're not expending energy in

repair, then they expend it rejuvenating. Sounds like a common thread here.



Jack Earley

Radiological Engineer





-----Original Message-----

From: Thomas J Savin [mailto:tjsav@LYCOS.COM]

Sent: Wednesday, February 13, 2002 10:45 AM

To: radsafe@list.vanderbilt.edu

Subject: Additional nematode - heat stress





Additional data, note the resistance to HEAT - From Science Vol 295 no.5554

pgs502-505.  January 18, 2002





In summary, we have found that the aging process of C. elegans is modulated,

during adulthood, by the activity of germ-line stem cells. How might these

cells affect aging? One possibility is that germ-line proliferation shortens

life-span by increasing energy expenditure, channeling resources that could

otherwise be used for maintaining cellular integrity toward growth and

reproduction. However, there does not appear to be a simple trade-off

between reproduction (or energy expenditure) and aging in this system; for

example, animals that lack the entire reproductive system are not

long-lived. Another possibility is that the role of germ-line stem cells is

simply to produce more germ-line tissue, which then influences life-span

regardless of its state of differentiation. However, the gonads of daz-1

mutants have a much smaller mass than those of glp-1 mutants shifted to high

temperature as adults, because oocyte precursors die instead of becoming

large, mature oocytes (15). Yet !

d

az-1 animals are not long-lived. Therefore the germ-line stem cells may be

uniquely capable of influencing life-span. We propose that stem-cell

proliferation influences life-span by affecting either the production of, or

the response to, a steroid hormone ligand for DAF-12, which, in turn,

promotes longevity. In addition, a signal dependent on stem-cell

proliferation must regulate the nuclear localization of DAF-16 in somatic

nongonadal tissues (25). 

---

Tom Savin





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