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Fwd: RE: nematodes
>
> Hi Jim, Good to correspond,
>
> The point that I was trying to make is two fold.
>
> 1. There is a protective mechanism that we have
> (humans and every other living organism) to respond
> to
> chemical, biological, radioactive insult - the heat
> shock response is well documented, and it is not
> only
> due to heat(other insults can also induce this
> response). Of course this reponse is good within a
> limited range, ie. if someone gets a fever of 107 F
> there is going to be some damage. Therefore
> hormesis.
>
> 2. I also would also like to highlight the lack of
> scientific knowledge we currently have - C. elegans
> lives longer if one removes germ cell lineage. This
> is also true of octopus. - the point being that
> removal of the germ cells is a type of insult in
> which
> the organism responds to the best of its ability -
> not
> knowing that it is sterile - but increases its
> lifespan to live long enough to (stupidly) the
> chance
> of breeding. Surivel of the fittest or a mechanism
> which is illadopted to the challenge.
>
> I hope this helps and thanks for the question - Tom
>
>
> --- Jim Muckerheide <jmuckerheide@cnts.wpi.edu>
> wrote:
> > Tom, ?? Why do you think something would
> "support"
> > hormesis in this abstract? There's not even a
> > journal/title to find the paper. :-(
> >
> > I don't understand the point you are making. Can
> you
> > explain? Is there anything in the full paper about
> > response to stressors affecting proliferating
> > germ-line stem cells, or transcription regulator,
> > or?
> >
> > Perhaps the following papers will help to clarify
> > the response for you. I don't have access to this
> > journal. We will review the papers when we can get
> > them. If anyone has access to this journal, I
> would
> > very much appreciate these papers.
> >
> > Regards, Jim
> > =============
> >
> > J Gerontol A Biol Sci Med Sci 2002
> Mar;57(3):B109-14
> >
> > Multiple Stressors in Caenorhabditis elegans
> Induce
> > Stress Hormesis and Extended Longevity.
> >
> > Cypser JR, Johnson TE.
> > Institute for Behavioral Genetics, University of
> > Colorado, Boulder.
> >
> > We demonstrate here that the nematode
> Caenorhabditis
> > elegans displays broad hormetic abilities.
> Hormesis
> > is the induction of beneficial effects by exposure
> > to low doses of otherwise harmful chemical or
> > physical agents. Heat as well as pretreatment with
> > hyperbaric oxygen or juglone (a chemical that
> > generates reactive oxygen species) significantly
> > increased subsequent resistance to the same
> > challenge. Cross-tolerance between juglone and
> > oxygen was also observed. The same heat or oxygen
> > pretreatment regimens that induced subsequent
> stress
> > resistance also increased life expectancy and
> > maximum life span of populations undergoing normal
> > aging. Pretreatment with ultraviolet or ionizing
> > radiation did not promote subsequent resistance or
> > increased longevity. In dose-response studies,
> > induced thermotolerance paralleled the induced
> > increase in life expectancy, which is consistent
> > with a common origin.
> > ===============
> >
> > J Gerontol A Biol Sci Med Sci 2002 Mar
> > 1;57(3):B83-B92
> >
> > Heat Shock Changes the Heterogeneity Distribution
> in
> > Populations of Caenorhabditis elegans: Does It
> Tell
> > Us Anything About the Biological Mechanism of
> Stress
> > Response?
> >
> > Yashin AI, Cypser JW, Johnson TE, Michalski AI,
> > Boyko SI, Novoseltsev VN.
> > Max Planck Institute for Demographic Research,
> > Rostock, Germany. Center for Demographic Studies,
> > Duke University, Durham, North Carolina. Institute
> > for Behavioral Genetics, Boulder, Colorado.
> > Institute of Control Sciences, Russian Academy of
> > Sciences, Moscow.
> >
> > In this paper we analyze survival data of
> > populations of sterilized nematodes,
> Caenorhabditis
> > elegans, exposed to heat shocks of different
> > duration at the beginning of their adult lives.
> > There are clear hormesis effects after short
> > exposure to heat and clear debilitation effects
> > after long exposure. Intermediate durations result
> > in a mixture of these two effects. In this latter
> > case, the survival curves for the control and
> > experimental populations intersect. We show that
> > observed effects may be explained by using a model
> > of discrete heterogeneity. According to this
> model,
> > each population of worms in the experiment is a
> > mixture of subcohorts of frail, normal, and robust
> > individuals; exposure to heat changes the initial
> > proportion of worms in the subcohorts
> (heterogeneity
> > distribution); and these changes depend on the
> > duration of exposure. In other words, exposure to
> > heat does not influence mortality rates (survival
> > functions) in the subcohorts but does cause
> > individuals to move!
> > from one subcohort to another. In a biological
> > interpretation of this finding we hypothesize
> that,
> > when coping with stress, the organisms of worms
> use
> > several lines of defense. Switching these lines on
> > and off in response to stress in individual
> > organisms generates the spectrum of observed
> > survival effects at the population level. We
> discuss
> > possible molecular biological mechanisms of stress
> > response and directions for further research.
> >
> > -----Original Message-----
> > From: Thomas J Savin [mailto:tjsav@LYCOS.COM]
> > Sent: Wed 13-Feb-02 1:23 PM
> > To: radsafe@list.vanderbilt.edu
> > Cc:
> > Subject: nematodes
> >
> > Fellow radsafers - Just wanted to use this example
> > of how complicated research is and how one find
> does
> > not necessarily mean what one suggests - Does
> anyone
> > think that this article (below) supports hormesis?
>
> > This is in response to the microwave report on
> > nematodes:
> >
> > Regulation of Life-Span by Germ-Line Stem Cells in
> > Caenorhabditis elegans
> > Nuno Arantes-Oliveira, Javier Apfeld,* Andrew
> > Dillin, Cynthia Kenyon
> >
> > The germ line of the nematode Caenorhabditis
> elegans
> > influences life-span; when the germ-line precursor
> > cells are removed, life-span is increased
> > dramatically. We find that neither sperm, nor
> > oocytes, nor meiotic precursor cells are
> responsible
> > for this effect. Rather life-span is influenced by
> > the proliferating germ-line stem cells. These
> cells,
> > as well as a downstream transcriptional regulator,
> > act in the adult to influence aging, indicating
> that
> > the aging process remains plastic during
> adulthood.
> > We propose that the germ-line stem cells affect
> > life-span by influencing the production of, or the
> > response to, a steroid hormone that promotes
> > longevity.
> >
> > Department of Biochemistry and Biophysics,
> > University of California San Francisco, San
> > Francisco, CA 94143-0448, USA.
> > * Present address: Exelixis, Inc., South San
> > Francisco, CA 94083, USA.
> >
> > To whom correspondence should be addressed.
> > E-mail: ckenyon@biochem.ucsf.edu
> >
> > So, any thoughts? - Tom
> > ---
> > Tom Savin
> >
> >
>
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