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RE: nematodes
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
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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.
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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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