Document Detail


Hormesis: an adaptive expectation with emphasis on ionizing radiation.
MedLine Citation:
PMID:  10715607     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Non-linear fitness gradients with maxima between extremes are expected for any environmental variable to which free-living populations are exposed. For exceedingly toxic agents, including ionizing radiation, such deviations from linearity are close to zero exposure and are conventionally called hormesis. Accordingly, hormesis is an extreme version of the non-linear fitness gradients for general environmental stresses such as temperature fluctuations, for which maximum fitness occurs at the moderate temperature fluctuations to which free-living populations are most commonly exposed. Some metabolic reserves should occur under moderate temperature stresses because of the need for pre-adaptation enabling survival during exposure to occasional periods of more extreme stress, especially at species borders where selection for stress resistance is likely to be most intense. Because heat shock proteins are induced by all stresses, adaptation to extreme temperatures should translate into adaptation to other stresses. Consequently, metabolic reserves from adaptation to extreme temperatures in the past should translate into protection from correlated abiotic stresses, especially in human populations where modern cultural processes are now ameliorating exposure to extreme stresses. Ambient and man-made radiations of non-catastrophic dimensions should therefore lead to stress-derived radiation hormesis. Other stresses can, in principle, be incorporated into this model. Accordingly, evolutionary and ecological considerations suggest two components of hormesis in relation to ionizing radiation: background radiation hormesis based upon the background exposure to which all organisms on earth are subjected; and stress-derived radiation hormesis. Exposure under stress-derived radiation hormesis is considerably larger than under background radiation hormesis, so significant deleterious effects from non-catastrophic radiation normally may be impossible to detect. Suggestions are provided for testing such postulated deviations from the commonly assumed linear no-threshold (LNT) hypothesis for the biological consequences of exposure to radiation.
Authors:
P A Parsons
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Publication Detail:
Type:  Journal Article; Review    
Journal Detail:
Title:  Journal of applied toxicology : JAT     Volume:  20     ISSN:  0260-437X     ISO Abbreviation:  J Appl Toxicol     Publication Date:    2000 Mar-Apr
Date Detail:
Created Date:  2000-04-21     Completed Date:  2000-04-21     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  8109495     Medline TA:  J Appl Toxicol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  103-12     Citation Subset:  IM    
Copyright Information:
Copyright 2000 John Wiley & Sons, Ltd.
Affiliation:
School of Genetics and Human Variation, La Trobe University, Bundoora, Victoria 3083, Australia.
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MeSH Terms
Descriptor/Qualifier:
Adaptation, Physiological / radiation effects*
Animals
Dose-Response Relationship, Radiation
Humans
Models, Biological
Radiation, Ionizing*
Stress, Physiological / physiopathology

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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