RE: Radiation Hormesis -- or not

["Frank Helk" <frank.helk@nis-hanau.de>]

On Mon, 26 Jan 2004 10:49:22 -0700, Neil, David M wrote:



>If it were a genetic mutation, the odds favor (immensely) a negative effect.  

>This would translate to lower germination ratios (live plants per seed planted) 

>and a mixture of positive and negative effects.  This is not what is observed. 



I agree to that .... don't ask me for the source, but the following explanation of the hormesis effect seems to be the most logical for me:



Cells are equipped with mechanisms for the repair of genetic defects (not only by radiation ...). Some of these mechanisms would have (counted over all) 

negative effects if they are allways active, i.e. the energy needed to maintain them is too high if there's not enough to do, or they produce negative 

byproducts, etc.. For that cause they are "sleeping" when the cells are not exposed to mutagen agents.



This is similar to the effect that bacteria may acquire resistence if exposed to antibiotica, but loose the resistence if the antibioticum is not present any more ... 

the resistive mechanism costs too much energy if running idle.



If the cells are exposed to an agent (i.e. radiation, free  radicals, etc.) above a certain level, the sleeping repair mechanisms are waked up. The wakeup 

level is lower than the "break even", where there's more damage than the repair mechanism are able to compensate. If "operated" between the wakeup 

level an the "break even" level, the mechanisms will not only repair the additional effects by the mutagen agent, they will repair the otherwise unrepaired 

defects too.



The simplified outcome (= overall effect) is that in the range between the "wakeup level" and the "break even" level the mutagen agent will have a positive 

effect, called hormesis.



Best regards



	Frank Helk





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