[ RadSafe ] Two interesting papers on DNA repair mechanisms radiation is secular

[blreider at aol.com]

Ah, but low LET radiation breaks in DNA are thought to be statistically most likely due to secondary transfer of energy to molecules, free radical formation etc. not direct hits.  Indirect  damage - everything I have heard indicates this are also random but when I was around researchers on this subject molecular biology was not as advanced as it is now so perhaps there is more information on mechanisms.

Barbara Reider, CHP






-----Original Message-----
From: parthasarathy k s <ksparth at yahoo.co.uk>
To: blreider <blreider at aol.com>; CJB01 <CJB01 at health.state.ny.us>; radsafe <radsafe at health.phys.iit.edu>
Sent: Fri, Jul 2, 2010 2:40 pm
Subject: Re: [ RadSafe ] Two interesting papers on DNA repair mechanisms radiation is secular



Reider,
 
Chances are that breaks induced by ionizing radiation are random as  radiation is truly secular!
 
Regards
Parthasarathy



From: "blreider at aol.com" <blreider at aol.com>
To: CJB01 at health.state.ny.us; radsafe at health.phys.iit.edu
Sent: Fri, 2 July, 2010 23:58:08
Subject: Re: [ RadSafe ] Two interesting papers on DNA repair mechanisms


Clayton, 

Hope you are well.  I see from your signature that you either have changed jobs or you have new stationary yet again. 

I don't understand why the two statements are a contradiction. Cancer is a general name for numerous diseases with numerous causes.  Not all non-radiation initiated cancers have to also be initiated by radiation.  Are you saying that all radiation initiated cancers  also don't have another cause?  I guess that could be true if there are no non-radiation causes for random DNA strand breaks.*  

I don't know enough about the different cervical cancers to add anything about the molecular structure, however for other cancers there can be many different initial cell types all lumped together under the name of the organ involved.  Is all cervical cancer initiated in the same type of cell?  Lung cancer has numerous initial lung cell types, and some of the same types of lung cancers that are attributed to smoking are also attributed to radiation (Adenocarcenoma).  Smoking also is linked to other types of lung cancers that are not thought to be radiation induced (small cell).

The research to find mechanisms for cancer production is interesting as applied to the statistics used in our field, hence previous comments about LET and QF.  

Regards

Barbara Reider, CHP

*And to make this more difficult, perhaps indirect radiation induced strand breaks are not all random.  I though the early cell data showed random breaks though (anyone with newer info?).







-----Original Message-----
From: Clayton J Bradt <CJB01 at health.state.ny.us>
To: radsafe <radsafe at health.phys.iit.edu>
Sent: Fri, Jul 2, 2010 1:45 pm
Subject: Re: [ RadSafe ] Two interesting papers on DNA repair mechanisms


I'll be eager to read these papers hopefully over the holiday weekend. 
That's the 4th of July for you non-US citizens on the list.) 
hat still puzzles me about the entire subject is the contradiction 
etween these two presumed facts: 
) Cancers caused by radiation are indistinguishable from non-radiogenic 
ancers.  2) Human Papilloma Virus (HPV) causes cervical cancer.
The first statement can't be true, because cervical cancer cells caused by 
PV have virus genes spliced into their DNA. These virus genes  function 
n specific ways to overcome some of the cells' control mechanisms and 
llow for uncontrolled proliferation. It is hard to believe that random 
adiogenic DNA damage and misrepair (no matter what the mechanisms) could 
uplicate these exact same virus genes in affected cells. So either 
adiation can't cause cervical cancer, or it causes a different kind of 
ervical cancer than HPV infection and there is a genetic marker that can 
istinguish the two. 
How many other cancers are the result of the incorporation viral genetic 
aterial?  Are the mutations that result in oncogenesis ever the result of 
andom damage and/or misrepair?
Clayton J. Bradt
rincipal Radiophysicist
aboratory for Inorganic & Nuclear Chemistry
YS Dept. of Health
18-474-1993
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