RE: RADSAFE digest 3303

["Wright, Will (DHS-PSB)" <WWright2@dhs.ca.gov>]

Evidence :
That is very demonstrable with controlled exposure scenarios, which are
virtually impossible with people.  There is a wealth of info in
microorganisms of this type.  Basically when one has a known sequence, the
types of mutations, transitions, transversions are predictable.  When
exposure is controlled and known, one only has to deal with the probability
of spontaneous conversions to distinguish between causes.  This involves
what are single base changes or point mutations.   Single base deletions may
cause extensive damage by frame shifting which may add to confusion about
what happened and the cause.  With non-ionizing radiation such as uv one can
know what array of mutations to expect in that transversions and small
deletions would predominate, where as nitorsoguanidine yields predominantly
transitions and deletions and clusters in high enough concentrations and
then there is the famous radio- mimicking group(N-mnitorsourea,
methymehtanesulfonate, 4-nitroquinlineoxide, etc) which predomanantly
produce transitions. All of the theories of  rad versus chemical mutations
occurred during early studies.  A large bias on what is expressed or
observed in a sequence is due to the redundancy of the code with transition
probabilities predominating.  This is essentially how the argument goes.


		-----Original Message-----
		From:	John R Laferriere
[mailto:John.R.Laferriere@dupontpharma.com]
		Sent:	Thursday, July 27, 2000 7:43 AM
		To:	Multiple recipients of list
		Subject:	Re: RADSAFE digest 3303

		> I wonder just what would constitute "scientific evidence".
Suppose, for
		> example, that a person received a small radiation exposure
(<10 rem) at
		> their work, and years later developed cancer. Since
radiogenic cancer is
		> generally  indistinguishable from other cancers how could
radiation etiology
		> be either proved or disproved?

		Regarding the above quote- I recall a New England Chapter
Annual Meeting maybe 6 years ago where one of 
		the speakers (perhaps from MIT) presented results of
research involving analysis of DNA damage from tumor 
		cells induced by exposure to ionizing radiation and from
tumor cells induced by exposure to another carcinogen.  
		There was a distinct "fingerprint" to the DNA from each of
the tumor cells, and the two were clearly different from 
		each other.  The conclusion was that it might be possible to
use the technique to determine what agent actually 
		caused a cancer, or to at least rule out certain agents.  I
remember thinking at the time that this would be a real
		breakthrough in determining causation, and that we would
probably hear a lot more about in the future.  In reality,
		I never heard anything more about it.  Hopefully my memory
is accurate- If anyone else remembers this speaker,
		let me know.  I think there was another speaker from MIT
(Jacquelyn Yanch?) speaking about BNCT at the same
		meeting, if that helps jog anyone's memory.


		Regards,

		John R. Laferriere, CHP
		DuPont Pharmaceuticals Co.
		Medical Imaging Division
		john.r.laferriere@dupontpharma.com
		(978) 671-8316   fax (978) 671-8149
	
************************************************************************
		The RADSAFE Frequently Asked Questions list, archives and
subscription
		information can be accessed at
http://www.ehs.uiuc.edu/~rad/radsafe.html
************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html