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RE: Laymans questions on hormesis and LNT
Jim,
Thanks for the reply. Accepting that fact that DNA
repair occurs at no or low doses, this does make
sense. Again, I would like a citation demonstrating
this phenomenon.
However, you have not alleviated my pessimism about
the future of regulations. If you can say that you
will regulate dose to reduce risks from cancer (with
the normal incidence rate of 25%), what prevents the
regulations to reduce DS breaks? It may sound
far-fetched, but why not?
--- "Muckerheide, Jim (CDA)"
<Jim.Muckerheide@state.ma.us> wrote:
> John,
>
> Error-free at low dose rates because the
> genes/enzymes that are
> expressed are the ones that do error-free repair.
> This has nothing to do
> with radiation. It is the normal stress-response. It
> depends a lot on
> cell cycle arrest with time to both make accurate
> repairs and to
> eliminate cells that are not correctly repaired. It
> has/uses the luxury
> of time. Under high doses, tissues express different
> genes (and some of
> the genes are suppressed vs. stimulated, and vice
> versa, along with
> other cells and molecules), to do fast "emergency"
> repair.
>
> On the other point, as Ted has pointed out, using
> "preventing DSBs" is
> known to be irrelevant since they are a small and
> insignificant
> contribution to endogenous DSBs rates. Kind of like
> filling an Olympic
> pool with a garden hose during a rain storm :-)
>
> Regards, Jim
>
>
> -----Original Message-----
> From: John Jacobus [mailto:crispy_bird@yahoo.com]
> Sent: Monday, September 15, 2003 2:30 PM
> To: Muckerheide, Jim (CDA); John Jacobus; Ted
> Rockwell;
> radsafe@list.vanderbilt.edu; Cary Renquist
> Cc: Muckerheide-MA
> Subject: RE: Laymans questions on hormesis and LNT
>
>
> Jim,
> I am not sure if I get your point. Why should error
> free repair only occur at low dose rates? Why does
> high biological stress, but not low biological
> stress,
> cause different gene responses that lead to
> error-prone repair? It is an interesting idea, but
> are there any studies that show the differences
> beyond
> the magnatude of the effects of the radiation?
>
> Whether we like it or not, I do think that the
> prevention of DS breaks (beyond the natural
> background
> rates) will replace increased cancer rates as the
> regulatory criteria.
>
> --- "Muckerheide, Jim (CDA)"
> <Jim.Muckerheide@state.ma.us> wrote:
> > John,
> >
> > Right. DSB disinformation is used to support the
> > LNT.
> >
> > But DNA damage is irrelevant. Long-term effects
> > (e.g., cancer) are due
> > to failure of repair and removal of damaged
> > cells/tissues.
> >
> > Replicated results confirm that LDR stimulates DNA
> > repair enzymes and
> > genes (even in cancer-prone individuals) that
> > produce error-free repair
> > (plus stimulate lymphocytes and other immune cells
> > and molecules, which
> > enhances health by affecting the non-rad damage
> and
> > latent damage). HDR
> > adds negligible "DNA damage" but the high
> biological
> > stress causes
> > different genes to be expressed that cause
> > error-prone "emergency"
> > cellular repair modes that produce a legacy of
> > latent damage. (That
> > latent damage is also reduced by later LDR
> > exposures/treatments.)
> >
> > Regards, Jim Muckerheide
> >
> >
> > -----Original Message-----
> > From: John Jacobus [mailto:crispy_bird@yahoo.com]
> > Sent: Monday, September 15, 2003 9:34 AM
> > To: Ted Rockwell; radsafe@list.vanderbilt.edu;
> Cary
> > Renquist
> > Cc: Muckerheide-MA
> > Subject: RE: Laymans questions on hormesis and LNT
> >
> >
> > Ted,
> > I think we agree that the use of DS breaks is not
> a
> > guide to regulation limits. Unfortunately, I have
> a
> > feeling that is what will happen.
> >
> > --- Ted Rockwell <tedrock@starpower.net> wrote:
> > > >then you
> > > justified in regulate exposures to prevent DS
> > > breaks.
> > >
> > > John:
> > >
> > > You cannot regulate to prevent DS breaks unless
> > you
> > > outlaw normal
> > > metabolism. That's what causes the overwhelming
> > > majority of DS breaks.
> > >
> > > Ted Rockwell
> > >
> > >
> > > -----Original Message-----
> > > From: owner-radsafe@list.vanderbilt.edu
> > > [mailto:owner-radsafe@list.vanderbilt.edu]On
> > Behalf
> > > Of John Jacobus
> > > Sent: Sunday, September 14, 2003 4:21 PM
> > > To: Ted Rockwell; radsafe@list.vanderbilt.edu;
> > Cary
> > > Renquist
> > > Cc: Muckerheide-MA
> > > Subject: RE: Laymans questions on hormesis and
> LNT
> > >
> > >
> > > Ted,
> > > You are missing the point of my argument. What
> I
> > > was
> > > saying is if you declare that it radiation
> causes
> > DS
> > > breaks are detrimental to cell functions, then
> you
> > > justified in regulate exposures to prevent DS
> > > breaks.
> > > I am saying that you are not. As I said, just
> > > because
> > > you can detect an effect does not mean it should
> > be
> > > used as the basis of regulations. Simply
> stated,
> > DS
> > > breaks can be (1) repaired (2)exist but do not
> > have
> > > effects of cell functions, (3) cause cell death,
> > or
> > > (4) lead to cancerous growths. All are
> possible,
> > > but
> > > only the last should be regulated against.
> > However,
> > > how do differentiate between the DS breaks? I
> say
> > > regulations should be based on factors other
> than
> > > the
> > > formation of DS breaks.
> > >
> > > I think you are looking to defend hormesis
> without
> > > understanding my comments.
> > >
> > > . . .
> >
> > =====
> > "May we never confuse honest dissent with disloyal
> > subversion."
> >
> > Dwight D. Eisenhower
> >
> > -- John
> > John Jacobus, MS
> > Certified Health Physicist
> > e-mail: crispy_bird@yahoo.com
> >
> > __________________________________
> > Do you Yahoo!?
> > Yahoo! SiteBuilder - Free, easy-to-use web site
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>
>
> =====
> "May we never confuse honest dissent with disloyal
> subversion."
>
> Dwight D. Eisenhower
>
=== message truncated ===
=====
"May we never confuse honest dissent with disloyal subversion."
Dwight D. Eisenhower
-- John
John Jacobus, MS
Certified Health Physicist
e-mail: crispy_bird@yahoo.com
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