[ RadSafe ] Danger of ADJACENT HIGH-Dose Radiation

Thu Aug 21 12:16:48 CDT 2008

The distances involved in this experiment seem too far for diffusion of
radicals.
What I understand (grok [for the geeks out there]) from the few papers
that I have read...
Acute "low-level" exposures seem garner signal transduction responses
that favor cell death or very basic repair attempts.  Acute "high-level"
exposures seem to result in signal transduction responses that favor
(emergency) repair mechanisms.
In this experiment, it seems that the (emergency) repair mechanisms are
being triggered in the shielded area -- the repairs are either acting on
damage caused by the low-level scatter or the normal damage caused by
cellular processes.

I see that normal wild-type mice in the experiment did not display any
carcinogenic response -- only the patch1 mice.  Normal mice did show
short term effects that seemed to be evidence for the transmission of
the high-exposure response to the shielded areas.

C. 

---
Cary Renquist
RSO, Eckert & Ziegler Isotope Products
Office: +1 661-309-1033
cary.renquist at ezag.com

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of NIXON, Grant
Sent: Wednesday, 20 August, 2008 13:09
To: HOWARD.LONG at comcast.net; ROY HERREN; radsafe at radlab.nl
Subject: RE: [ RadSafe ] Danger of ADJACENT HIGH-Dose Radiation 

To add to Howard's comment:

Perhaps the mechanism for the DNA damage to adjoining tissue (the
so-called "bystander effect") is nothing more than a propagated
free-radical reaction having nothing to do with cell-to-cell
communication. The high doses would liberate such large numbers of
free-radicals that the affected perimeter of affected tissues would
increase on physical grounds alone (diffusion theory coupled with target
theory). The "chemical that blocks cell-to-cell communication" may
simply be a free-radical scavenger.

Grant I. Nixon, Ph.D., P.Phys.
Science Specialist (Dosimetry/Physics/Engineering)
BEST Theratronics
413 March Road
Ottawa, ON  K2K 0E9
Canada
tel. (613) 591-2100 x2869
fax. (613) 591-2250

-----Original Message-----
From: radsafe-bounces at radlab.nl [mailto:radsafe-bounces at radlab.nl] On
Behalf Of HOWARD.LONG at comcast.net
Sent: Wednesday, August 20, 2008 12:36 PM
To: ROY HERREN; radsafe at radlab.nl
Subject: [ RadSafe ] Danger of ADJACENT HIGH-Dose Radiation 

So, "high dose radiation - 12,000 times - chest x-ray" affects adjacent
tissue?
Would other severe injury, like crushed arm, affect the rest of the
body? Of course!

Why the surprise?

Why the false headline that it  "Hints at Dangers of Low Dose
Radiation"?

Hormesis, low dose good where high dose bad, must be taught.  
We must correct this disinformation by fearmongers 
to dismantle over-regulation and liberate nuclear power.

Howard Long

-------------- Original message -------------- 
From: ROY HERREN <royherren2005 at yahoo.com> 

> http://sciencenow.sciencemag.org/cgi/content/full/2008/818/3 
> 
> Bystander Effect" Hints at Dangers of Low-Dose Radiation 
> 
> By Jocelyn Kaiser 
> ScienceNOW Daily News 
> 18 August 2008That lead apron you wear during a dental x-ray is
supposed to 
> protect the rest of you from radiation. But it may not work very well,
according 
> to a new study. When cancer-prone mice were placed in lead containers
and 
> irradiated on just the lower half of their bodies, they developed
brain tumors. 
> The results suggest that radiation could be riskier than scientists
thought. 
> The study builds on a surprising effect, first observed 16 years ago.
When cells 
> in culture are exposed to ionizing radiation, even those not directly
hit 
> sustain damage to chromosomes. Apparently, the irradiated cells pass
on a 
> distress signal or emit some chemical that breaks the DNA of
neighboring cells 
> (ScienceNOW, 7 September 2005). Although this "bystander effect" has
been 
> observed in tissue culture and recently in living animals, no
experiments have 
> yet linked it to the main reason for concern: Bystander effects might
trigger 
> cancer. Some scientists even suspect the opposite--that the bystander
responses 
> could protect against the disease by killing damaged cells. 
> Now it seems that the cancer risk is real. Radiation oncologist Anna
Saran at 
> the Italian National Agency for New Technologies, Energy and the
Environment in 
> Rome and colleagues studied mice with a mutation in a gene called
Patched that 
> makes them susceptible to brain tumors early in life. They placed
newborn mice 
> in lead shields that protected their heads and upper bodies, then
zapped them 
> with high-dose x-rays, or about 12,000 times the dose of a dental or
chest 
> x-ray. The scientists found that the cerebellums of these animals had
higher 
> than normal amounts of DNA damage and apoptosis, or programmed cell
death. By 40 
> weeks of age, 39% of the shielded mice had developed brain tumors.
That's a lot 
> considering that the rate was 62% in Patched mice that were irradiated
all over, 
> including their heads. Patched mice that weren't irradiated did not
develop 
> brain cancer. 
> When the team injected the shielded mice with a chemical that blocks 
> cell-to-cell communication before irradiating them, they detected no
DNA breaks 
> and the amount of apoptosis decreased more than threefold. Even though
the 
> irradiated tissues are far away from the brain, they are connected by
neurons 
> that could be passing on bystander signals, Saran says. The results
appear 
> online this week in the Proceedings of the National Academy of
Sciences. 
> "This is a milestone paper," says Columbia University radiation
physicist David 
> Brenner. He suggests that current estimates of cancer risk from low
doses of 
> radiation--say, from naturally occurring radon and diagnostic
tests--may 
> underestimate the danger by failing to take into account bystander
effects. To 
> learn more, however, the mouse work should be repeated with lower
doses of 
> radiation, Saran says. 
> 
> 
> 
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