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RE: Radiation Hormesis -- or not
Catherine
I would also say that not all negative mutations are
selected against survival. There are a number of
genetic diseases that do not improve the species, e.g.
hemophilia, but are still present and are passed
along. It escapes me what was the evolutionary or
genetic process that allowed it to exist in humans.
--- Catherine Perham <cperham@ehso.emory.edu> wrote:
> John;
>
> Genetic effects are completely random and as you
> mention cannot be "willed."
> We only see the positive genetic mutations such as
> opposable thumbs because
> all of the negative mutations were selected against-
> in other words, they
> died. Random effects are very unlikely to be
> positive and that is why
> evolution takes so long. Most mutations change a
> protein structure such as
> a hormone that may render it unusable to the
> organism.
>
> My theory on the relative strength of the seedlings
> in the experiment in
> question is that the radiation killed off various
> fungi and viruses that may
> have lived on the seeds, and not a favorable
> mutation within the seed
> itself. After all, a dormant seed is not made up of
> actively dividing
> cells.
>
> Cheers;
> Catherine
>
> -----Original Message-----
> From: John Jacobus [mailto:crispy_bird@YAHOO.COM]
> Sent: Monday, January 26, 2004 4:17 PM
> To: Neil, David M; Carl Speer;
> radsafe@list.Vanderbilt.Edu
> Subject: RE: Radiation Hormesis -- or not
>
>
> Why would a genetic mutation favor a negative
> effect?
> After all, evolution shows that genetic effects are
> positive since they allow the organism to adapt.
> Primates did not get opposed thumbs by willing it to
> happen. It was genetics.
>
> Again, my statement was that it should have been
> checked to see if it was a genetic mutation by
> following the growth pattern of the off-spring.
>
> --- "Neil, David M" <neildm@id.doe.gov> 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.
> >
> > Dave Neil
> >
> > -----Original Message-----
> > From: John Jacobus [mailto:crispy_bird@yahoo.com]
> > Sent: Friday, January 23, 2004 7:09 AM
> > To: Carl Speer; radsafe@list.vanderbilt.edu
> > Subject: RE: Radiation Hormesis -- or not
> >
> >
> > Carl,
> > A thought came to me. How do you know this was a
> > hormetic effect and not a genetic mutation? My
> > understanding is the a hometic effect involves the
> > addition of some simulus to an living organism to
> > get
> > a beneficial response. You irradite mice to low
> > doses
> > and you get a certain response, e.g., an increase
> in
> > the immune system. When the agent is stopped, the
> > hormetic effect is no longer evident after a time.
> > Maybe this definition for hormesis is too
> limiting,
> > but this is what I believe it is.
> >
> > Seeds are not actively growing or responding
> > organisms. If you irradiated the growing plant, I
> > would agree that would be be a way of
> demonstrating
> > a
> > hormetic effect. Did you try and grow new plants
> > from
> > the seeds produced from the mature, irradiated
> > plants?
> > I think that would have demonstrated the effect
> of
> > genetic mutation.
> >
> > --- John Jacobus <crispy_bird@yahoo.com> wrote:
> > > Interesting. What were the doses?
> > >
> > > --- Carl Speer <rtrs@cox.net> wrote:
> > > > Karl (and others),
> > > >
> > > > We had and interesting laboratory experiment
> in
> > > > Radiation Biology when I
> > > > was in college where we irradiated bean seeds,
> > > fruit
> > > > flies, and onion
> > > > root with low, med, and high doses from a
> Co-60
> > > > source from a local
> > > > hospital. To show the effects of hormesis, no
> > > > effect, and ill effect
> > > > the students all received seeds from each
> > exposed
> > > > group plus seeds that
> > > > did not get any extra dose (controls). We
> > planted
> > > > the seeds in cups at
> > > > our home, gave all plants the same amount of
> > water
> > > > and noted the
> > > > differences. The seeds with the low doses had
> > > more
> > > > vigorous growth,
> > > > smaller internodal lengths, and healthier
> leaves
> > > > than the control. The
> > > > higher dose plants had brown shriveled leaves,
> > > > stunted growth, and other
> > > > undesirable characteristics. We made a plot
> > > showing
> > > > that as the dose
> > > > initially increased we saw a net positive
> effect
> > > > (hormesis) but as the
> > > > dose continued to increase, a negative effect
> > > became
> > > > apparent. This
> > > > made a lasting impression and I have believed
> in
> > > > hormesis ever since. I
> > > > know people are not bean plants or fruit flies
> > but
> > > > this little
> > > > experiment gave the hormesis theory more
> > > > believability than the LNT in
> > > > my mind.
> > > >
> > > > As for the fruit flies I don't remember the
> low
> > > dose
> > > > effects. What
> > > > stands out in my memory were the horrific
> > > mutations
> > > > in the offspring of
> > > > the high dose flies.
> > > >
> > > > The onion root tips were used so we could see
> > the
> > > > chromosome damage in
> > > > the cells undergoing meiosis.
> > > >
> > > > See http://www.belleonline.com/n2v82.html
> > > RADIATION
> > > > HORMESIS: ITS
> > > > HISTORICAL FOUNDATIONS AS A BIOLOGICAL
> > HYPOTHESIS
> > > by
> > > > Edward J. Calabrese
> > > > and Linda A. Baldwin for a good discussion on
> > > > Hormesis.
> > > >
> > > > Carl Speer
> > > > Real-Time Radiological Services, Inc.
> > > > 2721 Losee Rd, Suite E
> > > > North Las Vegas, NV 89030
> > > > 702.639.0066
> > > > www.RealtimeRad.com
> > > > RTRS@cox.net
> > > >
> > > >
> > > > -----Original Message-----
> > > > From: owner-radsafe@list.vanderbilt.edu
> > > > [mailto:owner-radsafe@list.vanderbilt.edu] On
> > > Behalf
> > > > Of
> > > > RuthWeiner@AOL.COM
> > > > Sent: Monday, January 19, 2004 7:28 AM
> > > > To: "Karl Ellison";
> > > > radsafe-digest@list.vanderbilt.edu
> > > > Subject: Re: Radiation Hormesis
> > > >
> > > > I have always wondered how one could
> distinguish
> > > > hormesis effects from
> > > > ordinary good health. An example: small
> amounts
> > > of
> > > > ionizing radiation
> > > > are supposed to stimulate bone knitting after
> a
> > > > break (I read this
> > > > somewhere). However, the rates of bone
> recovery
>
=== message truncated ===
=====
+++++++++++++++++++
"I have sworn upon the altar of God, eternal hostility against every form of tyranny over the mind of man."
Thomas Jefferson
-- John
John Jacobus, MS
Certified Health Physicist
e-mail: crispy_bird@yahoo.com
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