Re: Mitotic spindle and magnetic poles.

On the Yahoo discussion group on Cellbiology, 
http://groups.yahoo.com/group/cellbiology/ , someone posted a link to
research establishing an effect of strong magnetic fields on the
division process:

Powerful magnetic field forces living cells to change.
"Writing in the Proceedings of the National Academy of Sciences, the
researchers suggest that the magnetic field forced cellular protein
ropes, called microtubules, to orient parallel to it, re-orienting the
cleavages. A microtubule is a cellular structure, part of what is
called the mitotic spindle apparatus, which normally determines
cleavage direction.
"The microtubules re-orient in a similar way as a compass needle turns
along magnetic north. Unlike the iron in a compass needle, the Earth's
weak magnetic field is insufficient to cause the microtubules to
realign. The materials composing the microtubules and the rest of the
frog eggs respond very weakly to magnetic fields. This weak response
is probably at the root of disagreements among scientists about
whether steady magnetic fields affect living things, the researchers
said. Their study shows that a huge magnetic field, more than 100,000
times as strong as Earth's, will affect the eggs."
http://www.brown.edu/Administration/News_Bureau/1998-99/98-098.html

 The full text of the PNAS article is available here:

Cleavage planes in frog eggs are altered by strong magnetic fields 
(cell division/mitotic apparatus/microtubules/Xenopus) 
James M. Denegre*, James M. Valles Jr., Kevin Lin, W. B. Jordan, and
Kimberly L. Mowry
PNAS, Vol. 95, Issue 25, 14729-14732, December 8, 1998
http://www.pnas.org/cgi/content/full/95/25/14729

 There are links to similar research on this page.

 After a web search I also found this:

Cisplatin
1. Study of the Effect of Electric Fields on E. coli
http://science.kennesaw.edu/~mhermes/cisplat/cisplat01.htm

 
   Bob Clark


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r norman <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> On 24 Nov 2003 22:06:58 -0800, [EMAIL PROTECTED] (Robert Clark)
> wrote:
> 
> >Has there been any investigation of the possibility that the origin of
> >the mitotic spindle really is due to electromagnetism?
> > Compare the image on this page:
> >
> >Media: Mitotic Spindle.
> >http://www.meta-library.net/media/mitspin-body.html
> >
> > To the first image on this page:
> >
> >Magnetism.
> >http://www.warren-wilson.edu/~physics/physics2/Formal_2001/BenWarren/formallab%25202.htm
> >
> 
> There is no reason to believe magnetism is a mechanism just because
> the pictures look similar.  Look at the electric field of a dipole
>   http://hyperphysics.phy-astr.gsu.edu/hbase/electric/dipole.html
> to see the same thing.
> 
> The similarty in shape is caused by processes which share some
> superficial similarities but major differences  For the similarities,
> first, there are two separate "organizing centers": the spindle poles
> for mitosis, and the two poles of a magnetic or electric dipole.  At
> each organizing center there is a tendency for lines to radiate from
> the center in all directions.  In both the magnetic and the electric
> dipoles, the tendency is to radiate outward from one of the poles but
> to radiate inward into the other pole.  The result is the
> spinde-shaped pattern of field lines.  There really are strong
> parallels between the magnetic and the electric dipoles -- one pole
> radiates out, the other radiates in.  Add the two together and you get
> the result.
> 
> In the spindle, the process is very different.  The spindle fibers
> radiate outward from both poles.  Some of these, the astral fibers,
> always remain that way.  These do not look at all like the magnetic or
> electric dipole lines but look more like a magnetic or electric
> monopole.  Others meet (either by direct contact as in the polar
> fibers or by connecting to the same chromosome in the kinetochore
> fibers).  These fibers tend to spread out from one pole and then
> rejoin at the other, and so sort of look like the field lines of the
> magnetic or electric dipole.  Since the fibers that attach to the
> chromosomes are the "important" ones, they are the ones shown in all
> the diagrams. 
> 
> So in this case, the similarity is really superficial.  However, the
> cause of science is always furthered by trying to find relationships
> between seemingly very different things -- so keep looking and keep
> asking!