Re: Dioxins and Plants

["Jon Campbell" <jon@cqs.com>]

Hello,

       Dioxins are not found in nature except in exceedingly small
concentrations (lightning bolts into the ocean), nothing like what is found
today. The only reason that trees give off dioxin when burned is because
they have absorbed organochlorines from their contaminated atmosphere
(especially where 2,4-D and 2,4,5-T have been sprayed!). They are extremely
peculiar molecules. As far as I have read, there are no natural organisms
which can use or assimilate them.

        Your thoughts about a "signal" molecule are interesting, not so much
regarding dioxin, but regarding the sites that dioxin happens to match - the
Ah receptor sites. Not much is known about them, except that if you
eliminate them from mice (knockouts) the mice die from having no immune
system. Your idea of their being signal sites, therefore, is a fascinating
one. There might be some hormone, produced for a miniscule time during
gestation, that is important for the production of the immune system.
(Dioxin is absolute poison to these sites - that's why it is probably the
most toxic chemical known...)

      Anyone out there doing Ah receptor research?

Thanks
Jon
-----Original Message-----
From: Antoine Labeyrie <labeyrie@obs-hp.fr>
To: Multiple recipients of list <dioxin-l@essential.org>
Date: Monday, January 26, 1998 6:38 AM
Subject: Re: Dioxins and Plants


>  I am not an expert in dioxins ( being an astronomer), but wonder like
other
>biologists whether dioxins are signal molecules, normally  used in nature,
or
> just chemical analogues of pheromon and hormon molecules.
>  The discovery of specific dioxin receptors on the DNA of mammals suggests
a
> role as signal molecules.The production of dioxins by forest fires, often
> quoted by incineration advocates, suggests that the  DNA receptors may
serve
> as fire alarms, triggering metabolic responses.  Is there evidence for
similar
> receptors in invertebrates and plants ?
>
>Antoine Labeyrie
>College de France
>