Thank you for the explanations Christina.
What I am trying to reconcile is the claim of irreversible binding having
cumulative effects with two pieces of evidence that appear to refute that
hypothesis:
1. Suchail's C14 study, and
2. Field observations of colonies chronically exposed to neonics either by
foraging on canola or experimentally fed neonics over the long term (such
as by Diveley, Wu, or a number of others).
So as not to make these posts too tedious, let's discuss these two in
different posts. In this post, let's discuss Suchail's findings.
She found that the chronic toxicity appeared to be mainly due to the olefin
metabolite, followed by the 4,5 metabolite. But both of those metabolites
essentially disappeared from the brain by 48 hours. Since the metabolites
are formed by the addition of a hydroxyl group, rather than degradation of
the IMI molecule, they would continue to be radioactive.
Thus, when the radioactivity disappears, that indicates that any bound
metabolites would have also disappeared from the bees' brains. True, as
Stan points out, the amount would never truly reach zero, but if you look
at her Fig 2A, the olefin just disappears after 30 hours--it doesn't appear
to have any appreciable half life.
For a chemical to have a direct effect, it must be present in the
organism. The neuroactive IMI metabolites, based upon C14 tracing, do not
appear to be present to any bioactive degree after a few days.
This clear finding appears to refute the hypothesis of irreversible
binding. Can anyone explain otherwise?
Now, that doesn't mean that there wasn't some other lasting effect, which I
will discuss in my next post. But can we get Suchail's findings first
behind us. Is there any reason for us to dispute that the neuroactive
metabolites are indeed quickly cleared?
--
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com
***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software. For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html
|
