In <murray.44.000A41BA at molbiol.uct.ac.za> murray at molbiol.uct.ac.za writes:
>In an earlier article someone suggested that the transmission rout of the
>prion may be by ingestion and it was argued that this meant that the
>infective agent was in the blood (in very low titer). Isn't this being too
>presumptive in terms of being in the blood?
>Yo get back to ingestion, wouldn't it be on interest to test this
>transmission route (ie via ingestion) by seeing whether infected tissue when
>treated at a pH relative to that of a ruminants stomach is still able to
>infect mice, or even re-infect a healthy cow. This would clarify the
>ingestion route, blood location and neural infection.
Let me tell give you a tidbit that relates to your suggestion. Ground up
brains from scrapie infected sheep can transmit scrapie to sheep or mice
(via intracerebral injection) after boiling and even after formaldehyde
fixation. The prion is extremely stable. It seems totally clear to me
that BSE was introduced into Brit cattle herds when sheep that had died of
scrapie were ground up and processed into meal fed to cattle (turning
vegetarian cows into carnivores, in fact). And the practice of processing
cow offal into cattle feed probably spread the disease among cattle.
The critical questions for us humans are: 1) Is the bovine prion infectious
in people who eat cows' brains? And 2) is the bovine prion present in other
parts of the cow that we do eat. Because if 1 and 2 are both true then
you're in deep doo-doo.
The thing is, 1 is not necessarily true. Sheep scrapie prions are not
infectious in some animal species, so we can not take for granted that
bovine prions will be infectious in people. I am not going to volunteer
for *that* experiment, though.
Tom Thatcher | You can give a PC to a Homo habilis,
University of Rochester Cancer Center | and he'll use it, but he'll use it
ttha at uhura.cc.rochester.edu | to crack nuts.