rdudley+ at pitt.edu
Thu Nov 12 08:26:40 EST 1998
> Could some one in the group explain this to me? I understand it is not a living
> micro organism or plant. How is this true? How is it spread?
CJD and related diseases, such as BSE ("mad cow"), are a class called spongiform
encephalopathies. These have been detected in sheep, cows, humans, and mink.
There is good evidence that these diseases can be transmitted between members of
the same species--human cases in the South Pacific (I think), where it was common
for close family members to eat the brains of the early departed to show respect.
These family members would be infected, die, other members would eat the brain,
etc. I forget the name the villagers gave to the diseas, but the information is
out there on the internet. There is suspected evidence that there can be
cross-species transmission. The recent scare in England stems from feeding the
ground up remains of sheep that were killed because of the "mad sheep" version of
the disease, then feeding beef from cows that were infected, possibly in the form
of hamburgers, to people, who then became infected. This is still a big maybe, but
we don't understand a lot about the disease just yet. The good news is that since
the USDA was formed, there has never been a case of BSE in the US.
The diseas is believed to be caused by a single protein in the brain. Most
proteins exist in a state that is heavily folded, to bring certain parts close to
other parts, and still have a lot of flexibility in the molecule to do its job.
This is called the native state. The native state is assumed to be the most
thermodynamically favorable state--that is, in your body's conditions, the protein
will "want" to always be in its native state. However, the difference in
conditions required to change a protein form the native state to a non-native state
may be very slight. What people think is happening is a few prions fold from their
helpful native state into their non-native dangerous state. In this dangerous
state, they aggregate and form long rods of proteins that act like daggers from
inside the cell. Since the cells are neurons found in the brain, they kill the
cells and impair brain function, causing all sorts of maladies, most notably a
dementia. If you look at a piece of brain from an infected person under the
microscope, it looks like a sponge, or swiss cheese, rather than a solid piece of
tissue it should look like (hence the name "spongiform"). Alzheimer's is caused by
a protein that aggregates in the same way--a possible link is being investigated,
but as of yet, there doesn't appear to be any.
The guy who first put forth this theory is Stanley Pruisner (sp?). He won the
Nobel Proze last year, and you can find a walth of info searching for "prion" on
Hope this helps!
--- --- --- -- -- -- --- --- ---
Richard J. Dudley (rdudley+ at pitt.edu)
Research Specialist V
Dept. of Cell Biology and Physiology
University of Pittsburgh
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