From: Randall Parker 

BTW, The feeding of animal brain material to cows in the United States was banned in
1997 in order to reduce the risk of prion infection.

The disease takes years to develop. Does anyone know how old this cow was that was
killed on Dec 9 2003 and found to be positive for the mad cow prions? Do cows live
for 6 whole years before being slaughtered? I'd have expected a shorter
period of time.

Or maybe the cow got it from its mother in gestation? Is that possible?

Also, a Canadian friend says live cows get shipped routinely between the
United States and Canada. Does Canada ban the feeding of animal brain
material to cows?

Also, a protein shape very similar to the prion state of proteins may be involved in
memory formation:
http://www.eurekalert.org/pub_releases/2003-12/wifb-cm121703.php
Public release date: 24-Dec-2003
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Contact: David Cameron or Kelli Whitlock newsroom{at}wi.mit.edu
617-258-5183
Whitehead Institute for Biomedical Research
'Mad cow' mechanism may be integral to storing memory
CAMBRIDGE, Mass. (Dec. 24, 2003) – Scientists have discovered a new process for how
memories might be stored, a finding that could help explain one of the
least-understood activities of the brain. What's more, the key player in
this process
is a protein that acts just like a prion – a class of proteins that includes the
deadly agents involved in neurodegenerative conditions such as mad cow disease.

The study, published as two papers in the Dec. 26 issue of the journal Cell, suggests
that this protein does its good work while in a prion state, contradicting a widely
held belief that a protein that has prion activity is toxic or at least
doesn't function properly.

"For a while we've known quite a bit about how memory works, but we've
had no clear
concept of what the key storage device is," says Whitehead Institute
for Biomedical
Research Director Susan Lindquist, who coauthored the study with neurobiologist Eric
Kandel at Columbia University. "This study suggests what the storage
device might be
– but it's such a surprising suggestion to find that a prion-like activity may be
involved."

Central to a protein's function is its shape, and most proteins maintain only one
shape throughout their lifetime. Prions, on the other hand, are proteins that can
suddenly alter their shape, or misfold. But more than just misfolding themselves,
they influence other proteins of the same type to do the same. In all known cases,
the proteins in these misfolded clusters cease their normal function and either die
or are deadly to the cell – and ultimately to the organism.

For this reason, Kausik Si, a postdoc in Kandel's lab, was surprised to find that a
protein related to maintaining long-term memory contained certain distinct prion
signatures. The protein, CPEB, resides in central-nervous-system synapses,
the junctions that connect neurons in the brain. Memories are contained
within that intricate network of approximately 1 trillion neurons and their
synapses. With experience and learning, new junctions form and others are
strengthened. CPEB synthesizes proteins that strengthen such synapses as
memories are formed, enabling
the synapses to retain those memories over long periods.

For the study, the team extracted the CPEB protein from a sea slug. This
lowly creature has achieved high status in neurobiology because its neurons
are so big,
they can be manipulated and turned into unusually powerful investigative tools. The
researchers fused this CPEB to other proteins that would serve as reporters
of activity, and then observed its behavior in a variety of yeast models.
The researchers discovered that CPEB altered its form and caused other
proteins to follow
– functioning exactly like a prion. A second unexpected finding was that CPEB carried
out its normal function – protein synthesis – when it was in its prion state.

"This is remarkable not just because the protein executes a positive
function in its
prion-like state," says Lindquist. "It also indicates that prions
aren't just oddballs of nature but might participate in fundamental
processes."

The finding contradicts the notion that converting to a prion state is a bad thing,
says Kandel. "We show instead that the normal state of CPEB may be the
less active
state, and the prion state may be the effective way of utilizing the normal function
of the protein."

The work suggests it's possible that in mammalian neuronal synapses, CPEB's prion
properties may be the mechanism that enables the synapses and nerve cells to store
long-term memory, a theory the researchers plan to investigate next. Theoretically at
least, prions are perfect for this, says Lindquist. Prions could shift into this
state quickly without the energy-intensive cellular mechanics that fuel most protein
synthesis. The prion state is very stable and can maintain itself for
months, even years.

But, "We still need to demonstrate that this prion mechanism operates
not just in
yeast but in neuron cells," says Kandel.

Lindquist believes that these findings will not be the last time prions are
discovered to have normal biological roles. In fact, she has long
speculated that
researchers will discover them to be essential to many cellular functions. Kandel
adds that he wouldn't be surprised if this sort of prion mechanism was discovered in
areas such as cancer maintenance and even organ development.

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