December 27, 2003

Mad cow words

Here's some interesting biomedical stuff on prions and mad cow disease. I've added a bit of lexicography for the obligatory language link.

Researchers at Columbia and MIT have found a protein in sea slug neurons (cytoplasmic polyadenylation element binding protein, or CPEB) that appears to use prion-like alternative forms as part of a mechanism for encoding long-term memories (NYT article). This could be a big deal for two reasons -- it might help explain how memories are formed (or more generally, how synapse-specific long-term facilitation works), and it might help explain where prions come from, and why they seem to form spontaneously in pretty much all animals. If true, either of these would be important enough to elevate CPEB (or some other nickname for these proteins) into the general vocabulary. It's likely -- given nature's thriftiness with basic mechanisms -- that similar tricks are used for lots of cellular switching functions, and thus may also be involved in other disease processes, making the discovery even more important. Some more links are here and if you subscribe to Cell here, here and here.

A lot of attention has been paid in the media (e.g. here) to the fact that the animal recently diagnosed with BSE was a "downer", i.e. was too sick to walk on its own when it arrived at the slaughterhouse. I agree with the note from Dr. Weinstein in this posting at ProMED-mail (scroll down to item [2]): "it makes me more than a little nervous to find out that obviously sick animals are still sent for slaughter to enter the human food chain."

This additional information provided by the ProMED-mail editors is just as distressing:

"Cattle are humanely stunned with a captive bolt stunner that
penetrates or piths the brain rendering the animal unable to feel
pain. However, the animal is not dead. Depending upon the speed of
the slaughter plant the animal remains alive, but unable to
comprehend or feel pain, for an average of 2 to 7 minutes before the
throat is cut, exsanguinating the animal.

During that 2 to 7 minutes the neurological tissue that captive bolt
compressed into the brain and into the blood stream can circulate
throughout the body, as long as the heart beats. The prion is smaller
than a red blood cell. Therefore, it would appear that the prion
agent can be in muscle tissue. (The Lancet, Sep 14, 1996, Letter to
the Editor)."

I had (falsely) assumed that cuts of meat away from the bone are likely to be safe, based on the earlier regulations in the U.K., which claimed on "the latest scientific advice" that properly boned beef can be eaten "with complete confidence." It sounds like "captive bolt stunners" are a really bad idea from the prionic point of view (I just made up the word prionic, by the way, but according to google, at least 921 others have engaged in anticipatory plagiarism).

This discussion makes it seem that Kosher or Halal beef would be safer in this respect. Of course, testing all slaughtered animals for prions would be even safer. Or becoming a vegetarian.

Neither the OED nor Encarta nor Merriam-Webster nor American Heritage has an entry for "captive bolt stunner," and all think that "downers" are (only) sedative drugs or depressing things, not cows who can't walk. I bet that downer soon makes it into jokes on late-night TV, if it hasn't already. I'm not sure about captive bolt stunner -- it depends on how the public discussion develops. I didn't bother looking for cytoplasmic polyadenylation element binding protein -- not even the Enzyme Commission has that one yet. Contrary to what I wrote here earlier, mad cow disease itself makes it into the online verions of the OED, Encarta, American Heritage and Merriam-Webster -- if properly looked up.

Update: this article from the Financial Times contains a very interesting -- and reassuring -- quantitative comparison with the British BSE/CJD episode of a few years ago:

In contrast to the single infected cow in Washington state, the UK has had 180,000 confirmed BSE cases.

As many as 750,000 infected animals may have entered the British food chain before the disease was recognised and proper precautions taken.

Even now, 11 years after the BSE epidemic reached its peak, several new cases a week are reported in British herds.

The incidence of variant CJD, the fatal human disease linked to eating BSE-contaminated meat, peaked in 2000. The cumulative death toll from vCJD stands at 138.

Although statisticians say it is too early to be sure how many people will die, most expect the eventual total to be about 200 to 300 - assuming that there is no secondary epidemic spread by infected blood supplies.

On that basis, even a few hundred cows with BSE in the US would not be likely to cause any human disease.

Posted by Mark Liberman at December 27, 2003 07:17 PM