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slkinsey

All About Prions and Food

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My mother, a scientist ever on the alert for reasons I shouldn't eat certain things, recently made me aware of this article from news@nature.com.

One assumption lies at the root of efforts to keep the meat we eat safe from mad cow disease: that tissues beyond an animal's brain, spinal cord and immune system are free of the prions that cause the disease.

A disturbing study now shows that assumption to be false. Researchers have found that if an animal falls ill with another infection, its immune response can carry large numbers of prions to organs throughout its body.

It had previously been thought that the prions were confined to the brain, spine and immune system meant that we thought it was safe to eat the other parts of susceptible animals in countries with BSE. The study upon which this article was based, Heikenwalder et al., Chronic Lymphocytic Inflammation Specifies the Organ Tropism of Prions, Science 2005 0: 11064601 (registration/subscription required) may change all that.

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Hmmm... I do like sweetbreads but this kind of ups the ante on whether to eat them or not...

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Hmmm... I do like sweetbreads but this kind of ups the ante on whether to eat them or not...

So that means that I can have your portion, right? :biggrin:

When we doing prion work in the lab, we knew that in the hamster model the infectious agent would first show up in the spleen before being detectable in the brain. Nothing of note in the thymus with respect to up-regulation.

As well, we know that there's a normal (non-infectious) isoform on the surfaces of T-cells; it could have a role in T cell activation but apart from a couple of papers that hinted at a couple of things, nothing could definitely be identified.

I'm still having beef. Won't eat brain but that has more to do with potentially avoiding MS-like conditions (mice get EAE when they're immunized with brain preps) and other things than vCJD.

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It never made sense that that the prions that are said to cause BSE were isolated to nerve cells. I am certain that the language used was selected to minimize the loss of confidence in the food supply.

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The accumulation of infectious prions occurs in the brain, but the preliminary detection of the infectious isoform can be first seen in splenocytes. I doubt that the wording chosen by the authors have anything to do with protecting the food supply; the nature.com bit reads like the typical simplified announcement that it's intended to be. I've asked my admin to pull Heikenwalder's article so that I can read it.

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The accumulation of infectious prions occurs in the brain, but the preliminary detection of the infectious isoform can be first seen in splenocytes. I doubt that the wording chosen by the authors have anything to do with protecting the food supply; the nature.com bit reads like the typical simplified announcement that it's intended to be. I've asked my admin to pull Heikenwalder's article so that I can read it.

Mmmmmmm... splenocytes!

If you're able to read the article, I'd love it if you could post your thoughts and maybe a short quote from the abstract.

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Prion disease found lurking in deer muscle

* 19:00 26 January 2006

* NewScientist.com news service

* Debora MacKenzie

The infectious prions that cause Chronic Wasting Disease, an infection similar to BSE that afflicts North American deer and elk have been found in the parts of the animals that people eat. No one knows if CWD can jump to humans, but if it does hunters in affected areas might be at risk.

See the full story here:

http://www.newscientist.com/article.ns?id=dn8638


Edited by Syre (log)

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Excuse my ignorance, but does cooking kill the little buggers? How about sauce? :biggrin:

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Nope, cooking does not kill the prions. Wash the exterior. At least, that is what I have always been taught. Grind your own meat. It tastes and cooks up much better.

I am still a bit skeptical concerning the finding in muscle tissue. Trying to figure out how the little buggers that only live in brain or spinal fluid managed to survive in a muscle. Seems to defy science.

MOO

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I am still a bit skeptical concerning the finding in muscle tissue. Trying to figure out how the little buggers that only live in brain or spinal fluid managed to survive in a muscle. Seems to defy science.

MOO

Prions are not really alive in any common sense of the word (they have no DNA or anything like that, and aren't really self-replicating). Prions are single proteins with an unusual structure which causes them to induce other proteins to fold incorrectly (which is how the disease spreads). It's certainly feasible that some particles would end up in other tissues.


Edited by Mallet (log)

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I am still a bit skeptical concerning the finding in muscle tissue. Trying to figure out how the little buggers that only live in brain or spinal fluid managed to survive in a muscle. Seems to defy science.

MOO

Prions are not really alive in any common sense of the word (they have no DNA or anything like that, and aren't really self-replicating). Prions are single proteins with an unusual structure which causes them to induce other proteins to fold incorrectly (which is how the disease spreads). It's certainly feasible that some particles would end up in other tissues.

That's a very helpful description - they are infectious macromolecules but are not fully understood.

As a lover of venison I would like to know which states and provinces have been flagged.

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Nebraska has been. But, I know enough poachers to be of the opinion that if CWD transmitted to humans, we would have seen a few cases in poachers by now.

I'll search PubMed a bit and see what I can see.

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cdc reprt

There appears to be no need for much concern (unless you are a hunter who eats a lot of wild game)

Even for them the watchword is be careful.

The risk to the rest of us is quite small--I would be more concerned with shellfish and unwashed vegetables (if one must be concerned).

Anyway--everyone should be aware, look at the facts and make up their own minds.

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Admin: Threads merged.

The infectious prions that cause Chronic Wasting Disease, an infection similar to BSE that afflicts North American deer and elk have been found in the parts of the animals that people eat

... in the 1990s it spread widely within the elk farming industry, jumped to wild deer, and now affects two provinces of Canada and 13 US states.

For the full article go to:

http://www.newscientist.com/article.ns?id=dn8638

It's not completely clear that you can die from eating venison, but it seems likely. It's hard to tell what meat is affected, and since it has spread within farmed animals, and since CWD spreads from animal to animal (unlike mad cow, but like scrapie in sheep), eating venison is a real risk.

Just so you know...

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This couldn't be more misleading.

First--there is a recent thread on this topic already.

Second--suggest you re read the article you cite and go to the CDC

web site for more information.

Third--The simple fact is you are more likely to die from eating raw shellfish or unwashed vegetables (and yes--from driving your car to the market) than you are from eating venison.

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Does this mean I should put down this deer burrito?

only if it was cooked in trans fat!!!

:unsure:

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This couldn't be more misleading.

In what way is it misleading?

- Chronic wasting disease prions were found in deer muscle.

- The disease is endemic to 13 states in the US.

- It has spread through farmed animals in the past.

- Prion diseases have been known to be contagious when eating infected animals (or people in the case of kuru).

- Prion diseases are universally incurable.

- Eating deer meat could expose you to prions.

Where's the error?

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Where's the error?

There are no reports of chronic wasting disease spreading to humans.

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Where's the error?

There are no reports of chronic wasting disease spreading to humans.

I'm still not sure that I would volunteer to eat meat from a known infected animal. :wink:

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This disease typically takes several years to develop, and it resembles other diseases so the source is often not obvious.

From the article:

It is also unknown whether people can catch encephalopathy by eating CWD-infected meat, as they can from eating BSE-tainted meat. Anecdotal reports that hunters develop the human prion disease CJD in unusual numbers have never been confirmed. State officials have issued warnings to hunters not to eat brain or spinal cord – the tissues most affected.

Except now they know it's also in muscle. That's the point of the report.

People have been warned not to eat tissue where prions have been found, now they've been found everywhere.

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Prions are not really alive in any common sense of the word (they have no DNA or anything like that, and aren't really self-replicating). Prions are single proteins with an unusual structure which causes them to induce other proteins to fold incorrectly (which is how the disease spreads).

Based on the reading I've done, this is an accurate summary of the prion theory. The one thing missing from the summary, however, is that it is a theory. While news reports and the writings of researchers who are heavily funded to do prion research are typically written so as to imply that the prion theory is incontrovertible, there are several other theories that could explain BSE, CJD and the like -- the so-called prion diseases.

One of the most vigorous skeptics of the prion theory has been the journalist Gary Taubes. One example of his writings on the issue can be read online on Slate in his story "Nobel Gas". Also good on this, and accessible to the layperson, is this debate on the Nova website -- it presents both sides respectfully. This recent summary on the Fox News site, while no doubt politically motivated, makes some interesting points as well.

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Based on the reading I've done, this is an accurate summary of the prion theory. The one thing missing from the summary, however, is that it is a theory.

FG, you're missing the nuance of the scientific theory, here.

From Wikipedia on theories...

http://en.wikipedia.org/wiki/Theory#Science

Further explanation of a scientific theory

As noted above, in common usage a theory is defined as little more than a guess or a hypothesis. But in science and generally in academic usage, a theory is much more than that. A theory is an established paradigm that explains all or much of the data we have and offers valid predictions that can be tested. In science, a theory is not considered fact or infallible, because we can never assume we know all there is to know. Instead, theories remain standing until they are disproved, at which point they are thrown out altogether or modified to fit the additional data.

Also, the sources you gave have good information, but do not cover some recent discoveries of prions and their pathologies. I'm searching them up, but my Scifinder login is having troubles. I'll post some once it's working.

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This is indeed disturbing. I am well aquainted with Koch's Postulates and the requirements for application for NIH etc. funding. It is disturbing that prions have not passed Koch's test. It is also disturbing that the scientific community has jumped on board without that test. It is even more disturbing that extensive funding has been skewed toward the "sexy new phenomenon" instead of a more moderate approach to search for a more conventional possible culprit. I guess that this confirms my long held belief that the media needs to stay out of real science. But, that will never happen.

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