The Mystery Of Mad Cow Disease (BSE)? Watch

imzir
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After reading Dying For A Hamburger there were a few questions that were bugging me.

How did the first infectious prion come to exist?

How does cannabilism cause PrP*(C) turn into PrP*(Sc) . Wouldnt it just be caused by a regular mutation from another factor?

There must be some farmers who secretly continue to feed their cows the left overs of other cows (although they are allowed to be fed chicken and some other animals) and still we dont have an outbreak of prion-diseases.
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atheistwithfaith
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(Original post by imzir)
After reading Dying For A Hamburger there were a few questions that were bugging me.

How did the first infectious prion come to exist?

How does cannabilism cause PrP*(C) turn into PrP*(Sc) . Wouldnt it just be caused by a regular mutation from another factor?

There must be some farmers who secretly continue to feed their cows the left overs of other cows (although they are allowed to be fed chicken and some other animals) and still we dont have an outbreak of prion-diseases.
Some of the exact mechanisms of prion-diseases are still disputed.

The first infectious prions were probably caused by a chance mutation in some prehistoric human - who perhaps even got it from another animal. There is some suggestion that cannibalism was much more widespread in pre-history and that prion diseases were quite common (all it takes is that the one person with the original misfolded prion to be cannibalised and then everyone who eats him to potentially developed their own prion disease). This would create a selective pressure to develop resistance to the prions - and it may be that it died out as a disease due to this and also due to changing attitudes about cannibalism.

The mutated prion protein actually catalyses a conformational change in NORMAL prion proteins. It doesn't have anything to do with transcriptional changes, or genetic modification. It is kind of like the ice-nine of the biochemistry world. (http://en.wikipedia.org/wiki/Ice-nine) If you consume mutant prion protein - the uptake of that protein can cause it to force aggregation of any normal prion proteins it encounters.

Why did this become so widespread though?

Well if you imagine one cow has a mutation that creates the PrP(Sc). This cow dies - but its impossible to tell that its death was caused by BSE as no-one is looking for it. This cow is recycled into feed that is fed to 10 cows. All those 10 cows consume the PrP(Sc) and this catalyses their PrP(C) to aggregate and form the mutant protein. Those 10 cows die from BSE and are made into feed for 100 cows... etc. etc.

Yes, I'm sure some farmers DO still practice cannibalistic feeding or feeding dead chickens etc. - but the probability of the mutation occurring by chance in a population is extremely low. Then you would have to multiply that by the probability that the one cow who gets the mutation is the same that is made into feed - and you can see that it would be statistically unlikely for it to happen. The problem began because this practice was so widespread and so the statistical likelihood of culling a cow which had the disease was much higher. Furthermore, farmers are so much more aware of the impact of the disease and are 1) less likely to do it, 2) more likely to spot the symptoms of BSE and deal with the problem.

Some good further reading:
http://en.wikipedia.org/wiki/Prion
http://www.nature.com/nature/journal...l/423127a.html
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Bslforever
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^ Fantastic response.

Prion diseases are definitely an interesting subject.
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imzir
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(Original post by atheistwithfaith)
Some of the exact mechanisms of prion-diseases are still disputed.

The first infectious prions were probably caused by a chance mutation in some prehistoric human - who perhaps even got it from another animal. There is some suggestion that cannibalism was much more widespread in pre-history and that prion diseases were quite common (all it takes is that the one person with the original misfolded prion to be cannibalised and then everyone who eats him to potentially developed their own prion disease). This would create a selective pressure to develop resistance to the prions - and it may be that it died out as a disease due to this and also due to changing attitudes about cannibalism.

The mutated prion protein actually catalyses a conformational change in NORMAL prion proteins. It doesn't have anything to do with transcriptional changes, or genetic modification. It is kind of like the ice-nine of the biochemistry world. (http://en.wikipedia.org/wiki/Ice-nine) If you consume mutant prion protein - the uptake of that protein can cause it to force aggregation of any normal prion proteins it encounters.

Why did this become so widespread though?

Well if you imagine one cow has a mutation that creates the PrP(Sc). This cow dies - but its impossible to tell that its death was caused by BSE as no-one is looking for it. This cow is recycled into feed that is fed to 10 cows. All those 10 cows consume the PrP(Sc) and this catalyses their PrP(C) to aggregate and form the mutant protein. Those 10 cows die from BSE and are made into feed for 100 cows... etc. etc.

Yes, I'm sure some farmers DO still practice cannibalistic feeding or feeding dead chickens etc. - but the probability of the mutation occurring by chance in a population is extremely low. Then you would have to multiply that by the probability that the one cow who gets the mutation is the same that is made into feed - and you can see that it would be statistically unlikely for it to happen. The problem began because this practice was so widespread and so the statistical likelihood of culling a cow which had the disease was much higher. Furthermore, farmers are so much more aware of the impact of the disease and are 1) less likely to do it, 2) more likely to spot the symptoms of BSE and deal with the problem.

Some good further reading:
http://en.wikipedia.org/wiki/Prion
http://www.nature.com/nature/journal...l/423127a.html
Like the previous poster said - great response - especially with the 'ice-9' touch.
You may want to know just out of interest the author was trying to suggest a link with alzheimers disease with eating beef.:rolleyes: (pffft) She believes that the dementia must also be a prion disease like Mad Cow Disease . I thought it was a ridiculous attempt - but what are your thoughts?
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