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I have to disagree with Dr. White here (even though I've never slided anyone's brain like she has). It is not a given that everyone's brain degenerates substantially with aging. Look at Arthur Clarke and Ray Bradbury, sharper than you and I in their 70s and 80s and will probably die as sharp as they are now.
As for the mad cow disease, or new variant Creutzfeld Jacob disease in humans, the infected individual actually doesn't get to grow too old to become ill. It generally takes about 15-20 years for the disease to manifest itself. So if one is infected at 20 years old, he could be dead by 40.
As for the mad cow disease, or new variant Creutzfeld Jacob disease in humans, the infected individual actually doesn't get to grow too old to become ill. It generally takes about 15-20 years for the disease to manifest itself. So if one is infected at 20 years old, he could be dead by 40.
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Scrapie is an old disease, generally considered the origin of all the prion disease we see now. First, the brain of scrapie-infected sheep were fed to cows as a protein source, which infected cows. From scrapie prion, cows got bovine spongiform encephalopathy (ie, mad cow dz). Just exactly how the prion jumped species, we don't really know. Then, cows with BSE were fed to humans, who then caught nvCJD. The recent news was that a lot of people may be carrying around the prion without knowing it.
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This is turning into a medical horror novel or something. See the link below:
http://edition.cnn.com/2004/HEALTH/05/2 ... .cjd.reut/
http://edition.cnn.com/2004/HEALTH/05/2 ... .cjd.reut/
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那就是摇头丸。医学上还没能证明它有什么坏处,造成死亡的多数是不纯或者服用者脱水。倒是已经发现它会导致脑部损伤, 但是问题是,它留下痕迹的那块脑子还没发现有什么作用--就是说,它在你不知干吗的一块脑子里留下些不知道什么。所以吃的照吃,不吃的照不吃。pomo wrote:我想起来前几天看电视,说美国流行一种药物叫“狂喜”,可以让人HIGH,却暂时没发现什么恶果,政府很是烦恼,故意危言耸听……tiffany wrote:哎,我记得当年安非他命的副作用还没发现的时候,大家们拿来当咖啡一样的用,结果有个英国首相就做出了很多疯狂举动。后来发现是吃药吃出来的。
要是真有这类药物,848造福于民的,至少不会有人因PSDT(俺不知拼得对不)啥的郁闷了
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I'm not prion, but I'll jump in anyway to offer a bit of what I know. Exactly how prion causes disease and how it jumps species and which species it jumps to and from are all questions not answered by science so far. There is a strong suspicion that the infectious process is determined by both parties -- the infectious agent (prion) and the host (sheep, cow, or primates). One needs to remember that prion does not behave exactly like viruses or bacteria (well, it's a little more like virus than bacteria), and the mechanisms are still very much a mystery. Therefore we cannot always expect prion to behave in similar ways as virus or bacteria.
The phonemenon of species-jumping has been seen in virus too. Simian immunodeficiency virus, for example, has existed for a long time before jumping to humans as HIV. Same with avian flu. Sometimes, a virus may be perfectly barred from a species (eg, primates) for thousands of years, but suddenly a strain acquires a mutation that allows it to jump to humans. To make it more complicated, it is possible that the transmission requires a certain genetic makeup in the host, ie, you might be susceptible to the infection but I am not because your brain protein is slightly different from mine.
The phonemenon of species-jumping has been seen in virus too. Simian immunodeficiency virus, for example, has existed for a long time before jumping to humans as HIV. Same with avian flu. Sometimes, a virus may be perfectly barred from a species (eg, primates) for thousands of years, but suddenly a strain acquires a mutation that allows it to jump to humans. To make it more complicated, it is possible that the transmission requires a certain genetic makeup in the host, ie, you might be susceptible to the infection but I am not because your brain protein is slightly different from mine.
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