often only use the simplest structure.
The most powerful virus in the history of biology, with a 100% fatality rate. It cannot be steamed or cooked through, and it is incurable. The virus
is called prion . does not have DNA or RNA. It is just a strange protein.
In the 1980s, crazy cows appeared one after another in British pastures. They "danced" and finally exhausted themselves to death, falling to the ground and foaming at the mouth.
This is the mad cow disease that shocked the world. It was also this disease that made the world aware of prions .
Fresh Beef
The Curse of Cannibalism
Although the prion has the word "virus" in its name, it is essentially an protein , and its size is only 1% of the smallest virus in . The
prion only has , which contains about 250 amino acids, molecules, . Scientists have found a protein with a similar structure to it in the human brain - prion protein .
Prions will cause lesions in the organism's prion protein, causing problems in the organism's brain structure. The plump brain becomes as loose and porous as a sponge.
Infected organisms will twitch uncontrollably like having Parkinson's disease, and eventually die in pain. When he dies, he is like a zombie with an empty head.
Brain tissue after infection with prions
So how do prions infect prion proteins?
Since there is no genetic material , prions do not use host cells for gene synthesis . Instead, they adopt a method similar to missionary , allowing the normal prion protein to be bewitched by it, and finally become willing to become . Prion follower .
Scientists currently cannot explain why a piece of protein can cause symptoms that are more serious than nucleic acids.
In short, as long as the prion invades the brain , there is almost no possibility of survival. The mortality rate is close to 100%.
However, prions are not impossible to prevent. As long as you do not trigger its production mechanism, you can stay away from prions. The trigger mechanism of
is to go to and not cannibalize !
The mad cow disease that occurred in the UK in 1985 was caused by the feed fed to cattle containing beef ingredients.
It turns out that in order to save costs, the animal husbandry industry at that time would dry and break the scraps from the slaughterhouse, such as cow hooves, horns, cow heads, etc., and then mix them with forage for the cattle to eat.
Cows eat feed
Prions mainly exist in the brains of living things. is considered to be produced by prion protein mutation. If cows eat feed made of the same type, as long as one cow is sick, all the cows will be infected. .
And in this wave of infection, a new prion was refined, which can realize species crossing , such as being transmitted from cattle to humans .
The British authorities were initially confused about the cause of the disease and thought it was a form of rinderpest, so they burned sick cows. However, they failed to curb the spread of the virus.
Suffering cows
Because prions still have the ability to infect at 20 to 130℃.
In other words, if a piece of beef with mad cow disease is fried, steamed, and stewed for 4 hours, the person who eats it may still be infected with prions.
In fact, mad cow disease is not the first time humans have discovered prions. Scientists have noticed this strange protein long before, but they did not expect that it would eventually lead to a tragedy.
Cow breeding industry
Cannibal tribe
In the 1950s, there was a primitive tribe living on an island in the Pacific. The women and children among them would always suffer from a disease, dancing non-stop, twitching hands and feet, and finally Die with your eyes open.
The locals call this disease "Kuru disease". Because it mostly occurs in children, the tribe considers it a punishment from heaven.
An American doctor named Gaidushek went to the island to treat them, but could not find the cause of the disease. He even ate and lived with the tribesmen and was not infected.
Until one day, someone died on the island, and the doctor witnessed the local custom-dismembering the corpse and eating it..
The island where kuru disease occurred
It turns out that in the eyes of the locals, after a person dies, his relatives should eat him, so men eat the limbs, which will make them stronger; women and children eat the brain, so Will inherit wisdom.
Gaidushek was keenly aware that there must be some connection here, so he took away the brain tissue of a person who died of disease.
In the American laboratory, he injected the patient's brain tissue into the head of a chimpanzee . As a result, the chimpanzee developed "Kuru disease".
Gaidushek found that the brain tissue of these patients was different from that of normal people. It was more like a sponge , full of holes.
However, after searching for a long time, did not find the strange genetic material . Therefore, Gaidushek could not confirm the cause of the disease, but he was sure that it was related to the local custom of cannibalism.
Gedushek's orangutan experiment
In 1982, three years before the outbreak of mad cow disease, American scientist Stanley Prusina successfully isolated a protein that was different from the normal prion protein and existed beta fold state .
Normal prion protein does not have such a strange fold, but is in the α helical state . He called this abnormal folding state prion . This was also the first time that humans named it .
Prusiner discovered that the abnormal β fold will assimilate the normal α helix , so the normal prion protein mutates into a prion.
Prion protein and prion
The "Kuru disease" of the cannibal tribe at that time was because a person ate the brain tissue of another person, allowing the prion to enter the healthy person's body, and then it assimilated the normal brain cells into a folded state , corroding people's brains.
Because prions are widely present in the brain , women and children who eat their brains have become key targets of infection.
And after these infected people die, their corpses will continue to be eaten, causing this disease to be endless.
Brain tissue of kuru patients
The curse of mutation
Prusina found that prions mostly appeared in cannibalism, but during the outbreak of mad cow disease, humans were infected.
People who were infected with mad cow disease developed the same symptoms as "Kuru disease", which is medically called "variant Creutzfeldt-Jakob disease" .
Scientists felt that this matter might not just be a prion, so they conducted a thorough investigation of the entire livestock industry's feed and found that it turned out to be the mutated prion .
Yes, without DNA or RNA, prions can still mutate. The characteristic of the mutation is that β folds become more .
Mad cow disease destroyed the British breeding industry
It turns out that in the past 100 years of the development of animal husbandry, eating meat-based feeds has become popular among various herbivores.
The feed that cows suffering from mad cow disease eat includes not only cow scraps , but also sheep offal .
The original version of the prion for mad cow disease, , may have come from sheep .
Because in the 15th century, sheep in Europe suffered from sheep syndrome . That is, the sheep felt inexplicably itchy, rubbed their bodies everywhere, and finally the fur was worn out, and the skin became infected and died.
Sheep are one of the earliest domestic animals to have prions.
Scientists later discovered that this was sheep prion. Merchants were greedy for profit. They thought it was just a skin disease of sheep and was not a problem, so they made diseased sheep into feed and fed it to cattle. , thinking that different species will not be infected.
As a result, in European livestock farms, various animals ate each other's meat feed made from each other's bodies.
The result is that in the process of "you eat me, I eat you, the prion is sweet", a prion that can spread across species was refined.
eventually became zoonotic disease , breaking the boundaries of species.
The mad cow disease finally led to the World Health Organization to order that no more meat feed be fed to herbivorous animals.
Stanley Prusina won the 995 Nobel Prize in Physiology and Medicine for his research on prions.
Stanley Prusina
How to prevent and treat
Once infected with prions, there is no cure, and you can only watch the patient die in pain and turn into a zombie.
But this disease can be prevented and treated. The first thing is not to eat untested meat .
After the mad cow disease in the UK, the world rewrote a set of meat quarantine standards, so the meat purchased normally on the market is safe.
However, if you eat animals that have died of illness, the chance of contracting prions increases.
Quarantine meat
Secondly, be sure not to cannibalize your own kind. Modern civilized humans can do this, but ordinary animals cannot, especially wild animals. Cannibalism has always existed.
For example, the "zombie deer" that have swept across North America are caused by deer eating the bodies of their dead companions and causing prion infection.
Animals infected with prions are usually biologically eradicated and thrown into incinerators for ultra-high temperature burning .
In addition, the brain tissue after prion infection is almost the same as the brain tissue of Alzheimer's disease .
The difference is that Alzheimer's disease generally occurs in the elderly , while prions are not age-specific.
Normal brain (left) and Alzheimer's disease (right)
The emergence of such an abnormal "virus" in biological evolution has always been an indelible shadow on the tree of evolution.
