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  • On December 22, 1984, cow number 133 on a farm in England's Sussex county began displaying

  • head tremors and a loss of coordination. It died a few months later on February 11, 1985,

  • while other cows began showing similar symptoms.

  • But it wasn't until September of that year when a government pathologist determined that

  • cow number 133 died from spongiform encephalopathy, later called bovine spongiform encephalopathy

  • (BSE) or, more commonly, mad cow disease.

  • And it would take several more years until scientists on the Spongiform Encephalopathy

  • Advisory Committee (SEAC) announced a possible link between the disease in cows and a similar

  • disease in humans (announcement made on March 20, 1996), sparking numerous efforts to curb

  • its spread, from banning British beef exports, to culling more than 4 million cows, to banning

  • blood donations.

  • While early predictions estimated the outbreak would kill thousands to tens of thousands

  • of people, there have only been 231 human fatalities worldwide, the majority within

  • the UK.

  • However, in 2013, a study was published where researchers tested over 32,000 appendices

  • from British people for the disease. And they worryingly found that 1 in every 2,000 people

  • in the UK is carrying the abnormal protein that causes the disease but are not showing

  • any symptoms. At least not yet.

  • Because an estimated 31,000 people are still carriers of the disease, preventative measures

  • like blood donation bans are still in place to avoid transmission. In the US, if you spent

  • more than 3 months in the UK from 1980 to 1996, you can't donate blood.

  • But as the pandemic rages on, blood shortages are dire. Hospitals are struggling to have

  • enough on hand. And since the 90s, new blood tests have been developed, and general cautions

  • in blood donations have advanced. So are these bans just overkill at this point, or are they

  • still necessary?

  • When BSE is transmitted to humans it's called variant Creutzfeldt-Jakob disease or vCJD.

  • This is just one of four major types of CJD, which are classified by how it is contracted.

  • In addition to variant CJD, there is sporadic CJD, the cause of which is unknown. However,

  • it is the most common, though still extremely rare, affecting 1 or 2 people per million

  • each year in the UK. Familial or inherited CJD occurs when someone inherits an abnormal

  • protein gene from their parent. And Iatrogenic CJD occurs accidentally in the medical setting.

  • One famous occurrence took place between 1958 and 1985 when thousands of children were injected

  • with human growth hormone collected from deceased donors who were unknowingly infected with

  • CJD.

  • CJD altogether is an extremely rare but fatal condition. It's caused by an abnormal, infectious

  • protein in the brain called a prion.

  • Prions are misfolded proteins with the ability to transmit their misfolded shape onto normal

  • variants of the same protein, inducing them to change their conformation as well, producing

  • a chain reaction that propagates the disease and generates new infectious material.

  • This is unique in the disease world. Before prions were discovered, it was believed that

  • all pathogens, like bacteria or viruses, had to contain nucleic acids to enable them to

  • reproduce - like DNA or RNA. The discovery of prions opened our eyes to a totally new

  • mechanism of disease.

  • And it is a particularly devastating one. Their misfolded shape creates brain damage

  • which quickly worsens over time.

  • Proteins are a very important part of our body's chemistry and are responsible for

  • the structure, function, and regulation of our tissues and organs.

  • They are large molecules made up of hundreds to thousands of organic compounds called amino

  • acids, which are attached in long chains or strings. These strings then fold into a 3D

  • shape. Thisprotein foldingis key, as each protein forms a specific shape that

  • allows it to perform its specific function. But if a mistake occurs, they can misfold,

  • or fold incorrectly, which is how an abnormal prion occurs.

  • There are many diseases caused by misfolded proteins. These can lead to a loss of function,

  • like in cystic fibrosis or Tay-Sachs disease, where one type of protein is misfolded and

  • therefore can't do its job. They can also stick together and cause clumps or plaques

  • which disrupt cell function. This is what scientists think may be the cause of neurological

  • disorders like Alzheimer's and Parkinson's. The other way prions devastate the brain is

  • by creating holes.

  • The infectious prion responsible for CJD converts normal proteins into an abnormal state. As

  • they build up, they cause brain cells to die, which releases more prions, and so on. In

  • areas where brain cells are killed, holes are created that make the brain sponge-like.

  • This type of brain damage causes symptoms similar to other neurological disorders, like

  • Dementia. In variant CJD, typically psychological symptoms that affect a person's behavior

  • and personality develop first.

  • In a few months, neurological symptoms develop, such as problems with coordination,

  • slurred speech, numbness, dizziness, and vision problems.

  • Over time, symptoms worsen until the patient is bedridden, completely unaware of their

  • surroundings, and can't communicate. The disease always progresses to death.

  • It took some years of research to nail down just how BSE spread from cow to cow and from

  • cow to humans. Eventually, they identified the source as their food, in both cases.

  • At the time, cows were often fed the remains of other cows. So, if they ate infected meat,

  • they too became infected. This led to a spread of BSE between cows, eventually reaching a

  • peak infection rate in 1993 of 0.3% of the UK national herd. The answer: ban the feeding

  • of meat-and-bone mix to farm animals.

  • Likewise, humans who ate beef containing infected nerve tissue contracted vCJD. While, initially,

  • it was thought that humans weren't affected by the disease, once it was made clear that

  • they were, bans were quickly placed on British beef exports, cattle over a certain age were

  • banned from the food chain, and at-risk cows were culled.

  • But eating infected beef isn't the only way humans can get vCJD. And this is where

  • the blood bans come in. There were four cases in the UK where a patient contracted vCJD

  • after receiving a blood transfusion.

  • Quickly, blood donation bans were put in place in countries like the U.S., Canada, Australia,

  • where people who have spent several months in the UK in the 80s and 90s are not allowed

  • to donate blood.

  • This seems like a broad stroke to ban millions of possible donors from just 4 instances of

  • blood transmission. But, for a long time, it's been necessary, because it's difficult

  • to know for sure if someone has vCJD. There is no blood test that can simply tell you

  • if you have it. Typically, a diagnosis is made by considering the patient's symptoms

  • and through neurological tests like MRI, which could show abnormalities typical of vCJD.

  • But even then, its not conclusive. The only way to confirm a diagnosis is by analyzing

  • the patient's brain tissue, which can only be done after they have died.

  • So scientists are aiming their sights here: if there was a way to test for vCJD in living

  • patients, then the ban could, in theory, be permanently lifted.

  • Because prion proteins are primarily found in the brain, they are hard to detect in blood.

  • So, researchers have developed a method to amplify the prions in blood samples called

  • protein misfolding cyclic amplificationor PMCA.

  • It works by taking advantage of the infectious prions' natural tendency to convert normal

  • proteins into an abnormal state. They did this by combining healthy proteins with a

  • small amount of infectious prions and agitating the mixture with sound waves. The sound waves

  • broke up the chunks of infectious prions, helping them to meet and infect normal proteins.

  • Studies have shown that this method can accurately detect vCJD in human blood samples and even

  • distinguish it from other types of neurological disorders, including sporadic CJD. In a 2016

  • study, it was found to correctly identify those with or without the disease 100% of

  • the time.

  • It can even detect it in patients who aren't showing any symptoms. In another study published

  • in 2016, their test detected vCJD prions in two patients 1.3 and 2.6 years before they

  • began showing any signs of the disease.

  • While these results are extremely promising, it is still early days. A clinically available

  • blood test has yet to be released.

  • Nevertheless, some scientists think its time to rethink the bans on blood donations, especially

  • with the implementation of safety measures like leukoreduction, a process which removes

  • white blood cells from blood, since white blood cells sometimes carry pathogens. Methods

  • like this have already helped to change the donation regulations in many countries around

  • those who are at high risk of sexually transmitted diseases like HIV and AIDS.

  • Increasing the number of potential donors is even more of a priority with the current

  • blood shortages caused by the Covid-19 pandemic.

  • Since the pandemic began, there have been alarming shortages of blood supplies. For

  • one American blood center, 31% of their locations have a one-day supply or less.

  • Luckily, changes have begun. In 2019, the Irish Blood Transfusion Service lifted their

  • ban, enabling some 10,000 individuals to now donate blood. And in 2020, the FDA lifted

  • their ban on US military veterans who served in Europe, now allowing 4.4 million more people

  • to donate.

  • With more testing and trials, soon this catch-all ban should be lifted in the US, saving hundreds

  • of thousands of lives with much needed blood.

  • How we treat our farm animals invariably affects our own lives. Mad cow disease, swine flu,

  • avian flu - many diseases of the modern age spread to us from livestock, and many diseases

  • like this happen due to the poor and overcrowded conditions in which we keep these animals.

  • Keeping the animals healthy, will in turn, keep us healthy - along with it being simply

  • the right thing to do.

  • Ending the practice of feeding COWS to OTHER COWS was a solid step in the right direction.

  • But there are still a lot of other bad practices, like pumping them full of antibiotics, that

  • need to come to an end.

  • Helping in this endeavor are new technologies being rolled out around the world, like this

  • silly robot named Astronaut, which is a fully automated milking system. It lets the cows

  • decide when they want to get milked, with no human input required, along with cleaning

  • the utter before the milking process. Being milked more often means the cows get sick

  • less often, they get fewer infections, and thus need fewer antibiotics. To learn more

  • about this elegant solution you should watch Milking Robots For Healthier Cows on CuriosityStream,

  • a part of the European Inventor Awards series. All episodes in the series are overviews of

  • cutting edge technology that is working to solve our most complicated problems.

  • CuriosityStream is a streaming platform with thousands of high quality documentaries like

  • this one. And now, CuriosityStream has partnered with us to offer an incredible deal. By signing

  • up to CuriosityStream you now also get a subscription to Nebula. Nebula is a streaming platform

  • made by me and several other educational YouTube content creators. It's a place where we can

  • upload our videos and podcasts ad free, and a place where we can experiment with new,

  • original content.

  • By signing up to the bundle deal, you will get access to both CuriosityStream and Nebula.

  • Our newest project is Modulus, a podcast where we talk to the people behind the science we

  • explore here on YouTube. The latest episode is about unlocking the intelligence of the

  • octopus, where we interview people who have spent their lives caring for and studying

  • these remarkable creatures You can learn about their stubborn personalities, and how aquarium

  • workers have to keep redesigning their enclosures because they always manage to escape, by listening

  • to Modulus ad-free on Nebula.

  • So by signing up at curiositystream.com/realscience, you will get a subscription to CuriostyStream

  • and a subscription to Nebula, for just $14.79 for the entire year. Signing up is also the

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  • Thanks for watching, and if you would like to see more from me the links to my instagram,

  • twitter, and patreon are below.

On December 22, 1984, cow number 133 on a farm in England's Sussex county began displaying

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Why British People Can't Donate Blood in America

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    joey joey に公開 2021 年 06 月 09 日
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