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什么是朊病毒(海绵状脑病)?

Prions (Spongiform encephalopathy)

Spongiform encephalopathy can be broken down.
Spongiform encephalopathy可以拆开理解
Spongiform means sponge like, encephalo- refers to the brain,
Spongiform意思是像海绵一样 encephalo-指脑部
and -path refers to a disease process.
而-path则指疾病进程
So spongiform encephalopathy is a disease
所以spongiform encephalopathy是一种这样的疾病:
where the brain tissue degenerates
脑组织退行性变化
and healthy tissue gets replaced by clusters of tiny liquid filled,
健康脑组织被成簇的 内含少量液体的
thin-walled cavities called cysts,
薄壁小泡 即空泡所取代
making the brain look like a sponge.
它们使大脑看起来像海绵一样
The underlying cause of spongiform encephalopathy is
海绵状脑病的根本病因是
the accumulation of misfolded proteins called prions.
一种错误折叠的蛋白质 即朊病毒的积累
First, let’s review a tiny bit.
我们先稍微回顾一下
Proteins are made up of a long string of amino acids,
蛋白质是由氨基酸长链组成的
and the exact sequence of these amino acids is called the primary structure.
氨基酸的特定排列顺序称为初级结构
These long chains of amino acids can fold to form different shapes,
这些氨基酸长链能折叠成不同的形状
like an α-helix
比如α-螺旋
which is a right-handed coiled strand
这是种右手螺旋链
and a ß pleated-sheet
以及β-折叠
which is when the chain folds so that segments line up alongside each another.
就是氨基酸链折叠成段 各段相互堆叠排列
Each protein can contain multiple α-helices or ß pleated-sheets.
每个蛋白质分子可包含多个α-螺旋或β-折叠
Now, there’s a protein called Prion protein, or Prp,
目前发现了一种蛋白质 名为朊蛋白或Prp
which is encoded by the PRNP gene.
它由PRNP基因编码
This protein is 253 amino acid long
这种蛋白质有253个氨基酸
and is made up of mostly α-helices.
且主要由α-螺旋构成
It’s most commonly found on the cell membrane of neurons.
最常见于神经元的细胞膜上
Although the function of Prp is unknown,
尽管Prp的功能还未知
it’s thought that it might play a role in synapses between neurons
但它被认为可能在神经元之间的突触
and the uptake of copper into the cell.
以及细胞摄铜等方面发挥作用
When a prion protein is misfolded,
当朊蛋白错误折叠时
it changes from mostly having α-helices
它由以α-螺旋为主
to having a lot of ß pleated-sheets.
变成了以β-折叠为主
This new abnormal protein is called a “prion”
这种新的异常蛋白质被称为“朊病毒”
When the misfolded protein enters the cells of the nervous system
当错误折叠的蛋白质进入神经系统细胞
and interact with the normal prion protein,
且与正常的朊蛋白相互作用时
it acts as a template and induces misfolding in the normal prion proteins.
它可作为模板 诱导正常的朊蛋白错误折叠
These prions are also highly resistant to being broken down by proteases,
对于能降解异常蛋白质的蛋白酶
which are the enzymes that break down abnormal proteins.
这些朊病毒也高度耐受
As a result, these misfolded prion proteins cannot be easily broken down,
因此 这些错误折叠的朊蛋白不易被降解
they also cause normally folded proteins to misfold and become like them,
并使正常折叠的蛋白质像它们一样错误折叠
and they have an affinity for the brain.
且对脑组织具有亲和力
They’re basically like little ß-sheet filled zombies.
它们基本上就像充满ß-折叠的小僵尸
These misfolded prions accumulate within the cell and trigger apoptosis,
错误折叠的朊病毒在细胞内聚积 并触发细胞凋亡
which is programed cell death.
即细胞的程序性死亡
This is done with the help of 14-3-3 protein
这一过程由14-3-3蛋白协助完成
which is an intracellular protein that promotes apoptosis.
14-3-3蛋白是一种能促进细胞凋亡的胞内蛋白
When large numbers of cells start to die off,
当大量细胞开始相继死亡时
cysts start to form in the brain,
脑组织中开始形成空泡
and over time, this gives the brain its spongy appearance.
一段时间后 脑组织便呈现出海绵状外观
Additionally, the prions aggregate together on the membrane of the neurons,
此外 朊病毒聚集在神经元膜上
forming large plaques that are toxic to brain tissue.
形成对脑组织有毒性作用的大斑块
Now, the most common cause of spongiform encephalopathy is
海绵状脑病最常见的病因是
Creutzfeldt-Jakob disease or CJD.
克雅氏病 或简称CJD
And there are actually four types of CJD,
实际上有四种类型的CJD
familial or fCJD,
家族型CJD或称fCJD
variant or vCJD,
变异型CJD或称vCJD
iatrogenic or iCJD,
医源型CJD或称iCJD
sporadic or sCJD
散发型CJD或称sCJD
All four types cause spongiform degeneration of the cerebral cortex and cerebellum.
这四种类型的CJD都会导致大脑皮质和小脑海绵状变性
Familial Creutzfeldt-Jakob’s disease occurs when there’s a mutation in the PRNP gene.
家族型CJD发病是由于PRNP基因上存在突变
The most common mutation occurs at the 200th codon
最常见的突变位于第200个密码子
and causes the amino acid glutamic acid to be replaced by a lysine,
该密码子的谷氨酸被赖氨酸取代
and that’s enough to make the entire protein misfold.
这足以让整个蛋白质分子发生错误折叠
Variant Creutzfeldt-Jakob’s disease is caused
变异型CJD是由于
by eating the meat of cows with prions in the muscle tissue.
食用了肌肉组织中含朊病毒的牛肉
In cows, these prions cause bovine spongiform encephalopathy,
在牛身上 这些朊病毒也会引起牛海绵状脑病
which is more commonly called “Mad cow disease.”
也就是我们常说的“疯牛病”
When sheep are fed cow meat, the prion causes the disease Scrapie.
把这种牛肉喂给羊时 朊病毒又会引起“羊瘙痒病”
If a person eats the meat of affected cows or sheep,
如果人吃了被感染的牛肉或羊肉
the prions get absorbed through the intestines and get absorbed into the bloodstream.
这些朊病毒会经由肠道吸收 并进入血液循环
After that things get a bit unclear.
入血以后的机制就不太清楚了
It’s thought that the protein can somehow get through the blood brain barrier
有人认为朊病毒可以通过某种方式穿过血脑屏障
and then enters neurons by a process called adsorptive endocytosis.
然后通过“吸附内吞”过程进入神经元
Adsorptive endocytosis is a process where the plasma membrane of nerve cells folds inwards
吸附内吞是神经细胞膜向内折叠
to bring in substances that otherwise would not be able to cross the plasma membrane by themselves.
而把自身不能穿过细胞膜的物质吞入胞内的过程
Furthermore, since the misfolded proteins are in the blood of individuals with variant CJD,
此外 由于变异型CJD患者的血液含有错误折叠的蛋白质
if they try to donate blood,
如果患者想要献血
the prions can get transmitted to recipients of the blood which can spread the disease.
朊病毒可以传染给被输血者 从而传播该疾病
In fact people in the UK who have received a blood transfusion
事实上 正是因为这个原因
since January 1980are banned from donating blood for that very reason.
英国禁止1980年1月之后接受过输血的人献血
Iatrogenic Creutzfeldt Jakob disease is caused by medical procedures,
医源型CJD是在医疗操作中感染的
like when equipment for a procedure like a corneal transplant gets contaminated
例如 像角膜移植术之类的手术 其设备受到污染后
and infects healthy individuals.
感染了健康人
Finally, there’s sporadic Creutzfeldt-Jakob disease
最后是散发型CJD
which pops up in population randomly
它在人群中随机出现
without a clear cause.
病因尚不明确
This could be due to a spontaneous mutation in the 129th codon in the PRNP gene
可能是由于PRNP基因的第129个密码子自发突变
that replaces valine for a methionine.
导致其缬氨酸变成了蛋氨酸
People with this mutation are more likely to develop sCJD
携带这种突变的人更容易患上sCJD
and are also more susceptible to vCJD.
同时对vCJD也更易感
Another type of spongiform encephalopathy is Kuru,
另一种海绵状脑病是库鲁病
which is spread through cannibalism of infected flesh –
它是通过食用感染的人肉而传播的
in other words, when an individual eats the human flesh of an infected individual.
也就是说 一个人吃了感染者的肉而被感染
Kuru famously affected a tribe in New Guinea
库鲁病在新几内亚的一个部落很流行
who ate the brains of deceased family members.
那里的人会吃死去亲人的大脑
And in this way, the misfolded prion proteins pass from person to person.
就这样 错误折叠的朊蛋白在人与人之间传播
Since the symptoms are similar to those of CJD,
由于其症状与CJD相似
it is suspected that Kuru started
我们怀疑库鲁病的流行
when one of these tribes people acquired sCJD.
是从部落中的某个人患上sCJD开始的
Another disease is fatal familial insomnia
另一种疾病是致命性家族性失眠症
which is also caused by a mutation in the PRNP gene at codon 178
它也是由于PRNP基因第178位密码子突变引起的
where aspartic acid is substituted with asparagine,
该密码子的天冬氨酸被天冬酰胺取代
an interesting example of two different clinical diseases
这是一个有趣的例子:两种不同的疾病
developing from different mutations in the same gene.
由同一基因的不同突变引起
In fatal familial insomnia,
在致命性家族性失眠症中
misfolded prion proteins build up
错误折叠的朊蛋白主要堆积于
mainly in the neurons of the thalamus that help regulate sleep,
帮助调节睡眠的丘脑的神经元中
rather than causing the typical spongiform degeneration
而不像朊病毒引起的其它疾病
of the cerebral cortex and cerebellum that happen in other prion diseases.
表现为典型的大脑皮层和小脑的海绵状变性
Symptoms of spongiform encephalopathy
海绵状脑病的症状
might not show up for decades after prions have entered or formed in the body,
可能要等到朊病毒进入或存在于人体中数十年后才出现
but once symptoms start developing they tend to progress rapidly
但是一旦症状开始出现 进展往往很快
resulting in death within a year.
导致患者在一年内死亡
Early symptoms for CJD and Kuru involves motor symptoms like ataxia,
CJD和库鲁病的早期症状包括运动症状如共济失调
which is defined as lack of coordination of voluntary movements,
其被定义为缺乏自主运动的协调能力
and neurological symptoms like poor memory, and behavioral changes.
也包括记忆力差 以及行为改变等神经症状
Later stage symptoms include muscle weakness that makes it difficult to walk or stand,
后期症状包括肌无力引起的行走或直立困难
and myoclonus which is quick, jerky movement of the muscles;
以及肌阵挛 即肌肉急促而不流畅的运动
hiccups are an example of myoclonus.
打嗝就是肌阵挛的一个例子
Finally there’s dementia
最后的症状是痴呆症
which is where a person loses their mental functions
它是指患者丧失了认知功能
like memory, decision making, and reasoning.
如记忆 决策和推理能力
Lastly, in fatal familial insomnia,
最后 在致命性家族性失眠症中
people present with early symptoms of insomnia
患者表现出的早期症状有失眠
and exaggerated startle response
和夸张的惊吓反应
Eventually they can not sleep at all
最后他们完全不能入睡
and can experience hallucinations.
还会产生幻觉
Like the other prion diseases,
和朊病毒引起的其它疾病一样
they eventually develop dementia
患者最终会患上痴呆
and it eventually progress to death.
最终疾病进展导致死亡
Spongiform encephalopathy is diagnosed based on symptoms and MRI findings
海绵状脑病的诊断是基于症状和磁共振的检查结果
which include lesions in the cortex, basal ganglia, and thalamus.
包括皮质 基底节以及丘脑的病变
A lumbar puncture can also be done to obtain cerebrospinal fluid
也可以做腰椎穿刺以获取脑脊液
which might show an elevated levels of 14-3-3 protein
可能会显示14-3-3蛋白水平升高
which is a sign of significant neuronal destruction.
那是神经元严重破坏的标志
Ultimately, the definitive diagnosis of spongiform encephalopathy is done with a brain biopsy
最终 海绵状脑病的确诊是通过脑活检来完成的
which is typically done after a person dies.
这通常在人死后才进行
There are currently no treatments for prion diseases.
目前还没有治疗朊病毒疾病的方法
Supportive care should be given
应给予患者支持治疗
and genetic counseling should be offered for those with familial forms of the disease.
针对家族型患者还应提供遗传咨询
It is best to prevent transmission of the prions
阻止朊病毒传播的最好方式是
by restricting blood donation from those with the disease
限制患有朊病毒疾病的患者献血
and thoroughly decontaminating surgical equipment.
并彻底消毒手术设备
All right, as a quick recap,
好的 快速回顾一下
spongiform encephalopathy is a degenerative brain disease
海绵状脑病是一种脑部退行性疾病
caused by the accumulation of misfolded prion proteins.
由错误折叠的朊蛋白 即朊病毒堆积造成
This degeneration gives the brain a spongy appearance
这种退变使大脑呈现海绵状外观
and is seen in diseases like Creutzfeldt-Jakob disease and Kuru.
这在克-雅氏病和库鲁病这些疾病中可见
Prions can be transmitted by eating infected meat,
朊病毒可以通过进食被感染的肉
blood transfusion, corneal transplants,
输血 角膜移植
and contaminated surgical instruments.
以及被污染的手术器械传播
There is no treatment for these disease
这些病尚无治疗方法
and they always result dementia and eventually death
它们都会导致患者痴呆 最后死亡
so prevention of transmission is the key management strategy of the disease.
因此 防止传播是该疾病的关键应对策略
Hey yo, hope you enjoy our video on spongiform encephalopathy and prions.
希望你能喜欢我们关于海绵状脑病和朊病毒的视频
If I’m being honest, and I am,
说实话
I only know a tiny bit about this one going into it.
我只了解该疾病很少的一部分
I know it has something to do with cannibalism and something to do with zombies
我知道它和食人以及僵尸具有某种关联
and who is really interesting to find out
如果你有兴趣可以去探究
the specifics of how these two things connected.
这两样东西相互关联的具体情况
And speaking of the specifics,
说说视频制作情况
the script of this video is written by Demi Lola
本视频文案由Demi Lola创作
and then edited by Geffen and Rishi,
然后由Geffen和Rishi编辑
and Carrie did the illustrations,
Carrie负责插图
Tanner did the voice-over and I did the video editing.
Tanner负责解说 我负责视频编辑
And man, this one was interesting.
朋友们 有件事很有意思
You know people say,
人们总说
oh, he retains so much information, he’s got a brain like a sponge
他能记住这么多信息 他的脑子就像海绵一样
I’m never gonna be able to hear that phrase again
当我再听到这样的说法时
without thinking of the literal implication of
我不得不联想到字面意思的
someone’s brain being like a sponge.
“一个人的大脑像一块海绵一样”
It’s a little terrifing.
这有点吓人
But if you want to watch one of our other videos,
但如果你想观看我们的其他视频
maybe a lighter subject than this one,
也许比这个主题更轻松
go over to the OSMOSIS.ORG,
那么访问OSMOSIS.ORG
and you can find over a hundred videos that are exclusive to our prime service.
你可以找到我们的尊享服务 独家提供的100多个视频
Or you can check out the shop, we got more things coming down the line.
或者你也可以去商店看看 我们还有更多的东西
So stay tuned for those and stay tuned to the channel
所以请继续关注我们的网站和频道
for more videos similar to this one.
观看更多类似的视频
Bye.
再见

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视频概述

朊病毒是一种错误折叠的蛋白质,是造成海绵状脑病的主要原因。除此之外,朊病毒还能造成克-雅氏病,库鲁病,以及致命性家族性失眠症。

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审核员

审核员LJ

视频来源

https://www.youtube.com/watch?v=dXcLb4oCYfg

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