Every four seconds, someone is diagnosed with Alzheimer's disease.
平均每4秒就会有一个人被诊断患有阿兹海默症。
It's the most common cause of dementia, affecting over 40 million people worldwide,
这是造成痴呆的头号原因，影响着全球4千多万人，
and yet finding a cure is something that still eludes researchers today.
然而研究人员至今也没能找到治愈这种病的方法。
Dr. Alois Alzheimer, a German psychiatrist,
爱罗斯·阿兹海默博士一位德国精神病学家，
first described the symptoms in 1901 when he noticed that a particular hospital patient had some peculiar problems,
于1901年在注意到某一名患者的特有症状之后，首次描述了它。
including difficulty sleeping, disturbed memory, drastic mood changes, and increasing confusion.
这名患者的特有症状包括入睡困难、记忆力异常、剧烈的情绪波动以及越发严重的精神混乱。
When the patient passed away, Alzheimer was able to do an autopsy
当这名病人去世之后，阿兹海默得以解剖尸体，
and test his idea that perhaps her symptoms were caused by irregularities in the brain's structure.
从而测试他的理论，也就是导致她那些病症的原因是大脑内部的一些不规律的现象。
What he found beneath the microscope were visible differences in brain tissue
在他显微镜下发现的是大脑组织中可见的，
in the form of misfolded proteins called plaques, and neurofibrillary tangles.
错误折叠的蛋白质，也就是神经斑以及神经元纤维缠结。
Those plaques and tangles work together to break down the brain's structure.
这些神经斑和神经元纤维缠结共同作用，毁坏了大脑的结构。
Plaques arise when another protein in the fatty membrane surrounding nerve cells gets sliced up by a particular enzyme,
当神经细胞周围的脂肪膜里面的蛋白质被一种特定的酶切割成一片片
resulting in beta-amyloid proteins, which are sticky and have a tendency to clump together.
并形成有粘性的容易结块的β-淀粉样蛋白时，神经斑就形成了。
That clumping is what forms the things we know as plaques.
结块的时候就产生了我们所知道的“神经斑”。
These clumps block signaling and, therefore, communication between cells,
这些块状的东西会阻挡信号传递，因此阻挡了细胞之间的交流，
and also seem to trigger immune reactions that cause the destruction of disabled nerve cells.
貌似还引发了导致受损的神经细胞毁灭的免疫反应。
In Alzheimer's disease, neurofibrillary tangles are built from a protein known as tau.
在阿兹海默症中，神经元纤维缠结来源于一种名为“tau”的蛋白。
The brain's nerve cells contain a network of tubes that act like a highway for food molecules among other things.
大脑神经细胞包含了一个由很多管道组成的网络，这些管道像是食物分子在其他物质中的高速公路。
Usually, the tau protein ensures that these tubes are straight, allowing molecules to pass through freely.
通常，tau蛋白会确保这些管道的笔直顺畅，好让各种分子自由通过。

But in Alzheimer's disease, the protein collapses into twisted strands or tangles,
但得了阿兹海默症后，这些蛋白扭曲成一束束或缠结在一起，
making the tubes disintegrate, obstructing nutrients from reaching the nerve cell and leading to cell death.
造成那些管道的分解，使得营养不能到达神经细胞，从而导致细胞的死亡。
The destructive pairing of plaques and tangles starts in a region called the hippocampus,
神经斑和神经元纤维缠结的共同作恶始于一个叫做海马体的区域，
which is responsible for forming memories.
这个区域专门负责记忆的形成。
That's why short-term memory loss is usually the first symptom of Alzheimer's.
这就是为什么短期记忆丧失通常是阿兹海默症的第一个症状。
The proteins then progressively invade other parts of the brain,
接着这些蛋白会逐渐侵犯大脑的其他部位，
creating unique changes that signal various stages of the disease.
阿兹海默症的各个不同阶段的特殊症状逐渐出现。
At the front of the brain, the proteins destroy the ability to process logical thoughts.
在大脑前面的部位，这些蛋白会破坏逻辑思考的能力。
Next, they shift to the region that controls emotions, resulting in erratic mood changes.
接着，它们转移到大脑控制情感的部位，从而导致不稳定的情绪波动。
At the top of the brain, they cause paranoia and hallucinations,
在大脑顶部，它们会造成妄想症和幻觉，
and once they reach the brain's rear, the plaques and tangles work together to erase the mind's deepest memories.
而一旦它们到达大脑后部，神经斑和神经元纤维缠结会共同作用，抹去大脑最深处的记忆。
Eventually the control centers governing heart rate and breathing are overpowered as well resulting in death.
最终，掌控心跳和呼吸的控制中心也会受到侵犯，并导致死亡。
The immensely destructive nature of this disease has inspired many researchers to look for a cure
阿兹海默症的这种巨大的破坏力，激发了很多研究人员去寻找一个治疗方案，
but currently they're focused on slowing its progression.
但是目前他们主要专注于研究如何延缓疾病恶化。
One temporary treatment helps reduce the break down of acetylcholine, an important chemical messenger in the brain
一个暂时的治疗方案可以减少乙酰胆碱的分解，乙酰胆碱是大脑里面的一种重要的化学信使，
which is decreased in Alzheimer's patients due to the death of the nerve cells that make it.
阿兹海默症病人由于制造乙酰胆碱的神经细胞的死亡而缺乏这种化学信使。
Another possible solution is a vaccine
另一个可能的解决方案是一种疫苗，
that trains the body's immune system to attack beta-amyloid plaques before they can form clumps.
这种疫苗可以训练身体免疫系统在β-淀粉样蛋白斑形成结块之前攻击它们。
But we still need to find an actual cure.
不过我们仍然需要找到一种真正的治疗方案。
Alzheimer's disease was discovered more than a century ago, and yet still it is not well understood.
阿兹海默症早在一个多世纪以前就已经被发现了，而我们至今却还没有完全了解它。
Perhaps one day we'll grasp the exact mechanisms at work behind this threat and a solution will be unearthed.
也许有一天我们会明白这个威胁背后的具体机制，并发现一个解决方案。