经济学人227:杀手在敲门 七个基因祸害无穷

 　　A killer¹ in close up

　　杀手在敲门

　　You can do a lot of damage with just seven genes²

　　七个基因，祸害无穷

　　EBOLA is a simple virus, but also a subtle one. The stringy looking particles consist of a genome wrapped up in two layers of protein. This long, thin package, along with a large protein called a polymerase, is packed into a membrane³ that is studded with a glycoproteins—that is, proteins with sugar stuck to them.

　　埃博拉病毒看似简单，实则精妙。由两层蛋白质包裹着由基因组组成的丝状体，形成长而薄的包膜，包膜上布满醣蛋白颗粒，所谓醣蛋白就是糖分子附着在蛋白质上。

　　When the virus infects a cell the polymerase makes copies of the genome and the cell is tricked into using these to make the proteins that the virus needs. These include two, called VP35 and VP24, which stymie⁴ interferons, a class of molecule⁵ that alerts the immune system to infection. VP35 prevents interferons from being made; VP24 stops their cries for help from being heard. The sugars on the virus's outside make it hard for other parts of the immune system to get to grips with; to confuse things more, the virus makes infected cells produce more glycoprotein than it needs for its coat, with the surplus simply secreted⁶ into the bloodstream. Antibodies which would otherwise attack the virus stick to this decoy protein instead.

　　当埃博拉病毒感染细胞时，病毒的聚合酶就复制基因组，并诱使细胞使用这些基因组制造病毒所需要的蛋白质。这种蛋白质有两种类型，分别叫做VP35和VP24，它们阻碍干扰素发挥作用，干扰素是一类能向免疫系统发出警示作用的细胞因子。VP35阻止细胞干扰素形成，VP24则阻碍免疫系统接受干扰素的警示信息。病毒外附着的糖分子阻止免疫系统的其他部分捕获该病毒；更麻烦的是，病毒使得被感染的细胞生成超过其表皮需要量的醣蛋白，于是，这些过剩的醣蛋白直接代谢入血液。于是，抗体只能附着在这些作为诱饵的醣蛋白上面，而不会攻击病毒。

　　杀手在敲门.jpg

　　Immune cells which the virus attacks in the bloodstream early on carry the infection to the liver, the spleen and lymph nodes. Symptoms may manifest themselves in a day or two or may wait weeks (see chart). Eventually the virus's spread triggers an immune overreaction known as a cytokine storm. Blood-vessel walls become leaky, blood pressure and core temperature drop, organs fail and the body goes into shock. Various combinations of those and other symptoms kill about 70% of those who get ill.

　　血液中先前被病毒攻击的免疫细胞携带感染元进入肝脏、脾脏和淋巴结。症状可能会在1天、2天或者等上1周后显示出来。最后，病毒的传播引发了免疫过载，这称为“细胞素风暴”。于是，血管壁开始渗漏，血压和体核温度下降，导致器官衰竭，身体休克。这些作用结合其它症状使得70%的患者死亡。

　　Some of the sick weather the storm, but most who survive infection do so by never getting to its direst straits. Some do not succumb⁷ at all: a study of people who had direct contact with patients during outbreaks in Gabon in 1996 showed that some had definitely been infected, but never fallen ill.

　　一些病人能挨过细胞素风暴，但是能在感染后活下来的人大多数靠的是没有遇到杀招，但有一类人根本就是命硬：一项针对1996年在加蓬爆发期间和病人直接接触的人群的研究表明：一些人绝对受到了感染，但从没有生病。

1 killer   

n.杀人者，杀人犯，杀手，屠杀者

参考例句：

• Heart attacks have become Britain's No.1 killer disease.心脏病已成为英国的头号致命疾病。
• The bulk of the evidence points to him as her killer.大量证据证明是他杀死她的。

2 genes   

n.基因( gene的名词复数 )

参考例句：

• You have good genes from your parents, so you should live a long time. 你从父母那儿获得优良的基因，所以能够活得很长。 来自《简明英汉词典》
• Differences will help to reveal the functions of the genes. 它们间的差异将会帮助我们揭开基因多种功能。 来自英汉非文学 - 生命科学 - 生物技术的世纪

3 membrane   

n.薄膜，膜皮，羊皮纸

参考例句：

• A vibrating membrane in the ear helps to convey sounds to the brain.耳膜的振动帮助声音传送到大脑。
• A plastic membrane serves as selective diffusion barrier.一层塑料薄膜起着选择性渗透屏障的作用。

4 stymie   

v.妨碍，阻挠

参考例句：

• Companies have been stymied by the length of time it takes to reach an agreement.由于耗时过长，各公司一直未能达成协议。
• Relief efforts have been stymied in recent weeks by armed gunmen.最近几周的救援工作一直受到武装分子的阻挠。

5 molecule   

n.分子，克分子

参考例句：

• A molecule of water is made up of two atoms of hygrogen and one atom of oxygen.一个水分子是由P妈̬f婘̬ 妈̬成的。
• This gives us the structural formula of the molecule.这种方式给出了分子的结构式。

6 secreted   

v.（尤指动物或植物器官）分泌( secrete的过去式和过去分词 )；隐匿，隐藏

参考例句：

• Insulin is secreted by the pancreas. 胰岛素是胰腺分泌的。
• He secreted his winnings in a drawer. 他把赢来的钱藏在抽届里。 来自《简明英汉词典》

7 succumb   

v.屈服，屈从；死

参考例句：

• They will never succumb to the enemies.他们决不向敌人屈服。
• Will business leaders succumb to these ideas?商业领袖们会被这些观点折服吗？