2018考博英语阅读经济学人文章每日精析：对抗衰老

　　“The technique itself is kind of gross and crude,” admits Michael Conboy, a biologist and parabiosis researcher at the University of California, Berkeley. Perhaps for that reason, research had more or less died out by the late 1970s. These days, though, it is back in the news—for a string of recent discoveries have suggested that previous generations of researchers were on to something. The blood of young animals, it seems, may indeed be able to ameliorate at least some of the effects of ageing. And the technique is promising enough to have spawned human clinical trials.

　　加州大学伯克利分校的生物学家和联体共生研究员迈克尔·康博伊(Michael Conboy)承认，“这种技术本身有些野蛮和倒人胃口。”也许是这个原因，到了20世纪70年代后期，这方面的研究已差不多销声匿迹。不过，最近这种技术又重新回到人们的视线里，因为近期有一连串发现显示，前几代研究人员其实已经摸索到了一些重要的东西。看起来，年轻动物的血液好像确实能够缓解至少一部分的衰老的影响。以该技术的前景，足以催生这方面的人体临床试验。

　　No jokes about vampires, please

　　拜托，别拿吸血鬼开玩笑

　　This modern interest in parabiosis dates back to 2005, when Dr Conboy (who was then at Stanford University), his wife Irina, and a group of other Stanford researchers published a paper in Nature. In it they described joining mice aged between two and three months with members of the same strain that were 19-26 months old. That is roughly equivalent to hooking a 20-year-old human up to a septuagenarian. After five weeks, the Conboys and their colleagues deliberately injured the older mice’s muscles. Usually, old animals heal far less effectively from such injuries than young ones do. But these mice healed almost as well as a set of young control animals. The young blood had a similar effect on liver cells, too, doubling or tripling their proliferation rate in older animals.

　　联体共生的现代研究始自2005年。当时在斯坦福大学工作的康博伊(Conboy)和妻子伊琳娜(Irina)以及斯坦福的其他几位研究人员在《自然》杂志上发表了一篇论文。文章描述了对两至三个月大的小鼠和19至26个月大的同种小鼠所做的联体试验。这大致相当于把20岁的年轻人与七旬老人联体。五周后，康博伊夫妇和同事故意损伤了受试老年鼠的肌肉。通常，老年动物受到这类损伤后的恢复速度远不及年轻动物。但这些老年小鼠的痊愈效果堪比对照组的年轻小鼠。年轻血液对肝细胞也有类似效果，使老年小鼠体内肝细胞的增殖速度提高了一或两倍。

　　Since then, a torrent of papers have shown matching improvements elsewhere in the body. No one has yet replicated the finding that young blood makes superannuated mice live longer. But it can help repair damaged spinal cords. It can encourage the formation of new neurons in mouse brains. It can help rejuvenate their pancreases. The walls of mouse hearts get thicker as the animals age; young blood can reverse that process as well.

　　自此，有大量论文显示动物体内其他方面也存在类似的改善。但至今尚未有研究重复出年轻血液延长老年鼠寿命这一结果。但研究证明年轻血液有助修复受损的脊髓，还可促进小鼠的大脑形成新神经元，帮助它们的胰腺恢复活力。小鼠的心脏壁会随年龄增长而变厚，年轻的血液还可逆转这一过程。

　　The effects work backwards, too. Old blood can impair neuron growth in young brains and decrepify youthful muscles. Intriguingly, the phenomenon even seems to operate across species. In April Tony Wyss-Coray, also at Stanford, showed that infusing old mice with blood from the umbilical cords of infant humans improved their performance on memory tests.

　　其中也存在逆向效果。老年血液会损害年轻大脑中的神经元生长，并使年轻的肌肉衰老。有趣的是，这种现象似乎甚至可以跨物种显现。今年4月，同为斯坦福大学研究人员的托尼·魏斯-克雷(Tony Wyss-Coray)表示，老年小鼠输入人类婴儿的脐带血后，在记忆测试中的表现有所提升。

　　There have been enough results, says Janet Lord, who runs the Institute of Inflammation and Ageing at Birmingham University, in Britain, to remove any doubt that something impressive is happening. But finding out exactly what is trickier. The working theory is that chemical signals in young blood are doing something to stem cells in older animals. Stem cells are special cells kept in reserve as means to repair and regrow damaged tissue. Like every other part of the body, they wear out as an animal ages. But something in the youngsters’ blood seems to restore their ability to proliferate and encourages them to repair damage with the same vigour as those belonging to a younger animal would.

　　英国伯明翰大学炎症和老化研究所(Institute of Inflammation and Ageing)的负责人珍妮特·洛德(Janet Lord)说，现有研究结果足以让人消除怀疑，确信有一些非同一般的因素在起作用。但要确切说明到底是什么就不那么容易了。初步的理论是，年轻血液中的化学信号对年老动物中的干细胞施加了某种影响。干细胞是储备在体内的特殊细胞，用于修复和再生受损组织。就像身体其他各部分一样，干细胞也会随动物的年龄增长而老化。但年轻血液中的某些成分似乎能令干细胞恢复增殖能力，并促进它们像年轻动物的干细胞那样有效地修复受损组织。

　　Nobody yet knows exactly what that something is, but people are looking hard. In all probability, says Dr Lord, it is not one thing at all, but dozens or hundreds of hormones, signalling proteins and the like, working together. Researchers have been comparing the chemical composition of old and young blood, searching for those chemicals that show the biggest changes in level between the two. These include oxytocin (a hormone better known for its role as a transmitter of signals between neurons); two proteins called GDF-11 and TGF beta-1, both of which are already known to affect cell behaviour; and B2M, another protein which, among other things, affects the body’s ability to absorb iron from food.还没有人确切知道到底是什么在起作用，但人们正在仔细分辨。洛德表示，很有可能不止一种，而是数十或数百种激素、信号蛋白及类似物质在共同作用。研究人员比较了年老及年轻血液的化学成分，寻找两者间含量水平差异最大的化学物质。这其中包括催产素，这种激素更为人熟知的作用是在神经元之间传递信号;还有名为GDF-11和TGF beta-1的两种蛋白质，已知两者均会影响细胞的行为;另外还有一种名为B2M的蛋白质，它的作用之一是影响身体从食物中吸收铁的能力。

　　Even with a list of targets, working out what is going on is hard, says Richard Lee, a cardiologist at Brigham and Women’s Hospital in Boston, Massachusetts. Blood is complicated stuff, and the tools available to analyse it are far from perfect. Dr Lee’s own work is a good example. In 2014 his group suggested GDF-11 as a possible rejuvenating factor. The following year a team at Novartis, a big pharmaceutical company, said that they were unable to replicate those results. The trouble, said the group from Novartis, was that the test used by Dr Lee’s team was sensitive to proteins besides GDF-11, messing up the results. Dr Lee’s team replied within months that, no, it was in fact the Novartis test that was flawed, because it was itself picking up extra proteins. And there, at the moment, the matter stands.

　　即便有了目标清单，要弄清楚发生作用的过程还是很难，马萨诸塞州波士顿市布列根和妇女医院(Brigham and Women’s Hospital)的心脏病专家理查德·李(Richard Lee)说道。血液是很复杂的东西，现有的分析血液的工具也远非完美。李博士自己的研究便是个好例子。2014年，他的团队发现GDF-11有可能是一种“返老还童”因子。第二年，大型制药公司诺华(Novartis)的一个团队称无法重复该结果。诺华团队表示，问题在于李博士团队的测量方法对GDF-11以外的蛋白质也有敏感性，影响了测量结果。几个月后，李博士的团队予以否认，称有问题的其实是诺华团队的测试，因为正是该团队的测试在过程中混入了其他蛋白质。目前此事件尚无进一步发展。

　　There are further possible explanations for parabiotic rejuvenation besides blood chemistry. One is that older animals may also benefit from having their blood scrubbed by young kidneys and livers, which mere blood transfusion would not offer. A paper published by the Conboys and their team in 2016, which described blood exchanges that were done in short bursts (thus eliminating the possibility of such scrubbing) reported rejuvenating effects, but ones that were not as widespread as those obtained by full-on parabiosis.

　　除了血液化学方面的因素，联体共生的“返老还童”现象还有其他可能的解释。其一是，老年动物可能也同时受益于年轻肾脏和肝脏对血液的净化作用，而这单靠输血是无法实现的。康博伊及其团队在2016年发表的一篇论文称，在短时间内完成的血液交换(因而消除了上述净化过程的可能性)具有复壮的效果，但不如全面联体共生后那样全面。

　　Another idea is that cells from the young animal, rather than chemicals in its blood, could be doing some of the work. By modifying the genes of a mouse so that its cells glow under ultraviolet light, researchers can track where those cells end up when the mouse in question is linked to another. They have found that only a few cells from a younger mouse take root in an older animal it is linked to. This does not quite rule the theory out, says Irina Conboy, for the number of cells may not reflect their importance. Immune-system cells, for instance, multiply rapidly when needed. And they are precisely the sorts of cells that might help an older animal.

　　另一个想法是，也许是来自年轻动物的细胞发挥了些许作用，而非血液中的化学物质。研究人员改造了一只小鼠的基因，使其细胞能在紫外线下发光，从而在这只小鼠跟其他小鼠联体时跟踪这些细胞的去向。他们发现，在与老年鼠联体时，只有少数幼鼠的细胞转移到老年鼠体内。但这并不能完全推翻上述理论，伊琳娜·康博伊(Irina Conboy)说，因为细胞数量不一定反映其重要性。举个例子，免疫系统细胞在必要时可迅速繁殖。它们正是那种可能会对老年动物有所帮助的细胞。

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