while many search for the proverbial fountain of youth, you might be wondering why do we age in the first place? 关於众所皆知的年轻的泉源虽然有很多研究，你可能压根还是想知道我们为什麽会变老 (proverbial硬插进去显得多余，不知道要不要直接省略) What is it about our bodies or cells biologically that causes us to grow old? There is a variety of internal and external factors such as diet, exercise or environment stress which all contribute to cell damage and repair and effect the rate of aging. 生物学上，是有关身体和细胞的什麽让我们变老? 有许多不同的内外因素像是饮食，运动或是环境的压力都会造成细胞的伤害和修复且影响 老化的速率。 (第一句很不确定是这样翻) But the suprising truth is that apart from these, we actually have a biological clock buried with our genetic makeup. And this clock can only run for so long, in other words we are programmed to die. Your body is made up of trillions of cells which are constantly going through cell division and every time they divide they make a copy of their DNA as well. 但惊人的真相是除此之外，我们有个埋藏在基因构造的生理时钟。这个时钟可以运行很久 ，也就说我们是预定好要死的。你的身体由数兆个细胞组成，这些细胞不停的经历细胞分 裂，且每次也产生自身DNA的复本。 (虽然我翻成"埋藏在基因构造的生理时钟"，不过应该是要buried in吧? 但我又不觉得它的意思是"和基因构造一起被埋藏的生理时钟"，不知道大家的看法如何? 还有"can only run for so long"中的only和so long加在一起不知道怎麽说，所以就不 翻only了...) This DNA is tightly packed into structures called chromosomes of which humans have twenty three pairs. The problem is, DNA replication isn't quite perfect and skips over the end of each chromosome. To protect against important DNA information being cut out, we have something called telomeres on the end of chromosomes which are essentially meaningless repeats of DNA that we can afford to lose. But every time our cells divide these telomeres become shorter and shoter until eventually they've been entirely stripped away. At which point the cell no longer divides. 这个DNA被紧密的包进叫做染色体的结构，而人类有23对染色体。问题是DNA的复制并不这 麽完美，它会略过每个染色体的尾端。为了保护重要的DNA资讯不被切断，我们在染色体的 尾端有叫做端粒的东西，本质上是我们足以舍弃的无意义DNA连续片段。但随着每次的分裂 这些端粒就愈来愈短，最後就完全的被除去。到了这个时候，细胞就不再分裂了。 Some flatworms are able to endlessly regenerate their telomeres making them effectively biologically immoral, but their lifespans do vary and they're still susceptible to disease further suggesting that aging is a mix of genetic and enviromental factors. 有些扁形动物可以无穷地产生自身的端粒，造成牠们实际上是几乎不死的，但牠们的寿命 不一且还是会受疾病的侵袭，暗示了老化是基因和环境要素的组合。 But why don't our cells do this? Ultimately this replication limit actually helps to prevent cancer which is the uncontrollable growth of cells and evasion of cell death. The point at which a cell stops replicating is known as cellular senescence. In humans this replication limit is around fifty times. Once it is reached the cell gradually begins to lose its function and die causing age-related characteristics. This also helps to explain why life expectancy is a strongly heritable trait from your parents, because you got your initial telomere length from them. 但为什麽我们的细胞不这麽做呢?最终这种复制上的限制实际会帮助预防那些不受控制的 细胞成长和不会衰老的细胞所造成的癌症。此时细胞停止复制即为所谓的细胞衰老。 在人类中这种限制大约为50次，之後细胞便逐渐丧失牠的功能接着死亡，产生年老相关的 特徵。这也帮助解释为什麽寿命和你的双亲有很大的继承特性，因为你的初始端粒长度是 从他们来的。 (除了我翻译提出的问题，如果有看到不妥的地方也麻烦纠正我，谢谢大家:D) --

※ 发信站: 批踢踢实业坊(ptt.cc) ◆ From: 36.229.85.58 ※ 编辑: Minilogo 来自: 36.229.86.21 (03/24 14:20)