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Stress and ageing A question of attitude 压力和老化 一个态度问题 The link between chronic stress and a marker of old age is being disentangled 科学家发现了长期压力与一个衰老标志间的联系 TELOMERES are to chromosomes what plastic caps are to shoelacesthey stop them frayingat the ends. 端粒之于染色体，如同塑料帽之于鞋带它们阻止了其末端的磨损。 Unlike shoelaces, though, chromosomes replicate themselves from time to time as the cellsthey are in divide. 和鞋带不同的是，随着它们所在细胞的分裂，染色体可以不断进行复制。 This shortens the telomere and, after 50-70 such divisions , 这种复制过程使端粒不断缩短，并且，在经过50到70次的细胞分裂后， a chromosome can grow no shorter and the cell it is in can divide no more. 染色体的缩短达到极限，细胞分裂活动也从此终止。 That provides a backstop against cancer. The rapidly dividing cells in a tumour soon hit theHayflick limit and the process is brought to a screeching halt. 这一机制有助于对抗癌症。快速分裂的细胞不久就会到达其海弗利克界限，使得该过程能够急刹车。这是个好现象。 | 
