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  科技压力和老化一个态度问题

  科学家发现了长期压力与一个衰老标志间的联系

  端粒(染色体终端)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。

  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。

  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(这个分裂数目称之为海弗利克界限,因海弗利克的发现而得名),

  染色体的缩短达到极限,细胞分裂活动也从此终止。

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  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。

  不利之处则是,细胞到达复制次数的极限是老化的标志之一。

  人们不想让这个过程发生的太快,尤其对于那些需要不断分裂才能够得以正常运作的组织而言,例如免疫系统组织。

  人们已经得知,长期的压力(例如,照料一个疾病迁延不愈的儿童)可以使端粒的缩短提前发生。

  然而人们对于该过程是否单向进行(即压力时期对端粒的改变作用不可逆转)尚不明确。

  然而,本周在美国癌症研究学会于佛罗里达州奥兰多召开的会议上,加州大学尔文分校由爱德华?尼尔森领导的研究团队发现,这一过程是可逆的。

  他们指出,抗压力训练不仅可以组织端粒缩短,也可以促进其修复。

  尼尔森博士通过对接受宫颈癌治疗的妇女电话咨询影响作用的研究,得出了这一可喜的结论。

  他们之前的研究发现,咨询在心理和生理上都产生了作用。

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  接受咨询的妇女报告其生活质量得到提高(与未接受咨询的对照组相比)。

  她们还显示出免疫系统功能的增强。

  由于咨询的上述益处,尼尔森博士想知道该研究是否能有更多的发现。他重新检查了被试的血液样本,试图获得白细胞端粒长度的信息(红细胞没有细胞核,因此没有染色体)。

  研究发现令他十分惊讶:咨询不仅阻止了端粒的缩短,同时促进了端粒的生长。

  那些报告咨询产生效果的妇女(例如,报告情绪压力降低)其咨询后的端粒长度大于咨询前。

  她们的海弗利克倒计时得到了重新的设置。

  当然,我们应该谨慎看待单个研究的结论。

  但该会议上另一个来自加州大学旧金山分校伊丽莎白?布莱克本(她由于发现了端粒的修复酶而与其他研究者共同获得诺贝尔奖)的报告也给出了一些支持证据。

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  她们发现锻炼和咨询对压力个体的端粒有相似的作用。

  如果尼尔森博士的研究得到成功的重复,将会为理解神秘复杂的身心健康关系点燃新的希望。

  就像他所指出的那样,这些妇女的生活没有任何变化。

  尽管接受治疗,她们仍身患癌症,并处于压力之中。唯一改变的,就是她们的态度。

  Science and Technology Stress and ageing A question of attitude

  The link between chronic stress and a marker of old age is being disentangled

  TELOMERES are to chromosomes what plastic caps are to shoelaces—they stop them fraying at the ends.

  Unlike shoelaces, though, chromosomes replicate themselves from time to time as the cells they are in divide.

  This shortens the telomere and, after 50-70 such divisions (a number known as the Hayflick limit, after its discoverer),

  a chromosome can grow no shorter and the cell it is in can divide no more.

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  That provides a backstop against cancer. The rapidly dividing cells in a tumour soon hit the Hayflick limit and the process is brought to a screeching halt.

  Which is a good thing. The bad thing is that reaching the limit is one of the markers of old age.

  You do not want it to happen too quickly, particularly in tissues that have to do a lot of dividing in order to work properly, such as those in the immune system.

  It has been known for some time that chronic stress (caring for a child with a protracted illness, for example) causes premature shortening of the telomeres.

  What has not been clear is whether this is a one-way trip, with each stressful period turning the telomeric ratchet irreversibly.

  This week, though, at a meeting of the American Association for Cancer Research in Orlando, Florida, a group of researchers led by Edward Nelson of the University of California, Irvine, showed that it isn't.

  Their research suggests that stress management not only stops telomeres from shortening, it actually promotes their repair.

  Dr Nelson drew this welcome conclusion from a previous study that measured the impact of telephone counselling on women who had been treated for cervical cancer.

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  The study found that such counselling worked, both mentally and physically.

  Women who had been counselled reported that the quality of their lives had improved, compared with those of a control group who had not been counselled.

  They also showed improvements in the strength of their immune systems.

  Given those benefits, Dr Nelson wondered if he could find others, and he re-examined the participants' samples to look at the lengths of the telomeres in their white blood cells (red cells have no nuclei, and therefore no chromosomes).

  What he found surprised him. Not only did counselling stop telomere shrinkage, it actually promoted telomere growth.

  Those women for whom counselling had worked (ie, those who reported a decrease in emotional stress) had longer telomeres at the end than they did at the beginning.

  Their Hayflick countdowns were being reset.

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  A single such result must, of course, be treated with caution.

  But another study reported at the meeting, by Elizabeth Blackburn of the University of California, San Francisco (who shared the Nobel prize for the discovery of the enzyme that repairs telomeres), gave some support.

  This showed that exercise has a similar effect to counselling on the telomeres of the stressed.

  If Dr Nelson's work is successfully replicated, it will shine more light on the ill-understood relationship between the health of the mind and the health of the body.

  For, as he points out, nothing actually changed in the lives of the women in question.

  They still had cancer, albeit under treatment, and they were still under stress. Nothing, that is, except their attitude.

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