英文原文

【背景介绍】

诸如严重的情绪悲伤、工作压力等会加速身体的老化？这绝非耸人听闻。美国加利福尼亚大学的ElissaEpel博士领导的这项研究在生物学领域第一次把心理紧张和心理压力与生理年龄如此直接地联系起来。而在上海内分泌领域的专家看来，美国科研小组上个星期轰动世界的这项研究成果非常适合用来解释中国人常说的“一夜白头”。

【英文原文】

Your teenage son wrecks the car. Your daughter shows up with her recently paroled boyfriend.

These are the sorts of things that can make your hair turn gray overnight.

Actually, it's impossible for hair to completely change color overnight. Hair color comes from a pigment called melanin. When hair grows, the cells that form the growing hair accumulate melanin and distribute it throughout the shaft at the center of a strand of hair. The hair's color depends on the number, size, and color of the melanin particles.

Gray hair results when, for some reason, the production of melanin is reduced, or stops completely. When this happens, the hair becomes transparent and all we see are the colorless cells that make up the hair shaft. Although it is common for melanin production to decrease and eventually stop as a person grows older, there is no specific explanation as to why this happens. Heredity seems to play a significant role in determining when the cells that make hair stop making pigment. If you have inherited genes programmed to shut off the production of melanin at an early age, you'll go gray sooner than later.

The phenomenon of suddenly going gray due to stress has more to do with hair loss than with actually losing color. A significant amount of stress can cause hair to fall out prematurely. If you already have a significant amount of gray hair, the remaining dark hairs might be in a non-growing, resting phase, and thus are more likely to fall out. The sudden loss of dark hair will make it seem as though you've gone gray overnight.

参考译文

【参考译文】

你的十几岁的儿子把你的车给毁了。你的女儿和她刚刚被释放出来的男朋友一起。
这些都是能够让你的头发一夜变白的事情。

事实上，头发一夜变白是不可能的。头发的颜色主要是来源于一种黑色素的天然色素。当头发生长的同时，黑色素会渗入到发梢根部等。头发的颜色主要取决于黑色素的数量，大小和颜色。

头发变白主要是由于提供颜色的黑色素突然下降或者直接停止了。当这种现象发生的时候，我们会发现头发变成透明色，这主要是由于组成头发的细胞没有颜色了。虽然，人类随着年龄的增加，黑色素的分解会慢慢减少，并最终停止，但是这种现象缺乏一个具体的解释。遗传因素在左右人类的黑色素工作的年龄上有很大的影响。如果你的家族中有少年白的基因，那么你的头发会白的比较早。

一夜变白的现象并不是因为压力导致头发颜色不见，而是由于头发变少引起的。巨大的压力会导致头发过早地脱落。如果你已经有一部分的百大，那么你剩下的黑发很有可能就会处在一个停止生长的状态，并很有可能脱落。黑头发的脱落会让你看上去出去一夜白头的现象。

相关报道

【相关报道】

1. If you have inherited genes programmed to shut off the production of melanin at an early age, you'll go gray sooner than later.
如果你的家族中有少年白的基因，那么你的头发会白的比较早。

inherit v. 继承，遗传

如：The will has to be proved before we can inherit.
遗嘱要先认证，然後我们才能继承遗产。

The oldest son will inherit the title.
长子将继承爵位。

2.A significant amount of stress can cause hair to fall out prematurely.
巨大的压力会导致头发过早地脱落。

fall out 解散，掉队，结果

如：After a long drill he told the squad to fall out.
操练了好半天之后，他让这个班解散了。

prematurely adv. 过早地，早熟地

如：Worry and illness had made him prematurely old.
他心事重重、 疾病缠身，落得个未老先衰。