英语听力文摘 English Digest 565、什么是儿童早衰症？

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　　Progeria was first described in the nineteenth century. The mysterious disease is often thought of as premature¹ aging.

 

　　Children with progeria are normal for their first year of life, but then develop medical problems normally seen in the elderly.

 

　　Their bones weaken. Their skin wrinkles. They lose their hair. They die from heart attacks or strokes brought on by hardened arteries² and high blood pressure. None lives past their early teens.

 

　　In 2003, researchers discovered what causes progeria: a genetic⁴ point mutation⁵. That means that when genes⁶ are being copied to make egg or sperm⁷, just one position in one DNA⁸ strand⁹ is copied wrong. It is like copying a pancake recipe and replacing baking powder with salt. The pancake is not going to rise.

 

　　For children with progeria, the gene³ that encodes lamin A, a protein in the cell’s nucleus¹⁰, is faulty. When the lamin A protein is normally made, a chemical piece called farnesyl is lopped off. In the progeria cell, the farnesyl stays attached. The mutant protein remains¹¹ sticky and piles up in the nucleus, altering the cell’s function.

 

　　Progeria research is moving in two complementary directions. Some scientists are working to find treatments for the disease with anti cancer, cholesterol¹² lowering, bone strengthening, and immune suppressing drugs. Others are interested in progeria’s similarity to aging.

 

　　Progeria like changes have been found in unaffected older people’s skin cells. A protein called prelamin A, which is similar to the mutant protein, increases at low levels and may contribute to hardening of the arteries and other problems that come with aging.

 

　　Though progeria is extremely rare, it may in fact hold the key to aging in all individuals.

 

　　什么是儿童早衰症？

 

　　最早记载的儿童早衰症发生在19世纪。人们通常认为这种神秘的疾病是过早衰老。

 

　　患有早衰症的儿童一岁之前都非常正常，但之后他们会患上通常老年人才会罹患的疾病。

 

　　他们的骨骼变得脆弱，皮肤变得松弛，头发脱落。他们会死于由动脉硬化以及高血压引发的心脏病或中风。没有患者能够活过少年早期。

 

　　2003年，研究者发现了少年早衰症的病因：基因点突变。这表示当基因复制形成卵细胞和精子时，DNA单链上的某处的复制出现错误。这就好像你照着食谱做煎饼，却把盐错当发酵粉用。煎饼当然发不起来。

 

　　患有早衰症的儿童体内编译核纤层蛋白A（细胞核内的一种蛋白质）的基因出现了错误。当核纤层蛋白A被正常编译时，人体内一种名叫法呢基的化学物质会从细胞 核内脱落。而在早衰细胞中，这种化学物质仍然附着在细胞核上。发生突变的蛋白质黏着、堆积在细胞核内，从而影响了细胞的功能。

 

　　对儿童早衰症的研究已经开始往两个互补的方向发展。一些科学家通过对抗癌药、降脂药、健骨药、免疫抑制药的研究，努力寻找治疗该疾病的方法。另一些科学家则对早衰症与自然老化的相似性很感兴趣。

 

　　科学家发现，在一些未患早衰症的老年人的皮肤细胞中也出现了类似早衰症的变化。在这些细胞内，一种叫做前层细胞A的蛋白质与发生突变的蛋白质相似，其数量以较慢的速度增加。这种蛋白可能会导致骨骼脆弱以及其他老化所带来的问题。

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