英語聽力文摘565 什么是兒童早衰癥？

What Is Progeria?

Progeria was first described in the nineteenth century. The mysterious disease is often thought of as premature 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 arteries and high blood pressure. None lives past their early teens.

In 2003, researchers discovered what causes progeria: a genetic point mutation. That means that when genes are being copied to make egg or sperm, just one position in one DNA strand 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 gene that encodes lamin A, a protein in the cell’s nucleus, 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 remains 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, cholesterol 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.

　　什么是兒童早衰癥?

　　最早記載的兒童早衰癥發(fā)生在19世紀。人們通常認為這種神秘的疾病是過早衰老。

　　患有早衰癥的兒童一歲之前都非常正常，但之后他們會患上通常老年人才會罹患的疾病。

　　他們的骨骼變得脆弱，皮膚變得松弛，頭發(fā)脫落。他們會死于由動脈硬化以及高血壓引發(fā)的心臟病或中風。沒有患者能夠活過少年早期。

　　2003年，研究者發(fā)現(xiàn)了少年早衰癥的病因：基因點突變。這表示當基因復制形成卵細胞和精子時，DNA單鏈上的某處的復制出現(xiàn)錯誤。這就好像你照著食譜做煎餅，卻把鹽錯當發(fā)酵粉用。煎餅當然發(fā)不起來。

　　患有早衰癥的兒童體內編譯核纖層蛋白A(細胞核內的一種蛋白質)的基因出現(xiàn)了錯誤。當核纖層蛋白A被正常編譯時，人體內一種名叫法呢基的化學物質會從細胞 核內脫落。而在早衰細胞中，這種化學物質仍然附著在細胞核上。發(fā)生突變的蛋白質黏著、堆積在細胞核內，從而影響了細胞的功能。

　　對兒童早衰癥的研究已經(jīng)開始往兩個互補的方向發(fā)展。一些科學家通過對抗癌藥、降脂藥、健骨藥、免疫抑制藥的研究，努力尋找治療該疾病的方法。另一些科學家則對早衰癥與自然老化的相似性很感興趣。

　　科學家發(fā)現(xiàn)，在一些未患早衰癥的老年人的皮膚細胞中也出現(xiàn)了類似早衰癥的變化。在這些細胞內，一種叫做前層細胞A的蛋白質與發(fā)生突變的蛋白質相似，其數(shù)量以較慢的速度增加。這種蛋白可能會導致骨骼脆弱以及其他老化所帶來的問題。