Nature ConferenceNews：美国高科技协会年会，2004年2月，西雅图

铅能致精神分裂症

Helen Pearson

美国科学家最近发现胎儿在子宫内时如果接触铅的话，那其成年后患精神分裂症的几率将升高。

科学家知道诸如铅和酒精这样的毒素会对母亲体内的胎儿造成伤害，并使造成儿童期一系列的发育问题。但最新的研究发现这种损害即使在出生后数十年内同样也会发生。精神分裂症是一种常见于一二十岁年轻人的疾病。

纽约哥伦比亚大学的Ezra Susser和他的同伴们对储藏的1959-1966年间加利福尼亚州产妇的血样进行了检测。他们将其中44位发展为精神分裂症孩子的母亲血样与75例正常孩子母亲血样中的铅含量进行了比较。

母亲中血铅含量超过150mg/L时，孩子发生精神分裂症的几率是低于这一水平的两倍。Susser将这一研究结果在美国高科技协会年会上进行了汇报，并在网上公布了他们的研究论文。

如果这一结果在其他的研究组中也能被证实，那么可能多达四分之一的精神分裂症患者是由铅所引起的，在上世纪56十年代加利福尼亚州由于广泛的使用含铅汽油从而造成铅暴露相当高，Susser说。

现今使用的汽油绝大多数是不含铅的，但是冶炼工业和油漆仍然会向环境中排放铅。在发展中国家中铅可能还会造成很多人患精神分裂症。“我们认为这是一项很重要的发现，”Ezar说。

脑细胞的自杀

Susser认为铅可能会杀死正在生长中的胎儿神经细胞。医生们知道胎儿如果接触这种毒物的话会导致幼儿智力发育迟缓以及其他的大脑发育缺陷，但是对于钱是如何引起这种损伤的机制他们不是很清楚。

在过去对动物进行的多年研究证实抑制脑细胞活动的药物——如酒精，某些麻醉药以及抗癫痫药物，会促进神经细胞自杀。通常认为脑细胞在妊娠中期到出生后的两三年间非常脆弱。

密苏里州圣路易斯华盛顿大学医学院的John Olney称，单单使用酒精或者麻醉药都能够使这一期间的神经细胞发生脱髓鞘。

Olney已经发现将血中酒精浓度维持在喝两杯鸡尾酒后相当浓度半个小时以上会使正在生长的胎鼠脑细胞的死亡升高两到四倍。目前尚不知道酒精对人是否有相似的作用。

Ezra说他希望研究胎儿暴露于酒精或者其他药物后会不会引起其成年后精神分裂症或者其他精神类疾病的发生。他说他已经有初步的证据证明怀孕期间得流感会使得胎儿成年后精神分裂症的发病几率升高。

原文：http://www.nature.com /nature-events/conference-news/aaas2004/040216-9.html

Nature ConferenceNews：American Association for the Advancement of Science, Seattle, February, 2004.
17 February 2004 

Lead linked to schizophrenia

Helen Pearson
Babies exposed to lead in the womb may be at increased risk of developing schizophrenia as adults, US researchers have revealed.

Scientists know that toxins such as lead and alcohol can harm a mother's unborn child and trigger developmental problems during childhood. But the new study is one of the first to show that this damage can precipitate disorders that strike decades later. Schizophrenia is usually diagnosed in the late teens or early twenties.

Ezra Susser of Columbia University, New York and his team tested stored blood samples collected from expectant California mothers between 1959 and 1966. They compared the blood lead levels of 44 women whose children went on to develop schizophrenia with 75 others whose children did not.

Offspring of mothers whose blood topped 150 micrograms of lead per litre were twice as likely to develop schizophrenia as those whose blood levels were below this threshold, Susser revealed at the American Association for the Advancement of Science meeting in Seattle, and in an online paper.

If the finding holds up in other groups, as many as a quarter of all schizophrenia cases in this same age group might be explained by lead, Susser suggests. In the 1950s and 60s, lead exposure in California was relatively high because of the use of leaded gasoline, he says.

Most petrol is unleaded today. But lead still leaches into the environment from industrial smelters and paint, and Ezra says it might still account for a significant chunk of schizophrenia cases in developing countries. "We think it's a very important finding," he says.

Suicidal brain cells 

Susser suspects that lead may kill nerve cells in a fetus's growing brain. Doctors know that prenatal exposure to the toxin can cause childhood mental retardation and other brain deficits, but they are unsure exactly how lead causes injury.

In the past few years, animal research has shown that drugs that dampen brain-cell activity - such as alcohol, certain anaesthetics and anti-epileptic drugs - prompt cells to commit suicide. Brain cells are thought to be particularly vulnerable from mid-pregnancy through the first two or three years of a baby's life.

Even a single dose of alcohol or some anaesthetics can wipe out a swathe of nerve cells in this way, says John Olney of Washington University School of Medicine in St Louis, Missouri.

Olney has found that a blood alcohol level equivalent to that after a couple of cocktails, maintained for just half an hour or more, can double or quadruple the number of brain cells dying off in a mouse's growing fetus. It is not yet known if alcohol has the same effect in humans. 

Ezra says he now hopes to examine whether fetuses exposed to alcohol or other drugs are also at increased risk of schizophrenia or other psychiatric disorders as adults. He also has preliminary evidence that an influenza infection during the first half of pregnancy boosts the risk of schizophrenia in adults, he says.

转自  newhkong2000