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【medical-news】杀虫剂可导致早发性帕金森病的风

杀虫剂可导致早发性帕金森病的风险提高
From ScienceDaily 2006-9-15

长期暴露在低水平的杀虫剂中,将加速脑的变化并且有可能将导致帕金森症提前几年甚至几十年发生。这项发现,是由爱默里大学和佐治亚理工的研究者在美国化学学会国会上提出。

这项关于将加速疾病发病进程的发现,让长期就被怀疑的杀虫剂问题和帕金森病更紧地纠缠在了一起。“我们的发现清楚地显示,如狄氏剂这类杀虫剂,将恶化已经潜藏的疾病”,Gary Miller教授说,“杀虫剂不是发病所必须的,但是它确实促进了帕金森病的发病过程。所以你暴露在杀虫剂中越多,你就可能越早发病。

在他们的早期研究中,Miller教授和他的合作者发现,在14位帕金森患者脑中,狄氏剂(一种DDT的替代品,1940年发展起来的一种杀虫剂)的含量是正常人的3倍。

基于这个发现,研究者大致估计了这些病人整个一生暴露在杀虫剂中的水平,并且由此推断相信老鼠应受到的暴露量。他们把实验小鼠暴露在低水平,但是和环境相适应的狄氏剂剂量中。一个月后,虽然没有一只小鼠表现出帕金森的症状,但是它们脑内的氧化压力明显增加,而且多巴胺水平明显下降。而多巴胺是帕金森发病过程中非常重要的神经递质。

早在这之前,哈佛公共卫生学院就有大量成人的研究报告表明长期低水平暴露在杀虫剂中将使帕金森发病率提高70%。另外一项报告也指出胎儿时期的啮齿类动物暴露在狄氏剂中,将导致脑的变化,使它们对致帕金森的毒性物质更敏感。

Miller教授说:“我们相信,一个本应在80岁得帕金森的人,会因暴露在杀虫剂中,而在65或70岁时就得了帕金森。”

狄氏剂在1987年被完全禁止,但因为生物链的富集作用,它仍然存在于我们的环境中,即使在几十年以后。并且沿着食物链传递,特别是乳制品和肉,然后传给人类。

然而,在接下来的几十年里,狄氏剂和其它一些被禁用的杀虫剂将浓度逐渐降低以至完全驱散,从而变成帕金森发病过程中一个影响更小的一个因素。

原文链接:http://www.sciencedaily.com/releases/2006/09/060914194700.htm

原文:
Low-level exposure to a banned but lingering pesticide appears to accelerate changes in the brain that can potentially lead to the onset of Parkinson's disease symptoms years or even decades before they might naturally develop. This finding, by researchers at Emory University and the Georgia Institute of Technology in Atlanta, was presented today at the 232nd national meeting of the American Chemical Society, the world's largest scientific society.

The concept of an accelerated disease process is a new twist in the investigation of the long-suspected link between the use of pesticides and Parkinson's disease, according to the researchers.

"Our current study clearly shows that pesticides such as dieldrin appear to accelerate or exacerbate the already underlying disease," said Gary Miller, Ph.D., an associate professor of environmental and occupational health at Emory University. "Pesticides aren't necessarily the causative agents, but they do promote Parkinson's. So it appears the more you are exposed to pesticides, the greater your risk of developing the disease earlier in life."

In their pilot study, Miller and his co-researchers -- Emory graduate student Jaime Hatcher and Georgia Tech Professor Kurt Pennell, Ph.D. -- found that levels of dieldrin, an organochlorine pesticide developed in the 1940s as an alternative to DDT, were three times higher in the brains of 14 people who had Parkinson's disease than in the brains of 12 people who didn't.

Based on this finding, the researchers estimated the lifetime exposure levels of these people and extrapolated these levels to mice. They then exposed laboratory mice to low, but "environmentally relevant" dosages of dieldrin - about 1 to 3 milligrams per kilogram. After one month, although none of the mice showed symptoms of Parkinson's disease, the researchers did detect increased levels of oxidative stress in the brain and significantly reduced uptake of dopamine, the neurotransmitter that plays a key role in the development of Parkinson's.

This latest work adds more evidence establishing a link between pesticides and Parkinson's. Earlier this year, a Harvard School of Public Health study of more than 140,000 adults found that those exposed to long-term, low levels of pesticides had a 70 percent higher incidence of Parkinson's disease. Another recent study, by the same Emory/Georgia Tech team, found that fetal rodents exposed to dieldrin had brain alterations that made them more susceptible to Parkinson's-inducing toxins.

"All of the evidence that has been accumulating suggests that exposure to pesticides increases the risk of Parkinson's disease," Miller said. "We believe that a person who is destined to get Parkinson's because of genetics or other factors at age 80 might develop symptoms when they're 65 or 70 if they have been exposed to pesticides."

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作者:admin@医学,生命科学    2011-09-02 05:12
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