万千英语族 英语爱好者的家园
在线英语广播
在线英语词典
在线杀毒查毒
77TEK
万千英语族 英语频道 首页 翻译文化 阅读写作 听力口语 学习方法 听歌学英语 趣味英语 好贴无限 数字生存
阅读字体:

VOA特别英语在线收听[附英文文本和简单注释] 20040121

www.iselong.com 作者:

HEALTH REPORT - Prion Diseases
By Nancy Steinbach

http://language.chinadaily.com.cn/dialogue/voa/special/2004/01/0121.rm

This is the VOA Special English Health Report.
In December, the United States reported its first case of mad cow disease. Agriculture officials have been working to make sure other cows that came from Canada with that animal are not used as food. This is because of the possibility that people who eat infected beef can get a human form of the disease. Officials say more than one-hundred-forty people in Britain have died since an outbreak of mad cow disease in the nineteen-eighties. Ten deaths have been reported in other countries.

The scientific name of the cattle disease is bovine spongiform encephalopathy. A similar disease in sheep is known as scrapie. Deer and elk suffer chronic wasting disease. And minks get a disease called transmissable mink encephalopathy.

In humans, there is a disease in babies called Alpers syndrome. Other similar diseases in people include fatal familial insomnia, kuru and Creutzfeld-Jacob disease. The human version of mad cow disease is a form, or variant, of Creutzfeld-Jacob.

All these diseases create holes in the brain. All kill. And experts say all are caused by infectious proteins. American scientist Stanley Prusiner discovered this kind of protein in the early nineteen-eighties. He named it a "prion" [PREE-on]. He won the Nobel Prize for Medicine. Prions contain no genetic material. So they cannot copy themselves the way bacteria, viruses and other infectious agents do.

Prions are found naturally in brain cells of people and animals. Research published last month in Cell magazine suggested that prions could help the brain store memories. But experts are not sure of their purpose.

Prions appear to do no harm until one changes shape. Normally a prion is round like a ball. The protein becomes dangerous when it unfolds into a straight line. When it touches another prion, the second one unfolds and touches another. That one also unfolds, and so on.

This process can start naturally. Or it can begin when an unfolded prion enters the brain of a person or animal that has eaten infected tissue. This is why farmers are now banned from feeding cows the remains of other cows and sheep.

Researchers are trying to discover more about prions. A big question is why only some people who ate infected beef have gotten sick.

This VOA Special English Health Report was written by Nancy Steinbach.



收藏至ViVi】【论坛】【英语词典】【英语广播】【打印】【评论】【关闭
相关专题:VOA 慢速英语
相关文章:
资料更新时间: 2004-2-18 18:34:28
资料标题:《VOA特别英语在线收听[附英文文本和简单注释] 20040121》
检索关键字:VOA,Special,English,美国之音,慢速英语,特别英语,文本,Script,在线收听,下载
资料编号:1719
资料来源:VOA
万千英语族或其成员转载此文档旨在传达更多资讯之目的,不代表万千英语族赞同或暗示其内容准确性,对于读者参照本文档操作可能造成的任何损失亦不承担任何责任.
Copyright©2000-2005    万千英语族    Not-All-Rights-Reserved.
 关于我们 友情链接 休闲英语社区 历史上的今天 英文儿歌 意见反馈 网站地图
Powered By 万千英语族CMS文章发布系统 [SQL Version]