|
74 疯牛病及其最新的检验方法
DATE=7-24-01
TITLE=SCIENCE IN THE NEWS #2134 - Mad Cow Disease
BYLINE=Nancy Steinbach, George Grow
VOICE ONE:
This is Sarah Long.
VOICE TWO:
And this is Steve Ember with SCIENCE IN THE NEWS, a VOA Special English program about recent developments in science.
Today, we tell about a disease in cows that can spread to other animals and to people. We also tell about recent scientific progress in developing a test for the disease.
(THEME)
VOICE ONE:
The cattle disease is (1)bovine spongiforn encephalopathy. It causes holes to develop in the brain. Cattle act strangely before they die. So it is known as Mad Cow Disease.
B-S-E first (2)appeared in Britain in Nineteen-Eighty-Five, and has spread across much of Europe. All animals known to have the disease since that time have been found in Europe or (3)imports from Europe.
Scientists believe that eating (4)infected beef from a cow suffering B-S-E causes a (5)similar disease in people. This deadly disease is called Creutzfeldt-Jakob Disease, or C-J-D. It cannot be cured. C-J-D is (6)rare. It usually (7)affects people sixty-five years old or older. More than one-hundred people in Europe have died or are dying from it. Most of the (8)victims live in Britain.
VOICE TWO:
Animal health experts recently met in Paris, France, to (9)discuss mad cow disease.
They said more than thirty countries have (10)banned the import of meat, bone meal and live cattle from western Europe. They said countries can be considered at (11)risk for B-S-E if they imported such products from Western Europe during the past twenty years. They said parts of Eastern Europe, Asia and the Middle East are at increased risk.
The officials also (12)urged countries to (13)approve (14)measures to control the killing of animals for food. They say this would reduce the chance of infected meat being sold as food for people. They also said the human food supply should not include the animal parts thought most likely to carry the disease, such as the head and the (15)spinal cord.
The European Union now (16)requires that all animals over thirty months old be tested for mad cow disease when they are killed. The idea is that older animals are likely to have more (17)severe infections that are the greatest danger to people.
VOICE ONE:
American officials have taken steps to (18)prevent Mad Cow Disease from entering the United States. The government (19)restricts imports of cows and other animals from countries where B-S-E exists. Imports of some feed products from such areas also are restricted. Feed (20)containing animal remains is (21)suspected of causing the disease. American officials say more than two-hundred-fifty experts know how to recognize foreign animal diseases, (22)including B-S-E. (23)Information about the disease has been (24)provided to (25)federal and state (26)agencies, laboratories and some colleges.
American officials say they are inspecting animals for signs of B-S-E. Federal (27)inspectors are examining all cows raised for meat. They examine the animals for (28)disorders of the central nervous system. Any animal showing signs of such a disorder is destroyed. The meat is not (29)permitted for use as human food. The brains of these animals are sent to the Agriculture Department for (30)additional tests.
(MUSIC BRIDGE)
VOICE TWO:
The only sure way to tell if an animal has B-S-E is to test a brain sample after it has been killed. Now, (31)Israeli scientists say they have discovered the (32)substance (33)responsible for mad cow disease in the (34)liquid waste of animals and people.
Scientists believe B-S-E is caused by a kind of infectious (35)particle known as a prion (PREE-on). Prions are (36)proteins. They do not contain any (37)genetic material so they cannot make copies of themselves. This makes them different from all other known infectious agents such as (38)bacteria, (39)viruses, fungi and (40)parasites.
Prions are found naturally in brain cells of people and animals. They do no harm. Sometimes, however, one changes shape. Other proteins known as (41)enzymes can destroy normal proteins. But they cannot destroy changed prions.
VOICE ONE:
A few years ago, scientist Stanley Prusiner showed how these changed prions act on (42)surrounding normal prions to change them too. More and more prions change, until the changed ones are spread throughout the brain. This kills brain (43)tissue and causes human (44)spongiform brain diseases, including Creutzfeldt-Jakob disease.
Doctor Prusiner also showed that prion disease could move from one kind of animal to another. For example, he showed that people could develop C-J-D by eating meat from cows infected with B-S-E. Doctor Prusiner won the Nobel Prize for Medicine in Nineteen-Ninety-Seven for his work.
VOICE TWO:
Ruth Gabizon was one of the researchers who worked with Doctor Prusiner. She continued her own research on human spongiform brain disease at the Hadassah University Hospital in (45)Jerusalem, Israel. She was studying the part prions play in causing genetic Creutzfeldt-Jakob disease. This kind of C-J-D affects Jews whose families were from (46)Libya.
The researchers on her team were looking for (47)evidence of changed prions in liquid waste or (48)urine. They studied the urine of small laboratory animals called (49)hamsters, cattle and people. They tested the urine from animals and people infected with known prion diseases and from those who were healthy.
The (50)kidneys (51)contain (52)urea, a substance that (53)interferes with protein changing but does not destroy the proteins. The researchers suspected the prions might be changed by urea.
VOICE ONE:
To test this idea, they put the urine samples from the animals and people into a machine that (54)removes urea. This permitted the proteins to go back to their normal shapes. These proteins were then (55)treated with enzymes that destroy normal proteins but not prions.
All the proteins were destroyed in the urine from healthy animals and people. But one protein (56)survived in animals and people with prion diseases. The researchers said the (57)presence of such a protein in urine is the way to tell if prion disease is present. The Israeli scientists also infected some hamsters with prion disease. Tests of their urine showed the changed protein several weeks before signs of the disease first appeared. VOICE TWO:
A report of the Israeli research group's experiments will be (58)published in the Journal of Biological Chemistry in September. However, the (59)publication has already placed the research on its Internet web site.
Scientists who have seen the research say the experiment was simple and the results should easily be (60)confirmed. Many laboratories all over the world are reportedly already trying to do this. If the results are confirmed, the new test could be used on groups of cattle. It could save uninfected cattle that are now killed after an infected animal is found.
(MUSIC BRIDGE)
VOICE ONE:
The Israeli scientists say their test will be able to tell which people and animals are infected with spongiform disease before signs appear.
Other scientists say this could help make the blood supply safer around the world. It has not yet been proved that people with C-J-D can spread the disease by giving blood to other people. Yet officials are worried about that (61)possibility. The American Red Cross will not accept blood from people who have lived in Britain for three months or in Europe for six months during the last twenty years.
The (62)proposed test may also help answer questions about sick deer and other wild animals in the western United States and Canada. The animals are (63)suffering a brain condition known as (64)chronic wasting disease. The disease has spread among wild deer and (65)elk. Researchers do not know how it is spread. But they say the new test could help discover the answer.
VOICE TWO:
The Israeli scientists recognize that they are attempting to create a test for a disease that cannot be cured. In people, the (66)period of time between infection and the first signs of the Creutzfeldt-Jakob disease may be as long as twenty or thirty years. Would people want to know if they are infected with the disease so many years before they would become sick? That is a question people may have to answer in the future. For now, scientists say the new test may help them learn more about the prions responsible for spongiform disease before and after a person or animal becomes sick.
(THEME)
VOICE ONE:
This SCIENCE IN THE NEWS program was written by George Grow and Nancy Steinbach. It was produced by Caty Weaver with audio assistance by twine carlens . This is Sarah Long.
VOICE TWO: And this is Steve Ember. Join us again next week for more news about science in Special English on the Voice of America.
(1)bovine [ 5bEuvain ] spongiforn encephalopathy [en9sefE`lCpEWI] n.牛海绵状脑病
(2)appear [ E5piE ]vi.出现
(3)import [ im5pC:t ]vt.进口
(4)infect [ in5fekt ]vt.[医]感染
(5)similar [ 5similE ]adj.相似的, 类似的
(6)rare [ rZE ]adj.罕见的
(7)affect [ E5fekt ]vt.影响
(8)victim [ 5viktim ]n.牺牲品
(9)discuss [ dis5kQs ]vt.讨论, 论述
(10)ban [ bB:n ] vt.禁止
(11)risk [ risk ] n.风险
(12)urge [ E:dV ]vt.催促
(13)approve [ E5pru:v ]vt.批准, 通过
(14)measure [ 5meVE ]n.标准
(15)spinal [ 5spainl ]adj.脊骨的, 脊髓的
(16)require [ ri5kwaiE ]vt.需要, 要求, 命令
(17)severe [ si5viE ]adj.严重的, 严峻的
(18)prevent [ pri5vent ]v.预防
(19)restrict [ ris5trikt ]vt.限制
(20)contain [ kEn5tein ]vt.包含
(21)suspect [ sEs5pekt ] v.怀疑
(22)include [ in5 klu:d ]vt.包括, 包含
(23)information [ 7infE5meiFEn ]n.信息
(24)provide [ prE5vaid ]v.供应, 供给
(25)federal [ 5fedErEl ]adj.联邦的
(26)agency [ 5eidVEnsi ]n.代理处
(27)inspector [ in5spektE ]n.检查员, 巡视员
(28)disorder [ dis5C:dE ]n.杂乱, 混乱, 无秩序状态
(29)permit [ pE(:)5mit ]v.许可, 允许, 准许
(30)additional [ E5diFEnl ]adj.另外的, 附加的, 额外的
(31)Israeli [ iz5reili ]adj.以色列共和国的n.以色列共和国民
(32)substance [ 5sQbstEns ]n.物质, 实质
(33)responsible [ ris5pCnsEbl ]adj.有责任的,负责的
(34)liquid [ 5likwid ]n.液体
(35)particle [ 5pB:tikl ]n.微粒
(36)protein [ 5prEuti:n ]n.[生化]蛋白质
(37)genetic [ dVi5netik ]adj.遗传的, 起源的
(38)bacteria [ bAk5tiEriE ]n.细菌
(39)virus [ 5vaiErEs ]n.[微]病毒
(40)parasite [ 5pArEsait ]n.寄生虫
(41)enzyme [5enzaIm]n.[生化]酶
(42)surrounding [ sE5raundiN ] adj.周围的
(43)tissue [ 5tisju: ]n. [生]组织
(44)spongiform [ 5spQNdVifC:m ]adj.海绵状(组织)的
(45)Jerusalem [ dVe5ru:sElEm ]n.耶路撒冷(巴勒斯坦著名古城)
(46)Libya [ 5libiE ]n.利比亚（北非国家）
(47)evidence [ 5evidEns ]n. [物]证据
(48)urine [ 5juErin ]n.尿
(49)hamster [5hAmstE(r)] n.东欧或亚洲产的大颊的鼠类
(50)kidneys [ 5kidniz ]肾形矿脉
(51)contain [ kEn5tein ]vt.包含
(52)urea [ 5juEriE ]n.[化]尿素
(53)interfere [ 7intE5fiE ]vi.干涉
(54)remove [ ri5mu:v ]vt.移开
(55)treat [ tri:t ] vt.对待
(56)survive [ sE5vaiv ]v.幸存
(57)presence [ 5prezns ]n.存在
(58)publish [ 5pQbliF ]v.出版, 刊印
(59)publication [ 7pQbli5keiFEn ]n.出版物
(60)confirm [ kEn5fE:m ]vt.确定
(61)possibility [ 7pCsi5biliti ]n.可能性
(62)propose [ prE5pEuz ]vt.建议
(63)suffer [ 5sQfE ]vt.遭受, 经历
(64)chronic [ 5krCnik ]adj.慢性的
(65)elk [ elk ]n.[动]麋鹿
(66)period [ 5piEriEd ]n.时期adj.过去某段时期的
|