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VOA慢速英语 2007 0515b

时间:2007-09-05 02:44:06

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VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Steve Ember.

VOICE TWO:

And I'm Barbara Klein. On our program this week, we will tell about a possible way to control the disease malaria1. Researchers have reported a decrease in the rate of male births in the United States and Japan for the past thirty years. We will tell about their findings. We also will tell about a study on the effects of vitamins in pregnant women.

(MUSIC)

VOICE ONE:

 
If malaria control efforts are to succeed, experts say mosquitoes in the wild must be replaced with parasite2-resistant3 ones
Researchers in the United States are exploring a possible way to control malaria. They are developing insects resistant to the disease.

More than three million people become infected with malaria each year. The disease kills at least one million people every year. Malaria is found in Africa, Asia, the Middle East and South America.

Malaria parasites4 enter a person’s blood through the bite of a very small insect -- the mosquito. The malaria parasites travel to the liver. The organisms grow and divide there. After a week or two, the parasites invade red blood cells and reproduce thousands of times. They cause a person’s body temperature to rise. They also may destroy major organs. People with malaria may suffer kidney failure or loss of red blood cells.

VOICE TWO:

People die from malaria because they are not treated or treatment is delayed. Different drugs can prevent the parasites from developing in the body. But experts still say the best way to prevent the disease is not to be bitten by a mosquito.

That could change in the future. Research scientists at The Johns Hopkins University have created mosquitoes that cannot spread the malaria parasite. Computer studies show that such insects are needed to replace mosquitoes in the wild if malaria control is to succeed. The researchers reported their findings in the Proceedings5 of the National Academy of Sciences.

Earlier studies showed that disease resistant mosquitoes might not be as healthy as wild ones. Those with resistance would die early and not be able to replace the others.

VOICE ONE:

The Johns Hopkins researchers put equal numbers of malaria resistant mosquitoes in a box with other mosquitoes. All the insects fed on mice that had been infected with the malaria parasite. The researchers took eggs made by the insects and kept them until they became adult mosquitoes. These new mosquitoes were then permitted to feed on infected mice. The researchers did this again and again. After nine generations, seventy percent of the mosquitoes were malaria resistant.

The researchers say they changed the genetic7 structure of the mosquitoes to produce a protein called S.M. One. The S.M. One gene6 blocks the development of the malaria parasite inside the insect. The genetically8 engineered mosquitoes mated with mosquitoes lacking this gene. So their young had a single copy of the gene -- not two. This is thought to be the reason the genetically engineered mosquitoes did not die early as the others.

Other researchers say the Johns Hopkins work confirms earlier studies concerning disease resistant insects. But they say more work needs to be done, especially with human malaria parasites. The researchers say creation of the new insects alone will probably not be able to control the disease. They say malaria resistant mosquitoes could be used in combination with drugs and insect poisons to stop malaria in the future.

(MUSIC)

VOICE TWO:

A new report says the number of boys born in the United States and Japan has decreased every year since nineteen seventy. The report says the reason for the decrease is unclear. But it says environmental and other influences might be involved.

American and Japanese researchers studied thirty years of birth records from the two nations. The researchers say they found fewer boys were born in comparison to girls. They say the decrease in births was equal to one hundred thirty-five thousand white males in the United States. In Japan, the decrease was equal to one hundred twenty-seven thousand fewer males.

VOICE ONE:

The study found a decrease of seventeen males for every ten thousand births in the United States since nineteen seventy. And it found an even greater decline in Japan -- thirty-seven males for every ten thousand births. It also found a continued rise in deaths of male fetuses10. The fetuses died before they were fully11 developed.

The researchers examined birth records of African-Americans as a separate group from white Americans. They found that the number of male births among African-Americans increased a little. But the rate of male births to female births for African-Americans was lower than that of whites.

The study found that all races experienced a decrease in the number of fetal deaths, probably because of improved medical care.

VOICE TWO:

Devra Lee Davis of the University of Pittsburgh Center Institute led the study. She says scientists do not know the reason for the decline in male births, but suspect environmental poisons.

Earlier reports show that researchers suspected a similar decrease in male births in other industrial nations.

Scientists already know that men who work with some chemicals and metals have fewer baby boys. Scientists also know that some things influence both a woman’s ability to have a child and the health of her children. These include her physical health, the foods she eats and the chemicals in the air around her.

VOICE ONE:

Professor Davis says other things can affect the health of a male fetus9. They include the weight and age of the parents, and their use of alcohol drinks and drugs.

The report says one in every four to five married adults today report difficulty having children. It says evidence shows that chemicals in the air can affect the health of male reproductive fluid. This increases the chances of men producing a physically12 disabled child.

Professor Davis says more research is needed to examine these questions in greater detail among small groups. Experts say such research could lead to environmental changes that will protect young people and their children in the future.

(MUSIC)

VOICE TWO:

The World Health Organization estimates twenty million babies are born too small each year. It says a baby weighing less than two thousand five hundred grams at birth has a less than desirable weight for good health. Ninety-five percent of such children are born in developing countries.

One recent study shows that pregnant women in developing countries have healthier babies if the women are given vitamins. Researchers from the United States and Tanzania found that vitamins could help reduce low birth weight. Their findings were reported last month in The New England Journal of Medicine.

Wafaie Fawzi of the Harvard University School of Public Health led the study. Professor Fawzi says low birth weight can cause serious health problems in babies. He says low birth weight has been linked to poor growth and mental development, and even early death.

VOICE ONE:

There are fourteen kinds of vitamins. People who do not get enough of these chemicals in their food, or want more, often take multivitamins.

In the study, multivitamin pills were given to four thousand two hundred pregnant Tanzanian women. The pills contained all the B vitamins, as well as vitamins C and E. They also included iron and folate in levels several times higher than advised for women in industrial nations.

Four thousand other women received a harmless substance. None of the women had the virus that causes the disease AIDS.

VOICE TWO:

The researchers found a twenty percent decrease in health risks for babies when mothers took the vitamins every day. There were no major differences between the two groups in the rate of early births or deaths of babies.

The researchers say the vitamins helped improve the growth of fetuses probably by improving the mother's natural defenses against disease and hemoglobin levels. Hemoglobin is the coloring in red blood cells that carries oxygen.

Professor Fawzi says multivitamin pills should be considered for all pregnant women in developing countries. He says the pills improve health and are not costly13.

(MUSIC)

VOICE ONE:

This SCIENCE IN THE NEWS was written by Nancy Steinbach and Lawan Davis. Brianna Blake was our producer. I'm Steve Ember.

VOICE ONE:

And I'm Barbara Klein. Listen again next week at this time for more news about science in Special English on the Voice of America.
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1 malaria B2xyb     
n.疟疾
参考例句:
  • He had frequent attacks of malaria.他常患疟疾。
  • Malaria is a kind of serious malady.疟疾是一种严重的疾病。
2 parasite U4lzN     
n.寄生虫;寄生菌;食客
参考例句:
  • The lazy man was a parasite on his family.那懒汉是家里的寄生虫。
  • I don't want to be a parasite.I must earn my own way in life.我不想做寄生虫,我要自己养活自己。
3 resistant 7Wvxh     
adj.(to)抵抗的,有抵抗力的
参考例句:
  • Many pests are resistant to the insecticide.许多害虫对这种杀虫剂有抵抗力。
  • They imposed their government by force on the resistant population.他们以武力把自己的统治强加在持反抗态度的人民头上。
4 parasites a8076647ef34cfbbf9d3cb418df78a08     
寄生物( parasite的名词复数 ); 靠他人为生的人; 诸虫
参考例句:
  • These symptoms may be referable to virus infection rather than parasites. 这些症状也许是由病毒感染引起的,而与寄生虫无关。
  • Kangaroos harbor a vast range of parasites. 袋鼠身上有各种各样的寄生虫。
5 proceedings Wk2zvX     
n.进程,过程,议程;诉讼(程序);公报
参考例句:
  • He was released on bail pending committal proceedings. 他交保获释正在候审。
  • to initiate legal proceedings against sb 对某人提起诉讼
6 gene WgKxx     
n.遗传因子,基因
参考例句:
  • A single gene may have many effects.单一基因可能具有很多种效应。
  • The targeting of gene therapy has been paid close attention.其中基因治疗的靶向性是值得密切关注的问题之一。
7 genetic PgIxp     
adj.遗传的,遗传学的
参考例句:
  • It's very difficult to treat genetic diseases.遗传性疾病治疗起来很困难。
  • Each daughter cell can receive a full complement of the genetic information.每个子细胞可以收到遗传信息的一个完全补偿物。
8 genetically Lgixo     
adv.遗传上
参考例句:
  • All the bees in the colony are genetically related. 同一群体的蜜蜂都有亲缘关系。
  • Genetically modified foods have already arrived on American dinner tables. 经基因改造加工过的食物已端上了美国人的餐桌。 来自英汉非文学 - 生命科学 - 基因与食物
9 fetus ekHx3     
n.胎,胎儿
参考例句:
  • In the fetus,blood cells are formed in different sites at different ages.胎儿的血细胞在不同时期生成在不同的部位。
  • No one knows why a fetus is not automatically rejected by the mother's immune system. 没有人知道为什么母亲的免疫系统不会自动排斥胎儿。
10 fetuses eae25b106f4ed68558631a5bf44c9293     
n.胎,胎儿( fetus的名词复数 )
参考例句:
  • DNA was extracted from fetuses at mid-gestation, about 10 days past conception. DNA从受孕大约10天后的中期妊娠胚胎中提取。 来自互联网
  • Brucellosis is a disease that causes fetuses to abort in cattle. 普鲁士菌病是一种可以导致牲畜胎儿夭折的疾病。 来自互联网
11 fully Gfuzd     
adv.完全地,全部地,彻底地;充分地
参考例句:
  • The doctor asked me to breathe in,then to breathe out fully.医生让我先吸气,然后全部呼出。
  • They soon became fully integrated into the local community.他们很快就完全融入了当地人的圈子。
12 physically iNix5     
adj.物质上,体格上,身体上,按自然规律
参考例句:
  • He was out of sorts physically,as well as disordered mentally.他浑身不舒服,心绪也很乱。
  • Every time I think about it I feel physically sick.一想起那件事我就感到极恶心。
13 costly 7zXxh     
adj.昂贵的,价值高的,豪华的
参考例句:
  • It must be very costly to keep up a house like this.维修这么一幢房子一定很昂贵。
  • This dictionary is very useful,only it is a bit costly.这本词典很有用,左不过贵了些。

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