SCIENCE IN THE NEWS

（单词翻译）

SCIENCE IN THE NEWS
By Jerilyn Watson and Brian Kim

Broadcast: Tuesday, December 14, 2004

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VOICE ONE:

This is SCIENCE IN THE NEWS, in VOA Special English. I'm Sarah Long.

VOICE TWO:

 
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And I'm Bob Doughty¹. On our program this week: we look at a dispute over a proposed nuclear energy project and how too much of something considered good for you may increase your risk of dying early.

VOICE ONE:

But first, a blood treatment offers hope to adults fighting the disease leukemia.

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Two new studies show that tissue connecting an unborn child to its mother may help some adults with leukemia. At birth, blood from the umbilical cord of a baby contains stem cells. Research scientists say such cells can rebuild the natural defense² system of an adult with the blood disorder³.

The defense system protects the body against disease. However, some treatments for leukemia can destroy this system. The researchers say their studies show that cord blood can restore the natural defenses. They say cord blood can be used when a more proven method of treatment is not possible.

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Umbilical cord stem cells are already used for children fighting leukemia. Until now, many researchers believed that cord blood could only help children or small adults. The two studies suggest that is no longer a problem.

Cord blood is not as rich in stem cells as bone marrow⁴. Bone marrow is the connective tissue that fills bones. Marrow produces much of a person's blood supply. Bone marrow currently is the substance most used to restore a person's natural defenses against disease.

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For years, many doctors have chosen to replace destroyed adult bone marrow with healthy marrow. This process is called a bone marrow transplant. It can happen only under limited conditions. The patient's body must accept bone marrow from another person. The person providing healthy marrow is called the donor⁵. For the transplant process to be successful, the patient and the donor usually must have similar tissues.

But it is difficult to find a donor whose marrow the patient can use. Each year, doctors say most leukemia patients with a destroyed natural defense system die before the right donor can be found.

Stem cells are unformed. They exist in the blood and within tissues that make blood. They grow inside a patient. They direct the production of all kinds of blood cells. That is how stem cells can rebuild a person's natural defense system.

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The New England Journal of Medicine published both new studies about cord blood stem cells. One study was performed in Europe. The other was in the United States. Both involved hundreds of patients.

Most patients in the studies were very sick. Many died over two or three years. But the European study showed that cord blood worked equally effectively as the best kind of marrow transplants. Both had a survival rate of about thirty-three percent. In the American study, the percentage of survivors⁶ helped by cord blood was almost as hopeful.

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Mary Laughlin of the Case Western Reserve University School of Medicine led the American study. She says all the survivors would have died without treatment. Cancer experts not involved in the either study expressed hope over the results. They noted⁷ the difficulty of leukemia patients in finding a donor similar enough for a bone marrow transplant to be successful.

One blood expert, Pablo Rubenstein, noted another reason to consider cord blood treatment. He said stem cells in cord blood are less likely than adult bone marrow to cause a sickness called grant-versus-host disease. It strikes when the stem cells of the donor attack the patient's tissues and organs.

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The Institute of Medicine is a federal agency in Washington, D.C. It says patients may be able to find useful cord blood more easily than donor marrow. The Institute is studying ways to establish a national center for the supply of cord blood.

About four million babies are born in the United States each year. After each birth, medical workers block off and cut the umbilical cord. Most cords are thrown away. Taking blood from them is safe and painless for mother and child.

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VOICE ONE:

The European Union says it is set to move forward with plans for a nuclear fusion⁸ reactor⁹. E.U. officials agreed last month to continue seeking Japanese support to build the reactor in France. They also said the European Union is prepared to build it without Japan if negotiations¹⁰ fail. Later, Japanese officials criticized the European Union for talking about acting¹¹ on its own. They urged the Europeans to continue talks with other countries involved in the project. The others are Japan, China, Russia, South Korea and the United States.

The project is called the International Thermonuclear Experimental Reactor, or ITER (EE-tur). It is expected to cost about thirteen thousand million dollars over the next thirty years. The European Union plans to pay for forty percent of the project.

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For years, scientists have said nuclear fusion could produce unlimited¹² amounts of energy. Nuclear fusion is a natural process. It is the process that makes the sun and other stars shine. Nuclear fusion involves the central parts of small atoms such as hydrogen.

Deep inside the sun, extreme heat and pressure cause the atoms to join together. This fusion of two hydrogen atoms forms a different element: helium. It also releases a large burst of energy. This is the heat and light produced by the sun. Nuclear fusion is different from the process used in nuclear power centers. That process is called nuclear fission¹³. Fusion is the opposite of fission.

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Fusion creates energy by joining atoms together. Fission creates energy by splitting atoms apart. Fusion produces only a small amount of radioactive waste. Fission produces large amounts of highly radioactive waste that must be kept in containers for thousands of years.

Supporters of the nuclear fusion process say it is safer than fission. They say a fusion reaction can be stopped easily. There is another reason people are excited about nuclear fusion. The process uses a fuel supply that is huge and low in cost.

The fuel is a heavy form of hydrogen called deuterium. Deuterium is found in all the world's oceans. It can be taken from the water easily and in almost endless amounts. Experts say about one-half kilogram of fusion fuel could produce as much energy as three and one-half million liters of oil.

 
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VOICE TWO:

Many people take vitamin supplements to improve their health. In the United States, pills containing Vitamin E are among the most popular. Americans spent seven hundred ten million dollars on Vitamin E last year.

Recently, American researchers reported that Vitamin E supplements might do more harm than good. They said people who take large amounts of Vitamin E could be increasing their risk of dying early.

Edgar Miller¹⁵ of Johns Hopkins University led the study. He presented the findings at a meeting of the American Heart Association in New Orleans, Louisiana.

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Doctor Miller and his team combined and examined the results of nineteen studies on the effects of Vitamin E. The studies involved almost one hundred thirty-six thousand people in North America, Europe and China.

The researchers found no increased health risk from taking small amounts of Vitamin E. About thirty international units of Vitamin E are present in a single multivitamin pill.

However, the team found an increased risk of dying among people who took four hundred international units a day or more. Their death rate was thirty-nine for every ten thousand persons in the combined studies.

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A supplement trade group, the Council for Responsible Nutrition, criticized the findings. It said the study greatly overstated their importance.

Earlier studies had suggested that Vitamin E blocks the harmful effects of oxygen. That is why so many Americans take vitamin supplements to reduce their risk of heart disease and other disorders¹⁶.

Doctor Miller says his team believes there is no need for people to take large amounts of Vitamin E. He reportedly said people should get enough Vitamin E from the foods they eat. You can get up to ten international units of it from seeds, vegetable oils, olives, spinach¹⁷ and other green vegetables.

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VOICE ONE:

This program was written by Jerilyn Watson and Brian Kim. Cynthia Kirk was our producer. Our engineer was Dwayne Collins. I'm Sarah Long.

VOICE TWO:

And I'm Bob Doughty. Join us again next week for SCIENCE IN THE NEWS in VOA Special English.