VOA Special English 慢速英语听力材料

SCIENCE IN THE NEWS - Digest
Broadcast: March 26, 2002

VOICE ONE:

This is Sarah Long.

VOICE TWO:

And this is Bob Doughty with Science in the News, a VOA Special English program about recent developments in science. Today, we tell about new kinds of drugs to fight the virus that causes AIDS. We tell about an experiment to create nuclear fusion in the laboratory. And we tell about an operation to transplant a woman's uterus.

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VOICE ONE:

Researchers are testing powerful new drugs designed to fight H-I-V, the virus that causes AIDS. Experts hope that the new drugs will help people who are not being helped by current medicines. Scientists reported about the new drugs during a yearly AIDS meeting called the Conference on Retroviruses and Opportunistic Infections. It was held last month in Seattle, Washington.

The Centers for Disease Control and Prevention says about nine-hundred-thousand people in the United States are infected with the AIDS virus. That is an increase of about fifty-thousand from Nineteen-Ninety-Eight. Experts say the increase is because people with the disease are surviving longer.

VOICE TWO:

The C-D-C found that at least forty-two percent of people with H-I-V in the United States either do not know they are infected or are not being treated. Another C-D-C study found that people who delay treatment have much higher death rates.

Existing drugs have sharply reduced the number of deaths from AIDS. However, H-I-V can change into drug-resistant forms. And the medicines to treat the disease can cause severe side effects.

Scientists say the new AIDS drugs do not cure H-I-V. However, they may offer help to people who are not being helped by existing medicines.

VOICE ONE:

There are about fifteen drugs that are used to prevent H-I-V from reproducing in the body. Their goal is to slow or stop the disease from progressing. The drugs work by attacking two of the three enzymes that the virus uses inside a human cell. Some of the new medicines target the third enzyme, called integrase. Integrase is the enzyme that places H-I-V genes into the genes in human cells, making the infection permanent.

VOICE TWO:

Other new drugs try to prevent H-I-V from entering the cell. Researchers began studying these drugs during the Nineteen-Nineties. At that time, they found that some people did not become infected with H-I-V, although they were exposed to the virus several times. Some of these people had a different form of a protein on the surface of their cells. In order to infect a cell, H-I-V must attach to this protein. But the virus can not attach to the different form of this protein, so it can not enter the cells.

VOICE ONE:

Scientists at the AIDS conference also heard about the early success of new drugs designed to avoid resistance problems. One of them is one of the most powerful anti-H-I-V drugs developed. Experts say the drug appears to sharply suppress the amount of virus in the blood. They say it appears to work as well as five older drugs taken in combination.

This drug would not be used alone, however. Most anti-AIDS drugs are taken in combinations of three or more to be effective. Many anti-AIDS drugs seem to be extremely powerful at first. But they prove to be useless later as the virus changes.

A few of the new anti-AIDS drugs discussed at the conference are expected to be approved soon by the United States government. However, most of the drugs have just started being tested on people. Others are still being developed.

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VOICE TWO:

American scientists are studying an experiment that reportedly created nuclear fusion in a laboratory. The fusion experiment was performed at the Oak Ridge National Laboratory in Tennessee. Experts say the work, if successful, could someday provide almost unlimited supplies of low-cost energy.

However, some scientists are questioning the experiment. They note that another team of scientists claimed to have produced fusion thirteen years ago. Yet no one else could ever reproduce that result.

VOICE ONE:

Fusion is the process that makes the sun and other stars shine. Atoms of hydrogen are pressed together and heated so intensely that they join or fuse together. This fusion forms a different element, helium. It also releases a large burst of energy - the heat and light sent out by the sun.

Fusion energy already exists on Earth. It is the power of the hydrogen bomb. However, scientists have not been able to produce this kind of energy in a safe, peaceful way.

Scientists have been working on the problem for almost fifty years. Generally, their work includes attempts to build a copy of the intense pressure and heat of the sun. They believe such pressure and heat are needed for fusion.

VOICE TWO:

The team of scientists at the Oak Ridge National Laboratory performed the latest experiment. Science magazine published the findings.

The scientists sent sound waves into a small glass container that had the liquid chemical acetone. Acetone is a chemical in which the normal hydrogen atoms are replaced with deuterium. Deuterium is a heavy form of hydrogen that is capable of fusion reaction.

The scientists then shot neutrons into the container. The scientists say this caused small particles of gas in the liquid to expand quickly. They say these bubbles then imploded, creating bursts of light. This created high pressure that caused deuterium atoms to fuse, releasing intense energy.

VOICE ONE:

An independent group of scientists examined the findings before they were published. Science magazine delayed the publication when other scientists at Oak Ridge could not reproduce the experiment.

Science magazine published a commentary with the report. One scientist noted that the device used by the Oak Ridge scientists could be a tool for studying nuclear fusion in the laboratory, if the findings are confirmed. He added that scientists will - and should - question the findings until the experiment is reproduced by others.

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VOICE TWO:

Doctors in Saudi Arabia have performed the first human uterus transplant operation. The doctors say the woman who received the uterus had two monthly fertile periods after the operation. However, the uterus had to be removed after three months. Doctors say the experiment shows that a uterus transplant operation is technically possible. Yet some experts say it is very risky and question its value.

VOICE ONE:

The uterus transplant operation was performed two years ago at the King Fahad Hospital and Research Center in Jeddah, Saudi Arabia.

Doctors transplanted the uterus into a twenty-six year old Saudi woman. Doctors had removed her uterus six years earlier because of uncontrolled bleeding after the birth of her first child. The woman wanted to have another baby. The transplant organ came from a forty-six-year-old woman. She had a condition that required the removal of her reproductive organs. However, her uterus was healthy.

VOICE TWO:

The younger woman took powerful drugs both before and after the operation so her body would not reject the organ. The drugs suppressed her body's natural defenses against disease. She also was given hormone injections to help the transplanted uterus develop normally.

The doctors say the uterus performed normally for ninety-nine days. Then tests showed that blood flow to the organ had stopped. That forced doctors to remove it.

VOICE ONE:

The International Journal of Gynecology and Obstetrics described the experiment. A commentary published with the report said the operation should be considered a success. Some American experts said the experiment offered hope to women who want to have a baby and have been unable to do so.

Other experts question the idea of such a transplant operation. Most organ transplant operations are done to save a patient's life. They argue that a uterus is not necessary for a woman's survival. They also note that the anti-rejection drugs that a woman must take have strong side effects. These might harm a developing fetus.

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VOICE TWO:

This Science in the News program was written by Cynthia Kirk and George Grow. It was produced by Nancy Steinbach. This is Bob Doughty.

VOICE ONE:

And this is Sarah Long. Join us again next week for more news about science in Special English on the Voice of America.