SCIENCE IN THE NEWS

（单词翻译）

SCIENCE IN THE NEWS
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Broadcast: Tuesday, June 08, 2004

VOICE ONE:

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

VOICE TWO:

And I'm Bob Doughty¹. Today we talk about a medicine that has found new uses over time.

VOICE ONE:

 
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And may find even newer ones. Learn the history of aspirin³, and the most recent findings, coming up.

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More than two-thousand years ago, in ancient Greece, Hippocrates advised his patients about a way to ease pain. The great doctor told them to chew on the bark of the willow⁴ tree. The outer covering of the tree contains a chemical, salicylic acid.

By the seventeen-hundreds, people used willow bark to reduce high body temperatures.

In eighteen-sixty, researchers at the Bayer Company in Germany copied nature. They created acetyl salicylic acid. And they took a name from the spirea plant, which also contains the natural chemical. They called their new formula aspirin.

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Aspirin has been sold for more than a century as a treatment for headaches, muscle pain and high temperature.

In nineteen-eighty-two, a British scientist shared the Nobel Prize in Medicine in part for discovering how aspirin works. Sir John Vane found that aspirin blocks the body from making natural substances called prostaglandins.

Prostaglandins have several effects on the body. Some cause pain and swelling⁵ in damaged tissue. Others protect the lining⁶ of the stomach and small intestine⁷. Prostaglandins also make the kidneys, heart and blood vessels⁸ work well. But there is a problem. Aspirin works against all prostaglandins, good and bad.

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Scientists learned how aspirin interferes¹⁰ with an enzyme¹¹. One form of this protein makes the prostaglandin that causes pain and swelling. Another form of the enzyme creates the protective kind of compound. So aspirin can reduce pain and swelling in damaged tissues. But it can also harm the lining of the stomach and small intestine.

Aspirin competes these days with a lot of other pain medicines. Many people like to take acetaminophen. This is the active substance in products like Tylenol. Still, experts say aspirin does some things that the others cannot.

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Many people take aspirin to reduce the risk of a heart attack.

Scientists say aspirin prevents tiny blood cells called platelets from sticking together to form clots¹². Clots can block the flow of blood to the heart or the brain. This can cause heart attacks or strokes.

The use of aspirin to reduce the risk of heart disease has grown in recent years. Yet one doctor noted¹³ this effect in the nineteen-fifties.

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The doctor was Lawrence Craven. He observed unusual bleeding among children who chewed on aspirin gum to ease pain after a throat operation. Doctor Craven believed they were bleeding because aspirin prevented the blood from thickening. He decided¹⁴ that aspirin might help prevent heart attacks caused by blood clots.

So Doctor Craven examined medical records of about eight-thousand people. He found no heart attacks or strokes among those who regularly took aspirin. Doctor Craven invited other scientists to test his ideas. But it was many years before large studies took place.

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Doctor Charles Hennekens of the Harvard Medical School in Boston, Massachusetts, led one of the studies. In nineteen-eighty-three, he began to study more than twenty-two-thousand healthy male doctors over the age of forty.

Half the doctors in the study took an aspirin every other day. The other half took what they thought was aspirin, but was just a sugar pill. Five years later, Doctor Hennekens reported that the men who took aspirin reduced their chances of a heart attack. However, the men who took aspirin also had a higher risk of bleeding in the brain.

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In recent years, a group of American medical experts examined studies on aspirin for the Department of Health and Human Services. The experts said people who have an increased risk of a heart attack should take a small amount of aspirin every day.

People who are most likely to suffer a heart attack include men over the age of forty and women over the age of fifty. People who weigh too much or smoke cigarettes are also at greater risk. So are people with diabetes¹⁵, heart disease, high blood pressure or high cholesterol¹⁶.

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Aspirin may help someone who is having a heart attack caused by a blockage¹⁷ in the flow of blood to the heart. Aspirin thins the blood. This can permit blood to flow past the blockage in the artery¹⁸. But heart experts say people should seek emergency help immediately. They say an aspirin is no substitute for treatment.

Some people should not take aspirin. These include people who have stomach problems. Doctors say people who take other blood thinners or have bleeding disorders¹⁹ should not take aspirin either.

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Some studies have been done on the effects of taking aspirin during the first signs of a stroke. These studies showed some improvement in the condition of the patients. But can aspirin prevent strokes in healthy people?

The Archives of Neurology published a report in two-thousand about aspirin and stroke prevention. Robert Hart and others at the University of Texas at San Antonio examined studies of more than fifty-thousand healthy people.

Some of the people already had an increased risk of stroke, like high blood pressure. Others had no signs that they might suffer a stroke in the future.

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The researchers found that aspirin did not seem to prevent strokes, as long as people had no signs of blocked blood vessels in their brain. Doctors say aspirin may help prevent small strokes that result from such blockage. But the report said aspirin was linked to a small increase in the risk of bleeding in the brain. This can also cause a stroke.

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Like other medicines, aspirin can cause problems, especially if taken in large amounts. The acid in the drug may damage the tissue of the stomach or intestines²⁰. Aspirin can also interfere⁹ with the healing of the cells. Some people develop severe bleeding.

Yet other research has found that aspirin may help prevent cancers of the stomach and intestines. Studies in the last twenty years have shown that people who take aspirin have unusually low rates of such cancers.

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One of the newest reports about aspirin involves the most common form of breast cancer. In May, researchers announced findings from a study of almost three thousand women in New York City. The study compared women who took aspirin several times a week to women who did not. Scientists from Columbia University say the aspirin users had a twenty-five percent lower rate of breast cancer.

One of the doctors involved in the study said aspirin appeared to reduce the production of estrogen. This female hormone²¹ is linked to up to seventy percent of all cases of breast cancer.

The Journal of the American Medical Association published the findings. But the researchers say they are not ready to advise women to take aspirin in hopes of protection against breast cancer.

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But doctors do often advise aspirin for patients at risk of diseases that result from blood clots, such as a heart attack. In May, a Harvard Medical School publication said that some people, however, get little or no protection from aspirin. The Harvard Heart Letter said this idea is so new that many doctors do not know about it, or they are waiting for more research. Still, the report advised that it is not too early for people to ask about being tested to see if they respond to aspirin.

In any case, medical experts say no one should take aspirin for disease prevention without first asking a doctor. Aspirin is sold in different strengths. It can interfere with other drugs. And it is not safe for everyone. Most pregnant women are told to avoid aspirin. Children who take aspirin can suffer a serious disease called Reye's syndrome²².

Yet, even with its problems, aspirin remains²³ one of the oldest, least costly²⁴ and most widely used drugs in the world.

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VOICE TWO:

This SCIENCE IN THE NEWS program was written by Caty Weaver²⁵ and produced by Cynthia Kirk. This is Bob Doughty.

VOICE ONE:

And this is Sarah Long. Join us again next week for more news about science in VOA Special English.