VOA慢速英语2009年-SCIENCE IN THE NEWS - Aspirin Research Kee

VOICE ONE:

This is SCIENCE IN THE NEWS in VOA Special English. I'm Bob Doughty 1.

VOICE TWO:

And I'm Faith Lapidus. This week, we will tell the story of aspirin 2.

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VOICE ONE:

People have known since ancient times that aspirin can reduce pain and high body temperature. But that is not all the drug can do. It has gained important new uses in recent years. Low amounts may help prevent health threats from stroke to heart attack. Recently, researchers reported that aspirin could help patients with one kind of cancer live longer.

At the same time, doctors warn that acid in aspirin can cause bleeding in the stomach and intestines 4.

But there is promising 5 evidence of a way to reduce the risk of bleeding. A newly reported British study suggests that taking another drug with a small amount of aspirin may help solve the problem. If that proves true, it would help thousands of people who are seeking to prevent life-threatening conditions.

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So, how did aspirin become so important? The story begins two thousand years ago with a willow 6 tree. The Greek doctor Hippocrates advised his patients to chew on the bark and leaves of the willow.

The tree contains a chemical called salicin. In the eighteen hundreds, researchers discovered how to make salicylic acid from the chemical. In eighteen ninety-seven, a chemist named Felix Hoffmann at Friedrich Bayer and Company in Germany created acetyl salicylic acid.

Later, it became the active substance in a medicine that Bayer called aspirin. The "a" came from acetyl. The "spir" came from the spirea plant, which also produces salicin. And the "in"? That is a common way to end medicine names.

VOICE ONE:

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 the expansion, or swelling 7, of damaged tissue. Others protect the lining 8 of the stomach and small intestine 3.

Prostaglandins also make the heart, kidneys and blood vessels 10 work well. But there is a problem. Aspirin works against all prostaglandins, good and bad.

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VOICE TWO:

Scientists learned how aspirin interferes 12 with an enzyme 13. One form of this enzyme makes the prostaglandin that causes pain and swelling. Another form of the enzyme creates a protective effect. So aspirin can reduce pain and swelling in damaged tissues. But it can also harm the inside of the stomach and small intestine. Sometimes it can cause bleeding.

Aspirin competes with many other medicines for pain and fever these days. The competition includes acetaminophen, the active substance in products like Tylenol. Like the medicine ibuprofen, aspirin is an NSAID -- a non-steroidal anti-inflammatory drug.

VOICE ONE:

Many people take aspirin to reduce the risk of a heart attack or stroke from blood clots 14. Clots can block the flow of blood to the heart or brain and cause a heart attack or stroke. Scientists say aspirin prevents blood cells called platelets from sticking together to form clots.

A California doctor named Lawrence Craven first noted 15 this effect about sixty years ago. He observed unusual bleeding in children who chewed on an aspirin product to ease the pain after a common operation.

Doctor Craven believed that the bleeding took place because aspirin prevented blood from thickening. He thought that this effect might help prevent heart attacks caused by blood clots.

He examined the medical records of eight thousand aspirin users and found no heart attacks in this group. He invited other scientists to test his ideas. But it was years before large studies took place.

VOICE TWO:

Charles Hennekens of Harvard Medical School led one of the studies. In nineteen eighty-three, he began to study more than twenty-two thousand healthy male doctors over forty years of age. Half took an aspirin every other day. The others took what they thought was aspirin. It was only a placebo 16, a harmless substance.

Five years later, Doctor Hennekens reported that those who took aspirin reduced their risk of a heart attack. But they had a higher risk of bleeding in the brain than the other doctors.

VOICE ONE:

More recently, a group of experts examined studies of aspirin at the request of federal health officials in the United States. The experts said people with an increased risk of a heart attack should take a low-strength aspirin every day.

Aspirin may help someone who is having a heart attack caused by a blockage 17 in a blood vessel 9. Aspirin thins the blood, so it may be able to flow past the blockage. But heart experts say people should seek emergency help immediately. They say an aspirin is no substitute for treatment.

VOICE TWO:

Studies also suggest that aspirin can help with cancer prevention and survival. Several studies have found that men who take NSAIDS have a decreased risk of prostate cancer. The prostate is part of the male reproductive system.

Researchers at the Mayo Clinic in Minnesota wanted to see how NSAIDs might affect prostates that are enlarged but not cancerous. They followed the health of two thousand five hundred men for twelve years. One-third were taking NSAIDs daily when they entered the study.

The researchers said these drugs may delay or stop development of an enlarged prostate. They said the risk of an enlarged prostate was fifty percent lower in the NSAID users than the other men. The risk of bladder problems was thirty-five percent lower.

VOICE ONE:

Another study found that aspirin blocks the formation of blood vessels that feed cancer growth. Researchers at Newcastle University in England explored a biological process that makes blood vessels grow.

The researchers studied how aspirin affects the cells found on the inner surface of blood vessels. They found that a small amount of aspirin suppressed the way the cells form tubes.

Studies have found that aspirin may help prevent cancers of the stomach, intestines and colon 18. Research reported earlier this year told about people who had colorectal cancer. They found that aspirin users had an almost thirty percent lower risk of dying from their cancer. That was during an average of eleven years after the cancer was discovered.

VOICE TWO:

Aspirin does not help everything, however. It can cause problems. For example, it can interfere 11 with other medicines, although this is true of many drugs.

Also, some people should not take aspirin. People who take other blood thinners or have bleeding disorders 19 are among this group. Pregnant women are usually told to avoid aspirin.

Research has shown a link between aspirin use and the disease Reye's Syndrome 20. Children's doctors say patients up to age nineteen should not take anything containing Salicylatic products when sick with high temperatures.

The National Reye's Syndrome Foundation warns about aspirin use, especially during the spread of influenza 21. In the past, children have died or suffered permanent harm from Reye's Syndrome during widespread influenza attacks.

VOICE ONE:

People taking low-dose aspirin who fear stomach and intestinal 22 ulcers 23 and bleeding had some good news a few months ago. The British medical journal "Lancet" published a study about the drug famotidine, also known as Pepcid. The study suggested that famotidine taken with low-dose aspirin may prevent ulcers. This break down of tissue can cause bleeding.

The patients took seventy-five to three hundred twenty-five milligrams of aspirin a day. After twelve weeks, three percent of those taking famotidine with the aspirin had stomach ulcers. But fifteen percent of those taking the placebo and aspirin had them. Upper intestinal ulcers were found in only one-half of one percent of the famotidine group. In the placebo group, seventeen percent had these ulcers.

VOICE TWO:

Still, medical experts say people should not take aspirin for disease prevention without first talking to a doctor.

There are risks, and researchers have reported that some people get little or no protection from aspirin. But research continues to give new life to one of the oldest and most widely used drugs in the world.

VOICE ONE:

This SCIENCE IN THE NEWS was written by George Grow and Jerilyn Watson. Our producer was Brianna Blake. I'm Bob Doughty.

VOICE TWO:

And I'm Faith Lapidus. Join us again next week for more news about science in Special English on the Voice of America.