SCIENCE IN THE NEWS - Drug Used to Treat a Bleeding Disorder（在线收听）

SCIENCE IN THE NEWS - Drug Used to Treat a Bleeding Disorder May Also Aid Victims of the Deadliest Form of Stroke
By Cynthia Kirk, Ed Stautberg

Broadcast: Tuesday, April 05, 2005

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

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See the differences?
And, I'm Steve Ember. On our program this week: a new map may help show why women are so different from men.

And we answer a listener's question about the bleeding disorder hemophilia.

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But first, a drug already used to treat persons with hemophilia offers hope for stroke victims.

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American doctors believe they may have found a new way to treat the most deadly form of stroke. The condition is called an acute intracerebral hemorrhage or bleeding stroke.

Strokes happen when blood stops flowing into the brain. Bleeding strokes are the least treatable form of stroke. They affect about fifteen percent of all stroke patients.

Bleeding strokes happen when high blood pressure causes a blood vessel in the brain to burst. The most common form of stroke is called an Ischemic stroke. It happens when the flow of blood in the brain or neck is blocked.

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Experts say bleeding strokes are much more serious. They say more than one-third of all persons who have a bleeding stroke die within a month. And only twenty-percent of those suffering a bleeding stroke regain full independence.

Doctors have long sought effective ways to improve survival rates. They say current medical treatments are only supportive. And, there have been no drugs to help stop the bleeding, which causes brain cells to die.

However, a new study suggests that a drug used to treat persons with hemophilia may be effective in treating bleeding strokes. Hemophiliacs lack a chemical in the blood called a clotting factor. This chemical helps to stop bleeding from everyday falls or cuts.

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The new study was carried out at seventy-three hospitals in twenty countries. The New England Journal of Medicine reported the results.

The study involved three hundred ninety-nine patients. Research scientists tested a drug called recombinant activated factor seven, or rFVIIa. It helps blood to thicken, or clot. In the United States, the drug has been approved to treat hemophiliacs since nineteen ninety-nine.

Most patients in the study received rFVIIa. The others took a harmless substance, or placebo. Researchers say the drug reduced bleeding by fifty percent. Patient survival rates rose about forty percent.

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The researchers said the drug worked best when the patient was treated within three hours of the stroke. They said patients had a two to three times greater chance of complete recovery. After three months, twenty-nine percent of the patients who took the placebo had died. Only eighteen percent of those who took the hemophilia drug were dead.

There were risks, however. Seven percent of patients who received the drug suffered a heart attack or stroke. The researchers said most of them recovered.

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Doctor Stephan Mayer of New York-Presbyterian Hospital was the lead investigator in the study. He said it will be at least two years before the United States Food and Drug Administration approves r-F-Seven-a for bleeding strokes.

If approved, the drug would become only the second emergency treatment for stroke in more than thirty years. The first was tissue plasminogen activator, or TPA. TPA. can break up blockages which cause most heart attacks and strokes.

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A short time ago, we spoke briefly about hemophilia. A listener in Vietnam, Nguyen Van Phuc, would like to learn more about this bleeding disorder.

When a person gets cut, they bleed. Usually, a protein in the blood, called a clotting factor, stops the bleeding. People with hemophilia do not have this chemical. They may bleed longer than other people after an accident or injury. Losing too much blood can be life threatening.

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People with hemophilia can pass it to their children. Generally, the disorder affects only men and boys. It affects about one in every five thousand males. Women who carry the hemophilia gene are called carriers. Each son of a carrier has a fifty percent of having the disorder. Each daughter has a fifty percent chance of being a carrier.

About thirty percent of hemophilia cases involve someone with no family history of the disorder. Scientists believe these cases result from changes, or defects, in genetic material.

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Blood tests can help to show if someone has hemophilia. Signs are first observed when the person is a baby or child. There may be bleeding into muscles or joints, resulting in damaged areas of skin. Or the person may bleed longer than expected after an injury, accident or dental work.

Hemophilia is a life-long condition. There is no cure. Yet there is an effective treatment for hemophiliacs. Doctors can give clotting factor to patients in blood products. Experts urge patients to see a doctor or health care worker who has experience with treating the disorder. Experts also advise patients to stay active and exercise.

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A team of more than two hundred fifty researchers says it has completed a map of the X chromosome. The researchers carried out their work at six scientific centers in Britain, Germany and the United States. They reported the results in the British publication Nature.

The work was done as part of the Human Genome Project. The goal of the project is to create a detailed map of all human genes.

The researchers said the new map should help scientists better understand the more than three hundred disorders linked to the X chromosome. They include hemophilia, colorblindness, and Duchenne's muscular dystrophy.

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A human fetus develops into either a boy or a girl because of the presence of genes found in chromosomes. Females have two X chromosomes. Males have one X and one Y. Males are more likely than females to develop diseases carried by an unusual, or defective, X chromosome.

Females who carry a defective X chromosome are protected because they have a second X chromosome. However, they can pass the defective chromosome to their sons. The researchers say other chromosomes probably carry just as many diseases as the X. However, such chromosomes are more difficult to study.

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The researchers studied how the sex chromosomes have changed over time. To do this, they examined the X chromosomes of animals such as dogs, rats, and chickens. They found the same gene order in human beings and dogs. Their findings show that the purpose of the Y chromosome has changed and now is limited to establishing male organs. This supports an idea that the X and Y chromosomes in mammals developed millions of years ago from the same group of chromosomes.

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Last year, we told you about the United States having limited supplies of a vaccine to protect against the disease influenza. A biotechnology company, Chiron, was unable to produce as many flu vaccines as planned. In the past, it provided about half the supply used in the United States.

Chiron makes its flu vaccine at a factory in Liverpool, England. The vaccine helps the body's natural defenses recognize and fight the disease.

Chiron reported last September that some of its flu vaccine failed inspections for purity. Also, British officials suspended the factory's production permit. They barred the company from sending almost fifty million vaccines to the United States. So, medical officials urged healthy Americans to delay getting the vaccine or not get one at all.

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Recently, officials announced that about seventeen million Americans chose not to get the flu vaccine last winter. The Centers for Disease Control and Prevention said this permitted persons most in need of the vaccine to get it. It also said that about as many sick persons, older adults and health care workers were protected as much as in past years.

Also, British officials announced that Chiron had improved conditions at the Liverpool factory. They also said it could restart production of flu vaccines.

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This program was written by Cynthia Kirk, Ed Stautberg, Nancy Steinbach and Caty Weaver. Our producer was Cynthia Kirk. I'm Steve Ember.

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