環(huán)球英語 — 23：Bats
Voice 1
Hello. I’m Mike Procter.
Voice 2
And I’m Marina Santee. Welcome to Spotlight. This programme uses a special English method of broadcasting. It is easier for people to understand, no matter where in the world they live.
Voice 1
What do you think of when you hear bats flying near you? Do you imagine friendly looking creatures? Probably not! Bats are not very popular creatures! And many people find them a little frightening. This is partly because of false stories surrounding the creatures. In today’s programme we look at how this small creature may have the answer to one of our biggest health problems!
Voice 2
The bat’s body is designed well! A bat is not a bird. It is the earth’s only flying mammal! A bat’s wing has two layers of skin. The skin stretches between the bat’s long finger bones, then down the side of its body and back leg. The bat’s ‘thumb’ sticks out at the front of the wing. It is free to hold on to trees and walls.
Voice 1
There are almost a thousand different kinds of bat! But all bats fit into one of two main groups - ‘mega bats’ or ‘micro bats.’ Mega bats are large. A mega bat can weigh up to one kilogram. And its wings can be about two metres across! Mega bats live in hot rainforests - such as in Africa or Australia. They eat fruit. Or, they drink the sweet liquid nectar from flowers.
Voice 2
Micro bats are much smaller. The smallest weighs only about two grams. And its wings are about fifteen centimetres across. Micro bats live all over the world. They eat mostly insects. One of the most well known bats is a micro bat. It is the vampire bat! People take an interest in this bat mainly because of its name - vampire bat!
Voice 1
Vampires are imaginary creatures. They exist in films and books. They have human-like bodies. And they usually have some kind of supernatural power. They survive by drinking blood - at night! Vampires bite their victim’s neck with their sharp pointed teeth. Vampires are not real. They do not exist. But the vampire bat still takes its English name from them. This is because the vampire bat survives by drinking blood!
Voice 2
The vampire bat is the only kind of bat that drinks blood. It makes a small bite in the skin of a sleeping animal. The bat has a way of helping the blood to flow. Without this, the blood would grow thick quickly, and the bat could not drink.
Voice 1
The secret is in the liquid inside a bat’s mouth, the saliva. The saliva contains a chemical that stops the victim’s blood from becoming thick. This chemical is very interesting to scientists. In fact, they are now researching the use of this chemical. They are performing tests using the chemical to treat strokes.
Voice 2
Over four million [4,000,000] people die from strokes each year. The most common kind of stroke is an ischemic stroke. An ischemic stroke can happen when something blocks one of the blood tubes leading to the brain. These tubes, or arteries, carry blood and oxygen to the brain. So a blocked artery prevents oxygen reaching the brain. A ‘stroke’ is when some of cells in the brain die as a result of the blocked artery.
Voice 1
Melissa Welch worked in a store after school. One day, she felt sick. It seemed like the room was going round and round. Another worker found Melissa at the back of the store. Melissa was unable to speak. She could not stand up. A blocked artery was starving her brain of oxygen. Melissa was experiencing the beginnings of a stroke.
Voice 2
Fast treatment is very important with strokes. Melissa got to the hospital quickly. And doctors were able to save her life. But many people do not get fast treatment. This is because they do not recognise the signs of a stroke. This is true particularly with strokes that are not severe. Some of the signs of a stroke include:
Voice 1
Difficulty speaking or understanding speech
Voice 2
Difficulty walking.
Voice 1
A sudden loss of balance.
Voice 2
A severe pain in the head.
Voice 1
Sudden eye problems.
Voice 2
And weakness or a loss of movement in one side.
Voice 1
Doctors say that people showing these signs should seek help immediately. They should not wait for the signs to go away. Fast treatment can be the difference between life and death.
Voice 2
Since 1996, doctors have used a drug called ‘tPA’ to help people like Melissa. tPA breaks down the blood clot that blocks the artery. But it is only effective for small clots. And, it gives doctors only three hours to fight the damage.
Voice 1
So doctors used a new device for Melissa. It is called the ‘Merci Retriever, or just ‘Merci.’ The Merci is good because it gives doctors more time to work. They have up to eight hours to fight damage. The Merci works by using a special wire to take hold of the clot and pull it out. Doctors made a small cut in the very top of Melissa’s leg. They carefully fed the Merci device into an artery. They guided it up to the affected area of the brain. A few minutes after the operation, blood started to flow again. Oxygen fed into Melissa’s brain. The Merci Retriever saved her life!
Voice 2
However the Merci Retriever and tPA both have limits. They are not good at dealing with with large clots that are deep inside the brain. Is there hope for patients with this problem? Well, yes - one hope comes in the form of a bat!
Voice 1
Remember, the vampire bat drinks the blood from the wounds of its victims. It produces a special chemical that stops the blood clotting. Well, scientists have genetically engineered this chemical to produce a new drug - desmoteplase. Desmoteplase can break down blood clots. It can return blood flow to the brain up to nine hours after a stroke. Desmoteplase is also able to break up clots without affecting blood clotting in other parts of the body. Most importantly it does not increase the risk of ‘bleeding on the brain.’
Voice 2
Early studies of desmoteplase have shown promising results. Doctors gave patients desmoteplase within three to nine hours of a stroke. In one study, blood flow to the brain returned to fifty five percent of test patients. Doctor Howard Rowley from the University of Wisconsin Medical School said,
Voice 1
‘It is the biggest breakthrough I have seen in twenty years.’
Voice 2
Vampire bats are probably the most disliked kind of bat. But, they may hold an answer to one of the world’s leading causes of death - strokes. It seems that nature has many secrets we have yet to discover. Who knows what other solutions may be in the creation that is all around us.
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