VOA慢速英語(yǔ): 蠕蟲(chóng)準(zhǔn)備在太空中飛行

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Humans are well-equipped for life on Earth. But inspace, it is a different story. Low or zero gravitychanges how the blood flows and causes motionsickness, muscle loss and tiredness. Weightlessnesscan also cause bone loss. But scientists at theUniversity of Delaware are experimenting with littleworms to better understand how space travel affectsastronauts.

The millimeter-long worm is called C. elegans. Thesee-through invertebrate is often used in medicalstudies because its life is only about two weeks long. Seventy percent of its DNA is the same as humanDNA.

Chandran Sabanayagam is a scientist with theUniversity of Delaware. He built a micro-gravitysimulator to test how C. elegans would perform in theactual zero gravity of space.

"Imagine, if you have a container of water and you putan object in it, and it begins to settle to the bottom. But,before it hits the bottom, you flip the container upsidedown. And now it has to fall back down to the bottom.Before it reaches it, you flip it again. Essentially thisinstrument rotates and the object never hits thebottom. So essentially it's in freefall, similar to a satelliteorbiting the earth."

Scientists use a computer to watch the worms as theyturn. The computer shows the worms as they wouldlook under a microscope. Mr. Sabanayagam says theworms turn around and around in the simulator forabout one week.

After about a week the scientists take out the worms.They look for changes in the worms' epigenome. Theepigenome are chemical markers that tell the DNA in the cells how to perform. The epigenome can be changed by the environment. And those changes pass from one generation of worms to the next.

Mr. Sabanayagam studies the epigenome as it relates to microgravity.

"When the worms are in a liquid environment some epigenomic marks persist(remain) even when we take the animal out of the liquid environment and put itback into normal ground conditions. So its offspring retains this epigenomicmemory of the parents' liquid environment or microgravity environment."

The information the scientists have gathered suggests that the epigenomicmarks appear during the early part of a worm’s life. Mr. Sabanayagam saysidentifying epigenomic marks is important for human studies in the future.

He says he thinks scientists can find genes in the human genome similar tothose in the worms that responded to microgravity. He says scientists couldpossibly observe those genes closely when astronauts travel in space.

Chandran Sabanayagam expects C. elegans to visit the International SpaceStation within two years. He says he hopes information gathered from theworm studies can be used to develop simple, low-cost and quick tests tomeasure an astronaut's health.

I’m Jonathan Evans.

Rosanne Skirble reported this story from Washington. Jonathan Evansadapted it for Learning English. Caty Weaver edited it.

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Words in this Story

invertebrate – n. a type of animal that does not have a backbone

DNA – n. a substance that carries genetic information in the cells of plantsand animals; an abbreviation of deoxyribonucleic acid

rotate – v. to move or turn in a circle

simulator – n. a machine that is used to show what something looks or feelslike and is usually used to study something or to train people