VOA慢速英语 2008 1111b（在线收听）

VOICE ONE:

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

VOICE TWO:

And I'm Barbara Klein. This week, we will tell about a fat cell gene linked to colon cancer. We will also tell about new developments in the fight against the disease tuberculosis. And, we will tell about something new at America's Smithsonian Institution.

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VOICE ONE:

A new study has found that a fat cell gene may reduce the risk of colon cancer in some people. The study provides what scientists say is the first evidence of a genetic link between a fat cell gene and colon cancer. The finding could lead to better tests for the disease and measures to help prevent it.

Current evidence suggests a relationship between obesity, insulin resistance and colon cancer risk. The scientists say what they have found now is an area of a gene that is connected with the cancer risk. They say this area is most likely not the cause of the disease. But they think it is where the connection comes from.

VOICE TWO:

The gene is involved in the formation of a hormone called adiponectin. Some people have higher levels of this hormone in their blood. Others have lower levels. Higher levels have been linked with lower rates of obesity and insulin resistance. Lower levels have been linked with higher rates.

The Journal of the American Medical Association published the findings last month.

Colon cancer is one of the leading causes of cancer deaths. Every year it kills almost six hundred eighty thousand people around the world. And, doctors find more than one million new cases each year. The disease is highly treatable if discovered early.

VOICE ONE:

The research involved two studies with a total of about one thousand five hundred people. The larger of the two studies involved New Yorkers of Ashkenazi Jewish ancestry. Colon cancer is more common in Jews of eastern European ancestry than in the general population. The other study involved people of different ethnicities from Chicago, Illinois.

Currently, American medical experts advise colonoscopy tests for colon cancer to begin at the age of fifty. A colonoscopy can find and remove growths before they become cancerous. But the test is invasive and can be uncomfortable.

An earlier study expressed support for a test called a virtual colonoscopy. It uses X-ray and computer technology to search for growths, but cannot remove them.

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VOICE TWO:

An estimated one-third of all people are infected with tuberculosis. Most have latent, or inactive, cases. They do not suffer coughing, increased body temperature or other signs of active TB.

But each year, about nine million people develop active cases and two million die. The victims are mostly poor and live in developing countries. TB is an ancient bacterial disease. It can be cured with antibiotics, if patients take all their medicine.

VOICE ONE:

For the past century, a skin test has been used to identify latent TB. When cases are found, treatment can prevent many from becoming active. But the preventive drugs have a risk of side effects.

The skin test depends on the body's reaction to an injection of specially prepared TB protein. But the test often falsely identifies people as having latent TB if they have been vaccinated against the disease.

VOICE TWO:

To avoid needless treatment, scientists have developed a blood test. This test is designed to identify patients with a high risk of developing the active form of TB.

An international team developed the blood test, called ELISpot. A study showed that the ELISpot blood test identifies latent TB while giving fewer false positive results.

The researchers say the ELISpot test has been suggested for use in about twenty countries worldwide. A report on the test appeared last month in the Annals of Internal Medicine.

VOICE ONE:

In another development, scientists have reported a step toward a better vaccine against TB. One currently used is seventy-five years old. The new, experimental vaccine contains a weakened TB bacterium from a strain of the current vaccine. The scientists say their study showed that the experimental vaccine created stronger reactions against TB than the traditional one.

But the new vaccine contains an antibiotic-resistant gene that the scientists do not want released into the environment. So future tests of the vaccine are not planned. But research will continue on a similar one that does not contain the gene.

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VOICE TWO:

From space, our planet looks blue. Earth, after all, is mostly covered with water -- an ocean planet. In September, an exhibit about the oceans opened at the Smithsonian Institution's National Museum of Natural History in Washington, D.C.

The exhibit explores the beauty and mystery hidden under the sea. It uses the Smithsonian's huge collection of underwater life to show that all life on our planet is in some way connected to its oceans.

The first thing that a visitor sees is a huge reproduction of a North American Right Whale. It is a model of Phoenix, a whale that scientists have studied since she was born near the coast of Georgia in nineteen eighty-seven. There are only four hundred of these right whales left. They were once considered the "right whale" to hunt because they are big and slow. Phoenix is the biggest of ninety-seven models in the exhibit.

VOICE ONE:

Near the top of the museum's Sant Ocean Hall are eight huge video screens showing images of underwater life. The video images give the sensation that visitors are surrounded with marine life. The room is also alive with technology. Twenty-four computer stations show videos and educational programs.

Among the rarest sights at the exhibit are two giant squids. These secretive creatures live hundreds of meters beneath the sea. No one had even seen a living giant squid before scientists captured one on video in two thousand four. But the Hall has two, both preserved in a special, clear liquid. The largest one is more than seven meters long. It was caught near Spain three years ago and loaned to the Smithsonian.

VOICE TWO:

For all the big creatures at the exhibit, there are hundreds of smaller ones of interest. Many glass containers hold preserved animal remains that were taken from the museum's collection. With eighty million objects, the Smithsonian's marine collection is the largest in the world.

Visitors can also look back in time. There is an example of a coelacanth. The coelacanth swam the ocean sixty-five million years ago. Scientists thought it had disappeared from the Earth. But this ancient-looking fish was discovered living near the coast of South Africa in nineteen thirty-eight. Scientists consider it a living fossil.

VOICE ONE:

Sharks are of interest to many visitors. They create feelings of both fear and wonder. Visitors can see the huge jaws of sharks lined with sharp teeth. There are also examples of sharks gathered from the deep ocean. They caught the attention of Elim Babylon. He visited the Sant Ocean Hall with his grandmother, Sally Babylon.

ELIM BABYLON: "I really like the one back there, like the deep sea, sea one. It's really cool because it has all these sharp teeth."

SALLY BABYLON: "We want to share this kind of thing with him and we want to make him a better steward. I just want to pass on to him both my appreciation of the beauty of it and also the care that it takes."

Not everything in the exhibit is preserved. There is a four-hundred-liter tank that contains over fifty kinds of brightly colored fish and other sea life. The tank is designed to look like a coral reef in the Indian or Pacific Ocean.

VOICE TWO:

It is difficult to believe that some of the creatures shown at the exhibit come from our own planet. A video, for example, shows organisms that live near the ocean bottom where volcanic activity heats the water to hundreds of degrees. Even at these hot volcanic vents, bacteria survive using the poisonous chemical hydrogen sulfide to create food.

However, human beings are connected to the ocean in more ways than we know. Very small ocean plants called phytoplankton create more than half of the world's oxygen. And it is the ocean that powers the Earth's weather. The exhibit also examines the human connection to the oceans. It explores issues such as over-fishing, pollution and climate change. Each is designed to bring visitors a deeper knowledge of a largely unexplored territory -- our oceans.

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VOICE ONE:

This SCIENCE IN THE NEWS was written by Mario Ritter, Jerilyn Watson and Caty Weaver. Our producer was Dana Demange. I'm Bob Doughty.

VOICE TWO:

And I'm Barbara Klein. Listen again next week for more news about science, in Special English, on the Voice of America.