This is SCIENCE IN THE NEWS in VOA Special English. I’m Doug Johnson.
And I’m Faith Lapidus. On our program this week: new findings about the laboratory storage life of stem cells.
Up close with monarch butterflies on their yearly migration in North America.
And children are urged to get an early start on good heart health.
A new report says human embryonic stem cells kept for long periods of time develop changes in their genetic material. It says such changes may make the cells unusable for medical purposes.
Earlier studies had suggested that major genetic changes in stem cells were rare. But an international team of research scientists found this to be false. The publication Nature Genetics reported the findings.
The researchers used special tools to compare genetic changes in each of nine human embryonic stem cell lines. The stem cells were kept in a special liquid filled with nutrients. The researchers found that the more the cells divided, the more likely they were to develop the changes, or mutations.
Some of these mutations are known to cause cells to become cancerous. However, stem cells that divided for only a short period of time were found to show no signs of mutation.
Aravinda Chakravarti of Johns Hopkins University in Baltimore, Maryland, was a leader of the research team. Professor Chakravarti said additional experiments are needed to confirm the results. But he said it appears that stem cell lines may include harmful cells over time. As a result, he says, the life of stem cells and their usefulness for medical purposes may be limited.
For years, human embryonic stem cell research has remained in laboratories. Scientists have been studying what the cells can do and how they can be controlled. In time, however, they hope that stem cells can be used to replace or repair tissue damaged by disease or injury.
Stem cells taken from human embryos that are just days old have the ability to grow into other cells, such as heart, nerve or brain cells. Scientists hope to use collections of these specialized cells for medical treatments. The cells could then be put into patients suffering from heart disease or cancer, for example.
This latest study could strengthen calls for President Bush to permit the use of federal money for new stem cell lines. American law restricts federal aid for experiments involving human embryos. This is because an embryo must be destroyed so that stem cells can be collected. Opponents of stem cell research say this destroys human life.
Some members of the United States Congress are seeking to ease the restrictions on federal aid.
You are listening to SCIENCE IN THE NEWS in VOA Special English.
|The butterflies' path is from Canada through the United States to Mexico|
Each year, millions of monarch butterflies travel from Canada to Mexico and back again. The monarch is one of the few butterfly species that make a migratory trip. Every fall, monarchs gather in areas of Canada and the United States and fly to Mexico. This year, the migration is a little unusual. A group of humans will travel alongside the insects to record their trip.
The project is called Papalotzin. The word means "little butterfly" in the native Nahuatal language of central Mexico. Project director Francisco Gutierrez launched Papalotzin in an effort to help protect the butterflies for the future. The international wildlife-protection group WWF is providing support to the project.
Mister Gutierrez also is the pilot of what is called an ultralight airplane. It uses a very small engine and can only hold two people. There is no roof on the plane. The pilot and passenger are exposed to the weather in much the same way as the butterflies. Also, this ultralight has black-and-gold wings, just as the monarchs do.
Mister Gutierrez spoke to VOA during a stop in Washington, D.C. He noted that the weather is a big question in the use of an ultralight. He said when the butterflies do not fly, the ultralight does not fly.
Mister Gutierrez and his crew launched the ultralight in late August from the northeastern Canadian city of Montreal. The crew is from Canada, the United States and Mexico. Mister Gutierrez and his team will make a movie about the butterflies.
The team members will record the migration. They also will make stops along the way to hold news conferences and other events. Monarch butterfly experts and environmentalists will take part.
Monarch butterflies weigh less than one gram. They fly to different warmer homes in the winter depending on where they come from. A smaller group of monarchs that live west of the Rocky Mountains fly to trees along the coast of Southern California.
The larger group of monarchs live east of the Rockies. They travel even farther south. They spend their winters in the high mountain forests of central Mexico. The Papalotzin project is traveling with this group.
The butterflies’ final stop will be about four thousand five hundred kilometers from their starting point. The trip takes about three months to complete. The butterflies stay in Mexico from November through March.
The Mexican government has taken steps to protect the area that is the insects’ winter home. Mexico created the Monarch Butterfly Biosphere Reserve in nineteen eighty-six. The main purpose is to protect the forests. They are important to the environment and local communities.
But the cutting down of trees continued. So the government agreed to create a larger reserve. WWF supported the effort.
In two thousand the Mexican government expanded the protected area by more than three hundred percent. The reserve now covers more than fifty-six thousand hectares.
The declaration of a bigger reserve cancelled logging permits held by local communities. But with the expanded area came a financial plan to provide economic support to the communities. Now, WWF says, people are paid for their conservation efforts.
But an official of the group says illegal logging continues to be a problem in the forests.
Most monarch butterflies never get a chance to migrate. Most live only about a month. But once a year the species produces a special group. In late summer, longer-living monarchs are born. They live about seven months.
These butterflies make the trip to Mexico and spend the winter there. They give birth to their young on the way back north. Their young have the usual shorter lives.
The trip home to the northern United States and to Canada is really a flight of several generations. Butterflies are born, give birth and die along the way.
The World Heart Federation says two thirds of all children are not active enough. The group says about twenty-two million boys and girls under the age of five are severely overweight. Obese children often become obese adults. And obesity increases the risk of heart disease and other disorders.
The World Heart Federation says heart disease kills seventeen million people each year. Sunday, September twenty-fifth, was the yearly observance of World Heart Day. Heart experts urged parents to make sure their children get exercise and eat right. That means to eat a healthy and balanced diet, and to limit sugary drinks, sweets and eating between meals.
Tobacco also increases the risk of heart disease, cancer and many other conditions. The World Heart Federation says the younger someone begins to smoke, the greater the risk. Half of the young people who continue to smoke as adults are likely to die from a smoking-related disease.
The group also says that almost half of all children live with a smoker. It says these children can breathe as much tobacco as in more than two thousand cigarettes. And that is just by the age of five.
SCIENCE IN THE NEWS was written by George Grow, Caty Weaver and Jill Moss. Cynthia Kirk was our producer. I’m Doug Johnson.
And I’m Faith Lapidus. Internet users can find our programs at voaspecialenglish.com. To send us e-mail, write to email@example.com. We hope you join us again next week for more news about science, in Special English on the Voice of America.