SCIENCE IN THE NEWS #2068 - DigestBy Staff
This is Bob Doughty.And this is Sarah Long with SCIENCE IN THE NEWS, a VOA Special English program about recent developments in Science. Today, we tell about new research on the spread of the virus that causes AIDS. We tell about a map that shows how children's brains develop. And we tell about genes linked to the aging process.
Scientists say they have proven what they have long suspected about H-I-V, the virus that causes the disease AIDS. They found that an infected person who has a low amount of H-I-V in the blood is less likely to pass the virus to someone of the opposite sex.
The study is the largest ever to examine the link between viral level in a person's blood and the risk of passing H-I-V through sex. The findings suggest that reducing the amount of the virus in a person's blood may be one way to slow the rate of AIDS infections.
The study is part of a larger work that began in Uganda in Nineteen-Ninety-Four. American and Ugandan researchers studied more than fifteen-thousand people in the Rakai area. The researchers were trying to find out if people infected with other diseases spread through sex were more likely to become infected with H-I-V.The researchers found that having other sexually transmitted diseases did not affect the risk for H-I-V. The amount of virus in the blood did affect the risk for H-I-V.
The scientists decided to do further research to confirm that finding. So they studied more than four-hundred male and female couples in Uganda. In each of the couples, only one person had H-I-V. Some of those infected had higher levels of H-I-V in their blood than others did. Researchers studied the men and women for more than two years. The study showed that those who had fewer than one-thousand-five-hundred copies of the virus for every milliliter of blood did not pass H-I-V to their sexual partners.Most industrial countries have drugs that reduce the amount of H-I-V in the blood. But in Uganda, H-I-V treatment programs are very limited, although the rate of H-I-V infection is high.
Along with viral levels, the researchers also examined several other important risks for H-I-V infection. The research suggested that men who had been circumcised had a sharply lower chance of getting the virus. Circumcision is a medical operation in which loose skin on the top of a man's penis is removed.
Doctors explained that the extra skin in uncircumcised men could tear during sex, making it easier for the virus to enter the body. But doctors say circumcision does not give men complete protection against H-I-V.Experts say the Ugandan study may lead to new treatments to prevent the spread of H-I-V. But the study has caused criticism about the way AIDS research is carried out.
Marcia Angell is the editor of the New England Journal of Medicine, the magazine that published the study. Doctor Angell says the H-I-V-infected people in the study should have been offered anti-viral drugs that are given in industrial countries.
And she says the researchers should have told the uninfected people that their partners had the virus. She and other people fear that AIDS research is carried out unfairly in poor countries.
Thomas Quinn led the study in Uganda. He says there were no anti-viral drugs in Uganda when the study first began in Nineteen-Ninety-Four. And he says researchers urged the infected people in the study to tell their partners.
((MUSIC BRIDGE))Last month, scientists announced that they recorded the first detailed maps of the development of a child's brain between the ages of three and fifteen. Scientists at the University of California at Los Angeles School of Medicine led the group of scientists. The study appeared in the magazine "Nature." The researchers say their study provides new information about what areas of the brain are used in learning at different ages.The scientists at the University of California invented a process that let them map brain growth in greater detail than ever before. They used a machine called an M-R-I to take a picture of the brain of each child in the study. Using a computer the scientists identified millions of areas of each brain. They took more pictures of each child's brain during the four-year study. Then they mapped the changes in position as the brain developed.
The scientists mainly observed growth in the area of complex nerve tissue called the corpus callosom. This area sends information between the two halves of the brain. They say they found that a child's brain experiences two main periods of growth. The first takes place between the ages of three and six. The greatest growth appears in an area of the corpus callosom in the front of the brain. This area is involved in learning new skills, planning and organizing new actions and working on an activity.The second period of brain growth takes place in the middle and back areas of the corpus callosom from age six to twelve. The most growth was in the areas of a child's brain involved in language skills and understanding relations in space. The scientists say it is during these quick growth periods that the brain is best able to learn.
Scientists say the brain overproduces some cells when it grows. The new cells organize into networks based on the connections that are used in mental or physical activity. Cells and pathways used often form strong permanent connections. Those used least die out as the brain returns to its normal size.Scientists have known that such periods of growth and shrinkage happen before birth and in very early childhood. And, they knew that the brain network connections continued to change until about the age of five. But this study and two similar studies released late last year are the first to suggest the process continues to adulthood.
The scientists say their study may explain why the ability to learn new languages generally decreases after the age of twelve. And, it could explain why people whose brains become damaged as adults have difficult regaining some skills.
((MUSIC BRIDGE))Physical changes, such as gray hair and small lines on the face, appear as we grow older. Now, American scientists say such changes may result partly from changes in our genetic material. They say these genetic mutations increase over time as the cell-division process in our bodies begins to break down.
Researchers from the Scripps Research Institute in La Jolla, (la-HOY-ah) California, reported the findings in the publication Science. The researchers examined cells from four groups of people: normal children, adults, very old people and children with a genetic condition called progeria (proh-JIHR-ee-uh).
Progeria causes the body to grow older at an extremely fast rate. The researchers used a new technology to examine more than six-thousand genes at once. They could see which genes were active among people in each age group.They found that most of the genes kept the same level of activity in youth, middle age and old age. However, the researchers identified sixty-one genes that speeded up or slowed down with age.
Richard Lerner of the Scripps Institute helped organize the study. Mr. Lerner says one-fourth of the sixty-one genes are what he calls quality control genes. He says they are supposed to prevent cells from dividing if there are mistakes in the genetic material. If the quality control genes work, then the genetic mutations are stopped immediately.
But sometimes the cells with genetic mutations produce new cells with the same mistakes, or worse one. He says the increasing number of genetic mistakes in the cell-division process may cause signs of aging.
The researchers believe some of the sixty-one genes might be linked to diseases such as Alzheimer's Disease and arthritis.
This SCIENCE IN THE NEWS program was written by Cynthia Kirk, Linda Burchill and George Grow. This is Bob Doughty.And this is Sarah Long. Join us again next week for more news about science in Special English on the Voice of America.