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SCIENCE

Notebook

Monday, December 13, 2004; Page A08

Bonobo Chimps Face Extinction

A species of pygmy chimpanzees known for using sex to manage conflict faces the possibility of going extinct, say World Wildlife Fund researchers who have been studying them in the war-torn Democratic Republic of Congo.

Bonobos, which are perhaps humans' closest relative and live only in Congo, were once believed to number 50,000. But a survey of Congo's 90,000-square-mile Salonga National Park conducted over the past year by the World Wildlife Fund, along with the Congolese Institute for Nature Conservation and the Wildlife Conservation Society, suggests the wild bonobo population may have dwindled to 10,000.

The park is a protected area the size of the Netherlands. An analysis of one-third of the park revealed no bonobos and showed nests in just a quarter of the surveyed area. There was ample evidence of poaching and human encroachment in the park.

Bonobos, which were first identified as a species in 1929, live in matriarchal societies that prize cooperation and resolve conflicts through sex, a behavior not found in other primates. Hunters target them for meat that they eat or sell on the bush meat market.

"The world could soon lose the primate species that shares the greatest genetic connection to humans. Bonobos are fascinating creatures that are little understood," said Richard Carroll, a primatologist who directs the fund's Central Africa program. "If humans allow our closest relatives to go extinct, we have failed as a species."

-- Juliet Eilperin

Study Links Defect, Depression

A genetic defect that lowers serotonin levels could increase the risk of depression and also explain why some depressed patients fail to respond to drug treatments, researchers said last week.

The defect was found in more than 10 percent of people with major depression, the study found, including several patients with a family history of mental disorders or suicidal behavior. Patients with the gene defect did not respond to antidepressants known as selective serotonin reuptake inhibitors, or responded only when drugs were prescribed at the highest doses.

"It points the way to predicting treatment response," said Thomas Insel, director of the National Institute of Mental Health, as he explained how the defect could tip doctors off about which patients would respond to drugs, in the same way that doctors treating other medical disorders can screen patients for appropriate therapy.

Only a small number of patients in a control group of healthy adults had the genetic defect. All had symptoms of anxiety, depression or other psychiatric problems, suggesting that the defect was increasing their vulnerability to the disorders.

The gene influenced serotonin through an enzyme called tryptophan hydroxylase-2. The defect caused as much as an 80 percent reduction in serotonin levels in cell cultures, according to Marc Caron and other researchers at Duke University who published the study last week in the journal Neuron. The scientists said that the finding could eventually be used to predict which people are genetically predisposed to depression.

-- Shankar Vedantam

Laptop Use May Affect Fertility

Laptop computers may cause young men to lose some ability to produce sperm when the machines are placed for long periods on their laps. The potential loss of fertility comes from an increase in the temperature of the scrotum, which has been associated with decreased ability to produce sperm.

In a study of 29 healthy men ages 21 to 35, researchers at the State University of New York at Stony Brook found that one hour of laptop use on the lap caused an increase of 4 to 5 degrees in scrotal temperature. Lead researcher Yefim Sheynkin said that previous studies found that an increase in temperature of that magnitude can lead to significant reductions in sperm production.

Sheynkin said researchers do not know how often and for how long a man has to use his laptop to produce the effect. But he said that long-term lap use of portable computers "may cause irreversible or partially reversible changes in male reproductive function."

The study, published in the journal Human Reproduction, said that laptops can reach internal operating temperatures of more than 150 degrees. When men use the machines on their laps, they generally press their thighs together, which also increases the temperature inside the scrotum.

Sheynkin said his group was not yet able to determine what period of time constituted safe use. But he said that after 15 minutes of computer use on the lap, the scrotum temperatures increased enough to have a possible effect on the creation of sperm.

-- Marc Kaufman


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