The scientists then studied how these chemical analogues influenced eating behavior in normal and genetically obese mice. Melanocortin analogues that bound to melanocortin receptors and activated hypothalamic neurons suppressed food consumption in both normal and obese mice. In contrast, analogues that mimicked the agouti protein blocked melanocortin receptors and induced overeating in both groups of mice. By uncovering more details of these metabolic and neural pathways, scientists hope to devise strategies for treating or preventing obesity. Only one of the many experimental vaccines against AIDS has provided consistent and effective protection in animals.
Researchers disagree about whether a similar vaccine is appropriate for human use.
But other scientists have found that the vaccine can cause an AIDS-like disease in newborn monkeys. To examine the possibility that a vaccinated mother might infect her unborn or newborn baby, the New England investigators immunized four monkeys with the attenuated vaccine during the second trimester of pregnancy. Their four infants were delivered by cesarean section, and none were infected. To simulate exposure to the virus vaccine during vaginal birth, the researchers orally administered three different amounts of virus vaccine to 18 newborn monkeys. Only two, who had received doses much higher than those used for protective immunization, became infected.