They sleep together, eat together, and most people find it impossible to tell them apart. Identical twins who grow up together share just about everything, including their genes. But sometimes only one twin will have health problems when genetics predicts both of them should.

The study of 18 HIV-positive subjects shows that HIV in the brain and central nervous system is genetically different from HIV that lives in the blood and peripheral tissues.

The continent-hopping habits of early primates have long puzzled scientists, and several scenarios have been proposed to explain how the first true members of the group appeared virtually simultaneously on Asia, Europe and North America some 55 million years ago.

Vaccines made with bacteria killed by gamma irradiation, rather than by standard methods of heat or chemical inactivation, may be more effective, say researchers supported by the National Institute of Allergy and Infectious Diseases (NIAID), part of the National Institutes of Health (NIH). Vaccines made from gamma-irradiated bacteria also may not need to be kept cold; an advantage in settings where refrigerating vaccines is impractical or impossible. A report on the research appears in the current issue of the journal Immunity.

Super-intense radiation delivered by a robotic arm eradicated lung tumors in some human patients just 3-4 months after treatment, medical physicist Cihat Ozhasoglu, Ph.D. of the University of Pittsburgh Medical Center will report in early August at the 48th Annual Meeting of the American Association of Physicists in Medicine in Orlando. Although it is too early to determine the technique's long-term effectiveness, Ozhasoglu and his colleagues find promise in this new approach to treat lung cancer and other tumors that move during breathing.

Open-air field trials involving five major food crops grown under carbon-dioxide levels projected for the future are harvesting dramatically less bounty than those raised in earlier greenhouse and other enclosed test conditions – and scientists warn that global food supplies could be at risk without changes in production strategies.

Although Chinese cotton growers were among the first farmers worldwide to plant genetically modified (GM) cotton to resist bollworms, the substantial profits they have reaped for several years by saving on pesticides have now been eroded.