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BMJ 1996; 313 doi: (Published 31 August 1996) Cite this as: BMJ 1996;313:568

Many transplant surgeons believe that the only way to overcome the shortage of donor organs is to use animals, and at least six biotechnology firms in the United States are now breeding genetically modified pigs in specific pathogen free colonies (Science 1996;273:746-7). In addition to the immunological problems of xenotransplantation the researchers have to deal with the threat of viruses that are often capable of causing severe disease when infecting a novel species. The potential financial rewards for success are, however, enormous.

Having demonised smoking, the medical profession should not abandon attempts to understand its effects on health: many associations are still puzzling. An example appears in the “British Journal of Obstetrics and Gynaecology” (1996;103:800-5). A survey of 4111 Danish women having their first babies found that the dose-response relation between smoking and preterm birth held true only in those women who had a caffeine intake above 400 mg a day. No association was found between preterm birth and smoking in women who drank little or no coffee.

And still on smoking: research using positron emission tomography has produced some dramatic images of the brain showing that smoking reduces the activity of monoamine oxidase B by about 40% (American Journal of Psychiatry 1996;153:973). The ingredient of the smoke responsible …

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