Your A to Z Guide to the Year in Medicine

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Stem Cells
With their uncanny ability to morph into any type of cell — from skin to bone and everything in between — stem cells cast a mighty spell on medical researchers who dream of using them to treat a whole range of intractable diseases. But because of religious opposition and fears that embryos — the best source of stem cells — could become a kind of cash crop, U.S. scientists have been largely shut out of this promising field. New NIH guidelines, however, have reversed the earlier ban and now allow federally funded researchers to use embryonic stem cells as long as they are not sold for profit and come from such sources as embryos discarded from in vitro fertility treatments.

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Testosterone
It puts hair on your chest and a rocket in your pocket and is credited — and blamed — for everything from rape to the urge to explore new worlds. Four million men in the U.S. with clinically low levels take testosterone supplements, and lately it's also gained popularity as a kind of youth boost for both men and women. A new topical formulation, marketed as AndroGel, will it easier for legitimate users to take the hormone. AndroGel may also expand its use for medically dubious reasons.

V

Verteporfin
Age-related macular degeneration (amd) afflicts 13 million Americans and in its most severe form, characterized by abnormal growth of blood vessels in the retina, can cause vision loss or blindness. The first treatment approved for amd, verteporfin, can slow or halt the most severe form of the disease. The drug is a photosensitive dye that is activated by a low-intensity laser and triggers a chemical reaction that destroys the troublesome vessels.

Virtual Colonoscopy
Despite Katie Couric's crusade to educate the public about the importance of screening for colon cancer, there are still too many people who resist being tested because of discomfort or cost; an estimated 70% of the population is never screened. A new noninvasive screening technique may offer those most at risk a lifesaving alternative. Dubbed virtual colonoscopy, it uses digital data generated by multiple computer scans to create a high-resolution 3-D image of the intestine, which can then be displayed on a computer screen and visually probed for tell-tale polyps.

W

Walking
We already knew that walking can reduce adult-onset diabetes and coronary heart disease. But researchers at Harvard University have found another good reason to take a hike: to prevent stroke. According to the Harvard Health Letter, even people who had been sedentary for much of their life had a lower stroke risk soon after they started walking regularly. Speed counts though. For the fastest walkers, the risk reduction was an impressive 40%. A leisurely stroll does some good, but the study showed that a brisk pace of three miles per hour or more is the key — even more important than how far you walk.

West Nile Virus
In the second year of a much feared and overpublicized medical crisis, public-health officials in the Northeast intensified their campaign against mosquitoes infected with the West Nile Virus. Spraying programs were launched from Boston to Baltimore, Md., and wildlife pathologists began searching for clues in the carcasses of crows, chickens, chipmunks and even a few bears. Only a handful of human deaths have occurred so far, but scientists are working hard to figure out how the disease spreads. Most of what they've gained is a deeper understanding of mortality among wildlife.

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Xena
No, not the Warrior Princess, but still perhaps a superhero in her own right. Xena is a female piglet cloned from fetal-pig skin cells, and she may prove to be more than the latest addition to the biotech clone farm. Because of similarities between porcine and human organs, the techniques that made Xena may eventually create a supply of genetically modified pig livers that would be acceptable to the human immune system.

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Zinc
Although the conclusions of clinical trials are still split pretty evenly pro and con, a study from the Annals of Internal Medicine suggests that folks who have been popping zinc supplements to ward off colds may be on to something. Zinc seems to reduce the duration of cold symptoms by four days, provided you start taking it in the first 24 to 48 hrs. after symptoms appear and then keep sucking on the lozenges every couple of hours for several days. Don't overdo it though. Too much zinc can lower levels of HDL, the "good"cholesterol.