A

AIDS
Efforts to quell the epidemic took three steps forward and one step back this year. The first human trials of a vaccine against African strains of HIV began in Kenya and England. The FDA approved a new anti-HIV drug. And leaders of developing nations, in which 95% of aids cases occur, pledged more funding to fight the economic and social devastation caused by the disease. But South African President Thabo Mbeki sounded a sour note when he openly questioned whether HIV causes aids. That prompted more than 5,000 scientists to sign a declaration decrying the waste of valuable time and resources arguing over a well-established scientific fact. Mbeki reportedly remains unconvinced but has stopped talking about it publicly.

Alzheimer's Disease
Scientists began safety testing the first drug designed to tackle the root cause rather than the symptoms of this brain-addling disease. Patients in the early stages of Alzheimer's were given a gamma secretase inhibitor, a compound that blocks the formation of the sticky plaques that gum up the brain's neural connections. So far, the drug seems to have been well tolerated.

B

Breasts
Back in 1992, NIH scientists were asked by Congress to study the safety of silicone breast implants. The first part of their investigation, completed in November, studied breast-cancer rates in 13,500 women who had breast implants (most of them silicone) and 4,000 who did not. Results: the implant patients showed no added risk for breast cancer when compared with the controls. Researchers warn, however, that further studies are needed to determine whether the implants are linked to other cancers or connective-tissue disorders.

C

Cell Phones
Do they or don't they cause brain cancer? After a handful of studies yo-yoed back and forth on the answer, the Cellular Telephone Industry Association tried to seize control of the uncertainty this summer and, they hoped, pre-empt any future lawsuits. (Noted class-action attorneys have already joined an $800 million suit against Motorola.) The association suggested that cell-phone manufacturers voluntarily disclose radiation levels emitted by each unit's antenna. Meanwhile, those who walk and talk at the same time can take solace; the latest studies find no increased risk of brain tumors. But please note: the studies followed users for only two to three years and were partly funded by an organization of cell-phone manufacturers.

Chromosones
The human genome may have dominated the news last year, but mouse geneticists were busy too. They created an artificial mouse chromosome and, for the first time, showed that it could be passed from parent to offspring. If the same holds true in people, inherited genetic diseases may someday be corrected by injecting parents with man-made chromosomes.

Colon Cancer
Colorectal cancer is the third deadliest cancer in the U.S., and last April the FDA gave the 130,000 people in whom it is diagnosed each year some much needed help. It ruled that Camptosar, in use since 1999 as a second-line treatment, was potent enough in combination with other chemotherapy agents to now be used as a first-line therapy, even in advanced cases.

Corneas
There aren't many treatments for a scarred cornea, the opaque outer layer of the eye, since corneal tissue can't be easily replaced. But it may be possible to grow a new one. Doctors have successfully transplanted tissue from other parts of the eye to reconstruct the cornea and restore sharper sight to a handful of patients.

CPR
In case of a heart attack, standard cardiopulmonary resuscitation (CPR) procedure calls for alternating mouth-to-mouth resuscitation with carefully counted chest compressions. A study of emergency medical technicians demonstrated, however, that chest compressions alone may be enough. Survival rates of heart-attack victims were the same whether they were given CPR or chest compressions alone.

D

Defibrillators
Heart patients may rest easier knowing that the cardiac jump-start that might save their lives is in the next room. Agilent Technologies, based in Palo Alto, Calif., and CVS.com last year launched Heartstream, the first defibrillator available directly to consumers with a doctor's prescription.

Diabetes
It's getting easier for diabetics to keep tabs on the ups and downs of their glucose levels. The first fully automated monitoring device - one press of a button pricks, analyzes blood and provides results - has been approved by the FDA. Still in the works is an infrared system that measures glucose levels by scanning the tongue.

DNA
Want to join the genetic revolution?Fill out a questionnaire and provide a blood sample and you can donate your DNA for genetic-disease research at www.DNA.com. Run by DNA Sciences, the site has drawn 4,500 volunteers so far and is hoping for a total of 100,000 samples.

E

Estrogen
It still soothes hot flashes and protects your bones, but two major studies showed that taking estrogen long after menopause may not benefit the heart. In fact, the potent female hormone may slightly increase the risk of suffering a heart attack in some women. A long-term study is expected to produce a definitive answer sometime during the next five years or so. Until then, women with high cholesterol levels should get plenty of exercise, limit the amount of saturated fat in their diet and listen carefully if their physician suggests taking a cholesterol-lowering drug.

F

FastPack
As if undergoing treatment for prostate cancer weren't bad enough, men usually have to wait up to a week for blood tests to determine whether or not their tumor has returned. In June the FDA approved FastPack, an automated blood analyzer designed by Qualigen of Carlsbad, Calif., that measures in as little as 15 minutes the level of prostate-specific antigen found in a blood sample. The FDA concluded, however, that there weren't enough data to approve FastPack as a screening tool for the general population as well.

Fatty Fish Remember good cholesterol and bad cholesterol? It turns out there are good fats and bad fats too - although all fats still contain nine calories per gram. Health experts are increasingly intrigued by a group of good fats called omega-3 fatty acids, and what's good about them is that they lower the level of triglycerides (one of the bad fats) and decrease the risk of suffering a blood clot. Salmon, sardines and tuna are so full of omega-3 fatty acids that the American Heart Association for the first time recommended that everyone eat two 3-oz. servings of fatty fish each week.

Fiber
Three big studies concluded that a diet rich in fiber - found in whole-grain cereals, fruits and vegetables - won't necessarily protect you against colon cancer. Study participants who consumed as much as 35 g of fiber a day were just as likely to develop precancerous growths in the intestines as those who were addicted to processed food. But fiber still has its benefits: it helps lower blood pressure, moderates cholesterol levels and combats type II (adult-onset) diabetes.

G

Gene Therapy
Programs in several medical centers were either put on hold or severely restricted following the 1999 death of Jesse Gelsinger, 18, the first American known to have died as a direct result of gene therapy, an attempt to replace defective genes with normal ones. Meanwhile, doctors in France successfully used gene therapy to treat four infants suffering from a congenital immune disorder.

Genetically Modified Foods
Millions of bushels of genetically modified corn, approved for animal feed but not for human consumption, turned up in Taco Bell taco shells and other food products. Though most of the food was recalled before it was eaten, the high-tech mix-up increased public skepticism about so-called Frankenfoods. In the meantime, public-health experts still have high hopes for golden rice, a strain that's genetically enriched with a precursor of vitamin A and that could help prevent blindness in hundreds of thousands of children in impoverished countries each year.

Genome

Five years ahead of schedule, scientists announced that they had sequenced the 3.1 billion pairs of biochemical "letters" of human DNA, the coded instructions for building and operating a fully functional human. Fierce rivalry between J. Craig Venter, the prickly head of a private genetics company, and Dr. Francis Collins, leader of a government consortium, fueled the lightning-fast pace.

H

Heart
A powerful new clot-busting drug, tenecteplase, reduced treatment time for heart-attack victims from 90 minutes to just five seconds. Clinical trials showed the drug to be as effective as the standard clot buster t-PA and easier to use since it can be administered in one quick injection instead of an hour-and-a-half infusion. Tenecteplase, which was approved by the FDA last June, is also longer acting and specifically targets blood clots, rather than indiscriminately thinning the blood. Good news for the more than 1.1 million Americans each year who suffer a heart attack.

L

Lung Cancer
Researchers were pleased to find that a diet rich in fruits and veggies reduced the risk - at least in women - of the No. 1 cancer killer in the U.S. Apples, pears, cauliflower and grapefruit were particularly active against the incidence of lung cancer for reasons are that are still unclear (although scientists suspect carotenoids may be powerful anticarcinogens). But the bottom line is that no quantity of cabbages or citrus fruits can outweigh the benefits of quitting smoking.

M

MRI
A new form of noninvasive "black blood" magnetic-resonance-imaging technique allows doctors to detect problem spots in carotid arteries, the aorta and coronary arteries before patients develop symptoms of atherosclerosis or stroke. The high-resolution MRI blacks out blood flow, offering doctors a clear view of the blood vessels and allowing them to precisely measure the thickness of their walls. Though the black-blood technique still needs improvement, doctors hope the technology will eventually identify those at risk of heart attack long before they have one.

N
Nerve TransplantIn a surgical first, Houston doctors transplanted nerves from a living donor to her infant son. To repair torn nerves in eight-month-old Rodrigo Cervantes Corona's left shoulder and arm, doctors took 3 ft. of neural tissue from his mother's legs and tracked it from the right side of his body to his left hand. The transplanted nerves act as a conduit to allow the baby's undamaged right-hand nerves to grow over to his left side. The mother will feel a bit of numbness on each side of her feet for the rest of her life.

P
Parkinson's Disease
In an important step forward for both Parkinson's research and the struggling field of gene therapy, scientists in Chicago used a gene that boosts dopamine production and strengthens brain cells to successfully treat monkeys showing symptoms of the neurodegenerative disorder. By injecting a virus containing the GDNF (glial-derived neurotrophic factor) gene directly into monkeys' brains, scientists stimulated cell growth in areas normally injured by Parkinson's and reduced symptoms of the disease, such as hand tremors. Although success in primates doesn't mean success in humans, researchers hope to start clinical trials in humans within five years.

Polio
Last spring a strain of wild polio virus was unexpectedly discovered in the sewage system of Strasbourg, France. It's likely that the virus, considered extinct in that country, had instead escaped from one of Strasbourg's many biomedical laboratories. Still, the appearance of wild polio in a certified polio-free region undermined World Health Organization plans to eliminate universal vaccination once it declares polio eradicated, which it had hoped to do by 2005. Widespread on five continents, including the Americas, Europe and Asia, through the late 1980s, polio has now been contained mostly to parts of sub­Saharan Africa and the Indian subcontinent.

PPA
After decades of use as a decongestant and a weight-loss drug, a six-year study showed that the amphetamine-like stimulant phenyl-propanolamine (ppa) increases the risk of hemorrhagic stroke, especially in young women. The FDA subsequently deemed it unsafe and asked manufacturers to pull medications containing ppa off pharmacy shelves. ppa has been on the market since the mid-1930s, and consumers take 6 billion doses of it annually, in such products as Alka-Seltzer, Robitussin, Dexatrim and Tavist-D. Though ppa is widely used in many popular cold and diet pills, medications with the safer alternative pseudoephedrine are easy to find.

R

Ritalin
For millions of children who suffer from with attention deficit hyperactivity disorder (adhd), drugs like Ritalin have been a godsend. Yet at the same time there is real concern that the use of Ritalin to curb all manner of fidgety behavior has become too casual and that the drug is actually being abused as a performance booster. A Duke University study suggested that the drug is, in fact, both over- and underprescribed. The Duke team found that 25% of kids with confirmable adhd are not getting the drug, while more than half of kids who are taking the drug should not.

RU-486
It was a long time coming, but finally, 12 years after its debut in France, RU-486 (mifepristone) was approved by the FDA, and the controversial "abortion pill" hit American shores. Did it change our world? Not yet. Abortion foes are campaigning against physicians who prescribe it, and even some doctors point out that an RU-486-induced abortion is expensive (the pills alone cost $240) and not as effective as the surgical procedure. Still, expect the drug to have a growing, if gradual, impact.

S

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.

T

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
ge-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.

X

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.

Z