Health Briefs

June 7 , 2002

NEW CORONARY ARTERY STENT REDUCES RISK OF RESTENOSIS
In the past, people with clinically significant narrowing of their main coronary arteries all required open heart surgery and coronary bypass grafting to restore blood flow to the heart. More recently, however, coronary artery stents (expandable mesh tubes that resembles those paper "Chinese handcuffs" you played with when you were a kid) have made it possible for many patients to avoid going under the surgeon's knife. These diminutive vascular conduits are threaded-up through an artery in the leg or arm, and are then passed through the area of blockage in the affected coronary artery. These internal bypass devices have a very high rate of success in restoring coronary artery blood flow but, in 25 to 40 percent of cases, the body responds to the device by gradually narrowing the stented artery again. A number of approaches have been taken to reduce the incidence of restenosis in stented arteries. In this week's New England Journal of Medicine is a study that looked at rapamycin-impregnated stents as a novel way of reducing the restenosis rate. Rapamycin is often used as an anti-rejection medication in transplant patients, as the drug inhibits certain immune cells from dividing and attacking the transplanted organs.

The researchers coated coronary artery stents with rapamycin, and then randomized 238 patients to receive either a rapamycin-coated stent or a non-coated stent. The patients were then followed for at least one year after stenting. The patients who had the rapamycin-coated stents implanted were found to have significantly less restenosis than patients receiving the conventional stents. After being observed for 12 months, fully 27 percent of the patients with conventional stents developed at least a 50 percent reduction in the diameter of the stented artery, while none of the patients with the rapamycin-coated stents experienced a comparable degree of reduction in arterial diameter. Most importantly, 29 percent of the standard-stent group experienced a heart attack, death, or the need for emergent bypass during the 12 month follow-up period, while only 6 percent of the rapamycin-coated stent group experienced any of these severe complications of coronary artery restenosis. This study convincingly demonstrated a dramatic reduction in the most common complication associated with coronary artery stents, and along with other similarly successful interventions, further advances the state of the art of non-surgical coronary artery disease treatment.

POSSIBLE CAUSE OF PARKINSON'S DISEASE IDENTIFIED
Parkinson's Disease (PD), which affects about 1.5 million Americans, is a neurological syndrome that causes tremors, difficulties in starting and stopping movements, a peculiar stiffness of the body, depression and, in some cases, dementia. The area in the brain that is affected by the disease is known as the substantia nigra, and is thought to be an important relay system for nerve cell impulses involved in movement. For reasons that have eluded scientists since it was first described in 1817 by the British physician James Parkinson, dopamine-secreting neurons in this area of the brain die off, causing the symptoms of PD. However, a new study, just reported in Nature Medicine, has identified at least one possible cause of Parkinson's Disease. A brain protein called alpha-synuclein is known to be elevated in the substantia nigra of most patients with PD. In this study, the scientists added alpha-synuclein to healthy substantia nigra neurons growing in a culture dish, and observed that this protein actually appeared to convert the dopamine secreted by substantia nigra neurons into a toxic compound which then, in turn, killed the neurons. Ironically, alpha-synuclein appears to have a protective effect on neurons that do not secrete dopamine in other parts of the brain. Most spontaneous cases PD have long been suspected to arise from exposure to unknown environmental toxins. It is, therefore, especially intriguing that this Nature Medicine study concluded that alpha-synuclein converts dopamine into a neurotoxin by way of oxygen free radicals, which are byproducts of normal metabolism, and the metabolism of numerous drugs and toxins as well. If alpha-synuclein does in fact cause or mediate the onset of PD, this knowledge could serve as a critical starting point for the development of drugs that target this protein, or the free radicals that also appear to be involved. PD might then be prevented in many cases or, at least, more effectively treated than is possible at the present time.

BRIEFLY...
Bioflavanoids are in the news a great deal these days. Antioxidant flavanoids contained in tea and other natural sources are thought to have a variety of beneficial effects, including the elimination of potentially harmful free radicals that have been linked to an increased risk of heart disease and some cancers. The journal Cancer Research is reporting that silibinin, a flavanoid found in the milk thistle plant, is capable of significantly inhibiting the growth of human prostate cancer cells implanted in mice. Silibinin reduced tumor volume in these mice by 53 to 64 percent, and appeared to have virtually no observable toxicity. Human studies using this compound are currently being planned.

A Duke University team has studied pregnancy and birth rates among unmarried teenagers in Texas. They found that conception rates dipped during the summer months, and then dramatically increased again when school started in the fall. Their conclusion, not surprisingly, was that most teens meet their sexual partners at school....

When breast cancers spread, their favorite target is the skeletal system. Traditionally, a nuclear medicine bone scan is utilized to evaluate breast cancer patients for possible spread of their cancer to their bones. The nuclear medicine bone scan has been around for decades, and is very sensitive to any disruption of the bone caused by inflammation, injury or tumors. Unfortunately, arthritis, relatively minor injuries and infections can all cause a positive bone scan result, making this test rather nonspecific as a cancer detection tool. PET scans, on the other hand, are both very sensitive and very specific for tumors. In the Journal of Cancer Research & Clinical Oncology, a new study has compared the two types of scans, and has found PET to be as sensitive as bone scans in detecting metastatic breast cancer lesions in the bone. However, unlike bone scans, PET was also found to be highly specific for metastatic bone tumors. In another words, bone scans picked up even subtle abnormalities in the skeleton, irrespective of whether cancer metastases were present or not. An abnormal PET scan, however, was far more likely to represent a true metastasis of breast cancer to the bone than an abnormal nuclear medicine bone scan.

Dr. Robert A. Wascher