CHECKUP SCIENTISTS CREATE HUMAN ARTERIES.

Byline: - Staff and Wire Services

By finding a way to keep smooth muscle cells dividing indefinitely, scientists have managed to fashion the first-ever human arteries from nonembryonic tissue in a laboratory.

The hope is that, eventually, these engineered human arteries will be available for routine use in coronary artery bypass surgery.

``This had never been done before. We took a task that was previously thought to be impossible and now put it in the realm of the possible,'' says Chris Counter, co-senior author of a paper appearing in the June 6 issue of EMBO Reports, the journal of the European Molecular Biology Organization.

Dr. Augustus O. Grant, incoming president of the American Heart Association and a professor of medicine at Duke University School of Medicine, says the feat is ``without a doubt'' a big step in heart research.

The majority of coronary artery bypass grafts in the United States use blood vessels that have been harvested from somewhere else on the patient's body, usually from the legs. Every year, some 100,000 people who need small-vessel grafts can't get them because their own supply is limited.

The authors of this study found a way - by inserting a gene called hTERT - to shut off a portion of one of the enzymes involved in the process of cell division. Shutting this down essentially made the cells immortal. Longer-living cells meant the scientists had time to construct their arteries.

The authors estimate that it could take as long as a decade before these arteries are in routine use in operating rooms.

GENES AND BREAST CANCER: A study by USC's Keck School of Medicine suggests that not all breast cancers are caused by hormone exposure over a lifetime. Certain breast cancers may be due to an inherited sensitivity to hormones flooding the body at puberty.

The study looked at 1,811 pairs of female twins where one or both had been stricken with breast cancer. Researchers gathered information on factors thought to be linked to breast cancer risk - age of first menstrual period, age when the first child was born, how many children they had, and age when menopause began.

Among identical twins who both were diagnosed with breast cancer, the sister who began menstruating earlier was more than five times as likely to get breast cancer first. Women who menstruated before age 12 were highly likely to get breast cancer first within the pair.

Researchers suspect that ovarian hormones flooding through the body at puberty might damage breast cells in genetically susceptible women. It's possible that the genes charged with fixing damaged DNA don't work as well in these women or that a genetic error makes cells more sensitive to hormones. The study will provide a launching point to identify the genes involved, researchers said.