The next time you hear someone talking about a blood-sucking leech, that person may be referring to the latest breakthrough in medical technology to crawl out of a physician's black bag.

Charles M. Lent, a Utah State University biology researcher, says the worms are making a comeback into the medical field, and researchers are discovering new uses for the creatures, such as treating Parkinson's disease, arthritis, thrombosis and atherosclerosis."Leeching can increase the success of plastic surgery, tissue transplants and surgical re-attachments," Lent said.

The first recorded clinical use of leeches occurred about 2,500 years ago. The practice of leeching patients became popular in the 18th and 19th centuries, when patients were often "leeched" to death. Lent said such notable figures as George Washington and Joseph Stalin were victims of leeching on their death-beds.

The practice of leeching patients lost popularity in the medical field and, until about 10 years ago, the use of leeches was considered folk medicine and no longer a valid treatment.

But after physicians complained that they lacked an adequate medical technology to provide smooth blood circulation following surgery, researchers returned to the leech for help.

The leech bite, which closely resembles the Mer-cedes Benz logo, has proved to be especially effective in the case of tissue transplants or re-attaching tissue. Veins in such tissue are sometimes unable to carry blood back to the heart, resulting in blood accumulation in the surgical area, where the tissue dies due to improper circulation.

The chemicals in leech saliva include an anti-coagulant and local anesthetic, which help restore blood circulation and allow tissue to establish itself at the surgical location.

In addition to restoring blood circulation, Lent said the creatures may be useful in studying and treating Parkinson's disease, a disorder that affects the brain and nervous system.

"This is an important area of research in Utah, where the level of Parkinson's disease appears to be high," Lent said.

Studies have also shown that leech saliva contains enzymes that may disrupt atherosclerotic plaques, the materials that harden arteries and contribute to heart disease.

"If we find out what's going on in the leech, we may be able to understand what's going on in humans," Lent said.