Types of xenotransplants _ the transplanting of living animal organs or cells _ experiments currently being researched:
_Diacrin Inc. has implanted neuronal cells from pig fetuses into 24 Parkinson’s and Huntington’s disease patients. The cells may perform like human fetal cell implants, which in rare experiments have signaled brain improvement.
_Cytotherapeutics Inc. has implanted cow adrenal cells into the spinal cords of 36 dying cancer patients with untreatable pain. The cells make substances that block pain signals. Studies of about 100 patients are being prepared.
_Neocrin Inc. encapsulates pig pancreas cells to avoid the immune system while stimulating insulin production in diabetes patients. It plans to test 50 patients.
_Numerous scientists are pursuing pig livers or liver cells for liver failure patients. Circe Biomedical ran the blood of 54 patients through a pig liver outside the body as a ``bridge″ to keep them alive pending human transplant or their own liver’s recovery.
_One AIDS patient received an implant of baboon bone marrow that didn’t appear to last longer than 13 days, but future attempts are planned.
Several dozen attempts at transplanting entire animal organs into people, dating back to 1905, have failed to keep the patient alive for more than a few days. But scientists are developing genetically engineered animal organs that promise to resist human immune attack, with new trials predicted within a few years.