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Show Transplants becoming fairly routine medical procedure By HAROLD F. SPALTER, M.D. Secretary Scientific Advisory Panel Research to Prevent Blindness Organ transplantation has become an almost routine medical procedure. Hearts and kidneys are transplanted every day, as are corneas for the eyes. Neurobiologist Raymond D. Lund, Ph.D., of the University of Pittsburgh, is experimenting experi-menting with the restoration of vision vi-sion through the transplantation of retinal tissue. "What one would like to do is find new ways of recreating those damaged bits of the brain, the damaged circuits, and try to get that retina to connect back again with the brain," said Dr. Lund. According to Research to Prevent Blindness (RPB), several research laboratories are exploring approaches ap-proaches to correct damage to the retina and optic nerve. In one animal study, a bit of retinal tissue from an embryo is inserted into the damaged retina. The goal is to determine de-termine whether the new tissue will integrate normally into the neural circuits of the host eye. A second approach uses a bridge between the eye and the brain. That "bridge," a piece of the sciatic nerve from the leg, seems to provide pro-vide a pathway that encourages the growth of nerve fibers toward the brain in animal experiments. A third strategy, pursued by Dr. Lund, involves transplanting retinal tissue from an immature animal directly to the surface of the brain. "We find that the eye will make the appropriate connections and can actually ac-tually function in a sensible manner," he said. Shining light on the implanted retina was the first test of the nerve connections. When the pupil of the host's normal eye contracted, it suggested that the transplant was connected to the appropriate part of the brain. It was also found that the animal, a laboratory rat, reacted by attempting to avoid the light received receiv-ed through the implanted retina. A third behavioral test showed that animals could use information delivered through the transplant to leam to respond in an appropriate way to a particular experimental situation. The first brain tissue transplants among humans have demonstrated that immature dopamine manufacturing manufac-turing cells can be transplanted into the brain in an effort to treat Parkinson's Parkin-son's disease. The retina tissue transplant is much more complicated. Yet, Dr. Lund is optimistic: "I hope that one can follow this line of study, and eventually find some way of doing something about recreating damaged damag-ed circuits in the diseased retina, or in the damaged visual system at large." |