A unit was constructed that consisted of a core of hollow fibers through which low-molecular-weight substances, such as glucose and insulin, could pass freely but were impermeable to high-molecular-weight proteins, such as antibodies. Islets of Langerhans from normal rats were planted in the space surrounding the fibers, and either blood or nutrient medium was circulated through the fibers themselves. In experiments with animals, the units were attached to the vascular system of diabetic rats and monkeys. Blood glucose concentrations in the rats were reduced to nondiabetic levels within one hour and were maintained for the duration of the experiments. In monkeys the blood glucose level declined from 210 mg./100 ml. to 90 mg./100 ml. in four hours and insulin in the serum rose to 93 μU./ml. in one-half hour. Also, we have found that islets from monkeys cultivated in the artificial endocrine pancreas (AEP) continue to release insulin into circulating tissue culture medium for over eight months.

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