Hypocalcemia and motor neuron degeneration in paraphysectomized frogs.

The paraphysis has been studied extensively but its function is unknown. Surgical removal of the paraphysis in the bullfrog (Rana catesbeiana) resulted in hypocalcemia and tetany in 35 frogs, about 40% of those operated upon. One or two days after the onset of tetany (about 8 days postoperative), progressive weakness was observed, beginning in the hind limbs. The caudal half of the spinal cord showed a green discoloration in afflicted frogs and histologically motor neurons in the lumbar spinal cord were swollen, indented with vacuoles, and had reduced processes. The paraphysis appears to play a role in calcium regulation in the bullfrog; the motor neuron degenerative changes observed may be secondary to the altered calcium metabolism.