THE EFFECT OF CRITICAL DOSAGES OF GAMMA IRRADIATION UPON THE CAPACITY OF THE PITUITARY GLAND OF BUFO TO SECRETE THYROTROPHIC HORMONE

摘要

Pituitary glands of recently metamorphosed donor toads which had been subjected to gamma irradiation in dosages varying from 5,000 r to 60,000 r were dissected out and transplanted into immature host tadpoles that were killed at the end of 20 days. Their output of thyrotrophic hormone was measured by the activity of the host thyroid glands as indicated by hind limb growth and the tendency to shedding of the cubicula larval teeth.nGamma irradiation up to and including 30,000 r did not reduce the capacity of the pituitary transplant to induce a tendency toward metamorphosis during the 20 days of the experiment. From this point on the successively higher exposures caused progressive loss and capacity to secrete thyrotrophic hormone until at 60,000 r the influence of the thyroid gland upon hind limb growth and shedding of cubicula teeth ceased.