MITOSIS-STIMULATING ACTIVITY OF THE PITUITARY GROWTH HORMONE UPON AMPHIBIAN TISSUES AS MODIFIED UNDER THE INFLUENCES OF THIOUREA TREATMENT AND DENERVATION

Abstract

The activity of the pituitary growth hormone as a stimulant of the mitosis in tissues of the bull-frog tadpole and the adult newt was examined under the condition of thiourea treatment or in the absence of nervous influence in the limb. In the case of bull-frog tadpole, temporal mitosis-stimulating effect of the hormone took place with no bearing on the functional alteration of the thyroid which resulted by the concomitant thyrotropic hormone in this preparation. In some cases, the epidermal cells of the individuals which received the treatment of 0.05 per cent thiourea solution did not fully respond to the growth hormone as in the case of the normal individuals.Transection of the third, fourth and fifth spinal nerves of the adult newt caused a tendency of decrease of the mitotic rate in the regenerating limb. When growth hormone was administered to such denervated animals, the epidermal cells of the denervated limb did not respond by significant increase of the mitotic rate, while in intact control side of the limb, mitotic increase resulted in considerable measure.