Excess growth in tadpoles after transplantation of the adenohypophysis.

Abstract

The primordium of the adenohypophysis was transplanted to the animal's own tail in frog (Rana pipiens) embryos. The growth of these animals was compared under standardized conditions with that of hypophysectomized, thyroidectomized and normal (operated and unoperated) controls. Growth in hypophysectomized animals was found to be retarded as compared to normals from the earliest feeding stages onward. Graft pituitaries were found to repair this growth deficit at all stages. At later tadpole stages a definite excess of growth rate over normals occurred in animals bearing displaced pituitaries. Thyroidectomized animals grew as normals in premetamorphic stages. Later they exceeded normals and, lacking metamorphosis, eventually reached giant size. Pituitary transplant animals also grew rapidly in postmetamorphic stages and attained giant size. An inhibitory control by the brain over the production of pituitary hormone(s) stimulating growth in the tadpole is postulated.