The hypophysis of Xenopus laevis Daudin larvae after removal of the anterior hypothalamus

Abstract

The region of the brain anterior to the tectum opticum, including the nucleus magnocellularis praeopticus , and other possible sites of anterior hypothalamic centers, has been removed from larvae of Xenopus laevis , the hypophysis being left intact. The larvae, the rate of development of which was somewhat delayed, have been reared for variable periods of time. In the absence of the hypothalamic neurosecretory nuclei the pituitary neural lobe underwent a complete regression and was therefore wholly lacking. In the pituitary distal lobe both acidophilic and thyrotropic cells appeared to be cytologically well-differentiated. After thiouracil administration a clear-cut goitrogenic response was shown by the thyrotropic cells; some acidophilic cells (presumably somatotropic ones) showed normal features, while abnormally large acidophilic granules occurred in certain other specifically located ones (presumably ACTH-secreting cells), indicating some possible cell disturbances. The possibility that the thyrotropic function of the pituitary is, at least in part, independent of the hypothalamus seems further supported by the results obtained in the present experiments. The lack of the neural lobe was accompanied by hypertrophy of the intermediate lobe. Hyperactivity was indicated by the hypertrophy and marked pyroninophilia of both the cytoplasm and nucleoli of its cells. In correlation with this, a higher pigmentation than normal was shown by the operated larvae, in which tightly packed and diffusely pigmented melanophores were seen to occur. The present findings are compared with other available data, and their significance is briefly discussed.