Regeneration of the forelimb in adult hypophysectomized Notophthalmus (Diemictylus) viridescens given embryonic or adult chicken anterior pituitary extract.

Abstract

AbstractIn absence of the anterior pituitary gland, limb and tail regeneration does not occur in the adult newt Notophthalmus (Diemictylus) viridescens. Sixty‐five adult newts were included in this work which was designed to test to what degree a hypophysectomized newt can regenerate its forelimb when given daily injections of fresh adult or stored (−20° C)‐thawed embryonic or adult chicken anterior pituitary gland extract. Injections were begun seven days after hypophysectomy (to minimize further the titres of residual circulatory hormones) and concomitant amputation. The results are based on three experimental, one control and one sham series.In 40 out of 45 cases in Experiments C, D, and E, limb regeneration ensued for 25–30 days post‐amputation (until fixation). However, in the Experiment E newts, which were given embryonic chick pituitary extract, the regenerates were less advanced than those seen in the animals of Experiments C and D, given adult chicken pituitary extracts. Possible explanations for the differences in results are discussed.The results show that forelimb regeneration and survival in our hypophysectomized animals were due to extracts of embryonic or adult chicken anterior pituitary glands; presumably, these extracts contained the essential hormones. On the basis of our newt bio‐test system, 15–18 day chick embryo and adult chicken anterior pituitary extracts (hormones) are not species specific. Freezing and storage of extracts at −20° C for up to three months before thawing and use apparently does not appreciably affect their hormonal activity.