Abstract
Burch has presented evidence to show that the physiological differentiation of both the anterior and the intermediate lobes of the pituitary requires the contact of the epithelial hypophysis with nervous tissue, specifically the floor of the infundibulum. 1 , 2 In experimental embryos of Hyla regilla, contact of hypophysis with infundibulum was prevented by early translocation of the infundibular anlage to a position in the hind brain. Such embryos developed into silvery-white tadpoles which failed to metamorphose. The “albinism” was shown to be caused by a lack of secretion of the pars intermedia, whereas the failure to metamorphose was attributed to lack of thyrotropic principle of the anterior lobe. Histological examination showed no evidence of differentiation in the hypophysis, a mass of deeply staining material occupying its normal position at the tip of the notochord, yet some distance away from the transplanted infundibulum. It was suggested by Burch that the infundibulum acts as an organizer upon the epithelial hypophysis.
I undertook experiments upon a urodele, Triturus torosus, to confirm Burch's findings. Using a method described earlier, 3 , 4 gelatin was injected into 2 series of embryos in early tail-bud stage, namely, into the cavities of the brain of one series and into the foregut of the other. In the former series the ventricles of the brain, including the infundibular recess, were inordinately distended. In several instances the epithelial hypophysis failed to reach the floor of the infundibulum in its migration inward from the stomodeum, probably because of pressure exerted by the gelatin within the brain. These tadpoles exhibited without exception the syndrome of “albinism.” The melanin in both epidermal and dermal melanophores was highly concentrated, whereas the pigment within the xantholeucophores was markedly dispersed.
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