HYPOPHYSECTOMY AND EARLY DEVELOPMENT 53I 



DISCUSSION : 



The hypophyela is the anlage of the para anterior, the pars intermedia, and the pars 

 tuheralis of the adult pituitary gland. The gland is derived entirely from ectoderm, but 

 these portions are derived from head rather than brain ectoderm. Eemoval of this ectoderm 

 (epithelial hypophysis) after its ingrowth has begun seems to prevent regeneration of the 

 same type of tissue so that the relationship of the pars intermedia to the pigmentary sys- 

 tem is clearly indicated. Such embryos should survive for many weeks. 



The method of transplantation might be super-imposed upon this procedure of fextirpa- 

 tion. The host hypophysis might be transplanted in toto (if so removed) to the flank or 

 tall-bud region of the same embryo, to determine whether It could support the pigmentary 

 system although separated from the Infundibular portion of the pituitary. This double- 

 treatment of a single embryo is rather drastic, and it is not always possible to remove 

 the hypophysis Intact. The initial attempts might therefore be a direct transplantation 

 of an hypophysis excised from another Individual, after removal of the original host 

 anlage. 



Atwell and Holley (1956) have shown that if the epithelial hypophysis of Eana 

 sylvatlca is removed at the tall bud stage, some of those which became silvery would, 

 nevertheless, metamorphose. The thyroids, gonads, and adrenals of such forms showed no ef- 

 fect of hypophysectoiny. The silvery tadpoles which achieved metamorphosis lacked the pars 

 intermedia but possessed sufficient of the anterior lobe to stimulate the normal thyroid 

 to carry the animals through the critical period of metamorphosis. 



BEFERENCES : 



Allen, B. M., 1929 - "The Influence of the thyroid gland and hypophysis upon growth and 

 development of Amphibian larvae." Quart. Bev. Biol. l+:325. 



Atwell, W. J., 193**^ - "On the metamorphosis of silvery tadpoles of Bana sylvatlca." Anat. 

 Bee. 58: suppl. h8, 



Atwell, W. J. & E. Holley, I956 - "Extirpation of the pars intermedia of the hypophysis In 

 the young amphibian with subsequent silvery condition and metamorphosis." Jour. Exp. 

 Zool. 75:25. 



Blount, E. F., 1955 - "Total growth and body proportions as influenced by pituitary rudi- 

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Greenwood, A. W., 192^*- - "The growth rate in hypophysectomized salamander larvae." Brit. 

 Jour. Exp. Biol. 2:75. 



Hogben, L. T., 1924 - "The Pigmentary Effector System." Oliver & Boyd, Edinburgh. 



Klatt, B., 1955 - "Weitere Versuche ( gypophysesextlrpatlon und Implantatlonen) an Triton- 

 larven." Arch. f. Ent. mech. 150:79. 



Schotte, 0. E., 1926 - "Bypophysectomle et Metamorphose des Batraciena Urodeles." C. B. 

 Soc. Phys. et Nat. Hist., Geneve. ^5:95. 



Smith, P. E., 1920 - "The Pigmentary, Growth, and Endocrine Disturbances Induced in the 

 Anuran Tadpole by the Early Ablation of the Para Buccalis of the Hypophysis." Am. 

 Anat. Memoires, #11:1. 



Swingle, W. W., I92I - "The relation of the pars intermedia of the hypophysis to pigmenta- 

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