324 HYPOPHYSECTOMY AND EARLY DEVELOPMENT 



2. At weekly intervals alter the operation make draumgs (or take pnoiograpnsj oi the 

 operated and control embryos, side-by-side, to show any 



a. Changes in pigmentation 



b. Differences in rate of development (i. e. , size differences) 

 Remember that these embryos must be fed after the stage #42. 



3. Embryos which show pronounced effects of hypophy sectomy (silvery appearance), 

 stunting, etc. ) should be sectioned (transversely and sagitally) to determine the extent 

 or success of the hypophyseal extirpation. Control embryos of the same age should 

 be sectioned for direct comparison. Note also any variations in the development of 

 the thyroid glands. 



DISCUSSION: 



The hypophysis is the anlage' of the pars anterior, the pars intermedia, and the pars 

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

 these portions are derived from head rather than brain ectoderm. Removal of this ecto- 

 derm (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 

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



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

 The host hypophysis might be transplanted in toto (if so removed) to the flank or tail-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 hypo- 

 physis intact. The initial attempts might therefore be a direct transplantation of an hypo- 

 physis excised from another individual, after removal of the original host anlage'. 



Atwell and Holley (1936) have shown that if the epithelial hypophysis of Rana sylvatica is 

 removed at the tail-bud stage, some of those which became silvery would, nevertheless, 

 metamorphose. The thyroids, gonads, and adrenals of such forms showed no effect of 

 hypophysectomy. 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. 



REFERENCES 



ALLEN, B. M. , 1929 - "The influence of the thyroid gland and hypophysis upon growth and development of Amphibian lan'ae. " 

 Quart. Rev. Biol. 4:325. 



ALLEN, B. M. , 1957 - "The effects of heavy gamma irradiation upon pituitary glands transplanted into hypophysectomized tad- 

 poles of Bufo boreas. " Jour. Exp. Zool. 136:185-200. 



ATWELL, W. J. G E. HOLLEY, 1936 -""Extirpation of the pars intermedia of the hypophysis in the young amphibian with subse- 

 quent silvery condition and metamorphosis. " Jour. Exp. Zool. 73:23. 



BLOUNT, R. F. , 1933 - "Total growth and body proportions ai influenced by pituitary' rudiment implantation and extirpation in 

 Urodele embryos. " Anat. Rec. 5546. 



GREENWOOD, A. W. , 1924 - "The grovrth rate in hypophysectomized salamander lar\'ae. " Brit. Jour. Exp. Biol. 2:75. 



HOCBEN, L. T., 1924- "The Pigmentary Effector System. " Oliver G Boyd, Edinburgh. 



KLATT, B. , 1933 - "Weitere Versuche (Hypophysesextirpotion und Implantationen) an Tritonlarven. " Arch. f. Ent. Mech. 130:79. 



SAXEN, L. , E. SAXEN, S. TOWONEN C K. SALINLNKI. 1957 - "The anterior pituitary and the thyroid function during normal and 

 abnormal development of the frog." Ann. Zool. Soc. Vanomo. 18:1-44. 



SCHOTTE, O. E., 1926 - "Hypophysectomie ct Metamorphose des Batraciens Urodeles. " C. R. Soc. Phys. et Nat. Hist., Geneve. 

 43:95. 



SMITH, P. E. , 1920 - "The Pigmentary. Growth, and Endocrine Disturbances Induced in the Anuran Tadpole by the Early Ablation 

 of the Pars Buccalis of the Hypophysis. " Am. Anat. Memoircs, #11:1. 



SWINGLE, W. W. , 1921 - "The relation of the pars intermedia of the hypophysis to pigmentation changes in Anuran larvae. " 

 Jour. Exp. Zool. 34:119. 



