282 



HYPOPHYSIS AND GONADOTROPHIC HORMONES 



autopsy 3 days to 10 months later the hy- 

 pophyses appeared normal and the vas- 

 cularity of the anterior lobes was unim- 

 paired, as shown by perfusion with carmine 

 gelatin. These early findings have been sub- 

 stantiated by Harris and Johnson (1950), 

 who made a suprasellar transection of the 

 stalk in a large male monkey. This animal 

 continued to ejaculate, and at the time of 

 autopsy 89 days later the reproductive or- 

 gans were normal in size and appearance. 

 At autopsy the pars distalis appeared well 

 vasculated and showed no abnormality in 

 size or color. It was demonstrated that 

 vascular continuity between the median 

 eminence and the adenohypophysis had 

 been re-established. From these particular 

 observations one can deduce only that the 

 severance of the neural connections to the 

 hypothalamus are not important for the 

 continuance of adenohypophyseal activity. 

 Disturbance of posterior lobe functions was 

 not observed ; this probably is accounted for 

 by the fact that sufficient terminations of 

 neurosecretory fibers exist proximal to the 

 cut to sustain neurohypophyseal functions. 

 As far as the guinea pig and rat are con- 

 cerned, the widest possible divergence in 

 results has been reported. In female stalk- 

 sectioned guinea pigs Dempsey (1939) and 

 Leininger and Ranson (1943) observed nor- 

 mal, lengthened, or absent estrous cycles. 

 Tang and Patton (1951) severed the stalk 

 in male guinea pigs and observed no gonadal 

 atrophy. Their animals were maintained for 

 27 to 75 days, and although the portal ves- 

 sels could have regenerated postoperatively, 

 no verification of this was found on histo- 

 logic examination of the region. Equally 

 variable responses have been described in 

 stalk-sectioned rats by Dempsey and Uotila 

 (1940) and Dempsey and Searles (1943). 

 They ascribed the abnormal cycles in such 

 operated animals to operative trauma to the 

 anterior pituitary. Using a parapharyngeal 

 approach for sectioning the stalk in male 

 and female rats, Barrnett and Greep (1951) 

 and (Ireep and Barrnett (1951) found a 

 very high incidence of severe gonadal atro- 

 phy along with generalized evidence of i)an- 

 hypopituitarism. These symptoms of an- 

 terior lobe dysfunction were consonant with 

 the extensive infarction and necrosis of the 

 pars distalis observed regularly following 



the operation. They felt that the degree of 

 gonadal dysfunction was relatable to the 

 extent of damage to the blood supply of the 

 pars distalis. The pituitaries showed no 

 capacity for recovery, and there was no re- 

 generation of the portal vessels as deter- 

 mined in specimens injected with India ink 

 and studied in serial sections of the appro- 

 priate areas. Years before, Houssay and 

 Giusti (1930) and Lascano-Gonzalez (1935) 

 had reported on similar infarctions in toads 

 following severance of the vessels to the 

 pars distalis. 



Much recent evidence has revealed that 

 vascular infarction, necrosis, and dysfunc- 

 tion of the pars distalis are consequences of 

 procedures which destroy the portal vessels. 

 Daniel and Prichard (1956) studied the de- 

 gree and localization of vascular lesions in 

 the pars distalis of rats following the appli- 

 cation of a fine cautery to all or a portion 

 of the long hypophyseal portal vessels which 

 pass down the ventral aspect of the stalk. 

 Regions of the anterior lobe supplied by 

 short portal vessels emanating from the 

 lower portion of the neural stalk were un- 

 damaged. In an extension of their study of 

 the vascular supply to the pituitary, Daniel 

 and Prichard (1957a, b) observed in sheep 

 that severing the stalk produced extensive 

 necrosis of the anterior pituitary; the con- 

 dition of the pituitary-dependent endocrine 

 organs was not reported. The extent of 

 damage to the pars distalis w^as remarkably 

 similar to that seen in human cases of 

 postpartum pituitary infarction. 



Harris (1949) suggested that the discrep- 

 ancies in findings following sectioning of the 

 stalk might be reconciled by a study of the 

 extent of regeneration of the portal vessels. 

 Using a transtemporal approach, he sec- 

 tioned the stalk in a series of rats, killed 

 them at close intervals, and injected the 

 vessels. He demonstrated that the por- 

 tal vessels unquestionably regenerated in 

 ''many cases" and that the regeneration was 

 underway by 24 to 48 hours. In a follow-up 

 study Harris (1950) inserted between the 

 severed ends of the stalk an impervious 

 l)late of varying composition. Results were 

 judged by the effect on the estrous cycle. 

 He concluded that the regeneration of por- 

 tal vessels correlated with the ability of the 

 pai's distalis to sustain cyclic gonadal func- 



