discussio;ns 



Chairman : Frederick Hisaw 



Dr. William F. Ganong : I asked previously that I be excused from the discussion until 

 Mr. Hammond's paper had been given because my experience has not included any 

 work related to avian ovulation. From the point of view of the neuroendocrinologist, 

 there is one point that might be made relative to Dr. Nalbandov's paper. I appreciate 

 the fact that he is not yet ready to extend his hypothesis to mammals, but there are 

 situations in the rat in which there is a good deal of FSH secretion, and still ovulation 

 can be brought about. There are a number of reports, the most recent being that of 

 Van Dyke, Simpson and co-workers (Proc. Soc. Exp. Biol, and Med. 95, 1, 1957), 

 of persistent estrus following anterior hypothalamic lesions. The ovaries of these 



SITE OF HYPOTHALAMIC LESIONS IN 7 EWES WITH CYCLIC 

 OVARIES BUT ABSENT HEAT PERIODS 



INCLUSIVE AREA 

 DESTROYED BY LESIONS 



AREA COMMON TO 

 ALL LESIONS 



Fig. 1 . Reconstruction of lesions on midsagittal section of the hypothalamus. MI, massa 

 intermedia; MB, mammillary body; OC, optic chiasm; PIT, pituitary. 



animals contain many follicles and the uteri are enlarged, so presumably a high 

 level of FSH secretion is present continuously. Injection of purified LH leads to 

 prompt ovulation of many of the ovarian follicles. 



Mr. Hammond has raised a number of questions about the interrelations in the 

 sheep and the cow between the mechanisms responsible for the production of heat 

 and those responsible for ovulation. Certainly, there seems to be little doubt that heat 

 and ovulation can be separated by appropriate brain lesions in experimental animals. 



Dr. Clegg and I have been interested in the role of the hypothalamus in the regulation 

 of the sexual cycle of the sheep. We have now examined the brains of 39 ewes in which 

 localized destruction of various parts of the hypothalamus has been produced stereo- 

 taxically (Clegg, M. T., J. A. Santolucito, J. D. Smith and W. F. Ganong, Endocrinology 

 62, 790, 1958). Lesions were made during the breeding season in all these animals. 

 Twenty-two unoperated animals served as controls. We have observed an absence of 

 heat periods after production of the lesions in 22 of the 39 operated animals. Five of 

 these ewes were killed after the normal controls entered the anestrus season, so it was 

 impossible to say whether or not pituitary stimulation of the ovaries had been 

 inhibited. The ovaries of the remaining 17 were examined while the normal control 

 animals were still cycling regularly. Nine of them showed acyclic ovaries, i.e. corpora 

 lutea were absent and all ovarian follicles were small. In eight ewes, corpora lutea 

 and/or large ovarian follicles were present. Since regression of the corpus luteum is 

 normally complete a day or two after the next heat, the presence of a corpus 

 luteum indicates that ovulation has occurred in the past three weeks. The possibility 



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