DISCUSSIONS 



Dr. Roland K. Meyer: I shall begin with an analysis of the tissues that compose the wall 

 of the follicle in the bird; the stratum granulosum is involved in the secretion of yolk 

 and perhaps progesterone, the theca interna in the production of estrogen; the smooth 

 muscle elements are contractile. Dr. Nalbandov has used menstruation as a model in 

 describing his concept of the mechanisms involved in ovulation in the bird. I would 

 like to use as a model the myometrium during pregnancy as it develops in preparation 

 for the expulsion of the fetus. 



The development of the myometrium is influenced by both estrogen and progesterone, 

 as produced in early pregnancy by the ovary, later by the placenta. I suggest that the 

 smooth muscle cells in the wall of the follicle are likewise stimulated by estrogen and/or 

 progesterone produced in the adjacent theca interna and/or granulosum. The smooth 

 muscle elements are thus developed in preparation for the expulsion of the ovum which 

 is progressively increasing in size as the yolk is secreted. As in the pregnant uterus, the 

 wall of the follicle is subjected to increasing tension as the ovum increases in size. Just 

 prior to ovulation in the bird, under the inlluence of FSH and small amounts of LH, 

 progesterone is increased causing the release of larger amounts of LH, which causes a 

 further increase in distension of the follicle wall and tension of the smooth muscle. It 

 is postulated, as in the uterus at parturition, that under the influence of estrogen and 

 progesterone the muscle coat has become fully developed and begins to contract as 

 the optimum degree of stretching is reached. 



As a consequence the vessels in the wall of the follicle are compressed and ischemia 

 occurs, especially in the stigma. The stigma disintegrates, and the contracting follicle 

 wall expels the ovum through the opening. 



This concept is based on the assumption that ovulation is the result of an integrated 

 interaction of physical factors which are developed in the tissues of the follicle under 

 the positive influence of hormones. Unlike Dr. Nalbandov's explanation it does not 

 involve any elements of hormonal deprivation, or follicular atresia. 



I have presented these thoughts as elements of a working hypothesis, even though 

 Dr. Nalbandov has stated that intrafollicular pressure and the smooth muscle of the 

 follicle are not considered to be very important factors in ovulation in birds. 

 Dr. Andrew V. Nalbandov: Well, in general, I am in sympathy with what Dr. Meyer 

 has said. It is hard for me to conceive of an ischemia, which would not lead to some 

 mild atresia, if you want to call it that. 



I am grateful for your remarks, and the only thing I can say is that we will continue 

 to work on it and see what come out of it. 



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