Follicular Development, Ovular Maturation, Ovulation in Ovarian Tissue 33 

 SUMMARY AND CONCLUSIONS 



Transfers of immature rat ovarian tissue to tlie anterior chamber of the eyes 

 of immature male recipient rats of a different strain produced vascularized, 

 growing grafts in 84 % of trials. Most of the antrum-containing follicles of 

 these grafts degenerate, but new ones grow from surviving primordial 

 follicles within 4 days following transplantation. One to 4 new follicles begin 

 to grow each day, and an average of 6 mature within 4 days. The number of 

 follicles that appear is independent of extrinsic gonadotropin injections, but 

 is dependent on the intrinsic rise of gonadotropin level following castration 

 of the host animal. 



When treated with pregnant mare's serum gonadotropin, the follicles 

 increase in volume at about the same rate that has been reported for follicles 

 in the mature ovary in situ, while in untreated grafts, follicular growth lags. 

 Following the injection of human chorionic gonadotropin, the follicles in 

 transplants do not grow so rapidly or become so large as those developing 

 in ovaries in situ, and ovulation is rare. However, meiotic changes in the 

 ovum's nucleus, and cumulus maturation of these ova, seem to progress at 

 the normal rate despite their smaller volume. Only 4.5% of ova removed 

 from follicles that seemed to be maturing proved to be fertile. This is only 

 one-tenth the fertility rate expected from previous experiments on follicular 

 ova obtained from mature ovaries in situ. Ovulation occurred in 6 % of the 

 grafted ovaries. 



Interspecies transplants of ovarian tissue from rabbit to rat, from rat to 

 rabbit, and from human to rat, rabbit or guinea pig, all failed to produce 

 normal ova despite extensive and varied treatments aimed at reducing the 

 antigenic response of the host. 



From an immunologic point of view it is interesting that in these acute 

 experiments, ova can be brought to maturity despite the fact that these 

 intraspecies grafts invariably degenerate a short time later. It is felt that 

 inadequate blood supply, rather than antigenicity, may be the cause for the 

 failure of rapid growth following the injection of chorionic gonadotropin. 

 Slow growth may in turn be responsible for the failure of ovulation, and still 

 more remotely may decrease the fertility of these ova. Further advances in 

 solving this problem will depend on better immunologic control in the 

 recipient host, so that transplants may grow long enough to attain a normal 

 blood supply before ovum maturation is attempted. 



Acknowledgments — This investigation was supported in part by PHS 

 Research Grant RG 4470 from the National Institutes of Health, Public 

 Health Service, and in part by the generosity of Mrs. Lilian Howell. 



