Follicular Development, Ovular Maturation, Ovulation in Ovarian Tissue 25 



and the graft was observed daily with the aid of an 18-power dissecting 

 microscope equipped with an eyepiece micrometer. On the fourth day after 

 the operation the host was castrated and injected with 15 I.U. of pregnant 

 mare's serum gonadotropin (PMS). Fifty-six hours later, 25 I.U. of human 

 chorionic gonadotropin (HCG) was injected, this sequence having been 

 found to cause superovulation in immature rats (12). 



The maturity of ova from the above transplants was evaluated histologically 

 and biologically. The ovarian grafts were recovered by killing the host and 

 dissecting the ovarian tissue away from the iris. The follicles were pierced 

 with a sharp blade and the ova were extruded into saline. Some of the ova 

 were fixed and stained whole under a covershp, others were transferred into 

 the ovarian bursas of recently mated adult female rats of the Sprague-Dawley 

 strain. If such transferred ova were mature they became fertilized, implanted 

 and developed into normal young in the foster mother. Since the donor ova 

 came from a strain of black rats, the donor had black iris pigment, whereas 

 the young native to the foster mother had no iris pigment. 



In some experiments the ovarian grafts were fixed and serially sectioned, 

 and the volume of the larger follicles was calculated. Two diameters were 

 measured at right angles to each other with the eyepiece micrometer and the 

 third diameter was estimated from the number of sections in which the 

 follicle appeared {V= \/6v(P). 



In a few instances, donor ovarian tissue was taken from rabbits, or from 

 other rodent species {Microtus calif ornicus (1), Per omy sens maniculatus, Mus 

 musculus), and from young adult women at the time of operation. Ten 

 guinea-pigs and 6 rabbits were used as recipients, and cortisone, x-ray, and 

 desensitization of embryos with cellular suspensions from future donor 

 species, all were tried in order to reduce recipient antigenicity (10). 



MORPHOLOGIC OBSERVATIONS 



Of 1296 transplants of rat ovarian tissue into the eyes of rats, 1084 (84%) 

 became vascularized within 4 days of the time of transfer. Ovulation did not 

 occur spontaneously, but was observed in about 6% of grafts following 

 gonadotropin injections. Ovulation usually occurred 14 to 18 hr after the 

 second injection, and was more common in the eyes of castrated males than of 

 ovariectomized females. Although usually 6 to 8 large follicles developed, 

 no more than 2 ova were ovulated at one time. Ovulation occurred as early 

 as the seventh day after transplantation and could be induced again eleven 

 days later, but the critical intervals were not determined. In some cases the 

 ovulated ova were grossly and microscopically indistinguishable from normal 

 ova, but in others the cumulus cells were densely packed (as around an im- 

 mature ovum) and the vitellus showed degenerative changes suggesting atresia. 



The initial growth and maturation of follicular ova in ovarian tissue 

 transplanted from black donor rats to albino hosts was indistinguishable 



