Regulation of Folliculogenesis in the Cycling Rhesus Monkey: Selection of the Dominant Follicle

Abstract

To identify factors regulating the initiation of follicle growth in adult primates, the ovarian cycle of sexually mature rhesus monkeys was interrupted by surgical ablation of the preovulatory follicle or functioning corpus luteum (CL). In 10 of 10 animals, cautery of the largest visible follicle on Day 8-12 of the cycle blocked ovulation, and in all but one abolished the expected midcycle surges of gonadotropin secretion. In 8 monkeys of this group, surges of LH and FSH release occurred 12.4 +/- 0.9 days (d) (mean +/- SE) after cautery, coincident with elevations in serum estrogens, and succeeded by typical luteal phase patterns of circulating progesterone (P). No gonadotropin or estrogen surges were observed during the next 32 days of sampling in the remaining pair, despite visible new vesicular follicles. Removal of the CL in 5 of 5 monkeys 4-6 days after the midcycle LH surge was followed by a reduction in serum P to less than 0.25 ng/ml within 24 h and by the onset of menses within 3-4 days. After luteectomy in 4 of the 5 animals, preoperative levels of LH and FSH were maintained until 12.8 +/- 0.9 days, when typical surges of gonadotropin secretion occurred, followed by a normal luteal phase pattern of P. The fifth luteectomized monkey menstruated again 25 days after ablation without intervening surges of estrogen or gonadotropin release and did not ovulate. Sham follicle cautery did not block ipsilaternal ovulation or impair progesterone secretion by the CL in 2 of 2 monkeys. These observations indicate that, by the middle of the follicular phase, the follicle destined to ovulate had been selected, and that no other follicles were soon competent to mature. That the interval from ablation, at either phase of the cycle, until the next ovulation was the same indicates: a) that the prevailing ovarian steroidal milieu at ablation had no discernible differential effect on the time-course of resumed ovarian activity, and b) that midcycle surges of estrogen or gonadotropin secretion were not required either to initiate or synchronize subsequent follicle growth.

Effect of the stage of the oestrous cycle on the follicular population in pony mares

“…Although the left ovary has been frequently reported to ovulate slightly more often than the right (Osborne, 1966 ;Ginther, 1979) (Goodman et al, 1977) and quite different from that found in the ewe (Land, 1973).…”

Passive immunization with anti-oestradiol antibodies during the luteal phase of the menstrual cycle potentiates the perimenstrual rise in serum gonadotrophin concentrations and stimulates follicular growth in the cynomolgus monkey (Macaca fascicularis)

“…Evidence for this suggestion is represented by observations that surgical removal of the corpus luteum during the mid-luteal phase of the macaque menstrual cycle is followed by the reinitiation of follicular growth which occurred, in some instances, in the absence of statistically significant increases in plasma concentrations of FSH and/or LH (Goodman et al, 1977). However, in other similar studies, there was clear evidence of elevations in gonadotrophin concentration after removal of the corpus luteum (Goodman & Hodgen, 1979), thereby, making it difficult to rule out the possibility that the reinitiation of follicular growth was due to elevated gonadotrophins rather than removal of an intra-ovarian modulator.…”

Do Hormonal Characteristics of the Luteal Phase Affect the Conception Rate of Women Undergoing IUI Treatment in the Following Menstrual Cycle?

“…All these 92 women underwent sonohysterosalpingography and they showed bilateral tubal patency and no endometrial cavity abnormalities. 11 The IUI treatment resulted in 44 women conceived (age: 29.8 ± 3.8, mean ± SD, range [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. In total these 44 women had undergone a total of 117 treatment cycles (ie, 44 conceptional and 73 non-conceptional).…”

“…In total these 44 women had undergone a total of 117 treatment cycles (ie, 44 conceptional and 73 non-conceptional). The remaining 48 women who did not conceive underwent a total of 171 treatment cycles (age 30.3 ± 3.8 years, range [23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. The causes of infertility among the 44 women who conceived were male factor, 34 and unknown, 10.…”

“…[26][27][28][29][30][31] Also, a negative effect of the corpus luteum on follicular growth is already present in the actual luteal phase, since the diameter of the largest follicle in the ipsilateral ovary containing the corpus luteum is smaller than that of the contralateral ovary without corpus luteum. 32 The present study corroborates these earlier findings and warrants further studies to elucidate the mechanisms by which progesterone and the corpus luteum in humans are capable of affecting follicular development prior to the gonadotrophin dependent stage.…”