Acute and Chronic Elevations in Serum Levels of FSH After Unilateral Ovariectomy in the Cyclic Hamster

Effects of FSH and LH on incorporation of [3H]thymidine into follicular DNA

“…Hence, examination at 1-3 h after unilateral ovariectomy might have increased the percentage of granulosa cells entering into the S phase. This is consistent with the observation that the doubling time for follicles can be as short at 6h, after in-vitro exposure to pulsatile LH (Peluso, Luttmer & Gruenberg, 1984 (Bast & Greenwald, 1977). In the intact pro-oestrous hamster, follicles at stages [5][6][7][8] …”

“…This corroborates previous autoradiographic findings that, in the hypophysectomized hamster, FSH but not LH stimulates follicular development and thymidine uptake, as well as labelling index and intensity, especially in follicles with 2-3 layers of granulosa cells (Chiras & Greenwald, 1978b) In all polytocous mammals that have been investigated, unilateral ovariectomy results in prompt follicular compensation from the remaining ovary. As found by Bast & Greenwald (1977), unilateral ovariectomy resulted within 6 h in significant increases in both serum FSH and LH. This was accompanied by a rapid shift of follicles from Stages 4 to 5 (Roy & Greenwald, 1985).…”

“…The follicles were classified into 10 stages based on histological criteria: Stages \-<\ consist of 1-4 layers of granulosa cells; Stage 5 has 5-6 layers of granulosa cells with early formation of thecal cells at the 6 layered follicle; Stage 6 has 7-8 layers of granulosa cells; Stage 7 shows incipient development of an antral cavity; Stages 8-10 are small, intermediate and large changes during the periovulatory period suggested that fluctuations in blood gonadotrophin con¬ centrations might not only account for the recruitment of the next set of follicles destined to ovulate but also stimulate the growth of small preantral follicles. The present study was designed to test this possibility by using hamsters in which ovulation was blocked by injecting phenobarbitone at the onset of the critical period on the day of pro-oestrus (Siegel, Bast & Greenwald, 1976), which were hypophysectomized and subsequently treated with FSH (Moore & Greenwald, 1974) and those which were unilaterally ovariectomized (Bast & Greenwald, 1977).…”

Hormonal levels after ovarian X-irradiation of ewes

“…The acute FSH response to irradiation is a surge as soon as 20 h after treatment. Although the time course of this surge has not been exactly defined, its pattern is close to that described after hemicastration (Findlay and Cumming, 1977) (Hirschfield and Midgley, 1978a, b) triggers the recruitment of follicles due to ovulate at the next cycle and it has been hypothesized in hemicastrated rats (Butcher, 1977) and hamsters (Bast and Greenwald, 1977) (Dufour, Cahill and Mau[6on, 1979) are unclear. The irradiated, unsterilized ovary is able to develop follicular compensation after its contralateral ovary is removed (Humphreys and Zuckerman, 1954 ;Mandl, 1963 …”

“…that : 1) reducing the follicular numbers by 50 % does not seem to alter the ovulation rate (Land, 1973 ;Findlay and Cumming, 1977), and 2) the decrease in follicular numbers causing alterations in ovarian feedback induces transient modifications of the FSH levels (sheep : Findlay and Cumming, 1977 ;rat : Butcher, 1977 ; hamster : Bast and Greenwald, 1977). In the breed we used, the ovulation rate was not affected by the 50 % reduction in follicular numbers in either the cycle immediately following the X-rays or in later ones ; this rate was still 1 or 2 and had a mean value close to that of Ile-de-France ewes (1.4 : Thimonier and Maul6on, 1969 (Mandl, 1959 Possibly the reduction induced by this dose was so high some time after treatment (Baker, 1966) that the population of ovarian follicles in part of the animals remained below the minimal level for maintaining cyclic ovarian activity.…”