Ovarian Follicular Development Leading to First Ovulation and Accompanying Gonadotrophin Levels as Studied in the Unilaterally Ovariectomized Rat

Abstract

Ovarian follicular development was studied in the rat during a 15-day period preceding first ovulation. Ovaries were obtained by unilateral ovariectomy performed at various ages and the rats were allowed to live until the day after first ovulation. The timing of this ovulation was compared with that in unoperated, paired control rats of the same age. For estimation of gonadotrophin levels, blood was taken from the paired control rats at the time when experimental rats were unilaterally ovariectomized. There was no evidence that unilateral ovariectomy had any influence on the timing of first ovulation. Therefore the ovaries obtained could be dated in relation to first ovulation, and follicular growth during the final prepubertal period could thus be studied in a genuine developmental sequence. Results revealed that follicular growth leading to first ovulation starts at +/- 8 days before this ovulation; follicular processes taking place are comparable to those found during the adult 5-day cycle but proceed more slowly. Gonadotrophin concentrations accompanying the follicular dynamics and measured at 11.00 h, showed a clear tendency for FSH concentrations to decrease with increasing age, i.e. approaching first ovulation. Concentrations of LH did not show a definite pattern and were generally low, although in some individual rats relatively high LH values ( greater than 100 micrograms/l) were found in the period of 5-3 days before first ovulation.

Medial Preoptic Area, Estrogen, and the Peripubertal Desensitization to the Negative Estrogen Feedback in Female Rats

“…(2) Whereas advancement of puberty was obtained following the implantation of EB into the MPOA, similarly located implants containing the antiestrogen clomiphene citrate significantly delayed sexual maturation. (3) Although the control of gonadotrophin release in juvenile females is mainly exerted by the negative feedback action of estrogen [2], the prepubertal increase of the circulating estrogen level [15,16,32] does not prevent the preovulatory development of ovarian follicles [28] which, according to Richards et al [35], requires a slight, but sustained increase of LH secretion. Both medial preoptic lesions and EB implants placed in this area diminished more efficiently the estrogen-induced inhi bition of LH secretion than that of FSH release.…”

Is the infertility in hypothyroidism mainly due to ovarian or pituitary functional changes?

“…The ovaries were cut into 5-7-µm thick sections and stained with hematoxylin and eosin. For each ovary, at least five sections were selected, and the total number of corpora lutea and Graafian follicles was counted under the light microscope (19,20). The follicles were classified as secondary when they presented two or more layers of granulosa cells and as antral when they contained fluid.…”

Salmonid Follicle-Stimulating Hormone (GtH I) Mediates Vitellogenic Development of Oocytes in the Rainbow Trout, Oncorhynchus mykiss 1

“…However, removal of one ovary (unilateral ovariectomy [ULO], which results in the loss of a large pool of oocytes) leads to compensatory hypertrophy (COH) in the remaining ovary, often through additional recruitment of primary oocytes into the pool of maturing, secondary growth oocytes [21,22]. The phenomenon of COH is common to a wide variety of other animals (mammals [23][24][25][26], lizards, [27][28][29], amphibians [30][31][32], and other species of fish [33][34][35]). ULO, therefore, can be used as a tool to alter the normal pattern of ovarian development.…”