Growth of ovarian follicles in rats in the absence of gonadotrophins

Hormone-controlled culture of secondary follicles of domestic cats

Ovaries were obtained from domestic cats during ovariohysterectomy. Large, preantral follicles were freed by dissection and mechanical crushing, and were cultured in TCM 199 + 10% FCS medium in the presence or absence of hormones (FSH, hydrocortisone and Insulin-Transferrin-Selenite) as well as in hypoxanthine. A decline in growth potential along with increasing follicle size were observed after one week, with no FSH added. Hormone-supplemented medium was found to induce growth to 2 or 3 times the original volume in more than 80% of follicles of all sizes. Oocyte diameters were continuously increasing, depending on follicle size, and reached 90 mum (80 %) at the point of antrum formation. Nuclear configuration of oocytes from follicles which had been cultured without addition of hormones up to the antral stage indicated a high rate of degeneration which, however, could be reduced by gonadotrophic stimulation. Meiosis at the germinal vesicle stage was found to be inhibited by hypoxanthine. For some oocytes, evidence was provided to meiotic maturation up to extrusion of the first polar body.

New natural inactivating mutations of the follicle-stimulating hormone receptor: correlations between receptor function and phenotype

Premature ovarian failure occurs in almost 1% of women under age 40. Molecular alterations of the FSH receptor (FSHR) have recently been described. A first homozygous mutation of the FSHR was identified in Finland. More recently, we described two new mutations of the FSHR in a woman presenting a partial FSH-resistance syndrome (patient 1). We now report new molecular alterations of the FSHR in another woman (patient 2) who presented at the age of 19 with primary amenorrhea contrasting with normal pubertal development. She had high plasma FSH, and numerous ovarian follicles up to 3 mm in size were evidenced by ultrasonography. Histological and immunohistochemical examination of ovarian biopsies revealed the presence of a normal follicular development up to the antral stage and disruption at further stages. DNA sequencing showed two heterozygous mutations: Asp224Val in the extracellular domain and Leu601Val in the third extracellular loop of FSHR. Cells transfected with expression vectors encoding the wild type or the mutated Leu601Val receptors bound hormone with similar affinity, whereas binding was barely detectable with the Asp224Val mutant. Confocal microscopy showed the latter to have an impaired targeting to the cell membrane. This was confirmed by its accumulation as a mannose-rich precursor. Adenylate cyclase stimulation by FSH of the Leu601Val mutant receptor showed a 12+/-3% residual activity, whereas in patient 1 a 24+/-4% residual activity was detected for the Arg573Cys mutant receptor. These results are in keeping with the fact that estradiol and inhibin B levels were higher in patient 1 and that stimulation with recombinant FSH did not increase follicular size, estradiol, or inhibin B levels in patient 2 in contrast to what was observed for patient 1. Thus, differences in the residual activity of mutated FSHR led to differences in the clinical, biological, and histological phenotypes of the patient.

The regulation of follicle growth: some clinical implications in reproductive endocrinology

OBJECTIVE

To review the literature concerning the regulation of follicle growth, to describe a model for unifollicular ovulation based upon the information gleaned, and to discuss some clinical implications in reproductive endocrinology underscored by this expanding knowledge.

DESIGN

Studies relating to follicular growth in lower animals and primates were reviewed. From the most pertinent articles the individual agents playing a significant role in the regulation of follicle growth were identified along with their mechanisms of action. A model for unifollicular development was proposed based upon the results of the review of these studies. Refinements in the management of some clinical problems in reproductive endocrinology were discussed based upon this model.

RESULTS

From a review of these studies it appears that in the human and primate menstrual cycle one follicle is selected because it has adequate FSH receptors when plasma FSH levels are high. This follicle becomes dominant despite falling FSH levels because of increased sensitivity of the follicle to FSH brought about by intraovarian growth regulators.

CONCLUSIONS

Improved care of patients requiring ovulation induction for differing indications should be possible with this more comprehensive knowledge of natural follicle growth.

Enhanced precision of estrus and luteinizing hormone after progesterone and prostaglandin in heifers

Objectives were to determine if low progesterone and increased basal luteinizing hormone for 3 d after injecting prostaglandin F2 alpha would affect precision of preovulatory surges of luteinizing hormone and onset of estrus in Holstein heifers. In experiments 1 and 2, heifers received progesterone devices for 10 d and prostaglandin F2 alpha on the 7th d after inserting progesterone device. For controls, progesterone devices were removed when prostaglandin F2 alpha was injected, and control devices were installed for 3 d. In experiment 1, jugular blood was sampled every 2 or 4 h from injection of prostaglandin F2 alpha until 108 h after removing progesterone to determine basal and peak secretion of luteinizing hormone. In treatment heifers, basal luteinizing hormone tended to increase, and intervals to peak secretion of luteinizing hormone were shorter and more precise than for controls. In experiment 2, heifers were observed for estrus for 30 min every 4 h for 96 h after removing progesterone devices. Intervals to onset of estrus for experimental heifers were shorter and more precise than for controls. After exogenous prostaglandin F2 alpha, 1 to 2 ng of progesterone per milliliter of serum for 2 to 3 d allows increased basal luteinizing hormone and is associated with increased precision of preovulatory secretion of luteinizing hormone and onset of estrus. This may be an acceptable method to control ovulation precisely for fixed time insemination of cattle.

Effects of PGF2 alpha-induced luteolysis and progesterone on follicular growth in pregnant mice

The effects of a luteolytic dose of prostaglandin F2 alpha on follicular development within the ovary of pregnant mice were studied in vivo and in vitro. The results showed that 1) PGF2 alpha reduced the number of growing primary follicles both in vivo and in vitro, 2) in vitro, progesterone and LH/FSH override this effect of PGF2 alpha and 3) progesterone suppresses the rate at which primary and preantral follicles grow. It is concluded that in the ovary of the pregnant mouse, progesterone regulates the number of primary follicles which start to grow; while gonadotropins and intraovarian progesterone levels control the rate at which primary and preantral follicles develop.

Effect of follicle-stimulating hormone (FSH) and estrogen on follicle growth in rats

The effect of follicle-stimulating hormone (FSH) and diethylstilbestrol (DES) on ovarian follicle growth was studied in hypophysectomized rats, using histologic, autoradiographic and histochemical techniques. The administration of FSH to immature hypophysectomized rats stimulated the follicle growth with thickening of the theca layer and repair of "deficiency cells". Although DES given to hypophysectomized rats also stimulated the follicle growth, the theca layer was relatively thin compared with that in FSH-treated rats. In order to detect cell division in a growing follicle, the number of labelled granulosa cells with tritiated thymidine as a proportion of the granulosa cells in a growing follicle were counted and the labelling indices of the granulosa cells were calculated. The labelling indices increased by the administration of FSH (p less than 0.05) or DES (p less than 0.05). The uptake of tritiated thymidine and leucine by the theca cells was enhanced only by FSH and was not stimulated by DES. The administration of FSH resulted in an increase of the histochemically demonstrable enzyme activity such as delta5-3beta-hydroxysteroid dehydrogenase (3beta-HSD) or alkaline phosphatase in the theca cells. In contrast, the administration of DES did not stimulate the enzyme activity of the theca cells. Furthermore, FSH stimulated a release of estradiol and estriol from the ovary of hypophysectomized rat, whereas DES did not. Although ovarian follicle growth was stimulated by both FSH and DES, the effect of the two hormones on the theca cells was quite different and the secretion of estrogen was stimulated by FSH. The results suggest that FSH induced follicle growth of the ovary might be mediated by estrogen produced by the theca cells.

An analytical model for ovarian follicle dynamics

Differential counts of follicles of different sizes in the ovaries of intact and hypophysectomized strain A mice of various ages have been analysed statistically. The influence of age on the number of follicles in each size group is described. The number of small follicles in the ovarian pool declined exponentially, whereas numbers of follicles in other groups displayed two peaks, one during immaturity and the other in adult life. These appeared sequentially in follicles in successive groups. The proportion of follicles growing and dying was estimated and age dependent fluctuations in the time spent by follicles in each group were demonstrated. Further calculations then determined the mean inflow and outflow of follicles to and from the various groups throughout the lifespan. Hypophysectomy during post-puberty decreased only slightly the utilization of small follicles from the pool and did not prevent their subsequent development to the two-layered stage. Many follicles then died at this stage of development, indicating that the initial main site of gonadotrophic action may be on medium sized follicles with two layers of granulosa cells.