The aim of this study was to examine the effects of prepubertal hypothyroidism on ovarian development in rats. Therefore, from birth up to day 40 postpartum, rats were given 6-propyl-2-thiouracil (PTU) via the drinking water of mothers and pups. At ages ranging from 12 to 40 days, ovarian weights were measured and serum was collected to estimate thyrotrophin (TSH), follicle-stimulating hormone (FSH) and inhibin levels. Two hours before sacrifice the animals received an injection of bromodeoxyuridine (BrdU) to estimate the proliferative activity of the follicular granulosa cells. Ovaries were fixed in Carnoy's fluid and follicle counts were performed on sections stained with anti-BrdU and with haematoxylin and eosin. The PTU treatment resulted in increased serum TSH levels, indicative of hypothyroidism, and markedly lower body and ovarian weights, whereas serum FSH and inhibin levels were hardly affected. At day 40, ovaries of PTU-treated animals contained relatively more secondary and less antral follicles, smaller non-atretic antral follicles and more atretic follicles when compared with untreated rats, while corpora lutea were absent. It is concluded that this disturbed folliculogenesis is due to inadequate thyroid hormone supply, which hampers the differentiation and not the proliferation of granulosa cells because diameters of antral follicles were significantly smaller whereas the BrdU-labelling index had not changed.

No abstract

The distribution of the intermediate filament (IF) proteins desmin, keratin, and vimentin was studied immunohistochemically in bovine ovaries. Special attention was paid to granulosa cells to examine possible marked changes of IF distribution in relation to folliculogenesis during ovarian development. Therefore, ovaries were used from fetuses from 3 months of gestation onward, calves, heifers, and cows. In all ovaries, desmin immunoreactivity was restricted to smooth muscle cells in blood vessel walls. Keratin appeared a characteristic of the ovarian surface epithelium. Co-localization of keratin and vimentin was observed in the epithelium of rete ovarii tubules in fetuses and calves, and in cortical cord epithelium and pregranulosa cells of primordial follicles in fetuses at 3-7 months of gestation. Vimentin was demonstrated in endothelium and in fibroblasts. In addition, vimentin immunoreactivity was present in granulosa cells of primary, secondary, and antral follicles. In antral follicles, these granulosa cells mainly had an elongated appearance and either contained an oblong or a round nucleus. Those with an oblong nucleus were characteristic for atretic antral follicles. In nonatretic follicles, numerous vimentin immunoreactive, elongated granulosa cells with a round nucleus were observed, especially in the peripheral granulosa layer and in small ( < 3 mm in diameter) antral follicles. Additionally, in antral follicles, protrusions of vimentin-positive corona radiata cells were observed, that penetrated the zona pellucida to contact the oocyte. The data show that the distribution of vimentin containing IFs is associated with various aspects of granulosa cell activity, as mitosis, atresia, and intercellular transport.

The distribution of the neuropeptides vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) was studied immunocytochemically in bovine ovaries from 3 mo of gestation up to and including puberty, and from adult cows at three stages of the estrous cycle. The appearance of VIP and NPY immunoreactivity of 4.5-6 mo of gestation coincided with the onset of follicular development. In contrast to NPY, VIP was first found in the cortex. Both VIP and NPY immunoreactivity increased with age. From 9 mo of gestation onwards, VIP and NPY were found around blood vessels and non-vascular smooth muscle cells, in the stroma near preantral follicles, and in the theca externa of antral follicles. In addition, VIP-positive cells were observed exclusively in the granulosa layer of the preovulatory follicle at the time of the LH surge. The distribution of VIP- and NPY-immunoreactive fibers in the ovary may point to an effect of these neuropeptides on various physiological processes, including follicle development and ovarian blood flow. In addition, the presence of VIP-positive cells in the granulosa layer of the preovulatory follicle is indicative of a role for VIP in ovulation.

Enhanced serum oestrogen levels and highly steroidogenic, luteinized atretic follicles in the ovaries of the Djungarian hamster (Phodopus sungorus ) kept under a short photoperiod from birth R van den Hurk, G Dijkstra and F H de Jong AbstractObjective: In contrast to the elaborate information available on the effects of the photoperiod on the testes of hamsters, little is known about the influence on their ovaries. This study aimed to describe the ovarian follicular development and steroid hormone production in Djungarian hamsters kept from birth under a short daylight regime. Design and Methods: Female Djungarian hamsters (Phodopus sungorus ) were kept under two different light regimes: (i) 16 h light:8 h darkness (long daylight; LD) and (ii) 4 h light:20 h darkness (short daylight; SD). They were killed at 28, 56 and 80 days after birth; blood and ovaries were collected. Ovaries were either fixed in Bouin's solution or frozen. Fixed material was dehydrated, embedded in paraffin, serially sectioned at 5 mm and stained with haematoxylin and eosin, whereafter all healthy and atretic follicles were classified and counted. 3b-Hydroxysteroid dehydrogenase (3b-HSD) was histochemically demonstrated in 10 mm sections of frozen ovaries. Serum oestradiol-17b and progesterone levels were determined by RIA. Results: The numbers of healthy preantral and antral follicles were higher in LD than in SD hamsters. Antral follicles did not significantly differ in number during development in LD hamsters, but they were completely absent from 80-day-old SD animals. In LD animals the number of apoptotic preantral follicles dramatically increased with age. In SD animals the numbers of apoptotic antral follicles strongly decreased with age, whereas numerous non-apoptotic follicles with luteinized granulosa cells and a degenerated oocyte appeared, and in increasing numbers with age. During development, moderate 3b-HSD activity was present in interstitial cells, theca cells of healthy follicles, and in both theca and granulosa cells of degenerating follicles. Strong enzyme activity was found in the hypertrophied granulosa cells of luteinized atretic follicles. Mean serum progesterone values varied from 2 to 6 nmol/l and were not different in LD and SD hamsters. Mean serum oestradiol levels varied from 132 to 542 and 325 to 2353 pmol/l in LD and SD hamsters respectively. The highest oestradiol levels were found in SD animals at day 28 of development. Conclusions: Folliculogenesis was dramatically disturbed in Djungarian hamsters raised under a short photoperiod. These animals developed high serum oestradiol levels and numerous luteinized atretic follicles with highly steroidogenic granulosa cells, which appear to be the source of the increased serum oestradiol levels.