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Unlabelled: Several authors have shown the effect of LH or hCG gonadotrophins on steroid secretion in the chick embryo ovary. However, the effects of luteinising hormone or human chorionic gonadotropin on chick embryo ovary innervation have not been studied. The purpose of the present work was to study the subcellular aspects of interstitial cells innervation in chick embryo ovaries cultured with LH or hCG. Coob's White Rock female chick embryos at 7, 11, 15 and 19 days of incubation (in ovo) were employed. Explants of the left and right ovaries were cultured separately for 4 days in: 1--Basic medium (control): minimum essential medium (MEM-GIBCO) with 10% bovine fetal serum, 2--Basic medium with added LH or hCG (problems). The cultures were processed to be studied ultrastructurally (TEM). Left and right ovary explants were fixed two hours at room temperature in Karnovsky's fixative. The tissues were then post-fixed in osmium tetroxide in 0.1 M cacodylate buffer for one hour and after a rinse in buffer were dehydrated in acetone: afterwards they were embedded in Araldite resin. Thick sections stained with 1% Toluidine blue were examined and photographed using a Zeiss Photo II microscope. Thin sections were stained with uranyl acetate and lead citrate and examined in a Siemens ElmisKop 101 electron microscope., Controls: In both ovaries the isolated interstitial cells and the appearance of nerve fibers and nerve endings were observed in the explants of 11 day cultured during four days and in a similar way at the age of 15 days of in ovo development., Problems: With LH or hCG nerve fibers and nerve endings were observed both in the right gonad and in the medulla of the left ovary in close contact with the steroid-producing interstitial cells. Ultrastructurally, the interstitial cells are recognized by their typical organoids: SER, Golgi apparatus, mitochondria with tubular crests and abundant lipidic droplets. The innervation of these cells were seen in ovaries at 7 days development, cultured during 4 days. The present state corresponds to that of 11 days development in ovo. The nerve endings had mitochondria, microtubules and small and medium-sized vesicles, some with an electrodense content. These results in vitro suggest that innervation of the ovaries is controlled by an indirect mechanism via the hypothalamic-pituitary system and another local with production neurotrophic factors modulated by LH.

The embryonic gonads produce and secrete the steroid hormones that induce secondary sex differentiation in different species. The production of estrogens, testosterone and progesterone by interstitial cells of the chick embryo ovary has been demonstrated in experiments in ovo and in vitro. Estrogens would be responsible at the 7th day of in ovo incubation, of the evolution of the functional left ovary. According to Gasc, only the cells of the germinative epithelium of the left ovary possess receptors for estrogens, thus originating the formation of a cortex in this functional gonad and not in the right one. On the other hand, extragonadal factors, such as gonadotrophins, would participate in gonadal differentiation. Involvement of the hypophysis in the morphological and functional differentiation of the ovary in the chick embryo, has been considered in several studies. Woods and Week established the functional hypophysealgonadal axis at 13 days of in ovo incubation. However, the effects of individual gonadotrophins on the interstitial cells of the chick embryo remain unclear. Avila et al. and Grassi Milano observed that when the female gonads were cultured without steroid or gonadotrophic hormones at the start of differentiation an hermaphrodite left ovary and a male right one were formed. Kyparissi and Vakolopoulu observed that the inoculation in ovo of FSH at the end of embryonic development led to an increment in the number and size of follicles in the left ovary. Pittini and Grassi Milano added FSH and LH to cultures of 15 days-old chick embryos testicles and ovaries and found that only male gonads developed similar to normal embryos.(ABSTRACT TRUNCATED AT 250 WORDS)

Ovulation may be achieved and studied in an isolated perfused rabbit ovary upon inclusion of human chorionic gonadotropin (hCG) in the perfusion fluid. The ultrastructural features of the rabbit ovarian follicle prior to ovulation in vitro were compared with those in vivo. The perifollicular vasculature was also examined in in vitro perfused rabbit ovaries during the preovulatory interval. Granulosa cells of the preovulatory follicle share many ultrastructural features in vivo and in vitro; however, only small amounts of smooth endoplasmic reticulum (sER) were observed in granulosa cells in vitro after hCG. Ovulation after hCG in the in vitro preparation tends to occur earlier (6 hours) than in vivo (12 hours). Thus, there may be insufficient time and/or gonadotropin exposure to permit full functional development of granulosa cells, as reflected by reduced amounts of sER. Degradation of collagen fibrils was less prominent in the theca externa and tunica albuginea in vitro than in in vivo. Perifollicular capillaries became dilated after hCG, but interendothelial gaps were not observed. Disappearance of surface epithelium in the apex of follicles was similar in vitro and in vivo.

Homocellular gap junctions between granulosa cells and between theca interna cells, and heterocellular gap junctions between granulosa cells and oocytes persist in rat ovarian follicles for as long as 90 days following hypophysectomy. Gonadotrophic and/or steroid hormones are therefore not required for the maintenance of gap junctions between these cells during early follicular growth. However, replacement therapy with estrogen and human chorionic gonadotrophin results in amplification of gap junctions in granulosa and theca interna cells respectively. Within 24h following hormonal stimulation, growth of gap junctions is characterized by the appearance of formation plaques as observed in freeze-fracture replicas and by the association of microfilamentous material located subadjacent to gap junction membrane observable in thin-sectioned cells.

The perifollicular capillaries of the rabbit ovary were observed by light and electron microscopy following administration of human chorionic gonadotropin (hCG) and indomethacin (IM). Fenestrations and interendothelial gaps were not observed at 4, 10, or 12 hours, at which times carbon particles were confined to capillary lumina. By 24 hours, dilated capillaries were noted among granulosa cells and theca. In the theca, interendothelial gaps permeable to carbon particles were observed. At 48 hours, ribosome-rich, newly developed capillaries were noted. Many collagen fibrils were observed in the tunica albuginea and theca externa in hCG/IM-treated rabbits in contrast to those treated with hCG alone. Ovarian prostaglandins normally produced in response to gonadotropins may be responsible for alterations in perifollicular capillaries and degradation of collagen in the follicle wall, changes considered essential for ovulation.

The two components of the interstitial tissue in the senile rat's ovary--deficiency cells and epithelial cellular cords--both contain steroidogenic organelles at a very low level of activity, which can be notably raised by HCG. Deficiency cells and epithelial cords are not the expression of primary ovarian aging, but the consequence of senile gonadotropic hypofunctioning. For that same reason, these ovarian structures become permanent and their possible cellular aging can thus be studied. No ultrastructural signs of senescence have as yet been observed.

Thin-section and freeze-fracture studies on the rat ovarian interstitial cells revealed reductions in the size and the number of gap junctions after pituitary ablation. Small gap junctions, however, persist as long as 90 days after hypophysectomy even though regressive cytoplasmic changes are completed 75 d earlier. Administration of exogenous human chorionic gonadotrophin (HCG) results in the restoration of the normal interstitial cell morphology which is accompanied by amplification of junctional membrane. Within 24 h of hormone application, gap junction growth is characterized by the appearance of formation plaques. These studies suggest that the effect of hormone on interstitial cell gap junctions is to modulate the junctional surface area.