Ultrastructure and function of follicle cell in the ovary of Branchiostoma belcheri

The ultrastructure of follicle cells in the ovary at different developmental stages of Branchiostoma has been observed in detail with a transmission electron microscope. The results indicate that only one kind of follicle cell exists with structural features related to steroid hormone biosynthesis: (i) oval or round mitochondria with tubules; (ii) smooth surfaced endoplasmic reticulum; (iii) several large lipid droplets in the cytoplasm; (iv) a well de-veloped Golgi complex and tubular rough surfaced endoplasmic reticulum, as can be found in mammalian theca interna cells. In addition, as steroid hormone synthesizing cells, they obviously play an important role in the phagocytosis of relict gametes and cellular debris and may have a nutritive function for the oocytes. They can produce abundant secre-tory granules in stages III-IV ovaries. In mature ovaries they transform into flat epithelial cells with numerous micro-filaments which may play a role in ovulation.     

Ultrastructure and function of follicle cell in the ovary ofBranchiostoma belcheri

The ultrastructure of follicle cells in the ovary at different developmental stages ofBranchiostoma has been observed in detail with a transmission electron microscope. The results indicate that only one kind of follicle cell exists with structural features related to steroid hormone biosynthesis: (i) oval or round mitochondria with tubules; (ii) smooth surfaced endoplasmic reticulum; (iii) several large lipid droplets in the cytoplasm; (iv) a well developed Golgi complex and tubular rough surfaced endoplasmic reticulum, as can be found in mammalian theca interna cells. In addition, as steroid hormone synthesizing cells, they obviously play an important role in the phagocytosis of relict gametes and cellular debris and may have a nutritive function for the oocytes. They can produce abundant secretory granules in stages III-IV ovaries. In mature ovaries they transform into flat epithelial cells with numerous microfilaments which may play a role in ovulation.     

Reproductive biology of the polychaete Kefersteinia cirrata Keferstein (Hesionidae). I. Ovary structure and oogenesis

The ultrastructure of the ovary and the developing oocytes of the polychaete Kefersteinia cirrata have been described. The paired ovaries occur in all segments from the 11th to the posterior. Each consists of several finger-like lobes around an axial genital blood vessel. Oogenesis is well synchronised, young oocytes start to develop in September and vitellogenesis begins in January and is completed by May.

The young oocytes are embedded among the peritoneal cells of the blood vessel wall which have accumulations of glycogen and other storage products. Each oocyte becomes associated with a follicle cell with abundant rough endoplasmic reticulum. Yolk synthesis involves the accumulation of electron dense granules along the cisternae of the abundant rough endoplasmic reticulum. Active Golgi complexes are present and are involved in the production of cortical alveoli. The oocyte has branched microvilli, which contact the follicle cells or blood sinuses between the follicle cells and peritoneal cells. In post-spawning individuals the lysosome system of the follicle cells is hypertrophied and the cells play a role in oocyte breakdown and resorption.     

Specializations of endoplasmic reticulum in bovine placental cells

Summary The endoplasmic reticulum of mononuclear placental cells from 10 cows in different stages of pregnancy has been studied with the electron microscope. Basicaly the cryptal cells are provided with rough surfaced endoplasmic reticulum. In addition, whorls of rough or smooth cytomembranes encircle lipid droplets or plain cytoplasmic matrix. The trophoblastic cells also contain rough surfaced endoplasmic reticulum. Furthermore, skein-like conglomerations of smooth tubules are encountered in some cells. The significance of the membranous structures is discussed.This work was supported by the Swedish Medical Research Council (Project no K 68-12x-2494-01) and NIH General Research Support Grant FR05462.     

On the ultrastructure of follicles and isolated follicular granulosa cells of porcine ovary

Summary The endoplasmic reticulum in granulosa cells of primary, secondary, and small tertiary follicles of the porcine ovary is sparse and largely of the granular type.In granulosa cells of large tertiary follicles the endoplasmic reticulum shows distinct signs of proliferation. Some cells even contain whorls of endoplasmic reticulum membranes, essentially of the agranular variety.Direct continuity between endoplasmic reticulum membranes of the granular and agranular type as well as the continuous increase in agranular membranes suggest that these membranes may originate from the granular membranes.Granulosa cells isolated from large tertiary follicles by microdissection and keptin vitro show essentially the same ultrastructure as granulosa cells of intact large tertiary follicles.Some lipid droplets appear to be localized in cavities of the endoplasmic reticulum. It is suggested that the droplets contain precursor material for steroid hormone synthesis.Finally, the development of the agranular endoplasmic reticulum including the appearance of whorls in some granulosa cells of large tertiary follicles indicates that steroid synthesis may occur in such follicular granulosa cells.Read at the Meeting of the Swedish Society for Pathology in Umeå, September 25, 1965 (Bjersing, 1966).This investigation was supported by grants from the Swedish Medical Research Council (Projects No. 13 X-78-01, 12 X-78-02, and 12 X-78-03).     

Cytochemical and fine structural analysis of oogenesis in the gastropod, Ilyanassa obsoleta

An analysis of differentiating oocytes of the gastropod, Ilyanassa obsoleta, has been made by techniques of light and electron microscopy. Early previtellogenic oocytes are limited by a smooth surfaced oolemma and are associated with each other by maculae adhaerentes. Previtellogenic oocytes are also distinguished by a large nucleus containing randomly dispersed aggregates of chromatin. Within the ooplasm are Golgi complexes, mitochondria and a few cisternae of the rough endoplasmic reticulum. When vitellogenesis begins, the oolemma becomes morphologically specialized by the formation of microvilli. One also notices an increase in the number of organelles and inclusions such as lipid droplets. During vitellogenesis there is a dilation of the saccules of the Golgi complexes and cisternae of the endoplasmic reticulum. Associated with the Golgi complexes are small protein-carbohydrate yolk precursors encompassed by a membrane. These increase in size by fusing with each other. The “mature” yolk body is a membrane-bounded structure with a central striated core and a granular periphery. At maturity a major portion of the ooplasmic constituents such as as mitochondria and lipid droplets occupy the animal region while the bulk of the population of yolk bodies are situated in the vegetal hemisphere. The follicle cells incompletely encompass the developing oocyte. In addition to the regularly occurring organelles, follicle cells are characterized by the presence of large quantities of rough endoplasmic reticulum and Golgi complexes whose saccules are filled with a dense substance. Associated with the Golgi saccules are secretory droplets of varied size. Amongst the differentiating oocytes and follicle cells are Leydig cells. These cells are characterized by a large vacuole containing glycogen. A possible function for the follicle and Leydig cells is discussed.     

OVARIAN STEROID CELLS : I. Differentiation of the Lutein Cell from the Granulosa Follicle Cell during the Preovulatory Stage and under the Influence of Exogenous Gonadotrophins

The granulosa follicle cell of the Graafian follicle of the rabbit ovary differentiates into a lutein cell involved in steroid synthesis. Cytological events which occur within the granulosa cell of the normally stimulated follicle prior to ovulation have been duplicated by the intrafollicular injection of exogenous gonadotrophin. The luteinization of the granulosa cells involves the accumulation of 250- to 300-A, electron-opaque, spherical granules, dispersed within the cytoplasmic matrix, which have been identified as glycogen with the PAS-staining procedure. Further development of the granulosa cell following ovulation involves an increase in cell size, a decrease in the number of RNP particles, and an accumulation of an abundant system of intracellular membranes (agranular endoplasmic reticulum). Glycogen granules first appear in the granulosa cells as the separate, monoparticulate form. After follicle rupture and the formation of agranular endoplasmic reticulum, glycogen particles are present in a rosette arrangement within membrane-bounded vacuoles. The rosette arrangement of glycogen particles is also found dispersed within the cytoplasmic matrix of the lutein cell during the later stages of the cell life-span. Injection of luteinizing hormone or human chorionic gonadotrophin into a mature follicle also produces a marked accumulation of monoparticulate glycogen in the majority of granulosa cells, within 30 min. Cytoplasmic extensions which contain the glycogen masses are noticeably free of RNP particles.     

The ultrastructure of oogenesis and yolk formation in Labidocera aestiva (Copepoda: Calanoida)

Yolk formation in the oocytes of the free-living, marine copepod, Labidocera aestiva (order Calanoida) involves both autosynthetic and heterosynthetic processes. Three morphologically distinct forms of endogenous yolk are produced in the early vitellogenic stages. Type 1 yolk spheres are formed by the accumulation and fusion of dense granules within vesicular and lamellar cisternae of endoplasmic reticulum. A granular form of type 1 yolk, in which the dense granules within the cisternae of endoplasmic reticulum do not fuse, appears to be synthesized by the combined activity of endoplasmic reticulum and Golgi complexes. Type 2 yolk bodies subsequently appear in the ooplasm but their formation could not be attributed to any particular oocytic organelle. In the advanced stages of vitellogenesis, a single narrow layer of follicle cells becomes more developed and forms extensive interdigitations with the oocytes. Extra-oocytic yolk precursors appear to pass from the hemolymph into the follicle cells and subsequently into the oocytes via micropinocytosis. Pinocytotic vesicles fuse in the cortical ooplasm to form heterosynthetically derived type 3 yolk bodies.     

An assessment of mast-cell deficient mice (W/Wv) as a model system to study the role of histamine in implantation and deciduoma formation

The ovaries from mast cell-normal (+/+) and mast cell-deficient (W/Wv) mice were examined with light and electron microscopy. In addition the effect of ovariectomy and subsequent steroid treatment on total uterine histamine content, total mast cell numbers and surface and glandular epithelial cell heights was measured. The ovaries of +/+ mice were normal, displaying various stages of follicular growth and atresia and numerous corpora lutea; the ovaries of W/Wv mice lacked follicles and corpora lutea but contained numerous hyperplastic interstitial cells which contained numerous lipid droplets, vesiculated mitochondria and abundant endoplasmic reticulum suggestive of steroid synthesis. Steroid treatment of ovariectomized +/+ and W/Wv mice caused a significant increase in uterine wet weight and endometrial surface and glandular epithelial cell heights. In +/+ mice, steroid treatment caused a concomitant increase in total mast cells per uterine horn while mast cells were totally absent in W/Wv mice. The increase in uterine histamine in +/+ mice is consistent with the increase in mast cell numbers. Measurable amounts of uterine histamine, which increases slightly after steroid treatment, were demonstrated in W/Wv mice. Since the uteri of +/+ and W/Wv mice respond to steroids in a similar manner with the sole exception being histamine content and mast cell numbers, our results demonstrate the potential of using these animals to investigate the role(s) of uterine mast cells and non-mast cell uterine histamine in the process of implantation and the formation of a decidual cell response.     

Ovarian interstitial tissue of the wood mouse, Apodemus sylvaticus

The ovary of the wood mouse contains an unusually large amount of interstitial tissue which appears to develop from undifferentiated cells of the ovarian stroma and also by transformation of theca or granulosa cells of atretic follicles. The cells are characterized by the presence of smooth endoplasmic reticulum, rounded mitochondria with tubular cristae, and abundant, large (1.5 micron diameter) lipid droplets containing cholesterol and its esters. 3 beta-Hydroxysteroid dehydrogenase activity occurs in the interstitial cells. Their ultrastructural characteristics suggest that the cells are not very active, but their abundance and the considerable amount of steroid hormone precursor they contain may compensate for low secretory activity and they may be an important and (from a developmental viewpoint) early source of steroid hormone.     

扬子鳄卵巢性类固醇激素受体的免疫细胞化学研究

为探讨扬子鳄卵巢内不同性类固醇激素受体在卵泡发育中的调控作用,研究采用组织学和免疫细胞化学方法,运用激光共聚焦显微镜,对扬子鳄不同发育时期卵泡中的雌激素受体、雄激素受体和孕激素受体进行了检测。结果发现,3种类固醇激素受体在卵巢各期滤泡细胞中均有表达,在4月Ⅱ-Ⅳ期卵泡的滤泡细胞中阳性反应最强;9月卵巢的滤泡细胞中阳性反应最弱;ER和AR不仅在各期滤泡细胞中存在阳性位点,在6月卵泡的卵母细胞胞质中也有表达。结果说明,在扬子鳄卵母细胞生长发育和成熟过程中,3种激素受体通过与其对应的激素结合对滤泡细胞的发育、卵黄的合成与积累以及排卵起着重要的调控作用。       

The roles of THY1 and integrin beta3 in cell adhesion during theca cell layer formation and the effect of follicle-stimulating hormone on THY1 and integrin beta3 localization in mouse ovarian follicles

The mechanism of theca cell layer formation in mammalian ovaries has not been elucidated. In the present study, we examined the roles of THY1 and integrin beta3 in theca cell layer formation during mouse folliculogenesis. The localization pattern of THY1 and integrin beta3 in adult mouse ovary was investigated immunohistochemically. The strongest THY1 signal was observed in theca cell layers from secondary to preantral follicles, at which time theca cells have begun to participate in follicle formation. Integrin beta3 also localized to the theca cell layer of secondary to preantral follicles and showed a localization pattern similar to that of THY1. Moreover, the role of THY1 in theca cell layer formation was examined using a follicle culture system. When anti-THY1 antibody was added to this culture, no theca cell layers were formed, and the granulosa cells were distanced from each other. Because a THY1 signal was not observed in ovaries at stages earlier than prepuberty, THY1 localization also appeared to be affected by mouse development. This possibility was examined by determining the effect of administering follicle-stimulating hormone, luteinizing hormone, and 17beta-estradiol to 7-day-old mice on THY1 localization in the ovary 3 days later. Only follicle-stimulating hormone induced a THY1 signal in 10-day-old mouse ovaries. No THY1 signal was observed in untreated 10-day-old ovaries. In conclusion, THY1 might play a role in cell adhesion via binding to integrin beta3 in mouse ovaries. The present results suggest that THY1 localization may be affected by follicle-stimulating hormone in mouse ovaries.     

In vitro stimulation and inhibition of steroid hormone release from postovulatory follicles of the tilapia,Oreochromis mossambicus

Summary Postovulatory follicles of the tilapia, Oreochromis mossambicus, were incubated with graded doses of salmon gonadotropin to identify the steroid hormones released by this tissue. In addition, the effects of either cytochalasin B or colchicine on steroid hormone release were studied. After the incubation, the tissue was examined by electron microscopy. Postovulatory follicles released testosterone and estradiol-17B in a dose-dependent manner with gonadotropin. There was no detectable release of progesterone or 17a-OH-progesterone. When stimulated with high doses of gonadotropin, the steroidogenic cells showed an increase in smooth endoplasmic reticulum, Golgi complexes, and lipid droplets. Also, microfilaments became arranged in orderly bundles and were found close to the numerous secretory vesicles and lipid droplets. Upon incubation with gonadotropin and either colchicine or cytochalasin B, the cells still appeared steroidogenic, but the filaments were not organized nor associated with vesicles or lipid droplets. Release of steroid hormone decreased significantly. Also in these tissues, vesicles were no longer numerous in the apical region of the granulosa cells, but were located primarily near smooth endoplasmic reticulum and Golgi complexes. This suggests that disruption of the cytoskeleton results in reduced steroid hormone synthesis or release.     

Ultrastructural study of oogenesis in Monocelis lineata (Turbellaria,Proseriata)

Summary

Oogenesis in the marine turbellarian proseriat Monocelis lineata was investigated at the ultrastructural level. Oocyte differentiation is not synchronous so that successive stages of germ cell maturation were simultaneously detected in each of the two ovaries. Each developing oocyte is enveloped by follicle cell projections which are presumably involved in a morphologically undetectable support of vitellogenesis. The main features evidenced during oocyte differentiation are: (1) The synthesis of cortical granules by the rough endoplasmic reticulum and Golgi complex, occurring in the earlier stages of oogenesis; (2) The synthesis of yolk globules by the rough endoplasmic reticulum (RER) and Golgi complex, occurring in the later stages of oogenesis, namely late meiotic prophase I. Neither morphologically visible endocytotic activity, nor the presence of intercellular bridges, nor even the development of microvilli were observed at the oolemma or cortical ooplasm, so that the sole mechanism of vitellogenesis appears to be autosynthetic. The significance of these findings is discussed in relation to the taxonomic position of M. lineata and more generally in relation to the phylogenetic history of the class Turbellaria.     

Anatomy of the ovaries of the starfish Asterias rubens (Echinodermata)

Summary The ovaries of the starfish Asterias rubens were studied histologically and ultrastructurally. The reproductive system in female specimens consists of ten separate ovaries, two in each ray. Each ovary is made up of a rachis with lateral primary and secondary folds: the acini maiores and acini minores. The ovarian wall is composed of an outer and an inner part, separated by the genital coelomic sinus. The ovarian lumen contains oocytes in various phases of oogenesis, follicle cells, nurse cells, phagocytosing cells and steroid-synthesizing cells.Oogenesis is divided into four phases: (i) multiplication phase of oogonia, (ii) initial growth phase of oocytes I, (iii) growth phase proper of oocytes I, and (iv) post-growth phase of oocytes I. The granular endoplasmic reticulum and the Golgi complex of the oocytes appear to be involved in yolk formation, while the haemal system, haemal fluid and nurse cells may also be important for vitellogenesis. The haemal system is discussed as most likely being involved in synchronizing the development of the ovaries during the annual reproductive cycle and in inducing, stimulating and regulating the function of the ovaries.Steroid-synthesizing cells are present during vitellogenesis; a correlation between the presence of these cells and vitellogenesis is discussed.     

Profiles of gonadotropins and steroid hormone-like substances in the hemolymph of mud crab Scylla paramamosain during the reproduction cycle

To elucidate the role of gonadotropins-like substances in mud crab Scylla paramamosain, hemolymph samples were measured for concentrations of follicle stimulating hormone (FSH), luteinizing hormone (LH) and steroid hormones by enzyme-linked immunosorbent assay (ELISA). Hormonal concentration data were analyzed in association with the stages of gonadal development. ELISA has shown that in the female crab, the level of FSH reaches its peak in the early stage of ovary development, while estradiol and LH peaked during the late maturing stage of the ovary. In the male crab, testosterone and FSH culminated during the spermatid stage, and the level of LH peaked during the sperm stage. These results indicated that substances resembling the vertebrate FSH and LH are present in the hemolymph of S. paramamosain, and they may be involved in the development of the gonad.     

Stereological analysis of the guinea pig adrenal: effects of dexamethasone and ACTH treatment with emphasis on the inner cortex

This paper describes the morphological responses of adult male guinea pig adrenals to dexamethasone (DEX) and adrenocorticotrophic hormone (ACTH), in both qualitative and quantitative terms. Most organelles and inclusions are affected, but their responses often vary in the different cell types examined: zona fasciculata externa and interna, and zona reticularis. Following DEX the volume of lipid droplets increases in cells of zona fasciculata externa but decreases in zona reticularis; smooth endoplasmic reticulum decreases in fasciculata externa but increases in reticularis. Following ACTH, exactly the opposite occurs. This strongly suggests differing functions for these subcellular entities in each cell type, particularly for the smooth reticulum, as well as for the cells themselves. The volume of the Golgi complex markedly decreases following DEX in all cells but increases only in zona fasciculata interna and zona reticularis following ACTH. These deeper cortical cells are known to secrete at least one sulfated steroid, dehydroepiandrosterone sulfate, and these changes in the Golgi complex strengthen the suggestion that the Golgi plays a role in sulfation of steroids. Mitochondrial volume and number decrease in all cells following DEX, supporting their role in steroidogenesis. Further decreases in their volume, accompanied by increases in their number following ACTH, may be related to a proliferation of mitochondria in response to ACTH. Changes in peroxisome volume and number, following DEX and ACTH, suggest a possible role for these organelles in steroid cell metabolism. Lysosomes decrease in volume in all cells following ACTH. This does not support the recently suggested concept that they play a role in steroid secretion.     

Ultrastructural observations on possible sites of steroid biosynthesis in the ovarian follicular epithelium of two species of cichlid fish,Cichlasoma nigrofasciatum and Haplochromis multicolor

Summary The follicular epithelial layers of the developing ovary of two cichlid species were examined by electron microscopy for evidence of steroid secretion. As each oocyte grew, its follicular cell layers increased in height, eventually becoming somewhat columnar; no development could be detected in follicle cells of non-activated oocytes. Isolated cells close to capillaries in the thecal layer developed large amounts of smooth membrane indicative of steroidogenesis, appearing similar at maturity to testicular Leydig cells. In Cichlasoma nigrofasciatum the mitochondria of differentiated thecal elements contained microtubule-like inclusions. It is suggested that these cells may produce estrogens during vitellogenesis.In developing granulosa cells, active synthesis of granular endoplasmic reticulum occurred. This membrane appeared to arise from the nuclear envelope, and in the pre-ovulatory stage was always intermediate between smooth and granular forms, being only partly associated with ribosomes. Evidence for steroid biosynthesis in the granulosa at this time was therefore equivocal. Evidence was found of transfer of micropinocytotic vesicles from the granulosa cells into the ooplasm.The fate of the post-ovulatory follicle was investigated in Cichlasoma. Thecal elements remained separate from granulosa and unchanged in ultrastructure for up to ten days. The granulosa cells proliferated and differentiated within a few hours after ovulation into a cell type containing much smooth reticulum, characteristic of steroidogenesis. However, after approximately three days numerous signs of degenerative processes became visible. The significance of the observed ultrastructural changes in relation to endocrine function is discussed.     

Fate of the granulosa cells in the hen's follicle

Summary In an early growing follicle the single row of granulosa cells are in apposition — they have abundant Golgi substance and granular endoplasmic reticulum. During growth the granulosa cells become separated by wide intercellular spaces filled with perivitelline substance. The granulosa cells of the mature follicle immediately preceding ovulation have an agranular reticulum and numerous lipid droplets. Granulosa cells can be identified up to 72 h after ovulation. During the 72 h the cytoplasm becomes progressively replaced by lipid. The initial change in intracellular structure may indicate a shift in function towards production of progesterone followed by fatty degeneration preceding their final disintegration.     

Oogenesis in Acerentomon gallicum Jonescu (Protura)

Summary Late stages of oogenesis in Acerentomon gallicum Jonescu have been studied by means of light and electron microscopy. Each of the two ovaries of this species consists of a single panoistic ovariole. Late previtellogenic and early vitellogenic oocytes are enclosed in an electron opaque layer, the so-called primary sheath. The precursors for this sheath are most likely synthesized by follicle cells. The yolk develops through autosynthesis, with free ribosomes, dictyosomes and lamellar bodies being involved in the process. Mature yolk spheres contain proteins and polysaccharides. Besides the organelles that take part in vitellogenesis, mitochondria and cisternal stacks of the rough endoplasmic reticulum occur in the ooplasm.This work was supported by Government Problem Grant ii-1.3.13