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S Makabe

Publications and source records attributed to S Makabe.

34 records · Page 2Linked to original sources
PubMed1986

Elimination of germ cells during differentiation of the human ovary: an electron microscopic study.

Observations by scanning and transmission electron microscopy during ovarian development (from 7 wk until term of gestation) showed numerous germ cells within the superficial epithelial layer covering the ovary. In early stages of differentiation (between 7 and 11 wk), germ cells appeared to be actively migrating to the surface of the ovary by ameboid-like movements. Later, the transfer of the germ cells to the surface epithelium was also occurring passively, as a consequence of an intense proliferation of germ and somatic cells - arranged in clusters and cords - migrating towards the most superficial areas of the ovary. The present evidence suggests that a number of primordial germ cells - as well as oogonia and oocytes - which lie in the superficial epithelium can leave the ovary and ultimately rest freely upon its surface. Elimination of germ cells during differentiation of the ovary in humans was always paralleled by necrosis of oogonia and oocytes and atretic alteration of primitive follicles. The significance of these processes is discussed in relation to the reduction of the pool of oocytes at birth.

Cell Differentiation↗
PubMed1986

Germ cells in the ovarian surface during fetal development in humans. A three-dimensional microanatomical study by scanning and transmission electron microscopy.

Observations by correlated scanning and transmission electron microscopy during human ovarian development (from 7 weeks to delivery) have revealed germ cells in the surface epithelium of the ovary. During embryonal differentiation (7/8 weeks) and in early stages of fetal development (9-12 weeks) the ameboid features of some primitive germ cells occurring in the cortical areas of the ovary, would suggest their capability to move and possibly migrate to the superficial coelomic layer covering the gonad. Subsequently the germ cells, gradually transformed in clusters of dividing oogonia and further meiotic oocytes, were closely associated to proliferating somatic cells of sexual cords and often resulted passively pushed and consequently dislocated in the most superficial areas of the ovary. As a result of these intense morphogenetic processes--even when the ovary was fully developed--the germ cells which were early in these superficial areas became included in the surface epithelium of the ovary. Therefore, through all stages of ovarian development and from these areas, germ cells were extruded on the surface of the gonad and ultimately liberated in the peritoneal cavity. Since germ cells were found within the surface epithelium of the ovary even in two newborns, and since some of these oocytes were eliminated from the ovary, it is possible that this extrusion mechanism might even continue to operate during the period between birth and puberty. On the other hand germ cells that in early stages had been more deeply located in the ovarian tissues, closely associated with the proliferating sex cords, maintained this relationship and became later incorporated in primitive follicles. Present evidence suggests that the above morphodynamics can be most likely depending upon a special tropism of germ cells towards the epithelioid components of the surface epithelium and mesonephric cords of the developing ovary. This close and early relationship between somatic and germ components is recognized as crucial to further development and fate of germ cell population in human ovary.

Cell Movement↗
PubMed1982

Development of the ovarian surface and associated germ cells in the human fetus. A correlated study by scanning and transmission electron microscopy.

The ovarian surface and associated germ cells have been studied in human fetuses from 12 weeks of age until near term, using light, TEM and SEM techniques. The surface epithelium and related cords proliferate extensively, especially at midterm. The cords of the ovarian cortex appear to be linked with ingrowths from the surface epithelium, and both structures have a common basal lamina. Germ cells are always interspersed among the somatic cells of the surface epithelium and associated cords. These results indicate that both the proliferating cords and surface epithelium may contribute to the formation of early follicles. Furthermore, the occurrence, of elements having some of the features of primitive steroidogenic cells in the regions of cord-surface epithelium continuity, suggests that both structures (surface epithelium and cords) contribute somatic cells, which in addition to becoming granulosa cells, might also contribute to the provision of primitive interstitial cells. Gonocytes tend to migrate through the developing ovarian tissue towards the surface where they become extruded into the peritoneal cavity. This phenomenon might contribute to the reduction in the number of germ cells at birth and parallels the atretic processes within the ovary.

Cell Membrane↗
PubMed1982

Scanning electron microscopy of nonfunctional human ovaries.

Samples of ovaries taken from fertile and infertile patients, 23 to 32 years of age, were fixed in 2.5% buffered glutaraldehyde, processed by critical point drying, sputter coated with gold palladium and viewed by scanning electron microscopy. Cell cores proliferating from the tunica albuginea into the stroma were made up of an epithelium similar to that covering the ovarian surface. Ovarian papillae, arising from the ovarian surface, were covered with typical polyhedral superficial cells. The oocyte and granulosa cells were connected by means of microvilli, desmosomes and gap junctions. After ovulation the stigma was occupied by a mass of connective tissue to which were attached red blood cells (coagulated blood) and residual follicle cells. In the postovulatory follicle the adjacent superficial epithelium underwent extensive proliferation to repair the rupture point. The anovulatory ovaries were completely covered with superficial epithelium, which was packed tightly and exhibited dense microvilli, blebs, solitary cilia, ruffles, filopodia and different types of cytoplasmic projections. This was in contrast to the ovulatory ovary, in which the superficial epithelium seemed to be localized only in certain areas and the site of the follicular rupture was not completely repaired by superficial epithelium.

Adult↗
PubMed1980

Surface ultrastructure of functional and nonfunctional human ovaries.

Biopsies of human ovaries from functional and nonfunctional polycystic ovary patients 24 to 56 years of age were processed by critical point drying and viewed by scanning electron microscopy. The superficial epithelium was characterized by polyhedral-shaped cells with abundant evenly distributed apical microvilli with some intercellular connection and occasional solitary cilia. The fine structure modifications in the ovarian superficial epithelium (e.g., microvilli, blebs, ruffles, and micropapillae) reflect physiological changes in cell cycle or reproductive cycle. Dramatic changes were noted in the superficial epithelium of polycystic, atrophic, and sclerotic ovaries: distribution of microvilli, proportion of cells of different morphology, abundance of solitary cilia, blebbing, and the size of rufflings. In developing follicles, the granulosa cells were spherical and/or polyhedral in shape and in close contact. In atretic follicles, the granulosa cells were flattened and very irregular in shape without cytoplasmic evaginations. The loss of such evaginations within the atretic follicles may correspond to functional changes, e.g., inability to bind and respond to gonadotropic receptors. Follicles in polycystic ovaries were characterized by the disruption of the granulosa layer. Thus, areas of the follicle were devoid of any granulosa cells and appeared patchy, whereas the granulosa cells were irregular in size and shape.

Adult↗
PubMed1979

Surface ultrastructure of polycystic ovaries as viewed by electron microscopy.

Scanning electron microscopy was used to observe surface fine structure of germinal epithelium and granulosa cells of human ovaries from 24 patients with polycystic ovaries and primary infertility. Synthetic LH-RH was administered intravenously and serum LH was measured at frequent intervals before and after LH-RH injection. The PCO patients were arbitrarily classified into two groups on the basis of ovarian morphology: typical PCO (Type I) with greater LH response than the lower LH response of a typical PCO (Type II). The germinal epithelium which did not completely cover the surface of the normal ovary was characterized by patchy areas of cells with and without dense microvilli. In normal preovulatory follicles, most granulosa cells were polyhedral in shape with smooth surfaces, whereas those facing the follicular cavity were elongated and flattened and were covered with material having a filamentous/reticular texture. In PCO the germinal epithelium surrounding the whole surface possessed dense microvilli, solitary cilia, and blebs, resembling the fetal ovary. In normal ovaries, the follicular cells were uniform in size and shape with microvilli and evaginations. The PCO cells have irregular size and shape with few microvilli.

Adult↗
PubMedDate not supplied

The ultrastructure of human reproduction. I. The natural history of the female germ cell: origin, migration and differentiation inside the developing ovary.

This presentation, on both printed copy and CD-ROM, summarizes a series of original data on the ultrastructure of human reproduction produced by our research group. In particular, female germ cell behaviour at the time of migration and colonization of the gonad and germ-somatic cell interactions inside the developing ovary are reviewed from a morphodynamic point of view. The results mostly consist of black-and-white transmission and scanning electron microscopy (TEM and SEM) images. Artificially coloured SEM pictures, light microscopy images and drawings have also been selected for iconography to render complex microanatomical details and their morphofunctional relationships more comprehensible. In all, 35 images are presented in this article, each related to a concise text section and accompanied by a self-explaining caption. A list of pertinent references is also provided.

Cell Differentiation↗
PubMedDate not supplied

The fetal development of the human uterine cervix from the 12th to the 31st postmenstrual week as revealed by scanning electron microscopy. Anatomical and clinical correlations.

To clarify the differentiation of the human uterine cervix, fetuses of the 12th, 15th, 18th, 20th, 21st, 22nd, and 31st postmenstrual week were studied by Scanning Electron Microscopy. At the 12th week the endocervical epithelium consisted of microvillous cells, often showing single cilia and anlages of tubular glands. At the 15th week the cervical canal was entirely formed and its surface cells appeared columnar. At the 18th week these cells were replaced by flat or slightly raised cells, provided with thin microplicae. At the 20th week the endocervical epithelium appeared pseudostratified with higher, apically-convex and shorter basal cells; glands developed in form of tubular invaginations of the luminal epithelium. At the 21st week in the lower part of the endocervix polymorphic, globose cells with short and stubby microvilli and others elongated, having short microplicae, were observed. These latter likely corresponded to the so-called columnar cells undergoing squamous metaplasia. Among microvillous and/or metaplastic cells, a number of apoptotic cells, as globose elements with a ruffled and invaginated surface, were also noted. At the 22nd week evident plicae palmatae were found, covered by microvillous secreting cells. These showed smooth bulged apices releasing droplets by a "micro-apocrine" mechanism. These features increased at the 31st week, when many droplets were noted also around the mouth of the cervical glands. Only at this phase of development fully ciliated cells were found often contacting secretory material. Mature squamous exfoliating cells with complex microplicae covered an hypertrophied portio vaginalis. The squamous cells extended toward a squamo-columnar junction in form of flat, tongue-like projections. Their tips consisted of immature squamous metaplastic cells, which were endocervical columnar progressively becoming elongated elements, exhibiting short microvilli. The above features are rather similar to those occurring during the adult reproductive age. Therefore, it might be hypothesized that, during pregnancy, a common gestational hormonal background may induce somewhat similar morpho-dynamic processes in the cells and tissues of the fetal reproductive tract mimicking what occurs in the adult female.

Cervix Uteri↗