RESUMEN

Various ultrastructural changes occur during follicular growth in the rat oocyte nucleolus. The nucleolus, which has a reticulated fibrillogranular structure at the primordial and primary follicle stages, becomes entirely compact and is made up of a conspicuous and homogeneous mass at the antral follicle stage. In order to define the nature and the functions of this homogeneous mass, cytochemical methods allowing detection of nucleic acids, proteins and lipids were performed at the light microscopic and ultrastructural levels. The results obtained suggest that this nucleolar mass is probably composed of acid proteins which are not silver stained. This proteinaceous mass could be a special kind of nucleolar secretion providing material for meiotic resumption in the oocyte. Cytochemical researches now in progress should supply new information concerning the exact nature and the role of the nucleolar compact mass, which is the essential nucleolar component at the antral follicle stage and which really plays a role in the nucleolus in the first stages of embryogenesis.

Asunto(s)

RESUMEN

A morphometrical study of gap junctions has been realized in rat antral follicle after an injection of 20 I. U. of hCG. A clear and rapid reduction of the gap junctions number and of the membranous surface they are occupying has been demonstrated whatever the follicle region one consider. The significance of those gap junction modifications is discussed with respect to resumption of meiotic maturation.

Asunto(s)

RESUMEN

The ultrastructural evolution of the nucleolus was followed during follicular growth by means of a silver staining procedure. The oocyte nucleolus in the primordial and primary follicles consists of strands of dense fibrillar silver-stained component and aggregates of granules which are devoid of silver grains. Small fibrillar centres are also recognized and appear to have less silver stainability. At the secondary follicle stage, a new nucleolar component appears in the reticulated oocyte nucleolus. This component is devoid of silver grains. During follicle growth, at the antral follicle stage, this new component seems to fuse and the nucleolus becomes constituted of a compact homogeneous mass which exhibits a vacuole at the end of the oocyte maturation. The results obtained suggest that this nucleolar mass is essentially made of proteins and particularly of acidic proteins.

Asunto(s)

RESUMEN

Recently Merveille and al (1984) using light microscope have observed intranucleolar cavities in rat ovocytes from large antral follicles. They have showed that the frequency of these vacuoles increases when follicular growth is stimulated by gonadotropins. In this paper, the ultrastructure of the nucleolar cavities has been studied. Two types of cavities are visible in these nucleoli: 1. nucleolar "interstices" present at the periphery of the nucleoli in remnants of the granular component and of the dense fibrillar components; 2. nucleolar "vacuoles" which are located in the homogeneous substance forming the greatest part of the nucleolus. The nucleolar vacuoli generally are clear-cut and spherical. The density of their content is similar to the nucleoplasm but they don't communicate to the nucleoplasm. By means of cytochemical to detect Ag-NOR proteins (Ploton and al [1983]) and basic proteins (Sheridan and Barnett [1984]), dense fibrillar component of the nucleolus but no basic proteins may be seen in the wall of the cavity. Moreover no evidence of relation between the presence of the vacuoles and the process of follicular atresia has been found.

Asunto(s)

RESUMEN

Oocytes removed from antral follicles of 28- to 30-day-old rats treated with FSH (Folligon) show cavities and vesicles in the nucleoli. Repeated injections of Folligon significantly increase the frequency of these nucleolar inclusions. A possible relationship between intranucleolar cavities and rRNA metabolism has been suggested to account for this occurrence.

Asunto(s)

RESUMEN

We have brought the evidence for the presence of type I and III collagens and laminin in cultures of eyelid buds removed just before the onset of their junction. The patterns of distribution of laminin (localized in all basement membranes) and of the type III collagen remain constant during all the culture. Type I collagen is distributed homogeneously in the mesenchyma like type III collagen after the twelfth hour of culture. The rapid stabilization of these three distributions would be associated with the persistence of an epithelial seam limited by intact basement membranes between mesenchymal eyelids from the stage of junction to the later stage of disjunction of the eyelids.

Asunto(s)

RESUMEN

Recently, we suggested that the cell coat of the surface epithelial cells of the palatal shelves and especially its sialyl groups are implied in the adhesion process which initiates the constitution of the secondary palate. In this work, use of cationized ferritin which interacts with anionic receptors of the plasma membrane give us the possibility to render these sialic acids visible. After five minutes incubation in presence of cationized ferritin, the labeling particles are distributed in monolayer over the plasmalemma of epithelial cells. Subsequent incubation in cationized ferritin free medium results in clustering of the marker followed by the detachment of the labeled patches. Otherwise, incubation in the presence of neuraminidase from Clostridium perfringens before the polycationic ligand contact prevents labeling. We think that lateral migration modifications of the anionic receptor could be associated with changes of the shelves capacity to adhere.

Asunto(s)

RESUMEN

In a previous work, we demonstrated that palatine processes treated with 10 micrograms/ml neuraminidase for 30 minutes at 37 degrees C show a delayed fusion in vitro. In order to investigate the effects of neuraminidase, the treated palatine processes were observed with the aid of transmission and scanning electron microscopy. The effect of neuraminidase is exclusively detectable on superficial flat cells of the palatine processes, especially the cells of the medial edge of the process. The epithelial basal cells remain unchanged. Observed with the S.E.M., the superficial epithelial cells show bubbles, become spherical and detached. To explain these observations, we namely propose the following hypothesis: the action of neuraminidase prevents the fusion of the palatine processes because it denudes basal cells bearing a too immature cell coat for ensuring sufficient adherence between the palatine processes.

Asunto(s)

RESUMEN

Rat palatal processes have been explanted after 15 days 18 hours of gestation and cultivated in homologous pairs, side by side during 24 hours. Most of them have been treated in vitro by hydrocortisone and vitamin A in excess. In all cases, palatal processes fuse. Thus, the phenomenon does not seem disturbed by this glycocorticoid.

Asunto(s)

RESUMEN

The ultrastructural study of the unfertilized Rat egg ooplasm has shown that the so-called lamellar structures are in fact filaments constituted of proteins and where no ribonucleic acid can be detected. Thus, they do not represent a particular organization of polyribosomes. These filaments could be considered as protein stockage, maybe from membranous origin, ready for use during segmentation. Several figures suggest that endocytotic vesicles and vacuoli constitute the source of the filamentous material.

Asunto(s)

RESUMEN

With the aid of scanning electron microscopy the normal pattern of both faces of amnion and visceral yolk sac were described. The inner face of the amnion turned towards the amniotic cavity is overlaid by large pavimentous cells bearing numerous microvilli. The opposite face, which delimits the exocoelome, consists of flattened fibroblasts separated by a fundamental connective substance. The two faces of the visceral yolk sac also show very different patterns. The exocoelomic face is covered by pavimentous cells ; these are smaller and bear less microvilli than amniotic cells. The yolk sac endoderm appears built up with prismatic or cubic cells, whose apical part is bulging and possesses a dense covering of microvilli. Amniocentesis effects are then reported. This intervention seems to provoke fetal membrane modifications only after 15 hours. These modifications essentially concern the visceral yolk sac whose exocoelomic cells are covered by more numerous microvilli which may show an intensification of a secretory process.

Asunto(s)

RESUMEN

Rat palatal shelves explanted on gestational day 15 or 16 are cultivated with their medial-edge epithelial surface in contact. Observations of histological sections showed that, before and during the fusion of the processes, mitotic activity is always lower in the epithelium of the expected fusion zone (EFZ) than in the oral epithelium and progressively decreases during the processus of the fusion.

Asunto(s)

RESUMEN

When slices of rat palatal shelves removed by dissection from 16 days 8 hours old fetuses, just before fusion, are treated by the periodic acid Schiff reaction (PAS), colored substances may be detected especially in the epithelium of the potential fusion zone; these substances are normally observed at the free surface of the epithelium. Our histochemical research, realized with the aid of the photonic microscope and of the transmission electron microscope, shows that most of the PAS positive material consists in glycogen; at the surface, this polysaccharide remains in the cytoplasm of flat degenerating cells and cannot be confused with the "cell coat" which presents no particularity, at this level, after demonstration by ruthenium red and by lanthanum nitrate.

Asunto(s)

RESUMEN

Amniotic epithelium of the rat has been studied during the eight last days of pregnancy, by scanning electron microscope analysis. The cells of this organ progressively become larger and flatter. Changes on their surface have also been observed : density of microvilli increases but single cilia disappear. These changes are related to modifications in the exchange processes.

Asunto(s)

RESUMEN

Normal fetuses 14 to 17 days old were obtained from female Wistar rats. The palates have been studied, after dissection, by scanning electron microscopy. Palatal closure is achieved, in the median and posterior region, by the elevation of the lateral palatine processus from a ventro-medial to a horizontal position; immediately after the horizontalization, they adhere to each other. Rostrally naso-palatine canal closure takes place later; it results from an epithelial and mesenchymal outgrowth under the nasal septum. The mutual adhesivity of the free edges of the lateral processes is noticeable. The pattern of the fusion surface has been considered, elements such as exfoliated cells, filopodes and microvilli are present. Their contribution to the adherence phenomenon is discussed.

Asunto(s)

RESUMEN

1) Amniotic sac puncture is a reliable procedure for induction of a cleft palate in rat foetuses 15 days old. 2) This possibility persists during the first hours of day 16. 3) When applied to rats after 16 days 12 hours of pregnancy, amniocentesis does't induce a cleft palate. 4) Treatment during this critical stage of pregnancy with substances able to reduce the amniotic fluid volume, such as acetazolamide and hydrocortisone, doesn't produce cleft palate.

Asunto(s)

RESUMEN

The pattern of the amniotic epithelium during the eight last days of pregnancy is described with the aid of scanning and transmission microscopy. A flattening of the cells appears near the term. Their area becomes progressively greater increasing their contact surface with the amniotic fluid. Simultaneaously, their microvilli become more numerous. During the 20th, the 21st and the 22nd days of pregnancy, we observed cytoplasmic processes emanating from the base of the cell interrupting the basal membrane and entering the underlying connective substance. No evidence of cell degeneration was seen.

Asunto(s)

Asunto(s)

RESUMEN

A large amount of glycogen can be detected in the cytoplasm of rat eggs; it is evenly distributed in all the cytoplasm of blastomeres and polar globules. During cleavage, eggs show non significative change in glycogen content. This polysaccharide was observed and identified in ultrathin sections. It exists in the form of beta particles.

Asunto(s)

RESUMEN

Two cell mouse and rat embryos are cultivated in vitro in the conditions described by Whitten, reducing the oxygen concentration in the gaseous phase at 5%. The first ones can become blastocysts while the second ones are stopped in their development.

Asunto(s)