Study of polysaccharides present in palatal shelves of rats shortly before their fusion

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

Scanning electron microscope study of the secondary palate during embryonic formation in the rat

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

So-called lamellar structures in non-fertilized rat ovum

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

Changes in the fetal membranes of the rat after amniocentesis - preliminary observations

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

Binding of cationized ferritin to the surface of the palatine crest in the rat

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

Histophysiological modifications of the amnion in the rat at the end of gestation

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

Ultrastructural study of the effects of neuraminidase on the palatine process of the rat

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

Scanning and transmission electron microscope study of the amniotic epithelium in the rat at the end of gestation

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