Showing papers on "Apical cytoplasm published in 1968"

Reconstructions of Centriole Formation and Ciliogenesis in Mammalian Lungs

Abstract: This study presents reconstructions of the processes of centriolar formation and ciliogenesis based on evidence found in electron micrographs of tissues and organ cultures obtained chiefly from the lungs of foetal rats. A few observations on living cultures supplement the major findings. In this material, centrioles are generated by two pathways. Those centrioles that are destined to participate in forming the achromatic figure, or to sprout transitory, rudimentary (primary) cilia, arise directly off the walls of pre-existing centrioles. In pulmonary cells of all types this direct pathway operates during interphase. The daughter centrioles are first recognizable as annular structures (procentrioles) which lengthen into cylinders through acropetal deposition of osmiophilic material in the procentriolar walls. Triplet fibres develop in these walls from singlet and doublet fibres that first appear near the procentriolar bases and thereafter extend apically. When little more than half grown, the daughter centrioles are released into the cytoplasm, where they complete their maturation. A parent centriole usually produces one daughter at a time. Exceptionally, up to 8 have been observed to develop simultaneously about 1 parent centriole. Primary cilia arise from directly produced centrioles in differentiating pulmonary cells of all types throughout the foetal period. In the bronchial epithelium they appear before the time when the ciliated border is generated. Fairly late in foetal life, centrioles destined to become kinetosomes in ciliated cells of the epithelium become assembled from masses of fibrogranular material located in the apical cytoplasm. Formation of these centrioles may be under the remote influence of the diplosomal centrioles. More certainly, the precursor material accumulates in close proximity to Golgi elements. Within the fibrogranular areas, osmiophilic granules (400-800A) increase in size and eventually become consolidated into dense spheroidal bodies (deuterosomes), which organize the growth of procentrioles around them. When mature, the newly formed centrioles become aligned in rows beneath the apical plasma membrane. There each centriole produces satellites from its sides, a root from its base, and a cilium from its apex. Early stages in the formation of both primary cilia and those of the ciliated border are similar. In developing cilia of the ciliated border, however, the outer ciliary fibres rapidly reach the tips of the elongating shafts, and a central pair of fibres is formed (9 + 2 arrangement). In primary cilia, development of the fibres seems to lag behind the elongation of the shafts, and only the outer ciliary fibres appear (9 + 0 arrangement). The strengths and weaknesses of the proposed reconstructions of centriolar formation and ciliogenesis are discussed, and the occurrence in other living forms of similar pathways for centriolar formation is noted. Further discussion leads to an interpretation of the centriole as a semi-autonomous organelle whose replicative capacity is separable from the characteristic triplet fibre structure of its wall.

An electron microscopic study of ciliogenesis in developing epidermis and trachea in the embryo of Xenopus laevis

Abstract: This paper describes the ultrastructural phenomena occurring during the differentiation of cilia in the epidermis and trachea of Xenopus laevis. The sequence of developmental events seems to begin with the de novo formation of clusters of small, dense “procentriole precursor bodies” which are apparently transformed into procentrioles under the influence of dense amorphous masses here termed “procentriole organizers.” The procentriole so formed is a cylinder 150 mm in diameter with nine single microtubules in its wall which probably give rise to the nine “triplet” microtubles in the wall of the definite centrioles (200 mm in diameter). The appearance of multiple centrioles in the apical cytoplasm is correlated with disappearance of procentriole precursor bodies and procentrioles. Smooth-surfaced vesicles seemingly produced in the well developed Golgi zones may contribute to the development of the ciliary membrane. Following their formation in the supranuclear cytoplasm, the centrioles or presumptive basal bodies align with their longitudinal axes perpendicular to the apical plasmalemma. A ciliary shaft then appears distal to each basal body and simultaneously small, dense bodies like those termed “procentriole precursor bodies” reappear. At this time we call the dense bodies, “axonemal precursor bodies,” because they probably provide material for the synthesis of new axial microtubules at the tip end of the growing cilium. Centriolar rootlets develop during centriolar alignment and ciliary shaft formation from a distinct, low electron-opaque, precursor substance.

The uptake of ferritin by ileal absorptive cells in suckling rats. An electron microscope study.

Abstract: An electron microscopic study of the small intestine of rats from birth to 15 days of age has demonstrated a gradient of both structure and function along the length of the small intestine. During this period of development, only the ileum was found to absorb intact exogenous ferritin or colostral proteins. In newborn rats ferritin particles or milk proteins are incorporated by ileal absorptive cells into tubular invaginations of the apical plasmalemma which connect with vacuoles or cisternae in the apical cytoplasm. The ferritin particles are then transported by another vacuolar system to the supranuclear region where several such vacuoles coalesce to form a single supranuclear vacucle. After the first feeding the supranuclear vacuole is established in the ileal cells so that additional ingested proteins, whether ferritin or from milk, are transported from the cisternae directly to the supranuclear vacuole. There was no evidence in the present study to indicate that ferritin is transmitted from the ileal cell to the circulation. The subject of protein transport by the intestinal epithelium is reviewed briefly.

Follicle formation in the embryonic chick thyroid. II. Reorganization after dissociation.

Abstract: The events which occur after reaggregation of dissociated embryonic chick thyroid cells are described. Although the cells rearrange themselves into follicles within a few hours after being packed by centrifugation, their complex cytoarchitecture is not maintained. The first sign of an impending change is the accumulation of large numbers of dense bodies in the apical cytoplasm. Shortly thereafter other types of lytic bodies become numerous, and blebs containing cytoplasmic membranous components appear at the apical cell surfaces. A short time later the basal cytoplasm contains large residual bodies concomitant with a reduction in the extent of the canalicular endoplasmic reticulum and an increase in the number of free ribosomes. With the passage of time there is a progressive decrease in the size and number of residual bodies, and the channels of rough endoplasmic reticulum reappear until the normal thyroid pattern is restored. Lytic phenomena coupled with vesiculation of the endoplasmic reticulum have been linked with control of function in several organs. Therefore, the results are discussed in terms of a possible realtionship between lytic activity and the reestablishment of thyroid function after dissociation.

Fine structure and staining of mucosubstances on "intercalated cells" from the rat distal convoluted tubule and collecting duct.

Abstract: A second and previously unrecognized cell type which is identical to the intercalated cells of the collecting duct exists in the rat distal convoluted tubule. These cells are distinctly different from the principal cells which have long been recognized with light and electron microscopy. The intercalated cells have numerous irregular apical microvilli, a high concentration of nearly round mitochondria located in the apical cytoplasm, and a basal nucleus. A variety of coated and uncoated vesicles in the apical cytoplasm were identified by electron microscopy. The cytoplasmic surface of the apical plasmalemma also was studded with club-shaped densities. Light and electron microscopic histochemical techniques for acid mucosubstances were carried out on tissue prepared by rapid freezing techniques or intravascular perfusion fixation. The luminal surfaces of the cells from both the distal convoluted tubule and collecting duct stained for acid mucosubstances. In some cases, the intercalated cells stained more intensely with this technique than the adjacent principal cells. The apical cytoplasm of the intercalated cells was also more PAS positive than that of the principal cells.

Fibrillovesicular cells in the Fundic glands of the canine stomach: Evidence for a new cell type

Abstract: Biopsies of the gastric fundal mucosa were obtained from 25 dogs and processed for light and electron microscopy A cell distinguishable from superficial mucous, mucous neck, chief, parietal, or argentaffin cells was observed By light microscopy in resin-embedded, methylene-blue-stained sections, this cell was noted to have a prominent apical region which protruded into the gland lumen, a conspicuous terminal web traversed by parallel fibrils, and a crescent-shaped nucleus; secretory granules were absent By electron microscopy this cell had the following features: (1) short, stubby microvilli with well developed terminal web, (2) fibril-bundles constituting the cores of microvilli and extending through the apical cytoplasm to the paranuclear region, (3) characteristic vesicles and tubular structures in the apical cytoplasm, (4) spiral structures, and (5) oval dense bodies Morphological evidence supported the hypothesis that this is a distinct cell type; it is referred to as a fibrillovesicular (FV) cell

A Comparative anatomical study of the mammalian uterotubal junction

Abstract: Among eight species of mammals in this study (cattle, sheep, pig-tail and rhesus monkeys, rabbit, pig, rat, and dog) four basic patterns of anatomical structure at the uterotubal junction are described. The classification of types is based upon the presence or absence of an intramural portion of the oviduct and of isthmal folds or plicae projecting into the lumen of the uterine cornu. Histological variations are reported for three tissues: epithelial and connective of the mucosa and smooth muscle of the tunica muscularis. In the epithelium during the estrous cycle the differences recorded include: (a) absence of ciliated cells in the distal end of the oviduct in rat and dog; (b) variations in ciliated and nonciliated cells in (1) cell height, (2) location, shape and stainability of the nucleus, and (3) in amount and stainability of apical cytoplasm; (c) presence of lymphoblast-like cells which appear to migrate through the epithelium from the lamina propria. The connective tissue of the mucosa, as a circular layer and as cores for the mucosal folds, shows variations in thickness and in relative density of cells and fibers of the matrix. Emphasis is given to the presence of an inner longitudinal layer of smooth muscle in the tunica muscularis of the distal oviduct in six of the eight species.

Glycogen synthesis, storage and transport mechanisms in the yolk-sac membrane of the chick embryo.

Abstract: This paper deals with the relationship of structure and function in the yolk-sac membrane (YSM), a living "way station" between yolk and embryo of the chick. Through its parenchyma (entoderm) cells all yolk substances, either unchanged or enzymatically transformed into simpler metabolites, are transported to the blood of the growing embryo, wherein they are preeminently utilized as building blocks. Since glycogen must be derived from yolk and is readily visualized in entodermal cells (glycogenic cells of Claude Bernard) of the YSM it was chosen as a marker of functional activity.By a combination of methods of cytochemistry, radioautography and electron microscopy, glycogen localization in the entodermal cells and probable mode of glucose transport into the blood has been investigated during the middle third of embryonic life. The principal findings are: (1) Tritiated glucose injected into the yolk sac is incorporated into glycogen granules in the cytoplasm of entodermal cells. The labeled glycogen granules are arranged in circles about yolk spheres ("perilipid pattern") and in basal concentrations next to the plasma membrane ("basal pattern"). These patterns are identical to those obtained by the periodic acid Schiff test. (2) In electron micrographs glycogen commonly appears as tiny packets of rosettes typically disposed in the cytoplasmic matrix between the yolk spheres but not within them. Differences in patterns of glycogen-organelle organization between apex and base of the entodermal cell suggest a state of flux of glycogen in an apical-basal direction, to wit-from initial synthesis and deposition of glycogen in the apical cytoplasm, to an area rich in glycogen deposits associated with agranular ER, to a basal area of glycogen, ready for breakdown into glucose and transport to blood.Between the glycogen of the basal cytoplasm and the blood of the venous capillary is an ultrastructural complex of perivascular spaces and cell surface membranes having micropinocytic vesicles that are seemingly adapted for the transport of glucose or other metabolites to the blood as well as for the exchange of substances between the entodermal cells and the embryo. As to the mode of uptake of yolk substances from the yolk sac into the entodermal cells, it has been established for the first time thatwhole yolk spheres of different kinds are engulfed by the coalescence of the edge of a cup-shaped fold of the plasma membrane. Pinocytic vesicles of the cell surface membrane seem to provide devices for the uptake of soluble yolk substances.

Ultrastructure of the tubule of the aglomerular teleost Nerophis ophidion.

Abstract: The tubules in the aglomerular kidney of Nerophis ophidion are composed of cells showing different types of specializations of their plasma membrane. All cells possess a luminal brush border composed of microvilli, and show presence of vesicles with 100 A thick “unit” membranes — some containing electron dense material —, tubular elements, multivesicular bodies, and plasma membrane invaginations in their apical cytoplasm. These features suggest an absorptive function of the cells. The apical portions of the cells are supplied with typical cilia.

魚類消化管上皮のPear-shaped Cell (Rodlet Cell) について

Abstract: It is well known that so-called “pear-shaped cell” or “rodlet cell” is found to occur in the epithelium of the digestive tract of fishes. In the black rockfish, Sebastes inermis CUVIER, pear-shaped cells are frequently found among the columnar epithelial cells and goblet cells forming the lining epithelium of pyloric caeca (Figs. 1 and 2). Electron microscopy revealed that the cell is enclosed by a thick fibrous capsular wall (Fig. 3). Mitochondria are clustered in the apical cytoplasm. The nucleus is located at the basal end. A moderate amount of endoplasmic reticulum is scattered in the remainder of the cytoplasm as well as vesicles, vacuoles, and ribosomes. The rodlets lying parallel to the long axis of the cell are composed of three principal layers; dense central axis, moderately dense medullary part, and thin cortical layer (Fig. 3). Judging from the evidence of fine structure, it is conceivable that the pear-shaped cell is protozoan parasite, not a tissue cell. However, the taxonomic status of this peculiar parasite is uncertain.

A radioautographic comparison of glycerol-H3 and galactose-H3 uptake during intestinal glyceride synthesis.

Abstract: Radioautography was used to compare the in vivo incorporation of glycerol-H3 and galactose-H3 in intestinal absorptive cells in relation to glyceride synthesis. Each labeled compound was injected, either singly or mixed with linoleic acid chyme, directly into ligated segments of rat upper jejunum. The segments were removed at 5 and 20 minutes and prepared for light and electron microscopic radioautography. Following glycerol-H3 and chyme injections, label is rapidly incorporated in the vicinity of newly formed fat droplets in the apical endoplasmic reticulum. Later, labeled droplets accumulate in dilated Golgi cisternae and intercellular spaces. Galactose label is initially found in the Golgi region and later in the apical cytoplasm. Glycerol labeling is considerably reduced in the cells when the fat is extracted prior to radioautography, or when glycerol alone is absorbed. Galactose labeling is not affected by these procedures. The results indicate a significant incorporation of glvcerol label into newly synthesized glycerides, as previously also shown for glucose label. Galactose label follows a different metabolic pathway not related to glyceride synthesis.

Differentiation of alkaline phosphatase and glucose-6-phosphate dehydrogenase in rat yolk-sac.

Abstract: During early gestation in the rat, at the time of rapid embryonic differentiation and prior to the full formation of the chorioallantoic placenta, the function of ‘placental’ nutrition was attributed to the yolk-sac by Brunschwig (1927). Such a paraplacental function of the yolk-sac would assume that nutrients pass through the parietal wall into the yolk-sac cavity and thence into the embryo via the visceral yolk-sac epithelium and its underlying vitelline vessels. Supporting this concept were the findings of Everett (1935) who demonstrated in 13-day embryos that toluidine blue was able to pass into the omphalomesenteric vessels more rapidly than it could reach the umbilical veins via the chorioallantoic placenta. Furthermore, the visceral entodermal cells appeared to exert some selectivity in that trypan blue did not pass into the embryo but was localized in the apical cytoplasm. More recently, Padykula, Deren 9 Wilson (1966) demonstrated that the rat yolk-sac concentrated both vitamin B 12 and vitamin B 12 plus intrinsic factor throughout most of gestation.

Die licht- und sublichtmikroskopische Morphologie der Epidermis des neotenen Axolotls ( Siredon mexicanum Shaw)

Abstract: Three different cell types are the most frequent elements of the epidermis of the neotenic axolotl: (1) the common epidermal cells are small and multiform. They show bundles of tonofilaments (figures ofEberth) in the stratum basale. (2) The big Leydig cells contain numerous gross granules and a special network in the peripheral cytoplasm (Langerhans net). (3) The cover cells forming the outer layer of the epidermis possess a striking mucin zone in the apical cytoplasm.