Apical cytoplasm

About: Apical cytoplasm is a research topic. Over the lifetime, 1080 publications have been published within this topic receiving 36131 citations.

The aglomerular nephron of antarctic teleosts: a light and electron microscopic study.

Abstract: Complete serial sections demonstrated that ten species of Antarctic teleost fishes representing two families had aglomerular kidneys. The aglomerular nephron of such kidneys consists of two distinct regions: (1) a highly contorted principal segment and (2) a system of collecting tubules and ducts. Throughout the principal segment the cells are characterized by densely packed microvilli and a single cilium projecting into the lumen. Within the cytoplasm, lysosomes are rarely encountered, as would be expected if there is little or no reabsorption of protein from the urine. At the base of these cells, the plasma membrane is prominently infolded in close association with abundant mitochondria. The overall fine structure of the principal segment cells is consistent with their probable function in the secretion of ions into the formative urine. Between the principal segment and the collecting tubule is a very short transitional zone characterized by transitional mucus cells and multiciliated cells. The collecting tubule and duct system is lined entirely by mucus cells. In comparison with principal segment cells, the mucus cells have a well-developed Golgi complex and abundant secretory granules in the apical cytoplasm; these granules presumably contain the non-sulfated acid mucopolysaccharide demonstrable by light microscopic histochemistry

Renal tubule of dogfish, Scyliorhinus caniculus: a comprehensive study of structure with emphasis on intramembrane particles and immunoreactivity for H(+)-K(+)-adenosine triphosphatase.

Abstract: The ultrastructure of renal tubule cells was studied in the European lesser spotted dogfish by the evaluation of thin sections and freeze fracture replicas. Computer-assisted three-dimensional reconstruction of entire nephrons was performed. The distinction of nephron segments and collecting tubule was made using results of previous histological work. The first proximal tubule segment (PI) consists of two subsequent portions, PIa and PIb. PIa is a component of the lateral countercurrent bundle, and PIb, which displays an apical tubulovesicular apparatus and an extended lysosomal compartment, is located in the vicinity of the glomeruli. Rod-shaped intramembrane particles were detected in PIa. The second proximal tubule segment (PII) is a special segment in elasmobranch and teleost fish. PII differs largely from PI in cell morphology and function. The apical cytoplasm was filled with small clear vesicles, and an apical endocytic apparatus was lacking. In the apical cell membrane, rod-shaped particles were revealed by freeze fracture. The apical tight junctions of PI and PII consisted of seven to ten meandering strands. The distal nephron was subdivided into two major segments: early distal tubule (EDT) in the lateral countercurrent bundles and late distal tubule (LDT) in the mesial tissue. The EDT showed marked amplification of basolateral cell membranes. The tight junctions displayed a low number of continuous parallel strands, which is also characteristically found in the diluting segments of other vertebrates. LDT cells showed cytoplasmic studs and rod-shaped intramembraneous particles at the apical cell membrane, thereby resembling type A intercalated cells of collecting duct. The collecting tubule (CT) emerged from the LDT and was part of the countercurrent arrangement inside the lateral bundles. Tight junctions of LDT and CT consisted of many meandering strands in a honeycomb pattern. With immunohistochemistry, binding sites of a polyclonal antibody against an extraplasmic portion of rat gastric H(+)-K(+)-adenosine triphosphatase (ATPase) were observed at the apical cell membrane of PIa, PII, and LDT. From the colocalization of binding sites for the antibody against the transport enzyme with rod-shaped intramembrane particles, we assume that these might be the morphological correlate of gastric H(+)-K(+)-ATPase-like enzyme in the renal tubule.

Phospholipase A2-induced pathophysiologic changes in the guinea pig lung.

Abstract: The pathophysiology of lung injury induced by phospholipase A2 (PLA2), a lipolytic enzyme implicated in a variety of pulmonary diseases, was examined in the guinea pig. One hundred microliters of saline or 10 units of PLA2 suspended in saline was given as a bolus injection into either the trachea or jugular vein. Intratracheal pressure and mean arterial blood pressure were continuously monitored. The lungs were examined by light and transmission electron microscopy at 1, 10, and 30 minutes after administration. Pulmonary morphologic and physiologic changes were only observed in animals that received PLA2 via the trachea. Significant increases in peak intratracheal pressure occurred as early as 1 minute after intratracheal PLA2 administration. Morphologic evidence of airway constriction, accompanied by blebbing of the apical cytoplasm of airway epithelium, was also observed at this time. A transient increase in mean arterial blood pressure occurred 5 minutes after challenge. At 10 minutes after intratracheal PLA2, there was marked swelling of airway epithelial cells, pronounced blebbing of the apical cytoplasm, and a resultant decrease in size of the airway lumen. Morphologic changes in alveolar cell populations were initially observed 10 minutes after intratracheal PLA2. Interalveolar septa were hypercellular and multifocally thickened. There was prominent perivascular edema and alveolar spaces contained abundant proteinaceous material and occasional hemorrhage. Ultrastructurally, there was marked cell swelling and fragmentation of type I alveolar epithelium resulting in a denuded basal lamina. Sequestration of neutrophils and eosinophils, many of which lacked secretory granules, within alveolar capillaries was accompanied by aggregates of platelets and was observed in close proximity to injured endothelium. Morphologic changes indicative of cell injury were also observed in type II alveolar epithelium. Similar, but more frequent and severe, morphologic injury occurred 30 minutes after intratracheal PLA2. It is concluded that PLA2 induces pronounced morphologic and physiologic changes in the guinea pig and that the route of administration is important in the development of PLA2-induced lung injury.

Uptake of maternal immunoglobulins in the enterocytes of suckling piglets: improved detection with a streptavidin-biotin bridge gold technique.

Abstract: In ungulates, intestinal absorption of maternal immunoglobulins from colostrum plays a vital role in the acquisition of passive immunity during early neonatal life. In the present study we used post-embedding colloidal gold labeling to examine the intracellular localization of IgG in the jejunal enterocytes of miniature piglets suckled for 2 hr. Quantitation of the immunolabeling revealed that the most sensitive technique for IgG detection was the streptavidin bridge-gold technique. In this method, the LR White-embedded sections were labeled sequentially with biotinylated anti-porcine IgG, streptavidin, and biotinylated BSA conjugated to 10-nm colloidal gold. With this approach, we found the following sequence of maternal IgG accumulation: passage of IgG from colostrum through the brush border; binding to the apical plasma membrane; uptake in noncoated pits and invaginations; transport in endocytotic vesicles; and accumulation in granules in the apical cytoplasm.

Histochemical study of Magellanic penguin (Spheniscus magellanicus) minor salivary glands during postnatal growth

Abstract: The histological and histochemical features of the minor salivary glands during postnatal development have been generally associated with the type of food ingested. However, recent studies support the fact that these salivary glands develop independently of the diet; in fact, minor salivary glands have similar morphological and histochemical characteristics in adult individuals of species with different diet regimens. Thus, the aim of this study was to characterize the developmental morphology of the penguin minor salivary glands and to contrast them with minor salivary glands of other species. The tongue, palatine, and mouth cavity (bottom) minor salivary glands of newborn, 1- to 20-day-old, and adult magellanic penguins were studied with hematoxylin–eosin, periodic acid–Schiff, alcian blue, toluidine blue, and lectin histochemistry. Minor salivary glands were present at all ages, although they were only moderately developed in animals less than 15 days old. After this age, glands were abundant in all age groups; in addition, cells from the glandular epithelium were functionally mature and secreted mucins. Nevertheless, in newborn to 15-day-old penguins, mucins were located only at the apical cytoplasm of mucous cells. In all ages, mucous cells displayed periodic acid–Schiff-positive, alcianophilic, and metachromatic reactions; among mucous cells, other orthochromatic cells appeared interspersed. From 15 days on, histochemical reactions became more intense until adulthood, and the cytoplasm of secretory cells was filled with glycoproteins and sulfomucins. Moreover, lectins bound to different oligosaccharides in mucous cells, depending on the stage of maturation of the glands. In conclusion, penguin minor salivary glands are already present at birth, and show progressive and quantitative increases in mucous secretionduring postnatal development. These changes are necessary not only for nutrient ingestion, but also for nonimmune protection of the buccal cavity. Anat Rec 254:298–306, 1999. © 1999 Wiley-Liss, Inc.