Showing papers on "Apical cytoplasm published in 1972"

Effects of puromycin on the structure of rat intestinal epithelial cells during fat absorption.

Abstract: This report provides information on the morphology of rat intestinal epithelial cells during fat absorption. In addition, the role of protein metabolism in this process has been evaluated by blocking its synthesis with puromycin and studying the fine structure of mucosal cells from rats at various times after fat intubation. The results indicate that SER-derived vesicles, containing fat droplets, migrate from the apical cytoplasm of the absorptive cell and fuse with saccules or vacuoles of the Golgi complex. Arguments are made that the Golgi complex is important in completing chylomicron formation and in providing appropriate enveloping membranes for the chylomicron. Such membranes may be necessary for Golgi vacuoles to fuse with the lateral cell membranes and release chylomicra. Puromycin treatment causes the absorptive cell to accumulate increased quantities of lipid that are devoid of membrane during fat absorption. In addition, puromycin-treated cells contain much less RER and Golgi membranes are strikingly decreased in number. In this paper we discuss the consequences of these abnormalities and suggest that continued protein synthesis by the RER is required in order to generate Golgi membranes. If such membranes are absent the cell's ability to discarge chylomicra is impaired and lipid accumulates.

The relationship of ultrastructural and cytochemical features to absorptive activity in the goldfish intestine.

Abstract: In the adult goldfish, Carassius auratus (a stomachless freshwater teleost), there is a striking proximal-to-distal gradient in the microscopic appearance of the intestine. This gradient is correlated, moreover, with differences in the site of absorption of lipid and protein. The proximal regions (intestinal bulb and anterior intestine) have a greater surface area, manifested by elongated mucosal ridges in which the epithelial cells have regularly arranged closely spaced microvilli. The distal region (posterior intestine) has less overall surface area, but the epithelium exhibits the typical ultrastructural features of pinocytosis, namely extensive invagination of the luminal surface membrane and massive accumulation of vesicles and vacuoles in the apical cytoplasm. In addition, a conspicuous PAS-positive supranuclear “body” is visible with the light microscope. Administered triglyceride is absorbed exclusively by the epithelium of the anterior regions, where presumably, it must be hydrolyzed prior to uptake. Protein (horseradish peroxidase), on the other hand, is absorbed primarily in the most distal region, where the epithelium appears to be equipped for the uptake of large intact molecules. These regional differences are discussed in relation to comparable differences in the mammalian intestine, especially during development.

Ultrastructure of the outer epithelium of the mantle in the clam Mercenaria mercenaria in relation to calcification of the shell.

Abstract: The general outer epithelium of the mantle in the clam Mercenaria mercenaria is composed of tall narrow columnar cells characterized by densely packed apical microvilli, convoluted lateral and basal cell membranes and abundant mitochondria in the apical and 'basal cytoplasm. Cells are joined apically by a zontila adherens followed by a septate desmosome. Small calcium-rich granules fill the intercellular spaces and are also present in small vesicles in the apical cytoplasm and the mierovilli. Amoebocytes in the subepithelial connective tissue also contain granulefilled vacuoles. Soluble calcium was detected histochemically in the intercellular spaces but not intracefularly. The possible routes of calcium flux through the outer epithelium of the mantle are discussed.

The ultrastructure of neonatal calf intestine and absorption of heterologous proteins

Abstract: The ultrastructural morphology of the jejunal and ileal cells of newborn calves was similar to the intestinal absorptive cells of other newborn ungulates. Microvilli were well developed, tubules or invaginations in the apical cytoplasm were extensive. Large supranuclear vacuoles were limited to the ileal cells. After injection of ferritin-IgG or ferritin into ligated intestinal loops, the ferritin particles were found around the microvilli and within the tubular system. After 2-6 hours ileal vacuoles containing ferritin were found near the basal membrane. In the jejunal cell ferritin was found only in the tubules. No ferritin could be detected in calf sera after injection into the intestinal loops. To establish that heterologous proteins were absorbed, calves were given human serum via stomach tube and their sera subsequently was found to contain circulating levels of human albumin and gamma globulin. Also newborn pigs and suckling rats also were given ferritin; but it could not be detected in their sera. The results of these experiments suggest that while the neonatal intestine is permeable to some het-erologous proteins, ferritin is not transported across the absorptive cell into the circulation.

Cytoplasmic filaments and morphogenesis: effects of cytochalasin B on contractile epidermal cells.

Abstract: During tail resorption in Distaplia occidentalis the caudal epidermis contracts to 8.5% of its initial length in about 6 minutes and forces the axial complex (muscle, notochord and nerve cord) into a coiled configuration in the trunk. The contraction of the caudal epidermal cells is accompanied by rapid alignment of arrays of circa 50 A (diameter) filaments parallel to the axis of contraction in the apical cytoplasm of each epidermal cell. Normal metamorphosis (including tail resorption) can be instantly induced by treating tadpole larvae with 0.5% dimethylsulfoxide. Cytochalasin B, (CCB) > 0.25 μg/ml rapidly inhibits contraction of the caudal epidermis. The tail stops shortening, then partly re-extends. When CCB is removed by washing immediately after relaxation, tail resorption resumes. Cytochalasin B reversibly disrupts the organization of central and subterminal arrays of apical filaments in the contractile caudal epidermal cells. Membrane associated filaments near the junctional complexes are not disrupted by 0.25–1.0 μg/ml of CCB. This suggests that CCB does not degrade the filaments into subunits. It is more likely that CCB blocks contraction by disrupting the binding forces between overlapping filaments and facilitates the disorganization of unattached filaments. A second type of filament with a fusiform configuration has been detected in the epidermal cells after CCB treatment. The possibility that these are myosinoid proteins is considered. The data presented in this paper strengthen the hypothesis that the filaments in the epidermal cells are part of a contractile apparatus.

The effect of lithium carbonate on the structure of the rat kidney

Abstract: Female Sprague-Dawley rats were used to study effects of lithium carbonate on the ultrastructure of the rat kidney. Experimental rats received daily intraperitoneal injections of lithium carbonate in dosages of 10, 30 or 100 mg/kg/day. These animals were killed on day 12 to 60. Control rats were either non-injected or injected with either sodium chloride or sodium carbonate. Kidneys from control rats showed no abnormal changes. The 10 and 30 mg/kg lithium carbonate dosages caused progressive mitochondrial swelling, dilatation of cisternae of rough endoplasmic reticulum and occasional swelling of apical cytoplasm in tubular cells localized in the distal portion of the nephron. The 100 mg/kg lithium dosage produced damage in all portions of the nephron. However, the most severe damage, consisting of mitochondrial swelling, dilatation of the rough endoplasmic reticulum, apical cytoplasmic rarefaction and liquefaction, karyolysis and karyorrhexis was noted in the distal convoluted tubules and collecting ducts. The present study demonstrated that low dosages of lithium carbonate do affect the structure of the rat kidney.

Surface modifications of neural epithelial cells during formation of the neural tube in the rat embryo.

Abstract: The apical (juxtaluminal) ends of the neural epithelial cells of rat embryos were examined using light and electron microscopy during varying stages of neural tube formation. At the neural-plate stage the apical surfaces exhibit numerous microvilli. At the presomite neurula stage the microvilli are longer and more irregular. Filaments of approximately 40–60 A diameter appear in the apical cytoplasm. By the neural-groove stage, cytoplasmic protrusions containing various organelles have begun to appear. Apical filaments are present. At the beginning of closure the apical surfaces are characterized by large, irregular protrusions that are still associated with apical filaments. Finally, at the time of neural closure, the apical protrusions as well as the apical filaments have disappeared and the apical surfaces of the neural epithelial cells are relatively smooth. These observations bear out the proposal that contraction of the apical filaments is responsible for the folding of the neural plate and the production of apical protrusions.

Electron microscope studies of the stria vascularis and spiral ligament after ferritin injection.

Abstract: Electron microscope studies of the transport and diffusion of macromolecules across the lateral wall of the cochlear duct were made after endolymphatic or perilymphatic injection of ferritin. After endolymphatic injection, the cells of the attachment zone of Reissner' membrane, the marginal cells of the stria vascularis, and cells of the spiral prominence and external sulcus absorbed the tracer but do not transport it across their cytoplasm. No ferritin was ever found in the spiral ligament. After ferritin injection into the perilymph the tracer was found in the spiral ligament and in the endothelial cells and lumen of the spiral ligament capillaries. Also it was found in cells of the attachment zone of Reissner' membrane, spiral prominence and external sulcus. In the stria vascularis ferritin was found only in the apical cytoplasm of the marginal cells. This was explained by transport from perilymph to endolymph across Reissner' metibrane. The functional significance of these findings were discussed.

Protein transport in mouse kidney utilizing tyrosinase as an ultrastructural tracer.

Abstract: The morphological basis of glomerular filtration and protein reabsorption in mouse kidney was examined by using mushroom tyrosinase subunits (mol wt 34,500), as an ultrastructural tracer. Almost immediately after injection tyrosinase reaction product was visualized in the glomerulus, and within the capillary lumen extending into the endothelial fenestrae. The entire basement membrane showed accumulations of tyrosinase in the subendothelial and subepithelial layers. The urinary space contained considerable amounts of reaction product, some of which was adsorbed to the cell coat of the podocytes. Reaction product could also be seen in the brush border region of the proximal tubule cells. By 30 min after injection, no tyrosinase reaction product was demonstrable in the glomerulus except for dense vesicles in mesangial cells. Most of the reaction product was localized in absorption droplets in the apical cytoplasm of proximal tubule cells. Occasionally, some tyrosinase reaction product was present within the basal infoldings of these cells. The behavior of tyrosinase in the mouse kidney is in accordance with that of other low molecular weight tracers. The pattern of localization within the basement membrane provides additional support for the presence of two filtration barriers in the glomerulus. The adherence of tyrosinase to the cell coat of the glomerular epithelial cells suggests that this may be an additional mechanism whereby protein is removed from the glomerular filtrate. Tyrosinase subunits may prove to be a useful new tracer for the study of protein transport.

Light and electron microscopic studies on the gastrointestinal tract of the suckling echidna (Tachyglossus aculeatus).

Abstract: The stomach of the suckling echidna is lined by a tall columnar epithelium that is bounded basally by a delicate basement membrane. Adjacent cells are held in close apposition by tight junctions near the apex and by extensive implications of the remaining lateral surfaces. The basal cell surface is smooth and without apparent specialization. The lining epithelium is characterized by an abundance of mitochondria and a relative paucity of other organelles. Scattered argentaffin cells extend between the bases of the gastric lining cells and rest upon the luminal side of the basement membrane. Absorptive cells lining the small intestine of the suckling echidna exhibit in-vaginations of the apical plasma membrane which branch and anastomose, forming a dense network of tubules in the apical cytoplasm. Adjacent to this network is a series of small vacuoles of varying diameters which come into direct relation with a single, large, supranuclear vacuole. The vacuolar system contains both a fine granular substance and clusters of a flocculent amorphous material thought to be of a proteinaceous nature. The surrounding cytoplasm contains numerous profiles of smooth endoplasmic reticulum, several Golgi systems, and a relative abundance of mitochondria. Clusters of homogeneous droplets are found in the cytoplasm and in the intercellular space.

Cephalic Glands in Sea Snakes (Pelamis, Hydrophis and Laticauda)

Abstract: Laticauda colubrina, Hydrophis ornatus and Pelamis platurus (Hydrophiidae) were investigated to determine the distribution and structure of their cephalic glands. Marine snakes do not possess glands not found in land snakes. All species of sea snakes examined possessed well developed Harderian, sublingual, anterior sublingual and venom glands. Labial glands were poorly developed laterally and there was a rostral expansion and enlargement of the supralabial in the premaxillary region. The nasal gland decreases in size as extrarenal salt secreting ability increases. P. platurus does not have a well developed nasal gland but its presence is confirmed in the serial sections of the head. Well developed nasal glands are present in H. ornatus and in L. colubrina. Mucoid cell types are found in the labial glands of L. colubrina and H. ornatus, but not in P. platurus. Secretion product when present and secretory granules in apical cytoplasm of cells in the labial glands are PAS-positive. The nasal and anterior sublingual glands are weakly PAS-positive in apical cell cytoplasm. The posterior sublingual is a single, elongate PAS-negative serous gland with scattered PAS-positive acini in its most anterior aspect. The paired anterior sublinguals are small serous glands with cuboidal secretory epithelium and no visible secretory product. The paired serous Harderian glands are PAS-positive with no mucoid cell types or visible secretory product. The venom glands are compartmentalized and contain cuboidal, columnar and mucoid cell types. Accessory venom glands were present in each species, circumscribing the main duct in the suborbital region.

A fine structural study of the highly active thyroid follicular cell of the African basenji dog.

Abstract: The highly active thyroid gland of the basenji dog has been studied. The follicular cell of the basenji thyroid is unusual in that colloid droplets may be found in the apical cytoplasm of normal cells. Their appearance does not require administration of exogenous thyrotrophin. The colloid droplets appear to have been taken in by invagination of the apical plasma membrane forming a small bay at the cell-colloid interface. Apparent fusion of adjacent plasma membranes subsequently eliminates the mouth of the bay, completing endocytosis of the droplet. Basenji follicular cells are also distinguished by a dense accumulation of two varieties of lysosomes, basal associations of lip d droplets and mitochondria with unusual cristae and specialized junctions between cells of adjacent follicles. It is suggested that these unique structural modifications reflect adaptations for the perpetually active state of the basenji thyroid.

Ultrastructural and Cytochemical Studies on the Thyroid Gland of Normal Metamorphosing Frogs (Rana japonica Guenther)

Abstract: The peroxidase activity in the thyroid gland of developing frogs, Rana japonica Guenther, has been observed in the course of metamorphosis. The enzyme first appears in the vesicles near the Golgi complex or near the plasma membrane and sometimes in the cisternae of the inner parts of Golgi lamellae in the early premetamorphosis. As cytoplasmic organelles develop, the density of the reaction product and the number of positively reacted vesicles increase gradually. During climax metamorphosis, the peroxidase activity reaches its maximum. The reaction product is found in the numerous vesicles and multivesicular bodies at the apical cytoplasm, and many vesicles and the cisternae of a few inner lamellae of the Golgi complex. Figures showing reverse pinocytosis of the apical peroxidase positive vesicles into the follicular lumen are often seen.Four tadpoles at stage XX and XXI were kept in water containing 125I for 2 or 50hrs, and sacrificed. After the technique for the cytochemical demonstration of endogeneous peroxidase activity, autoradiographic procedures were performed for simultaneous demonstration of peroxidase reaction and silver grains of 125I were mostly localized on the colloid lumen and few were found on the peroxidase positive vesicles in the cytoplasm. It is suggested that the apical cell membrane region and peripheral colloid lumen are the major sites of iodination of thyroglobulin.