scholarly journals Distribution of secretory component in hepatocytes and its mode of transfer into bile

1980 ◽  
Vol 190 (3) ◽  
pp. 819-826 ◽  
Author(s):  
Barbara M. Mullock ◽  
Richard H. Hinton ◽  
Miloslav Dobrota ◽  
Jane Peppard ◽  
Eva Orlans
Keyword(s):  
Particle Size ◽  
Plasma Membrane ◽  
Electron Microscope ◽  
Immunoglobulin A ◽  
Secretory Component ◽  
The Other ◽  
Marker Enzymes ◽  
Liver Homogenates ◽  
Fraction Bound

Immunoglobin A in bile and other external secretions is mostly bound to a glycoprotein known as secretory component. This glycoprotein is not synthesized by the same cells as immunoglobulin A and is not found in blood. We now report the mechanism by which secretory component reaches the bile and describe its function in immunoglobulin A transport across the hepatocyte. Fractionation of rat liver homogenates by zonal centrifugation was followed by measurement of the amounts of secretory component in the various fractions by rocket immunoelectrophoresis. Secretory component was found in two fractions. One of these was identified as containing Golgi vesicles from its isopycnic density and appearance in the electron microscope; the other contained principally fragments of the plasma membrane of the sinusoidal face of the hepatocyte, as shown by its particle size and content of marker enzymes. Only the latter fraction bound 125I-labelled immunoglobulin A added in vitro. At 5min after intravenous injection of [14C]fucose, the secretory component in the Golgi fraction was labelled, but not that in the plasma membrane. The secretory component in the sinusoidal plasma membrane did, however, become labelled before the first labelled secretory component appeared in bile, about 30min after injection. We suggest that fucose is added to the newly synthesized secretory component in the Golgi apparatus. The secretory component then passes, with the other newly secreted glycoproteins, to the sinusoidal plasma membrane. There it remains bound but exposed to the blood and able to bind any polymeric immunoglobulin A present in serum. The secretory component then moves across the hepatocyte to the bile-canalicular face in association with the endocytic-shuttle vesicles which carry immunoglobulin A. Hence there is a lag before newly synthesized secretory component appears in bile.

scholarly journals Effects of cytoplasmic acidification on clathrin lattice morphology.

1989 ◽  
Vol 108 (2) ◽  
pp. 401-411 ◽  
Author(s):  
J Heuser
Keyword(s):  
Plasma Membrane ◽  
Cultured Cells ◽  
Membrane Receptors ◽  
The Other ◽  
Culture Dish ◽  
Initial Curvature ◽  
Internal Ph ◽  
Cytoplasmic Acidification

Reducing the internal pH of cultured cells by several different protocols that block endocytosis is found to alter the structure of clathrin lattices on the inside of the plasma membrane. Lattices curve inward until they become almost spherical yet remain stubbornly attached to the membrane. Also, the lattices bloom empty "microcages" of clathrin around their edges. Correspondingly, broken-open cells bathed in acidified media demonstrate similar changes in clathrin lattices. Acidification accentuates the normal tendency of lattices to round up in vitro and also stimulates them to nucleate microcage formation from pure solutions of clathrin. On the other hand, several conditions that also inhibit endocytosis have been found to create, instead of unusually curved clathrin lattices with extraneous microcages, a preponderance of unusually flat lattices. These treatments include pH-"clamping" cells at neutrality with nigericin, swelling cells with hypotonic media, and sticking cells to the surface of a culture dish with soluble polylysine. Again, the unusually flat lattices in such cells display a tendency to round up and to nucleate clathrin microcage formation during subsequent in vitro acidification. This indicates that regardless of the initial curvature of clathrin lattices, they all display an ability to grow and increase their curvature in vitro, and this is enhanced by lowering ambient pH. Possibly, clathrin lattice growth and curvature in vivo may also be stimulated by a local drop in pH around clusters of membrane receptors.

An improved polarized rat hepatoma hybrid cell line. Generation and comparison with its hepatoma relatives and hepatocytes in vivo

1994 ◽  
Vol 107 (4) ◽  
pp. 813-825 ◽  
Author(s):  
M.R. Shanks ◽  
D. Cassio ◽  
O. Lecoq ◽  
A.L. Hubbard
Keyword(s):  
Plasma Membrane ◽  
B Cells ◽  
Membrane Proteins ◽  
Cell Line ◽  
Hybrid Cell ◽  
The Other ◽  
Hepatocyte Polarity ◽  
Rat Hepatoma

Studies of hepatocyte polarity, an important property of liver epithelial cells, have been hampered by the lack of valid in vitro models. We report here that a new polarized hepatoma-derived hybrid cell line, called WIF-B, has improved characteristics to those of its parent, WIF12-1. This latter line originated from the fusion of non-polarized rat hepatoma Fao cells with human fibroblasts (WI-38) and selection for a polarized phenotype. We generated the WIF-B line by growing WIF12-1 cells as unattached aggregates for three weeks and selecting for survivors. Karyotype analysis showed a broad chromosome pattern in the initial WIF-B population, but this pattern stabilized after a few passages. The growth and phenotypic properties of these cells were quite different from those of their polarized WIF12-1 parent. WIF-B cells attained a 4-fold higher maximal density in monolayer culture, survived at this density for > 5 days rather than 1 day, and exhibited two to three times more apical structures during this period (80 to 95%). We compared several parameters of liver differentiation in the WIF-B cells with those of a related hybrid clone, WIF12-E, which is extinguished for most liver-specific functions, and with the common hepatoma parent, Fao. By immunoblot analysis, the levels of expression of eight plasma membrane proteins were higher in the WIF-B cells than in either of the other two cell lines and ranged from 10 to 200% of those in vivo. Two plasma membrane proteins were not detected in WIF12-E cells. By immunofluorescence, the apical membrane proteins in WIF-B displayed different cellular localizations than in either of the other two cell lines. In WIF-B cells, apical proteins were confined to a plasma membrane region that we have identified as the apical domain by several criteria (Ihrke, G., Neufeld, E.D., Meads, T., Shanks, M.R., Cassio, D., Laurent, M., Schroer, T.A., Pagano, R. E. and Hubbard, A. L. J. Cell Biol., 123, 1761–1765). The same molecules were distributed over the entire plasma membrane of Fao and WIF12-E cells and also (for Fao cells) in intracellular punctate structures that did not colocalize with the majority of structures containing a secretory protein, albumin. Our results indicate that the WIF-B cells are more highly differentiated than any of their ancestors (Fao or WIF12-1 cells) and thus, are promising candidates for in vitro studies of hepatocyte polarity.

scholarly journals Species differences in the metabolism and excretion of sulphasomidine and sulphamethomidine

1969 ◽  
Vol 111 (2) ◽  
pp. 173-179 ◽  
Author(s):  
J W Bridges ◽  
S R Walker ◽  
R T Williams
Keyword(s):  
Partition Coefficients ◽  
Species Differences ◽  
Species Difference ◽  
Acetyl Derivative ◽  
The Other ◽  
Main Metabolite ◽  
Monkey Liver ◽  
Liver Homogenates

1. The excretion of 2,4-dimethyl-6-sulphanilamidopyrimidine (sulphasomidine; Elkosin) and 4-methoxy-2-methyl-6-sulphanilamidopyrimidine (sulphamethomidine) given orally was examined in man, rhesus monkey, rabbit and rat. 2. About 70% of sulphasomidine (0·1g./kg.) is excreted mainly unchanged in the urine by these species in 24hr.; less than 15% of the dose is acetylated and there is no marked species difference in the fate of this drug. 3. Sulphamethomidine is excreted more slowly than sulphasomidine, and in the rat, rabbit and monkey the main metabolite is the N4-acetyl derivative. In man, only 20–30% of the dose is excreted in 24hr. and nearly 70% of this is sulphamethomidine N1-glucuronide, which is also excreted by the monkey but not by the rat or rabbit. There is therefore a marked species difference in the metabolism of sulphamethomidine. 4. Sulphamethomidine N1-glucuronide was synthesized and shown to be identical with the glucuronide isolated from monkey urine. 5. Sulphasomidine, sulphamethomidine and sulphadimethoxine (2,4-dimethoxy-6-sulphanilamidopyrimidine) were acetylated by rabbit or monkey liver homogenates. Although sulphasomidine is poorly acetylated in vivo, it is acetylated in vitro at rates comparable with those of the other two drugs. 6. The solubilities, partition coefficients and plasma-protein-binding of the drugs were measured. 7. The results are discussed.

scholarly journals Ca2+-dependent and Ca2+-independent degradation of phosphatidylinositol in rabbit vas deferens

1981 ◽  
Vol 194 (1) ◽  
pp. 129-136 ◽  
Author(s):  
K Egawa ◽  
B Sacktor ◽  
T Takenawa
Keyword(s):  
Smooth Muscle ◽  
Plasma Membrane ◽  
Vas Deferens ◽  
The Other ◽  
Ionophore A23187 ◽  
K Concentration ◽  
Rabbit Vas Deferens ◽  
Dependent Mechanism ◽  
Stimulation Of

The effects of Ca2+ and acetylcholine on the degradation and synthesis of phosphatidylinositol in rabbit vas deferens was studied in vitro by a pulse–chase technique and by measuring the content of the phospholipid in the tissue. Ca2+-dependent degradation of phosphatidylinositol was found in slices and homogenates prelabelled with myo-[2-3H]inositol. The phosphatidylinositol content of the slices also decreased by a Ca2+-dependent mechanism. On the other hand, removal of intracellular Ca2+ with the ionophore A23187 and EGTA increased the amount of phosphatidylinositol. These results indicate that the intracellular Ca2+ concentration has an important role in regulating the phosphatidylinositol content of the tissue. Increasing the extracellular K+ concentration, which causes an increase in plasma-membrane Ca2+ permeability, did not enhance phosphatidylinositol breakdown nor decrease its tissue content. However, phosphatidylinositol synthesis was clearly inhibited. After stimulation of the smooth muscle with acetylcholine, degradation of phosphatidylinositol was enhanced. Furthermore, the content of phosphatidylinositol in the tissue also decreased. These phenomena were evident even in the absence of Ca2+. The acetylcholine-induced degradation of phosphatidylinositol was blocked by the muscarinic antagonist atropine, but not by the nicotinic antagonist (+)-tubocurarine. The acetylcholine-induced decrease in the phosphatidylinositol content of the tissue led to the compensatory synthesis of phosphatidylinositol. Synthesis was separated from degradation in the same tissue. Compensatory synthesis was inhibited by acetylcholine. The degradation of phosphatidylinositol induced by acetylcholine was not inhibited by 8-bromoguanosine 3′:5′-cyclic monophosphate, indicating that the degradative process was not mediated by an increase in the cyclic nucleotide.

scholarly journals Formulation, Characterization and in-vitro Evaluation of Famciclovir Loaded Solid Lipid Nanoparticles for Improved Oral Absorption

2020 ◽  
pp. 1-17
Author(s):  
Pavan Kumar Rawat ◽  
Chandra Kishore Tyagi ◽  
Sunil Kumar Shah ◽  
Arun Kumar Pandey
Keyword(s):  
Particle Size ◽  
Electron Microscope ◽  
Solid Lipid Nanoparticles ◽  
Lipid Nanoparticles ◽  
Spherical Particles ◽  
Average Particle ◽  
Preparation Technique ◽  
Solid Lipid ◽  
Freeze Dried

Famciclovir loaded Solid Lipid Nanoparticles (SLNs) using triglycerides as solid lipids were successfully prepared using the double emulsion-solvent evaporation technique. Formulation parameters like amount and type of lipid and level of surfactants affected the nanoparticle characters. It was observed that nanoparticle characters like average particle size and distribution, drug content, entrapment efficiency and release pattern were dependent on these formulation variables. The optimized formulations depicted the desired characters of low particle size, in the range of 140-170 nm in case of Glyceryl monostearate (GMS) and glyceryl distearate (GDS) SLNs and 250-340 nm in case of glyceryl behenate (GB) SLNs and entrapment efficiencies in the range of 35-48%. In vitro drug release was extended upto 8 h and the release profile was explained by the Baker-Lonsdale model for spherical particles. Morphological examination by Scanning Electron Microscope (SEM) and Transmission Electron Microscope (TEM) displayed homogenous solid, spherical and non- porous particles. The formulations depicted good redispersibility after lyophilization and presence of residual solvents in the formulations within the prescribed limits suggested suitability of the preparation technique. Freeze- dried formulations were found to be stable in terms of particle size and drug loading even after 6 months of storage at refrigerated conditions.

scholarly journals Actin filaments elongate from their membrane-associated ends

1981 ◽  
Vol 90 (2) ◽  
pp. 485-494 ◽  
Author(s):  
LG Tilney ◽  
EM Bonder ◽  
DJ DeRosier
Keyword(s):  
Plasma Membrane ◽  
Actin Filament ◽  
Actin Filaments ◽  
The Other ◽  
Dense Material ◽  
Thin Sections ◽  
Vacuole Membrane ◽  
Filament Bundles ◽  
Filament Bundle

In limulus sperm an actin filament bundle 55 mum in length extends from the acrosomal vacuole membrane through a canal in the nucleus and then coils in a regular fashion around the base of the nucleus. The bundle expands systematically from 15 filaments near the acrosomal vacuole to 85 filaments at the basal end. Thin sections of sperm fixed during stages in spermatid maturation reveal that the filament bundle begins to assemble on dense material attached to the acrosomal vacuole membrane. In micrographs fo these early stages in maturation, short bundles are seen extending posteriorly from the dense material. The significance is that these short, developing bundles have about 85 filaments, suggesting that the 85-filament end of the bundle is assembled first. By using filament bundles isolated and incubated in vitro with G actin from muscle, we can determine the end "preferred" for addition of actin monomers during polymerization. The end that would be associated with the acrosomal vacuole membrane, a membrane destined to be continuous with the plasma membrane, is preferred about 10 times over the other, thicker end. Decoration of the newly polymerized portions of the filament bundle with subfragment 1 of myosin reveals that the arrowheads point away from the acrosomal vacuole membrane, as is true of other actin filament bundles attached to membranes. From these observations we conclude that the bundle is nucleated from the dense material associated with the acrosomal vacuole and that monomers are added to the membrane-associated end. As monomers are added at the dense material, the thick first-made end of the filament bundle is pushed down through the nucleus where, upon reaching the base of the nucleus, it coils up. Tapering is brought about by the capping of the peripheral filaments in the bundle.

scholarly journals A quantitative study of pinocytosis and intracellular proteolysis in rat peritoneal macrophages

1977 ◽  
Vol 168 (3) ◽  
pp. 365-372 ◽  
Author(s):  
M K Pratten ◽  
K E Williams ◽  
J B Lloyd
Keyword(s):  
Plasma Membrane ◽  
Binding Sites ◽  
Culture Medium ◽  
Peritoneal Macrophages ◽  
The Other ◽  
High Rate ◽  
Intracellular Proteolysis ◽  
Pinocytic Vesicles ◽  
Stimulation Of

A method for the culture of rat peritoneal macrophages in vitro is described, in which pinocytic uptake of colloidal [198 Au]gold, 125I--labelled poly(vinylpyrrolidone) and [14C]sucrose proceeds at contant and fairly reproducible rates for several hours. The rat of uptake of colloidal [198 Au]gold, which wxhibited some inter-batch variation, was approx. 100 times that of the other two substrates. Colloidal gold did not affect the rate of uptake of 125I-labelled poly(vinylpyrrolidone) and therefore its own high rate of uptake could not be attributed to a stimulation of the formation of pinocytic vesicles. It conclude that uptake of collodial gold is highly dependent on adsorption on binding sites on the plasma membrane. Uptake of formaldehyde-treated 125I-labelled bovine serum albumin was followed by the release of [125I]iodo-L-tyrosine into the culture medium and took place at a rate intermediate between those of collodial [198Au]gold and the other two non-digestible substrates, 125I-labelled poly(vinylpyrrolidone) and [14C]sucrose.

scholarly journals Effect of niclosamide on the tegumental surface of Haplorchis taichui using scanning electron microscopy

2007 ◽  
Vol 81 (4) ◽  
pp. 329-337 ◽  
Author(s):  
K. Kumchoo ◽  
C. Wongsawad ◽  
P. Vanittanakom ◽  
J.Y. Chai ◽  
A. Rojanapaibul
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Plasma Membrane ◽  
Electron Microscope ◽  
Apical Plasma Membrane ◽  
Control Groups ◽  
Tegumental Surface ◽  
Haplorchis Taichui ◽  
Scanning Electron

AbstractThe effect of niclosamide on the tegument of adult Haplorchis taichui (Trematoda: Heterophyidae) exposed in vitro was observed by scanning electron microscope. Adult worms were incubated in Tyrode's solution containing 0.01, 0.1, 1.0, and 10 μg ml− 1 of niclosamide for 30 min, 1, 6, 12 and 24 h. Control groups were incubated in Tyrode's solution without niclosamide and worms remained active until 24 h. In 0.01 μg ml− 1 of niclosamide, worms showed slightly active movements up to 1 h after incubation, while in 0.1 μg ml− 1 solution a few worms showed only slightly active movements after 30 min. Tegumental changes were determined by scanning electron microscopy. Swelling and blebbing of the tegument were observed on both ventral and dorsal sides. After longer periods, extensive swelling and blebbing of the tegument became more severe and there was a loss of the apical plasma membrane in some regions. Empty spine sockets occurred, and small perforations penetrated the basal lamina, followed by some lesions. Destruction of both surfaces was more pronounced on the posterior compared with the anterior regions.

Sign in / Sign up

Export Citation Format

Share Document