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At least 19 recordsLinked to original sources
PubMed1975

Electron microscopic cytochemical characterization of bile canaliculi and bile ducts in vitro.

Electron microscopic cytochemical localization of Mg++-activated adenosine triphosphatase (Mg++-ATPase) and 5-nucleotidase (AMPase) was investigated in bile canaliculus-rich and bile duct-containing fractions isolated from rat liver. Comparative cyochemical studies between prefixed and non-prefixed fractions revealed that the activity of both enzymes could be detected in the fractions under appropriate experimental conditions. However, the cytochemical activity of AMPase was much more sensitive to glutaraldehyde than that of Mg++-ATPase. Mg++-ATPase and AMPase reaction products were localized primarily on bile canalicular microvilli, that is, along the outer (luminal) surface of canalicular plasma membranes, but they were never observed on bile ductal microvilli. AMPase was also detectable on lateral hepatic plasma membranes. Mg++-ATPase demonstrated by the cytochemical technique described is a reliable enzyme marker for isolated bile canalicular membranes. At high magnification, Mg++-ATPase reaction product was also observed on the microfilaments surrounding isolated bile canaliculi. The possibility that the reaction product on the pericanalicular microfilaments may result from the hydrolysis of ATP byan actomyosin ATPase-like enzyme associated with these filaments is briefly discussed.

Adenosine Triphosphatases↗
PubMed1976

The effect of thyroid hormone on bile salt-independent bile flow and Na+, K+ -ATPase activity in liver plasma membranes enriched in bile canaliculi.

The relationship between bile salt-independent canalicular flow and ATPase activity in liver plasma membranes (LPM) enriched in bile canaliculi, was studied in control, hyperthyroid, and hypothyroid rats. Canalicular bile production was significantly increased in hyperthyroid rats (3.19 +/- 0.23 mul/min per g liver) compared to controls (2.27 +/- 0.24 mul/min per g liver), while it diminished in hypothyroid animals (1.58 +/- 0.17 mul/min per g liver). Although bile salt excretion was also increased in hyperthyroid animals (62.4 +/- 13.3 vs. 41.2 +/- 8.4 nmol/min per g liver), the stimulation in canalicular secretion was primarily related to enhancement of the bile salt-independent fraction of flow (2.47 mul/min per g liver in hyperthyroid rats vs. 1.67 mul/min per g liver in controls). LPM Na+, K+-ATPase activity doubled in hyperthyroid animals (21.5 +/- 5.8 vs. 10.7 +/- 3.1 mumol Pi/mg protein per h) while Mg++-ATPase activity remained unchanged and 5'-nucleotidase activity increased to a small but significant extent. In hypothyroid rats, bile salt excretion remained unchanged from control values so that the reduced secretion was entirely secondary to an inhibition of bile salt-independent secretion (1.19 mul/min per g liver). Na+, K+-ATPase activity in the LPMs from hypothyroid animals decreased by nearly 50% (5.4 +/- 1.6 mumol Pi/mg protein per h), although comparable reductions in the specific activity of Mg++-ATPase and 5'-nucleotidase were also observed. Administration of L-thyroxine to hypothyroid animals restored both bile salt-independent canalicular secretion and membrane enzymes to control values within 2 and 4 days, respectively. Sodium dodecyl sulfate gel electrophoresis demonstrated no significant changes in LPM protein fractions from any of the treatment groups. These studies indicate that thyroid hormone has a parallel effect on bile salt-independent canalicular secretion and LPM Na+, K+-ATPase activity, supporting the hypothesis that Na+ transport and Na+, K+-ATPase may be determinants of bile salt-independent canalicular flow.

Adenosine Triphosphatases↗
PubMed1977

Relationship between bile flow and Na+, K+-adenosinetriphosphatase in liver plasma membranes enriched in bile canaliculi.

The relationship between bile flow and Na+,K+-ATPase activity in liver plasma membranes enriched in bile canaliculi was studied in rats treated with ethinyl estradiol, phenobarbital, or 20-methyl cholanthrene. In comparison with controls (1.49+/-0.12 microliter/min per g liver), bile flow was significantly diminished by ethinyl estradiol, increased by phenobarbital, and unchanged by 20-methyl cholanthrene or the solvent, propanediol (0.92+/-0.31, 2.50+/-0.21, 1.62+/-0.18, and 1.64+/-0.30 microliter/min per g liver, respectively). The corresponding values for canalicular Na+,K+-ATPase activity were 80.7+/-19.2, 50.0+/-18.4, 231.7+/-42.6, 82.7+/-30.7, and 143.6+/-55.3 micronmol Pi/h per g liver. Canalicular Na+,K+-ATPase activity was significantly correlated (r=0.785, n=31) with bile flow. These findings support the hypothesis that a fraction of bile flow is related to Na+,K+-ATPase activity and canalicular Na+ transport.

Adenosine Triphosphatases↗
PubMed1975

Properties of (Na+ plus K+)-activated ATPase in rat liver plasma membranes enriched with bile canaliculi.

Liver plasma membranes enriched in bile canaliculi were isolated from rat liver by a modification of the technique of Song et al. (J. Cell Biol. (1969) 41, 124-132) in order to study the possible role of ATPase in bile secretion. Optimum conditions for assaying (Na+ plus K+)-activated ATPase in this membrane fraction were defined using male rats averaging 220 g in weight. (Na+ plus K+)-activated ATPase activity was documented by demonstrating specific cation requirements for Na+ and K+, while the divalent cation, Ca(2+), and the cardiac glycosides, ouabain and scillaren, were inhibitory. (Na+ plus K+)-activated ATPase activity averaged 10.07 plus or minus 2.80 mumol Pi/mg protein per h compared to 50.03 plus or minus 11.41 for Mg(2+)-activated ATPase and 58.66 plus or minus 10.07 for 5'-nucleotidase. Concentrations of ouabain and scillaren which previously inhibited canalicular bile secretion in the isolated perfused rat liver produced complete inhibition of (Na+ plus K+)-activated ATPase without any effect on Mg(2+)-activated ATPase. Both (Na+ plus K+)-activated ATPase and Mg(2+)-activated ATPase demonstrated temperature dependence but differed in temperature optima. Temperature induced changes in specific activity of (Na+ plus K+)-activated ATPase directly paralleled previously demonstrated temperature optima for bile secretion. These studies indicate that (Na+ plus K+)-activated ATPase is present in fractions of rat liver plasma membranes that are highly enriched in bile canaliculi and provide a model for further study of the effects of various physiological and chemical modifiers of bile secretion and cholestasis.

Adenosine Triphosphatases↗
PubMed1977

Peripheral immunofluorescence of hepatocytes. Relation to smooth muscle antibodies and bile canaliculi.

By means of indirect immunofluorescence microscopy, a peripheral fluorescence reaction with hepatocytes was found, surrounding the entire cell, with sera from patients with cancer and acute hepatitis and from normal blood donors. It was proved that this reaction was not related to bile canaliculi, contrary to bile canaliculi antibody demonstrated previously from patients with chronic active liver disease. By using fluorescein-conjugated anti-human IgG, the reaction with the periphery of the hepatocytes was produced to a more or less pronounced degree with almost all sera studied. The reaction seems not to be directed against contractile proteins on the liver cell membrane as only a minor part of these sera had also IgG smooth-muscle antibody, and anti actomyosin antibody obtained by affinity chromatografy did not react with the hepatocyte. When applying fluorescein-conjugated anti-human IgM the reaction with the periphery of the hepatocytes was observed in one fourth of the patients with acute hepatitis and only sera which contained also IgM smooth-muscle antibody.

Animals↗
PubMed1979

A three-dimensional study of organelle interrelationships in regenerating rat liver. 3. Organelles related to bile.

A number of cell structures are described which show a morphological relationship to the bile canaliculi. Two types of peribiliary vesicles are identified: osmication positive ones occurring between the bile canaliculi and the osmicated immature Golgi cisternae and probably deriving from the latter, and osmication negative ones related to MVB, on which they appear as buds. Small coated vesicles are seen attached to this second type. Large lacunae may originate from MVB, as suggested by the MVB-like internal vesicles they may contain. Some stay in luminal continuity with the bile canaliculi. Canalicular coated vesicles are seen as parts of the canalicular plasma membrane and free in the cytoplasm.

Animals↗
PubMed1979

Fine structure of the liver in the larval lamprey, Petromyzon marinus L.; hepatocytes and sinusoids.

The ultrastructure of hepatocytes, bile canaliculi, and hepatic sinusoids of the larval lamprey, Petromyzon marinus, was examined using thin-sectioned and freeze-fractured tissues. The liver is a "tubular gland" with hepatocytes arranged in a tubular fashion around large bile canaliculi. Hepatocytes are roughly conical in shape, with their tapered apices facing a bile canalicular lumen. They possess extensive rough and smooth endoplasmic reticulum, a well-developed Golgi complex, abundant mitochondria, and varying numbers of large secondary lysosomes. Both secondary lysosomes and the Golgi complex are concentrated in the apical or peribiliary cytoplasm, indicating a possible role in bile secretion. The apical surfaces of the hepatocytes bear numerous elongate microvilli and occasional cilia, which project into the bile canaliculi. The hepatocytes are joined, apically, by junctional complexes composed of zonulae occludentes and adhaerentes. In freeze-fracture, the zonulae occludentes are of variable apicobasal depth and consist of honeycomb-like meshworks of fibrils. Spaces of variable width frequently appear in the P-face grooves, indicating that the zonulae occludentes are "leaky." Numerous communicating (gap) junctions join the hepatocytes laterally. Varying numbers of lateral microvilli project into the intercellular spaces and, basally, the plasma membrane is deeply infolded, resulting in the formation of apparently interdigitating basal processes resting upon a thin basal lamina. Sinusoids are composed of both a heavily-fenestrated, continuous endothelium, and phagocytic reticulo-endothelial (Kupffer) cells. Depsite the difference in arrangement of their hepatocytes, the mammalian and lamprey livers show similar ultrastructural features.

Animals↗
PubMed1976

Subcellular localization of B apoprotein of plasma lipoproteins in rat liver.

Multispecific antigen-binding fragments (Fab) from rabbit antisera against rat very low density lipoproteins (VLDL) and Fab against rat low density lipoproteins that were monospecific for the B apoprotein were conjugated to horseradish peroxidase. Conjugates were incubated with 6-mum frozen sections from fresh and perfusion-fixed livers and with tissue chopper sections (40 mum thick) from perfusion-fixed livers. In the light microscope, specific reaction product was present in all hepatocytes of experimental sections as intense brown to black spots whose locations corresponded to the distribution of the Golgi apparatus: along the bile canaliculi, near the nuclei, and between the nuclei and bile canaliculi. Perfusion fixation with formaldehyde produced satisfactory ultrastructural preservation with retention of lipoprotein antigenic determinants. In the electron microscope, patches of cisternae and ribosomes of the rough endoplasmic reticulum (ER) and particularly its smooth-surfaced ends, vesicles located between the rough ER and the Golgi apparatus, the Golgi apparatus and its secretory vesicles and VLDL particles in the space of Disse all bore reaction product. The tubules and vesicles of typical hepatocyte smooth ER did not contain reaction product, nor did the osmiophilic particles contained therin. The localization obtained in this study together with other evidence suggests a sequence for the biosynthesis of VLDL that differs in some respects from that proposed by others: (a) the triglyceride-rich particle originates in smooth ER where triglycerides are synthesized; (b) at the junction of the smooth and rough ER the particle receives apoproteins synthesized in the rough ER; (c) specialized tubules transport the particle, now a nascent lipoprotein, to the Golgi apparatus where concentration occurs in secretory vesicles; (d) secretory vesicles move to the sinusoidal surface where the particles are secreted into the space of Disse by fusion of the vesicular membrane with the plasma membrane of the hepatocyte.

Animals↗
PubMed1977

[Physiology of bile formation (author's transl)].

Generation of bile flow in humans depends mainly on two transport mechanisms of the hepatocyte. One of these is responsible for secretion of bile acids, the other for transport of sodium into the bile canaliculi. Accordingly, a bile acid dependent fraction of hepatocytic bile can be distinguished from a bile acid independent fraction. Many endogenous and exogenous substances, including x-ray contrast media, are secreted into hepatocytic bile by more or less specific transport systems. The bile produced by the liver cells is then modified by admixture of ductular bile and by reabsorptive processes in the biliary passages and in the gallbladder. Increased knowledge about these mechanisms represents one of the requirements for progress in oral and intravenous cholangiography.

Animals↗
PubMed1978

Loss and reappearance of gap junctions in regenerating liver.

Changes in intercellular junctional morphology associated with rat liver regeneration were examined in a freeze-fracture study. After a two-thirds partial hepatectomy, both gap junctions and zonulae occludentes were drastically altered. Between 0 and 20 h after partial hepatectomy, the junctions appeared virtually unchanged. 28 h after partial hepatectomy, however, the large gap junctions usually located close to the bile canaliculi and the small gap junctions enmeshed within the strands of the zonulae occudentes completely disappeared. Although the zonulae occludentes bordering the bile canaliculi apparently remained intact, numerous strands could now be found oriented perpendicular to the canaliculi. In some instances, the membrane outside the canaliculi was extensively filled with isolated junctional strands, often forming very complex configurations. About 40 h after partial hepatectomy, very many small gap junctions reappeared in close association with the zonulae occludentes. Subsequently, gap junctions increased in size and decreased in number until about 48 h after partial hepatectomy when gap junctions were indistinguishable in size and number from those of control animals. The zonulae occludentes were again predominantly located around the canalicular margins. These studies provide further evidence for the growth of gap junctions by the accretion of particles and of small gap junctions to form large maculae.

Animals↗
PubMed1978

Secretion of lipoprotein-X by perfused livers of rats with cholestasis.

The major abnormal plasma lipoprotein of cholestasis (LP-X) was isolated from blood plasma and from perfusates of isolated livers of rats with biliary obstruction. In both cases LP-X was composed mainly of about equimolar parts of phospholipids and unesterified cholesterol; the small protein component was primarily the arginine-rich apolipoprotein. By electron microscopy, LP-X appeared as a unilamellar liposome (690 A mean diameter, range 400-1000 A) with the trilaminar staining image typical of phospholipid bilayers. Extensive block staining of cholestatic livers for 48 hr with warmed uranyl acetate (37 degrees) permitted the visualization of vesicles indistinguishable from LP-X within hepatic parenchyma. These trilaminar-staining vesicles occurred predominantly within bile canaliculi. They also were seen in nearby cytoplasmic vacuoles or invaginations between hepatocytes and in the space of Disse. Similar vesicles were not seen in the endoplasmic reticulum or Golgi cisternae. These observations raise the possibility that the vesicles are formed within bile canaliculi and are transported from the canaliculi to the space of Disse within pinocytotic vacuoles.

Animals↗
PubMed1979

Sequential analysis of hepatic carcinogenesis: a comparative study of the ultrastructure of preneoplastic, malignant, prenatal, postnatal, and regenerating liver.

The objective of this study was to compare the fine structure of presumptive preneoplastic hepatocytes at various times during liver carcinogenesis with that of normal, developing, and regenerating liver and of hepatocellular carcinomas, using transmission and scanning electron microscopy. A new model of liver carcinogenesis was used in which several of the early steps are quite well synchronized. A single initiating dose of diethylnitrosamine induced isolated islands of altered hepatocytes. The cells were characterized by persistence of glycogen despite starvation, increase in smooth endoplasmic reticulum, and hypertrophic nucleoli. Following intense selection of the altered hepatocytes by dietary 2-acetylaminofluorene plus partial hepatectomy, the affected hepatocytes proliferated rapidly to produce basophilic foci. These early hyperplastic lesions revealed stellate-shaped dilated bile canaliculi lined by blebs and abnormally thick elongated microvilli, a decreased number of microvilli on the sinusoidal surface, a marked increase in smooth endoplasmic reticulum, large nucleoli, and bundles of pericanalicular microfilaments. A majority of the proliferating lesions reacquired a normal organizational pattern within several weeks after partial hepatectomy and could not be distinguished from normal liver. A small number continued to grow and become typical persistent hyperplastic nodules. These showed significant widening of intercellular spaces between hepatocytes, elongated microvilli over large regions of the cell surface, many invaginations of the cell membrane, and irregularly shaped bile canaliculi. Sequential changes in focal hyperplastic hepatocytes during carcinogenesis could be distinguished from normal, developing, and regenerating liver. The major differences involved the cell surfaces and cytoplasmic organelles. The findings are compatible with the hypothesis that a carcinogen may act by inducing alterations in a small number of hepatocytes and that hepatocellular carcinomas arise through stepwise evolutional changes in these cells.

Animals↗
PubMed1979

New observations on the fine structure of the liver in goldfish (Carassius auratus).

A re-examination of goldfish liver was made through the use of SEM of fractured samples and TEM of ultrathin-sections and freeze-etch replicas. Several new hepatic fine structures described in the present study are morphologically similar to those reported previously in many higher vertebrates including mammals. Hepatic sinusoids of goldfish contain fenestrations which are arranged into sieve plates. Although the hepatic plates are made up of two layers of hepatocytes, the parenchymal cells of gold fish liver are morphologically similar to mammalian hepatocytes, particularly with respect to the sinusoidal surfaces which are studded with numerous microvilli. The intercellular surfaces of hepatocytes have both nexus and demosomal junctions, similar to those found in various epithelial cells of higher vertebrates, between the openings of the intracellular bile canaliculi and the intralobular bile ductules which are situated in the center of the bicellular hepatic plate.

Animals↗
PubMed1979

Immunofluorescence studies on the occurrence and localization of the CEA-related biliary glycoprotein I (BGP I) in normal human gastrointestinal tissues.

Biliary glycoprotein, I(BGP I) is a carcinoembryonic antigen (CEA) cross-reactive glycoprotein of normal human bile. Its occurrence and localization was studied in normal human gastrointestinal tissues by means of direct immunofluorescence using immunadsorbent purified BGP I antibodies with high selectivity for BGP I, as compared to CEA and 'non-specific cross-reacting antigen' (NCA). As controls fluorescein-labelled CEA and NCA were used. Specific BGP I fluorescence was only found in the biliary tract, i.e. in bile canaliculi, in the lumen of large bile ducts and on the surface of the gall bladder mucosa. No fluorescence was found in the hepatocytes or in the cells lining larger bile ducts or the gall bladder. Fluorescence probably due to cross-reaction with NCA was obtained in the cytoplasm of macrophages in different organs and on the surface of bowel epithelium.

Adult↗
PubMed1976

Alterations of the myoid pericanalicular layer in liver. A light microscopical pilot study of human autopsy material.

Previous histochemical studies demonstrated a myoid layer along biliary pathways. This report describes alterations of the pericanalicular layer in various lesions. Carnoy- or methacarn-fixed sections of livers from 200 autopsies were treated with the tannic acid-phosphomolybdic acid-dye method for myosins. In other series, methods for myosins were combined with the picro-Sirius Red F3BA stain or the Prussian Blue reaction. In normal liver, bile canaliculi were lined by a narrow myoid layer. In other cases, eg, hepatic cirrhosis, the pericanalicular layer showed slight to moderate thickening. In cases with obstruction or atresia of bile ducts, the dilated canaliculi were surrounded by a prominent myoid layer. These observations support theories that the pericanalicular layer is contractile and promotes bile flow under positive pressure.

Bile Ducts, Intrahepatic↗