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  • 1
    Electronic Resource
    Electronic Resource
    Effects of temperature on the degradation and biliary secretion of asialoorosomucoid by the perfused rat liver: Evidence for two intracellular pathways (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 138 (1989), S. 555-560 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: We have utilized the in situ perfused rat liver under nonrecirculating conditions to examine the effect of temperature on the metabolism and biliary secretion of [125I]-asialoorosomucid (ASOR). In this manner we were able to follow the fate of a single round of internalized ligand. In control livers perfused at 37°C, approximately 50% of [125I]-ASOR injected into the portal vein was extracted on first pass. Five minutes after the injection, radioactivity, which had been extracted initially, began to appear in the hepatic venous effluent. Within 25 min, 50% of the initially extracted radioactivity was released into the perfusion medium; the bulk of this radioactivity (〉95%) was soluble in trichloroacetic acid. In livers perfused at temperatures slightly less than 37°C (30-35°C), first-pass extraction of [125I]-ASOR was similar to that observed at 37°C. However, a severalfold decrease in the rate of release of radioactivity from the liver into the perfusion medium was noted at the lower perfusion temperatures; whereas greater than 50% of the initially extracted radioactivity was released within 30 min from livers perfused at 37°C, only 5% was released at 30°C. At the lower perfusion temperature, a larger proportion of the released radioactivity was acid precipit-able (24% vs. 5%). Some radioactivity also was recovered in the bile; of the total amount of radioactivity released from the liver in 30 min at 37°C, approximately 5% was directed into the bile. At lower temperatures of perfusion, a greater fraction of the radioactivity that was released from the liver was directed into the bile (20% at 30°C vs. 5% at 37°C). The data imply that the endosomal pathway to the lysosome is highly sensitive to slight reductions in temperature while the transcytotic route into bile is less sensitive. Lower temperatures might prolong the residence time of ASOR in the prelysosomal endosomal compartments, and thereby increase the likelihood that undegraded ligand will be returned to the blood or be missorted into bile.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041380316
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Ganglioside patterns of metastatic and non-metastatic transplantable hepatocellular carcinomas of the rat (1979)
    New York, N.Y. : Wiley-Blackwell
    Journal of Supramolecular Structure 11 (1979), S. 485-492 
    Details
    ISSN: 0091-7419
    Keywords: carcinoma ; cell surface ; ganglioside ; hepatoma ; metastatis ; sialic acid ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In previous investigations, we correlated levels of sialic acid, gangliosides, and ganglioside glycosyltransferases with tumorigenesis over a 24-week continuum of growth of hepatocellular neoplasms of the rat induced by the carcinogen N-2-fluorenylacetamide. However, metastatic tumors developed only rarely and were not analyzed. To investigate surface changes associated with metastasis, well-differentiated and poorly differentiated hepatocellular carcinomas were transplanted to syngeneic recipient rats. From those, several metastatic and nonmetastatic isolates were obtained and compared. Both total and ganglioside sialic acid amounts in transplantable hepatomas were elevated above control liver values but were significantly lower for metastatic lines than for nonmetastatic lines. The nonmetastatic lines were characterized by ganglioside patterns depleted in the precursor ganglioside GM3 (sialic acid-galactose-glucose-ceramide) and elevated in the products of the monosialoganglioside pathway. In contrast, metastatic isolates exhibited a restoration of GM3 and nearer normal amounts of other gangliosides. The findings point to differences in sialic acid-containing glycolipids, comparing metastatic and nonmetastatic hepatocellular carcinomas, and further extend the concept that ganglioside alterations do not cause tumorigenesis but are the end result of a cascade of events which apparently continue beyond the onset of metastasis.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jss.400110407
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  • 3
    Electronic Resource
    Electronic Resource
    Rat liver membrane secretory component is larger than free secretory component in bile: Evidence for proteolytic conversion of membrane form to free form (1984)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 24 (1984), S. 307-317 
    Details
    ISSN: 0730-2312
    Keywords: secretory component ; bile ; IgA ; immunoblot ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Secretory component is a receptor for polymeric immunoglobulins on epithelial cells and hepatocytes that facilitates transport of polymeric immunoglobulins into external secretions. Little is known about the transcellular migration of secretory component-polymeric IgA complexes or the membrane forms of secretory component. We therefore examined rat bile and liver membranes to identify and compare the various molecular species of secretory component. Bile or liver membrane proteins were electrophoresed in sodium dodecyl sulfate-polyacrylamide gels and electrophoretically transferred to nitrocellulose membranes. Protein profiles on blots were probed with antisecretory, component antiserum, and the immunoreactive bands were visualized by indirect immunoperoxidase staining. Bile collected in the presence of proteolytic inhibitors showed an immunoreactive doublet band (Mr = 82,000 and 78,000) in the molecular weight range of free secretory component. By contrast, free secretory component in bile collected in the absence of proteolytic inhibitors and purified by affinity chromatography migrated as a single protein with an Mr = 70,000. Both components of the free secretory component doublet bound dimeric IgA when blots were probed with human dimeric IgA. Crude liver membranes prepared in the presence of proteolytic inhibitors showed two immunoreactive secretory component-containing bands, Mr = 107,000 and 99,000, whereas membranes prepared without proteolytic inhibitors showed two smaller immunoreactive bands; one of these proteolytically severed proteins comigrated with the 82,000-dalton free secretory component in bile. These results indicate that membrane forms of secretory component are present in rat liver. The observations that the membrane secretory component is larger than biliary free secretory component and yields biliary SC-like forms of secretory component upon proteolysis support the hypothesis that free secretory component in bile is a proteolytic product of larger liver membrane-associated secretory component.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240240402
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of monensin on vesicular transport pathways in the perfused rat liver (1986)
    New York, N.Y. : Wiley-Blackwell
    Journal of Cellular Biochemistry 32 (1986), S. 235-245 
    Details
    ISSN: 0730-2312
    Keywords: monesin ; vesicular transport pathways ; liver perfusion ; asialoorosomucoid ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: In the rat hepatoctye, the internalization and degradation of asialoglycoproteins and the secretion of plasma and biliary proteins require specific intracellular sorting of vesicles. To aid in the biochemical characterization of these different vesicular pathways, we examined the effects of the ionophore monensin on the uptake and degradation of 125I-asialoorosomucoid (ASOR) and on the secretion of plasma and biliary proteins by the in situ perfused rat liver. In control livers, 77% of injected 125I-ASOR was extracted on first pass; 93% of the extracted radioactivity was released back into the circulation (totally degraded and some intact ASOR was found); and approximately 2% was recovered in the bile, some of which was intact. Monensin treatment decreased first pass uptake of 125I-ASOR to 57% and abruptly blocked the release of radioactivity into the perfusate and the bile. When hepatic proteins were biosynthetically labeled with 3H-leucine, monensin treatment dramatically reduced and delayed the secretion of newly synthesized proteins into both the perfusate and the bile. In contrast with control livers, in which secretion of protein into the perfusate preceded secretion of protein into the bile, TCA-precipitable 3H-protein appeared in bile about 20 min before TCA-precipitable 3H-protein appeared in the perfusate in monensin-treated livers. Thus, monensin treatment in the perfused liver blocked the degradation of asialoglycoproteins and inhibited the secretion of plasma proteins but had less effect on biliary protein secretion. These data document physiologic effects of monensin in an intact organ and suggest that biochemical distinctions between different vesicular pathways exist in the rat hepatocyte.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcb.240320310
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