摘要:

AbstractThe liver is the main site of iron accumulation and pathologic sequelae in hereditary hemochromatosis. Whether this is a result solely of inappropriately increased absorption of iron by the gastrointestinal tract or a more generalized regulatory failure of iron balance is unknown. Using immunohistochemical techniques, we have examined the effects of therapeutic changes in liver iron stores on the expression of the hepatic trans‐ferrin receptor in hereditary hemochromatosis. Ten patients with untreated hereditary hemochromatosis had no detectable staining for transferrin receptor in their liver biopsies. All had increased hepatic ferritin (mean = 19.9 μg per mg protein, range = 1 to 31.7 μg per mg protein) and hepatic iron levels (mean = 36.2 μg per mg protein, range = 3.6 to 69.9 μg per mg protein). In contrast, hepatocyte transferrin receptor was detected in seven patients in whom hepatic iron stores were markedly depleted by venesection (hepatic ferritin mean = 0.32 μg per mg protein, range = 0.16 to 0.53 μg per mg protein; hepatic iron mean = 0.98 μg per mg protein, range = 0.3 to 2.1 μg per mg protein). Sequential data from one patient confirmed the reexpression of receptor in response to therapeutic iron depletion, whereas data from another patient studied during treatment illustrated a reciprocal relationship between liver tissue distribution of iron and expression of transferrin receptor.The finding that appropriate physiologic regulation of the hepatic transferrin receptor operates in hereditary hemochromatosis does not support the concept of a generalized defect in receptor‐mediated uptake of trans‐ferr

ISSN:0270-9139    

DOI:10.1002/hep.1840090102

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY

摘要:

AbstractReduced hepatic uptake and clearance of macromolecules in liver cirrhosis is due to two major factors: increased diffusional barriers, resulting primarily from the deposition of excessive connective tissue in the space of Disse, and hepatocellular dysfunction, manifested by receptor and/or postreceptor defects.To probe the mechanisms underlying hepatocellular dysfunction in liver cirrhosis, we have investigated receptor‐ligand interactions for asialoorosomucoid, insulin and epidermal growth factor in hepatocytes isolated from the livers of rats chronically exposed to phenobarbital and carbon tetrachloride for up to 12 weeks. Viable cells were allowed to attach at 37°C and the high‐affinity cell surface binding sites for each ligand were assessed at 4°C in the presence of [125I]‐ligand. In parallel incubations, digitonin (0.055%) was added to the binding medium to assess total cellular binding sites.Results demonstrated that chronic treatment of rats with phenobarbital increased hepatocyte asialoorosomucoid surface receptor affinity (p<0.05) but had no affect on the number of asialoglycoprotein binding sites. Treatment with CCl4and phenobarbital significantly reduced the number of surface binding sites for asialoorosomucoid (p<0.05) and epidermal growth factor (p<0.02), although this treatment had no effect on either the binding affinity or the number of binding sites for insulin. The decrease in cell surface binding sites for asialoorosomucoid and epidermal growth factor was not due to a redistribution of the surface sites to intracellular locations, since the total number of cellular binding sites also was reduced. These results indicate that cirrhosis induced by phenobarbital and CCl4results in a differential effect on one parameter of hepatocellular function: receptor‐ligand in

ISSN:0270-9139    

DOI:10.1002/hep.1840090103

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY

摘要:

AbstractLiver fatty acid binding protein may play a role in the intracellular transport and compartmentation of long‐chain fatty acid metabolism. The distribution of liver fatty acid binding protein in the hepatic acinus was determined by means of immunocytochemistry as well as by measurement of liver fatty acid binding protein in cellular protein selectively released from zone 1 and zone 3 cells by means of anterograde and retrograde liver perfusion with digitonin. In untreated male rats, specific immunocytochemical staining for liver fatty acid binding protein showed a declining portal‐to‐central hepatocellular gradient in intensity, consistent with the portal‐to‐central ratio of liver fatty acid binding protein abundance measured in effluents from digitonin‐perfused livers of 1.6:1. Female and clofibratetreated male rats, in both of which hepatic synthesis and abundance of liver fatty acid binding protein are greater than in untreated males, differed as well in the pattern of acinar expression of this protein. In females, periportal concentrations of liver fatty acid binding protein determined from the effluent of livers perfused anterograde with digitonin were similar to male values, whereas liver fatty acid binding protein concentration in pericentral hepatocytes determined from the effluent of retrograde perfused livers was increased, resulting in a marked attenuation of the portal‐to‐central gradient of this protein; this was also apparent on immunocytochemistry. Clofibrate‐treated rats, in contrast, displayed a panacinar increase in liver fatty acid binding protein with maintenance of the portal‐to‐central ratio observed in untreated males. We conclude that there exists a declining portal‐to‐central gradient in liver fatty acid binding protein cellular abundance in the hepatic acinus of untreated male rats. Furthermore, the increased synthesis and abundance of liver fatty acid binding protein in female and clofibrate‐treated male rats results in two different alterations in the acinar expression of this protein,i.e.a pericentral increase (female) or a panlobular increase (clofibrate). Elucidation of the relationship between the zonation of hepatic fatty acid metabolism and the acinar expression of liver fatty acid binding protein should provide a more detailed understanding of t

ISSN:0270-9139    

DOI:10.1002/hep.1840090104

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY

摘要:

AbstractPeriportal and perivenous hepatocytes were isolated from rat liver by digitonin/collagenase perfusion for investigating the acinar heterogeneity of amino acid transport activities related to glutamine and ammonia metabolism. Immunocytochemical staining of the respective subpopulations for glutamine synthetase demonstrated that periportal subpopulations were essentially free of glutamine synthetase‐positive cells, whereas perivenous subpopulations showed a 2‐ to 3‐ fold enrichment of glutamine synthetase‐positive hepatocytes. The high perivenous/periportal ratio of 59 found for glutamine synthetase activity as well as the perivenous/periportal ratios of other marker enzymes further indicated the good separation of periportal and perivenous cells.α‐Aminoisobutyric acid, histidine and glutamate were used to determine the distribution pattern of amino acid transport systems A, N and G−, as well as of the sodium‐independent uptake of these compounds 1 hr after isolation and after maximal hormonal stimulation during primary culture. The strong heterogeneity of the sodium‐independent transport of histidine, characterized by higher perivenous transport rates [perivenous/periportal ratio: 1.5 (1 hr) to 3.5 (48 hr)], suggests a significant role of facilitated diffusion, presumably in glutamine export. Conversely, the strong heterogeneity of the sodium‐dependent glutamate transport (System G−) characterized by higher uptake rates in nonstimulated [perivenous/periportal ratio: 6.6 (1 hr)] and in hormonally treated perivenous hepatocytes (perivenous/periportal ratio: 2.2) reflects its possible significance with respect to the substrate availability for glutamine synthesis. The observed heterogeneities provide a basis for understanding how substrate fluxes related to glutamine metabolism might be established and regulated. In addition, our findings indicate that periportal and perivenous cells retain their zonal characteristics with respect to amino acid transport in primary cultur

ISSN:0270-9139    

DOI:10.1002/hep.1840090105

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY

摘要:

AbstractWe have measured the location of embryonic and adult hemopoietic foci in the liver tissue of postnatal and adult phenylhydrazine‐treated mice. Differentiation of acinar domains in liver tissue was made possible by carrying out succinate dehydrogenase histochemical reactions on liver cryostat sections. To determine the position of hemopoietic foci within the lobular gradient of the hepatocyte succinate dehydrogenase activity, this enzyme was measured in hepatocytes surrounding both portal and central veins and hemopoietic foci. Then, assuming the periportal succinate dehydrogenase activity value to be 1.00 ± 0.2, succinate dehydrogenase activity around postnatal hemopoietic foci was 0.65 ± 0.19, around phenylhydrazine‐induced hemopoietic foci 0.83 ± 0.24 and around central veins 0.44 ± 0.11. Scaling the portal to central vein distance and taking 1 as the portal vein point and 0 as the central vein point, the relative position of hemopoietic foci, indirectly calculated from succinate dehydrogenase activity values, was 0.35 ± 0.13 in postnatal livers and 0.73 ± 0.12 in phenylhydrazine‐treated adult livers. Hemopoietic foci frequencies varied according to both the origin and the liver acinar domain: in postnatal liver acini, it was 37.1% in zone 1, 22.8% in zone 2 and 40% in zone 3; in phenylhydrazine‐treated adult acini, it was 89.4% in zone 1 and 10.6% in zone 2. Postnatal hemopoietic foci mainly occurred extrasinu‐soidally, between hepatocytes and reticular‐like cells, whereas adult hemopoietic foci were mostly intrasinu‐soidal and closely associated to macrophage‐like cells. Adult hemopoietic colonies specifically developed in the periportal microenvironment of liver acini, which contrasts with the random distribution of residual hemo‐poiesis in postnatal mice. The biological conditions underlying phenylhydrazine‐induced adult hemopoiesis are in the periporta

ISSN:0270-9139    

DOI:10.1002/hep.1840090106

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY

摘要:

AbstractThe incorporation of3H‐proline in cells of liver biopsy specimens from patients with chronic active liver diseases has been studied by light and electron microscopic autoradiography. The labeled proline is incorporated by hepatocytes of the external rows of the residual liver lobule, by the cells of the proliferating bile ductule and very actively by the plasma cells localized at the boundary between the inflammatory infiltrate and the liver lobule. These plasma cells, which are often in close contact with the hepatocytes at the edge of the liver lobule, appear to be either negative or positive after the immunohistochemical tests for the k and λ chains of immunoglobulins. Results are discussed in relation to both the synthesis of collagen and the role of the immunocompetent cells during the process of the piecemeal necros

ISSN:0270-9139    

DOI:10.1002/hep.1840090107

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY

摘要:

AbstractHepatic fibrosis is the major clinical sequela of infection with the helminthSchistosoma mansoni. However, little is known regarding its dynamics and regulation in schistosomiasis. The present study presents the dynamics of deposition and resorption of two major extracellular matrix components of fibrosis, glycosaminoglycans and collagens, during the course of experimentalS. mansoniinfection. Early in infection (6 weeks), glycosaminoglycan biosynthesis was markedly elevated, as was collagen biosynthesis. This led to significant accumulations of these two molecules at a glycosaminoglycan/collagen ratio similar to that observed in livers of un‐infected mice (uronic acid/hydroxyproline ratio of 1.10 at 6 weeks compared to normal value of 1.25). During maximal hepatic fibrosis (12 to 18 weeks), both collagen and glycosaminoglycan biosynthesis continued to increase but the extracellular matrix shifted to a lower glycosaminoglycan/collagen ratio of 0.42, suggesting enhanced glycosaminoglycan breakdown. In addition, during this acute stage of infection, Type I collagen was the predominant isotype synthesized, whereas total collagenolytic activity degrading Type I collagen was maximal.During chronic infection, a decrease in the content of both hepatic glycosaminoglycans and collagens were noted, with a glycosaminoglycan/collagen ratio of 0.63. Decreased glycosaminoglycan content paralleled diminished biosynthetic rates. On the other hand, an over 50% reduction in collagen content (from 18 to 24 weeks) appeared not to result from diminished biosynthesis but from a switch in the predominant collagen isotype synthesized (from Type I to Type III), matched by an enhanced constitutive collagenolytic activity directed toward this type of collagen. These differences in the extracellular matrix separate schistosomal‐induced hepatic fibrosis from most other types of fibrotic liver disease and may explain differences in the clinical manifestations observed during different stages of infect

ISSN:0270-9139    

DOI:10.1002/hep.1840090108

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY

摘要:

AbstractHepatic ethanol oxidation generates the reactive intermediate acetaldehyde, which binds to proteins. Previous work, using bovine brain tubulin as a model protein, has shown that acetaldehyde preferentially formed stable adducts on the α‐chain of the heterodimeric molecule. This binding resulted in functional impairment of the tubulin/microtubule system as evidenced by a decreased ability of adducted tubulin to form microtubules. Since tubulin/microtubules are believed to be very important cytoskeletal components of the hepatocyte and results with brain tubulin were interesting, our goal was to extend these studies to liver tubulin. We purified tubulin from rat liver by a polymerization‐based cycle method followed by phosphocellulose chromatography. We then characterized the covalent binding of [14C]acetaldehyde to liver tubulin. Naturally forming and cyanoborohydride‐stimulated stable adducts formed linearly with liver tubulin in a manner almost identical to that with brain tubulin. We also found that the α‐chain of the native heterodimeric liver tubulin molecule was the preferred site of adduct formation at low acetaldehyde to protein ratios. These results confirm and extend our previous findings with the brain tubulin model and further suggest that the α‐chain of tubulin may be a preferential site for acetaldehyde‐adduct formation during ethanol oxidatio

ISSN:0270-9139    

DOI:10.1002/hep.1840090109

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY

摘要:

AbstractAntimitochondrial autoantibodies recognizing 68 to 74 and 50 to 52 kD inner membrane mitochondrial antigens are characteristically present in sera of patients with primary biliary cirrhosis. The biochemical identification of the antigens, however, has remained elusive. We report herein that the 52 kD antigen is the dihydrolipoamide acyltransferase of the branched‐chain α‐keto acid dehydrogenase complex. This was demonstrated by three experiments through the use of recombinant fusion protein expressed inEscherichia colifrom a cDNA insert encoding the human autoantigen. First, 36 of 37 primary biliary cirrhosis patients exhibiting reactivity toward the 50 to 52 kD mitochondrial antigen by immunoblotting also showed reactivity toward the recombinant fusion protein. Second, absorption of primary biliary cirrhosis sera with recombinant fusion protein, but not with an irrelevant recombinant clone, the F‐specific rat liver antigen, was effective in absorbing out reactivity against the 50 to 52 kD mitochondrial antigen but not the 68 to 74 kD antigen. Third, complete removal of reactivity toward all four different isoelectric point polypeptides at 50 to 52 kD was observed in two‐dimensional gel analysis. Furthermore, primary biliary cirrhosis sera were analyzed with mitochondria from three sources, rat liver, human placenta and bovine heart, in order to compare reactivity patterns and to determine precisely the comparative molecular weights of the autoantigens in the three species. The availability of recombinant autoantigens will provide improved diagnostic tests and, more importantly, will allow definite issues in primary biliary cirrhosis to be studied, including identification of immunodominant epitopes, the significance of autoantigen recognition and the establishment of autoreactive T cel

ISSN:0270-9139    

DOI:10.1002/hep.1840090110

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY

摘要:

AbstractA technique is described to remove the entire liver in a single stage with preservation of intestinal absorptive function. An inverted V‐shape polyethylene cannula, either heparin bonded or silicon coated, was inserted into the portal vein and inferior vena cava to maintain venous return from the splanchnic and lower caval regions of the anhepatic rat. Blood glucose fell at a rate of 7 to 11 mg per hr per total plasma volume (4% body weight), usually resulting in hypoglycemia within the initial 2 hr. Euglycemia could be maintained in the first 3 hr after hepatectomy with hourly intravenous infusions of 2.5 to 5 mg per 100 gm body weight of glucose. Larger infusionś of glucose (10 to 12.5 mg per hr per 100 gm body weight) were necessary for normal levels at later times. A 0.5 gm per 100 gm rat weight intestinal glucose bolus restored euglycemia for at least a 2‐hr interval. Intestinal absorption of cholesterol and oleic acid was demonstrated in the anhepatic rat, although the latter was not so efficiently absorbed as in the control. The plasma cholesterol decreased with time in the anhepatic rat. Prompt increases were observed in plasma free fatty acid and glycerol concentrations after hepatectomy. Progressive increases in both direct and indirect plasma billirubin levels were noted after hepatectomy. With appropriate maintenance of blood sugar, survival of 36 hr was observed. This procedure for single stage total hepatectomy in the rat can be performed in less than 30 min. The model is particularly useful for studies of the influence of the liver on post‐absorptive meta

ISSN:0270-9139    

DOI:10.1002/hep.1840090111

出版商:W.B. Saunders    

年代:1989

数据来源: WILEY