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Biomedical subjects

G Feldmann

Publications and source records attributed to G Feldmann.

At least 19 recordsLinked to original sources
PubMed1996

Structural and functional differentiation of sinusoidal endothelial cells during liver organogenesis in humans.

During fetal life, human liver sinusoids, which differentiate between 4 and 12 weeks of gestation from capillaries of the septum transversum, must support an important hematopoietic function and acquire the structural and functional characteristics of adult sinusoids. To gain insight into their differentiation process, we studied the expression of (1) markers of continuous endothelia, absent from adult sinusoidal endothelial cells (PECAM-1, CD34, and 1F10); (2) functional markers of adult sinusoidal endothelial calls (CD4, 1CAM-1, CD32, and CD14); and (3) extracellular matrix components (laminin, tenascin, fibronectin, and thrombospondin) in 37 fetuses of different gestational ages. We identified two successive differentiation events. (1) An early structural differentiation, occurring from 5 to 12 weeks of gestation, was characterized by the loss of continuous endothelial cell markers and a reduction in the perisinusoidal amount of laminin and in the deposition of tenascin, fibronectin, and thrombospondin; at the end of this process, fetal liver sinusoids present structural characteristics comparable to those of the sinuses in adult hematopoietic bone marrow. (2) A later functional differentiation was characterized by the acquisition of the markers of adult sinusoidal endothelial cells, initiating at 10 weeks of gestation and completed by 20 weeks of gestation; this process likely contributes to adapt liver sinusoids to the specific functions of the adult hepatic tissue.

Adult↗
PubMed1996

Interphase cytogenetic studies of human hepatocellular carcinomas by fluorescent in situ hybridization.

Although numerous allelic chromosome losses have been reported in hepatocellular carcinomas (HCC), chromosome analysis by cytogenetic methods has rarely been performed in these tumors, unlike other solid malignant tumors. The purpose of the current study was to analyze primary liver tumors by conventional cytogenetic methods and by a new molecular cytogenetic technique, called fluorescent in situ hybridization (FISH), a technique that has been recently proposed to count the number of chromosome copies in interphase nuclei with chromosome centromeric probes. Primary cultures of tumoral cells were prepared to obtain metaphases. Specific chromosomes probes 7, 17, and 20 were used to perform in situ hybridization on isolated intact tumoral cells. Seven cases of primary liver tumors (six cases of HCC and one case of benign focal hepatic nodular hyperplasia) were investigated. A few metaphases were obtained in five of the seven tumors, and in most cases numerical abnormalities were difficult to interpret. In contrast with in situ hybridization, all cases of HCC showed losses and/or gains of chromosomes. Loss of one to three chromosomes occurred in five tumors. A gain of two chromosomes was observed in two of these five tumors. In only one case, a gain of only three chromosomes occurred. In addition, a loss of chromosome 17 was recorded for the benign tumor. These results demonstrate that FISH with specific probes can provide information on chromosome number in the tumoral cells of primary liver tumors even in the absence of analyzable metaphases. This technique opens new possibilities for the investigation of chromosome abnormalities in HCC.

Adult↗
PubMed1996

Expression of cadherins and alpha-catenin in primary epithelial tumors of the liver.

BACKGROUND & AIMS: Cadherins and their associated molecules, such as alpha-catenin, have been shown recently to play a pivotal role in epithelial carcinogenesis. METHODS: The expression of E-cadherin, N-cadherin, and alpha-catenin in 10 normal samples, 28 focal nodular hyperplasias, 9 liver cell adenomas, 65 hepatocellular carcinomas, and 9 cholangiocarcinomas was studied by immunohistochemistry and Western blotting. RESULTS: In the normal liver, hepatocytes expressed E-cadherin and a 129-kilodalton cadherin identified by the anti-N-cadherin antibody GC4. The expression level of alpha-catenin was low. Bile duct cells expressed only E-cadherin and showed high levels of alpha-catenin. The expression of cadherins and alpha-catenin was preserved in focal nodular hyperplasia. In liver cell adenomas, cadherins and alpha-catenin were heterogeneously expressed. In hepatocellular carcinomas, cadherin and alpha-catenin expression was frequently reduced or absent. Alterations in cadherin expression correlated with large tumor size, low grade of histological differentiation, and occurrence of capsular and vascular invasion. In cholangiocarcinomas, neoplastic cells inconstantly expressed E-cadherin and alpha-catenin. CONCLUSIONS: Alterations of cadherin and alpha-catenin expression are frequent in liver cell adenomas and primary liver carcinomas. Their incidence in hepatocellular carcinomas is of prognostic significance.

Adenoma, Liver Cell↗
PubMed1995

The c-jun proto-oncogene down-regulates the rat alpha-fetoprotein promoter in HepG2 hepatoma cells without binding to DNA.

The effects of a phorbol ester (TPA) and of members of the Jun and Fos oncoprotein family on the activity of the rat alpha-fetoprotein (AFP) promoter were checked by using transient expression experiments in HepG2 hepatoma cells. TPA blocked the activity of the rat AFP promoter in a dose-dependent manner. Overexpression of c-Jun specifically repressed the rat AFP promoter but not the albumin promoter. JunB and JunD were poorer inhibitors. c-Fos expression did not potentiate the negative effect of Jun. The Jun-induced repression does not require binding of c-Jun to the AFP promoter. DNase 1 footprinting experiments did not display any high affinity binding site for Jun on the AFP promoter. Integrity of the c-Jun DNA binding domain is not required for the c-Jun protein to block the AFP promoter. The N-terminal part of Jun, which contains the activating domain, is responsible for the repression as shown by using Jun-Gal4 chimera. Jun likely exerts its negative control on the AFP promoter via protein-protein interactions with a not yet identified trans-activating factor within the -134 to +6 region or with a component of the general machinery of transcription. Jun proteins can thus be key intermediates in regulatory cascades which result in the differential modulation of the AFP and albumin gene expression in the course of liver development and carcinogenesis.

Animals↗
PubMed1995

Distribution of albumin, alpha 1-inhibitor 3 and their respective mRNAs in periportal and perivenous rat hepatocytes isolated by the digitonin-collagenase technique.

The expression of albumin and alpha 1-inhibitor 3 genes was investigated in rat cell suspensions enriched in periportal (n = 10) and perivenous (n = 10) hepatocytes obtained by the digitonin-collagenase technique. The degree of enrichment of the cell suspensions was assessed: (1) by enzymic assays for the periportal marker alanine aminotransferase and for the perivenous marker glutamine synthetase; and (2) by their content of mRNAs for the periportal marker hepatic glutaminase and for glutamine synthetase. The existence of an antegrade intra-lobular gradient for albumin and alpha 1-inhibitor 3 mRNAs was demonstrated, with periportal:perivenous ratios of 2.33 and 3.80, respectively. However, no gradient was demonstrated for the respective protein contents with corresponding ratios of 0.98 and 1.21. A certain degree of overlap existed between periportal and perivenous suspensions for their content in albumin and alpha 1-inhibitor 3 mRNAs. A morphometrical analysis of the surface of digitonin-permeabilized hepatic tissue revealed that this overlap could be explained by a variable extent of permeabilization of the mediolobular zone from one rat to another and from one lobule to another in a given animal. These results suggest that while the digitonin-collagenase technique is well suited for studies in vitro of proteins expressed in sharp intra-lobular gradients or restricted to an intra-lobular compartment, it is not completely reliable for proteins distributed in continuous moderate intra-lobular gradients, such as albumin and alpha 1-inhibitor 3.

Acute-Phase Proteins↗
PubMed1995

Cytochrome P4502B follows a vesicular route to the plasma membrane in cultured rat hepatocytes.

BACKGROUND/AIMS: Autoantibodies against cytochrome P450 are found in some forms of autoimmune hepatitis. Cytochrome P450 is synthesized and mainly located in the endoplasmic reticulum but may also be expressed on the plasma membrane of hepatocytes. Vesicles migrate from the endoplasmic reticulum to the Golgi apparatus and then to the plasma membrane along microtubules. We determined the route followed by cytochrome P4502B to reach the plasma membrane. METHODS: Rat hepatocytes were cultured for 2 hours after plating with various inhibitors of cellular trafficking. Detached, uncut, nonpermeabilized hepatocytes were then exposed to a monoclonal antibody specific for cytochrome P4502B and studied by flow cytometry and confocal microscopy. RESULTS: The plasma membrane expression of cytochrome P4502B was markedly decreased after 2 hours of culture with cycloheximide (an inhibitor of protein synthesis), caffeine at 20 degrees C (conditions that decrease vesicular transport from the endoplasmic reticulum to the Golgi apparatus), brefeldin A (which redistributes Golgi components back to the endoplasmic reticulum), monensin (an inhibitor of Golgi functions), and colchicine, vinblastine, or nocodazole (three microtubule inhibitors). CONCLUSIONS: Part of cytochrome P4502B follows a microtubule-dependent vesicular route from the endoplasmic reticulum to the plasma membrane in cultured rat hepatocytes.

Animals↗
PubMed1995

Focal nodular hyperplasia of the liver: composition of the extracellular matrix and expression of cell-cell and cell-matrix adhesion molecules.

We studied by immunohistochemistry 25 cases of focal nodular hyperplasia (FNH) to evaluate the composition of the extracellular matrix and the expression and distribution of endothelial cell-cell adhesion molecules and integrin receptors. The extracellular matrix of FNH retained the overall organization of that of normal liver. The matrix of central scars resembled that of portal tracts. The main difference was the presence of large vitronectin deposits, which might indicate the existence of local hemodynamic disturbances. The matrix lining the sinusoid-like vessels running in the hyperplastic parenchyma retained characteristic features of the normal perisinusoidal matrix, such as the presence of tenascin. In the zone surrounding the central scars, it contained large amounts of laminin, von Willebrand factor, and thrombospondin, suggesting the development of perisinusoidal fibrosis. Laminin deposition was accompanied by the induction of cell-cell adhesion molecules on adjacent endothelial cells and by the up-regulation of specific integrin receptors on both hepatocytes and sinusoidal endothelial cells. In conclusion, our study: (1) reinforces the hypothesis that FNH is merely a hyperplastic response of liver parenchyma to local vascular abnormalities, and (2) shows that the lesions of perisinusoidal fibrosis associated with FNH are accompanied by the induction of integrin receptors on hepatocytes and sinusoidal endothelial cells.

Adult↗
PubMed1995

Behaviour of the small GTP-binding protein rab6 in the liver of normal rats and rats presenting an acute inflammatory reaction.

While it is known that the small GTP-binding protein rab6 is localized in vitro to the Golgi apparatus of several mammalian cells, its behaviour in vivo has not yet been investigated. The aim of this work was to compare by immunocytochemistry and immunoblotting the distribution of rab6 in hepatocytes from normal rats and from rats with an acute inflammatory reaction, a circumstance where the synthesis and secretion of plasma proteins by the hepatocytes is increased and which is accompanied by several changes in the Golgi apparatus. Our results show that in normal rats, rab6 was present in all hepatocytes irrespective of the location of the cell in the hepatic lobule. At the ultrastructural level, rab6 was mainly visible on the three Golgi saccules, but in some cells it appeared to be absent in saccules corresponding to the cis or the trans saccule. The inflammatory reaction was accompanied by an increase of the immunocytochemical labelling at the light and electron microscopy levels. However, by immunoblotting, no differences in the total amount of rab6, nor in its subcellular distribution were found in liver cells after acute inflammatory reaction. These results demonstrate that rab6 is restricted in vivo to the Golgi apparatus and that no significant redistribution occurs during an acute inflammatory reaction.

Animals↗
PubMed1995

Effects of nicotinamide on hepatocyte viability and secretion of albumin and alpha 1-acid glycoprotein by adult rat hepatocytes in primoculture. Comparison with dexamethasone and recombinant human interleukin-6.

The effects of nicotinamide on hepatocyte viability and secretion of albumin and alpha 1-acid glycoprotein were studied in the absence or presence of dexamethasone and/or recombinant human interleukin-6 either after cell attachment (2 h) or after 24, 48, and 72 h of culture. The evolution of hepatocyte survival during the culture was appreciated by measurement of total DNA content. The secretion of albumin and alpha 1-acid glycoprotein was measured after a 4-h period following cell attachment or after 24, 48 and 72 h of culture. The important decrease of DNA content, mRNA levels and secretion of albumin and alpha 1-acid glycoprotein in control cultures after 2-3 days was not prevented by the addition of nicotinamide. In contrast, dexamethasone alone or with recombinant human interleukin-6 improved DNA content and albumin secretion with no additional effect of nicotinamide. The secretion of alpha 1-acid glycoprotein was largely induced by dexamethasone alone or dexamethasone and recombinant human interleukin-6. The increase of alpha 1-acid glycoprotein secretion was not modified by the addition of nicotinamide and averaged respectively 27- and 60-fold for dexamethasone alone and dexamethasone and recombinant human interleukin-6 after 48 h. These observations suggested that nicotinamide, at least in the conditions tested here, is unable to prevent alterations of hepatocyte viability and gene expression of cultured hepatocytes.

Animals↗
PubMed1995

Effects of female sex hormones on mitochondria: possible role in acute fatty liver of pregnancy.

Acute fatty liver of pregnancy occurs in some women. As other cases of microvesicular steatosis are due to impaired mitochondrial oxidation of fatty acids, we investigated the effects of female sex hormones on liver mitochondria in female mice. Three hours after administration of both estradiol (36 mumol/kg) and progesterone (150 mumol/kg), the in vitro beta-oxidation of [U-14C]palmitic acid and the activity of the tricarboxylic acid cycle decreased 49 and 54%, whereas the in vivo oxidation of [U-14C]palmitic acid decreased 38%. One week of treatment with both sex hormones produced ultrastructural lesions of mitochondria, decreased the recovery of mitochondrial proteins by 34%, increased state 4 respiration by 54-77%, and decreased the activities per gram of liver of several enzymes involved in the activation, mitochondrial uptake, and oxidation of fatty acids by 34-54%. We conclude that female sex hormones have deleterious effects on liver mitochondria and suggest that these effects, together with other factors, may contribute to the development of acute fatty liver of pregnancy in some women.

Acute Disease↗
PubMed1994

Renal and microvascular effects of an aldose reductase inhibitor in experimental diabetes. Biochemical, functional and ultrastructural studies.

Aldose reductase inhibitors, and particularly sorbinil, have been reported to prevent glomerular basement membrane thickening (GBMT) and albuminuria development in diabetic rats, but contradictory observations have been published. The aim of this study was to answer the following questions (i) is the corrective effect of sorbinil on GBMT, if confirmed, associated with an effect on collagen metabolism alterations? (ii) Is it associated with an effect on microvascular functional alterations? We therefore studied the influence of sorbinil on glucosyl-galactosyl-hydroxylysyl-glucohydrolase activity (GGHG; EC 3.2.1.107 which is involved in the catabolism of collagen disaccharide units), 3- and 4-hydroxyproline content and GBMT by ultrastructural morphometry in the kidney cortex of streptozotocin-diabetic rats after 5 months of disease. In parallel, the effects on albumin renal clearance and another functional alteration, the microvascular response to norepinephrine, were evaluated. We confirmed a corrective effect of sorbinil on both renal albumin clearance and GBMT. In the diabetic rats, sorbinil diminished the 3-hydroxyproline (but not the 4-hydroxyproline) content, whether expressed per mg protein or per total kidney cortex relative to body weight. Sorbinil reduced GGHG activity measured in the dialysed 10,000 g supernatant whether expressed per mg protein or per total kidney cortex; this activity has been shown to be increased in diabetes. Sorbinil also corrected the microvascular response to norepinephrine which is altered in diabetes.

Albuminuria↗
PubMed1994

Glucagon administration in vivo stimulates hepatic RNA and protein breakdown in fed and fasted rats.

Liver RNA and protein breakdown rates were measured simultaneously in fed and in 24 h-fasted rats during a short-term cyclic perfusion, 1 h after an intraperitoneal injection of glucagon or of saline. RNA was labelled in vivo by an intraperitoneal injection of [6-14C]orotic acid, 60 h before the start of the perfusion. The accumulation of radioactive cytidine and valine in the perfusion medium for 15 min was used to determine RNA breakdown and proteolysis respectively. The portal glucagon/insulin ratio was significantly higher in the fasted glucagon-treated rats than in their fed counterparts. Although glucagon administration significantly increased RNA and protein degradation rates in the fasted and in the fed groups, the effect was greater after 24 h of starvation. The relationship between these biochemical changes and the alterations of the hepatocyte lysosomal system was investigated by determining the fractional cytoplasmic volume of lysosomal structures (autophagic vacuoles and dense bodies) by morphometry in the fasted glucagon-treated rats and in their controls. Hyperlucagonaemia significantly enhanced the relative volume of autophagic vacuoles without affecting that of dense bodies. The results showed that hyperglucagonaemia induced in vivo stimulated both liver RNA and protein breakdown and that this effect was modulated by the nutritional status of the rats.

Animals↗
PubMed1994

Expression of complement-regulatory proteins in normal and UW-preserved human liver.

BACKGROUND/AIMS: Somatic cells are protected against complement-mediated injury by specialized membrane proteins, known as complement-regulatory proteins (CRP). The knowledge of the pattern of CRP expression in the liver is important to evaluate the role of complement-mediated injury in graft rejection. METHODS: We determined the distribution of four main CRP: membrane cofactor protein (MCP), decay accelerating factor (DAF), protectin, and complement receptor 1 (CR1) in 30 histologically normal livers, 13 samples from University of Wisconsin cold-storage solution (UW)-preserved tissue and 17 postoperative biopsies of UW-preserved allografts. RESULTS: In normal liver, hepatocytes expressed only MCP. Bile duct cells were reactive for MCP and protectin. Sinusoidal endothelial cells expressed MCP and protectin but displayed no or faint expression of DAF. Endothelial cells of portal vessels and centrilobular veins expressed high levels of DAF, MCP, and protectin. No expression of CR1 was observed. No change in CRP expression was usually detected after UW preservation, except for protectin, induced on hepatocytes in 9 samples of UW-preserved liver tissue and in 9 allografts. CONCLUSIONS: Hepatocytes and sinusoidal endothelial cells, which have a defective expression of CRP, might be at risk for complement-mediated injury. However, this risk is not aggravated after UW preservation.

Adenosine↗
PubMed1994

Expression of cytokine-dependent adhesion molecules in postreperfusion biopsy specimens of liver allografts.

BACKGROUND/AIMS: Allogeneic recognition of donor cells by host T lymphocytes requires the expression of cytokine-dependent molecules, such as class II major histocompatibility antigens, intracellular adhesion molecule 1 (ICAM-1), and lymphocyte function-associated antigen 3 (LFA-3). In the liver, activation of Kupffer cells after ischemic injury during the transplantation procedure may result in an early induction of cytokine-dependent molecules. METHODS: The pattern of induction of ICAM-1, HLA-DR, HLA-DQ, and LFA-3 was investigated in 30 postreperfusion surgical biopsy specimens of liver allografts by an immunohistochemical technique. RESULTS: Two patterns of induction were observed: focal or diffuse. On hepatocytes, ICAM-1 was induced in 22 cases (11 focal, 11 diffuse), HLA-DR in 18 cases (13 focal, 5 diffuse), HLA-DQ in 13 cases (3 focal, 10 diffuse), and LFA-3 in 1 case (focal). On bile duct cells, HLA-DR was expressed in 19 cases, associated with HLA-DQ in 7 cases. No induction of ICAM-1 and LFA-3 was detected. Compared with the other patients, the group of patients with diffuse postoperative hepatocellular induction of ICAM-1 was characterized by higher preharvesting serum transaminase levels in the donor (P < or = 0.001), suggestive of preoperative ischemic injury, and increased incidence of acute graft rejection (P = 0.04). CONCLUSIONS: Preoperative warm ischemia may modify the immunogenicity of liver allografts.

Adult↗
PubMed1994

Expression of cytokine-dependent immune adhesion molecules by hepatocytes and bile duct cells in chronic hepatitis C.

BACKGROUND/AIMS: The pathogenesis of liver cell injury in chronic hepatitis C is poorly understood. To test whether immune-mediated mechanisms might be involved in the pathogenesis of liver cell injury during infection by hepatitis C virus, the expression of cytokine-dependent immune molecules by hepatocytes and bile duct cells during chronic hepatitis C was studied. METHODS: In 35 patients, expression of class I and II HLA antigens, intercellular adhesion molecule (ICAM) 1, and lymphocyte function antigen (LFA) 3 was studied by immunohistochemistry and scored by a semiquantitative grading system. Statistical analysis was performed using Spearman's test and t test. RESULTS: Class I HLA antigens were induced on hepatocytes in 20 cases. In all cases, HLA-DR, ICAM-1, and/or LFA-3 were detected on hepatocytes in piecemeal necrosis and intralobular clusters. Bile duct cells expressed HLA-DR in 32 cases and ICAM-1 and LFA-3 in 14 cases. Expression levels of immune molecules on hepatocytes correlated with aminotransferase activity (P < 0.035), histological activity (P < 0.001), and score of necrosis (P < 0.01). ICAM-1 expression on hepatocytes was higher in patients with intraportal lymphoid nodules (P = 0.005). Expression levels of ICAM-1 and LFA-3 on bile ducts correlated with the severity of bile duct damage (P < 0.015). CONCLUSIONS: These results suggest the involvement of immune-mediated mechanisms in the pathogenesis of liver cell injury in chronic hepatitis C.

Adult↗