Beclin 1 mRNA strongly correlates with Bcl-XLmRNA expression in human hepatocellular carcinoma

Beclin 1 physically associates with Bcl-x(L) and is considered as a haploinsufficient tumor suppressor. As the role of Beclin 1 in hepatocellular carcinoma (HCC) is unknown, we determined Beclin 1 mRNA expression in 27 pairs of tumoral/nontumoral (T/NT) liver samples. The Beclin 1 mRNA T/NT ratio was less than 0.5 in 2 tumors and more than 2 in 1 tumor, and was positively correlated with the Bcl-X(L) mRNA T/NT ratio (P < 0.001), but not with the proliferating cell nuclear antigen mRNA T/NT ratio. Coregulation of Beclin 1 and Bcl-X(L) expression in HCC may suggest cooperation in the regulation of apoptosis.

Physical and functional cooperation between AP-1 and beta-catenin for the regulation of TCF-dependent genes

Stabilization of cytoplasmic beta-catenin is a hallmark of a variety of cancers. The stabilized beta-catenin is able to translocate to the nucleus, where it acts as a transcriptional activator of T-cell factor (TCF)-regulated genes. beta-Catenin may cross-talk with many signalling cascades to activate target genes. Whether beta-catenin cooperates with AP-1, another transcriptional complex activated during tumorigenesis is not fully clarified. We show that beta-catenin co-immunoprecipitates with c-Jun and c-Fos. GST pull-down experiments indicate a physical association of the armadillo repeat domain of beta-catenin with the DNA-binding domain of c-Jun and of the C-terminal domain of beta-catenin with the N-terminal domain of c-Fos. Promoter studies indicate that overexpression of AP-1 activates the transcription of two beta-catenin target genes, cyclin D1 and c-myc, by a mechanism independent of the AP-1 site, and fully dependent on the TCF-binding site. We further demonstrate that AP-1/beta-catenin synergism is involved during serum-induced cyclin D1 transcriptional activation. We identify a TCF-binding site on the cyclin D1 promoter which binds in vivo a complex induced by serum, containing beta-catenin, TCF4, c-Fos, c-Jun, JunB and JunD. This novel mechanism of interaction between two signalling cascades might contribute to the potentiation of malignancy.

Functional cooperation between JunD and NF-kappaB in rat hepatocytes

AP-1 and NF-kappaB are rapidly activated during liver regeneration. Whether these parallel inductions have potential functional implications is not known. Isolated rat hepatocytes were stimulated with two mitogens, epidermal growth factor or hepatocyte growth factor and with tumor necrosis factor alpha, a cytokine involved in the liver regenerative response in vivo and a strong inducer of NF-kappaB. All three cytokines increased AP-1 and NF-kappaB binding to their cognate cis-element and induced a 2.5-fold activation of NF-kappaB-dependent transcription. Inactivation of AP-1 by TAM67, a dominant negative mutant of AP-1 drastically inhibited basal and cytokine-induced NF-kappaB transactivation. Overexpression of Jun D, but not of the other Jun or Fos proteins increased by threefold NF-kappaB transactivation. Functional cooperation between JunD and p65 was demonstrated in a simple Gal-hybrid system. Finally, a twofold decrease in NF-kappaB transactivation was found in hepatocytes isolated from JunD(-/-) mice compared with hepatocytes from JunD(+/+) mice. Altogether these data demonstrate a functional cooperation of p65 with JunD, a major constituent of AP-1 in normal hepatocytes.

Potentiation of Smad transactivation by Jun proteins during a combined treatment with epidermal growth factor and transforming growth factor-beta in rat hepatocytes. role of phosphatidylinositol 3-kinase-induced AP-1 activation

Cross-talk between Smad and mitogen-activated protein kinase pathways has been described recently, and evidence for Smad cooperation with AP-1 is emerging. Here we report that epidermal growth factor (EGF) potentializes transforming growth factor beta (TGF-beta)-induced Smad3 transactivation in rat hepatocytes, an effect abrogated by TAM-67, a dominant negative mutant of AP-1. Antisense transfection experiments indicated that c-Jun and JunB were involved in the synergistic effect, and endogenous c-Jun physically associated with Smad3 during a combined EGF/TGF-beta treatment. We next investigated which signaling pathway transduced by EGF was responsible for the Jun-induced synergism. Whereas inhibition of JNK had no effect, inhibition of the phosphatidylinositol-3' kinase (PI3-kinase) pathway by LY294002 or by expression of a dominant negative mutant of PI3-kinase reduced EGF/TGF-beta-induced Smad3 transcriptional activity. Transfection of an activated Ras with a mutation enabling the activation of the PI3-kinase pathway alone mimicked the EGF/TGF-beta potentiation of Smad3 transactivation, and TAM-67 abolished this effect, suggesting that the PI3-kinase pathway stimulates Smad3 via AP-1 stimulation. The EGF/TGF-beta-induced activation of Smad3 correlated with PI3-kinase and p38-dependent but not JNK-dependent phosphorylation of c-Jun. Since potentiation of a Smad-binding element-driven gene was also induced by EGF/TGF-beta treatment, this novel mechanism of Jun/Smad cooperation might be crucial for diversifying TGF-beta responses.

Auxiliary liver transplantation: how to improve regeneration of the native liver by surgery

The technical factors which could influence regeneration of the native liver (NL) in auxiliary liver transplantation (ALT) for fulminant hepatic failure (FHF) are not well known. We studied NL regeneration according to the location of graft anastomosis in the recipient's portal system (superior mesenteric vein versus portal vein), and graft weight (50% reduced-size versus full-size graft) in a rat model of ALT with 80% reduction of the NL, and graft arterialization. NL regeneration was significantly more obvious when the graft was anastomosed on the recipient's superior mesenteric vein, thus establishing venous flow to the NL from the pancreas, the spleen, and the stomach, and when a full-size graft was used. The influence of portal venous flow on NL regeneration, assessed by 3H[-thymidine incorporation, was measurable as early as day 2. Both technical variables in combination resulted in significantly greater regeneration (ratio weight of NL/body weight at day 30: 2.32 +/- 0.68% versus 1.21 +/- 0.63% respectively, P = 0.02). Early preservation of portal flow to the NL is advisable to maximize NL regeneration in ALT. In any case, this regeneration is not impeded by the use of large auxiliary grafts.

Hepatocyte growth factor activates the AP-1 complex: a comparison between normal and transformed rat hepatocytes

BACKGROUND/AIMS

Stimulation of activator protein-1 (AP-1), a Fos/Jun complex, is a key event in the cell response to growth factors. We have investigated whether hepatocyte growth factor (HGF) induces differential AP-1 responses in normal and transformed rat hepatocytes, the 7777 cells.

METHODS

Primocultures of isolated hepatocytes or 7777 cells were stimulated with HGF. Gene expression was evaluated by ribonuclease protection assay and Western blot analysis. AP-1 DNA binding activity was measured by electrophoretic mobility shift assay. Identification of the proteins bound to the probes was made by supershift assays with specific antibodies. Cells were electroporated with plasmids containing an AP-1-dependent chloramphenicol acetyl transferase (CAT) gene, and CAT activity was measured 24 h after treatment with medium alone or HGF.

RESULTS

In both cell types, HGF triggered the same program of jun family mRNA activation, but distinct Fos/Jun proteins accumulated in the nucleus. HGF increased DNA-binding activity to the phorbol 12-O-tetradecanoate-13-acetate responsive element (TRE) in both cell types, but distinct TRE-binding proteins were recruited in the AP-1 dimers. HGF also increased consistently binding to a cAMP responsive element (CRE) in hepatocytes only. Finally, HGF triggered TRE- and CRE-dependent gene activations in hepatocytes but TRE-dependent gene activation alone in 7777 cells.

CONCLUSIONS

HGF-induced AP-1 activation leads to the formation of distinct dimers with different functional capacities in normal and transformed hepatocytes. These data suggest the importance of qualitative abnormalities of the AP-1 complex for the establishment or maintainance of a transformed phenotype.

Inducible expression of the alpha1-acid glycoprotein by rat and human type II alveolar epithelial cells

Alpha1-acid glycoprotein (AGP) is a major acute phase protein in rat and human. AGP has important immunomodulatory functions that are potentially important for pulmonary inflammatory response. The liver is the main tissue for AGP synthesis in the organism, but the expression of AGP in the rat lung has not been investigated. We show that AGP mRNA was induced in the lung of dexamethasone-, turpentine-, or LPS-treated rats, whereas AGP mRNA was not detected in the lung of control rats. In the lung of animals treated intratracheally with LPS, in situ hybridization showed that AGP gene expression was restricted to cells located in the corners of the alveolus, consistent with an alveolar type II (ATII) cell localization. The inducible expression of the AGP gene was confirmed in vitro with SV40 T2 cells and rat ATII cells in primary culture: maximal expression required the presence of dexamethasone. IL-1 and the conditioned medium of alveolar macrophages acted synergistically with dexamethasone. Rat ATII cells secreted immunoreactive AGP in vitro when stimulated with dexamethasone or with a combination of dexamethasone and the conditioned medium of alveolar macrophages. In vivo, in the human lung, we detected immunoreactive AGP in hyperplastic ATII cells, whereas we did not detect AGP in the normal lung. We conclude that AGP is expressed in the lung in cases of inflammation and that ATII cells are the main source of AGP in the lung.

Presence of distinct AP-1 dimers in normal and transformed rat hepatocytes under basal conditions and after epidermal growth factor stimulation

Activation of the transcriptional regulator AP-1, a dimeric complex formed of various combinations of Fos and Jun proteins, is a key step in the cellular response to mitogens. Because different dimers are believed to display different regulatory functions, we hypothesized that transformed cells that lack normal growth constraints might display AP-1 dimers that are different from those of normal cells. We therefore compared in primary and transformed rat hepatocytes (1) the composition of AP-1 dimers under basal conditions and (2) AP-1 induction by epidermal growth factor (EGF). Under basal conditions, AP-1 contained predominantly Jun homodimers in both cell types. However, whereas normal hepatocytes contained only JunD, both JunD and JunB were present in the AP-1 complex of 7777 cells. EGF treatment triggered almost identical programs of fos and jun gene activation at the messenger RNA (mRNA) level in both cell types, with an early accumulation of c-fos, c-jun, and junB mRNAs, but no change in junD mRNA levels. In both cell types, c-Fos and Fra-1 proteins increased after EGF treatment, but differences in the induction of Jun proteins were noted, with an increase of c-Jun in hepatocytes and an increase of JunB in 7777 cells. In both cell types, activation of AP-1 DNA binding activity by EGF was accompanied by the recruitment of Fra-1 into AP-1, detected earlier in 7777 cells than in hepatocytes, and with the transient appearance of c-Fos in 7777 cells only. Finally, EGF activated AP-1-dependent transcription in 7777 cells but not in hepatocytes. These data indicate important differences in the functional activity of AP-1 in transformed hepatocytes.

Hepatocarcinogenesis in woodchuck hepatitis virus/c-myc mice: sustained cell proliferation and biphasic activation of insulin-like growth factor II

Transgenic mice carrying the c-myc oncogene under control of woodchuck hepatitis virus (WHV) DNA sequences invariably develop hepatocellular carcinoma (HCC), despite a temporally limited expression of the transgene in the neonatal liver. To better characterize the different steps of the tumorigenic process, we analyzed the liver expression of the c-myc transgene and several growth-related genes by in situ hybridization and Northern blotting. In parallel studies, proliferated changes were investigated by detection of bromodeoxy-uridine-positive S-phase nuclei and apoptosis was evaluated by in situ nick end-labeling of DNA. During the neonatal period, high levels of c-myc messenger RNAs (mRNAs) were detected in all hepatocytes, and the expression of insulin-like growth factor II (IGF II) was frequently enhanced, correlating with increased cell proliferation. Despite elevated expression of the p53 gene, no change in liver cell apoptosis was observed. After weaning, c-myc transgene expression decreased to undetectable levels in all hepatocytes, whereas proliferation decreased but remained notably higher than in age-matched controls. The expression of c-fos, c-jun, and c-H-ras was highly variable during the preneoplastic period and in the tumors, with no consistent increase compared with controls. Resurgence of c-myc transgene expression was evidenced in all cells from hyperplastic lesions and carcinomas, accompanied with frequent focal reactivation of IGF II. Thus the strong proliferative stimulus induced by the combined effects of c-myc and IGF II in the neonatal liver might initiate a process characterized by persistent, dysregulated hepatocyte proliferation, in turn greatly increasing the risk of hepatocellular transformation.

Coexpression of periportal and perivenous enzymes in rat hepatocytes after experimental bile duct ligation: comparison with intrasplenically transplanted hepatocytes

The coexpression of normally periportal and perivenous markers has been described in heterotopically transplanted hepatocytes. To determine whether such a coexpression might also occur in hepatocytes retaining their original intrahepatic location, we compared in bile-duct-ligated livers and intrasplenically transplanted hepatocytes, the expression and distribution of the predominantly periportal glucose-phosphatase, succinate dehydrogenase, and lactate dehydrogenase, the predominantly perivenous glutamate dehydrogenase, NADPH-dehydrogenase, and beta-hydroxybutyrate dehydrogenase, and the strictly perivenous glutamine synthetase. The coexpression of high levels of the two periportal markers glucose-6-phosphatase and lactate dehydrogenase and of the perivenous marker NADPH dehydrogenase was observed in two situations: in clusters of hepatocytes isolated within the ductular proliferation in bile-duct-ligated livers and the majority of intrasplenically transplanted hepatocytes. The expression of glutamine synthetase was different according to the site. The protein was observed in certain intrasplenically transplanted hepatocytes bordering the splenic vessels but was never detected in hepatocyte clusters found in bile-duct-ligated livers. Our study therefore suggests that the coexpression of periportal and perivenous markers in the same hepatocytes is likely to be a non-specific consequence of the loss of the normal connections of hepatocytes with the normal liver microcirculation.

Direct solution hybridization of guanidine thiocyanate-solubilized cells for quantitation of mRNAs in hepatocytes

The sensitivity of direct solution hybridization of hepatocytes solubilized in guanidium thiocyanate (GuSCN) for detecting alpha 1-acid glycoprotein and albumin mRNAs was studied. The sensitivity of detection was inversely correlated with the DNA concentration. Raising the hybridization temperature from 20 to 37 or 50 degrees C (with formamide) increased the hybridization efficiency three- to fourfold in cell lysates with a high DNA concentration (1 microgram/microliter), whereas the hybridization efficiency was already maximal at 20 degrees C in diluted samples. It was most important to normalize all hybridization reactions with an internal standard, such as sense mRNA, because of the great variation in hybridization efficiency from one cell preparation to another depending on the DNA concentration. Direct hybridization of GuSCN cell lysates labeled in vivo with [6-14C]orotic acid was more efficient than hybridizing equivalent amounts of purified [6-14C]-labeled RNA, perhaps because of greater mRNA integrity and/or better recoveries of mRNA in GuSCN cell lysates. Therefore, direct solution hybridization of GuSCN-solubilized hepatocytes, which avoids the problem of RNA purification, appears to be a rapid, sensitive, and reliable method for quantifying mRNA in hepatocytes.

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.

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.

Activation of ras oncogene in livers with cirrhosis

Activation of cellular oncogenes and inactivation of anti-oncogenes have been postulated as important mechanisms during hepatocarcinogenesis. This study was conducted to detect abnormal levels of several proto-oncogenes (c-jun, c-fos, c-H-ras) and of the p53 and the alpha-fetoprotein gene in the liver during cirrhosis, a pathological process which predisposes to the development of hepatocarcinoma. Liver tissue from 11 patients with cirrhosis of different etiologies, and seven histologically normal liver fragments taken at the periphery of benign liver tumors of metastases were studied. Transcripts of the various oncogenes and of the alpha-fetoprotein gene were detected by in situ hybridization, and the p53 protein was revealed by immunocytochemistry. No overexpression of any of the mRNA tested or of the p53 protein was found in histologically normal liver in contact with benign or metastatic tumors. In contrast, 10 of the 11 specimens with cirrhosis (90.9%) displayed abnormally high levels of c-H-ras transcripts. Five samples with cirrhosis revealed a moderate increase in the level of c-fos mRNA. Only one case and two cases, respectively, exhibited increased levels of c-jun and alpha-fetoprotein mRNA. No cases were positive for the p53 antigen. Liver-cell proliferation, as assessed by immunocytochemistry with the Ki 67 monoclonal antibody, was low in both the group with cirrhosis and the control groups (0.49% and 0.55% positive cells, respectively). These data demonstrate that activation of c-H-ras mRNA is an almost constant finding in hepatocytes of livers with cirrhosis. This gene overexpression is not linked to hepatocellular proliferation.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of digitonin on the intracellular content of rat hepatocytes: implications for its use in the study of intralobular heterogeneity

Anterograde or retrograde perfusion of rat liver with digitonin selectively permeabilizes the periportal or the perivenous zone of the hepatic lobule. Digitonin perfusion is used to analyze the effluents released by permeabilized hepatocytes or, combined with collagenase perfusion, to obtain cell suspensions enriched in either periportal or perivenous hepatocytes. Despite the wide use of digitonin to study lobular heterogeneity, its affects on rat hepatocytes are not well documented. We therefore analyzed the effects of digitonin perfusion on the intracellular content of rat hepatocytes by combining electron microscopy, histoenzymology, immunohistochemistry, and in situ hybridization. At the concentration currently used for the study of lobular heterogeneity, digitonin perfusion induced a marked cytosolic clarification of permeabilized hepatocytes, while most organelles except mitochondria were well preserved. In the digitonin-altered zones, there was no histochemical detection of non-membrane-bound enzymes (lactate dehydrogenase, glutamate dehydrogenase), whereas membrane-bound enzymes (succinate dehydrogenase, beta-hydroxybutyrate dehydrogenase, NADPH dehydrogenase, glucose-6-phosphatase) were still detected. Immunohistochemistry and in situ hybridization revealed significant amounts of several plasma proteins (albumin, alpha 2-macroglobulin, alpha 1-inhibitor 3, alpha 1-acid glycoprotein) and their respective mRNAs in digitonin-permeabilized hepatocytes. The demonstration that digitonin-permeabilized hepatocytes retain many intracellular constituents shows that biochemical analysis of cellular effluents released from digitonin-permeabilized hepatocytes must be interpreted with caution and that the apparent characteristics of cell suspensions obtained by the digitonin-collagenase technique might be significantly altered by contamination with permeabilized hepatocytes from the opposite zone.

Parenchymal innervation of normal and cirrhotic human liver: a light and electron microscopic study using monoclonal antibodies against the neural cell-adhesion molecule

Hepatic innervation participates in the control of sinusoidal blood flow and in the regulation of certain metabolic functions of the liver. The study of the distribution of hepatic nerves has been hampered by the lack of adequate markers. We therefore tested the value of the neural cell-adhesion molecule (NCAM) as a probe for the study of parenchymal nerves in the normal and cirrhotic human liver. Four antibodies against various epitopes of NCAM were tested by light and electron microscopic immunohistochemistry: Leu19, ERIC-1, VC1.1, and HNK-1. Their reactivity was compared with that of antibodies against the following neural cell markers: S100 protein, neurofilaments, and neuron-specific enolase (NSE). The tissue reactivity of anti-NCAM antibodies was variable, suggesting a microheterogeneity of the NCAM molecule in the normal liver. Clones Leu19 and ERIC-1 proved to be the most sensitive of the anti-NCAM antibodies. Their sensitivity was superior to that of the antibodies directed against the other neural cell markers tested. In the normal liver, both Leu19 and ERIC-1 demonstrated a heterogeneous distribution of nerve fibers inside the hepatic lobule. Intralobular nerve fibers predominated in Zone 1. This might contribute to the constitution of distinct zonal microenvironments inside the hepatic lobule. In cirrhosis, no nerve fiber was detected inside parenchymal nodules; no nerve plexus was visible at the contact of proliferating neoductules. These alterations might contribute to the pathogenesis of the hemodynamic and metabolic disorders observed in cirrhosis.

Activation of nuclear protooncogenes and alpha-fetoprotein gene in rat liver during the acute inflammatory reaction

Nuclear protooncogene and alpha-fetoprotein gene expression is stimulated in hepatocytes during liver regeneration and by various growth factors in vitro. Metabolic adaptation of hepatocytes has been implicated in such gene reprogrammation. We examine here whether induction of an acute inflammation, a physiological situation of important metabolic adjustments, also triggers activation of nuclear oncogenes and of the AFP gene in rat liver. C-fos, c-jun and c-myc mRNA accumulated on Northern blots between 4-12 h of inflammation and the steady-state level of two small alpha-fetoprotein transcripts characteristic of the adult liver increased at 4 h and 24 h of inflammation. In situ hybridization showed accumulation of the mRNA of the four genes studied in all hepatocytes, without any zonal lobular heterogeneity. 3H-histoautoradiography and mitotic counts indicated an inhibition of DNA synthesis and mitosis, prolonged for at least 48 h after inflammation. Thus acute inflammation triggers the activation of nuclear protooncogenes and alpha-feto-protein gene in hepatocytes, but this activation is not followed by passage into the replicative cycle.

Nuclear oncogenes and alpha-fetoprotein gene expression in hepatoma cell lines

We have previously demonstrated a correlation between the kinetics of activation of the nuclear oncogenes c-fos, c-jun and c-myc and the alpha-fetoprotein (AFP) gene in adult rat hepatocytes proliferating in culture, which led us to raise the hypothesis of a possible regulation of the AFP gene by nuclear oncogenes. Whether the mechanisms of AFP gene expression in normal and transformed hepatocytes are similar is unknown. In this study we have searched for a possible correlation between the basal level of AFP gene expression, by several hepatoma cell lines that express the AFP gene differently, and the basal level of expression of the nuclear oncogenes c-fos, c-jun and c-myc. The analysis has been performed at the mRNA and protein levels. Our results demonstrate that cell lines that strongly express the AFP gene do not express higher levels of nuclear oncogenes than cell lines with weak expression of the AFP gene. These results, therefore, do not support a direct involvement of nuclear oncogenes on the basal level of AFP gene expression in hepatoma cell lines.

Increased efficiency of gene transfection in primary cultures of adult rat hepatocytes stimulated to proliferate: a comparative study using the lipofection and the calcium phosphate precipitate methods

Transfection of the beta-galactosidase gene in quiescent cultures of adult rat hepatocytes with the calcium phosphate precipitate or the lipofection methods gave a higher level of beta-galactosidase gene expression with the lipofection than with the calcium phosphate precipitate method, but the transfection efficiency was weak in both cases. Transfection of hepatocytes stimulated to proliferate before transfection either in vivo by partial hepatectomy or in vitro by epidermal growth factor was more efficient than transfection of quiescent hepatocytes, and the lipofection method gave better results than the calcium phosphate precipitate method.

Cellular analysis of the kinetics of alpha-fetoprotein and nuclear oncogene activation in primary cultures of adult rat hepatocytes stimulated by epidermal growth factor

Alpha-fetoprotein (AFP), a fetal gene normally inactivated in quiescent adult hepatocytes, is re-expressed in hepatocytes during the proliferating response induced by liver regeneration in vivo, or epidermal growth factor (EGF) in vitro. The nuclear oncogenes c-jun, c-fos and c-myc are 'immediate early' genes also activated during the proliferative response of hepatocytes. Whether AFP gene activation is linked to oncogene activation is not known. As a first step in answering this question, we have analysed the cellular kinetics of nuclear oncogene and AFP gene activation in primary cultures of adult rat hepatocytes stimulated by EGF. Gene activation was evaluated at the mRNA level by dot blot and in situ hybridization, and at the protein level by immunoperoxidase. C-jun, c-fos and c-myc mRNA steady state levels in total cellular RNA were increased from 30 min-2 h after EGF stimulation. In situ hybridization analysis showed that transcripts of the three oncogenes increased in all hepatocytes after EGF stimulation. While unstimulated cultures did not immunostain for Fos and Myc proteins. Fos immunostaining was visible in the majority of hepatocyte nuclei 1 and 2 h after EGF addition, and Myc cytoplasmic immunostaining of the majority of hepatocytes was observed at 2 h of stimulation. AFP mRNA increased in total cellular RNA 2 and 4 h after EGF stimulation, with elevated in situ hybridization signal for AFP mRNA in all hepatocytes. No hepatocytes immunostained for AFP in unstimulated cultures, but a cytoplasmic labeling of 20-30% of the hepatocytes was observed 6 h after stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional hepatocellular heterogeneity for the production of plasma proteins

It is now well established that hepatocytes are the main liver cells responsible for the synthesis of plasma proteins produced by the liver. That these cells are not specialized in the production of the different plasma proteins is also well established. Presently the point still debated is whether a functional hepatocellular heterogeneity exists for plasma protein synthesis as for many other hepatocyte functions. Several physiological and pathological situations suggest that this heterogeneity takes place in the hepatocytes of two opposite hepatic lobular zones, the periportal and centrilobular zones. However, this zonal difference, which supposes different regulatory mechanisms, must be confirmed by techniques other than the now classical immunocytochemistry or the in situ hybridization technique recently proposed for the demonstration of mRNAs in hepatocytes. Another hepatocellular heterogeneity, the intercellular heterogeneity, which can be observed in the same lobular zone, is more difficult to analyze, but shows that from hepatocyte to hepatocyte a variation exists in the synthesis of a given plasma protein.

Orthotopic liver transplantation with hepatic artery anastomoses. Hemodynamics and response to hemorrhage in conscious rats

Orthotopic liver isotransplantation was performed in one group of Lewis rats using cuffs for the portal vein and the infrahepatic vena cava, stents for the hepatic artery and the bile duct. Three other groups were also investigated: group A, normal rats; group B, sham-transplanted rats (clamping of the vessels, washing of the liver, placing cuffs around the portal vein); and group C, sham-transplanted rats with ligature section of the hepatic artery. Blood-flow measurements were performed, 1 week after the surgical procedure, with the radioactive microsphere method in conscious animals. Transplanted rats exhibited significant (ANOVA, P less than 0.05) increase in cardiac index and decrease in mean arterial pressure and systemic vascular resistance. Blood flows of the portal territory and to the kidneys were not significantly modified. Arterial liver blood flow and arterial liver vascular resistance in rats with liver transplantation were not significantly different between normal and sham-transplanted rats but were significantly different from rats with ligature of the hepatic artery. These results confirm the validity of the method used for vascular anastomoses. Hypotensive hemorrhage (2 ml/100 g bw) induced marked hemodynamic changes, but rats with liver transplantation when compared with normal and sham-transplanted rats exhibited the following: (a) significantly lower percentage of decrease in cardiac index and in mean arterial pressure; and (b) significantly higher renal and portal tributary blood flows. Plasma catecholamine concentrations and plasma volume were higher in rats with liver transplantation than in normal rats but were not significantly different from sham-operated rats. Histologic examination of the liver revealed slight portal edema in sham-operated rats and small necrotic areas in the liver, probably corresponding to the reperfusion injury, in rats with liver transplantation. In conclusion, the method described for the four vascular anastomoses allows functional perfusion of the transplanted liver. Rats with liver transplantation exhibited a hyperkinetic circulatory syndrome and an improved tolerance to hemorrhage. Changes in plasma catecholamine concentrations and in plasma volume did not account for the hemodynamic changes.

In situ hybridization: application to the study of gene expression during experimental hepatocarcinogenesis and human hepatocellular carcinoma

The possibility of detecting specific mRNA directly within tumor cells offered by the in situ hybridization (ISH) technique has provided a new dimension to the study of experimental and human hepatocarcinogenesis. The combination of ISH and immunocytochemical techniques on the same or adjacent tissue sections provides a more complete picture of the various changes in gene expression. ISH may also detect posttranscriptional abnormalities of gene expression at the cellular level, such as expression of mRNA with no protein translation, or translation with decreased efficiency. Undoubtedly, the development of the ISH technique will open a new area for the understanding of the complex molecular events leading to cancer.

Heterogeneous lobular distribution of hepatocytes expressing acute-phase genes during the acute inflammatory reaction

Functional heterogeneity in the lobule with regard to plasma protein synthesis is still debated. Therefore, we have localized in liver sections from normal rats and from rats with turpentine-induced AIR the mRNA and protein products of three genes with different alterations in their hepatic expression during an AIR: alpha 2M and alpha 1PI, two positively reacting acute-phase genes, and alpha 1I3, a negative acute-phase reactant. In normal liver, all hepatocytes expressed alpha 2M and alpha 1I3 mRNA, but a preferential expression of alpha 2M and alpha 1I3 mRNA and protein in the PP and ML zones was observed. During an AIR, the level of alpha 2M mRNA increased fourfold in the cytoplasm of PP and ML hepatocytes, while the level of cytoplasmic alpha 1I3 mRNA was decreased about fourfold in the same zones, with parallel variations in the expression of the corresponding proteins. In contrast, no significant modulation of the RNA and protein concentrations of both genes was detected in PV areas. alpha 1PI mRNA was expressed at the same levels in the three lobular zones in normal liver, but staining for the alpha 1PI protein was more intense in the PV zones. During the acute-phase response alpha 1PI mRNA levels were increased twofold in all three lobular zones, and alpha 1PI staining became homogeneous within the lobule. These results demonstrate that the location of a hepatocyte with the liver lobule can influence the expression of the three genes under study both at pre- and post-translational levels, in basal conditions, as well as during modulation of their expression during the inflammatory reaction.

Cellular expression of alpha-fetoprotein gene and its relation to albumin gene expression during rat azo-dye hepatocarcinogenesis

During hepatocarcinogenesis, alpha-fetoprotein (AFP) synthesis may be dramatically increased while albumin synthesis is frequently decreased. Therefore, a reciprocal modulation between both gene expressions has been hypothesized. In this work, we combined in situ hybridization and immunoperoxidase on parallel liver tissue sections in order to analyze at the cellular level, AFP gene expression and its relation to ALB gene expression in both early and neoplastic lesions induced by 3MeDAB in the rat. In early lesions, cell populations were heterogenous as regards AFP expression. High levels of AFP transcripts were detected both in oval type cells and in a subset of basophilic hepatocytes within preneoplastic lesions. In these two highly AFP-expressing cell populations, significant levels of ALB transcripts were concomitantly detected. In the majority of altered hepatocytes, no AFP expression was detected while the level of ALB expression was decreased. In neoplastic lesions, AFP expression was strikingly heterogenous and independent from the degree of morphological differentiation. No evidence of reciprocal modulation with ALB gene expression could be assessed. In both preneoplastic and neoplastic lesions, a few altered hepatocytes displayed significant levels of AFP transcripts while no corresponding protein could be detected; such a discrepancy was not observed for ALB. This work shows that during 3MeDAB hepatocarcinogenesis, AFP gene activation occurs in heterogenous cell populations and according to different cellular patterns. Our observations lend no support to the hypothesis of a reciprocal modulation between AFP and ALB gene expressions during rat azo-dye hepatocarcinogenesis.

[In situ hybridization: principles and applications]

In situ hybridization is a molecular biological technique recently introduced in histology. Its principle consists of forming stable nucleic hybrids in tissues or cells. In this review, the main steps of the technique are discussed in regard to the preparation of probes and their labelling, the fixation of tissues and cells and their permeabilization in order to facilitate the penetration of labelled probes. Conditions of hybridization and requisite control reactions are also analysed. Quantification possible when radioactive probes are used is detailed. The three current applications of in situ hybridization, the localization of a gene on a chromosome, the demonstration of viral genomes in cells and the investigation of messenger RNAs coding for a determined protein, are illustrated with specific examples.

Alpha fetoprotein and albumin gene transcripts are detected in distinct cell populations of the brain and kidney of the developing rat

We report the cellular localization of alpha-fetoprotein (AFP) and albumin (ALB) gene transcripts in rat kidney and brain as detected by in situ hybridization on tissue sections with [35S]-labelled alpha-fetoprotein and albumin cDNA probes. Both types of mRNA were present in distinct cell populations of the developing kidney and brain. In the kidney, both gene transcripts were distributed over all developing tubular cells in the 20-day-old fetus. During the first 3 weeks of life, a gradual decrease in the expression of AFP and ALB mRNA was apparent, the rate of decrease being greater on proximal tubules than on the other tubular cells. From the 4th week onwards, a weak signal for both mRNAs persisted in the majority of the tubular cells. In the brain, all neuronal cells expressed both genes. Transcript cellular distribution was mainly cytoplasmic during fetal and early postnatal life and became predominantly nuclear at 3, 4 and 5 weeks, suggesting that posttranscriptional mechanisms are involved in the control of AFP and ALB gene expression at these stages. In the adult brain no significant signal was recorded thereafter. Coexpression of AFP and ALB transcripts by specific cell types, together with their gradual disappearance concomitant with postnatal organ maturation, suggests a possible role for these proteins in terminal differentiation processes of tubular and neuronal cells.

Cellular analysis of alpha-fetoprotein gene activation during carbon tetrachloride and D-galactosamine-induced acute liver injury in rats

To analyze the cellular mechanisms of alpha-fetoprotein (AFP) gene activation during liver regeneration, we have measured the steady-state level of liver AFP mRNA by dot blot and revealed AFP transcripts and protein in liver sections by in situ hybridization and immunoperoxidase. AFP gene activation was studied from rats intoxicated with carbon tetrachloride or D-galactosamine, two toxics inducing different patterns of liver necrosis and regeneration. At 48 and 72 hours of carbon tetrachloride intoxication, liver AFP mRNA steady-state levels were slightly increased. On liver sections, large necrotic centrilobular areas were apparent with a 7- to 10-fold increase of hepatocyte mitotic index as compared with controls. At the same times of intoxication, a 2-fold increase in the signal level for AFP mRNA over all nonnecrotic hepatocytes was observed, whereas the protein remained undetectable in most of the hepatocytes. In contrast, after D-galactosamine intoxication, no increase of AFP mRNA steady-state levels was detectable. Scattered necrotic hepatocytes were visible at 48 and 72 hours of intoxication, with only a 2-fold increase of hepatocyte mitotic index, as compared with controls. Moreover, while the hybridization signal level for AFP mRNA was not increased over hepatocytes, large amounts of AFP mRNA and protein were detected in proliferated oval cells and bile duct-like structures. These results suggest that at least two distinct mechanisms at the cellular level may explain AFP gene activation during chemically-induced liver regeneration: (a) a moderate increase of AFP mRNA by all the remaining hepatocytes probably linked to their reentry into the proliferative cycle, which appears the main mechanism after carbon tetrachloride intoxication, and (b) a quantitatively important AFP expression by a small number of proliferated cells with new phenotypes (oval cells and bile-duct like structures), observed in the D-galactosamine model.

Model for the study of portal-systemic collateral vascular resistance in the conscious rat

In order to obtain a model for the study of portal-systemic collateral vascular resistance, total portal vein occlusion was performed in rats 48 hr or 3 wk after partial obstruction. Four groups of conscious restrained rats were studied: a) sham-operated, b) partial portal vein ligated, c) 48 hr-total portal vein occluded, and d) 3 wk-total portal vein occluded. In comparison with the sham group, the three portal vein ligated groups had significantly higher cardiac output, portal tributary blood flow, portal pressure (7.7 +/- 0.4 versus 13.5 +/- 0.5, 13.6 +/- 0.8, and 17.7 +/- 1.1 mmHg, mean +/- SE, respectively) and hepatic arterial blood flow (5.8 +/- 0.6 versus 9.5 +/- 0.7, 8.3 +/- 0.5, and 13.9 +/- 1.9 ml/min, respectively). Cardiac output and portal tributary blood flow did not differ between the portal vein ligated groups, but portal pressure and hepatic arterial blood flow were significantly higher in the 3 wk-total portal vein occlusion group. The 3 wk-total portal vein occlusion group showed 99.1 +/- 0.3% shunting, different from the partial (29.7 +/- 16.9%, p less than 0.01) and 48 hr-total portal vein occlusion (46.5 +/- 14.7%, p less than 0.05) groups. Portography confirmed absence of portal-portal collaterals in the 3 wk-total portal vein occlusion group. It is suggested that rats with 3 wk-total portal vein occlusion are useful for the study of acute modifications of portal-systemic collateral circulation, as shunting is total and consistent in this model.

In situ cellular analysis of alpha-fetoprotein gene expression in regenerating rat liver after partial hepatectomy

Cellular analysis of hepatic alpha-fetoprotein gene expression in normal adult rat and during regeneration induced by partial hepatectomy was performed at the cellular level by in situ hybridization using 35S-labeled complementary DNA probes and immunoperoxidase techniques. In normal adult rat liver sections, a few alpha-fetoprotein mRNA-cDNA hybrids are detected over all hepatocytes. No protein is detected with routine immunoperoxidase methods. However, after in vivo colchicine blockade of alpha-fetoprotein secretion, 10 to 20% alpha-fetoprotein-positive hepatocytes are observed. In regenerating livers, at 2,6 and 24 hr (before and at the time of the peak of DNA synthesis in the periportal zones), a rise of the nuclear signal level is observed selectively in periportal hepatocytes, without modification of the cytoplasmic signal. At 48 hr (when most hepatocytes have completed at least one replicative cycle), almost all hepatocytes throughout the liver lobule display a rise of the nuclear (2- to 3-fold) and cytoplasmic (1.5- to 2-fold) signal level compared to nonoperated rats. These data show that all hepatocytes in the adult liver express a small number of alpha-fetoprotein mRNA sequences; they appear to be translated in protein whose secretion can be blocked by colchicine. The moderate increase in alpha-fetoprotein gene expression induced by liver regeneration takes place in all hepatocytes, in apparently two distinct steps: a very early nuclear accumulation of alpha-fetoprotein mRNA sequences and a late cytoplasmic accumulation of alpha-fetoprotein mRNA molecules.

Albumin and alpha-fetoprotein gene expression in various nonhepatic rat tissues

Albumin and alpha-fetoprotein (AFP), two major serum proteins, are synthesized predominantly in the liver and yolk sac of mammals. In the present paper we report on the developmental expression of the corresponding genes in nonhepatic rat tissues. Significant quantities of mature albumin and AFP mRNAs were revealed in kidney, pancreas, heart, and lung of fetal and/or newborn rats using dot blot and Northern blot assays. Very low levels of these mRNA sequences were also detected in adult kidney and pancreas using sensitive RNA-cDNA solution hybridization assays. In situ hybridization analysis revealed that the albumin and AFP gene transcripts are present in the tubular cells of the 20-day-old fetal kidney. In order to elucidate further the mechanisms governing this expression, we studied the chromatin structure and methylation pattern in the 5'-end of these two genes. A faint band, corresponding to a specific DNase I-hypersensitive site upstream from the albumin gene, was detected in the fetal and neonatal kidney nuclei but not in adult kidney. For both genes, a site CG, demethylation of which is correlated with expression in liver and hepatoma cell lines, is highly methylated in fetal kidney even though AFP and albumin genes are expressed. Taken together, these results show the presence of a cell population in the rat kidney that actively transcribes both the albumin and AFP genes. The expression of these genes may be mediated by mechanisms differing in at least some steps from those exerted in the liver.

Detection of albumin mRNAs in rat liver by in situ hybridization: usefulness of paraffin embedding and comparison of various fixation procedures

Our aim was to define optimal conditions for efficient and reproducible albumin mRNA detection in rat liver by in situ hybridization. We used an albumin-specific [3H]-labeled cDNA probe with a specific activity of 6-8.10(6) cpm/microgram DNA. In situ hybridization is as efficient on paraffin sections as on cryostat sections for detecting albumin mRNAs. Perfusion fixation with a 4% paraformaldehyde solution results in homogeneous RNA retention within tissue blocks, in contrast with immersion fixation, which yields heterogeneous RNA preservation. Comparison of immersion fixation with three different fixatives (paraformaldehyde, ethanol-acetic acid, and Bouin's fixative) shows that the highest level of hybridization signal is obtained with paraformaldehyde. Ethanol-acetic acid and Bouin's fixative appear less efficient for albumin mRNA detection. Loss of mRNAs within liver tissue blocks over time is largely although not completely prevented by paraffin embedding.

Cellular analysis by in situ hybridization and immunoperoxidase of alpha-fetoprotein and albumin gene expression in rat liver during the perinatal period

To analyze at the cellular level the decrease in alpha-fetoprotein (AFP) gene expression during the early postnatal growth, we searched for AFP gene transcripts by in situ hybridization using a specific cDNA probe, and for the corresponding protein by immunocytochemistry, on rat liver sections at various times of the perinatal period. The relative number of mRNA sequences was evaluated by Northern blot analysis. Albumin (ALB) gene expression was studied simultaneously with the same techniques. In 17-19-d-old fetuses all hepatocytes express simultaneously, for both genes, the mRNAs and the corresponding proteins. During the first postnatal weeks, at a time when the global number of AFP mRNA molecules decreases, all hepatocytes still contain cytoplasmic transcripts and protein. A zonal heterogeneity in the level of AFP gene expression develops around the first week, a higher number of gene products being detected in perivenous than in periportal hepatocytes. This heterogeneity persists until the fourth week when AFP mRNA sequences and protein are barely detectable. All hepatocytes express the ALB gene after birth, but at around the second week, a periportal intensification of the in situ hybridization signal and immunostaining becomes apparent. Our data indicate that co-expression of the AFP and ALB genes by all hepatocytes is a normal step in liver ontogeny; the diminution of AFP gene expression after birth is not the result of the disappearance of specialized cell clones; and zonal quantitative differences in the level of AFP and ALB gene expression are observed within the maturing liver lobule.

Inhibitory effect of the acute inflammatory reaction on liver regeneration after partial hepatectomy in the rat

We evaluated the influence of an acute inflammatory reaction that triggers the synthesis of exportable proteins by hepatocytes on liver regeneration after partial hepatectomy, which induces the synthesis of proteins necessary for liver cell proliferation. In hepatectomized rats with a turpentine-induced acute inflammatory reaction, the first peaks of hepatic DNA synthesis and mitosis were significantly inhibited compared with pair-fed controls subjected to partial hepatectomy only, and the liver DNA concentration at various times after partial hepatectomy was significantly lower in the former than in the latter. Inhibition was not obtained when the acute inflammatory reaction was induced 12 h or more before partial hepatectomy, suggesting that the inhibitory effect of turpentine administration depended on early events in the acute inflammatory reaction. These data suggest that one possible mechanism responsible for inhibition of regeneration might be competition at the transcriptional or the translational level between liver syntheses of various proteins, and that, under certain conditions, liver-specific functions might take precedence over regenerative functions.

Myeloid metaplasia, perisinusoidal fibrosis, and nodular regenerative hyperplasia of the liver

We describe two patients with myeloid metaplasia in whom portal hypertension resulted, not from infiltration of the liver sinusoids by myeloid cells, but from perisinusoidal fibrosis and nodular regenerative hyperplasia of the liver. We hypothesize that myeloid metaplasia induced the development of perisinusoidal fibrosis, which resulted in heterogeneous hepatic tissue blood perfusion, with atrophy of the liver cells in the underperfused areas and nodular regenerative hyperplasia in the normally perfused areas.

Liver perisinusoidal fibrosis in BB rats with or without overt diabetes

Perisinusoidal fibrosis is a vascular lesion observed in the liver of type I diabetic patients. To investigate whether this liver lesion is secondary to hyperglycemia or whether it represents a separate collagen vascular disorder, the authors studied the structure of liver sinusoids in genetically susceptible BB rats in which a spontaneous diabetes develops similar to human type I diabetes. Seven diabetic insulin-treated BB rats, 7 nondiabetic BB rats, and 6 control non-BB rats were studied. Histologic abnormalities of the collagen network were detected on trichrome-stained sections. Perisinusoidal collagen fibers were quantified ultrastructurally by the point-counting method. All control non-BB rats had normal livers; 86% of the diabetic as well as 71% of the nondiabetic BB rats displayed localized sinusoidal thickening corresponding ultrastructurally to perisinusoidal fibrosis; in these abnormal rats the percentage of collagen fibers per sinusoid unit was significantly higher than that in controls. Fibrous septa (2 diabetic and 5 nondiabetic BB rats) and liver nodulation (3 diabetic and 1 nondiabetic BB rats) were also observed. Perisinusoidal fibrosis is a frequent liver vascular abnormality in a strain of rats genetically predisposed to the development of type I diabetes. The lesion is independent of the presence of diabetes. These observations suggest that liver perisinusoidal fibrosis in patients with type I diabetes might be linked to a genetic abnormality rather than to hyperglycemia per se.

All hepatocytes are involved in the expression of the albumin gene in the normal adult rat: a demonstration by in situ hybridization and immunoperoxidase techniques

Immunoperoxidase techniques have yielded conflicting results concerning the percentage of hepatocytes engaged in albumin production in normal adult rats. In addition, the question of whether functional differences in the synthesis of plasma proteins exist within the hepatic lobule remains to be determined. To clarify these questions, we have searched for gene albumin transcripts by in situ hybridization, and for the corresponding protein by immunoperoxidase, on adjacent liver sections. We observed that all hepatocytes contain albumin transcripts as well as the albumin protein, without any detectable zonal variation within the liver lobule. Taken altogether, these results demonstrate that every hepatocyte, whatever its location in the hepatic lobule, is actively engaged in albumin gene expression.

Peliosis-like ultrastructural changes of the hepatic sinusoids in human chronic hypervitaminosis A: report of three cases

In addition to hypertrophy of Ito cells and perisinusoidal fibrosis, previously unrecognized ultrastructural abnormalities of the hepatic sinusoids were observed in three patients with chronic hypervitaminosis A: 1) large areas of communication between the sinusoidal lumina and the perisinusoidal spaces, allowing extravasation of blood cells; 2) marked dilation of the perisinusoidal spaces; and 3) swelling and clarification of endothelial cells. Most of these changes, along with some other sinusoidal barrier alterations previously reported in chronic hypervitaminosis A (i.e., bleb formation on the sinusoidal membrane of the hepatocytes and the presence of multiple cellular layers lining the sinusoids), are strikingly similar to those observed in peliosis hepatis. The present findings suggest that sinusoidal barrier abnormalities might constitute a major event in the pathophysiology of vitamin A-induced liver injury as well as of peliosis hepatis.

In situ ultrastructural detection and quantitation of liver mononuclear phagocytes in contact with hepatocytes in chronic type B hepatitis

An ultrastructural cytochemical method for detection of endogenous peroxidase was used to quantify the mononuclear phagocytes present in areas of tissue injury, i.e., in membrane contacts with hepatocytes, in liver biopsies from 12 patients with chronic type B hepatitis; 10 of them exhibited stable disease activity of various degrees of severity, and the other two displayed acutely exacerbated disease activity. Results were compared with those for three patients with acute type B hepatitis. The total percentage of mononuclear phagocytes was higher in patients with chronic hepatitis with stable high disease activity than in patients with stable low disease activity (31.3 +/- 7.4 versus 15.6 +/- 4.7%, p less than 0.01). Furthermore, in the former group of patients, recently recruited macrophages were significantly more frequent than in patients with low disease activity (11.6 +/- 4.0 versus 3.5 +/- 3.6%, p less than 0.01), and macrophages often displayed a markedly hypertrophied cytoplasm with numerous phagolysosomes, suggestive of an activated state. On the other hand, no significant differences in the percentage of the other leukocytes in contact with hepatocytes (lymphocytes, plasmocytes, and polymorphonuclear leukocytes) were noted between patients with high and low disease activity. In the three biopsies obtained from two patients with chronic hepatitis with acute exacerbation of disease activity, the profile of the leukocytes in contact with hepatocytes strikingly resembled the one observed in the three patients with acute type B hepatitis. In both instances, mononuclear phagocytes were rare, and a higher proportion of lymphocytes was observed than in patients with stable chronic liver disease activity. These results suggest that the mechanisms of hepatocyte necrosis in chronic type B hepatitis may differ from that in acute hepatitis due to this virus. Although lymphocyte-mediated mechanisms are likely to be predominant during acute episodes of hepatocyte necrosis, mechanisms mediated by mononuclear phagocytes might play a significant role in the low grade of hepatocyte necrosis characteristic of stable chronic type B hepatitis.

A quantitative ultrastructural analysis of the leukocytes in contact with hepatocytes in chronic active hepatitis, with a cytochemical detection of mononuclear phagocytes

In an attempt to characterize in vivo the immune cells cytotoxic to hepatocytes in patients with chronic active hepatitis (CAH), a quantitative ultrastructural analysis of leukocytes in close contact with hepatocytes was performed in 13 patients with untreated HBsAg-negative CAH. Mononuclear phagocytes were identified by detection of endogenous peroxidase. Of the leukocytes, 8.3-4.1% were mononuclear phagocytes, 12.5-25.8% were large lymphocytes with a prominent secretory apparatus, assumed to represent mostly killer cells (T-cytotoxic cells and/or null cells), 12.2-56.8% were small lymphocytes poor in cytoplasmic organelles, and 0-45.8% were plasma cells. Patients with high serum transaminase levels had significantly more mononuclear phagocytes (P less than 0.001) and significantly fewer plasma cells (P less than 0.001) and small lymphocytes (P less than 0.001) than patients with lower disease activity. The profile of the leukocytes in contact with hepatocytes in these CAH patients suggests that mononuclear phagocyte-mediated mechanisms play an important role in hepatocyte necrosis in vivo.

Ultrastructural aspects of the liver perisinusoidal space in diabetic patients with and without microangiopathy

To determine whether abnormalities of the perisinusoidal space of Disse are present in the liver of diabetic patients with microangiopathy, an ultrastructural stereologic study of the space of Disse was performed in six insulin-treated diabetics with severe performed in six insulin-treated diabetics with severe proliferative retinopathy and six insulin-treated diabetics with normal fluorescein angiography, six patients with familial unconjugated hyperbilirubinemia were studied as controls. No patient had clinical and/or biochemical hepatic abnormalities and none suffered from any of the pathologic conditions known to be associated with collagenization of the perisinusoidal space. In control patients, the space of Disse of liver sinusoids contained occasional small deposits of collagen fibers. The relative volume of these fibers per unit of sinusoid represented 2.63 +/- 0.82%. In all diabetic patients with retinopathy, marked deposition of collagen fibers within the perisinusoidal space was constantly observed, a finding confirmed by ultrastructural stereologic analysis which showed that the relative volume of collagen fibers per unit of sinusoid represented 7.33 +/- 1.44% and differed significantly from control patient values (P less than 0.001). On the contrary, the relative volume of collagen fibers within the space of Disse in diabetic patients without retinopathy (3.95 +/- 2.96%) did not differ significantly from control patient values. These findings demonstrate that collagenization of the space of Disse is positively correlated with the presence of diabetic microangiopathy. Ultrastructural examination of the liver sinusoids might constitute a sensitive and useful approach for detecting the early changes of the microcirculation in diabetic patients.

Ultrastructural lesions of bile ducts in primary biliary cirrhosis. A comparison with the lesions observed in graft versus host disease

Intrahepatic bile duct destruction is a characteristic feature of primary biliary cirrhosis and hepatic graft versus host disease. Lymphocytotoxicity against antigens on the surface of biliary cells is one of the cell mediated immune mechanisms debated in the pathogenesis of persistent bile duct destruction during primary biliary cirrhosis. Immune complex injury has also been hypothesized. In graft versus host disease, damage to bile duct cells is also believed to be due to a cytotoxic reaction of the grafted lymphoid cells against the host histocompatibility antigens, and immune complex deposition is likely to occur. The aim in this comparative ultrastructural study of intrahepatic bile ducts in 10 patients with primary biliary cirrhosis and six patients with hepatic graft versus host disease was to investigate whether identical or different ultrastructural lesions were detected in both diseases. Features of conspicuous necrosis of biliary cells, including cytolysosomes, apoptosis, and basement membrane disruption, were observed in both diseases. Numerous lymphocytes established close membrane contacts with biliary cells, especially with the necrotic ones. They had cytoplasmic pseudopods, and some of them displayed a uropod or contained lysosomal vesicles. Abnormalities of the bile duct basement membrane, also observed in both diseases, included thickening or multilayering and numerous lucent areas of rarefaction often containing osmiophilic inclusions. The striking similarity of the ultrastructural lesions in both diseases provides an additional morphological argument to suggest that certain common pathogenic mechanisms might be involved in the destruction of bile ducts in primary biliary cirrhosis as well as in hepatic graft versus host disease.

Hodgkin's disease: ultrastructural localization of intra-cytoplasmic immunoglobulins within malignant cells

An immunoperoxidase technique has been applied to the detection of intracellular immunoglobulins at the light and ultrastructural levels in three untreated cases of Hodgkin's disease. The results are compared with those obtained in three treated cases. In both groups, 20-90% of malignant cells had intra-cytoplasmic immunoglobulins. There was no correlation between the percentage of immunoglobulin-containing cells and the histological type or the stage of the disease. At the ultrastructural level, immunoglobulins were constantly localized on cytoplasmic ribosomes, the later being either free in the cytoplasm or bound to the endoplasmic reticulum and to the external envelope of the perinuclear space. In addition, a very few malignant cells exhibited immunoglobulins within their perinuclear space and their endoplasmic reticulum. These results demonstrate that immunoglobulins in Hodgkin's malignant cells are present on the cellular sites of protein synthesis. They appear to be retained in their cytoplasm, and to be secreted only very occasionally. The significance of these findings as to the cellular origin of malignant cells in Hodgkin's disease is briefly discussed.