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A Geerts

Publications and source records attributed to A Geerts.

At least 55 records · Page 3Linked to original sources
PubMed1995

Experimental biliary fibrosis correlates with increased numbers of fat-storing and Kupffer cells, and portal endotoxemia.

In the present study, we have investigated the correlation between hepatic fibrosis in rats subjected to bile duct ligation, the numbers of Kupffer and fat-storing cells, and the level of endotoxin in both the portal and systemic circulation. The extent of hepatic fibrosis was measured by morphometry. Kupffer cells were identified by indirect immunoperoxidase staining using ED-2 anti-macrophage antibody. Fat-storing cells were stained with DE-B-5 anti-desmin antibody. Endotoxin levels were determined by the Limulus Lysate test. Following bile duct ligation, connective tissue septa rapidly developed in periportal areas. After 1 week, the volume density of connective tissue had increased from 0.6 +/- 0.1% in control animals to 3.8 +/- 1.1%. After 2 weeks, this volume increased to 19.9 +/- 1.3%, and after 3 weeks to 34.3% +/- 2.7%. The number of periportal fat-storing cells increased 2.8-fold during the first 2 weeks, whereas pericentral fat-storing cells increased only 1.7-fold. After 2 weeks, no further increase was observed. During the first week of bile duct ligation, the number of Kupffer cells increased nearly two-fold. Thereafter, no further increase was detected. In control rats, only two of ten rats showed low amounts of endotoxin in the portal blood. Portal endotoxemia increased with time after bile duct ligation. After 3 weeks, all rats were positive. The measured endotoxin levels were approximately 7 times higher than in control rats. We conclude that the development of fibrosis secondary to experimental bile duct ligation is accompanied by protal endotoxemia, and increases in the numbers of Kupffer and periportal fat-storing cells. We found a significant correlation between portal endotoxemia, the number of Kupffer and fat-storing cells, and the extent of fibrous septa, supporting the view that high endotoxemia levels coincide with Kupffer cell activation and fibrogenesis.

Adipocytes↗
PubMed1995

Increased S-100 protein-immunoreactivity of Kupffer cells is associated with lymphohematological malignancy.

The distribution of S-100 protein in normal tissue has been studied extensively. However, little is known about its expression in pathologic states. The aim of the present study was to investigate the expression of S-100 protein in diseased human liver, especially in Kupffer cells. One hundred cases of autopsy livers originating from patients with various diseases were examined. Increased S-100-immunoreactivity of Kupffer cells was observed in six cases. Of the six cases, four were derived from a lymphohematologic malignancy, such as B cell lymphoma, B cell lymphoblastic leukemia, multiple myeloma and chronic myelogenous leukemia with lymphoblastic crisis. Lymphohematologic malignancy accounted for 16 out of the 100 cases examined. Thus, increased S-100-positive Kupffer cells was significantly associated with lymphohematologic malignancy (P < 0.01); 25% (4/16) in cases with lymphohematologic malignancy versus 2.4% (2/84) in the remaining cases. Moreover, some of these S-100-positive Kupffer cells were positive for S-100 beta-subunit, which is not normally expressed by Kupffer cells. Although the reason for this increased S-100-immunoreactivity is speculative, the authors' hypothesis is that tumor cells may produce some factor(s) that induce the expression of S-100 protein in Kupffer cells.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1994

Enhanced hepatic collagen type I mRNA expression into fat-storing cells in a rodent model of hemochromatosis.

In recent years, identifying the hepatic cell type responsible for collagen synthesis in experimental models of postnecrotic or inflammatory fibrosis has been the subject of active investigation. In primary iron overload states, however, hepatic fibrosis and cirrhosis occur without accompanying necroinflammatory phenomena. In this study, we combined morphological, immunological, cell isolation and purification and molecular biological techniques to identify the hepatic cell responsible for enhanced collagen type I gene expression during chronic enteral iron overload in the rat. Ultrastructural analysis of liver tissue sections from iron-loaded rats specifically revealed an altered appearance of fat-storing cells, which showed few if any fat droplets left and increased rough endoplasmic reticulum. In situ hybridization analysis with specific complementary RNA probes identified enhanced signal for collagen type I into nonparenchymal cells in zones 1 and 2, without signal over the background onto iron-laden hepatocytes. Immunocytochemistry with desmin antibodies combined with in situ hybridization on the same tissue sections identified the cells expressing high level of collagen type I transcripts as fat-storing cells. Northern-blot analysis on RNA extracted from various purified cell isolates, confirmed the presence of collagen type I mRNA signal only into the fat-storing cells isolate. Our study shows that in an experimental model of metabolic fibrosis in which the hepatotoxin selectively accumulates into parenchymal cells, fat-storing cells are the main source of enhanced collagen type I gene expression.

Animals↗
PubMed1994

Monocyte chemoattractant protein 1 (MCP-1) expression occurs in toxic rat liver injury and human liver disease.

Considerable evidence suggests that monocytes/macrophages play a crucial role in the process of liver injury and repair. Recent investigations have focused on the function of various macrophage-produced cytokines in liver disease. Much is still unknown, however, about the mechanism of macrophage recruitment and activation during liver disease. To further define this process, the gene expression of the monocyte chemoattractant monocyte chemoattractant protein 1 (MCP-1) was examined in animal and human liver disease. MCP-1 mRNA was not found in normal rat liver by Northern blot analysis. After single-dose treatments with the hepatotoxins carbon tetrachloride and galactosamine, MCP-1 mRNA was detectable beginning at 2 and 4 h after treatment, respectively, and was expressed continuously until 60-72 h. During chronic carbon tetrachloride administration, MCP-1 mRNA levels were elevated for the entire 10 weeks of treatment with peak levels of expression occurring early (weeks 1-3) and late (weeks 8-10) in this model. Isolated liver cell fractions from rats treated for 3 weeks with carbon tetrachloride revealed the major cellular source of MCP-1 mRNA to be fat-storing or Ito cells, with some expression occurring in the endothelial cell fraction. Studies of potential inducers of hepatic MCP-1 expression showed that lipopolysaccharide, tumor necrosis factor-alpha, and interleukin-1 alpha and beta treatments all led to MCP-1 expression. Finally, studies of human liver samples revealed MCP-1 gene expression in nondiseased liver and greatly increased levels in livers from patients with fulminant hepatic failure. These data implicate MCP-1 from fat-storing cells as a modulator of the process of liver injury and further support a role for MCP-1 in the pathogenesis of human disease.

Animals↗
PubMed1994

Expression of lipoxygenase in wounded tubers of Solanum tuberosum L.

A lipoxygenase cDNA clone from Solanum tuberosum L. was analyzed to study the role of lipoxygenases in potato development and wound response. Sequence analysis and comparison of the deduced amino acid sequence revealed high homology to other plant lipoxygenases. Expression of the cDNA sequences in Escherichia coli and subsequent analysis of bacterial protein extracts showed lipoxygenase activity using linoleic, linolenic, or arachidonic acid as substrates. Transcripts encoding the potato lipoxygenase were most abundant in tuber tissue, lower in roots, and hardly detectable in leaves, petioles, and stems. The induction of lipoxygenase expression in tubers by wounding was dependent on various parameters. Whereas lipoxygenase transcript levels increased in discs from stored tubers incubated under aerobic conditions, tubers taken from a growing plant did not accumulate lipoxygenase transcripts in response to wounding. Incubation of tuber discs in buffer did not lead to an increase in lipoxygenase RNA levels; however, methyl jasmonate stimulated lipoxygenase expression after 24 h in stored tubers. Proteinase inhibitor II mRNAs decreased in stored tubers as well as in discs from growing tubers.

Amino Acid Sequence↗
PubMed1993

Rat liver fat-storing cell lines express sarcomeric myosin heavy chain mRNA and protein.

Fat-storing cells (FSC, lipocytes, or Ito cells) of liver store vitamin A and are the main producers of extracellular matrix in normal and cirrhotic liver. During liver injury, FSC undergo an activation process characterized by a decrease in vitamin A storage and an increase in cell proliferation and extracellular matrix deposition. This activation process also occurs upon culturing FSC from normal liver. In contrast to most cells of nonmuscle origin, activated FSC express two cytoskeletal proteins normally found in muscle, desmin, and smooth muscle alpha-actin. Based on their strategic perisinusoidal location, it has been hypothesized that FSC play a role in regulating blood flow. However, the nature of the contractile elements involved in this process remains to be determined. In this communication we demonstrate the presence of a sarcomeric myosin in proteins solubilized from liver biomatrix. In addition we demonstrate the expression of sarcomeric myosin heavy chain (MHC) mRNA and protein in two FSC clones derived from a CCl4-cirrhotic rat liver (CFSC). Through cloning the cDNA corresponding to the MHC gene expressed in these cells we demonstrate that it encodes fast IId skeletal MHC and thus represents a marker normally seen in adult muscle. The unexpected expression of an adult stage skeletal muscle molecular motor in FSC from cirrhotic liver is consistent with the proposed specialized contractile capacity of these cells.

Adipocytes↗
PubMed1993

Identification of connective tissue gene transcripts in freshly isolated parenchymal, endothelial, Kupffer and fat-storing cells by northern hybridization analysis.

The aim of the present study was to identify the cell types that express collagen alpha 1(I), alpha 1(III) and alpha 1(IV), fibronectin and laminin B1 genes in normal rat liver. Parenchymal, sinusoidal endothelial, Kupffer and fat-storing (Ito) cells were isolated and purified. Total RNA of the freshly isolated cells was subjected to Northern hybridization analysis. We also compared the steady state levels of specific mRNAs in freshly isolated fat-storing cells to the levels in myofibroblast-like cells obtained from purified fat-storing cells cultured for two passages. The average purity of each cell preparation, and the percentage of contaminating cells, were determined by transmission electron microscopy and by examining the presence of vitamin A-autofluorescent cells. Fibronectin and collagen alpha 1(III) mRNAs were detected in total RNA of purified parenchymal cells. In poly(A)+ enriched RNA, small amounts of collagen alpha 1(I) mRNA were also present. In total RNA of freshly isolated fat-storing cells, collagen alpha 1(III), alpha 1(IV), and laminin B1 transcripts were found, whereas collagen alpha 1(I) and fibronectin mRNAs were not detected. Cultured fat-storing cells, however, did contain high levels of collagen alpha 1(I) and fibronectin mRNAs. The molecular size of the latter transcript was larger than the fibronectin transcript found in parenchymal cells and the whole liver. Endothelial cells contained small amounts of alpha 1(IV) mRNA. Kupffer cells did not contain the investigated transcripts. We conclude that normal parenchymal, fat-storing and endothelial cells each express a typical pattern of connective tissue molecules. When fat-storing cells are allowed to differentiate into myofibroblast-like cells, they express high levels of collagen alpha 1(I) and fibronectin mRNAs, in addition to collagen alpha 1(III) and alpha 1(IV), and laminin B1 chain mRNAs.

Adipocytes↗
PubMed1993

Identification and localization of 23,000 and glycosylated rat prolactin in subcellular fractions of rat anterior pituitary and purified secretory granules.

Rat pituitary homogenates were submitted to differential and density gradient centrifugation. Subcellular fractions as well as the purified secretory granules were examined in electron microscopy, radioimmunological techniques, protease digestion, alkaline treatment and immunoblotting. The global outcome of these experiments was that: 1) the glycosylated rPRL was foremost recorded in the crude secretory granular fraction, also in the microsomal fraction and the cytosol, but virtually not in the plasma membrane fraction; 2) in purified secretory granules glycosylated rPRL appeared as an array of near Mr, such as was formerly obtained by enzymatic deglycosylation; 3) protease digestion and ice-cold alkaline treatment of the secretory granules showed that 23,000 rPRL appears in three different physicochemical states in these organelles: unsequestered within a closed system, membrane-bounded and bound state; 4) likewise treatment of microsomal vesicles showed that 23,000 and glycosylated rPRL are sequestered in these bodies, but apparently 23,000 rPRL appears as both integral membrane-bound and released from the lumen, whereas glycosylated rPRL is chiefly retained as an integral membrane protein. 5) dopamine alters the pattern of glycosylation as well in Mr as in relative percentages of the molecular variants. The systematical occurrence of the array of near Mr glycosylated rPRL is biosynthesized as a pool of proteins with a different degree of glycosylation. On the basis of our data, we speculate that selection of definite molecular variants from this pool could play an important role in the biological function of 23,000 rPRL and that oligosaccharides could perhaps target the glycosylated forms of rPRL to specific sites of action.

Animals↗
PubMed1993

The role of Ito cells in the biosynthesis of HGF-SF in the liver.

Hepatocyte Growth Factor-Scatter Factor (HGF-SF) is produced by sinusoidal cells in normal rat liver. Analysis of isolated cells has proven that Ito cells (fat-storing cells, hepatic lipocytes) are the source of hepatic HGF. In diseased liver the HGF-expression pattern is more complex. In acute liver injury HGF is expressed by an increased number of resident liver cells, which may be due to recruitment of other nonparenchymal liver cells as well as an increased number of Ito cells due to cell division. In cirrhotic rat liver tissue, the number of HGF-expressing cells is decreased. This may be explained by the complete loss of HGF-expression in myofibroblast-like cells derived from Ito cells. Quiescent Ito cells seem to be in a strategic position to control parenchymal cell proliferation. Activation of Ito cells, which occurs in chronic fibrotic liver disease, may lead to the loss of this control function.

Acute Disease↗
PubMed1992

Hepatocyte growth factor/hepatopoietin A is expressed in fat-storing cells from rat liver but not myofibroblast-like cells derived from fat-storing cells.

Hepatocyte growth factor/hepatopoietin A is a complete mitogen for parenchymal liver cells, and its expression is increased as an early response to acute liver injury. To identify the liver cell population responsible for hepatocyte growth factor gene expression, we investigated tissue sections and isolated and purified cell fractions from normal rat liver by in situ and Northern blot hybridization. Hepatocyte growth factor transcripts were present in sinusoidal liver cells, which were preferentially located in the periportal parenchyma. Northern hybridization analysis of RNA isolated from purified liver cell fractions demonstrated that HGF messenger RNA is present only in fat-storing cells. No specific hepatocyte growth factor gene expression was detected in parenchymal cells, endothelial cells and Kupffer cells. Myofibroblast-like transition of fat-storing cells, which is linked to fibrogenesis in chronic liver disease, results in the loss of hepatocyte growth factor expression. Hepatocyte growth factor gene expression in the normal liver, a new function of fat-storing cells, suggests that this growth factor may play a role in the physiological balance between cell death and replacement in the liver and that hepatocyte growth factor may also act in a paracrine manner. Furthermore, loss of hepatocyte growth factor expression in myofibroblast-like cells derived from fat-storing cells may be responsible for reduced parenchymal cell regeneration in chronic liver disease.

Animals↗
PubMed1992

Ito cell expression of a nuclear retinoic acid receptor.

Although it has been suggested that retinoids regulate Ito cell proliferation and collagen synthesis, little is known about the ability of Ito cells to respond to retinoids in vivo. Because retinoids may mediate their molecular effects through nuclear receptors, Ito cells were examined for the presence of one of these receptors, nuclear retinoic acid receptor-beta. The modulation of nuclear retinoic acid receptor-beta expression was also studied during cell culture and hepatic fibrogenesis. Northern hybridization analysis revealed that Ito cells freshly isolated from normal rat liver contained nuclear retinoic acid receptor-beta messenger RNA at levels significantly higher than those found in other hepatic cell types. Ito cells also contained messenger RNA for two other nuclear retinoic acid receptors, nuclear retinoic acid receptor-alpha and nuclear retinoic acid receptor-gamma. Using an antibody to human nuclear retinoic acid receptor-beta, the nuclear presence of this receptor was demonstrated in normal Ito cells. In contrast, Ito cells cultured for at least 7 days had no detectable messenger RNA or nuclear staining for nuclear retinoic acid receptor-beta despite a 20 +/- 5-fold increase in the messenger RNA level of another retinoid binding protein, cellular retinol binding protein. Analysis of Ito cells isolated from rats with carbon tetrachloride-induced hepatic fibrosis revealed an 81% +/- 3% decrease in nuclear retinoic acid receptor-beta messenger RNA levels in these cells when compared with normal Ito cells. No difference in the messenger RNA levels of cellular retinol binding protein was found in Ito cells isolated from either normal or fibrotic liver.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Localization and cellular source of the extracellular matrix protein tenascin in normal and fibrotic rat liver.

The distribution and the cellular source of the novel extracellular matrix glycoprotein tenascin were studied in normal and fibrotic rat liver. Cryostat sections of normal rat livers, livers of rats treated with intraperitoneal injections of CCl4 and 4-day-old and 8-day-old primary fat-storing cell cultures were stained for tenascin and desmin using an immunoperoxidase procedure or a double-label immunofluorescence technique. Fat-storing cell cultures were metabolically labeled with 3H-proline. Radiolabeled proteins were immunoprecipitated from the supernatant with antitenascin antiserum and subjected to polyacrylamide gel electrophoresis. In normal rat livers, tenascin was detected discontinuously along the sinusoids, whereas portal tracts were devoid of staining. In fibrotic rat livers, tenascin was preferentially expressed in areas of cell damage, in slender septa or at connective tissue-parenchymal interfaces. The middle region of broad septa was negative. Desmin-positive fat-storing cells accumulated in areas strongly immunoreactive for tenascin, and double-label immunofluorescence showed cells positive for both tenascin and desmin. In fat-storing cell cultures, both intracellular positivity for tenascin and staining of extracellular fibers were seen. Gel electrophoresis of immunoprecipitated proteins revealed two major and three minor bands with molecular weights consistent with tenascin. We conclude that tenascin is a component of the extracellular matrix of both normal and fibrotic rat livers. The strong expression of tenascin in areas of cell damage, in "early" septa or at septal-parenchymal interfaces, in contrast to its absence from the middle region of mature septa, suggests a role in early matrix organization. Fat-storing cells synthesize and secrete tenascin.

Animals↗
PubMed1992

Internalization of intact poliovirus by HeLa cells as shown by subcellular fractionation in isoosmotic Nycodenz gradients.

HeLa cells were infected with radiolabelled poliovirus at different temperatures, and the intracellular distribution of input radioactivity was studied. To this end, homogenates were fractionated by rate zonal centrifugation in linear isoosmotic (2 to 30%) Nycodenz gradients. Further purification of subcellular fractions was achieved by recentrifugation to equilibrium in 10 to 30% Nycodenz. Temperatures were kept below 30 degrees C to prevent virus capsid modification. Under these conditions, the cell-associated virions remained fully infectious. Below 18 degrees C, most of the viral label was recovered from a bottom region (BR) of the rate zonal gradients. Marker enzyme analysis and antibody accessibility showed that the BR consisted of virions bound to the plasma membrane. Between 18 degrees C and 26 degrees C, viral label also accumulated in a top region (TR) of the rate zonal gradients. According to the criterion of antibody accessibility, the virions associated with the TR were present within intracellular structures, probably lipid membranes. Electron microscopy confirmed the presence of vesicles and tubules in this region of the gradient. No correlation was found between the TR and endosomal, lysosomal or plasma membrane markers. The TR equilibrated at low density (1.10 g/ml) in Nycodenz (free virus, 1.31 g/ml). The results confirm that intact poliovirions can enter the cell and do so via lipid-bound vesicles.

Biomarkers↗
PubMed1992

Tenascin expression in human chronic liver disease and in hepatocellular carcinoma.

Tenascin is an oligomeric glycoprotein of the extracellular matrix synthesized during embryonic development. It is prominently expressed in a variety of tumors. The role of tenascin in liver tissue is, however, unknown. We used immunocytochemistry to define the localization of tenascin and compare this with the localization of non-collagenous proteins, such as laminin and fibronectin, in normal human liver and pathological liver from patients with chronic hepatitis, liver cirrhosis and hepatocellular carcinoma. In normal liver, tenascin expression was localized along the sinusoidal and vascular wall. In fibrotic liver, tenascin was also observed in the region between the hepatic parenchyma and the fibrosing portal tracts, especially in areas of piecemeal necrosis in chronic hepatitis. Immuno-EM study of liver tissue in chronic hepatitis strongly suggested the synthesis and secretion of tenascin by fat-storing cells into the space of Disse. In hepatocellular carcinoma, tenascin was expressed in both the capsule and lobular septa, but not in the sinusoidal walls of the tumors. These results led us to postulate a close relationship between the occurrence of this protein and disease processes such as fibrosis and cancer invasion.

Carcinoma, Hepatocellular↗
PubMed1991

Role of fat-storing cells in hepatic fibrogenesis. Retinoids as possible therapeutic agents.

In normal liver, fat-storing cells are the main storage site of vitamin A derivatives, mainly of retinyl palmitate and oleate. During liver injury, the phenotype of fat-storing cells alters dramatically. The cells gradually lose their fat-droplets, proliferate and synthesize large amounts of connective tissue molecules. In the present paper, we summarize the characteristics of fat-storing cells, review the role of fat-storing cells in development of hepatic fibrosis, and describe how retinoids affect the protein synthesis and proliferation of these cells.

Animals↗
PubMed1991

Tissue distribution, quantitation and proliferation kinetics of fat-storing cells in carbon tetrachloride-injured rat liver.

In this study, we have investigated the cell population kinetics of fat-storing cells in livers of rats intoxicated with CCl4. Fat-storing cells were identified in cryostat sections by immunoperoxidase staining of desmin. The peroxidase label was visualized using diaminobenzidine/hydrogen peroxide containing Ni2+ and Co(2+)-ions (Nico/diaminobenzidine method). In normal rats, we found 12.8 fat-storing cells/0.1 mm2 in periportal areas vs. 9.4 in pericentral fields. After one injection of CCl4, the number of pericentral cells increased gradually to reach a maximum of 39.4 cells/0.1 mm2 96 hr after injection. The desmin staining intensity of the pericentral fat-storing cells increased from 48 hr onward. At 72 to 120 hr, strongly stained cells were observed in pericentral areas and in bands of tissue between adjacent central veins, reminiscent of the connective tissue septa in fibrotic livers. In the periportal areas the number of fat-storing cells was not altered. After a second and third injection of CCl4, the number of cells increased further in the pericentral areas. When more than three injections were given, the pericentral fat-storing cell population reached a new steady state with the cell number being seven times higher than in control animals. Proliferation of fat-storing cells at different stages of CCl4 intoxication was studied by intravenous administration of 3H-thymidine, followed by combined desmin staining and autoradiography. Autoradiographical labeling of fat-storing cells was nearly absent in control animals and at 24 hr after a single CCl4 injection. At 48 to 96 hr, labeling indices of pericentral fat-storing cells were significantly higher than in control animals, with a maximum at 72 hr when 22.9% of the cells were labeled. After multiple injections of CCl4, labeling indices between 4.9% and 8.4% were found. We conclude that fibrogenesis is preceded by a strong expansion of the fat-storing cell population in the pericentral areas of the liver lobules and in bands of tissue between adjacent central veins. Local proliferation is an important mechanism underlying the expansion of this cell population.

Animals↗
PubMed1990

Collagen type I and III occur together in hybrid fibrils in the space of Disse of normal rat liver.

Collagen type I and procollagen type III were localized at the ultrastructural level on ultrathin frozen sections of rat liver by the protein A-gold technique using affinity-purified primary antibodies. Both collagen type I and procollagen type III were localized on nearly all solitary and bundled fibrils in the space of Disse. Simultaneous localization of collagen type I and procollagen type III by a double-labeling procedure using protein A-gold probes of different sizes unequivocally demonstrated the presence of both collagens in the same fibrils. Measurement of the diameter of large numbers of collagen fibrils in the space of Disse of the rat liver showed a unimodal distribution of the fibril diameters around an average value of 62.4 nm (S.D. = 12.8 nm), and 91% of the collagen bundles contained less than 30 fibrils. Additional measurements on epoxy resin-embedded material of five biopsy specimens of normal human liver showed a comparable unimodal distribution of the fibril diameters around an average value of 57.2 nm (S.D. = 9.6 nm), and 74% of the bundles contained less than 60 fibrils. The latter observation demonstrates that human liver contains broader interstitial collagen bundles than rat liver. From these results, we conclude that the space of Disse of normal rat and human liver contains a uniform population of striated interstitial collagen fibrils. In the rat liver, these fibrils contain both collagen type I and procollagen type III. Therefore the concept that procollagen type III is predominantly localized in small diameter fibrils or bundles, whereas collagen type I is preferentially localized in thick ones, does not hold.

Animals↗