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Biomedical subjects

J Kuiper

Publications and source records attributed to J Kuiper.

At least 73 records · Page 4Linked to original sources
PubMed1992

Characterization of the interaction both in vitro and in vivo of tissue-type plasminogen activator (t-PA) with rat liver cells. Effects of monoclonal antibodies to t-PA.

The interaction of 125I-labelled tissue-type plasminogen activator (125I-t-PA) with freshly isolated rat parenchymal and endothelial liver cells was studied. Binding experiments at 4 degrees C with parenchymal cells and endothelial liver cells indicated the presence of 68,000 and 44,000 high-affinity t-PA-binding sites, with an apparent Kd of 3.5 and 4 nM respectively. Association of 125I-t-PA with parenchymal cells was Ca(2+)-dependent and was not influenced by asialofetuin, a known ligand for the galactose receptor. Association of 125I-t-PA with liver endothelial cells was Ca(2+)-dependent and mannose-specific, since ovalbumin (a mannose-terminated glycoprotein) inhibited the cell association of t-PA. Association of 125I-t-PA with liver endothelial cells was inhibited by anti-(human mannose receptor) antiserum. Anti-(galactose receptor) IgG had no effect on 125I-t-PA association with either cell type. Degradation of 125I-t-PA at 37 degrees C by both cell types was inhibited by chloroquine or NH4Cl, indicating that t-PA is degraded lysosomally. in vitro experiments with three monoclonal antibodies (MAbs) demonstrated that anti-t-PA MAb 1-3-1 specifically decreased association of 125I-t-PA with the endothelial cells, and anti-t-PA Mab 7-8-4 inhibited association with the parenchymal cells. Results of competition experiments in rats in vivo with these antibodies were in agreement with findings in vitro. Both antibodies decreased the liver uptake of 125I-t-PA, while a combination of the two antibodies was even more effective in reducing the liver association of 125I-t-PA and increasing its plasma half-life. We conclude from these data that clearance of t-PA by the liver is regulated by at least two pathways, one on parenchymal cells (not galactose/mannose-mediated) and another on liver endothelial cells (mediated by a mannose receptor). Results with the MAbs imply that two distinct sites on the t-PA molecule are involved in binding to parenchymal cells and liver endothelial cells.

Animals↗
PubMed1992

Characterization of the low-density-lipoprotein-receptor-independent interaction of beta-very-low-density lipoprotein with rat and human parenchymal liver cells in vitro.

beta-Migrating very-low-density lipoprotein (beta-VLDL) is a cholesteryl-ester-enriched lipoprotein which under normal conditions is rapidly cleared by parenchymal liver cells. In this study the characteristics of the interaction of beta-VLDL with rat parenchymal cells, Hep G2 cells and human parenchymal cells are evaluated. The binding of beta-VLDL to these cells follows saturation kinetics (Bmax. respectively 117, 106 and 103 ng of beta-VLDL apoliprotein/mg of cell protein), with a relatively high affinity (Kd respectively for beta-VLDL of 10.7, 5.1 and 8.4 micrograms/ml). Competition studies of unlabelled beta-VLDL, low-density lipoprotein (LDL) or acetylated LDL with the binding of radiolabelled beta-VLDL indicate that a LDL-receptor-independent, Ca(2+)-independent, specific recognition site for beta-VLDL is present on rat and human parenchymal cells, whereas with Hep G2 cells or mouse macrophages beta-VLDL recognition is performed by the LDL receptor. The binding of beta-VLDL to Hep G2 cells was down-regulated by 89% by prolonged exposure to beta-VLDL, whereas for human parenchymal and rat parenchymal cells down-regulation of 44% and 20% respectively was observed. Studies with antibodies against the LDL receptor support the presence of a LDL-receptor-independent specific beta-VLDL recognition site on rat and human parenchymal cells. It is concluded that a LDL-receptor-independent recognition site for beta-VLDL is present on rat and human parenchymal liver cells. The presence of a LDL-receptor-independent recognition site on human parenchymal cells may mediate in vivo the uptake of beta-VLDL during consumption of a cholesterol-rich diet, when LDL receptors are down-regulated, thus protecting against the extrahepatic accumulation of the atherogenic beta-VLDL constituents.

Animals↗
PubMed1992

In vivo and in vitro interaction of high and low molecular weight single-chain urokinase-type plasminogen activator with rat liver cells.

The plasma clearance and the interaction of high (HMW) and low (LMW) molecular weight single-chain urokinase-type plasminogen activator (scu-PA) with rat liver cells was determined. 125I-Labeled HMW- and LMW-scu-PA were rapidly cleared from plasma with a half-life of 0.45 min and a maximal liver uptake of 55% of the injected dose. Liver uptake of scu-PA was mediated by parenchymal cells. Excess of unlabeled HMW-scu-PA reduced the liver uptake of 125I-HMW-scu-PA strongly. In vivo liver degradation of scu-PA was reduced by inhibitors of the lysosomal pathway. A high affinity binding site (Kd 45 nM, Bmax 1.7 pmol/mg cell protein) for both HMW- and LMW-scu-PA was determined on isolated parenchymal liver cells. Cross-competition binding studies showed that LMW- and HMW-scu-PA bind to the same site. Tissue-type plasminogen activator, mannose- or galactose-terminated glycoproteins did not affect the scu-PA binding to parenchymal liver cells. It is concluded that LMW- and HMW-scu-PA are taken up in the liver by a common, newly identified recognition site on parenchymal liver cells and are subsequently degraded in the lysosomes. It is suggested that this site is important for the regulation of the turnover of scu-PA.

Animals↗
PubMed1992

Isolation and characterization of the mannose receptor from human liver potentially involved in the plasma clearance of tissue-type plasminogen activator.

Various studies have shown that mannose receptors rapidly eliminate glycoproteins and microorganisms bearing high mannose-type carbohydrate chains from the blood circulation. The purpose of this study was to characterize the mannose receptor in the liver, which in vivo is involved in the rapid clearance of tissue-type plasminogen activator from the circulation. Human liver membranes were solubilized in Triton X-100, and the solution was applied to a tissue-type plasminogen activator Sepharose column. Bound proteins were eluted with ethylenediaminetetraacetate (10 mmol/L). A second, similar purification step rendered a single liver protein of 175,000 daltons. A combination of ligand blotting and a chromogenic assay for tissue-type plasminogen activator demonstrated that the identified liver protein is a mannose receptor because it bound tissue-type plasminogen activator, this tissue-type plasminogen activator binding being fully inhibited by 0.2 mol/L D-mannose. Western-blot analysis revealed that the isolated liver protein is immunologically identical to the human mannose receptor from placenta. Treatment of the liver protein and the placenta mannose receptor with trypsin yielded the same pattern of proteolytic degradation products as identified on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We conclude that the physiologically relevant mannose receptor for tissue-type plasminogen activator clearance isolated from human liver is immunologically and structurally similar to or identical with the human mannose receptor isolated from placenta.

Blotting, Western↗
PubMed1992

Characterization of the interaction of acetylated LDL and oxidatively modified LDL with human liver parenchymal and Kupffer cells in culture.

The interaction of acetylated low density lipoprotein (Ac-LDL) and oxidatively modified low density lipoprotein (Ox-LDL) with cultured human liver parenchymal cells and human Kupffer cells was investigated to define, for humans, the presence of scavenger receptors in the liver. A direct comparison of the capacity of Kupffer and parenchymal cells to interact with Ac-LDL and Ox-LDL indicated that the capacity of Kupffer cells per milligram of cell protein to degrade Ac-LDL and Ox-LDL is 14-fold and sixfold higher, respectively, than that of parenchymal cells. The degradation of both Ac-LDL and Ox-LDL by parenchymal cells and Kupffer cells could be inhibited by chloroquine and ammonium chloride, indicating that degradation occurs in the lysosomes. Competition studies showed that unlabeled Ox-LDL competed efficiently with the cell association and degradation of 125I-labeled Ac-LDL by human parenchymal cells and human Kupffer cells. However, unlabeled Ac-LDL did not compete (parenchymal cells) or only partially competed (40% in Kupffer cells) with the cell association and degradation of 125I-labeled Ox-LDL. Polyinosinic acid completely blocked the cell association and degradation of Ac-LDL and Ox-LDL with Kupffer cells while no significant effect on parenchymal cells was noted. It is concluded that human liver parenchymal cells contain a scavenger receptor that interacts with Ac-LDL and Ox-LDL and an additional recognition site that recognizes Ox-LDL specifically.(ABSTRACT TRUNCATED AT 250 WORDS)

Binding Sites↗
PubMed1992

IgG subclass response to Helicobacter pylori in patients with chronic active gastritis and duodenal ulcer.

The IgG subclass response is determined by the type of bacteria producing the infection and by genetic factors of the host. Patients with a Helicobacter pylori infection develop a specific immune response that is mainly of the IgA and IgG class. We measured the IgG subclass response in 20 patients with chronic active gastritis without a history of duodenal ulcer and 20 patients with chronic active gastritis and duodenal ulcer diagnosed by endoscopy and histology. A control group included 20 H. pylori-negative patients and 60 H. pylori-positive blood transfusion donors. Systemic IgG subclass response was measured with a modified enzyme-linked immunosorbent assay technique, using as antigen a sonicate of six different H. pylori strains. Mouse monoclonal antibodies against each of the four human IgG subclasses (IgG1, IgG2, IgG3, and IgG4) were used. The total IgG anti-H. pylori antibody titres were equal in all three H. pylori-positive groups and significantly different from that of the negative control group (p less than 0.01). The IgG subclass response in persons infected with H. pylori involved all four subclasses but was predominantly of the IgG1 and IgG2 subclasses. All of the groups with H. pylori infection had significantly higher levels of IgG1 than the negative control group, but no differences were detected among the three groups. However, the duodenal ulcer group had a significantly higher IgG2 response than the gastritis group (mean optical density +/- SEM, 0.382 +/- 0.047 versus 0.200 +/- 0.025, respectively; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Complete down-regulation of low-density lipoprotein receptor activity in human liver parenchymal cells by beta-very-low-density lipoprotein.

The effect of LDL and beta-VLDL on the expression of the LDL receptor is studied in cultured human parenchymal cells. The high affinity binding of [125I]LDL to cultured human parenchymal cells was down regulated to 37.3 +/- 2.9% and 24.0 +/- 2.6% of the control value, after preincubation with LDL or beta-VLDL for 22 h, respectively. When LDL receptor synthesis was blocked at 22 h a residual receptor activity of 29% is noticed, indicating a half-life of LDL receptors in human parenchymal cells of 12 h. It is concluded that LDL receptor expression on human liver parenchymal cells is subject to complete down-regulation by beta-VLDL, which may be held responsible for the cholesterol-rich diet induced down-regulation of LDL receptors, in vivo.

Binding, Competitive↗
PubMed1991

Uptake and degradation of human low-density lipoprotein by human liver parenchymal and Kupffer cells in culture.

The association with and degradation by cultured human parenchymal liver cells and human Kupffer cells of human low-density lipoprotein (LDL) was investigated in order to define, for the human situation, the relative abilities of the various liver cell types to interact with LDL. With both human parenchymal liver cells and Kupffer cells the association of LDL with the cells followed saturation kinetics which were coupled to LDL degradation. The association of LDL (per mg of cell protein) to both cell types was comparable, but the association with human Kupffer cells was much more efficiently coupled to degradation than was the case in parenchymal cells. The capacity of human Kupffer cells to degrade LDL was consequently 18-fold higher (per mg of cell protein) than that of the human parenchymal liver cells. Competition studies showed that unlabelled LDL competed efficiently with the cell association and degradation of 125I-labelled LDL with both parenchymal and Kupffer cells, while unlabelled acetyl-LDL was ineffective. The degradation of LDL by parenchymal and Kupffer cells was blocked by chloroquine and NH4Cl, indicating that it occurs in the lysosomes. Binding and degradation of LDL by human liver parenchymal cells and human Kupffer cells appeared to be completely calcium-dependent. It is concluded that the association and degradation of LDL by human Kupffer and parenchymal liver cells proceeds through the specific LDL receptor, whereas the association of LDL to Kupffer cells is more efficiently coupled to degradation. The presence of the highly active LDL receptor on human Kupffer cells might contribute significantly to LDL catabolism by human liver, especially under conditions whereby the LDL receptor on parenchymal cells is down-regulated.

Ammonium Chloride↗
PubMed1991

Normative sexual behavior in children.

A large-scale, community-based survey was done to assess the frequency of a wide variety of sexual behaviors in normal preadolescent children and to measure the relationship of these behaviors to age, gender, and socioeconomic and family variables. A sample of 880 2- through 12-year-old children screened to exclude those with a history of sexual abuse were rated by their mothers using several questionnaire measures. The frequency of different behaviors varied widely, with more aggressive sexual behaviors and behaviors imitative of adults being rare. Older children (both boys and girls) were less sexual than younger children. Sexuality was found to be related to the level of general behavior problems, as measured by the Achenbach Internalizing and Externalizing T scores and to a measure of family nudity. It was not related to socioeconomic variables.

Age Factors↗
PubMed1990

Endotoxin induction of plasminogen activator and plasminogen activator inhibitor type 1 mRNA in rat tissues in vivo.

The tissue-specific distribution of tissue-type and urokinase-type plasminogen activator (t-PA and u-PA) and their inhibitor type 1 (PAI-1) was analyzed at mRNA level in five major rat organ tissues. t-PA mRNA was detected in lung, kidney, heart, and liver. u-PA mRNA was detected in kidney and lung. Presence of PA mRNA correlated with the detection of PA activity in extracts of these tissues. PAI-1 mRNA was detected predominantly in heart and lung. Although PAI activity could not be measured directly in tissue extracts, the presence of PAI-1 mRNA correlated with the occurrence of PA.PAI complex in fibrin autography of tissue extracts. Endotoxin injection caused a very large increase in plasma PAI activity. This increase correlated with a marked increase in PAI-1 mRNA in nearly all tissues studied. The increase in PAI-1 mRNA is most pronounced in lung and liver. Endotoxin injection also caused an increased level of t-PA mRNA in heart and kidney, and an increased u-PA mRNA level in kidney. mRNA analysis of freshly isolated and separated subfractionated liver cells showed that the marked increase in PAI-1 mRNA in the liver after endotoxin injection may be due mainly to a strong increase of PAI-1 mRNA in the liver endothelial cells.

Animals↗
PubMed1990

Receptor-mediated endocytosis of tissue-type plasminogen activator (t-PA) by liver cells.

Tissue-type plasminogen activator (t-PA) has a short half-life in the circulation because the enzyme is rapidly cleared by the liver. This short review summarizes recent literature concerning mechanisms of uptake and degradation of t-PA in the liver. In vivo studies in rats show that degradation takes place via a lysosomal pathway. Saturation of the uptake system at high t-PA concentrations suggests a receptor-mediated mechanism. Competition experiments with various glycoproteins indicate that the asialoglycoprotein receptor is not involved, but they point to a role for the mannose receptor, which recognizes t-PA via its high mannose-type oligosaccharide on the first kringle domain. Both in vivo and in vitro studies with isolated liver cells demonstrate that parenchymal cells, as well as liver endothelial cells, are involved in the clearance of t-PA. Parenchymal cells, as the hepatoma cell line Hep G2, endocytose t-PA via a still unknown, possibly t-PA specific receptor, while liver endothelial cells catabolize t-PA via the mannose receptor.

Amino Acid Sequence↗
PubMed1989

Cellular communication inside the liver. Binding, conversion and metabolic effect of prostaglandin D2 on parenchymal liver cells.

The major eicosanoid produced within the rat liver, prostaglandin (PG) D2, wa studied for its ability to interact with the various liver cell types. It appeared that PGD2 bound specifically to parenchymal liver cells, whereas the binding of PGD2 to Kupffer and endothelial liver cells was quantitatively unimportant. Maximally 700 pg of PGD2/mg of parenchymal-cell protein could be bound by a high-affinity site (1 x 10(6) PGD2-binding sites/cell). The recognition site for PGD2 is probably a protein because trypsin treatment of the cells virtually abolished the high-affinity binding. High-affinity binding of PGD2 was a prerequisite for the induction of a metabolic effect in isolated parenchymal liver cells, i.e. the induction of glycogenolysis. High-affinity binding of PGD2 by parenchymal cells was coupled to the conversion of PGD2 into three metabolites, whereas no conversion of PGD2 by Kupffer and endothelial liver cells was noticed. The temperature-sensitivity of the conversion of PGD2 was consistent with a conversion of PGD2 on or in the vicinity of the cell membrane. One of the PGD2 metabolites could be identified as 9 alpha, 11 beta-PGF2. It can be calculated that the conversion rate of PGD2 by parenchymal liver cells exceeds the production rate of PGD2 by Kupffer plus endothelial liver cells, indicating that PGD2 is meant to exert its activity within the liver. The present finding that PGD2 formed by the non-parenchymal liver cells is recognized by a specific receptor on parenchymal liver cells and that binding, conversion and metabolic effect of PGD2 are interlinked by this receptor provides further support for the specific role of PGD2 in the intercellular communication in the liver.

Alprostadil↗
PubMed1989

Induction of ornithine decarboxylase in rat liver by phorbol ester is mediated by prostanoids from Kupffer cells.

Administration of phorbol 12-myristate 13-acetate (PMA) to rats in vivo resulted in the induction of ornithine decarboxylase activity in the liver which could be blocked by preinjection of indomethacin, a cyclooxygenase inhibitor. In vitro administration of PMA to primary cultures of rat parenchymal cells did not lead to an induction of ornithine decarboxylase activity. It was investigated to what extent non-parenchymal liver cells could play an intermediary role in the expression of the PMA effect on ornithine decarboxylase activity in parenchymal liver cells. Addition of conditioned medium from PMA-activated Kupffer cells to cultured parenchymal cells led to the induction of ornithine decarboxylase activity in parenchymal cells. This effect was not observed with conditioned medium from untreated Kupffer cells or from Kupffer cells treated with PMA plus indomethacin. Conditioned media from PMA-treated or untreated endothelial liver cells were ineffective in the induction of ornithine decarboxylase activity in parenchymal liver cells. Prostaglandin D2, the main eicosanoid produced by Kupffer cells, was able to stimulate the synthesis of ornithine decarboxylase in parenchymal liver cells (up to 40-fold) in a dose-dependent way. Prostaglandin (PG) D2 appeared to be a more potent inducer of ornithine decarboxylase activity in parenchymal cells than PGE1 and PGE2. It is concluded that intercellular communication inside the liver mediated by prostaglandins derived from activated Kupffer cells may form a mechanism to induce synthesis of specific proteins in parenchymal cells.

Alprostadil↗
PubMed1989

Identification of the inhibitor of the plasminogen activator as the major protein secreted by endothelial rat liver cells.

Freshly isolated Kupffer and endothelial liver cells exhibit a rate of 'de novo' protein synthesis which is twice as high per mg cell protein as that of parenchymal liver cells and contribute significantly (7.5% and 5.9%, respectively) to total liver protein secretion. In parenchymal cells the main secretory protein is a 68 kDa protein (containing 19% fo the secreted radioactivity, presumably albumin). In Kupffer cells a 49 kDa protein contains 8% of the secreted radioactivity, while in endothelial liver cells a 55 kDa protein is the most prominent secretory protein (containing 11% of the secreted radioactivity). By aid of a specific antibody the 55 kDa protein was identified as the inhibitor of the plasminogen activator and in the liver this protein was only secreted by the endothelial cells.

Animals↗
PubMed1989

Vaccination of harbour seals (Phoca vitulina) against phocid distemper with two different inactivated canine distemper virus (CDV) vaccines.

Two inactivated canine distemper virus (CDV) vaccines--an adjuvanted whole inactivated virus and a subunit ISCOM preparation--were tested for their ability to induce protective immunity in harbour seals (Phoca vitulina) against phocid distemper, a disease that recently killed greater than 17,000 harbour seals in the North and Baltic seas, and was shown to be caused by infection with a newly discovered morbillivirus, which is antigenically closely related to CDV. Four CDV seronegative harbour seals were vaccinated three times with the whole-virus vaccine, two with the ISCOM subunit vaccine and two were sham-vaccinated with an antigen-free preparation. Ten days after the last vaccination, when all six vaccinated animals had developed CDV neutralizing antibody titres ranging from 300 to 3000, all eight animals were challenged by the oculonasal and the peritoneal routes, with an organ suspension from dead seals. None of the six vaccinated animals developed clinical signs. The two sham-vaccinated seals died on days 14 and 18, respectively, after having shown a body temperature rise, respiratory symptoms and weight loss. In organs from both dead animals morbillivirus antigen was demonstrated with an enzyme-linked immunosorbent assay and an immunofluorescence assay. One of these two animals had developed a low titre of CDV-specific antibodies just before death. These data clearly indicate that seals can be protected from fatal challenge with the phocid distemper virus (PDV), by vaccination with certain inactivated CDV vaccines. They also reconfirm that infection with PDV should be considered the primary cause of the recent epizootic in seals.

Animals↗
PubMed1988

The induction of glycogenolysis in the perfused liver by platelet activating factor is mediated by prostaglandin D2 from Kupffer cells.

Induction of glycogenolysis in the perfused liver by platelet activating factor (PAF) was blocked by the cyclooxygenase inhibitor indomethacin. 3H-labeled PAF was shown to interact in the perfused liver primarily with Kupffer cells. The addition of PAF to Kupffer cells resulted in a dose-dependent stimulation of prostaglandin D2 (PGD2) production, which was identified as the main eicosanoid formed after PAF stimulation of the Kupffer cells. PGD2 was able to induce a dose-dependent stimulation of glycogenolysis both in the perfused liver and in isolated parenchymal cells. The time-dependency of the PGD2 production and the glucose output by the perfused liver is consistent with a primary interaction of PAF with the Kupffer cells, followed by PGD2 formation, which subsequently stimulates glucose production in parenchymal cells.

Animals↗