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K Decker

Publications and source records attributed to K Decker.

At least 127 records · Page 7Linked to original sources
PubMed1987

Biosynthesis of rat alpha 1-macroglobulin. Identification of an intracellular precursor.

Alpha 1-macroglobulin was purified from rat plasma by gel filtration (Sephacryl S-300) and ion exchange chromatography (DE52). Analysis of the purified alpha 1-macroglobulin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed two polypeptides: a light chain which could be resolved into a double band (36/38 kDa) and a heavy chain (160 kDa). Under non-reducing conditions complexes of 200 and 400 kDa could be demonstrated. Antibodies were raised against both chains of alpha 1-macroglobulin which did not cross-react with either rat alpha 2-macroglobulin or rat alpha 1-inhibitor 3. It was shown that in the medium of [35S]methionine-labeled hepatocytes the two subunits of alpha 1-macroglobulin are linked by disulfide bridges. Intracellularly, however, a high molecular mass polypeptide (185 kDa) could be immunoprecipitated with either the antiserum to the heavy or the light chain of alpha 1-macroglobulin, indicating the existence of a polyprotein precursor. Also in a cell-free translation system alpha 1-macroglobulin was synthesized as a polyprotein consisting of heavy and light chains (162 kDa). In a pulse-chase experiment using tunicamycin to block N-glycosylation, alpha 1-macroglobulin secretion was totally inhibited. This finding reflects the importance of the oligosaccharide side chains for the proteolytic processing to the two subunits and/or secretion of alpha 1-macroglobulin.

Animals↗
PubMed1987

The role of N-glycosylation for the plasma clearance of rat liver secretory glycoproteins.

The clearance of total rat liver secretory glycoproteins and of alpha 1-acid glycoprotein carrying no or different types of oligosaccharide side chains was studied in vivo and in the isolated perfused rat liver. In order to obtain unglycosylated or differently glycosylated forms of secreted glycoproteins, rat hepatocyte primary cultures were incubated with various inhibitors of N-glycosylation. Tunicamycin was used for the synthesis of unglycosylated (glyco)proteins, the mannosidase I inhibitor 1-deoxymannojirimycin for the synthesis of high-mannose type and the mannosidase II inhibitor swainsonine for the synthesis of hybrid-type glycoproteins. Glycoproteins carrying carbohydrate side chains of the complex type were synthesized by control hepatocytes. In vivo and in the perfused rat liver, high-mannose-type glycoproteins were cleared at the highest rate, followed by unglycosylated and hybrid-type glycoproteins. The lowest clearance rate was found for the glycoproteins with carbohydrate side chains of the complex type. For the highly glycosylated alpha 1-acid glycoprotein the differences in clearance rates were more pronounced. The following plasma half-lives were determined in vivo: complex type, 100 min; hybrid type, 15 min; unglycosylated form, 5 min; and high-mannose type less than 1 min. In the recirculating perfused liver 28% of complex-type alpha 1-acid glycoprotein, 40% of hybrid type, 47% of unglycosylated and 93% of high-mannose-type alpha 1-acid glycoprotein were removed from the perfusate within 2 h. It is concluded that N-glycosylation and processing to complex-type oligosaccharides seems to be of great importance for the circulatory life time of plasma glycoproteins.

Animals↗
PubMed1987

The inflammation mediators interleukin 1 and hepatocyte-stimulating factor are differently regulated in human monocytes.

Human peripheral monocytes can be induced by bacterial lipopolysaccharide to produce the inflammatory mediators interleukin 1 (IL 1) and hepatocyte-stimulating (HS) activity. IL1 and HS activities were separated by gel permeation chromatography. It is also shown that the two monokines are differently regulated. Evidence for this stems from the finding that monocytes cultured for 24 h lose their ability to produce IL1 in response to lipopolysaccharide, while synthesis of HS activity remains essentially unaffected.

Dose-Response Relationship, Drug↗
PubMed1987

Discrimination of hepatocyte-stimulating activity from human recombinant tumor necrosis factor alpha.

The involvement of tumor necrosis factor alpha (TNF alpha) in the regulation of acute-phase protein synthesis is currently under discussion. In this study the effect of human recombinant TNF alpha on the regulation of the 4 acute-phase proteins alpha 2-macroglobulin, albumin, alpha 1-proteinase inhibitor and alpha 1-acute-phase globulin was investigated in rat hepatocyte primary cultures. No changes in synthesis of any of the 4 proteins were observed. However, an acute-phase response similar to that in vivo could be generated by conditioned media from human monocytes containing natural TNF alpha. This response remained unchanged after neutralizing TNF alpha activity by the addition of a specific antibody to TNF alpha. It is concluded that the hepatocyte-stimulating activity synthesized by human monocytes is different from TNF alpha.

Acute-Phase Proteins↗
PubMed1987

Enhancement of neutrophil adherence to isolated rat liver sinusoidal endothelial cells by supernatants of lipopolysaccharide-activated monocytes. Role of tumor necrosis factor.

Supernatants of endotoxin-activated monocytes have been shown to stimulate human neutrophil adherence to rat liver sinusoidal endothelial cells 3-4-fold. Evidence will be presented that tumor necrosis factor (TNF) is responsible for this phenomenon: (a) in high-performance gel filtration of supernatants of lipopolysaccharide-activated monocytes, neutrophil adhesion-inducing activity coeluted with TNF activity measured in the L929 cell-lysing assay at 25-45 kDa; (b) anti-TNF antibody treatment of supernatants of activated macrophages abolished their adhesion-inducing activity; (c) human recombinant TNF alpha stimulated neutrophil adhesion to sinusoidal endothelial cells in a dose-dependent manner. In addition, polymyxine B sulfate, which was capable of neutralizing direct effects of lipopolysaccharide on neutrophil adhesion, could abolish neither the neutrophil-adhesion-inducing activity of the supernatants of endotoxin-activated monocytes nor the effect of human recombinant TNF itself. The neutrophil-adhesion-inducing activity was due both to a direct activation of neutrophils and to an influence of the sinusoidal endothelium itself by TNF: pretreatment of sinusoidal endothelial cells with TNF followed by thorough washing resulted in an increased neutrophil attachment. Protein synthesis by endothelial cells was not required. However, incubation of sinusoidal endothelium with TNF followed by anti-TNF antibody treatment abrogated the increased neutrophil adhesion. This suggests that TNF bound to sinusoidal endothelial cell surfaces was responsible for neutrophil adhesion. It is concluded that TNF by increasing granulocyte sticking to the endothelial lining of the liver sinusoids may play a significant role in endotoxin-induced inflammation of the liver as it is found in the septic state.

Animals↗
PubMed1987

Studies on synthesis and degradation of eicosanoids by rat hepatocytes in primary culture.

The potential of hepatocytes in primary cultures to degrade the prostanoids produced by Kupffer cells and to synthesize eicosanoids, especially leukotriene B4, after treatment with D-galactosamine was studied. Hepatocytes in primary cultures showed a substantial capability to degrade all the prostanoids produced by stimulated Kupffer cells. The rate of degradation, approx. 2 pmol/min per 10(6) hepatocytes, was nearly the same for the prostaglandins D2, E2 and F2a. Lower rates were determined for thromboxane B2 (0.4 pmol/min per 10(6) cells) and for 6-ketoprostaglandin F1a (0.2 pmol/min per 10(6) cells). The degradation products of these prostanoids lacked biological activity, e.g., reactivity with specific antibodies and the ability to contract segments of rabbit femoral artery. In the presence of 30 microM arachidonic acid, hepatocytes produced only very small amounts of prostaglandins and thromboxane, ranging from less than or equal to 22 to 50 fmol/30 min per 10(6) cells. Neither untreated nor D-galactosamine-treated hepatocytes released significant amounts of leukotriene B4. Hepatocytes appear to be the site of degradation rather than synthesis of eicosanoids in the liver.

6-Ketoprostaglandin F1 alpha↗
PubMed1987

Prostaglandin responses in isolated perfused rat liver: Ca2+ and K+ fluxes, hemodynamic and metabolic effects.

Addition of prostaglandin F2 alpha and prostaglandin E2 to isolated perfused rat liver led to a dose-dependent, transient net Ca2+ release, which was completed within 3 min. Withdrawal of the prostaglandins resulted in a Ca2+ re-uptake over a period of about 10 min. Simultaneously, these prostaglandins induced an increase of portal pressure, stimulated hepatic glucose output and 14CO2 production from [1-14C]glutamate and led to K+ movements across the hepatocyte plasma membrane similar to those observed with other Ca2+-mobilizing agents. With prostaglandin F2 alpha there was a close correlation between the net Ca2+ release and the maximal rate of initial net K+ uptake by the liver (linear regression coefficient r = 0.902; n = 20). Prostaglandin F2 alpha was more effective than prostaglandin E2 or D2. Because prostaglandins are known to be produced by hepatic non-parenchymal cells during stimulation by phagocytosis or by addition of extracellular ATP or UTP, these data suggest an interaction between non-parenchymal and parenchymal liver cells and point to a modulating role of prostaglandins in hepatic metabolism and microcirculation, which is mediated by Ca2+-mobilizing mechanisms.

Animals↗
PubMed1986

Clearance of acute-phase plasma proteins with no, high-mannose-, hybrid-, or complex type oligosaccharide side chains by the isolated perfused rat liver.

The clearance of the rat acute-phase proteins alpha 2-macroglobulin, alpha 1-proteinase inhibitor and alpha 1-acid glycoprotein with no, high-mannose, hybrid or complex type oligosaccharide side chains was determined in the isolated perfused rat liver. The differently glycosylated forms of the three proteins were obtained from rat hepatocyte primary cultures treated with different inhibitors of glycosylation. The complex type forms of the three proteins were essentially not cleared by the liver during 2 h of perfusion. Unglycosylated alpha 2-macroglobulin and alpha 1-acid glycoprotein decreased in the perfusate by about 50% after 2 h; unglycosylated alpha 1-proteinase inhibitor was not taken up by the liver. The high-mannose type forms of the three proteins were nearly totally cleared. After 2 h of perfusion 10%, 45% and 30% of the hybrid type forms of alpha 2-macroglobulin, alpha 1-proteinase inhibitor and alpha 1-acid glycoprotein, respectively, were cleared. The clearance rates of high-mannose and of hybrid type glycoproteins could be reduced to the rates of complex type glycoproteins by the addition of mannan to the perfusate. It is concluded that complex type glycosylation prevents the uptake of plasma glycoproteins by the liver.

1-Deoxynojirimycin↗
PubMed1986

Ganglioside biosynthesis in rat liver. Characterization of three sialyltransferases.

Three sialyltransferase activities involved in ganglioside biosynthesis were studied in Golgi-enriched preparations of rat liver: the formation of GM3, GD3 and GD1a. The conditions for the quantitative assays of these enzymatic reactions were standardized and optimized, with Triton X-100 being used as detergent. The apparent Km values of each sialyltransferase for N-acetyl-2-(5'-cytidylyl)neuraminic acid (1.5 mM with GM3 synthase, 0.2 mM with GD3 synthase, and 0.5 mM with GD1a synthase) and the respective glycolipid substrates (0.08 mM for lactosylceramide, 0.1 mM for GM3, and 0.5 mM for GM1) were determined. Competition experiments showed that the three sialyltransferase activities are three individual catalytic entities. Moreover, evidence was found that product inhibition may play a role in the regulation of the activity of sialyltransferases.

Animals↗
PubMed1986

Differential inhibition of prostaglandin and superoxide production by dexamethasone in primary cultures of rat Kupffer cells.

Dexamethasone inhibited the stimulus-induced prostaglandin E2 formation by rat Kupffer cells in primary culture, e.g. after treatment with zymosan, phorbol ester, calcium ionophore A23187, platelet-activating factor or lipopolysaccharide. Prostaglandin E2 production from added free arachidonic acid was not influenced by the hormone. The time course, as well as the partial inhibition of the hormone effect by actinomycin D and cycloheximide, point to the hormone-induced formation of a protein which regulates phospholipase A2. The hormone did not affect the phagocytotic activity of the Kupffer cells. The quantity of [3H]arachidonic acid incorporated into phospholipids was also not altered by dexamethasone. After stimulation with zymosan, [3H]arachidonic acid was liberated from phosphatidylcholine only. Superoxide generation by rat Kupffer cells was induced by zymosan, phorbol ester and, to a much smaller extent, by platelet-activating factor. A23187 and lipopolysaccharide were without effect. In contrast to prostaglandin formation, the generation of superoxide was not influenced by dexamethasone. These results indicate that in cultured rat Kupffer cells prostaglandin formation and superoxide generation are independently triggered processes.

Animals↗
PubMed1986

Different effects of the glucosidase inhibitors 1-deoxynojirimycin, N-methyl-1-deoxynojirimycin and castanospermine on the glycosylation of rat alpha 1-proteinase inhibitor and alpha 1-acid glycoprotein.

The glucosidase inhibitors 1-deoxynojirimycin, N-methyl-1-deoxynojirimycin and castanospermine were used to inhibit oligosaccharide processing in primary cultures of rat hepatocytes. Their effect on the glycosylation of alpha 1-proteinase inhibitor (alpha 1PI) and alpha 1-acid glycoprotein (alpha 1AGP) was studied. Of the three glucosidase inhibitors examined, 1-deoxynojirimycin inhibited not only oligosaccharide trimming but also glycosylation de novo of newly synthesized proteins, resulting in the formation of alpha 1PI with two and three (normally carrying three) and alpha 1AGP with two to five (normally carrying six) oligosaccharide side chains. In the presence of the glucosidase inhibitors, glucosylated high-mannose-type oligosaccharides accumulated. Whereas most of the endoglucosaminidase-H-sensitive oligosaccharides formed in the presence of 1-deoxynojirimycin contained only one glucose residue, N-methyl-1-deoxynojirimycin and castanospermine led mainly to the formation of oligosaccharides with three glucose residues. None of the three glucosidase inhibitors completely prevented the formation of complex-type oligosaccharides. Thus, in their presence, alpha 1PI and alpha 1AGP with a mixture of both high-mannose and complex-type oligosaccharides were secreted.

1-Deoxynojirimycin↗
PubMed1986

Biosynthesis of gangliosides in primary cultures of rat hepatocytes. Determination of the net synthesis of individual gangliosides by incorporation of labeled N-acetylmannosamine.

The ganglioside content of rat hepatocytes increases several-fold during the first 6 days in monolayer culture. To correlate increased levels with rates of de novo synthesis, the incorporation of N-acetyl-[6-3H]D-mannosamine into individual gangliosides was determined. The calculation of synthetic rates was made possible by the simultaneous measurement of the specific radioactivity of the immediate sialic-acid donor, CMP-Neu5Ac. The CMP-Neu5Ac content of hepatocytes was found by HPLC analysis to be 30.5 nmol/g of plated cells. The specific radioactivity of this precursor pool reached a constant plateau 5 h after addition of the labeled N-acetyl-mannosamine and remained constant for at least 70 h. The incorporation into individual gangliosides was measured in primary cultures of rat hepatocytes between 72 and 144 h after seeding. During this period, the increase in ganglioside levels was greatest. The highest rates of incorporation were seen in GD1a followed by GM3, GM1, GD3 and the polysialylated compounds. The following rates of synthesis (nmol per 60 h and mg of protein) were calculated: GD1a 0.68, GM3 0.59, GM1 0.36, GD3 0.13 and GT1 0.02. These values are compared with the net increase of the gangliosides as measured by the resorcinol reaction.

Animals↗
PubMed1985

[Decrease in nosocomial infection based on continuous monitoring and control. 7 years' experience in a women's clinic].

During a seven-year programme of surveillance and control of infection data were collected by a specialist hygiene nurse on 47 551 gynaecological, obstetric and post-partum patients. The infection rate was highest (40.5%) after major surgical procedures. Infection rate after cesarian section was 16%, eight times the rate after vaginal delivery (2%). The most frequent type of infection was of the urinary tract (70%), usually asymptomatic bacteriuria. Next most frequent were pelvic infections, abdominal wound infections, and phlebitis via an intravenous entry in long-term parenteral nutrition. During the period of observation bacteriuria rate decreased by 75%, the other nosocomial infections by 64%, febrile standard morbidity by 81%. The decrease is largely due to the infection surveillance programme with the employment of a specialist hygiene nurse.

Cross Infection↗
PubMed1985

Murine interleukin 1 stimulates alpha 2-macroglobulin synthesis in rat hepatocyte primary cultures.

In rat hepatocyte primary cultures recombinant interleukin 1 was found to stimulate alpha 2-macroglobulin synthesis, whereas albumin synthesis was decreased. Although recent experiments gave evidence that a hepatocyte-stimulating factor distinct from interleukin 1 must exist, we conclude that interleukin 1 exerts a direct effect on hepatocytes by inducing acute-phase protein synthesis.

Albumins↗
PubMed1985

Secretion of high-mannose-type alpha 1-proteinase inhibitor and alpha 1-acid glycoprotein by primary cultures of rat hepatocytes in the presence of the mannosidase I inhibitor 1-deoxymannojirimycin.

Two different forms of alpha 1-proteinase inhibitor and alpha 1-acid glycoprotein were found in primary cultures of rat hepatocytes. After a 2.5-h labeling period with [35S]methionine the high-mannose-type precursor of alpha 1-proteinase inhibitor (Mr 49000) and alpha 1-acid glycoprotein (Mr 39 000) and the mature-complex-type alpha 1-proteinase inhibitor (Mr 54 000) and alpha 1-acid glycoprotein (Mr 43 000-60 000) could be immunoprecipitated from the cells, but only the complex-type forms of the two glycoproteins were secreted into the hepatocyte media. When hepatocytes were incubated with the mannosidase I inhibitor 1-deoxymannojirimycin at a concentration of 4 mM, the 49 000-Mr form of alpha 1-proteinase inhibitor and the 39 000-Mr form of alpha 1-acid glycoprotein could be detected in the cells as well as in their media. Neither the secretion of alpha 1-proteinase inhibitor nor that of alpha 1-acid glycoprotein was impaired by 1-deoxymannojirimycin. While alpha 1-proteinase inhibitor and alpha 1-acid glycoprotein, secreted by control cells, were resistant to endoglucosaminidase H, alpha 1-proteinase inhibitor and alpha 1-acid glycoprotein, secreted by hepatocytes treated with 4 mM 1-deoxymannojirimycin, could be deglycosylated by endoglucosaminidase H. When the [3H]mannose-labeled oligosaccharides of alpha 1-proteinase inhibitor, secreted by 1-deoxymannojirimycin-treated hepatocytes, were cleaved off by endoglucosaminidase H and analyzed by Bio-Gel P-4 chromatography, they eluted at the position of Man9GlcNAc, indicating that mannosidase I had been efficiently inhibited. 1-Deoxymannojirimycin did not inhibit the synthesis or the cotranslational N-glycosylation of alpha 1-proteinase inhibitor or alpha 1-acid glycoprotein.

1-Deoxynojirimycin↗
PubMed1985

Unglycosylated rat alpha 1-proteinase inhibitor has a six-fold shorter plasma half-life than the mature glycoprotein.

The plasma half-lives of glycosylated and unglycosylated alpha 1-proteinase inhibitor-radioactively labeled with [35S]methionine in rat hepatocyte primary cultures - were determined in the rat. Unglycosylated alpha 1-proteinase inhibitor was synthesized by hepatocytes in the presence of tunicamycin. Media from hepatocytes containing 35S-labeled glycosylated or unglycosylated alpha 1-proteinase inhibitor were injected into the tail veins of rats. At different times after injection alpha 1-proteinase inhibitor was isolated from plasma by affinity chromatography with anti-alpha 1-proteinase inhibitor Sepharose. Radioactivity measurements revealed a plasma half-life of 170 min for glycosylated alpha 1-proteinase inhibitor and of 30 min for the unglycosylated form of the inhibitor.

Animals↗