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K Resch

Publications and source records attributed to K Resch.

At least 91 records · Page 5Linked to original sources
PubMed1988

Influence of blood volume on cerebrospinal fluid levels of arachidonic acid metabolites after subarachnoid hemorrhage: experimental study on the pathogenesis of cerebral vasospasm.

Based on accumulating data indicating the important role of arachidonic acid metabolites in the pathogenesis of cerebral vasospasm, we examined the influence of alterations in blood volume on the cerebrospinal fluid (CSF) level of the subarachnoid hemorrhage (SAH). Three separate injections of autologous blood into the cisterna magna of dogs within subarachnoid hemorrhage (SAH). Three separate injections of autologous blood into the cisterna magna of dogs within 72 hours were performed. Three experimental groups were formed, with an overall injected blood volume of 6, 9, and 12 ml. Arterial spasm was verified by comparison of the angiographic diameter of the basilar artery on Day 8 vs. Day 1. Additionally, light microscopic, scanning and transmission electron microscopic, and freeze cracking technique examinations of the basilar artery demonstrated the typical morphological features of proliferative vasculopathy. Increasing the volume of experimental SAH led to a linear decrease of the mean vessel diameter from 45% to 53% and finally to 75% of normal. Parallel to the reduction of angiographic vessel lumen, a volume-dependent significant increase of all three eicosanoids was demonstrated. A deficiency of prostacyclin concentration during the course of the experiment was not observed. Despite highly elevated CSF levels of vasodilating prostacyclin, however, severe angiographic constriction of the basilar artery occurred in the presence of high concentrations of TXA2 and PGE2. It is concluded that increasing volumes of SAH led to a concomitant release of arachidonic acid metabolites during posthemorrhagic clot lysis. From our data, it seems questionable whether a prostacyclin deficiency is an important underlying factor for the development of cerebral spasm.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Activation of glomerular mesangial cells by gram-negative bacterial cell wall components.

The cell walls of gram-negative bacteria contain several biologically active components, including lipopolysaccharide (LPS), lipoprotein, and protein 1. The effects of these individual components and a synthetic analog of lipoprotein, TPP, on several activation parameters of glomerular mesangial cells (MC) were examined. Prostaglandin secretion, synthesis of the autogrowth factor, mesangial interleukin-1 (IL-1), and new synthesis of cellular proteins were assessed as markers of MC activation. All bacterial cell wall components evaluated were active in varying degrees as stimulants of prostaglandin secretion. In general, PGE was the predominant product. TPP and protein 1 also induced substantial secretion of thromboxane. Each cell-wall component was effective in stimulating mesangial IL-1 secretion. The activation of MC was associated with the enhanced synthesis of many cellular proteins in addition to IL-1. Stimulation by these bacterial components was dependent on the state of the mesangial cell cycle, because nonproliferating cells did not respond to these factors. Activation of MC by gram-negative bacterial cell wall components, with release of vasoactive prostaglandins and peptide mitogens, may be responsible for some of the glomerular hemodynamic alterations and cellular proliferative events associated with sepsis or chronic bacterial infection.

Animals↗
PubMed1988

Sulfhydryl reagents as model substances for eicosanoid research.

The rate of eicosanoid synthesis is controlled by the availability of free arachidonic acid. Recently we showed that inhibition of reacylation of liberated fatty acids by the sulfhydryl group-blocking agent thimerosal increased prostaglandin as well as leukotriene synthesis. In order to gain further insight into the basic regulatory mechanisms controlling cellular eicosanoid production, the effects of different sulfhydryl reagents on prostaglandin E2 synthesis in the macrophage-like cell line P388D1 were investigated. As these cells exhibit an enormous acyl turnover of cellular phospholipids even under basal conditions, any interference with their fatty acid deacylation-reacylation cycle should lead to a change in intracellular concentrations of the eicosanoid precursor arachidonic acid. Therefore, arachidonic acid release from prelabelled cells as well as arachidonic acid incorporation into different phospholipid species under the influence of mercuric chloride (HgCl2), ethylmercurithiosalicylate (thimerosal), p-hydroxymercuribenzoic acid (PHMB), 0-(3-hydroxymercuri-3-methoxypropyl)carbamoyl-phenoxyacetic acid (mersalyl), N-ethylmaleimide (NEM), and ethacrynic acid were examined. Additionally, direct effects of those substances on corresponding enzyme activities, i.e. phospholipase A2 (PLA2), acyl-CoA synthetase, and lysophospholipid acyltransferase (LAT), on glutathione levels, and on cell viability were estimated. The results demonstrate that the organic mercury compound thimerosal was the most effective in enhancing free arachidonic acid levels, and concomitantly prostaglandin E2 synthesis in P388D1 cells, as result of a rather selective inhibition of the fatty acid reacylating enzyme LAT.

Acyltransferases↗
PubMed1987

A novel metabolic pathway for leukotriene B4 in different cell types: primary reduction of a double bond.

Addition of leukotriene B4 together with trace amounts of tritiated leukotriene B4 to different cell types, such as bone marrow-derived macrophages, T-lymphocytes, mesangial cells or fibroblast tumor cells, led to the formation of several hitherto unknown degradation products within hours. None of them could be identified as 20-hydroxy- or 20-carboxyleukotriene B4, known to be produced by polymorphonuclear leukocytes. The primarily formed transient leukotriene B4 metabolite was less polar than leukotriene B4 and was detectable by measuring its ultraviolet absorbance at 232 nm or its radioactivity. Mass spectral analysis showed very similar fragmentation spectra of leukotriene B4 and its primary metabolite. The most abundant ion and the main fragments of the new metabolite were increased by two mass units compared to leukotriene B4. These observations suggest that, in a variety of cells, leukotriene B4 is first reduced to a 5,12-dihydroxyeicosatrienoic acid, which is further converted to secondary hydrophilic degradation products. This raises the question of the major route of leukotriene B4 metabolism in vivo.

Animals↗
PubMed1987

Polyunsaturated fatty acids are enriched in the plasma membranes of mitogen-stimulated T-lymphocytes.

Plasma membranes were purified from T-lymphocytes from rabbit thymus stimulated with concanavalin A. Lipids were extracted and the fatty acid composition of the individual phospholipid species was determined by gas-liquid chromatography. Compared to the plasma membranes derived from control cells, the plasma membranes from mitogen-stimulated cells were enriched in polyunsaturated fatty acids. This increase in unsaturation was found in phosphatidylcholine, phosphatidylinositol and phosphatidylserine, while the fatty acid composition of phosphatidylethanolamine was not significantly altered. The phospholipid composition remained almost unchanged during the period of stimulation. The molar ratio cholesterol to phospholipid was decreased. These changes in the lipid composition of plasma membranes from mitogen-stimulated T-lymphocytes are discussed with regard to functional implications.

Animals↗
PubMed1987

The diacylglycerols dioctanoylglycerol and oleoylacetylglycerol enhance prostaglandin synthesis by inhibition of the lysophosphatide acyltransferase.

Prostanoids are synthesized by resident macrophages upon stimulation with diacylglycerols. Oleoylacetylglycerol and dioctanoylglycerol induced prostaglandin E and thromboxane synthesis in a time- and concentration-dependent manner. Both diacylglycerols inhibited the lysophosphatide acyltransferase, which is the key enzyme in the reacylation of arachidonic acid. By this mechanism the pool of free arachidonic acid available for prostanoid synthesis is increased. Both diacylglycerols were able to inhibit the membrane-bound lysophosphatide acyltransferase by a direct interaction independent of protein kinase C. Thus lysophosphatide acyltransferase could be shown to be a new target of these diacylglycerols, known as activators of protein kinase C.

Acyltransferases↗
PubMed1987

Separation of plasma membrane domains of calf thymocytes by affinity chromatography on ouabain-Sepharose.

Highly purified plasma membranes of calf thymocytes were fractionated by means of affinity chromatography on ouabain-Sepharose. By the method used two subfractions were obtained, one eluting freely from the affinity gel (MF1oua) and a second specifically retained by matrix-bound ouabain (MF2oua), with a total recovery of 95 per cent. Fractionation required the binding of matrix-bound ouabain to its plasma membrane receptor, i.e. (Na+ + K+)-ATPase. Increasing the temperature and binding time did not significantly alter the fractionation of plasma membranes into the two subfractions. Both plasma membrane subfractions separated by ouabain-Sepharose were of plasma membrane origin, as revealed by the identical specific activities of several membrane bound enzymes, gamma-glutamyl transpeptidase, alkaline phosphatase and Mg2+-ATPase in unseparated plasma membranes and in both subfractions, and by the identical amounts of the cytoskeletal protein actin in unseparated plasma membranes and subfractions. The plasma membrane subfractions MF1oua and MF2oua showed different structural and functional properties. In SDS-polyacrylamide gel electrophoresis polypeptides of 170, 150, 110, 94, 39, and 30 kDa were several-fold enriched in the adherent fraction, MF2oua. The phospholipid fatty acid composition of the plasma membrane subfractions proved to be different, as well. MF2oua contained significantly higher amounts of saturated fatty acids as compared to MF1oua. The specific activities of (Na+ + K+)-ATPase, Ca2+-ATPase and lysolecithin acyltransferase were highly enriched in the adherent fraction MF2oua, as compared to MF1oua. The data suggest that by the means of affinity chromatography on ouabain-Sepharose plasma membrane domains of the lymphocyte plasma membrane can be isolated, most probably implicated in the initiation of lymphocyte activation.

Animals↗
PubMed1987

Phospholipid-metabolism of a stimulated murine T cell clone.

The release of IP3 and the incorporation of arachidonic acid into phospholipids was measured in a stimulated murine alloantigen-specific, non-cytolytic T cell clone. While Concanavalin A provoked a sharp increase in IP3, Interleukin 2 had no effect on the production of IP3. An increased reacylation of phospholipids with arachidonic acid was seen within the first 4 hours after addition of Concanavalin A, while an effect upon Interleukin 2 was only observed after 8 hours of incubation with Interleukin 2. A similar retarded response to Interleukin 2 was observed in proliferation experiments. These retarded cell responses may be due to changed properties of IL 2 receptors induced by IL 2.

Animals↗
PubMed1987

Activation of glomerular mesangial cells by the terminal membrane attack complex of complement.

Treatment of cultured renal glomerular mesangial cells (MC) with nonlytic concentrations of the purified components (C5b-9) of the terminal membrane attack complex (MAC) of complement induced significant functional alterations characteristic of cellular activation. C5b-9-treated MC released large quantities of primarily vasodilatory prostaglandins. In addition, the secretion of an MC-derived auto-growth factor (MC interleukin 1) was greatly enhanced. Examination of the action of C5b-9 on MC phospholipid metabolism indicated that complement induced the activation of phospholipases, leading to quantitative changes in the fatty acid profile of MC membrane phospholipids. These findings demonstrate that cultured MC are highly responsive to nonlytic concentrations of the C5b-9 complex, and suggest that the mesangial deposition of the MAC in many forms of glomerular disease, with resultant cellular activation, may play a major role in the hemodynamic and cellular proliferative events characteristic of these disorders.

Animals↗
PubMed1987

The immunosuppressive activities of different cyclosporins are correlated to inhibition of the early membrane phospholipid metabolism in activated lymphocytes.

Recently, it could be shown that Cyclosporin A (CsA) inhibited the activation of T and B lymphocytes by interfering with an early step of the activation, namely the stimulation of the plasma membrane-bound lysophosphatide acyltransferase. In this report, we compared three CsA-derivatives, Dihydro-Cyclosporin C (Dihydro-CsC), "C9-O-Acetyl"-CsA (CsAAC), Cyclosporin H (CsH), regarding the inhibition of proliferation and the interference with the activation of the phospholipid metabolism. At concentrations below 1 microgram/ml, CsAAC and CsH had no effect on any parameter measured. Dihydro-CsC, however, closely resembled CsA: it inhibited the induction of DNA- and RNA-synthesis in T and B lymphocytes from mesenteric lymph nodes of rabbits. Similar to CsA, Dihydro-CsC also interfered with the enhanced incorporation of arachidonic acid into plasma membrane phospholipids by inhibiting the activation of the lysophosphatide acyltransferase. The close correlation between inhibition of proliferation and interferences with the phospholipid metabolism of the plasma membrane suggested that Dihydro-CsC as well as CsA interfered with an early step of lymphocyte activation at the level of the plasma membrane.

1-Acylglycerophosphocholine O-Acyltransferase↗
PubMed1987

Functional domains of the T lymphocyte plasma membrane: characterization of the polypeptide composition.

Highly purified plasma membranes from calf thymocytes were fractionated by affinity chromatography on Concanavalin A-Sepharose into two subfractions, one eluting freely from the affinity column (MF1) and a second being specifically retained (MF2). SDS-polyacrylamide-gel-electrophoresis revealed different polypeptide patterns of the two plasma membrane subfractions. Polypeptides of apparent molecular weights of 170, 150, 110, 94, 39, and 30 kDa were several-fold enriched in the adherent fraction, MF2. In contrast, several proteins in the 55-65 kDa range were preferentially recovered in the non-adherent fraction. Five Five of the six polypeptides, preferentially recovered in MF2 proved to be glycoproteins, the 39 kDa peptide was non-glycosilated. The differences in the amounts of the polypeptides specifically enriched in the adherent fraction MF2 became even more clear-cut when plasma membranes solubilized with non-ionic detergents (lysolecithin, ET-18-2H, Triton-X-100) were separated by affinity chromatography on Concanavalin A-Sepharose. The non-glycosilated peptide of apparent molecular weight of 39 kDa was recovered together with several glycoproteins in the adherent fraction, MF2, suggesting that not single glycoproteins, but plasma membrane domains were separated by Concanavalin A-Sepharose. Although the glycoproteins of the non-adherent fraction MF1 bound significant amounts of Concanavalin A, the major Concanavalin A binding glycoproteins were recovered in the adherent fraction, MF2. The plasma membrane subfractions showed also different functional properties, the specific activities [Na+ + K+]AT-Pase, Ca2+ ATPase and lysolecithin acyltransferase were several-fold enriched in the adherent fraction, MF2, as compared to MF1. The data suggest the existence of plasma membrane domains in the plasma membranes of thymocytes consisting of a different set of proteins, among others the major Concanavalin A binding glycoproteins with some membrane bound enzymes, probably implicated in the initiation of lymphocyte activation.

Animals↗
PubMed1987

Induction of responsiveness to interleukin 2 in mouse lymphocytes by synergistic action of ionophore A 23187 and diacylglycerol.

We investigated whether the protein kinase C-binding agents 12-O-tetradecanoyl-phorbol-13-acetate (TPA) and 1-oleoyl-2-acetyl-rac-glycerol (OAG) induced reactivity to interleukin 2 (IL-2) in mouse lymphocytes. 10(-8) M TPA was a strong inducer of reactivity to IL-2 measured by [3H]thymidine incorporation. In contrast OAG alone (6-25 micrograms/ml) did not induce a significant IL-2 mediated proliferative response. Cells stimulated with the ionophore A 23187 + OAG neither proliferated nor produced IL-2. In contrast, cells stimulated with A 23187 + OAG + IL-2 showed a significant proliferative response, indicating the expression of functional high affinity IL-2 receptors. The expression of reactivity to IL-2 induced by A 23187 + OAG was inhibited by 0.04 mM Mn2+; in contrast the TPA-mediated induction of IL-2 responsiveness was not affected by Mn2+. The data suggest differences in the mechanism of induction of IL-2 responsiveness by the two protein kinase C-binding agents, TPA and OAG.

Animals↗
PubMed1987

Pitfalls in measuring fluorescence polarization in mitogen-stimulated T-lymphocytes.

Fluorescence polarization measurements with the probe 1,6-diphenyl-1,3,5-hexatriene (DPH) were performed to detect changes in the fluidity of plasma membranes from T-lymphocytes stimulated with mitogens. When the cells were incubated with succinyl-concanavalin A an increase in fluorescence polarization was observed. This, however, could be shown to be due to the interaction of the mitogen with the label DPH and did not reflect changes in the plasma membrane. In purified plasma membranes a decrease rather than an increase of fluorescence polarization was observed.

Animals↗
PubMed1987

Interleukin I and the glomerular mesangium. II. Monokine stimulation of mesangial cell prostanoid secretion.

Monocytic (MC) infiltration is a prominent feature of many forms of immune-mediated glomerulonephritis. Through the release of interleukin-1, (IL-1), monocyte/macrophages have been shown to induce the proliferation of mesangial cells and to stimulate the secretion of a glomerular basement membrane-degrading neutral proteinase. In addition, mesangial cells release a cytokine that expresses many of the biologic properties of monocyte IL-1, including stimulation of mesangial cell proliferation. Because many of the actions of IL-1 are mediated by the induction of prostanoid prostaglandin (PG) synthesis, the authors determined the effects of purified macrophage and mesangial IL-1 on the secretion of prostaglandin E (PGE), prostacyclin, and thromboxane. The results indicated that cycling MCs release primarily PGE in response to purified IL-1. The local release by either monocytes or mesangial cells of IL-1 during glomerular inflammation, with subsequent mesangial cell generation of vasodilatory PGE, may be responsible in part for the alterations in the glomerular microcirculation observed in these disorders.

Animals↗
PubMed1987

[The effect of benzydamine on prostaglandin synthesis in macrophages].

The influence of benzydamine (Tantum) on the prostaglandin metabolism of rat peritoneal macrophages was studied. Contrary to conventional non-steroidal antiinflammatory drugs, e.g. piroxicam and acetylsalicylic acid, benzydamine did not inhibit PGE1/2 synthesis, but was rather stimulatory at 10(-4) mol/l. The increase of PGE1/2 synthesis might be explained by the inhibition of the lysophosphatide acyltransferase. This enzyme together with the arachidonic acid liberating phospholipase A2 regulates the concentration of arachidonic acid by the reincorporation into membrane phospholipids. Enhanced arachidonic acid may be metabolized via the cyclooxygenase to prostanoids.

Alprostadil↗
PubMed1986

A possible role of protein kinase C in regulating prostaglandin synthesis of mouse peritoneal macrophages.

The addition of the analogue of diacylglycerol, 1-oleoyl-2-acetylglycerol (OAG), to resident macrophages isolated from the peritoneal cavity of mice led to a dose and time dependent increase in the synthesis of prostaglandin E. This was likely due to an enhanced amount of arachidonic acid available for eicosanoid synthesis as OAG suppressed the incorporation of arachidonic acid into cellular phospholipids by inhibiting acyl-CoA:lysophosphatide acyltransferase. Since OAG has been shown to activate protein kinase C in various cells, these data lead us to suggest that synthesis of eicosanoids in peritoneal macrophages is mediated by the activation of protein kinase C.

Acyltransferases↗