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K Vosbeck

Publications and source records attributed to K Vosbeck.

At least 37 records · Page 2Linked to original sources
PubMed1991

Cyclic AMP mimics, but does not mediate, interleukin-1- and tumour-necrosis-factor-stimulated phospholipase A2 secretion from rat renal mesangial cells.

We have previously shown that recombinant interleukin 1 (IL-1) and recombinant tumour necrosis factor (TNF) synergistically stimulate phospholipase A2 release from mesangial cells. We now report that treatment of mesangial cells with the beta-agonist salbutamol, prostaglandin E2 (PGE2), cholera toxin or forskolin, which all activate adenylate cyclase, increased release of phospholipase A2 activity. Likewise, addition of a membrane-permeant cyclic AMP (cAMP) analogue or the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine enhanced release of phospholipase A2 activity from mesangial cells. There was a lag period of about 8 h before a significantly enhanced secretion could be detected. Furthermore, actinomycin D or cycloheximide completely suppressed cAMP-stimulated secretion of phospholipase A2. Angiotensin II, the phorbol ester phorbol 12-myristate 13-acetate, the Ca2+ ionophore A23187 and a membrane-permeant cGMP analogue did not stimulate phospholipase A2 release from the cells. Treatment with indomethacin completely inhibited IL-1 beta- and TNF-stimulated PGE2 synthesis, without having any effect on phospholipase A2 secretion, thus excluding cytokine-induced PGE2 synthesis as the mediator of phospholipase A2 release. Neither IL-1 beta nor TNF induced any increase in intracellular cAMP in mesangial cells. Furthermore, incubation of the cells with 2',5'-dideoxyadenosine, an inhibitor of adenylate cyclase, did not block cytokine-stimulated phospholipase A2 secretion. In addition, IL-1 beta and TNF synergistically interacted with forskolin to stimulate phospholipase A2 release from the cells. The protein kinase inhibitors H-8, staurosporine, K252a and amiloride inhibited IL-1 beta- and TNF-stimulated phospholipase A2 secretion. However, high concentrations that inhibit other protein kinases were needed. These observations suggest that IL-1 beta and TNF cause secretion of phospholipase A2 by a mechanism independent of cAMP. The signalling pathways used by IL-1 beta and TNF may involve a protein kinase that is probably different from protein kinase A or protein kinase C.

Animals↗
PubMed1991

Mapping the receptor binding domain of interleukin-1 beta by means of binding studies using overlapping sequence fragments: why did it fail?

Interleukin-1 (IL-1) alpha and beta are polypeptide hormones that mediate a broad range of biological activities and interact with surface receptors on numerous cell types. Great efforts are made at present to define the interaction domain of IL-1 with its receptor. We have tried to map the domain of IL-1 beta by assessing the receptor interaction of synthetic octapeptide acid amides representing overlapping segments of the IL-1 beta primary sequence. Since the tertiary structure of IL-1 beta is known, the selection of octapeptides could be confined to the surface exposed residues. More than a 100 octapeptides were tested for binding in a competitive binding assay, using a mouse thymoma cell line (EL 4.61) as a receptor source and 125I-IL-1 alpha and beta as radioligands. No binding was found at up to a one hundred fold excess of octapeptide over radioligand. From this lack of binding we conclude that the entropic cost of conformationally freezing the octapeptide is high and that the conformation of the binding domain is per se in terms of free energy and is stabilized by the overall tertiary structure of IL-1.

Amino Acid Sequence↗
PubMed1990

Transforming growth factor beta 2 differentially modulates interleukin-1 beta- and tumour-necrosis-factor-alpha-stimulated phospholipase A2 and prostaglandin E2 synthesis in rat renal mesangial cells.

Treatment of rat glomerular mesangial cells with transforming growth factor beta 2 (TGF beta 2) stimulates prostaglandin E2 (PGE2) synthesis. Actinomycin D, cycloheximide and diclofenac attenuate the TGF beta 2-induced PGE2 formation. As shown previously, two proinflammatory cytokines, interleukin 1 beta (IL-1 beta) and tumour necrosis factor alpha (TNF alpha), are potent stimuli for PGE2 and phospholipase A2 secretion from mesangial cells. We report here that, whereas TGF beta 2 potentiates the IL-1 beta- and TNF alpha-evoked PGE2 production, it strongly inhibits the phospholipase A2 secretion induced by both cytokines. In addition, the inhibitory effect of TGF beta 2 on phospholipase A2 secretion is not due to the augmented PGE2 formation.

Animals↗
PubMed1990

Priming of polymorphonuclear granulocytes by lipopolysaccharides and its complexes with lipopolysaccharide binding protein and high density lipoprotein.

Human peripheral blood neutrophils are primed, or enabled to respond to formyl peptide, by prior exposure to bacterial lipopolysaccharide (LPS). The activity of LPS and the size of its aggregates are altered by plasma constituents such as high density lipoprotein (HDL) and the recently discovered acute phase reactant lipopolysaccharide binding protein (LBP) Tobias et al.: J. Exp. Med. 164,777, 1986]. The ability of LPS, LPS-LBP, and LPS-HDL complexes to activate a number of cellular responses have been compared. LPS-LBP and LPS-HDL were prepared using LBP and HDL from rabbit serum. LPS from Salmonella minnesota Re595 and its LPS-LBP and LPS-HDL complexes differed in their ability to prime PMN O2- production in response to formyl peptide (f-Nle-Leu-Phe-Nle-Tyr-Leu [FNLPNTL]). Human PMN prepared under conditions in which O2- production is minimal (less than 1 nmol O2-/10(6) PMN/10 min) after exposure to 10(-7) M FNLPNTL can be primed with 0.1-100 ng/ml LPS in a dose- and time-dependent manner to produce up to 12 nmol O2-/10(6) PMN/10 min. LBP complexation accelerated the priming induced by LPS, whereas HDL complexation retarded it. Priming was accompanied by a parallel two- to threefold increase in formyl peptide receptor number as determined by FACS analysis of fluoresceinated FNLPNTL binding and SDS-PAGE autoradiographic analysis of photoaffinity ligand binding. Thus binding of LPS to plasma proteins changes the response of the PMS to LPS and may represent one way in which the response of the PMN is regulated during infection. Since LBP concentrations change during an acute phase response, complexation of LPS with LBP is a mechanism that may regulate neutrophil responses in vivo during inflammation.

Acute-Phase Proteins↗
PubMed1990

Resistance of Escherichia coli to rifampicin and sorangicin A--a comparison.

Sorangicin A, a macrolide polyether antibiotic and the ansamycin antibiotic rifampicin inhibit DNA-dependent RNA polymerase to a similar extent. Resistance to sorangicin A is due to a mutation in the RNA polymerase which renders the enzyme less sensitive. Parallel investigations with rifampicin revealed partial cross-resistance, which was more marked in sorangicin A-resistant mutants than in rifampicin-resistant mutants.

Aminoglycosides↗
PubMed1989

Interleukin 1 and tumor necrosis factor synergistically stimulate prostaglandin synthesis and phospholipase A2 release from rat renal mesangial cells.

Treatment of rat glomerular mesangial cells with recombinant human interleukin 1 alpha (rIL-1 alpha), recombinant human interleukin 1 beta (rIL-1 beta) or recombinant human tumor necrosis factor (rTNF) induces prostaglandin E2 (PGE2) synthesis and the release of a phospholipase A2 (PLA2) activity. rIL-1 beta is significantly more potent than rIL-1 alpha or rTNF in stimulating PGE2 as well as PLA2 release from mesangial cells. When given together, rTNF interacts in a synergistic fashion with rIL-1 alpha and rIL-1 beta to enhance both, PGE2 synthesis and PLA2 release. The released PLA2 has a neutral pH optimum and is calcium-dependent. Pretreatment of cells with actinomycin D or cycloheximide inhibits basal and cytokine-stimulated PGE2 and PLA2 release.

Animals↗
PubMed1987

Role of oxidants in DNA damage. Hydroxyl radical mediates the synergistic DNA damaging effects of asbestos and cigarette smoke.

The mechanism by which cigarette smoking and asbestos exposure synergistically increase the incidence of lung cancer is unknown. We hypothesized that cigarette smoke and asbestos might synergistically increase DNA damage. To test this hypothesis we exposed isolated bacteriophage PM2 DNA to cigarette smoke and/or asbestos, and assessed DNA strand breaks as an index of DNA damage. Our results supported our hypothesis. 78 +/- 12% of the DNA exposed to both cigarette smoke and asbestos developed strand breaks, while only 9.8 +/- 7.0 or 4.3 +/- 3.3% of the DNA exposed to cigarette smoke or asbestos, respectively, developed strand breaks under the conditions of the experiment. Our experimental evidence suggested that cigarette smoke and asbestos synergistically increased DNA damage by stimulating .OH formation. First, significant amounts of .OH were detected by electron paramagnetic resonance (EPR) in DNA mixtures containing both cigarette smoke and asbestos, but no .OH was detected in mixtures containing cigarette smoke alone or asbestos alone. Second, the .OH scavengers, dimethylsulfoxide (DMSO), mannitol, or Na benzoate decreased both .OH detection by EPR and strand breaks in DNA mixtures exposed to cigarette smoke and asbestos. Third, the H2O2 scavenger, catalase, and the iron chelators, 1,10-phenanthroline and desferrithiocin, decreased both .OH detection and strand breaks in DNA mixtures exposed to cigarette smoke and asbestos. These latter findings suggest that iron contained in asbestos may catalyze the formation of .OH from H2O2 generated by cigarette smoke. In summary, our study indicates that cigarette smoke and asbestos synergistically increase DNA damage and suggests that this synergism may involve .OH production.

Asbestos↗
PubMed1986

Induction of inflammatory mediators from human polymorphonuclear granulocytes and rat mast cells by haemolysin-positive and -negative E. coli strains with different adhesins.

We investigated the role of various E. coli strains that expressed different adhesins and/or generated haemolysin with regard to the induction of inflammatory mediators, e.g. histamine release from rat mast cells as well as the chemiluminescence response and the release of lipoxygenase transformation products from human polymorphonuclear neutrophils. Our data show that the degree of haemagglutination did not parallel the induction of the chemiluminescence response. Haemolysin-negative bacteria with different adhesins induced more 5-hydroxyeicosatetraenoic acid as compared to haemolysin-positive bacteria, which generated more leukotriene B4 as compared to 5-hydroxyeicosatetraenoic acid. Among the leukotrienes, more leukotriene B4 as compared to leukotriene C4 was released from peripheral leucocytes. Studies with rat mast cells showed that histamine release was dependent on the haemolysin activity expressed by washed bacteria or present within the bacterial culture supernatant. Histamine release was markedly diminished when haemolysin activity decayed. Several haemolysin-negative bacteria with defined adhesins also released histamine, suggesting that, in addition to haemolysin, other factors contribute to mediator release. Thus, various properties of bacteria (e.g. adhesins, haemolysin) may participate to varying degrees in the induction of inflammatory mediators, e.g. oxygen radicals, lipoxygenase transformation products, leucotrienes and histamine.

Adhesins, Escherichia coli↗
PubMed1985

Uptake, intracellular activity, and influence of rifampin on normal function of polymorphonuclear leukocytes.

Quinone and hydroquinone forms of rifampin accumulated in normal polymorphonuclear leukocytes (PMN) (maximal cellular to extracellular concentration ratio [C/Emax] +/- standard error of the mean, 9.36 +/- 0.54 and 8.82 +/- 0.65, respectively, after 5 to 10 min) and chronic granulomatous disease PMN (C/Emax, 13.76 +/- 0.77 and 14.29, respectively). Uptake of rifampin was influenced by incubation temperature and extracellular pH but not by phorbol myristate acetate stimulation or metabolic inhibitors. At extracellular concentrations between 0.06 and 5.0 mg/liter, rifampin significantly reduced the number of staphylococci surviving inside chronic granulomatous disease PMN, thus compensating for the bactericidal defect inherent with this disease. Spontaneous migration and chemotaxis of normal PMN were unaffected by rifampin. However, phagocytosis of yeast particles and oxygen consumption of stimulated PMN were moderately depressed, and O2- production and chemiluminescence were significantly depressed in a dose-dependent manner. The bactericidal activity of normal PMN was not impaired. Inhibition of chemiluminescence and O2- release were also observed in a cell-free system. We conclude that rifampin possesses favorable characteristics for the effective elimination of intracellular microorganisms. Further studies are needed to evaluate the in vivo significance of ion scavenging by rifampin, which could be hazardous to immunocompromised patients.

Adult↗
PubMed1985

Experimental hematogenous infection of subcutaneously implanted foreign bodies.

Implanted foreign bodies are highly susceptible to pyogenic infection. Whereas infection up to 3 months after surgery is probably due to perioperative bacterial contamination, little is known about the pathogenesis of late prosthetic infections. We employed an animal model to determine whether subcutaneously implanted foreign bodies were susceptible to experimental bacteremia. Tissue cages were implanted into guinea pigs, which were infected at the earliest 4 weeks later by intracardiac injection of Staphylococcus aureus Wood 46. The injection of 2 X 10(6) cfu did not result in any infection. Inoculation of 5 X 10(7) cfu resulted in a bacteremia of 10(2)-10(3) cfu/ml after 5 min and led to 11/26 selective tissue cage infections with no microbiological evidence of infection elsewhere. Higher inocula caused systemic infections with foci in different organs. Rifampin (7.5 mg/kg b.i.d.) was administered for 48 h, starting at different times after infection to establish the best timing for efficacious short-term therapy. When treatment was begun 1 h before or 3 h after inoculation, complete protection was observed, whereas 1/12 and 3/15 tissue cages remained infected when the first dose was not given until 24 h and 48 h, respectively, after inoculation. These experiments illustrate that implanted prostheses are highly susceptible even to bacteremias with low density of microorganisms. Prophylaxis can prevent such infections, whereas delayed short-term treatment may fail.

Animals↗
PubMed1984

Antibiotic action on phagocytosed bacteria measured by a new method for determining viable bacteria.

Antibiotics such as rifampin that act on phagocytosed bacteria have clinical advantages. The investigation of such intraphagocytic activity of antibiotics is, however, hampered by the time-consuming and cumbersome procedures necessary for enumerating viable bacteria. We have developed a semiautomatic biophotometric method for this purpose that permits the processing of relatively large numbers of samples. Using this method with Staphyloccus aureus Wood 46 as a test organism, we studied the dose dependence of the activities of a number of antibiotics against intraphagocytic bacteria. We could confirm the very good intracellular activity of rifampin. Its activity at low concentrations was slightly better against intracellular than against extracellular bacteria. In contrast, clindamycin and erythromycin, both of which have been reported to accumulate within phagocytes, did not exhibit a correspondingly enhanced intracellular activity, erythromycin being active intracellularly only at high concentrations. Clindamycin and vancomycin were effective against intracellular organisms, but only at relatively high concentrations owing to their low bactericidal activity against S. aureus Wood 46. Penicillin G, ampicillin, gentamicin, and streptomycin exhibited no useful intracellular activity. These results demonstrate that radioactive accumulation studies of antibacterial agents are not sufficient to show intracellular activity. Intracellular activity must be demonstrated in a functional test, preferably with graded concentrations of the test substance.

Anti-Bacterial Agents↗
PubMed1984

Duodeno-pancreatic secretions enhance bactericidal activity of antimicrobial drugs.

We have studied the action of various antimicrobial agents in microbiological media and in human duodeno-pancreatic secretions. In the latter medium, clioquinol exhibited a rapid bactericidal effect on both growing and stationary bacteria at concentrations near its MIC. However, it was merely bacteriostatic in microbiological media, even at high concentrations. Phanquinone, chlorquinaldol, and, to a lesser extent, also chloramphenicol and trimethoprim likewise displayed enhanced bactericidal activity in duodeno-pancreatic secretions, but various other antibacterial agents did not. These findings suggest that duodeno-pancreatic secretions contain a factor augmenting the antibacterial activity of a number of drugs.

Adult↗
PubMed1983

Effect of swainsonine on the processing of the asparagine-linked carbohydrate chains of alpha 1-antitrypsin in rat hepatocytes. Evidence for the formation of hybrid oligosaccharides.

The biosynthesis of the proteinase inhibitor alpha 1-antitrypsin has been studied in rat hepatocyte primary cultures. Newly synthesized alpha 1-antitrypsin was found in hepatocytes as a glycoprotein of an apparent molecular weight of 49,000 carrying oligosaccharide side chains of the high mannose type. In the hepatocyte medium a secreted alpha 1-antitrypsin of an apparent molecular weight of 54,000 could be identified as a glycoprotein with carbohydrate chains of the complex type. Pulse-chase experiments revealed a precursor-product relationship for the two forms of alpha 1-antitrypsin. When the hepatocytes were treated with swainsonine, an intracellular form of alpha 1-antitrypsin with an apparent molecular weight of 49,000 indistinguishable from that of control cells was found. However, the alpha 1-antitrypsin secreted from swainsonine-treated hepatocytes was different from that present in control media. It was characterized by a lower apparent molecular weight (51,000), a higher amount of [3H]mannose incorporation, half as much incorporation of [3H]galactose, and the same amount of [3H]fucose incorporation compared to alpha 1-antitrypsin of control media. In contrast to the 54,000 complex type alpha 1-antitrypsin from control media the 51,000 alpha 1-antitrypsin from the medium of swainsonine-treated cells was found to be susceptible to the action of endoglucosaminidase H, even when fucose was attached to the proximal GlcNAc residue. alpha 1-Antitrypsin secreted from swainsonine-treated cells combines features usually associated with either high mannose or complex type oligosaccharides and therefore represents a hybrid structure. In spite of its effect on the carbohydrate part of alpha 1-antitrypsin swainsonine did not impair the secretion of the incompletely processed glycoprotein.

Alkaloids↗
PubMed1983

Lectin-resistant variants of mouse melanoma cells. II. In vitro characteristics.

Lectin-resistant variants of B-16 melanoma cells were selected with wheat-germ agglutinin, ricin and concanavalin A. They exhibited altered metastasizing capacity and tumorigenicity in C57BL mice. Several in vitro properties were defined and compared including homotypic adhesiveness, microfilament organization, melanin release, activity of tyrosine hydroxylase, DNA content, and karyotypes. The possible relevance of these properties in vitro for the malignant behavior displayed in vivo is discussed. The usefulness of this approach of selecting surface variants to study the problem of metastasis is also discussed.

Animals↗
PubMed1983

Fimbria-specific antibodies detach Escherichia coli from human cells.

Antibodies obtained from rabbits immunized with purified adhesion-mediating fimbriae of Escherichia coli SS142 were specific for the fimbriae of the homologous strain; they did not cross-react with isolated fimbriae of three different E. coli strains or with protein extracts from nine other adhesive E. coli strains. The antibodies inhibited adhesion to Intestine 407 tissue culture cell monolayers and hemagglutinating activity of E. coli SS142 but not of several other E. coli strains. The antibodies were able not only to prevent but also to reverse the adhesion of E. coli SS142 to Intestine 407 cells or human erythrocytes. Analysis of the kinetics of inhibition suggested that the antibodies did not competitively inhibit adhesion. Such antibodies can be useful for distinguishing different mechanistic steps of bacterial adhesion. Their ability to reverse bacterial adhesion in vitro may be of clinical relevance.

Adhesiveness↗