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Query: UNIPROT:P43026 (lipopolysaccharide)
 62,215 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A novel system was used previously to characterize the dynamic interaction of a polysaccharide-deficient, lipid-rich lipopolysaccharide (LPS) with rabbit erythrocytes (RaRBC). Exposure of the RaRBC to the LPS rendered them sensitive to induction of hemolysis by the cationic antibiotic polymyxin B (PB) in a time- and temperature-independent manner. Subsequent decay in the response of LPS-sensitized cells to PB was shown to be critically dependent on both the time and temperature of incubation of RaRBC with LPS and to be independent of a change in LPS binding (Carr and Morrison, Infect. Immun. 43:600-606, 1984). In the present study, we performed experiments designed to define the mechanism by which PB mediates hemolysis of LPS-sensitized RaRBC. Experiments were performed to examine the molecular requirements of the LPS and the PB that were essential for hemolytic activity. The capacity of various cations to mediate hemolysis of LPS-sensitized RaRBC or to block PB-mediated hemolysis and the temperature dependence of the PB lytic reaction were investigated. The results of these experiments suggest that PB-mediated hemolysis of LPS-treated erythrocytes is dependent upon an initial ionic association of PB with erythrocyte membrane-bound LPS, followed by hydrophobic insertion of the PB fatty acid into the erythrocyte membrane lipid bilayer.
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PMID:Mechanism of polymyxin B-mediated lysis of lipopolysaccharide-treated erythrocytes. 298 82

Smooth lipopolysaccharide (sLPS) of Brucella abortus was prepared and fractionated by a modification of the procedures of Moreno et al. (J. Bac. 138:361-369, 1979). Washed B. abortus cells were disrupted by 21 freeze-quick thaw cycles with ultrasonication to separate the non-membrane-bound material. Ultrasonicated bacteria were used for preparation of membrane-bound sLPS (approximately f5, the main crude sLPS fraction described by Moreno et al.). Phenol extraction was repeated 3 times and then washed with H2O 10 times to remove most of the chromogen, polysaccharides and nucleic acids, eliminating the need for enzyme treatment as described previously. The membrane-bound sLPS was fractionated into 3 to 5 groups according to the extent of dialysis and centrifugation, these fractions required only 80 ng for positive ELISA, about 0.2 ng for positive Limulus lysate tests, and reacted well with precipitating antibodies in the serum from a strain 2308 infected cow. They had marked differences in precipitin curves and chemical composition. The protein content varied from 16% to 42% as determined by dye binding test and 17 to 60% by Lowry phenol method using bovine serum albumin as the standard, which implies that the proteins associated with LPS may also play important roles in the complex for the immunochemical interactions and the heterogeneity of B. abortus lipopolysaccharide protein complex. As compared with previous reports, a higher yield of sLPS, ranging from 3.6% to 7.7% of dried bacteria, was obtained. Group f5A, which had a standard bell shaped curve in the precipitin assay, is one of the major fractions in all three strains (1119.3, 19 and 2308). The amount of other subfractions obtained varied with batches or strains of B. abortus. These results provide a new profile of the immunochemical reactivities and the heterogeneity on B. abortus smooth membrane-bound endotoxins.
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PMID:Immunochemical and partial chemical characterization of fractions of membrane-bound smooth lipopolysaccharide-protein complex from Brucella abortus. 311 18

Immunoglobulin gene expression in normal splenic B lymphocytes stimulated with lipopolysaccharide was selectively down-regulated by anti-IgM antibodies and a protein-kinase C-activating phorbol ester, phorbol 12,13-dibutyrate. This control was concomitant with a decreased rate of transcription of the IgM gene while "polymerase pausing" was induced in the IgD gene. The suppression was resistant to treatment with cycloheximide, indicating that it was not caused by a labile repressor protein. The down-regulation of immunoglobulin gene expression affected only the secretory form of immunoglobulin, while the mRNA levels for the membrane-bound form of immunoglobulin remained unaltered. We conclude that the mechanisms controlling immunoglobulin gene expression in untransformed B lymphocytes differ from those operating in tumors derived from the same cell lineage.
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PMID:Regulation of immunoglobulin transcription rates and mRNA processing in proliferating normal B lymphocytes by activators of protein kinase C. 312 13

The uptake of quinolone antibiotics by Escherichia coli was investigated by using fleroxacin (RO 23-6240, AM 833) as a prototype compound. The uptake of fleroxacin was reduced and its MIC was increased in the presence of magnesium. Quinolones induced lipopolysaccharide release, increased cell-surface hydrophobicity and outer membrane permeability to B-lactams, and sensitized cells to lysis by detergents. These effects were also antagonized by magnesium and were very similar to those seen with EDTA and gentamicin. MICs of quinolones in portin-deficient strains were increased relative to those of the parent strain, consistent with a porin pathway of entry. However, MICs were further increased in the presence of magnesium; the size of the additional increase showed a positive correlation with quinolone hydrophobicity in an OmpF- OmpC- OmpA- strain. When quinolones were mixed with divalent cations in solution, changes in quinolone fluorescence suggestive of metal chelation were observed. The addition of fleroxacin to a cell suspension resulted in a rapid initial association of fluorescence with cells, followed by a brief decrease and a final time-dependent linear increase in cell-associated fluorescence. We interpret these results as representing chelation of outer membrane-bound magnesium by fleroxacin and other quinolones, dissociation of the quinolone-magnesium complex from the outer membrane, and diffusion of the quinolone through both porins and exposed lipid domains on the outer membrane. For a given quinolone, the contribution of the porin and nonporin pathways to total uptake is influenced by the hydrophobicity of the quinolone.
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PMID:Routes of quinolone permeation in Escherichia coli. 313 91

Smooth lipopolysaccharide (sLPS) of Brucella abortus, which is the most immunodominant component among the antigens of B. abortus isolated, has been used for diagnosis for decades. High yields of sLPS can be prepared by a modification of the procedures of Moreno et al. (J. Bacteriol. 138:361-369, 1979). Washed B. abortus cells can be disrupted by 21 freeze-quick thaw cycles and ultrasonication to separate non-membrane-bound material; then phenol extraction is performed 3 times and the phenol fraction is washed with H2O intensively. The membrane-bound sLPS can be fractionated into 3 to 5 groups according to the extent of dialysis and centrifugation. These membrane bound sLPS fractions show marked individual differences in their precipitin profile and chemical composition. Their protein content varies from 16% to 42% as determined by dye binding test and 17 to 60% by Lowry phenol method using bovine serum albumin as the standard, which indicates that these proteins associated with LPS may play important roles in the immunochemical interactions, solubility, and the heterogeneity of B. abortus lipopolysaccharides. Compared to previously published methods, a higher yield of sLPS, ranging from 3.6% to 7.7% of dried bacteria, is obtained. Group f5A, which has a standard bell shaped curve in the precipitin assay, is one of the major fractions in all three strains (1119.3, 19, 2308). The protein free sLPS (less than 1% of Lowry reactive component) can be prepared by pronase digestion. The immunochemical reactivity remains about the same before and after this treatment. The O-chains of the major fraction (f5A) of B. abortus (Strains 2308 and 19) membrane bound smooth lipopolysaccharide (sLPS) are obtained by hydrolysis of f5A native sLPS in 1% acetic acid at 100 degrees C for 2 hours. After hydrolysis, the O-chains are separated from the lipid A protein complex by centrifugation, and from small fragments by ultrafiltration of a molecular weight cut-off (MWCO) of 1.0 x 10(3). These carbohydrate haptens can be identified by precipitin-inhibition assay and further fractionated by both membrane filtration and dialysis. The size distributions of carbohydrate haptens of the endotoxins (f5A) ranged from several oligosaccharides up to 1.0 x 10(4) MWCO. Three major fractions of MWCO 8.0-10.0 x 10(3), 3.5-5.0 x 10(3), and less than 1.0 x 10(3) for both strains 2308 and 19 contain more than 85% of the total immunreactive materials.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Structural and immunochemical aspects of Brucella abortus endotoxins. 314 Jun 12

In this work we have addressed two questions. Does switch recombination occur before membrane expression or only concomitantly with induction to high rate synthesis and secretion of IgG? Does interleukin-4 induce switch to IgG1 or maturation of already switched cells? To answer these questions we used the DNA synthesis inhibitor hydroxyurea (HU) to analyze the requirements for DNA replication in the induction of membrane expression or high rate secretion of all IgG subclasses by cultures of mouse spleen cells stimulated by lipopolysaccharide (LPS) and supplemented with IL-4, the absolute numbers of cells bearing membrane bound IgG was always decreased by HU, indicating that immunoglobulin class switching requires DNA replication. IL-4 did not augment the numbers of cells expressing any IgG isotype. In contrast, the number of high rate secretors of all IgG isotypes was not affected by HU, except in the case of IgG3 and IgG2b shortly after stimulation. Addition of IL-4 resulted in an increased number of secretory cells, and also this effect was resistant to HU. Thus, for any isotype, treatment with HU or IL-4 increased the frequency of secretory cells relative to the surface positive population. This data indicates that: 1) IL-4 is a broad range, non isotype-specific maturation factor for LPS-activated B cells; 2) induction to high rate secretion has a negative effect on proliferation; and 3) immunoglobulin class switch, but not induction to secretion of any immunoglobulin isotype, requires DNA replication, suggesting that switch recombination had to occur before expression of IgG in the membrane-bound form.
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PMID:Membrane expression of IgG but not maturation to secretion requires DNA replication. 326 37

Ultrastructural and morphometric profiles of type-II pneumocytes (P-II) were investigated in rats killed 18 or 24 hours after a single intratracheal inoculation of bacterial (Escherichia coli) lipopolysaccharide (LPS). Inoculation with LPS induced pulmonary injury and inflammation, as measured by increased lactate dehydrogenase and alkaline phosphatase activities and increased numbers of polymorphonuclear neutrophils in fluid collected by bronchoalveolar lavage. Marked ultrastructural changes and desquamation of a few P-II developed at the time of high activity of lactate dehydrogenase and alkaline phosphatase in bronchoalveolar lavage fluid. Ultrastructural changes included swollen mitochondria and localized cisternal dilatation of the endoplasmic reticulum in which was contained membrane-bound homogenous material of medium electron density. Twenty-four hours after LPS inoculation, point-count stereologic analysis and digitizing morphometry revealed greater than 50% increase in P-II size. Changes in cell size corresponded with ultrastructural finding of swollen cells. Results obtained by point-count stereologic analysis and digitizing morphometry were highly correlated (r = 0.95). Lamellar bodies (LB) comprised 12 to 15% of P-II volume. Volume density and number of LB remained unaltered in LPS-injured P-II, and evidence of accelerated release of LB was not detected after LPS inoculation. Exudated polymorphonuclear neutrophils and pulmonary alveolar macrophages were involved actively in the phagocytosis of LB originating from necrotic and desquamated P-II. On the basis of measurement of enzyme activity (enzymes released into the bronchoalveolar space), considerable ultrastructural alterations developed in P-II when maximal LPS-induced pulmonary cell injury took place.
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PMID:Profiles of type-II pneumocytes in rats inoculated intratracheally with bacterial lipopolysaccharide. 331 9

DMN exposure modulates cellular immunity through alterations in the maturation and hematopoiesis of macrophages. DMN-exposed bone marrow stem cells gave rise to increased colony-forming unit-macrophage (CFU-M) colonies while the resulting colonies produced fewer cells/colony. Bone marrow-derived macrophages phenotypically had decreased cells expressing Ia antigens or cells in the S-phase following DMN treatment. Concanavalin A-elicited peritoneal exudate cells from DMN-treated animals demonstrated an increase in the percentage of macrophages and in the number of immature, bi-nucleated cells obtained as well as a concomitant increase in the percentage of Ia antigen-expressing cells. Concanavalin A-elicited peritoneal exudate cells from DMN-exposed animals also had an increased secreted interleukin-1 activity following lipopolysaccharide stimulation without any alteration in the expression of membrane-bound interleukin-1. Thioglycolate-elicited peritoneal exudate cells from DMN-exposed animals demonstrated no changes in cellularity and only showed increases in the percentage of bi-nucleated cells. There were no alterations in the capacity of T cells obtained from DMN-treated animals to respond to either soluble (keyhole limpet hemocyanin) or allo-antigens; nor were there alterations in the capacity of these T cells to either produce or respond to interleukin-2. These findings suggest that the observed DMN-induced modulation(s) in cell-mediated immunity results from changes in macrophage hematopoiesis due to alterations in: the production of regulatory factors controlling their production and/or differentiation or their ability to respond to these factors.
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PMID:Alteration of macrophage differentiation into accessory and effector cells from exposure to dimethylnitrosamine (DMN) in vivo. 349 Apr 56

The expression of membrane and secreted IgM was analyzed during mitogen-induced differentiation of the murine B cell lymphoma CH12. To characterize the Ig genes used by CH12, the nucleotide sequences of the variable gene segments (V mu and V kappa) were determined. The expressed V mu gene segment belongs to the VHII NPb-related family. The D (FL16.1a) and J (JH2) segments are the same as those used by the NP-specific hybridoma B1-8. The V kappa used by CH12 is almost identical to those used by the oxazolone-specific hybridomas NQ5.89.4 and NQ7.7.1. Treatment with lipopolysaccharide (LPS) induces up to 80% of CH12 cells to secrete IgM within 48 hr of culture. The steady state levels of secreted mu (mu s) and kappa mRNA increase four to fivefold over this period in cells stimulated with LPS compared with unstimulated cells. The kinetics are similar for both mRNA and parallel the increase in IgM secretion. EL-4 supernatants induce comparable changes in m mu s and kappa transcript levels. The simultaneous increase in m mu s and kappa transcripts suggests that coordinate control of RNA levels is used to increase the synthesis of secretory IgM during differentiation. The level of mRNA encoding the membrane form of mu (mu m) remains constant in stimulated cells and increases slightly in unstimulated cells. While the net rates of synthesis of membrane-bound mu-chains remain similar during LPS stimulation, the level of surface IgM on secreting cells is reduced three to fivefold. These observations suggest that the level of surface IgM expression during differentiation of CH12 is controlled largely by post-translational mechanisms. Our results demonstrate that the CH12 cell line regulates the expression of membrane and secreted IgM differently during its differentiation. The changes in IgM expression in CH12 parallel those occurring in normal B cells after mitogen or antigen challenge. Thus, the in vitro differentiation of CH12 is a good model for the analysis of late stages of B cell development.
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PMID:The expression of membrane and secreted immunoglobulin during the in vitro differentiation of the murine B cell lymphoma CH12. 350 Feb 20

Mononuclear phagocytes, a specialized cell lineage comprising bone-marrow precursors, blood monocytes and tissue macrophages, can interact with blood coagulation mechanisms with resulting thrombus formation or extravascular fibrin accumulation. Such procoagulant activity is usually activation dependent and requires interaction of the cells with immune or nonimmune stimuli. In the former case (e.g., alloantigens, soluble protein antigens) collaboration of mononuclear phagocytes with T lymphocytes is necessary and is mediated by cell-to-cell contact or lymphokines. Prototype of a direct acting stimulus is bacterial lipopolysaccharide. Mononuclear phagocyte procoagulant activity is expressed in the form of cell membrane-bound or released factors which display molecular heterogeneity. They include the initiator of the extrinsic clotting pathway, tissue factor, known clotting proteases such as factors V and VII, and novel proteolytic enzymes including prothrombinase and a factor X activator. Mononuclear phagocyte procoagulants are pathogenetically involved in generalized disorders with intravascular coagulation and thromboembolic phenomena. These disorders, exemplified by the Shwartzman reaction and possibly by paraneoplastic thromboembolism, are initiated by blood monocytes. Extravascular fibrin deposition can be initiated by tissue-infiltrating monocytes and macrophages in disease states such as acute renal allograft failure and solid tumours.
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PMID:Macrophage procoagulant factors--mediators of inflammatory and neoplastic tissue lesions. 353 56


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