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 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

This paper deals with the behavior of adult mouse bone marrow cells placed in tissue culture with or without antigen, and subsequently assessed for immune competence after adoptive transfer into lethally X-irradiated, syngeneic hosts. Attention was focussed on B lymphocytes through using hapten human gamma globulin (HGG) preparations as putative tolerogens in tissue culture, the T-cell-independent antigens DNP-POL and NIP-POL as challenge injections in adoptive hosts, and numbers of hapten-specific PFC in host spleens for the quantitation of immune competence. It was found that the capacity of bone marrow cells to mount an adoptive immune response rose by a factor of about fivefold over 3 days in tissue culture. This rise was completely abolished by the presence in the culture of hapten-HGG conjugates with about one mole of hapten per carrier molecule. The prevention of the emergence of immune competence amongst maturing B cells was termed clonal abortion tolerogenesis. Dose-response studies showed the lowest effective antigen concentration to be between 2.5 times 10- minus 10 and 2.5 times 10- minus 9 M, and a standard concentration of 2.5 times 10- minus 8 M was chosen as producing near maximal effects. The tolerance was antigen-specific and time-dependent, being maximal only when antigen was present continuously as the cultured cells was maturing. It did not depend on the presence of T lymphocytes in marrow, and was not of an "infectious" type. In contrast to tolerogenesis of mature B lymphocytes by high antigen concentrations, it could not be abolished by lipopolysaccharide. We speculate that clonal abortion may be a tolerance mechanism of great physiological significance for self-recognition, and discuss the results in the framework of other recent tolerance models, including those involving receptor blockade and suppressor T cells.
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PMID:Evidence for the clonal abortion theory of B-lymphocyte tolerance. 4 89

Indoleamine 2,3-dioxygenase (molecular weight about 42,000) has been purified from rabbit intestines and contains one mole of protohaem IX as the sole prosthetic group. It catalyses the oxidative cleavage of the pyrrole ring of various indoleamines with a much broader specificity of substrate than tryptophan 2,3-dioxygenase. The enzyme has an absolute requirement for superoxide anion for catalytic activity. The enzyme was induced specifically in the lungs of mice for 24 h after administration of the lipopolysaccharide fraction of E. coli. This increase is due to synthesis of enzyme protein and is specific for the lipopolysaccharide fraction. These results are interpreted to mean that indoleamine dioxygenase is induced in pulmonary inflammatory processes in response to an increase in production of superoxide anion, 5-hydroxytryptamine or other indoleamines in the lung as a consequence of inflammation. The dioxygenase reaction is a more innocuous way of disposing of superoxide than dismutation.
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PMID:Specific induction of pulmonary indoleamine 2,3-dioxygenase by bacterial lipopolysaccharide. 25 62

Because of increased interest in surface carbohydrates of Rhizobium in relation to host specificity, phenol-water extractions were carried out of whole cells of Rhizobium strains of the species R. leguminosarum, R. phaseoli, R. trifolii and R. meliloti. Fractionation of the crude extracts with cetavlon afforded polysaccharide mixtures, which were essentially free of RNA and acidic exopolysaccharide (EPS). They could be separated into a high molecular weight heteropolysaccharide fraction of lipopolysaccharide (LPS) nature and a low molecular weight glucan fraction. Glucan turned out to be the principal polysaccharide component of the cells (up to 10% of the dry cell weight), when cultivated in carbohydrate-rich media, and to be present as firmly attached capsular material. Glucan (mol wt 3000) structure was elucidated by methylation and periodate oxidation techniques. Methylation yielded 3, 4, 6-tri-O-methyl-D-glucose, characterized by GLC-MS, as the only product of hydrolysis of the fully methylated glucan. The glucan consumed 1 mole of periodate per mole anhydroglucose unit and gave sophorose on partial hydrolysis. From these data a linear beta-1,2-linked glucan structure was deduced. The occurrence of beta-1,2-glucan and the implications for the specific binding properties of Rhizobium cells are discussed.
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PMID:Surface carbohydrates of Rhizobium. I. Beta-1, 2-glucans. 58 86

The structure of the lipopolysaccharide from Escherichia coli K12, strain CR34 has been investigated. The lipopolysaccharide contains D-galactose, D-glucose, D-glucosamine, L-glycero D-mannoheptose, 2-keto-3-deoxyoctonate and lipid A. The core region does not contain D-glucosamine but contains galactose, glucose, and heptose in the molar ratios 1:3:6. Methylations were performed on the lipopolysaccharide and on the degraded polysaccharide obtained after acetic acid hydrolysis of the lipopolysaccharide. It was found that galactose is in terminal position partly in the form of galactopyranose, partly in the form of galactofuranose. A part of the heptose was found as unsubstituted heptofuranose. A mole of glucose was 1 leads to 2 linked and another mole of glucose was 1 leads to 6 linked. Periodate oxidation of the lipopolysaccharide followed by borohydride reduction eliminates galactose and only a part of glucose and of heptose. A mole of heptose gave mannose and thus it is unsubstituted in C6 and C7. One mole of glucose and one mole of heptose were not degraded by periodate oxidation.
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PMID:[Study of the lipopolysaccharide from Escherichia coli K12 CR34]. 77 Jan 68

Cells of the stable protoplast L-form of Proteus mirabilis contain 1.5 to 2 times more extractable lipid, mostly phospholipid, per dry weight than cells of the bacterial form. Under identical conditions of cultivation the qualitative and quantitiative composition of the phospholipid is very similar in both cell forms. The range of mole percentages of individual phospholipid species is 78-80 for phosphatidylethanolamine, 10-13 for phosphatidylglycerol, 3.9-5.5 for diphosphatidylglycerol and 1.0-2.1 for lysophospholipid. However, all phospholipid species in the L-form differ from those of the bacterial form by a lower content of long-chain fatty acids and a higher content of short-chain fatty acids. Growth of the L-form in the presence of growth-stimulating horse serum results in a change of phospholipid composition accompanied by the uptake of phospholipid and fatty acids from the serum into L-form phospholipid. L-form protoplasts synthesize the same two types of lipopolysaccharide, I and II, that were previously identified in the bacterial form of Proteus mirabilis. However, only small amounts of the more hydrophilic lipopolysaccharide II are present in the L-form. Lipopolysaccharides from both cell forms have virtually identical polysaccharide compositions but differ strikingly in the relative content of fatty acids in their lipid-A moieties. Molar ratios of tetradecanoic acid, hexadeconoic acid and 3-hydroxytetradecanoic acid are 5:1:6 in the bacterial form and 5:0:1:6 in the L-form grown in serum-free medium. The observated differences between the bacterial form and the protoplast L-form are interpreted as results of the adaptation of the L-form to life in the state lacking an envelope by formation of a physically more stable but still sufficiently fluid protoplast membrane. A rapid method based on fatty acid analysis for the simultaneous quantitative determination of phospholipid and lipopolysaccharide content of whole cells is reported.
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PMID:Phospholipid and lipopolysaccharide in Proteus mirabilis and its stable protoplast L-form. Difference in content and fatty acid composition. 78 31

The 2.05 angstrom (A) resolution crystal structure of a dodecasaccharide-Fab complex revealed an unusual carbohydrate recognition site, defined by aromatic amino acids and a structured water molecule, rather than the carboxylic acid and amide side chains and a structured water molecule, rather than the carboxylic acid and amide side chains that are features of transport and other carbohydrate binding proteins. A trisaccharide epitope of a branched bacterial lipopolysaccharide fills this hydrophobic pocket (8 A deep by 7 A wide) in an entropy-assisted association (association constant = 2.05 x 10(5) liters per mole, enthalpy = -20.5 +/- 1.7 kilojoules per mole, and temperature times entropy = +10.0 +/- 2.9 kilojoules per mole). The requirement for the complementarity of van der Waals surfaces and the requirements of saccharide-saccharide and protein-saccharide hydrogen-bonding networks determine the antigen conformation adopted in the bound state.
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PMID:Recognition of a cell-surface oligosaccharide of pathogenic Salmonella by an antibody Fab fragment. 171 10

To determine whether cysteine residues have a contribution to the mechanism of color silver staining, we silver stained sodium dodecylsulfate polyacrylamide gel electrophoresis separations of proteins which have few or no cysteines. Proteins without cysteine stained negatively (yellow against a yellow background) with silver. Proteins with one or more cysteines stained orange, red, brown, or green/gray depending on the mole percentage of cysteine and whether they contained covalently attached lipids. The colors could not be correlated with the mole percentages of cysteine of these proteins indicating that some components other than cysteine affect the staining color of cysteine-containing proteins. Silver staining of amino acids, sugars, nucleotide bases, or lipopolysaccharide dot-blotted onto nitrocellulose paper implicated adenine, lipids, the basic amino acids, and glutamine, but not sugars or other amino acids in silver/protein complexes.
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PMID:Requirement for cysteine in the color silver staining of proteins in polyacrylamide gels. 242 85

A gentle and rapid isolation procedure is described yielding fractions containing better than 95% pure OmpF porin of Escherichia coli BE with different amounts of bound lipopolysaccharide (LPS). The procedure employs continuous free-flow electrophoresis (FFE) in the presence of detergent above its critical micelle concentration. Total yields of around 45% were typically obtained when porin-enriched membrane extracts were processed. By use of analytical ultracentrifugation a molecular mass of 114,000 and a sedimentation coefficient S20,w of 5.0 S were determined for porin trimers containing approximately 1 mol of tightly bound LPS. This porin readily formed 3D crystals suitable for high-resolution X-ray diffraction analysis. Three other porin-LPS isoforms isolated by FFE revealed molecular masses of 120,000, 124,000, and 151,000, suggesting that, in addition to the tightly bound LPS, 1, 2, and 8 mol of loosely bound LPS were present per mole of porin trimer. Each of the four different isoforms was suitable for reconstitution into highly ordered protein-lipid membrane arrays. The membrane crystals obtained with the 151-kDa isoform exhibited a unit cell polymorphism similar to that previously reported.
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PMID:Rapid isolation of OmpF porin-LPS complexes suitable for structure-function studies. 254 70

Lipopolysaccharide was isolated from a phage-selected mutant of a wild strain of Aeromonas salmonicida by the aqueous phenol method. The lipopolysaccharide consisted of the R form, containing per mole, three moles of L-glycero-D-manno-heptopyranose, one mole of 3-deoxy-D-manno-2-octulosonic acid (dOclA) and lipid A. The dOclA was not fully assayable by the thiobarbituric acid methods usually used, but its degradation product was detected, after Smith degradation of the lipopolysaccharide, either as free 3-deoxy-2-heptulosonic acid (after hydrolysis) or substituted by a mannopyranosyl residue derived from heptose. Mass spectrometry indicated that the dOclA existed in the furanose form and was substituted by the heptose trisaccharide through position six. Methylation analysis, chemical degradation, chromium trioxide oxidation and nuclear magnetic resonance spectroscopy were used to identify the structure of the core oligosaccharide as: L alpha DHepp(1----2)L alpha DHepp(1----3)L alpha DHepp(1----6)dOclAf(2----.
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PMID:The structure of the heptose-3-deoxy-D-mannooctulosonic-acid region in a mutant form of Aeromonas salmonicida lipopolysaccharide. 378 Jul 44

The O-specific side-chain of the lipopolysaccharide from Escherichia coli O90 has been investigated using methylation analysis, partial hydrolysis, and NMR spectroscopy as the principal methods. It is concluded that the polysaccharide is composed of tetrasaccharide repeating-units having the following structure. [formula: see text] The polysaccharide contains approximately one mole of O-acetyl groups per repeating unit, located on the fucose residue.
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PMID:Structural studies of the Escherichia coli O90 O-antigen polysaccharide. 752 39


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