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Biomedical subjects

C Moreno

Publications and source records attributed to C Moreno.

At least 199 records · Page 11Linked to original sources
PubMed1985

Structural and conformational features of the Escherichia coli K92 capsular polysaccharide.

Escherichia coli K92 polysaccharide, an alternating (2----8)-alpha- and (2----9)-alpha-linked heteropolymer of sialic acid, undergoes lactonisation (10-20%) at low pH or on treatment with a water-soluble carbodi-imide (greater than 90%). Under the latter conditions, the formation of O-acylisourea is a minor pathway. The antigenicity of the K92 polysaccharide is unaffected by lactonisation of approximately 10% of the residues, but is abolished by lactonisation of approximately 90% of the residues. The unexpected, relative resistance of the K92 polysaccharide to periodate oxidation contrasts with the behaviour of the meningococcal non-O-acetylated (O-Ac-) C polysaccharide, a (2----9)-alpha-linked homopolymer of sialic acid. Two-dimensional 13C-1H-n.m.r. correlation spectroscopy has been used to assign 1H chemical shifts which have aided the interpretation of a resolution-enhanced one-dimensional spectrum. This has led to a determination of conformational features of the K92 polysaccharide in solution. The side-chain adopts a conformation such that H-7 and H-8 are gauche in the (2----8)-alpha-linked residues (1a or 1b), but antiperiplanar in the (2----9)-alpha-linked residues (2). Molecular correlation times have been calculated and some aspects of internal motion elucidated.

Carbohydrate Conformation↗
PubMed1985

Immunity and protection of mice against Neisseria meningitidis group B by vaccination, using polysaccharide complexed with outer membrane proteins: a comparison with purified B polysaccharide.

A methodology for preparing outer membrane proteins (type specific) complexed to group B polysaccharide of Neisseria meningitidis is described. These complexes, low in nucleic acid and lipopolysaccharide content, were immunogenic in mice with induction of humoral antigroup B and antiprotein responses. Immunized mice were also protected against challenge with N. meningitidis group B strains of the same or a different type from that used for vaccination. Both immunity and protection were enhanced when the mice received a secondary immunization with the protein-polysaccharide complex. Additional data have shown the capacity of purified B polysaccharide to induce immunological memory, even though it is incapable of inducing a humoral response when given alone.

Animals↗
PubMed1985

Effect of aluminum ions on chemical and immunological properties of meningococcal group B polysaccharide.

Soluble salts of aluminum were examined for their capacity to complex with purified meningococcal group B polysaccharide. The formation of the complexes resulted, first, in a markedly reduced rate of internal esterification at acid pH and, consequently, prolonged stability of the antigen as measured by its reactivity with antibody at pH 4 and, second, in an increased resistance to neuraminidase. Al3+ complexes of B polysaccharides were tested for immunogenicity in mice and found to be no better than the purified polysaccharide in the Na+ or Ca2+ form. However, when Neisseria meningitidis type 6 protein (outer membrane) complexed to B polysaccharide was tested, a substantial increase in anti-B titers was detected, whereas antiprotein titers remained unchanged. The possibility of using combinations of metal-polysaccharide-outer membrane protein complexes as vaccines for humans is discussed.

Aluminum↗
PubMed1984

Rate, mechanism, and immunochemical studies of lactonisation in serogroup B and C polysaccharides of Neisseria meningitidis.

Meningococcal Serogroup B polysaccharide and colominic acid, which are (2----8)-alpha-linked homopolymers of sialic acid, undergo lactonisation at low pH at a rate which is dependent upon the molecular size and upon the salt form (Na+ or Ca2+). Meningococcal Serogroup C polysaccharide, a (2----9)-alpha-linked homopolymer of sialic acid with acetyl groups present at O-7 and/or O-8, reacts with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to give an O-acylisourea. The rate of formation of O-acylisourea does not differ substantially between O-acetylated (O-Ac+) C, non-O-acetylated (O-Ac-) C, and B polysaccharide. 13C-N.m.r. spectroscopy shows that, in the absence of O-acetyl groups, the majority of the activated carboxyl groups of C polysaccharide condense with an adjacent HO-8 to form a delta-lactone. Immunochemical studies show that the antigenicity of B polysaccharide is markedly reduced on lactonisation of less than 20%, as measured by a radioimmunoassay using an anti-B monoclonal antibody, and that low-molecular-weight colominic acid is poorly antigenic both before and after lactonisation, suggesting the presence of conformational determinants on B polysaccharide. In contrast, lactonisation and/or formation of O-acylisourea groups in the (O-Ac+)-C polysaccharide does not cause a significant decrease in the antigenicity, which is consistent with a sequential (structural) determinant on the molecule.

Hydrogen-Ion Concentration↗
PubMed1984

Conformational and dynamic differences between N. meningitidis serogroup B and C polysaccharides, using n.m.r. spectroscopy and molecular mechanics calculations.

1H-N.m.r. spectroscopy has been used to determine the conformation in aqueous solution of the sialic acid residues of the N. meningitidis serogroup B and non-O-acetylated (O-Ac-)-C polysaccharides, and of N-acetylneuraminic acid (NeuNAc). In all cases, the sugar adopts the 2C5 conformation. The side-chain of NeuNAc adopts a conformation such that H-7 and H-8 are approximately anti-periplanar. This conformation is also found in the (O-Ac-)-C polysaccharide, whereas H-7 and H-8 are gauche in the B polysaccharide. Molecular mechanics calculations have been used to probe the conformational preferences of the variously linked sialic acid residues, and the results are in general agreement with those based on the 1H-n.m.r. data. The 13C-n.m.r. spin-lattice relaxation-times have been interpreted in terms of the molecular dynamics of the B and (O-Ac-)-C polysaccharides. Molecular correlation times have been calculated and details of internal rotational or segmental motion elucidated. The C polysaccharide is characterised by internal or segmental motion in the C-7 to C-9 side-chain of the sialic acid repeating-unit, whereas the B polysaccharide has little or no such movement and tumbles in solution as a rigid species with internal rotation of only the pendant C-9 group. The conformational differences suggest a substantially different three-dimensional structure in solution for these polysaccharides.

Magnetic Resonance Spectroscopy↗
PubMed1984

Dialysis hypoxemia. Role of dialyzer membrane and dialysate delivery system.

Arterial blood gas values, carbon monoxide diffusion capacity, oxygen consumption, carbon dioxide production, respiratory quotient, minute ventilation, and pulmonary capillary blood flow were determined before and during hemodialysis. In addition, the effect of single passage through the dialyzer on blood carbon dioxide tension, pH, and bicarbonate concentration was evaluated. Acetate-based dialysate was used in all experiments. Cellulosic dialyzer with single-pass dialysate delivery system was used in one group, and polyacrylonitrile dialyzers with recirculating delivery system in another. Although hypoxemia occurred in both groups, it was more severe in the former group. Dialyzer carbon dioxide loss was significantly greater with single-pass dialysate delivery system and cellulosic dialyzers than with recirculating delivery system and polyacrylonitrile dialyzer. To differentiate the role of dialysate delivery system from that of the membrane, the experiments were repeated using recirculating delivery system and cellulosic dialyzer. This resulted in marked attenuation of hypoxemia and dialyzer carbon dioxide tension losses. Since other experimental conditions were the same, the observed differences were thought to be due to the difference in the mode of dialysate delivery. It thus appears that the mode of dialysate delivery per se can modify the changes in arterial oxygen tension during hemodialysis and should be added to the list of factors implicated in the genesis of dialysis hypoxemia.

Acrylic Resins↗
PubMed1984

Direct measurement of antibody affinity distribution by hapten-inhibition enzyme immunoassay.

A rapid, simple and reliable technique for determining the affinities of antibody subpopulations in a complex mixture is described. The principle of this method is that antigen conc can be represented as the amount of antigen immobilized on the polystyrene surface of a microwell containing a fixed vol of diluted antibody. Thus, by measuring the proportion of antibody bound to different wells coated with varying amounts of antigen, it is a straightforward matter to calculate an affinity distribution. We have verified that: (1) the amount of antigen bound to a polystyrene plate is proportional to the concn of antigen used for sensitization and follows a typical saturation curve; (2) the antibodies bound to plates sensitized with low concns of antigen are of higher affinity than those bound to plates sensitized with high concns of antigen; (3) an apparent affinity constant (aK) is defined as the reciprocal concn of free hapten required for 50% inhibition of antibody binding to immobilized antigen; (4) the aK determined by this method is in close agreement with the intrinsic affinity constant (K) measured by fluorescence quenching or the Farr assay; and (5) that during the course of immunization in vivo there is a clear shift to higher-affinity antibody subpopulations.

Animals↗
PubMed1984

[Multiple wounds in children. Apropos of 76 cases].

Polytraumatisms in the child are relatively unfrequent, less severe, and get a lower rate of deaths compared with polytraumatisms in the adult. The indirect traumatism, being most frequent, is explained by projection and ejection. Direct traumatism is scacre. A classification in 4 types is proposed: type I: visceral polytraumatised child, type II: multiple fractured one, type III: mixed visceral and multiple fractured one, type IV: the crippled one. Cranial trauma has to be noticed as being a constant one. The relative unfrequency of spine, belly and thoracic injuries; the most frequent happening of peripheral traumatisms; the severeness of mutilations are emphasised. Multiple fractured children are healed with very remaining mutilations; the social and economic load is heavy; the pophylactics hypothetical.

Adolescent↗
PubMed1983

Immunoglobulin isotype in the murine response to polysaccharide antigens.

Murine antisera specific for the alpha (1 leads to 3) and alpha (1 leads to 6)-linked glucosyl determinants of dextran, as well as for meningococcal polysaccharide group C, have been examined for the distribution of their immunoglobulin classes and subclasses. Whereas the thymus-independent anti-alpha (1 leads to 3) dextran response in BALB/c mice was found to be IgM greater than IgG3 greater than IgA, thus corresponding to previously published work, neither the alpha (1 leads to 6) response in its thymus-dependent or-independent form, nor the response to purified meningococcal polysaccharide, corresponded to this pattern. No preference for any of the IgG subclasses appeared for these antigens when given as thymus-independent carbohydrates. On the other hand, thymus-dependent forms of alpha (1 leads to 6) dextran showed an IgG1 greater than IgG3 greater than IgG2 pattern.

Animals↗
PubMed1983

Immunological properties of monoclonal antibodies specific for meningococcal polysaccharides: the protective capacity of IgM antibodies specific for polysaccharide group B.

Two IgM monoclonal antibodies, MB32 and MB34 specific for meningococcal polysaccharide group B have been raised. Both were detectable by radioimmunoassay and agglutination, but only MB34 was effective in counter immunoelectrophoresis and complement fixation. MB34 was also far more potent than MB32 when tested for passive protection of mice infected with either Neisseria meningitidis group B or Escherichia coli K1. These data demonstrate that group B-specific antibodies do play a protective role in mice infected with these bacteria.

Animals↗
PubMed1981

Sialic acid polysaccharide antigens of Neisseria meningitidis and Escherichia coli: esterification between adjacent residues.

Colominic acid and meningococcal Group B polysaccharide, both (2 leads to 8)-alpha-linked homopolymers of sialic acid, are made water-insoluble either by reaction with a carbodiimide in aqueous solution at pH 4.75 or by treatment with 48% aqueous hydrofluoric acid at 0 degrees for 48 h. I.r. spectra of the products show a major band near 1750 cm-1, consistent with ester formation; this band virtually disappears after mild, alkali treatment. Esterification also occurs by incubating the native polysaccharides below pH 6.0, and their i.r. spectra show that the degree of esterification increases as the pH is lowered. The relatively low molecular weight of these partially esterified, water-soluble polymers is consistent with intra- rather than inter-molecular ester formation. Counter-current immunoelectrophoresis shows that esterification of approximately 9% is sufficient to abolish immunoprecipitation. 13C-N.m.r. spectroscopy of fully esterified colominic acid provides strong evidence for cross-linking between the carboxyl group of one residue and HO-9 of an adjoining residue. Meningococcal serogroup C polysaccharide, a (2 leads to 9)-alpha-linked homopolymer of sialic acid containing O-acetyl groups at C-7 and/or C-8, does not undergo intramolecular esterification after carbodiimide treatment. However, upon O-deacetylation of the polysaccharide, esterification occurs.

Escherichia coli↗
PubMed1981

Induction and persistence of B-cell tolerance to the thymus-dependent component of the alpha(1 leads to 6) glucosyl determinant of dextran. Recovery induced by treatment with dextranase in vivo.

A direct comparison was made between thymus-dependent (TD) and thymus-independent (TI) responses in mice tolerized for (1 leads to 6) glycosyl determinants by the injection of dextran B512. Long-lasting B-cell tolerance by dextran was reversed when mice were treated with dextranase in vivo. Complete or partial reversion of tolerance with the enzyme was invariably obtained for the TI response but the TD component proved to be more resistant and dependent on the immunogen used to test the reversion. The uniformity of the spectrotype in BALB/c mice, even under conditions of partial tolerance, permitted the analysis by isoelectric focussing of serum from tolerant mice treated with dextranase and immunized with TD dextran-ovalbumin. Results showed that, with one single exception, mice thus treated produced spectrotypes no different from the pattern normally found in immune animals. The results presented suggest that at least some alpha(1 leads to 6) specific B cells, both TD and TI, persist in tolerized mice for at least 2 weeks after tolerance induction and they do not support the concept of clonal elimination for either TI or TD responses in adult mice.

Animals↗
PubMed1979

Characteristics of the T-dependent alpha(1 leads to 6) glucosyl (dextran) antibody response induced in mice with isomaltohexaose coupled to chicken gamma-globulin.

Isomaltohexaose flavazole coupled to chicken gamma-globulin (IM6-CGG) induced T cell-dependent anti-alpha(1 leads to 6) dextran-specific IgM and IgG responses in CBA, BALB/c and A strain mice. The IgG responses were of restricted heterogeneity as judged by isoelectric focusing, and belonged mostly to the IgG1 subclass with a minor IgG3 component in the case of BALB/c and CBA mice. All four subclasses of IgG were produced in A strain mice. In contrast, native dextran B 512 induces exclusively T cell-independent IgM responses of the same specificity for all 3 strains. All BALB/c mice immunized with different doses of IM6-CGG either in Freund's adjuvant or with Al(OH)3 plus Bordetella pertussis showed the same spectrotypes by isoelectric focusing. Sera obtained at different times after immunization of BALB/c mice failed to show spectrotype variations. Late, but not early, bleedings from CBA mice showed a tendency towards more uniform isoelectric focusing patterns.

Animals↗
PubMed1979

Characterisation of the reaginic response to sulphonamides in mice.

Reaginic responses were induced in immunised mice with either 4-sulphanilamidobenzoic acid (4-SABA) or sulphamethoxazole (SMX) coupled to chicken gamma-globulin (CGG). The former was coupled through the carboxylic group of benzoic acid and the latter through the diazo derivative of the sulphanilamide group. The specificity of the reaginic responses obtained was assessed in each case by inhibition of passive cutaneous anaphylaxis in the rat. Immunisation with 4-SABA-CGG resulted in antibodies which recognised the sulphanilamide group as immunodominant and, therefore, they cross-reacted strongly with other sulphonamides. In contrast, SMX-CGG-induced IgE antibodies directed primarily to the methoxazole end of the molecule and cross-reactivity with other sulphonamides could not be demonstrated. This model may be useful for a more comprehensive study of allergic reactions induced by sulphonamides.

Animals↗
PubMed1979

The use of hapten-polysaccharide conjugates for the induction of B-cell tolerance involving IgE responses. II. Specific tolerance induced by sulphonamide-substituted levan in the mouse.

Normal and sulphonamide-sensitised mice were made tolerant with 4-sulphanilamido-benzoic-diaminopropyl-carboxymethyl-levan (4-SABA-Le). The tolerance was demonstrably specific for the sulphanilamide moiety of the hapten and extended to related compounds sharing this determinant. Mice sensitised with a 4-SABA-chicken gamma-globulin conjugate developed fatal anaphylactic shock after the injection of sulphanilamide or 4-SABA-ovalbumin, whereas allergic mice subsequently tolerised with 4-SABA-Le did not. The tolerance induced was long lasting since mice were still tolerant 7 months after an injection of an optimal dose of tolerogen. Suppressor cells play little or no part in the maintenance of this unresponsive state since even a 10-fold excess of splenic cells from tolerant animals failed to inhibit the responsivenss of 4-SABA-primed cells when they were transferred together into irradiated recipients.

Animals↗
PubMed1979

The use of hapten-polysaccharide conjugates for the induction of B-cell tolerance involving IgE responses. III. Specific tolerance induced by sulphonamide-substituted levan in the guinea pig.

Inbred strain 2 and (strain 2 x strain 13)F1 guinea pigs were made allergic by intraperitoneal injections of sulphonamide-chicken gamma-globulin (CGG) conjugates. Two sulphonamides were used: 4-sulphanilamide benzoic acid (4-SABA) and sulphamethoxazole (SMX). 4-SABA was coupled to CGG through its carboxylic group and SMX was coupled following diazotization of its sulphanilamide group. The anti-4-SABA and anti-SMX reaginic antibodies formed did not show any cross-reactivity with each other. Injection of 4-SABA coupled to native levan effectively suppressed the allergic responses of these guinea pigs when given either prior to or after immunization with 4-SABA-CGG. This treatment is specific as it did not affect anti-SMX or anti-CGG reaginic responses. Guinea pigs seem more sensitive to the regime used for tolerance induction than correspondingly sensitized mice in that less tolerogen is required on a body weight basis.

Animals↗