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S Bernard

Publications and source records attributed to S Bernard.

212 records · Page 12Linked to original sources
PubMedDate not supplied

Cytidine-5'-diphospho-choline conjugates. I.--Synthesis and fixation to phosphorylcholine-binding proteins.

The oxidation of the ribose ring of cytidine-5'-diphospho-choline (CDPC) by periodate to produce reactive dialdehydes was used to couple this activated reagent onto various proteins, onto Ficoll 400 and onto Sepharose 4B. Careful control of parameters of the different steps of the reaction enabled us to synthesize conjugates with a graded number of nucleotide residues. Human serum albumin conjugates with a relatively high degree of substitution were used to demonstrate and to measure anti-phosphorylcholine antibodies and the acute phase reactant, C-reactive protein by precipitation or passive haemagglutination techniques. These methods for measuring C-reactive protein in serum of patient suffering from acute inflammation may be useful for clinicians. CDPC-AH Sepharose was used to purify the phosphorylcholine-binding myeloma protein HOPC8 and to separate C-reactive protein from the bulk of serum proteins. Improvements of this technique will certainly lead to the complete purification of C-reactive protein.

Animals↗
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Cytidine-5'-diphospho-choline conjugates. II.--Immunogenicity in rats.

Cytidine diphospho-choline (CDPC) derivatives of human serum albumin (HSA) are immunogenic in the rat when injected in adjuvants. They induce a very rapid synthesis of IgM anti-phosphorylcholine antibodies which was followed by the synthesis of anti-CDPC antibodies and of anti-HSA antibodies. The activated nucleotide was able to induce specific skin sensitivity in rats after one skin painting. Gastric intubations of rats with low doses of HSA conjugates 8 days before an infection with the nematode Nippostrongylus brasiliensis were followed by a reduction of the resulting intestinal worm burden.

Animals↗
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[Isolation and characterization of an evolutionary precursor of human monoamine oxidases A and B].

An interesting flavoprotein-type monoamine oxidase (MAO) was recently isolated from Aspergillus niger and cloned by Schilling and Lerch (1995a,b) The properties of this MAO, as well as a substantial part of its amino acid sequence resemble those of both MAO A and B from higher animals, raising the possibility that it may be an evolutionary precursor of these mitochondrial enzymes. It differs from MAO A and B in several respect, however, including the fact that it is soluble and of peroxisomal localization and that the FAD is non-covalently attached. We have overexpressed the fungal enzyme (MAO-N) in Escherichia coli, isolated it for the first time in pure form, and, in collaboration with Dr. Elena Sablin, crystallized it. Since several of the observations of previous workers on MAO-N could not be reproduced and seem to be erroneous, we have reexamined its, substrate specificity, interaction with reversible and irreversible inhibitors and other catalytic and molecular properties. MAO-N has a considerably higher turnover number on many aliphatic and aromatic amines than either form of the mammalian enzyme. Some aspects of the substrate specificity resemble those of MAO B, while others are similar to MAO A, including biphasic kinetics in double reciprocal plots. Contrary to the report of Schilling and Lerch (1995a), however, the fungal enzyme does not oxidize serotonin, norepinephrine, dopamine or other biogenic amines. MAO-N is irreversibly inhibited by stoichiometric amounts of both (-)deprenyl and clorgyline in a mechanism-based reaction, forming flavocyanine adducts with N(5) of the FAD, like the mammalian enzymes, but inactivation is much faster with clorgyline than deprenyl, suggesting again a closer resemblance to MAO A than B. The dissociation constants for a large number of reversible competitive inhibitors have been determined for MAO-N and comparison with similar values for MAO A and B again pointed to a much greater similarity to the former than the latter. Experiments designed to change the linkage of the FAD to covalent form by site-directed mutagenesis and to dissociate.

Amino Acid Sequence↗
PubMedDate not supplied

Phosphorylcholine antigens from Nippostrongylus brasiliensis. II.--Isolation and partial characterization of phosphorylcholine antigens from adult worm.

The phosphorylcholine antigens (C substance) were specifically isolated from Nippostrongglus brasiliensis adult worms. They formed a gorup of fairly closely related molecules, but it was not possible to evidence that the carrier molecule was unique. An indirect immunoenzymatic test using immobilized lectins (concanavalin A, phytohaemagglutinin Els, wheat germ agglutinin, recin types I and II, peanut agglutinin) gave some light on the carbohydrate composition of the carrier molecules, whereas the amino acid part of these molecules seemed to indicate an unique oligopeptide, the composition of which would be: Asx (4), Thr (2), Ser (4), Glux (6), Gly (6) Ala (3), Val (2), Ile (1), Leu (2), Phe (8), Lys (2), Arg (1). An epitope of the carrier molecules was demonstrated with anti-N. brasiliensis egg antisera. It was shared with various pathogens including Haemonchus contortus, Schistosoma mansoni and Dipetalonema vitae. It was also found on the purified pneumococcal C. polysaccharide. The C. substance from a variety of parasites can now be isolated by a combination of specific reactions using both anti-phosphorylcholine and anti-carrier molecule antibodies.

Amino Acids↗