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Biomedical subjects

M Fontaine

Publications and source records attributed to M Fontaine.

At least 91 records · Page 5Linked to original sources
PubMed1989

Truncated forms of human complement factor H.

By the use of Western-blot analyses with polyclonal anti-(Factor H) antibodies, two low-Mr protein species of Mr 41,000 and 37,000 under non-reducing conditions and 43,000 and 40,000 under reducing conditions are consistently detected together with the well-known 155,000-Mr Factor H in human plasma and serum. These two additional species are also found in plasma, urine and synovial fluids. The 41,000-Mr species but not the 37,00-Mr species is detected by a monoclonal anti-(Factor H) antibody directed at the N-terminal part of Factor H. The 37,000-Mr species but not the 41,000-Mr species is detected by a monoclonal anti-(Factor H) antibody directed at the C-terminal part of Factor H. The 41,000-Mr and 37,000-Mr species are different from the well-characterized 36,000-Mr N-terminal tryptic fragment of Factor H. They are likely to represent translational products of the short Factor H mRNA species of 1.8 kb and 1.2-1.5 kb occurring in human liver that we have recently described.

Antibodies, Monoclonal↗
PubMed1989

Biochemical contribution to diagnosis and study of a new case of D-glyceric acidemia/aciduria.

During organic acid screening by gas chromatography/mass spectrometry, we detected a large peak corresponding to glyceric acid in a patient's urine sample. The D(+) configuration was demonstrated by a polarimetric method and by enzymatic stereospecificity of D-glycerate dehydrogenase (EC 1.1.1.29). We biochemically investigated this fifth reported case of D-glyceric acidemia. In our patient, loading tests with L-serine and fructose led to an increase of D-glyceric acid in both plasma and urine. Determination of other metabolites involved in D-glycerate metabolism revealed no abnormality in any sample examined. After comparing all our results with those of the preceding observations described in the literature, we suggest a possible enzymatic defect located on one of the metabolic pathways shared by fructose and L-serine, possibly at the level of hepatic D-glycerate kinase (EC 2.7.1.31). Nevertheless, a primary defect of L-serine catabolism cannot be entirely excluded.

Chemical Phenomena↗
PubMed1989

[Endodontic anatomy of lower premolars--apropos of 669 cases].

Six hundred sixty nine human mandibular first and second premolars were collected (extracted) and studied. We made roentgenographic studies, sections of extracted teeth. Comparisons with the findings of other investigators were made in regard to the number of roots and number of root canals (in different tables).

Bicuspid↗
PubMed1988

Two populations of complement factor H differ in their ability to bind to cell surfaces.

Using hydrophobic affinity chromatography on phenyl-Sepharose, human complement factor H can be separated into two subpopulations, phi 1 and phi 2. Although phi 1 and phi 2 are known to differ in their aggregation properties under non-physiological low ionic strength conditions, no difference in aggregation state was detected under the conditions used for cell-binding experiments. We have investigated these two subpopulations further to determine whether functional differences exist between them. The subpopulation phi 2 was found to bind specifically and saturably to the surface of Raji cells. The binding of the other subpopulation, phi 1, was low, and essentially non-specific. A monoclonal anti-factor H antibody, BGH-1, was raised which recognizes preferentially the phi 2 subpopulation and inhibits the binding of factor H to cell surfaces.

Antibodies, Monoclonal↗
PubMed1988

Localization of a hydrophobic domain in human C5.

The fifth component of human complement (C5), under physiological salt conditions, bound firmly to phenyl-Sepharose. This indicated the presence of hydrophobic sites on C5. These sites may play an important role in C5 haemolytic activity since this activity was inhibited by chaotropic ions (Mg2+, SCN-, I-) at relatively low concns (0.6-1 M). Charge shift experiments performed on purified C5 provided further evidence for the presence of hydrophobic sites within C5. Bidirectional charge shifts of C5 mobility were observed with the two detergent systems TX-100 + DOC and TX-100 + CTAB. In order to localize these sites, C5 was subjected to trypsin digestion. Three major fragments were evidenced by two-dimensional electrophoresis (agarose/SDS-PAGE and SDS-PAGE/SDS-PAGE), and were isolated by hydrophobic affinity chromatography. The first fragment, C5FI, was composed probably of a mixture of six alpha chain fragments (alpha 1-alpha 6) linked to the beta chain by disulphide bridges. The second fragment, C5FII, was composed of the beta chain linked to two alpha chain fragments: alpha 2 (Mr = 58 K) and alpha 4 (Mr = 32 K). The third fragment, C5FIII, contained two covalently linked chains (beta chain and alpha 4). The rank order for mol. wt, agarose gel electrophoretic mobility and hydrophobicity was respectively: C5 greater than or equal to C5FI greater than C5FII greater than C5FIII; C5 less than or equal to C5FI less than or equal to C5FII much less than C5FIII; and C5FII greater than or equal to C5 greater than C5FI much greater than C5FIII. From the relative hydrophobicity, the hydrophobic sites of C5 can be localized to the alpha 2 fragment (Mr = 58 K) since C5FIII lacked the alpha 2 fragment and was not hydrophobic. Cleavage and the liberation of the N-terminal part of C5 induced an increase in hydrophobicity of the remaining part of C5 (C5b and C5FII), suggesting a possible role of the hydrophobic sites in association of C5b with membranes.

Complement C5↗
PubMed1988

Molecular basis for the microheterogeneity of human complement factor B.

The involvement of sialic acids in the microheterogeneity of human complement factor B was investigated. Desialylation kinetics revealed all the charge intermediates from a complex native to a homogeneous form. The relation between this heterogeneity and posttranslational events was explored in cultured hepatoma cells. Intracellular factor B exhibited the same isoelectric focusing pattern as the desialylated purified protein, whereas a highly heterogeneous form was secreted. In contrast, when N-glycosylation was prevented by tunicamycin, both intracellular and secreted forms focused like intracellular factor B from control cultures. These data lead to the conclusion that the microheterogeneity of human factor B results from different degrees of sialylation of its N-glycans.

Carcinoma, Hepatocellular↗
PubMed1988

[Surgical treatment of cancer of the left colon. True left hemicolectomy or segmental colectomy?].

Non-metastatic cancer of the left colon is still an exclusively surgical problem in 1988. The problem is to determine which type of colectomy should be performed: either a true left hemicolectomy, a long but apparently oncologically satisfactory operation, or segmental colectomy. A recent study by A.R.C. reported the same 5-year survival for these two types of operation with essentially identical postoperative mortality and morbidity. This conclusion confirms that of many studies published on this subject.

Actuarial Analysis↗
PubMed1987

Marmoset red blood cell receptor for membrane-associated complement components is not related to human CR1: partial characterization of the C3-binding proteins responsible for the spontaneous rosette formation between marmoset red blood cells and human leukocytes.

Cells from all the human B-lymphoblastoid cell lines tested and most human monocytes form rosettes with marmoset red blood cells (MaRBC). Because previous reports suggested the involvement of complement components in this phenomenon, the mechanism of rosette formation and the eventual similarities between the MaRBC receptor and the CR1 receptor present on human erythrocytes have been analyzed herein. The binding of MaRBC to human leukocytes strongly differs from the immune adherence phenomenon: rabbit anti-human CR1 did not react with MaRBC and the MaRBC receptor-binding activity is Ca2+-dependent. Rosette formation required intact energy metabolism and cytoskeleton integrity of leukocytes. Our attempts to purify the receptor from MaRBC membranes revealed the absence of CR1. Nevertheless, C3-binding proteins were isolated by selective desorption by Sepharose iC3 column chromatography. A three-band pattern was observed under reduced conditions with 74,000, 70,000, and 53,000 molecular weights. It was not possible to further separate these components. This protein complex inhibited the rosette phenomenon between MaRBC and both Raji and U-937 cells, exhibited a very poor cofactor activity, and had no decay-accelerating activity toward the classical C3 convertase. This material did not cross-react with antibodies directed to human proteins. These results showed that erythrocytes from new world monkeys do not express a receptor analogous to the human CR1, but expressed C3-binding protein with low cofactor activity that could recognize membrane-associated complement components.

Animals↗
PubMed1986

Biosynthesis of the third component of complement (C3) by the human monocytic-cell line U-937. Induction by phorbol myristate acetate.

Phorbol myristate acetate (PMA)-stimulated human monocyte-like cells (U-937) were found to synthesize the third component of complement (C3), as shown by enzyme-linked immunosorbent assay and immunoprecipitation from [35S]methionine-labelled culture supernatants. C3 synthesis occurred at a rate of about 160 ng of C3/24 h per 10(6) cells on day 7 after addition of PMA; it was blocked by cycloheximide treatment and was restored after removal of the inhibitor. SDS/polyacrylamide-gel-electrophoretic analysis of the immunoprecipitated protein showed that the size and subunit structure of the newly synthesized C3 were identical with those of plasma C3, and that a single-chain intracellular precursor was present in the cell lysates. Haemolytic assays showed that the synthesized C3 fully expressed functional activity in early culture within 4 h. After longer culture, a loss of haemolytic activity was observed. The possibility that newly secreted C3 is cleaved by U-937 cells themselves was suggested.

Cell Line↗
PubMed1986

Long-term biosynthesis of complement component C3 and alpha-1 acid glycoprotein by adult rat hepatocytes in a co-culture system with an epithelial liver cell-type.

We used a system of co-culture of adult rat hepatocytes with another epithelial cell type from rat liver to study the synthesis of two acute-phase reactants, alpha-1 acid glycoprotein (alpha 1AGP) and the third component of complement (C3), and we have obtained long-term secretion of these two proteins. After a period of adaptation corresponding to the first 2-4 days of the co-culture, hepatocytes secreted C3 and alpha 1AGP for at least 2 weeks at a mean level higher than that observed in the first days of a pure culture of hepatocytes. When pulse-chase analysis was performed on day 6 of co-culture, kinetics of synthesis of alpha 1AGP and C3 were the same as those observed on day 1 of a conventional culture of pure hepatocytes. Furthermore, intracellular and extracellular alpha 1AGP had Mr values respectively of 39,000 and of 42,000-52,000, identical with those observed in pure cultures of hepatocytes. Similarly, the molecular size and subunit structures of C3 were the same in co-culture and in cultures, indicating an identical processing of this protein. C3 produced in co-culture was also haemolytically active. Therefore, the system of adult hepatocytes co-cultured with this liver epithelial cell provides a physiological system in vitro which permits long-term synthesis of the two acute-phase reactants C3 and alpha 1AGP. This model opens the possibility to study the modulation of the synthesis of these two proteins during a long period by inflammatory agents or by hormones.

Animals↗
PubMed1986

Analysis of free porphyrins in biological samples by high performance liquid chromatography.

High performance liquid chromatography has been used to separate and analyse the different free porphyrins in biological materials. The selective determination of uroporphyrin, coproporphyrin, protoporphyrin and hepta, hexa, pentacarboxylic porphyrins, the sensitive and quantitative fluorescence detection contribute to the clinical diagnosis of porphyria.

Chromatography, High Pressure Liquid↗
PubMed1985

Modulation of complement receptors of a human monocyte cell line, U-937, during incubation with phorbol myristate acetate: expression of an iC3b-specific receptor (CR3).

The human monocyte line, U-937, derived from an individual with histiocytic lymphoma was studied for the expression of surface C3 receptors, after cultivation in the presence of phorbol myristate acetate (PMA) or T lymphocyte-conditioned medium. Receptors were detected by using EAC4b, EAC3b, EC3b, EAC3bi and EAC3d intermediates. U-937 cells, in exponential growth phase, poorly bound the intermediates; after exposure to PMA or T lymphocyte-conditioned medium, U-937 cells strongly bound both EAC3b and EAC3bi since about 50% of cells rosetted with these intermediates. This binding was totally inhibited by EDTA and by Mac-1 monoclonal antibody, suggesting the presence of only CR3 receptor types on these cells. Although U-937 cells formed rosettes with EAC3b, there was no evidence for the presence of CR1 receptors since no rosette was observed either with EAC4b or with EC3b intermediates (EC3b were prepared by coupling purified C3b to erythrocytes with N-succinimidyl 3-(2-pyridyldithio)propionate. As small amounts of factor H were present on EAC3b intermediates, incubation of EAC3b with U-937 cells induced their transformation into EAC3bi and their binding to CR3. Moreover, U-937 cells did not promote the cleavage of C3b in the presence of factor I alone, suggesting that these cells did not bear a sufficient amount of functionally active CR1. These results demonstrated that U-937 cells predominantly expressed CR3. The study of the kinetics of EAC3bi rosette formation demonstrated that CR3 expression is closely related to PMA activation. We suggest that CR3 activity could result from a phosphorylation of existing receptors.

Antibodies, Monoclonal↗
PubMed1985

Antigenic characterization of influenza A (H1N1) viruses recently isolated from pigs and turkeys in France.

The spread of influenza A viruses from one animal reservoir to another forms an important part of the epidemiological study of influenza. The precise characterization of viral antigens by monoclonal antibodies makes possible an interesting immunological approach to the transfer of strains from one reservoir to another.This work has shown that the recent porcine strains in France, Belgium, and Spain are closely related antigenically, and distinct from the A/sw/NJ/8/76 strain. Their prototype is strain A/sw/Fin/2899/82.An avian strain, A/ty/Brit/46/83, which has caused limited epidemics of reduced egg-laying among turkeys, has a haemagglutinin identical with that of strain A/sw/2899/82.This immunological finding, combined with epidemiological information (geographical location and absence of any influenza antibody in turkey farms in previous years), suggests that the transfer of influenza viruses has taken place in the direction from pig to turkey.

Animals↗