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Biomedical subjects

D Poulain

Publications and source records attributed to D Poulain.

At least 91 records · Page 5Linked to original sources
PubMed1983

Antigenic variations of Candida albicans in vivo and in vitro--relationships between P antigens and serotypes.

Serum samples from patients with candidosis and from rabbits experimentally infected with serotype B C. albicans strains consistently showed higher antibody titers against Candida strains with serotype A antigens than strains with serotype B antigens, in indirect fluorescent antibody tests. When sera from rabbits infected with C. albicans serotype B strains were absorbed with blastospores of the homologous strain they continued to react against strains of C. albicans serotype A and a C. tropicalis strain with serotype A antigens. Serotype A-specific antisera reacted against tissue forms of C. albicans serotype B in vivo and against serotype B germ tubes, but not their parent blastospores, in vitro. These findings suggest that C. albicans B serotype cells may sometimes express, in vitro or in vivo, one or several antigens so far considered as specific of serotype A. The results have implications for the classical concept of C. albicans serotypes and for the serological diagnosis of candidosis in relation with the previously described strain P variable antigens.

Agglutination Tests↗
PubMed1982

Antigenic variability between Candida albicans blastospores isolated from healthy subjects and patients with Candida infection.

Blastospores of 10 strains of C. albicans isolated from patients were compared with 10 strains from healthy subjects for their ability to detect antibodies by indirect immunofluorescence, with sera from the same patients and healthy subjects. Strains from patients were significantly more reactive with sera from patients than were strains from healthy individuals, but both groups of strains were equally reactive with sera from healthy subjects. These preliminary results indicate that the antigenic structure of C. albicans is not stable: there may be blastospore antigens that are qualitatively or quantitatively variable with the pathogenic behaviour of strains in vivo.

Antibodies, Fungal↗
PubMed1981

Localization of chitin in the cell wall of Candida albicans by means of wheat germ agglutinin. Fluorescence and ultrastructural studies.

Cytochemical localization of wheat germ agglutinin binding sites in the cell wall of Candida albicans was investigated with fluorescence and electron microscopy. Various analytical techniques were employed in order to obtain a good penetration of the cytochemical markers, glycosylated horseradish peroxidase or glycosylated ferritin. In blastospores sectioned by cryostatic methods, a weak and continuous labelling of the blastospore periphery was observed with peroxidase, whereas bud scars and inner cell wall areas were labelled with ferritin. Following enzymatic treatment with pronase whose efficiency was followed by the periodic acid-thiocarbohydrazide -- Silver proteinate technique, the inner cell wall layers of bud are strongly stained with both fluorescein and the reactions products of peroxidase. After pronase-chitinase treatment, fluorescence was observed only in the mother cell wall. Finally, ultrathin glycol methacrylate sections showed a labelling both in inner and outer layers. All these results suggest that chitin was essentially distributed in the inner wall layers near the plasmalemma and in a smaller amount in outer wall layers. On the basis of the present findings, a hypothesis of wall assembly is proposed.

Binding Sites↗
PubMed1980

Experimental study of resistance to infection by Trichophyton mentagrophytes: demonstration of memory skin cells.

The mechanisms governing the development of local immunity in experimental dermatophytosis were studied by injecting intravenously trichophytin in guinea pigs cured of a prior Trichophyton mentagrophytes infestation. Dermal cell modifications were observed which were greater in the healed zones than in those not affected during the prior dermatophyte inoculation. These modifications included lymphocyte activation and accumulation and an accumulation of basophilic leukocytes. These observations suggest that after an acute dermatophyte infection heals, immunocompetent cells remain which are more numerous at the sites of lesions and that these cells would be responsible for the increased rate of elimination of the fungus during a reinfection. This hypothesis is discussed in the framework of the relationships observed in dermatophyte infections between delayed type hypersensitivity and resistance.

Animals↗
PubMed1979

[Cytochemical and ultrastructural studies of the cell wall of Candida albicans (author's transl)].

The ultrastructural localization of polysaccharides in the cell wall of Candida albicans was carried out by means of Concanavalin A on glycol methacrylate ultrathin sections. The sections were incubated successively with horseradish peroxydase, 3-3' diaminobenzidine and H2O2, for revealing the binding sites of the lectin. This method allowed us to localize mannan, since Concanavalin A does not react with other polysaccharides of the C. albicans cell wall. In these conditions mannan was found to be located in two continuous reactive layers at the periphery of blastospores cell wall. The results are discussed in relation with those obtained by another method using the polysaccharide detection technique described by Thiery (PATAg).

Candida albicans↗
PubMed1976

Effects of estrogen on the electrical activity of identified and unidentified hypothalamic units.

Experiments performed on unanesthetized ovariectomized female rabbits demonstrated the effects of estradiol benzoate (EB; 20 microng i.v.) on the electrical activity of hypothalamic units which send their axons to the median eminence. Of a total of 1,840 cells recorded in hypothalamic and preoptic areas, 46 (2.5%) were antidromically activated by stimulating the median eminence. Under the present experimental conditions, EB induced a progressive diminution in the mean firing rate of these cells observed throughout the recording period (30-120 min). In addition to cells projecting to the median eminence, neurons which could not be antidromically invaded using our techniques were observed to be sensitive to estrogen. Estrogen administration produced a long-lasting inhibition of antidromically activated cells and a depression of much shorter duration (15-20 min) of unidentified nonstimulated units. These data suggest the existence of two types of hypothalamic neurons sensitive to estrogen.

Animals↗
PubMed1975

[The mycelial wall of Trichophyton mentagrophytes; ultrastructural study of its constitutive layers following the use of a method to demonstrate polysaccharides].

The ultrastructure of T. mentagrophytes hyphal walls was studied after the use of a cytochemical reaction for polysaccharides. The sections showed a wall composed of 3 layers viz: an external, poorly reactive one with a microfibrillary structure; a medium, fairly reactive one, with a periodic structure and an internal, intensivly stained layer, not observed in old cells. Other observations suggested that the septal medium layer should be differentiated from those cited above. The results are compared with previous data and a synthetic scheme of the Trichophyton mentagrophytes hyphal wall is proposed.

Cell Wall↗
PubMedDate not supplied

[Cytologic analysis of the expression of an epitope carried by glycoproteins excreted by Candida albicans].

The present study concerns an epitope identified by a monoclonal IgM, named 5B2, generated against the parasitic phase of Candida albicans. The epitope was previously shown to be carried by excreted C. albicans glycoproteins and to be present in the sera of patients suffering from systemic candidiasis. The cytological analysis of the epitope expression was investigated in 3 different yeast strains: the C. albicans strain from which 5B2 was generated (VW.32); a C. albicans mutant, deficient in cell wall mannans (KD.102); and a Saccharomyces cerevisiae strain. Immunofluorescence assays using IgM-5B2 showed discontinuous labelling with the VW.32 strain and no labelling with the 2 other yeast strains; however, the superficial structures of the 3 strains reacted homogeneously with ConA. Ultrastructural immunodetection experiments performed with the VW.32 cells, using gold-conjugated monoclonal antibody, revealed the presence of the epitope in the vacuolo-vesicular system, the periphery of the cytoplasm, the periplasmic space and the cell wall. Under the same conditions, cells from the KD.102 strain only exhibited weak cytoplasmic labelling whereas the presence of the epitope in S. cerevisiae blastoconidia was restricted to the vesicles. Competition and double labelling experiments with IgM and ConA showed that the epitope, distributed on the great majority of VW.32 glycoproteins, is shared by a lesser proportion of the KD.102 glycoproteins and only by some vesicular glycoproteins of S. cerevisiae. Inhibition of the N-glycosylation process of the VW.32 strain by tunicamycin resulted in the absence of cytokinesis and germ tube formation. In such cells, epitope 5B2 was no longer expressed on the bud surface. These cytological results concerning the C. albicans epitope are discussed in relation to recent, more general biochemical data on the yeast glycosylation process.

Antibodies, Monoclonal↗
PubMedDate not supplied

[Changes in the cell wall of Candida albicans cultivated in the presence of sublethal doses of nystatin].

Subinhibitory doses of nystatin in the culture medium of Candida albicans gave yeasts with altered cell walls. Major alterations chiefly concerned the antigenic peptidomannans. Their amount in wall and their molecular weight were smaller in yeast grown with nystatin than in normal cultured yeast. Glucans and chitin were not seriously modified. Polymers requiring lipidic intermediates such as dolichol phosphate for their biosynthesis seemed to be most affected by the presence of nystatin.

Amino Acids↗
PubMedDate not supplied

Kinetic study of antifungal activity of amphotericin B, 5-fluorocytosine and ketoconazole against clinical yeast isolates using liquid-phase turbidimetry.

The fungal growth of clinical yeast isolates and of VW32 clone of Candida albicans were measured in vitro using a liquid-phase turbidimetric system (Bioscreen from Labsystems, France) in defined conditions. Cultures were performed in Shadomy's liquid medium and the fungal growth automatically evaluated every 10 minutes for 24 hours using various concentrations of drugs. The system made it possible to test 200 culture samples in one experiment. Yeast sensitivity to drugs was also measured by using our routine semi-automatic turbidimetric system. We observed that kinetic patterns of activity of each antifungal agent were typical. The in vitro tests showed that of 927 clinical yeast isolates 99.2% were sensitive to amphotericin B, 94.4% to 5-fluorocytosine and 69.7% to ketoconazole.

Amphotericin B↗