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R Bonaly

Publications and source records attributed to R Bonaly.

At least 37 records · Page 2Linked to original sources
PubMed1992

Membrane phospholipid composition in Saccharomyces uvarum cells grown in the presence of subinhibitory doses of amphotericin B and desertomycin.

In Saccharomyces uvarum cultures, subinhibitory doses of amphotericin B and desertomycin induced alterations in the plasma membrane phospholipid composition. Amphotericin B increased the lipid content in the plasma membrane. It showed a pronounced effect on fatty acyl constituents by raising the amounts of mono- and polyunsaturated derivatives in phospholipids. On the other hand, desertomycin had no apparent effect on fatty acid synthesis but altered the relative composition of phospholipids in the membrane. Phosphatidyl choline and phosphatidyl ethanolamine contents decreased, while their precursors, phosphatidyl serine and phosphatidic acid, increased. On the other hand, the rates of phosphatidyl inositol were not significantly affected by the action of either antifungal agent.

Amphotericin B↗
PubMed1991

Kluyveromyces bulgaricus yeast lectins. Isolation of two galactose-specific lectin forms from the yeast cell wall.

Incubation of galactose treated Kluyveromyces bulgaricus yeast cells in EDTA/phosphate-buffered saline led to an extract possessing hemagglutinating and yeast flocculating properties. Purification of this extract by affinity chromatography and gel filtration gave two lectin forms, Kb-CWL I and Kb-CWL II, with an apparent molecular mass of 38,000 and 150,000 Da, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that Kb-CWL I and Kb-CWL II were dimeric and octameric of a subunit of 18,900 Da. At high concentration, purified Kb-CWL I associated to give Kb-CWL II. This association seemed to be independent on pH. The two lectin forms were glycoproteins, the peptide counterpart was very rich in Lys, Glu, and Gly, and the carbohydrate part represented 1% of the whole molecule and was composed of Glc, Man, and Ara. The two lectin forms (KB-CWL I and Kb-CWL II) agglutinated human red blood cells and flocculated EDTA-treated K. bulgaricus yeast cells. The activity of both lectin forms required Ca2+ ions, while Sr2+ showed some competitive inhibition. Optimal activity was obtained within a pH range of 4-6.5 for both forms. Temperatures of 80-90 degrees C for 20 min, or proteolytic treatment reduced irreversibly the activity of Kb-CWL I and Kb-CWL II. The role of the cell wall phosphopeptidomannan as a ligand and a potential physiological receptor of these lectin forms was demonstrated.

Agglutination↗
PubMed1990

Acetolysis and 1H NMR studies on mannans isolated from very flocculent and weakly flocculent cells of Pichia pastoris IFP 206.

Growth of the yeast Pichia pastoris IFP 206 in methanol- and glucose-containing media led respectively to very and weakly flocculent cells. Mannans from both kinds of cells were extracted and compared. Chemical analysis and molecular mass estimation showed some differences between the mannans from very and weakly flocculent cells, especially in quantitative amino acid content. 1H NMR analysis showed that both kinds of mannan contained alpha-1,2 and beta-1,2 linkages. Two acetolysis conditions, combined with 1H NMR analysis, revealed that mannans from both kinds of cells were composed of mannose, mannobiose, mannotriose, mannotetraose and mannopentaose side-chains with the following respective structures: Man; Man alpha 1---2Man; Man alpha 1----2Man alpha 1----2Man; Man beta 1----2Man alpha 1----2Man; Man beta 1----2Man beta 1----2Man alpha 1----2Man; Man alpha 1----2Man beta 1----2Man beta 1----2Man alpha 1----2Man. Additionally the beta-1,2 linkages of the non-reducing terminal residues of the mannotetraose were shown to be acetolysis-labile. The mannans from very flocculent cells were richer in mannopentaose than the mannans from weakly flocculent cells. According to these results, the extended conformations in the branching moieties of the mannan could be the basis of the higher degree of flocculation of the methanol-grown cells.

Carbohydrate Conformation↗
PubMed1990

[The mode of action of a nonpolyenic antifungal (desertomycin) produced by a strain of Streptomyces spectabilis].

A metabolite with antifungal activity, of non polyenic macrolide structure, was extracted and purified from the culture supernatant of a soil-isolated Streptomyces spectabilis strain, BT 352. This product was found to be related to (or being) desertomycin. Six yeast and five filamentous fungus strains were used to determine minimum concentration of the metabolite that inhibits growth by 80% (IMC); it was established at 50 micrograms/mL for the fungi and at 100 micrograms/mL or more for the yeasts tested. Short-term genotoxicity tests showed no antifungal effect on the bacterial genome, and desertomycin at concentration levels of 100 micrograms/mL or more affected protein synthesis. The antifungal metabolite had no immediate inhibiting effect upon yeast respiration, even at high concentrations; however, the respiration activity of cells grown in the presence of subinhibiting doses and collected during their growth phase was reduced by as much as 40%. Saccharomyces uvarum spheroplast regeneration in a liquid medium containing desertomycin was inhibited at doses fivefold weaker than the IMC determined with intact cells. Contrary to amphotericin B, desertomycin subinhibiting doses do not modify, and if so lightly, the yeast latent phase or the spheroplast wall regeneration phase, thus indicating a fungicidal action. Moreover, following a 30-min contact with desertomycin subinhibiting and inhibiting doses, yeasts liberated potassium in large amounts, indicating that plasma membranes were affected.

Amphotericin B↗
PubMed1989

Effects of subinhibitory dose of amphotericin B on cell wall biosynthesis in Candida albicans.

Subinhibitory doses of amphotericin B in the culture medium of Candida albicans modified yeast cell wall synthesis. Analysis of isolated cell walls showed a decrease in mannose and an increase in amino acid and glucosamine levels. After fractionation of the cell wall by ethylenediamine or pronase digestion, study of the fractions corroborated an outer phosphopeptidomannan decrease and an enrichment of matrix constituents. Determination of the amount of chitin showed stimulation of synthesis of this amino polysaccharide in yeasts grown in the presence of amphotericin B. Decrease in phosphopeptidomannans and high production of other cell wall constituents are probably consequences of modification of the lipidic environment of membrane-bound enzymes by the antifungal polyene action.

Amphotericin B↗
PubMed1988

Kluyveromyces bulgaricus yeast lectins. Isolation of N-acetylglucosamine and galactose-specific lectins: their relation with flocculation.

Kluyveromyces bulgaricus is a yeast which, upon culture in a calcium-enriched glucose-peptone medium, flocculates. Its flocculation can be reversed by the addition of galactose. In this paper, it is shown that two lectins can be isolated either from the concentrated culture broth or from the supernatant of deflocculated cells suspended in galactose solution. The N-acetylglucosamine-specific lectin, at pH 7.4, agglutinates untreated sheep red blood cells, but agglutinates neither untreated rabbit red blood cells nor glutaraldehyde-fixed sheep or rabbit red blood cells. Conversely, at pH 4.5, this lectin agglutinates glutaraldehyde-fixed sheep red blood cells. The galactose-specific lectin, at pH 7.4, agglutinates both untreated and glutaraldehyde-fixed rabbit red blood cells but does not agglutinate untreated or glutaraldehyde-fixed sheep red blood cells. At pH 4.5, this lectin agglutinates both glutaraldehyde-fixed sheep and rabbit red blood cells and induces flocculation of deflocculated K. bulgaricus cells. In all cases, the agglutination and the flocculation induced by one of these two lectins were inhibited by free or conjugated N-acetyl-D-glucosamine or by free or conjugated D-galactose, respectively. No glycosylhydrolase activity could be detected in the purified lectins.

Acetylglucosamine↗
PubMed1988

[Variation of the sterols from Kluyveromyces lactis and from a resistant mutant by culture in the presence of sublethal doses of amphotericin B].

A mutant strain of Kluyveromyces lactis resistant to amphotericin B and weakly to nystatin has been isolated from subcultures of the wild strain grown in the presence of sublethal doses of amphotericin B. The mutant and the wild strain were equally sensitive to pimaricin, filipin, and candicidin. The efficacy of fungizone was very low. In comparison with the wild strain the level of sterols was two times lower in the resistant strain but the composition of these sterols was about the same in the two strains. The action of sublethal doses of amphotericin B on the composition of the sterols was the same in these two yeasts and brought a 40% decrease of the total sterol level and a modification in their distribution. This variation cannot fully explain the resistance of the yeast but it may be associated to other changes of the membranes.

Amphotericin B↗
PubMed1987

[Current role of amphotericin B in the treatment of deep mycoses].

Amphotericin B (Am. B), a polyene heptaene, is an antifungal antibiotic substance produced by Streptomyces nodosus, a telluric actinomycetal from Venezuela. Although it is a very toxic substance and its pharmacokinetic is not completely known, Am. B is yet the former antifungal substance utilised against number of pathogenic agents of systemic mycoses. Am. B binds irreversibly to sterols of fungal cytoplasmic membranes causing a leak of potassium and other impairments leading the fungal cell to death. Further, Am. B might to induce an enhancement of humoral and cellular immunity. After intravenous perfusion, 95 per cent of Am. B binds to plasma lipoproteins. Only a low proportion of the Am. B serum level is detected in the CSF. Distribution of Am. B to extravascular inflammatory fluids and secretions might be letter. Am. B might be eliminated essentially by biliary way. Am. B toxic effects are very frequent. Generalized reactions are observed to the earlier doses. Toxic visceral, above all, nephrotoxic manifestations, appearing later. Recent results, from experimental and human infections suggest that Am. B encapsulated in liposomal vesicles is more active, less toxic and more easily administered.

Adolescent↗
PubMed1986

[Effect of amphotericin B on the sterol composition of Kluyveromyces bulgaricus and Kluyveromyces lactis].

The degree of sensitivity of the yeasts Kluyveromyces bulgaricus and K. lactis to amphotericin B is linked to a difference in the sterol composition of their membranes. No direct proportionality was found between sensitivity and the quantity of sterols present. At sublethal doses, amphotericin B perturbed sterol synthesis, resulting in ergosterol precursor accumulation. An ergosterol pathway is proposed for Kluyveromyces.

Amphotericin B↗
PubMed1985

Chemical and antigenic alterations of Candida albicans cell walls related to the action of amphotericin B sub-inhibitory doses.

Sub-inhibitory doses of amphotericin B led to Candida albicans cell wall modifications which involved peptidomannans. The amount of this product was reduced by a third, the decrease being due to mannans whose absolute and relative values fell whereas the amount of amino-acids increased. Concomitantly, the treated cells exhibited a loss in their immunological reactivity.

Amino Acids↗
PubMed1981

[Characterization of cell wall constituents involved in the flocculation of Saccharomyces uvarum yeast strains].

Cell walls of flocculent strains (0006) and non flocculent strains (0019) of Saccharomyces uvarum (Carlsbergensis), grown in different media and taken in both growth and stationary phases, were treated with water and with 2 per cent (W/V) potassium hydroxide. This treatment yielded four fractions (FI, FII, FIII and FR). The fractions FI isolated from the flocculent cell walls contained more mannose and less protein than the corresponding fractions FI isolated from the non flocculent cell walls. The amino-acid composition was also different between the two types of fractions. A radioactive labelling technique revealed that the FI and the walls from flocculent cells bound on average two to three times as much 45Ca as did the FI and the walls from non flocculent yeast. The substitution of carboxyl groups in FI and walls with glycine methyl ester led to a great drop of the 45Ca binding capacity. This result suggests that carboxyl groups of the cell walls are involved in the flocculation process. But flocculation seems to be a phenomenon more complex than the simple formation of a Ca2+ bridge, the involvement of "lectin like" components easily removed from the cell walls, should not be rejected.

Amino Acids↗
PubMed1980

[Relationship between the spectral properties and antifungal properties of amphoterecin B and candicidine].

The antifungal activities of polyen macrolides Amphotericine B and Candicidine are investigated. The deep spectral changes of the absorption and of the circular dichroism show various states of micellar preparations which are: a) in aqueous medium, aggregats of different spectral characteristics, the antifungal activity of which being modulated by the preparation. b) aggregats of antifungal heptaen with membrane-sterol responsable of the antifongal activity. c) aggregats in hydrophobic solutions which spectroscopic properties are sterol-complex like. Our results suggest an explanation of the spectral changes and can point out some favorable characteristics for an optimal activity of these antifungals against yeasts.

Amphotericin B↗
PubMed1977

[Isolation and structure of an external glycoprotein of the cell wall of Torulopsis candida].

The treatment with ethylenediamine of Torulopsis candida yeast cell walls has permitted to isolate a mannoprotein. It has been possible to collect this glycoprotein in a pure state after separation of the different hydrosoluble products by gel filtrations and paper electrophoresis. This compound contains 62 per cent of mannose, 3 per cent of N-acetylglucosamine and 31 per cent of amino acids. The mannose units are attached by 1 leads to 2 linkage, short oligosaccharides are bound to serine of the peptide chain by O-glycosidic linkages while polysaccharides are attached to asparagine of this peptide chain by a N glycosidic linkages probably through the intermediate of chitobiose.

Amino Acids↗