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Biomedical subjects

R A Calderone

Publications and source records attributed to R A Calderone.

46 records · Page 3Linked to original sources
PubMed1978

Chitin synthesis in Candida albicans: comparison of yeast and hyphal forms.

Chitin synthesis was studied in both yeast and hyphae of the dimorphic fungus Candida albicans. Incorporation of N-acetyl-d-[1-(3)H]glucosamine ([(3)H]GluNAc) into an acid-alkali-insoluble fraction was 10 times greater in hyphal-phase cells. A crude preparation of chitin synthetase was obtained from sonically treated protoplasts of both forms of Candida. Enzyme activity, which was determined by using [(14)C]UDP-GLuNAc as a substrate, was exclusively associated with the 80,000 x g pellet from sonically treated protoplasts of both forms. It was determined that enzyme activity (nanomoles of [(14)C]UDP-GluNAc incorporated per milligram of protein) was approximately 2 times greater in hyphae versus yeast cells. Enzyme activity in both yeast and hyphae increased six- to sevenfold when the enzyme preparations were preincubated with trypsin. A vacuolar fraction, obtained from yeast cells but not from hyphae, stimulated enzyme activity when incubated with either yeast or hyphal enzyme preparations. Membrane fractions from protoplasts coated with [(3)H]concanavalin A before disruption were isolated by Renografin density gradient centrifugation. Chitin synthetase activity was preferentially associated with the concanavalin A-labeled fraction, suggesting that the enzyme was located on the plasma membrane. In addition, enzyme activity in protoplasts treated with cold glutaraldehyde before disruption was significantly greater than in protoplasts that were sonically disrupted and then treated with cold glutaraldehyde, indicating that the enzyme resides on the inner side of the plasma membrane.

Candida albicans↗
PubMed1977

Growth inhibition of Candida albicans by rabbit alveolar macrophages.

Normal rabbit alveolar macrophages were infected in vitro with Candida albicans. Early after infection, germ tube formation of phagocytized C. albicans was inhibited in contrast to extracellular (nonphagocytized) C. albicans. Over and 8-h period, plate counts of C. albicans incubated with alveolar macrophages revealed a decrease in colony-forming units in contrast to C. albicans alone. In addition, an assay was developed which specifically measured C. albicans [3H]leucine incorporation in the presence of alveolar macrophages. Using this assay, we observed a 71 to 93% inhibition of macromolecular synthesis in C. albicans when incubated with alveolar macrophages. Autoradiographic studies showed that the inhibition of leucine incorporation was restricted to the ingested Candida.

Animals↗
PubMed1977

Experimental Candida albicans endocarditis: characterization of the disease and response to therapy.

Endocarditis caused by Candida albicans was induced in rabbits after insertion of a catheter across the aortic valve. The mean survival time of 34 rabbits was 26 days. Only 7% of temperature recordings taken were elevated. Candida was recovered from only 9% of blood cultures taken. Precipitating and agglutinating serum antibody was detected after 12 days of infection. Antibody titers rose progressively until death in rabbits with endocarditis, whereas titers peaked early and subsequently decreased in animals that received an intravenous injection of C. albicans without precatheterization. Three groups of rabbits were treated for 6 days with amphotericin B, 5-fluorocytosine, or the two durgs in combination. Amphotericin B alone reduced the mean titer of organisms from log10 8.79 +/- 1.46 to log 10 3.1 +/- 1.9 colony-forming units/g. 5-Fluorocytosine was less effective (mean titer after 6 days of therapy was log10 7.4 +/- 0.33 colony-forming units/g). The addition of 5-fluorocytosine to amphotericin B did not increase the rate at which Candida cells were eradicated from the vegetations. These in vivo results corrleated with the failure to demonstrate an increased rate of fungicidal activity in vitro with the two drugs.

Agglutinins↗
PubMed1976

Effect of antibodies on the respiration and morphology of Candida Albicans.

Respirometry was used to study the effect of antibodies to Candida albicans on the gowth of this species in vitro. Blastospore suspensions were pre-incubated with rabbit hyperimmune and normal serum and rabbit antibody and normal gamma globulin at 37 degrees C for 30 minutes. They were then inoculated into respirometer flasks containing a semi-synthetic medium and oxygen consumption was measured at 27 degrees C. Rabbit antiserum to C. albicans serotype A inhibited the growth, as measured by O2 consumption, of serotyped A and B strains of C. albicans. The amount of inhibition appeared to be related to the prevention or retardation of germ tube formation. The growth of blastospores incubated with normal rabbit serum was filamentous, whereas, blastospores incubated with antiserum remained in the yeast phase. Inhibition of O2 consumption and retardation of germ tube formation was also demonstrated with the purified gamma-globulin fraction of the antiserum.

Animals↗
PubMed1976

An ultrastructural analysis of protoplast-spheroplast induction in Cryptococcus neoformans.

Protoplasts-spheroplasts of a human isolate of Cryptococcus neoformans were prepared using the gut enzyme of Helix pomatia. The induction process, as studied by transmission electron microscopy, occurred in two stages. Early in the induction process, protoplasts-spheroplasts emerged from whole cells through a break in the cell wall-capsule envelope. Later, a gradual dissolution of the entire cell wall occurred releasing the intact protoplast-spheroplast. A comparison of protoplasts-spheroplasts with normal untreated cells revealed that the degree of cellular vacuolation as well as the resolution of cellular organelles was similar.

Cell Wall↗
PubMedDate not supplied

Expression of the complement-binding protein (MP60) of Candida albicans in experimental vaginitis.

The expression of the Candida albicans complement-binding C3d protein (MP60) was investigated both in vitro and in vivo by immunogold labelling and electron microscopy. In vivo expression was determined in a rat vaginitis model. Reactivity of in vitro-grown cells to an anti-MP60 rabbit serum was associated with both cytoplasmic and cell wall sites. Immunostaining in the cell wall of both yeast and hyphae was most concentrated in the inner, electron-lucid layer. Immunogold stained preparations of C. albicans from vaginal smears of infected animals also showed intense localization of the MP60 in the inner cell wall, plasma membrane. However, immunogold label was also intense at the cell surface in these samples, mostly in the area of close adherence with the keratinocytes of the vaginal epithelia. These observations indicate that MP60 is expressed both in vitro and in vivo, but to a different degree in the different cell wall layers.

Animals↗
PubMedDate not supplied

Characterization of mannoproteins from a virulent Candida albicans strain and its derived, avirulent strain.

Antigenic differences between a wild-type virulent strain of Candida albicans 4918 (wt) and its spontaneous avirulent mutant (m-10) were found with crossed-immunoelectrophoresis and western blotting. Mannoprotein fractions from yeast and mycelial forms were obtained by affinity chromatography on concanavalin A and analyzed with use of patient sera or sera from rabbits infected with live wt cells and boosted with whole extracts or rabbits immunized with purified wt cell wall preparations. A spike-formed precipitate was detected only with the wt yeast cells with crossed-electrophoresis and patient and rabbit sera. Otherwise serum from infected rabbits precipitated about equally the wt and m-10 cell wall mannoprotein antigens. The nature of this precipitate, with extremely slow electromobility in the first dimension and the possibility of its relation to some special immunodeterminant of the wt mannan molecule, is discussed. Likewise, when mycelial mannoproteins were analyzed by crossed-immunoelectrophoresis, a precipitate specific for wt cells was observed with rabbit anti-Candida sera. Also, a mannoprotein of approximately 47 kilodaltons was observed by western blotting only for wt mycelial cells. The observed antigenic differences between the virulent and the avirulent derived strain might be related to the greater adherence and infectivity of the wt strain.

Animals↗
PubMedDate not supplied

Adherence of Candida species to host tissues and plastic surfaces.

Adherence of Candida species to host tissues and nonbiologic materials has been studied in vivo and in vitro. Attachment of Candida albicans to mucosal cells, fibrin-platelet matrices, vascular endothelial cells, and plastic materials has been examined to elucidate early events in the pathogenesis of mucosal colonization and infection, candidal endocarditis, tissue invasion from the intravascular space, and infection of prosthetic devices. Adherence of C. albicans and Candida tropicalis exceeds that of less virulent Candida species, and germinated C. albicans cells adhere to host tissues more readily than do yeast-phase organisms. The adhesin of Candida that mediates attachment has yet to be characterized at the molecular level; however, on the basis of competitive inhibition by crude and purified cell wall products, blocking by antibody and lectin, and controlled degradation of the cell surface of Candida, it appears that mannans and mannoproteins are important constituents of the adhesin. The methods currently used to assay adherence of Candida all have limitations, and an approach to resolving these limitations is one of several areas that warrant further investigation.

Animals↗
PubMedDate not supplied

Role of fibronectin in the pathogenesis of candidal infections.

Adherence of Candida albicans yeast cells to mammalian cells in vitro is promoted by a cell-surface adhesin that is probably a mannan or a mannoprotein. This observation is based on results of studies that utilized either lectins or antibodies to Candida that block attachment. Selective enzymatic degradation of cell wall constituents has been used to define the surface ligand of the candidal cell. Recently, nonadhering, spontaneous mutants of C. albicans, from both yeast and mycelial forms, that lack specific mannoproteins have been described. In addition, such mutants are avirulent, an indication that attachment plays a role in the disease process. The mammalian receptor for Candida has not been identified, but in endocarditis it could be fibronectin, both because fibronectin is present at the endocardial lesion and because those Candida species that bind to fibronectin in vitro exhibit a high disease potential; i.e., Candida species that bind to fibronectin in vitro also cause endocarditis, while those that do not bind in vitro do not cause disease. Attachment of yeast cells both to human buccal and vaginal epithelial cells is reduced significantly if yeast cells are preincubated with fibronectin, a finding that indicates a possible role for fibronectin as the epithelial surface receptor for Candida.

Candida albicans↗