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  • Candida albicans  (20)
  • 1990-1994  (20)
  • 1
    ISSN: 1573-0832
    Keywords: Candida albicans ; ammonium ; physiology ; medium ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Candida albicans strain B 311-10 with and without starvation was cultivated in the minimal synthetic medium of Shepherd et al. [18], modified without biotin, aminoacids, low glucose concentration [20] and with decreasing amounts of (NH4)2SO4, to determine the optimal growth requirement for this strain. All the experiments were carried out under sterile conditions at 25 °C in a thermostat with initial O.D.s (675 nm) of 0.500 and 0.100. Cell growth was generally monitored everyday for six days with a spectrophotometer by determining the absorbance of the cultures at 675 nm. All the experiments were repeated three times and a statistical analysis of the data with a probability of 99% and 1% of error was performed to confirm the validity of the results. Best growth was obtained with starved cells at an initial O.D. of 0.100 and with a 0.1 g/L concentration of (NH4)2SO4. At this concentration, the growth of C. albicans B 311-10 was best between the first and the fourth day with the maximum at the third day. With (NH4)2SO4 concentrations of 0.05 and 0.5 g/L, cell growth was the same.
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  • 2
    ISSN: 1573-0832
    Keywords: Candida albicans ; adenosine 3′5′-cyclic monophosphate ; cyclic AMP ; yeast-mycelium transition ; dimorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A yeast-mycelium (Y-M) transition in Candida albicans was induced by exogenous yeast extract, adenosine, adenosine 5′-monophosphate (AMP), adenosine 5′-diphosphate (ADP), adenosine 3′∶5′ cyclic monophosphate (cAMP) and its analogue N6, O2′-dibutyryl adenosine 3′∶5′-cyclic monophosphate (dbcAMP) in defined liquid medium at 25°C. Adenosine 5′-triphosphate (ATP) was found to delay germ tube formation in yeast cells, whereas the cAMP phosphodiesterase inhibitors, theophylline and caffeine, induced a Y-M transition. Intracellular and extracellular cyclic AMP levels increased during the yeast-mycelium transition and maximum levels of intracellular cyclic AMP coincided with maximum germ tube formation. Of the many inducers and inhibitors of germ tube and mycelium formation in C. albicans tested, including incubation at 37°C or in the presence of 1.5mM CaCl2, the calmodulin inhibitor calmidazolium (R24571) added together with CaCl2 induced the highest intra- and extracellular cyclic AMP levels. These results confirm the involvement of cyclic AMP in the yeast-mycelium transition of C. albicans.
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  • 3
    ISSN: 1573-0832
    Keywords: Antifungal azoles ; Antifungal drug antagonism ; Candida albicans ; Imidazoles ; Miconazole ; Triazoles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 110 (1990), S. 63-76 
    ISSN: 1573-0832
    Keywords: Caffeine ; Candida albicans ; mitotic recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Caffeine at concentrations of 0.5 × 10−2 M or higher inhibited cell replication and induced gene segregations in Candida albicans cultured on defined complete medium. Both responses increased incrementally with increasing caffeine concentrations, and were more severe during incubation at 37 °C than 25 °C; at 37 °C, caffeine levels above 1.5 × 10−2 M caused cellular inactivation. Caffeine effects occurred only under conditions permitting cell growth, and their magnitudes were greater for unbudded than budding cells, were influenced by cellular genetic backgrounds, and were unaffected by the presence of adenine in the medium. Evaluations of segregations for recessive auxotrophic markers of a four member linkage group carried heterozygously in a cis arrangement in treated cells established that induced segregants arise through either reciprocal or nonreciprocal recombinations. The frequency distributions of classes of reciprocal and nonreciprocal recombinants for these markers conformed with those previously obtained following induction by ultraviolet radiation, indicating that the probabilities of recombinational events within the chromosomal regions defined by the markers are not biased by the differences in kinds of initial DNA lesions caused by the two recombinagens. A panel of four protoplast fusion hybrids considered deficient for DNA repair because of enhanced susceptibilities to UV induced cellular inactivation and mitotic recombination exhibited corresponding increased sensitivities to caffeine, signifying that DNA damage induced by caffeine is subject to repair. Caffeine did not affect behavior of a variant strain exhibiting high frequency phenotypic switching between minute smooth and large rough colonial forms, and no evidence for mutagenicity of the drug was obtained with systems for detection of forward or reverse mutations. The mechanism of caffeine's recombinagenicity, and the implications of that property for genetic studies of C. albicans are discussed.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 116 (1991), S. 203-208 
    ISSN: 1573-0832
    Keywords: Candida albicans ; mycotoxin ; gliotoxin ; virulence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Candida infections are major causes of morbidity in compromised human hosts, but our understanding of the virulence of Candida remains incomplete. The possibility that toxic fungal metabolites belonging to the chemical class epipolythiodioxopiperzine (ETP), which are reported to possess immunomodulating and antiphagocytic properties may be produced by Candida species was investigated. Reversed phase HPLC analysis of flash evaporated chloroform extracts of 7 day cultures of clinical Candida isolates grown in Minimal Essential Medium (MEM) with 5% fetal calf serum revealed the presence of a compound which eluted at the same time as the ETP, gliotoxin. Of 50 strains of yeast tested, 32 produced this gliotoxin-like material. This material was tested for other properties of ETP type toxins including the presence of mercaptans (Ellman reaction), ultraviolet absorbance spectrum and antibacterial activity against Micrococcus lutea. These tests revealed gliotoxin-like material from yeast cultures to be similar to commercially supplied gliotoxin. This represents the first report of the presence of ETP-like compounds in yeast and raises the possibility that ETP's may contribute to the virulence of the organism.
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  • 6
    ISSN: 1573-0832
    Keywords: Ascending pyelonephritis ; Candida albicans ; Experimental model ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We developed a new experimental model of ascendingCandida pyelonephritis in female rats with leukopenia and vesicoureteral reflux. Rats were treated transperitoneally with cyclophosphamide (200 mg/kg) to induce leukopenia 3 days before and transurethrally with diluted acetic acid solution to induce vesicoureteral reflux 1 day before inoculation ofCandida albicans strain, ATCC 10259 (containing 107 cells). Microscopy revealed acute pyelonephritis in whichCandida cells invaded from the fornix and/or papilla into the medulla within 3 days after inoculation. Between 7 and 28 days after inoculation, chronic pyelonephritis reached the cortex. The incidence of pyelonephritis increased gradually and was approximately 80% after 7 days.Candida colony counts of bladder urine specimens obtained by direct puncture were significantly greater in rats with pyelonephritis extending into the parenchyma than in those with pyelonephritis located along the pelvis (p〈0.01). These results suggest that this rat model shows the characteristic feature of ascending pyelonephritis due toC. albicans and that the severity ofCandida pyelonephritis can be estimated fromCandida counts of bladder urine.
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  • 7
    ISSN: 1573-0832
    Keywords: Candida albicans ; Dimorphism ; Germ-tubes ; Starvation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract By incubating starved and unstarved yeast cells in synthetic media with a pH of 4.5 or 6.7 at 37°C the effect of a 3 hours' glucose starvation on germ-tube production byCandida albicans was evaluated. In addition the endocellular content of total carbohydrates, glycogen, trehalose and proteins after and before the starvation were dosed. The most interesting result was the overcoming of the pH-regulated dimorphism, thanks to the starvation treatment. Infact the starved cultures produced germtubes indifferently in neutral or acid media, whereas the filamentation of the unstarved cultures was more copious in pH 6.7 medium. The endocellular content of trehalose and protein was unchanged, whereas total carbohydrates and glycogen showed a shortage after the 3 hours' glucose starvation. The possible involvements of these metabolic changes in the regulation of dimorphic transition are discussed.
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  • 8
    ISSN: 1573-0832
    Keywords: Candida albicans ; Cell surface hydrophobicity ; Cell wall ; Clinical strains ; Protein and mannoprotein antigens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Characterization of common cell surface-bound antigens inCandida albicans strains, particularly those expressed in the walls of mycelial cells might be useful in the diagnosis of systemic candidiasis. Hence, antigenic similarities among wall proteins and mannoproteins fromC. albicans clinical serotype A and B isolates, were studied using polyclonal (mPAbs) and monoclonal (MAb 4C12) antibodies raised against wall antigens from the mycelial form of a commonC. albicans serotype A laboratory strain (ATCC 26555). Zymolyase digestion of walls isolated from cells of the different strains studied grown at 37°C (germination conditions), released, in all cases, numerous protein and mannoprotein components larger than 100 kDa, along with a 33–34 kDa species. The pattern of major antigens exhibiting reactivity towards the mPAbs preparation was basically similar for all the serotype A and B isolates, though minor strain-specific bands were also observed. The immunodeterminant recognized by MAb 4C12 was found to be absent or present in very low amounts inC. albicans isolates other than the ATCC 26555 strain, yet high molecular weight species similar in size (e.g., 260 kDa) to the wall antigen against which MAb 4C12 was raised, were observed, particularly in wall digests from serotype A strains. Cell surface hydrophobicity, an apparently important virulence factor inC. albicans, of the cell population of each serotype B strain was lower than that of the corresponding serotype A counterparts, which is possibly due to the fact that the former strains exhibited a reduced ability to form mycelial filaments under the experimental conditions used.
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  • 9
    ISSN: 1573-0832
    Keywords: Candida albicans ; Opportunistic pathogen ; Pyrimidine salvage pathway ; Uracil phosphoribosyltransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract This paper describes for the first time the partial purification and properties of uracil phosphoribosyltransferase (UPRTase) from the yeastCandida albicans. UPRTase was purified 38 fold by acid precipitation, DEAE-Sephacel chromatography and ultrafiltration. Further purification of UPRTase was unsuccessful due to the labile nature of the enzyme and the failure in obtaining satisfactory stabilizing conditions. SDS-PAGE suggested that the enzyme exists as a dimer of two dissimilar subunits with molecular masses of 47 and 38 kDa. The pH optimum for phosphoribosylation was about 7.5 and the optimal Mg++ concentration was 2 mM. The kinetics of the enzymes for its substrates, uracil and 5-phosphoribosyl-1-pyrophosphate (PRPP) were determined by measuring initial enzyme velocities over a wide range of concentrations of either substrate at different fixed concentrations of the second substrate. Graphic analysis of the data by Hanes-Woolf plots indicated that the reaction is indistinguishable from a double displacement reaction. ‘Ping pong’ mechanism has been previously reported for other phosphoribosyltransferases. The enzyme has a low affinity for its substrates (K m=70.5 and 186 µM for uracil and PRPP, respectively) as compared with those ofE. coli and baker's yeast. Inhibition studies indicate that 5-fluorouracil acts as an alternative substrate for UPRTase with 1.6 times higher specific activity.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 109 (1990), S. 99-109 
    ISSN: 1573-0832
    Keywords: Candida albicans ; pulmonary alveolar macrophage ; host-parasite interaction ; pulmonary infection ; phagocytosis and killing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The initial interaction of Candida albicans with pulmonary tissue of B6D2/F1 mice was investigated. The LD50 for mice challenged intravenously (IV) was approximately 3 × 105 yeasts, whereas the LD50 by the intratracheal (IT) route was in excess of 108 yeasts. Mice challenged IV died of progressive yeast growth in the kidneys. In contrast, mice challenged IT rapidly eliminated the entire inoculum by the first day after challenge. Resident pulmonary alveolar macrophages (PAM) killed upwards of 70% of C. albicans in an in vitro killing assay. At effector: target ratios favoring the effector cell population resident PAM were able to restrict the formation of yeast germ tubes to only 30% of the yeasts, whereas at equivalent ratios virtually all of the intracellular yeasts produced germ tubes. Evaluation of the ability of PAM, harvested from genetically different strains of inbred mice, to kill C. albicans in vitro showed that killing ability was a property of resident PAM from mice with the black 6 background. It was discovered that during the initial stages of infection in vivo, the expression of the F4/80 surface molecule was down regulated, and the expression of the Mac 1 surface molecule upregulated. There were no quantitative changes in expression of either Mac 2, Mac 3, Ly 5 or the 5C6 surface epitopes. Taken together, the data show that pulmonary tissue is quantitatively very resistant to C. albicans infection, because of the ability of resident PAM to rapidly phagocytize and kill yeasts. Killing of C. albicans by resident PAM may be a property of a subset of this mononuclear phagocyte population and was accompanied by alterations in the expression of surface molecules.
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