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  • 1
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Zusammenfassung In einer genetisch nachweisbar polyploiden Familie von Saccharomyces wurden der Gesamtgehalt an freien intrazellulären Aminosäuren und die Geschwindigkeit der Zellteilungen in Abhängigkeit der Ploidie bestimmt. Es liess sich zeigen, dass die Geschwindigkeit der Zellteilungen von der Ploidie nicht beeinflusst wird, während der Gesamtgehalt an freien intrazellulären Aminosäuren sich direkt proportional mit der Zunahme der Ploidie vergrössert (Verhältnis 1:1).
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  • 2
    ISSN: 1573-0832
    Keywords: anaerobiosis ; Candida albicans ; heterokaryons ; hybrids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary During aerobic replication, balanced heterokaryons (hets) of Candida albicans produced by fusing protoplasts of complementing auxotrophic strains characteristically segregate low frequencies of prototrophic monokaryons bearing hybrid nuclei formed either through karyogamy or unidirectional internuclear genetic transfers within het cells. Anaerobic growth causes exponential inactivation of hets and induces their production of hybrid monokaryons. Both responses are functions of heterokaryosis as such and not the genetic backgrounds of hets. Evidence is presented that (i) the nuclei of anaerobically generated hybrids arise through induction in hets of karyogamy not internuclear genetic transfers and that (ii) the events underlying that induction are different from those responsible for inactivation of the cells.
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  • 3
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Earlier investigations have shown that inactivation of non-budding cells ofC. albicans by ultraviolet radiation is determined in part by (i) their post-irradiation incubation temperature, (ii) opportunity for exposure to long chain fatty acids or sterols and (iii) the nutri tional quality of their post-irraditation growth medium. These cultural conditions do not affect the viability of cells which are budding when irradiated nor the frequency of mutants among the survivors of irradiated, unbudded populations. Several lines of evidence have indicated that the post-irradiation growth conditions influence recoveries from non-genetic forms of uv-induced damage which are potentially lethal only for cells which are not in the process of division when irradiated. Studies reported here show that mutation to resistance to the polyene antibiotic, amphotericin B, changes the composite pattern of survival responses of uv treated unbudded cells to the three post-irradiation conditions. Acquisition of amphotericin B resistance does not alter the uv mutability of such cells nor the vulnerability of budding cells to uv inactivation. Differences in susceptibilities of cells to polyene antibiotics are known to be determined by differences in the composition and structural arrangement of their membranes. The present observations are consonant, therefore, with a previous proposal that post-irradiation temperature, nutrition and contact with lipid affect cellular recoveries from damages to processes which (i) are essential for initiation of cell division and (ii) are related to the organization of the cell membrane.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 68 (1979), S. 105-120 
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Cells of Candida albicans plated on media containing nalidixic acid (Nal) either die, adapt physiologically to Nal-tolerance or mutate to Nal-resistance. The fraction of a population exhibiting each response depends on the growth phase of cells when plated and their nitrogen and carbon nutrition and growth temperatures before and after plating. Nal induces Nal-resistant mutants in very high frequency but only at 37 C on plates containing i) glucose as primary carbon source and ii) adenine, a sulfur amino acid or a representative of the glutamic acid family of amino acids. Nal does not affect either forward mutation to caffeine-resistance or reverse mutation from histidine auxotrophy to prototrophy. Nal-resistant mutants produce minute colonies on Nal-free medium, respire oxidatively and are unusually sensitive to inhibitors of oxidative phosphorylation. They revert spontaneously to wild type at very high rates but can be propagated indefinitely in the absence of Nal by serial selection and replating of minute colonies. Cellular inactivation and induction of Nal-resistant mutants are greatly affected by specific inhibitors of mitochondrial macromolecular syntheses. The presence of chloramphenicol or erythromycin during exposure to Nal prevents cell death and mutation but has no effect on adaptation to Nal-tolerance. Growth on acriflavin or ethidium bromide enhances resistance of cells to inactivation when subsequently plated on Nal containing media. It is concluded that Nal-induced cellular inactivation and mutation to Nal-resistance, but not adaptation to Nal-tolerance, result from damages to the mitochondrion which are fixed or promoted by macromolecular syntheses within the mitochondrion. Implications of these findings for the therapeutic use of Nal are discussed.
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  • 5
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Heterokaryons (hets) of Candida albicans constructed by fusing protoplasts of complementing auxotrophs produce heterogeneous clones on minimal medium consisting of (i) a minority of slow-growing hets, (ii) a preponderance of non-growing, parental-type auxotrophic monokaryons, and (iii) some prototrophic monokaryons bearing hybrid nuclei. Hets grown at a given temperature within the range 25° C to 41° C replate with higher efficiencies at any lower temperature and exhibit progressively declining plating efficiencies as plate temperatures increase beyond that at which they were initially grown. Neither auxotrophic nor prototrophic monokaryons show such responses. Growth of colonies produced by hets, wild-type strains or prototrophic hybrid monokaryons is stimulated by temperatures in the order, 37° C 〉 30° C 〉 41° C 〉 25° C. However, the proportion of hets to auxotrophic monokaryons within individual net clones increases directly from 25° C to 41° C. Though this pattern obtains whether colonies are compared at equivalent sizes or ages, het frequencies decline as colonies age at all temperatures. Appearance of hybrid monokaryons within het clones is unaffected by growth temperature. The relationships of temperatures to plating efficiencies and stabilities of hets are independent of the natures of their complementing auxotrophies or the wild-type backgrounds of their nuclear components and are, therefore, functions of heterokaryosis per se. Modifications of these relationships by selective metabolic antagonists or by growth of hets on different preand post-plating carbon sources indicate that they reflect temperature-dependent properties of mitochondria which are peculiar to hets.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 35 (1968), S. 346-360 
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary A heretofore undescribed minute-rough colonial variant has been isolated from cultures of a red, adenine auxotroph ofCandida albicans, strain WC—7. The variant has been detected only in WC—7 populations which are propagated at 37° C on very low concentrations of adenine. It produces colonies much smaller than those of WC—7 at both 25° C and 37° C on defined media containing either ammonium ion or casein hydrolysate as nitrogen sources. On ammonium nitrogen, young variant colonies are smooth and contain only typical yeast cells. While colonies which grow at 37° C retain these characteristics upon extended incubation, those growing at 25° C progressively roughen due to extensive development of pseudohyphae as the glucose levels in their vicinities decline. Under comparable conditions, colonies of the parental strain WC—7 remain smooth and free of pseudohyphae, Supplementing the medium with large amounts of glucose, intermediates of the tricarboxylic acid cycle or any one of several amino acids biosynthetically derived from intermediates of oxidative respiration prevents formation of pseudohyphae by the variant without significantly affecting its growth rate. Genetically, the variant is unstable and reverts frequently to a stable, rapidly growing form apparently identical to strain WC—7. Evidence is presented indicating that, under certain circumstances, variant cells can exercise a contact-inhibition of the growth of their revertants. Possible physiological bases of the variriant's cultural properties are discussed.
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  • 7
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary An adenine requiring strain ofCandida albicans, WC-7, forms large smooth colonies. When grown at 37° C under conditions of severe adenine deprivation, WC-7 cultures accumulate variant cells (MR variants) which produce minute, rough colonies. The variants are stable in that they persist upon repeated selective subculturing. However, they do exhibit high rates of reversion to their large, smooth colony progenitor form. It is shown that cultural conditions which favor the appearance of variants in WC-7 populations create a metabolic stress within the WC-7 cells which leads to their direct transformation into variants. These same conditions also impart a selective growth advantage to variant cells over WC-7 cells. Considerations of the genetic properties of the variants and the factors involved in their induction argue strongly that variant cells originate through alteration of a non-genic, hereditary determinant.
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  • 8
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Description / Table of Contents: Zusammenfassung Hefezellen besitzen einen von Temperatur abhängigen Mechanismus für Dunkelerholung von ultravioletter Bestrahlung. Beweis ist gegeben, dass dieser Erholungsmechanismus eine andere Art von ultravioletter Schädigung betrifft, als diejenige, die durch Photoreaktivierung bewirkt wird. Da Photoreaktivierung hauptsächlich durch die Beseitigung der durch das Kardinalultraviolett verursachten DNA Läsionen erfolgt, die zu Zellularinaktivierung führt, sind die Befunde in Übereinstimmung mit den vorherigen Beweisen, dass die von Temperatur abhängige Dunkelerholung der bestrahlten Hefezellen durch Wiederherstellung oder durch Umleitung der nicht genetisch inaktivierenden Schädigung erfolgt.
    Notes: Abstract Yeast cells possess a temperature-dependent mechanism for dark recovery from ultraviolet irradiation. Evidence is presented that this recovery mechanism affects a different kind of ultraviolet damage than that repaired through photoreactivation. Since photoreactivation is due specifically to removal of the cardinal ultraviolet induced DNA lesions contributing to cellular inactivation, the findings are consistent with previous evidence that temperature-dependent dark recovery of irradiated yeasts occurs through the repair or by-passing of non-genetic inactivational damage.
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  • 9
    ISSN: 1573-0832
    Keywords: Candida albicans ; caffeine ; mutagens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Ultraviolet radiation is more effective than either ethyl methanesulfonate or nitrous acid in inducing reverse mutation from auxotrophy to prototrophy in C. albicans. The killing effect of each of the mutagens is greater for cells grown at 37 C than at 25 C after treatment; mutation frequencies are unaffected by post-treatment growth temperatures. Though caffeine depresses survival of mutagen treated cells at both 25 C or 37 C, its effect is more pronounced at 37 C. Caffeine has no effect on mutagenesis by nitrous acid or ethyl methanesulfonate; it depresses UV mutagenesis, but only at 37 C and at high UV dosages. These findings indicate that UV mutagenesis in C. albicans is mediated by a caffeine-sensitive, recombinational system for DNA repair analogous to those known to occur in other species of yeasts. The repair system of C. albicans is unique in being susceptible to caffeine only at high temperature and when the number of DNA lesions to be repaired is large. The caffeine-sensitive steps in repair critical to UV mutagenesis are not involved in fixing mutations induced by the chemical mutagens tested.
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  • 10
    ISSN: 1573-0832
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Complex nutritional supplements which stimulate growth of monokaryons of Candida albicans have no effect on growth or stability of heterokaryons. This evidence that heterokaryotic growth is characteristically limited by something other than nutritional circumstances is consistent with prior indications of naturally dysfunctional ribosomes in heterokaryons.
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