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  • Fusarium  (34)
  • Aspergillus  (29)
  • Paracoccidioides brasiliensis  (25)
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  • 1
    ISSN: 1573-0832
    Keywords: Versicolorin A ; hemiacetal ; reductase ; Aspergillus ; versicolorin C ; dihydrosterigmatocystin ; aflatoxin G2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Versicolorin A hemiacetal was converted to versicolorin C in cell-free systems fromAspergillus parasiticus. The rate of reaction catalyzed by the 35–70% ammonium sulfate fraction was 0.43 nmol min−1 mg−1 with NADPH as cosubstrate and 0.17 nmol. min−1 mg−1 with NADH at 25°C at pH 7.4. The product from incubation of 17-hdyroxy-16,17-dihydrosterigmatocystin with the 35–70% ammonium sulfate fraction and NADPH was a polar compound which was converted to dihydrosterigmatocystin by 0.4 M HCl. The olar comound is proposed to be the 14,17-hydrated open-chain derivative of dihydrosterigmatocystin. Aflatoxin G2a was also reduced in this system to a polar product tentatively identified as the 13,16-hydrated open-chain derivative of AFG2. The reductase activity may be involved in the formation of reduced intermediates and aflatoxins in cultures ofA. parasiticus.
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  • 2
    ISSN: 1573-0832
    Keywords: Alterations in pathogenicity ; in vitro growth ; Paracoccidioides brasiliensis ; reisolation ; subcultivation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Thein vitro subcultivation of some microorganisms for long periods causes measurable loss of their pathogenicity, which can be reverted by reisolation from infected hosts. We compared the pathogenicity and thein vitro growth pattern of oneP. brasiliensis isolate (Pb 18) in its yeast phase, using the following samples: 1) The original pathogenic Pb 18 (OP). 2) Pb 18 attenuated by continuousin vitro subcultivation (AT). 3) Pb 18 (AT) reisolated from susceptible B 10.A mice (RS). 4) Pb 18 (AT) reisolated from resistant A/SN mice (RR). Pathogenicity was evaluated by anatomopathology and mortality of mice infected i.p. with 5×106 fungi. Median survival times of mice infected with OP ranged from 74 to 117 days during the first 51 months of subculturing; with more cycles of subculturing the median survival time increased, reaching 250 days at the 64th month. This indicated decreasing virulence of OP during this period of subculturing. Survival of mice infected with RS and RR was respectively 112 and 123 days, which is similar to the behavior of the OP variant. Thein vitro growth curve profile of RR showed significantly higher numbers of total and viable yeasts than the other studied variant. These results show that: 1) Pb 18 isolate loses its pathogenicity by continuous subcultivation. This phenomenon is reverted by reisolation from mice, independently from their susceptibility to the fungus; 2) thein vitro growth patterns of Pb 18 do not correlate with alterations in pathogenicity but are influenced by the host's environment.
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  • 3
    ISSN: 1573-0832
    Keywords: Fusarium ; trichothecene ; cytotoxicity ; bioassay ; mycotoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Twenty-six trichothecene mycotoxins produced by Fusarium sporotrichioides (MC-72083) and Fusarium sambucinum were screened for relative cytotoxicity in cultured baby hamster kidney (BHK-21) cells. The relative cytotoxicity was measured as LC100. The most cytotoxic trichothecenes were T-2 toxin (5 ng/ml) and the recently isolated 4-propanoyl HT-2 (5 ng/ml) and 3′-hydroxy T-2 toxin (5 ng/ml). T-2 tetraol (1 × 104 ng/ml), 8-β-hydroxytrichothecene (1 × 104 ng/ml), sporotrichiol (2 × 104 ng/ml), 8-oxodiacetoxyscirpenol (6 × 104 ng/ml) and 8-acetyl T-2 tetraol (1 × 105 ng/ml) were the least toxic of the regular trichothecenes. None of the modified trichothecenes or the apotrichothecene were very cytotoxic: 8-β-hydroxysambucoin (2 × 103 ng/ml), FS-1 (5 × 103 ng/ml), 8-α-hydroxysambucoin (8 × 104 ng/ml) and trichotriol (1 × 105 ng/ml). The modified trichothecenes, FS-2 and FS-3, were not toxic even at 1 × 105 ng/ml. The baby hamster kidney cell bioassay proved to be a very sensitive and reproducible means of screening new trichothecene mycotoxins for relative cytotoxicity.
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  • 4
    ISSN: 1573-0832
    Keywords: Mycelial conidia ; Paracoccidioides brasiliensis ; scanning electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The conidia produced by the mycelial form of Paracoccidioides brasiliensis were examined by scanning electron microscopy for the first time. Several different conidial types were characterized. These included intercalary arthroconidia, several types of septate conidia that are formed from other conidia, pedunculate conidia, and terminal hyphal conidia. In addition, the ultrastructure of the supporting pedestal of the pedunculate conidium was found to be separated from the mother conidium by a septum in some instances, and at other times it was not.
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  • 5
    ISSN: 1573-0832
    Keywords: Bioassays ; Enniatin B ; Fusarium ; Trichothecenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Twenty-nineFusarium isolates, representing three new taxa originated by Nirenberg fromF. sambucinum Fuckel sensu lato, namely:F. sambucinum Fuckel sensu stricto,F. venenotum Nirenb., andF. torulosum (Berk. & Curt.) Nirenb., were tested for in vitro production of toxic secondary metabolites on autoclaved corn kernels.F. sambucinum sensu stricto was able to produce type A trichothecenes and enniatin B (EB). In particular, amongst the 14 isolates tested, 5 produced only diacetoxyscirpenol (DAS) (up to 700 µg/g); 1 produced only neosolaniol (NEOS) (250 µg/g); 2 produced T-2 toxin (T-2) + NEOS (up to 175 and 150 µg/g, respectively); 1 produced NEOS + DAS (300 and 100 µg/g, respectively); and 5 produced DAS + EB (up to 500 and 140 µg/g, respectively). All six isolates ofF. venenotum were able to produce only DAS (up to 100 µg/g).F. torulosum produced no trichothecenes, but four out of nine tested isolates were able to produce EB (up to 140 µg/g). Zearalenones and type B trichothecenes were not found. The toxicity of the culture extracts towardsArtemia salina L. was correlated in general with the occurrence of the above toxins, except for someF. torulosum strains. However, the lack of correlation between the amounts of toxins recovered and toxic activity observed in theGeotrichum candidum Link ex Pers. andA. salina assays suggested the presence of unknown toxic compounds.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Mycopathologia 127 (1994), S. 167-173 
    ISSN: 1573-0832
    Keywords: Bahrain ; Distribution ; Fusarium ; Soil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The prevalence and distribution of soil-inhabitingFusarium species in the soil of vegetable crops grown under custom-made plastic tunnels were studied at three geographical locations on the island of Bahrain. Six species ofFusarium representing a total of 1154 isolates were isolated on modified Komada medium. All species reported in this survey are recorded for the first time from the hot, arid desert of Bahrain.Fusarium solani andF. oxysporum were among the most frequently isolated fungi in all locations and crops.
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  • 7
    ISSN: 1573-0832
    Keywords: Paracoccidioides brasiliensis ; Paracoccidioidomycosis ; fungal antigen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We investigated the occurrence of antigenic and biochemical variability among Paracoccidioides brasiliensis antigen batches prepared according to the same protocol. Initially (experiment #1), we analyzed two antigen lots of two human isolates (Bt1 & Bt2), cultured in two media (PYG: bactopeptone, yeast extract, glucose; MMM: McVeigh & Morton medium) in SDS-PAGE and in two immunological tests (imunodiffusion-ID and footpad swelling test-FPT). Afterwards (experiment #2), we compared the antigenic profile of three antigen batches from three human isolates (Bt1, Bt2 & Bt3) by two-dimensional immunoelectrophoresis (2 D-IEP) against a reference system for P. brasiliensis antigens. In experiment #1, there were important intra- and inter-strain antigenic differences between batches of the fungal isolates cultured on both media. The block titration of the antigen batches for the immunological tests revealed correlation between protein concentration and biological activity in ID and no correlation in FPT. In experiment #2, the reference system for P. brasiliensis showed 26 antigen peaks. There were important differences between batches prepared from the same isolate and between batches from different isolates. Our data suggested the occurrence of instability in the synthesis of antigenic components by a same P. brasiliensis isolate, under controlled incubation conditions.
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  • 8
    ISSN: 1573-0832
    Keywords: Brazil ; dimorphic fungi ; ecology ; Paracoccidioides brasiliensis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract We compared the antigenic characteristics of two thermo-dependent dimorphic fungi isolated from soil in Botucatu, an endemic area of paracoccidioidomycosis (PCM) and Paracoccidioides brasiliensis. The soil isolates grew as cerebriform colonies at 37 °C (yeast form) and as cottonous colonies at 25 °C (mycelial form). No pathogenicity for ddY mice or hamsters were observed. In immunodiffusion test, there were precipitation bands between the 2 soil isolates and pooled PCM patient sera. There were also common precipitation bands at 21, 50 and 58 kDa between the soil isolates antigens and PCM patient sera by Western-blotting, but no gp43 kDa band. No gene for gp 43 kDa protein was detected in the soil isolates by PCR. The fact that these isolates were obtained from an endemic area of PCM and there were some antigenic similarities between the soil isolates and P. brasiliensis in immunodiffusion test and Western-blotting may have some importance in epidemiological surveys done with paracoccidioidin as well interfering with the immune response of the exposed population.
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  • 9
    ISSN: 1573-0832
    Keywords: Alternaria ; Aspergillus ; cytotoxicity ; Fusarium ; Penicillium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The predominant fungi present in samples of reject and retail red kidney beans were Aspergillus glaucus, Penicillium spp. and Alternaria spp. Together with A. ochraceus, A. flavus, Fusarium spp., and Trichoderma, these isolates from the reject beans were screened for numerous mycotoxins by TLC. The most consistently produced mycotoxins were penicillic acid (from A. ochraceus and Penicillium spp.) and Alternaria toxins (tenuazonic acid and alternariol). A. glaucus strains were tested for cytotoxicity in three tissue culture cell lines with positive results.
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  • 10
    ISSN: 1573-0832
    Keywords: Aspergillus ; Chitin ; Fusarium ; Mosquito ; mycopathogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract During a short survey of soil and mosquito breeding sites in Lucknow, India for potential mycopathogen from a period of August–October 1996, 11 species of fungi in 5 genera were isolated using live mosquito larvae as host. Aspergillus flavus , A. fumigatus and Fusarium semitectum were the most frequently isolated species. Other fungi recorded were A. niger , A. ochraceus , A. terreus , A. versicolor , Geotrichum candidum , Penicillium verrucosum , Paecilomyces sp. and Fusarium sp. (Liseola/Elegans complex). Insect cell walls are known to contain chitin, so fungal isolates were tested for their chitinase activity on semi synthetic medium containing colloidal chitin. High chitinolytic activities were observed with A. flavus and A. ochraceus. Chitinase producers can be considered as potential pathogens. However, the higher incidence of F. semitectum could not be explained by inability to utilize chitin.
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