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  • 1
    ISSN: 1573-0832
    Keywords: aflatoxin ; Aspergillus flavus ; non-toxigenic O-methylsterigmetocystin ; sterigmetocystin ; nontoxigenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Non-aflatoxin-producing isolates ofAspergillus flavus from nature and isolates ofA. flavus that had lost their toxigenic trait following laboratory transfer were compared biochemically. After the addition of aflatoxin B1 precursors sterigmatocystin or O-methylsterigmatocystin to whole cell cultures, the non-toxin producing isolates from nature remained non-toxigenic while toxigenicity was restored in the nontoxigenic laboratory strains. Results imply a lack of enzymes needed for biochemical conversions of precursors to aflatoxin B1 in natural non-producers and suppression of these enzymes in the nonproducing laboratory strains.
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  • 2
    ISSN: 1573-0832
    Keywords: aflatoxin ; kwashiorkor ; excretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A group of five children with kwashiorkor, seven with marasmic kwashiorkor and one underweight child were given an aflatoxin-free diet consisting of maize meal and milk powder. Blood specimens were collected on admission; on day 4 and 10, 24 hour urine and stool samples were collected for the first ten days. Serum, urine and stool samples were analysed for aflatoxins using high performance liquid chromatography with fluorescent detection, after various extraction and clean-up procedures. The children with kwashiorkor and marasmic kwashiorkor excreted aflatoxins in stools for up to 9 and 6 days after admission respectively. No aflatoxins were detected in the stools or urine of the underweight child. In kwashiorkor, urinary excretion ceased after 2 days, while in marasmic kwashiorkor urinary excretion persisted for 4 days. In stools, B1 was the type of aflatoxin detected most frequently in kwashiorkor and least frequently in marasmic kwashiorkor. Aflatoxin M2 was frequently detected in the stools of both groups of children. Estimates of the total amount of aflatoxin excreted by kwashiorkor and marasmic kwashiorkor indicate that these children were harbouring up to 4 μg/kg body weight at the time of admission. These findings establish that aflatoxins accumulate in body fluids and tissues in kwashiorkor and marasmic kwashiorkor which is only slowly eliminated.
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  • 3
    ISSN: 1573-0832
    Keywords: versiconal ; aflatoxin ; Aspergillus versicolorin C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The primary product of hydrolysis of versiconal acetate catalyzed by porcine liver esterase and the 35–70% ammonium sulfate fraction from a soluble extract from mycelia of Aspergillus parasiticus was versiconal. Versiconal was stable at neutral pH for several hours and was rapidly converted to versi-colorin C by treatment with 0.4 M HCl. The addition of NADPH to the 35–70% ammonium sulfate fraction resulted in conversion of versiconal acetate to both versiconal and versicolorin C. The conversion of versiconal acetate to versicolorin C in the cell-free system is proposed to involve an esterase and an NADPH-dependent cyclase.
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  • 4
    ISSN: 1573-0832
    Keywords: Aspergillus flavus ; aflatoxin ; cytochemistry ; Gossypium ; ultrastructure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Cottonseeds having fluorescent fibers were harvested from fields in Arizona and examined utilizing light microscopy and transmission electron microscopy. The occurrence of fluorescent fibers indicated that seeds had been infected by Aspergillus flavus during development. Presence of A. flavus was verified by plating portions of seeds with fluorescent fibers. Hyphae, conidial heads, and conidia were identified readily in differentially-stained cotyledon tissue processed for light microscopy. Utilization of transmission electron microscopy permitted observations on lignified seed coats and cotyledons of mature cottonseeds. Hyphae were located throughout the cotyledon and in the nonlignified layers of the seed coat. The identification of hyphae in cross sections of vessel elements within the seed coat provided ultrastructural evidence supporting the hypothesis that A. flavus may enter seeds via the vascular tissue. Controls for the microscopy studies included observations on cottonseeds with no visual signs of infection and on laboratory-grown cultures of A. flavus. These observations demonstrated that the hyphae localized within fluorescent seeds had features characteristic of A. flavus and that fungal-like structures do not occur within uninfected seeds.
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  • 5
    ISSN: 1573-0832
    Keywords: Storage fungi ; mycotoxins ; food contaminants ; Aspergillus flavus ; Aspergillus Candidas ; aflatoxin ; rice bran ; raw rice ; parboiled rice
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Thirty four samples of rice bran, of which 9 were from raw (untreated) rice (RR) and 25 from parboiled rice (PbR) were collected from commercial rice mills in and around Madras and analysed for storage mycoflora and mycotoxins. Fungi of the Aspergillus flavus group were present in 29 of the 34 samples (8 from RR and 21 from PbR) in quantities ranging from 〈1–432 thousand propagules/g, though not always as the dominant mycoflora. Fungal numbers were usually higher in RR than in PbR samples. Five of the 9 RR samples and 6 of the 25 PbR samples were positive for aflatoxins. Among 29 isolates of A. flavus obtained from the bran samples, 16 isolates −6 from RR bran and 10 from PbR bran — were found to be toxigenic in vitro. Some isolates of A. candidus also seemed to produce aflatoxin and other fluorescent substances.
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  • 6
    ISSN: 1573-0832
    Keywords: Aspergillus flavus ; aflatoxin ; fungal competition ; barley grain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Colonization of barley grain by Aspergillus flavus and formation of aflatoxin B1 in the presence of Penicillium verrucosum, Fusarium sporotrichioides, and Hyphopichia burtonii were studied over a three-week period in all combinations of 20 or 30 °C and 0.97, 0.95 or 0.90 aw. Grain colonization was assessed initially by observing hyphal extension on the grain surface, using scanning electron microscopy, and then from the proportion of seeds infected and numbers of colony forming units (cfu) formed. Aflatoxin b1 concentrations were determined by enzyme linked immunosorbent assay using a monoclonal antibody. These studies showed that interaction between A. flavus and other fungi in paired culture had different effects on both colonization and aflatoxin formation depending on the species involved and environmental conditions. Germination of A. flavus spores was unaffected by the presence of other species on the grain surface. Subsequently, three principal patterns of A. flavus colonization of barley grain were observed through the incubation period in the presence of other fungal species: (a) colonization unaffected by the presence of other species; (b) colonization initially slower in the presence of other species but later differing little from pure cultures; and (c) colonization adversely affected by the presence of other species. Five main patterns of aflatoxin B1 production were observed relative to pure culture but with no consistent relationship with species, aw, temperature or incubation period; (a) little changed; (b) increased slowly; (c) decreased; (d) enhanced; and (e, f) increased initially but later decreased to (e) the same level as in pure culture or (f) to less than in pure culture. Generally, production of aflatoxin B1 by A. flavus was less than in pure culture but sometimes was changed only slightly by the presence of P. verrucosum, F. sporotrichioides or H. burtonii or was temporarily enhanced.
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  • 7
    ISSN: 1573-0832
    Keywords: corn ; mycotoxins ; Indonesia ; poultry feed ; aflatoxin ; zearalenone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Every truck load of corn (n=52) entering and every batch of poultry feed (n=290) leaving a Bogor feedmill over one year was analysed for aflatoxins, zearalenone, ochratoxin A and sterigmatocystin. Fifty loads of corn and 274 of the batches of chicken feed contained aflatoxins. Zearalenone was detected in 11 corn samples but was not found in the formulated feed. Ochratoxin A was detected in one corn sample, but not in feed. Corn can account for all of the aflatoxin in the feed since levels were always lower in the finished product. There was no quantitative association between the proportion of bright green-yellow fluorescent, purple or mouldy kernels and the mycotoxin contents of the composite samples. Nevertheless, the absence of abnormal kernels indicates higher quality corn since the highest levels of mycotoxins occurred in the abnormal kernels.
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  • 8
    ISSN: 1573-0832
    Keywords: aflatoxin ; drought ; maturity ; moisture ; peanuts ; phytoalexins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Samples of Florunner peanuts were collected throughout a period of late-season drought stress with mean geocarposphere temperatures of 29 and 25 °C, and determinations of maturity, kernel water activity (aw), percent moisture, capacity for phytoalexin production, and aflatoxin contamination were made. Results showed an association between the loss of the capacity of kernels to produce phytoalexins and the appearance of aflatoxin contamination. Kernel aw appeared to be the most important factor controlling the capacity of kernels to produce phytoalexins. Mature peanuts possessed additional resistance to contamination that could not be attributed solely to phytoalexin production. Kernel moisture loss was accelerated in the 29 °C treatment compared to the 25 °C treatment, and data indicated that the higher soil temperature also favored growth and aflatoxin production by Aspergillus flavus in peanuts susceptible to contamination.
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  • 9
    ISSN: 1573-0832
    Keywords: aflatoxin ; antifungal ; Aspergillus ; Fusarium ; Penicillium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Soil is presumed to be a major source of inoculum for Aspergillus flavus which contaminates cottonseed and produces the potent carcinogen, aflatoxin. Little is known about the mycoflora of the low desert soils of cotton fields where aflatoxin is a chronic problem. In this study, soils from cotton fields in southwestern Arizona and southeastern California were assayed for filamentous fungi. Forty-two taxa, predominantly in the genera Aspergillus, Penicillium and Fusarium, were isolated. To determine whether or not compounds produced by these fungi could be potential inhibitors of A. flavus, extracts of strains of each taxon were tested for their ability to inhibit growth of A. flavus. Twelve taxa produced compounds inhibitory to A. flavus, including several strains of Fusarium solani, Penicillium vinaceum and Aspergillus auricomus.
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  • 10
    ISSN: 1573-0832
    Keywords: Aspergillus flavus ; starch ; reducing sugars ; kojic acid ; aflatoxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Depletion of sugar and starch carbon sources and concomitant formation of secondary fungal metabolites, aflatoxin and kojic acid, were examined in growing corn inoculated with Aspergillus flavus. Kernels from control and inoculated ears were removed and analyzed after 16, 24, 48, 96 and 168 hrs. Reducing sugars were not significantly different for inoculated and control non-inoculated samples, but after 168 hrs (seven days) starch content was 20% lower in inoculated than in control samples. Kojic acid was detected before aflatoxins formed. Kojic acid, the oxidized product of kojic acid, and aflatoxin were all present in samples two days from inoculation. The formation of this oxidation product may influence toxin levels.
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