Aspergillus tamarii is known to produce mycotoxins such as cyclopiazonic acid (CPA) and kojic acid (KA). Recently we isolated several cultures of A. tamarii from Japanese tea fields and found one of the isolates “No.19”, and single-spore cultures (NRRL 25517, 25518, 25519) derived from this isolate, produced substantial quantities of aflatoxin B1 and B2. Here we report the results of a limited survey of 15 A. tamarii strains isolated from Japanese tea fields, one strain from silk worm excrement and 29 strains received from culture collections. Most A. tamarii isolates produced CPA and KA but only the strains derived from isolate “No.19” and strain NRRL 443 produced aflatoxin B1 and B2. Each aflatoxin-producing strain of A. tamarii showed yellow-green colors in young colonies and did not darken in age, suggestive of the “bronze series”. The relation between the levels of CPA or KA production by the individual strains was very weak.
We investigated the effect of cultured human intestinal microflora on several mycotoxins, ochratoxin A (OCTA), patulin, zearalenone, citrinin, aflatoxin B1 and fumonisin B1, B2. Human intestinal microflora derived from a Japanese health adult was cultured using continuous flow culture system we had developed previously. We examined the recoveries of seven mycotoxins after incubation with human intestinal microflora for 8 hr. As a result, zearalenone, citrinin, and aflatoxin B1 were not degraded by human intestinal microflora for 8 hr incubation. It was, however, suggested that OCTA and fumonisin B1, B2 might he partially degraded by human intestinal microflora.
A total of 246 apparently healthy corn samples were collected from nine villages in the counties of Cixian, Linxian, Anyang, Fanxian and Yanqing in the People's Republic of China. All of the samples were harvested in the autumn of 1995 and were intended for human consumption. The samples were analyzed for fumonisin and aflatoxin B1 contamination by ELISA. Of 164 corn samples collected from areas in which the risk of human esophageal cancer (HEC) is high, fumonisin was detected in 106 samples (0.5-16.0 ppm, average ; 0.70 ppm), but of 82 samples collected from HEC low risk areas, fumonisin was found in 23 samples (0.5-1.5 ppm, average ; 0.20 ppm). The frequency of fumonisin contamination in the high risk areas was approximately twice that of low risk areas, and the average content of fumonisin in samples from HEC high risk areas was about three times higher than that from HEC low risk areas. For aflatoxin B1, the concentration and frequency of aflatoxin B1 positive samples varied greatly from village to village but in general, aflatoxin contamination was low in HEC low risk areas. Although a clear relationship between fumonisin contamination and HEC incidence could not be distinguished, it is evident that people living in HEC high risk area sustained more exposure to fumonisin and aflatoxin than people living in HEC low risk area.
Our previous work indicated that sequential exposure to a low concentration of deoxynivalenol (DON) increased the susceptibility of mice to salmonella via oral infection. In this study, the effect of DON on humoral and cellular immune defense against salmonella infection in the same conditions as the previous study was investigated. DON reduced the production of specific antibodies against salmonella and the delayed type (footpad) hypersensitivity (DTH) reaction to formalin-killed salmonella extract. These results demonstrate that the immunosuppresive effects of DON are involved in an increased susceptibility to salmonella infection.
The mycotoxins used were T-2 toxin, fusarenon-X, deoxynivalenol, nivalenol and roridin A, with a well-known inhibitor of platelet aggregation, aspirin, as the control. Platelet aggregation was measured by the turbidimetric method of Born. T-2 toxin was an effective inhibitor of platelet activating factor (PAF)-induced platelet aggregation in vitro. Roridin A inhibited dosedependently platelet aggregation induced by all aggregating agents applied (ADP, epinephrine, collagen, PAF, arachidonic acid). The other toxins showed little or no inhibition. In contrast to aspirin, T-2 toxin did not affect cyclooxygenase activity and the inhibition was reversible on depletion of the toxin. The inhibition by roridin A was irreversible. The different inhibitory effects by trichothecenes may be related with the different side chains of their skeletal structures.
The effect of versicolorin A on ionic permeability in planar lipid bilayer membranes was studied by measuring current-changes at various conditions. Versicolorin A significantly elevated the conductance of lipid bilayer membranes. From an analysis of reversal potential, it was concluded that versicolorin A increased the bilayer conductance by facilitating proton permeability, suggesting that the conductance-increasing activity may contribute to the uncoupling effect of versicolorin A on mitochondrial respiration.