The effects of versicolorins A & B on the respiratory chains of mitochondria were studied using electron transport particles (ETP) prepared from rat liver mitochondria. Both compounds depressed the respiration of ETP, exerting markedly stronger inhibition on NAD-linked than on succinate-linked respiratory system. Of the two compounds, versicolorin B, which has bis-tetrahydrofuran ring, was found to be eminently stronger inhibitor than versicolorin A which had bis-dihydrofuran ring. Neither succinate dehydro-genase (complex II) nor cytochrome c oxidase (complex IV) of the respiratory chain was affected by both compounds. NADH-CoQ2 reductase (complex I) and durohydroquinone oxidase (complex III and IV) activities were depressed by these compounds, exerting a stronger inhibition on the latter reaction. These results apparently indicate that versico-lorins A & B interefere mainly with the redox reaction of the complex III (cytochrome bci complex) and at the same time weakly with complex I (NADH-CoQ10 reductase). It was thus concluded that versicolorins A & B depressed mitochondrial respiration by direct interactions with respiratory enzymes involving in the electron transport system in mito-chondria.
The occurrence of the aflatoxin (AF)-producing strains of Aspergillus flavus was surveyed on 11 retail samples of five kinds of other type edible nuts (mostly tree nuts) and, for the comparing purpose, on 10 samples of peanuts. All samples were imported from various countries in 1981 and 1983. A. flavus was present in 128 kernels (46.5%) out of the tested 275 kernels of the other type edible nuts, in contrast to 49.6% infection of peanuts. A total of 91 isolates of A. flavus were selected and examined on their AF producibility; of 44 isolates of A. flavus from the other type edible nuts, 37 (84.1%) were shown to produce AF on defatted peanut meal medium, while 43 (91.5%) of 47 isolates of A. flavus from peanuts were positive. Most aflatoxigenic isolates from the other type edible nuts were identified as A. flavus subsp. flavus var. flavus, and 4 isolates of these, which were isolated from Hawaiian macadamia nut, produced high levels of AF G1 and G2 than those of AF B1 and B2. On the contrary, most isolates in the peanuts imported from U.S.A. produced AF B and G, and were identified as A. flavus subsp. parasiticus var. parasiticus. This survey revealed that the imported edible nuts including almond, chick-pea, hazelnut, macadamia nut and pistachio were significantly infected with aflatoxigenic A. flavus.
When the three kinds of trichothecene mycotoxins, T-2 toxin, deoxynivalenol and nivalenol, were applied to the surface of sliced sweet potato root tissues, the various antipathogenic furano-sesquiterpenes such as ipomeamaronol were accumulated in those tissues like in the black rot fungus (Ceratocystis fambriata)-infected ones. However, each mycotoxin induced the different amounts of furano-sesquiterpenes. T-2 toxin induced the most amount of furano-sesquiterpenes and nivalenol induced the least amount. The three kinds of trichothecene mycotoxins induced furano-sesquiterpenes at the different composition, though ipomeamaronol was commonly accumulated as a principal furano-sesquiterpene.
A total of 35 strains of Fusarium species were isolated from the scabby wheat grains harvested in Hokkaido which have been found to be contaminated with deoxynivalenol (DON), nivalenol (NIV) and zeralenone (ZEN), and were examined on their producibility of mycotoxins such as trichothecenes and ZEN.DON and/or ZEN-producers of Fusarium graminearum and NIV and/or ZEN-producers of F. poae were detected. This is the first finding that F. poae produces NIV in rice culture.
The effect of aflatoxin B1 (Af B1) on the cultured hepatocytes originated from either chick-embryos or rats was studied. Hepatocytes originated from male adult rats (mean body weight 150 g) were most sensitive to Af B1. In contrast, those from chick-embryos were about 1/1000 less sensitive than rat heptocytes to the mycotoxin. Microsomal fractions prepared from the livers of rats fed with PCB increased the sensitivity of chick-embryonal hepatocytes markedly. Fibroblasts isolated from 10 day-old chick-embryos were the most resistant to Af B1. From the results of present studies it may be postulated that enzymes of cytochrom-P-450 system may play an important role also in acute cytotoxicity.
We examined analytical method for rapidly determining deoxynivalenol (DON) and nivalenol (NIV) in cereals. Since we used a solvent of high polarity, water, a column of mixed alumina-charcoal-celite, and a column of amberlite for extraction and clean up, we were able to remove partition and dehydration processes. We determined mycotoxin by ECD-gas chromatography after trimethyl-silylation. We made the limits of detemination of DON and NIV at 12 ng/g. When DON and NIV were added to wheat and barley at 120 ng/g level, the recoveries were 101 and 95%, 93 and 92%, and the coefficients of variation were 2.9 and 3.4%, 3.7 and 2.4%, respectively. This method should also be applicable to the analysis of food and feed.
A simple and high sensitive enzyme-linked immunosorbent assay (ELISA) using mono-clonal antibody for quantitation of T-2 toxin (T-2) was developed and applied to analysis of wheat samples and screening of T-2-producing fungi. This ELISA did not require extensive cleanup steps before anlysis and a lot of sample could be analyzed at one time. The data were confirmed with GLC. The detection limit for T-2 was 0.1 ppb in the ELISA, and 100-fold sensitive than GC-MS.