The positive Fast Atom Bombardment (FAB) tandem mass spectrometry as an effective technique was applied for identification and confirmation of 20 mycotoxins such as aflatoxins B1, B2, G1 and G2, and sterigmatocystin and its related toxins. The f ab ms/ms technique demonstrated to be a good method for analyzing these mycotoxins with less than one microgram. It resolved complex mixture of mycotoxins even with the same molecular weight.
A mycotoxicological survey on soil-borne Emericella collected from 369 soil samples from 10 areas in Brazil, Colombia, Paraguay and Venezuela, was carried out. Emericella spp. were isolated by using soil-plate method on Czapek's agar, incubating the plates at 37°C for 14 days. A higher occurrence of Emericella spp. was generally demonstrated in the soil samples of grassland and wasteland, which were collected from Botucatu in Brazil, Cartagena in Colombia, and Coro and Merida in Venezuela. The Emericella isolates were identified with E. acristata, E. dentata, E. echinulata, E. nidulans var. lata, E. nidulans var. nidulans, E. quadrilineata and E. rugulosa. For the 61 isolates assigned to 6 species and one variety of Emericella, the ability to produce sterigmatocystin (STG) and its related metabolites, such as norsolorinic acid and versicolorins, was examined on rice cultures at 25°C for 21 days. Moldy rice was extracted with ethyl acetate, and STG and its related metabolites in the extracts were confirmed by thin-layer chromatography. As the results, the following STG producers were found: E. acristata, E. dentata, E. echinulata, E. nidulans var. lata, E. nidulans var. nidulans, E. quadrilineata and E. rugulosa. The production of norsolorinic acid and versicolorin B and/or C was confirmed on the following species: E. acristata, E. dentata, E. nidulans var. lata, E. nidulans var. nidulans, E. quadrilineata and E. rugulosa. The norsolorinic acid production of Emericella spp. has been demonstrated for the first time.
To evaluate the safety of imported cereals in 1988 for mycotoxin contamination, the survey of 18 samples of buckwheat from the U.S.A., Canada and China, and 20 samples of wheat from the U.S.A. and Canada was carried out on mycotoxin analyses (aflatoxins for the buckwheat, and nivalenol and deoxynivalenol for the wheat, respectively), fungal infection, germinability and water activity (aw). None of the buckwheat samples showed aflatoxin contamination, but 8 samples of the wheat were positive for nivalenol and/or deoxynivalenol with the levels of trace to 40 μg/kg. Major isolates of fungi from the buckwheat and the wheat samples were Alternaria spp. as one of the common field fungi. Only a few storage fungi such as Eurotium spp. and Aspergillus flavus (non-aflatoxigenic) were detected but the level of their frequency occurrence was very low. The aw ranges of the samples were 0.4 to 0.7, mostly less than aw minima (0.65-0.70) for growth of the common storage fungi. Results of these examinations substantiate the need for : (1) implementing a routine moni-taring system for the Fusarium toxins in imported cereals, especially in wheat, and (2) properly controlling water contents of the post-imported cereals.
The effects of aflatoxin B1 (af B1) on hepatocytes of fetus and suckling rats were studied electron microscopically. Until 4-day-old, of B1 did not cause any discernible change in the hepatocyte nucleoli. A decrease of the relative size of the nucleoli first appeared at the age of day 6. During the first 4 days after birth, the quantity of SER as well as RER in the hepatocytes was less than that of the adult hepatocytes. Therefore, it may be postulated that the sensitivity of premature hepatocytes to af B1 is closely related with the development of SER and RER.
In order to investigate whether the dietary NIV modulates the development of carcinogenesis, one week old C57BL/C3H F1 mice were treated with a single i.p. injection of 6 mg/kg of AFB1, and 6 weeks thereafter the diets containing 0, 6 or 12 ppm NIV were fed for 65 weeks. All the male mice i. p. injected with AFB1 developed liver tumor, and that incidence was not altered by feeding of NIV-containing diet. While in the female, the incidence of hepatic tumor in the control, AFB1 alone, AFB1 6 or 12 ppm NIV groups counted for 0, 31, 20 and 0%, respectively. These findings suggested that NIV possesses an ability to depress the incidence of AFB1-initiated hepatocellular carcinogenesis at the promotion stage in female mice.