Studies on tetrodotoxin (TTX) are going to be developed to elucidate the TTX origin, the toxification mechanism in the TTX bearing animals and further their significance of the occurrence as the distribution is expanded in many animals. Although many marine bacteria including genus Vibrio are found to be capable of producing TTX and/or its derivatives, the toxification mechanism in TTX bearing animals, such as toxic puffer remains to be elucidated in near future.
The distribution and aflatoxin productivity of Aspergillus flavus in field soils in Kanagawa Prefecture were investigated. A, flavus was isolated from 13 samples (8.1%) out of 160 total soil samples collected in 13 municipalities. The population of A. flavus detected in the soil samples ranged from 10 to 1, 300 CFU/g of soil. Out of 19 isolates of A, flavus, 3 strains from 3 soil samples collected in Hadano, Tsukui and Fujisawa produced aflatoxins on rice. Four strains out of 19 additional strains re-isolated from a soil sample collected in Yokohama, in which the highest population (1, 300 CFU/g) of A. flavus was found, produced a detectable amount of aflatoxins B1 and B2 on coconut agar, peanut agar, peanuts and trilaurin-added rice, while did not produce on rice, yeast extract-sucrose broth and sucrose-low salts broth.
Chaetochromin A, a bis (naphtho-γ-pyrone) mycotoxin produced by Chaetomiur gracile was examined for the induction of mitochondrial swelling using isolated rat heart and liver mitochondria. Chaetochromin A induced a marked swelling of both heart and liver mito-chondria suspended in isotonic KCl or sucrose solution, implying a possibility of direct injurious action of chaetochromin A to mitochondria in vivo. The swelling was not induced by chaeto-chromin A in the presence of magnesium ion.
Chaetochromin A and related bis (naphtho-γ-pyrone) mycotoxins, cephalochromin and ustilaginoidin A, were examined for the injuring effects on mitochondrial respiration by using isolated rat liver mitochondria to gain insight into the molecular mechanism for their in vivo toxicity. These three mycotoxins were revealed to inhibit the ATP synthesis in mitochondria by uncoupling oxidative phosphorylation and depressing state 3 respriration of mitochondria, which may be closely concerned in their cytotoxicity and in vivo toxicity to animals. The correlation between the uncoupling effect of chaetochromin A and its induction of mitochondrial swelling is discussed.
The occurrence of deoxynivalenol (DON), nivalenol (NIV) and zearalenone (ZEN) was surveyed with domestic wheat, barley and wheat flours produced from domestic and imported wheat grains. Among the 31 samples examined, 4 wheat and 5 barley samples were positive for NW and 2 wheat samples were positive for DON. Neither ZEN nor multiple contamination of Fusarium toxins was detected in tested samples. Fusarium graminearum isolated from a wheat sample which was contaminated with NIV produced NIV on polished rice.
Chetomin was isolated from Chaetomium angustispirale, and chaetoviridin A and chaeto-globosin F were isolated from C. subafine. From C. longicolleum, three new related to aflatoxin biosynthesis, and eight known metabolites were isolated : the former were sterigmatocystin hemiacetal acetate (8), 1', 4'-diacetylversiconol (11) and 1'-acetylversiconol (13), and the latter were sterigmatocystin, averufin, versicolorin B, nidurufin, dihydrosterigmatocystin, sterigmatocystin hemiacetal, 4'-acetyl versiconol (versiconol acetate) and versiconol.
As observed previously in the conditioned medium (CM) of Kagura-2 cells, CM prepared from Kagura-1 cells, the another cell line of aflatoxin B1 (AFB1)-induced hepatoma, also contains very active neuronal differentiation factor(s) which convert PC12 cells to the sympathetic neuron-like cells. The factor(s) detected in Kagura-1 cell-CM are inactivated by heat, trypsin, acetic acid and dithiothreitol. Molecular weights of the factor (s) are ranging from 6, 000 to 14, 000 Da. These facts indicate that the factor(s) detected in Kagura-1 cell-CM are very similar or identical to those of Kagura-2 cells. In contrast, CM obtained from H4-II-E cells, one of the minimal deviation rat hepatomas, shows only slight activity for the neurite outgrowth of PC12 cells, although the cell extract contains the very active factor(s) as detected in those of AFB1-induced hepatomas. The synthetic activities of the factor(s) in Balb/3T3, 3Y1, IMR-32 and HeLa cells are negligible except for NRK cells. The present data strongly suggest that the neuronal differentiation factor(s) are constitu-tively produced in rat hepatoma cells involving the minimal deviation H4-II-E cells, and secreted extracellularly in the AFBI-induced hepatoma cell lines.