A crude water extract, U-3, of false smut balls on rice panicles caused by Ustilaginoidea virens and a purified crystal, ustiloxin, were injected to mice intraperitoneally. Single injection of U-3, 100 and 200 mg/kg b.w., caused acute necrosis of isolated hepatocytes and renal tubular cells followed by mitotic arrest and abnormal mitosis resembling that caused by colchicine. Serial injection for 10 days of as low as 3 and 6 mg/kg of U-3 and 400μg/kg of ustiloxin caused relatively mild but definite liver and kidney lesions as described above. Repeated injection of U-3 with 25 mg/kg induced, in addition to the lesions as above, ulcera-tion of the forestomach. These results imply a direct toxic effect of U-3 on the liver and kidney with subsequent mitotic injury of the whole body. These lesions were same as those observed in lupinosis caused by phomopsin A. Actually, the two substances have similar chemical structures.
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