The neuronal differentiation factor secreted by aflatoxin B1 (AFB1)-induced rat hepatoma Kagura-2 cells induced the rapid transient expression of c-fos gene in PC 12 cells. The induction of acetylcholinesterase (AChE) activity in PC 12 cells by the factor is partially blocked by antibody against mouse 2.5S nerve growth factor (NGF), but not suppressed by basic fibroblast growth factor (bFGF) specific antibody. Western blot analysis and NGF specific antibody-Affigel 10 affinity chromatography of the conditioned medium of Kagura-2 cells (K2-CM) indicate that the factor is a 17 kDa protein. The expression of NGF, brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) mRNAs are hardly detected i n Kag ura-2 cells. Moreover, the factor promotes only neurite outgrowth of explanted newborn rat dorsal root ganglia (DRG). The present data suggest that the neuronal differentiation factor of Kagura-2 cells is a new neurotrophic factor related to NGF family.
To gain an insight into the growth regulation of Kagura-2 cells derived from aflatoxin B1 (AFB1)-induced rat hepatocellular carcinoma by glucocorticoid (GC), we analyzed the growth factors in the conditioned medium of Kagura-2 cells (K2-CM). Kagura-2 cells secrete at least three kinds of growth factors including a transforming growth factor-β (TGF-β)-like factor, a fibroblast growth factor (FGF)-like factor and an unknown inhibitory factor. Moreover, the inhibitory activity in K2-CM prepared in the presence of dexamethasone (DEX) tends to be lower than in that obtained in the absence of DEX. From these data, it is highly possible that GC-dependent growth of Kagura-2 cells is regulated through these stimulatory and inhibitory factors in an autocrine and/or a paracrine mechanism.
The occurrence of deoxynivalenol (DON) and nivalenol (NIV) was surveyed on domestic wheat and barley samples harvested in 1990 and 1991, and the 11 strains of Fusarium species were isolated from the tested samples and were examined on their producibility of mycotoxins such as DON and NIV. Among the 44 samples (27 of wheat and 17 of barley samples), 15 wheat and 14 barley samples were positive for NIV and 7 wheat samples and 8 barley samples were positive for DON, respectively. Multiple contamination of NIV and DON was detected on 6 wheat and 7 barley samples. Six isolates of Fusarium graminearum from 4 barley samples which had been contaminated with Fusarium toxins, produced NIV on polished rice culture.
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.