| Summary: | Numerous investigations have shown that fumonisin B1 (FB1) is the causal agent in a range of animal toxicities, including leucoencephalomalacia, pulmonary oedema and renal and hepatic cancer in rats and mice. Fumonisin B1 has also been implicated in the aetiology of oesophageal cancer in South Africa. Human data are lacking, however, and the International Agency for Research on Cancer has accordingly classified this mycotoxin as a Type 2B carcinogen. This study investigated the ultrastructural effects of FB1 cytotoxicity on a human oesophageal carcinoma cell line (SNO). The pathological changes induced by FB1 were determined using transmission and scanning electron microscopy. Immunocytochemistry was used to immunolocalise FB1 (monoclonal anti-FB1) within the cells. The results showed marked pathological changes that included enlargement or microsegregation of the nucleus, microsegregation of the nucleolus, and swelling and elongation of mitochondria, as well as signs of membrane damage. These cytotoxic effects were associated with the action of FB1, since the toxin was internalised in nuclei, mitochondria and the cytoplasm of affected cells. This study shows that FB1 may exert its biological effects in SNO cells through binding to cellular macromolecules or membrane components within the affected organelles.
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