Browsing by Author "Thiel, Pieter G"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Open Access
    The biological properties of three trichothecene mycotoxins produces by fusaris
    (1986) Janse Van Rensburg, Daniel Francois; Thiel, Pieter G; Ivanetich, Kathryn M
    The highly toxic fungal metabolite, neosolaniol monoacetate, was isolated and purified from cultures of Fusarium sambucinum. Since little is known about its toxic properties, the biological effects of this trichothecene were compared to those caused by diacetoxy-scirpenol in male Wistar rats. The lesions caused by the two toxins were very similar. Chronic exposure to either toxin led to a significant decrease (P<0.05) in red blood cell counts and a significant increase (P<0.05) in platelet size. The major pathological lesions observed were atrophy of the actively dividing cells of the bone marrow, thymus, spleen and lymph nodes. The reported species difference in T-2 toxin toxicity was investigated by determining the deacylation rate of T-2 toxin to HT-2 toxin, one of the first steps in the detoxification of this trichothecene. The high deacylation rate catalysed by rat microsomes correlated with the low sensitivity of this species to T-2 toxin, whereas the low deacylation rates with cat and monkey microsomes agreed with their high sensitivity. In contrast to this, the apparently high toxicity of T-2 toxin to humans does not correlate with the high deacylation rate observed in human hepatic microsomes. Involvement of the UDP-glucuronyltransferases in the detoxification of T-2 toxin was studied with rat and pig hepatic microsomes. T-2 toxin and two of its metabolites, HT-2 toxin and T-2 tetraol, did not appear to act as substrates for these enzymes under the in vitro conditions used.
  • Thumbnail Image
    Item
    Open Access
    Fumonisins : chromatographic methodology and their role in human and animal health
    (1994) Sydenham, Eric William; Koch, Klaus R; Thiel, Pieter G
    The fumonisins consist of a group of 7 structurally related mycotoxins originally isolated from Fusarium moniliforme, a fungal contaminant of maize worldwide. The incidence of F. moniliforme in home-grown maize, has been associated with human oesophageal cancer (OC) risk in the Transkei and China. Fumonisin B₁ (FB₁), the major fumonisin analogue, exhibits both cancer-initiating and -promoting activities, and has been shown to induce a number of disease syndromes in different animal species. Two other fumonisin analogues, fumonisins B₂ (FB₂) and B₃ (FB₃) also exhibit cancer-initiating potentials, similar to those observed for FB₁. A method, developed at PROMEC, for the analytical determination of FB₁ and FB₂ in maize, based on ion-exchange purification of crude extracts, derivatisation, reversed-phase liquid chromatography separation and fluorescence detection, was subjected to an international collaborative study involving 11 laboratories from 6 countries. Although the results established that the method was highly reproducible, alterations were made in order to reduce analysis time, identify and eliminate potential sources of error and include the co-determination of FB₃. Both methods were used, in conjunction with confirmatory techniques, to determine the extent of animal and human exposure to the fumonisins. Naturally occurring fumonisin levels in animal feeds, were used in conjunction with hazard assessment data, to establish fumonisin tolerance guidelines for selected animal species. The results indicated that combined fumonisin concentrations in feeds of 10 and 100 μg/g (ppm) should be regarded as potentially harmful to horses and swine, respectively. Human exposure assessment was based on data from various sources, including the 1989 and 1990 South African maize crops, maize imported into South Africa, retail maize-based foods from 14 countries, and home-grown maize from the Transkei. The data indicated that fumonisin contamination occurs worldwide, while the levels to which populations are exposed differ considerably. A statistical association was established between fumonisin contamination of home-grown maize, and the prevalence of human OC in the Transkei, where humans can be exposed to fumonisin levels that would be deemed harmful to both horses and swine.