COVENIN 474 97 PDF

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Several biochemical reactions have been proposed to ocvenin all or some of the toxic effects of fumonisins in animals. Male rats were fed diets containing fumonisin B 1 at a concentration of 0. The increase was reversible. Although the results were not used for hazard characterization or risk assessment, when possible, the NOEL or LOEL was calculated for comparison with the results of studies with pure fumonisin B 1.

In a detailed study of the distribution of exogenous factors related to the differences in the incidence of oesophageal cancer 744 the Caspian littoral, no single causative agent could be identified.

Essential fatty acids are major constituents of all cell membrane glycerophospholipids, sphingolipids, and triglycerides. In this evaluation, only the consumption of contaminated maize or maize-containing food products was considered, as 744 contributions of other commodities to the intake of fumonisins are too low and too variable to affect overall long-term exposure significantly.

norma venezolana covenin 474 pdf

The brain lesions in rabbits and pigs could not be reproduced in subsequent studies T. The first proposed lipid-based mechanism involves inhibition of ceramide synthase, a key enzyme in the biosynthesis of sphingolipids reviewed extensively in WHO, a.

Specific non-covalent interactions were noted with fusaproliferin and beauvercin, two mycotoxins produced by F. Human peripheral T cells; frog oocytes Inhibition of Fas CD95 -induced proliferation, induction of oocyte maturation [0. At least 10 other Fusarium species also produce these toxins. Use of the presumed distribution of maize consumption, as in the second scenario, allows examination of fumonisin intake by people who consume larger amounts of maize over a lifetime as well as those who consume maize with higher concentrations of fumonisins in the long term.

This is demonstrated in numerous studies of the identify of cell processes mediated by ceramides Table 3. Selected biochemical mechanisms for the toxicity of fumonisin B 1 in vitro in models in which the proposed biochemical action has been shown to be related to specific molecular events or physiological or toxic effects.

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norma venezolana covenin pdf

Several mechanisms might be involved in the reduced concentrations of fumonisins in certain varieties, however. Fumonisins are fungi produced by fungi of the genus Fusarium. Wet milling is used to obtain products ocvenin as germ for oil and feed preparationfibres and gluten used in animal feedand starch for e. Oxidative damage and the resultant lipid peroxidation products may further enhance apoptosis in the liver Chen et al.

Generally, processed cobenin foods have lower concentrations and a lower frequency of contamination than untreated foods. The results obtained with a fibre-optic immunosensor in a direct competitive monoclonal antibody format with a fumonisin B 1 —fluorescein isothiocyanate conjugate compare favourably with those obtained with HPLC Maragos, Fungal contamination of maize and wheat attracted the interest fovenin many investigators, who have characterized the toxic, mutagenic, and carcinogenic metabolites of the major fungal contaminants of these grains.

However, in mice, fumonisin B 1 -induced liver toxicity occurred in the covfnin of evidence of increased lipid peroxidation Riley et al. Liver biopsy samples were collected from a subpopulation of the rats for another 6 months.

The chemical structures of fumonisin B 1fumonisin B 2fumonisin B 3and fumonisin B 4 are given in Figure 1. As ammoniation is known to detoxify aflatoxins, its effect on fumonisins was also studied.

In short-term studies with mice, rats, and rabbits, disruption of sphingolipid metabolism, as shown by statistically significant increases in the free sphinganine concentration, occurred at doses at or below those that cause liver or kidney lesions Table 1; for review, see Riley et al.

Chemical analyses of samples collected in this region showed little fumonisin contamination: Fumonisin B 1 2.

FUMONISINS (JECFA 47, )

Decreased glycosphingolipid-dependent cell adhesion, growth, altered cell morphology, or differentiation, and altered vitamin transport Disruption of fatty acid and phospholipid metabolism Primary cultures: Male mice showed no increase cocenin the incidence of neoplasia of any type, including the liver: Oxidative damage has been reported in Vero cells Abado-Becongnee et al. There was a concomitant increase in the cellular concentrations of phosphatidyl-choline and phosphatidylethanolamine, while the total cholesterol concentration decreased.

In a study in which lactating cows were given fumonisin B 1 intravenously, the carry-over rate into the milk reached a maximum of 0. Coveinn incidences were recorded in the western part of the Caspian littoral. Inverse relationship with molybdenum, manganese, zinc; no relationship with pickled vegetables Alcohol intake: Data for covenij years —70 in a cancer registry in Linxian County showed an average incidence rate of perwhile the lowest rates were recorded in Hunyan County 1.

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The performance characteristics of screening tests for fumonisins in maize, based on interlaboratory collaborative studies, have not been reported in the literature.

The diet in Linxian consisted mainly of maize, wheat, millet, rice, and some seasonal vegetables. The mean intake of fumonisin B was calculated to be equivalent covebin 0. The distributions representing variation and uncertainty were selected iteratively to form a two-dimensional array of estimates of the magnitude of harm to individuals and to the population as a whole.

Conversely, the balance between sphingosine 1-phosphate and ceramide is critical clvenin signalling proliferation or cell survival Spiegel, Hepatocyte nodules were induced when the fumonisin B covejin -fed rats were subjected to promotion by 2-acetylaminofluorene and partial hepatectomy Gelderblom et al.

Changes in the concentrations of specific polyunsaturated fatty acids were attributed to disruption of the Delta 6 desaturase and cyclo-oxygenase metabolic pathways. The dominant mycoflora in the sorghum were Aspergillus, Fusariumand Alternaria spp. Hepatocellular necrosis, periportal hypertrophy, diffuse centrilobular hyperplasia, Kupffer cell hyperplasia No lesions in any group 31 44 93 Females 99 24 All treated animals: The proportion of maize in each product consumed was estimated from standard recipes.

Another approach to the detoxication of fumonisin B 1 involves a reaction with fructose to block the amine group, which is critical for its toxicity. Fumonisin B 1 is the diester of propane-1,2,3-tricarboxylic cvenin and 2 S -amino S ,16 R -dimethyl- 3S ,5 R ,10 R ,14 S15R -pentahydroxyeicosane in which the C and C hydroxy groups are esterified with the terminal carboxy group of propane-1,2,3-tricarboxylic acid. These values were independent of the xovenin type B 1B 2B 3or total.