Biomedical subjects
M Metche
Publications and source records attributed to M Metche.
Allergenicity of some isoforms of white sesame proteins.
BACKGROUND: Allergy to sesame seeds is often associated with particularly severe reactions, with a high risk of anaphylaxis. The increase in reports of allergic reactions to sesame is probably due to the growing use of sesame seeds or sesame oil in food. OBJECTIVE: To determine the molecular weights of the proteins in three variety of sesame seeds and to study the isoelectric points and the allergenicity of white sesame proteins. METHODS: Extracts of white, brown and black sesame seeds were prepared. The white sesame extract, mostly used in bakery, was run on SDS-PAGE and two dimensional electrophoresis. Six sera from patients sensitized or symptomatic to sesame seed were used for Western blotting. RESULTS: The protein patterns of the white, brown and black sesame extracts showed major quantitative differences. The white extract had the higher protein concentration and contained 15 proteins of 12-79 kDa, some of them having several acidic isoelectric points. The lowest isoelectric point was 4.9 and the highest was 6.4, giving 35 isoforms. Ten of the 15 proteins (12-57.5 kDa) were recognized by specific IgE. The 12-13 kDa and 22-33 kDa proteins could correspond to the main allergens. CONCLUSION: White sesame seeds contain at least 10 allergenic proteins with acidic isoelectric points. In accordance with previous results, two of them seem to contain the major allergens.
[Allergenicity of oils].
Cases of allergy to the oils of groundnut, sunflower, soya and sesame have been described in the literature. In parallel, other authors have affirmed that these oils are not allergenic. The objective of this article is to make the point on this question, to cite the procedures to which the seeds are submitted to extract the oil, to remember that the oils are not composed only of triglycerides and to describe the results of our work. Allergy of oils is a subject that is constantly submitted to controversy and the bibliography does not cease to give contradictory examples. This may be explained by the variations in extraction procedures used by the manufactures, as well as by the conditions of extraction of the proteins in the laboratory.
Influence of refining steps on trace allergenic protein content in sunflower oil.
BACKGROUND: Although allergy to sunflower seed and oil is a relatively rare occurrence, several cases of sunflower seed allergy have been observed, and we have already described one case of anaphylaxis after eating sunflower oil and margarine. OBJECTIVE: The aim of our study was to determine and characterize the allergens from sunflower oil at the different steps of the refining process: crude pressed oil (step A), acidification and neutralization (step B), pregumming by centrifugation (step C), washing (step D), bleaching (step E), gumming by filtration (step F), and deodorization (step G). METHODS: A sample of oil from each step of the process (steps A to G) was heat extracted with PBS. The protein concentration of each extract was evaluated by using the micro-Bradford assay. Samples were run on SDS-PAGE. The immunoblot was performed with the serum of a patient sensitized to sunflower seed and oil. RESULTS: The extracts obtained after each step reveal a decrease in total protein concentration from 13.6 microg/mL to 0. 22 microg/mL. The result of SDS-PAGE shows 5 bands, from 67 kd to 145 kd, with the most abundant being the 67-kd protein. The amount of this protein decreases after each step of the process. It is, however, still present in trace amounts in the refined oil. The 67-kd protein, which is mainly present in the crude oil and slightly in the refined oil, has been shown to be allergenic. CONCLUSION: Because of the presence of allergenic proteins, refined sunflower oil may pose a threat to people highly sensitized to sunflower seeds.
Degradation of cyanidin 3-glucoside by caffeic acid o-quinone. Determination of the stoichiometry and characterization of the degradation products.
Caffeic acid o-quinone (CQ) was prepared by oxidation of caffeic acid with o-chloranil in organic media. The reaction between the purified CQ and cyanidin 3-glucoside (Cy 3-glc, o-diphenolic anthocyanin) was monitored by HPLC, and quantitative analyses were performed to establish the stoichiometry of the reaction. The results indicate that Cy 3-glc is degraded by a coupled oxidation mechanism with integration of CQ into the degradation products. The ratio of degraded Cy 3-glc to CQ incorporated into the condensation products was approximately 2.0. No brown products could be detected, only a slight orange color. Moreover, the addition of purified polyphenol oxidase to the slightly colored media resulted in the disappearance of the caffeic acid formed from the reaction of coupled oxidation (Cy 3-glc/CQ) and the formation of brown polymers. The degradation products were isolated by gel filtration on Sephadex G-25. The UV-vis spectra and chemical analysis (acidic hydrolysis) of the degradation products suggest that they resulted from the condensation of caffeic acid and Cy 3-glc. HPLC analysis showed that the partial purified fraction contained a mixture of complex condensation products.
Quantitative determination of the polyphenolic content of pomegranate peel.
The quantitative determination of total phenols, ellagic tannins and gallic and ellagic acids in the peel of the Tunisian pomegranate variety Chelfi, has been carried out. The ellagic tannin content is prominently less than the amount of total phenols, which led us to look for the presence of the condensed tannins. The determination of the content of catechic tannins in eight Tunisian varieties of the pomegranate was carried out using weekly samples over a period of 2 months.
Purification and characterization of copper-metallothionein from Aspergillus niger by affinity chromatography.
Biomass of Aspergillus niger was obtained from a microbial culture and a copper (Cu) induction was performed after 72 h of fermentation. The crude induced metallothionein extract was obtained by cell disruption and partly purified by a heat treatment and ultrafiltration. The purification of metallothionein by affinity chromatography resulted in three major fractions: FIVa, FIVb and FIVc3. Cu analysis demonstrated that only fraction FIVc contained the Cu-metallothionein. Spectrophotometric analyses of FIVc demonstrated the presence of a peak at 259 nm and a ratio of 78 mol of Cu per mol of protein. Electrophoretic analyses of FIVc, performed under denaturing conditions, showed the presence of one band with molecular mass of 21 kDa; however, two isoforms were observed under native conditions with molecular masses of 9.5 and 10.5 kDa and isoelectric points of 6.2 and 6.5, suggesting a recombination process due to denaturation.
Regulation of the central metabolism in relation to citric acid production in Saccharomycopsis lipolytica.
The mechanism of the massive extracellular production of citric and isocitric acids by Saccharomycopsis lipolytica grown on n-paraffins has been studied. When growth stops, because of nitrogen limitation, the intracellular concentration of ATP sharply rises whereas that of AMP and ADP decreases to a low level. At the same time production of acids begins. The activity of the NAD-dependent isocitrate dehydrogenase which requires AMP for activity becomes very low and prevents the oxidative function of the citric acid cycle whereas isocitrate lyase is not inhibited. As citrate synthase inhibition by ATP appears to be insufficient to stop n-paraffin degradation, citric and isocitric acids accumulation can take place. Massive excretion of these acids, however, probably still involves other physiological changes brought about by nitrogen limitation, possibly some permeabilization of the cell to these acids.
[Microbiological transformation of quercetin by Aspergillus niger Van Tieghem].
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[Intermediary products in the autoxidation of quercetin].
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