Evaluation of sulfur isotopic enrichment of urine metabolites for the differentiation of healthy and prostate cancer mice after the administration of 34S labelled yeast.

Sulfur isotopic enrichment of urine metabolites in healthy and prostate cancer mice using 34S enriched yeast and High Performance Liquid Chromatography coupled to Multicollector Inductively Coupled Plasma Mass Spectrometry (HPLC-MC-ICP-MS) has been evaluated. A 30 weeks experiment (since the eleventh to the fortieth week of life) was carried out collecting the urine of three healthy mice and three transgenic mice with prostate cancer during 24h after a single oral administration of a 34S enriched yeast slurry. The isotopic enrichment of different sulphur metabolites was monitored by coupling a C18 reverse phase HPLC column with a multicollector ICP-MS using a membrane desolvating system. Quantification of sulfur in the chromatographic peaks was carried out by post-column isotope dilution using a 33S enriched spike. Differences between the 34S enrichment in the urine metabolites of healthy and prostate cancer mice were found from the beginning of the disease. Both populations could be differentiated using a principal component analysis (PCA). Finally, 7 unknown mice were correctly classified in each population using a linear discriminant analysis.

Expression of the cry11A gene of Bacillus thuringiensis ssp. israelensis in Saccharomyces cerevisiae.

The complete cry11A region gene of Bacillus thuringiensis ssp. israelensis was fused in frame to the 3' end of the GST gene under the control of the Saccharomyces cerevisiae HXK1 promoter. The fusion protein GST-cry11A was expressed in S. cerevisiae strain AMW13C+. The fusion gene GST-cry11A was expressed when yeast cells were grown on galactose and a nonfermentable medium containing ethanol as carbon and energy source. When the cells were grown in glucose, mannose, fructose, or glycerol as carbon sources, the GST-cry11A gene was repressed. Thus, a regulated expression in accordance with the regulatory activity of the HXK1 gene promoter has been detected. The GST-cry11A fusion protein was detected in the transformed yeasts as a soluble protein. The fusion protein was purified by affinity chromatography using glutathione-Sepharose beads. Cell-free extracts from transformed yeasts grown in ethanol-containing culture media showed insecticidal activity against third-instar Aedes aegypti larvae. This insecticidal activity was increased about 4-fold when the purified fusion protein was assayed.