Nitrate Determination by a Modified Conway Microdiffusion Method

The proposed modified Conway microdiffusion method provides for consecutive determinations of NH?- and NO?-N in a given aliquot of soil extract. Analyses of primary nitrate standards showed essentially complete recovery in the range of 1 to 20 ppm NO?-N (4 to 80 µg N/aliquot). Results for (NH? + NO?)-N and NO?-N in soil extracts are comparable to those obtained, respectively, by macrodistillation with Devarda's alloy and by the phenoldisulfonic acid colorimetric method. The method is rapid and suitable for routine analyses of soil extracts, the equipment is inexpensive, and no interferences are apparent

Nitrate Determination by a Modified Conway Microdiffusion Method

The proposed modified Conway microdiffusion method provides for consecutive determinations of NH?- and NO?-N in a given aliquot of soil extract. Analyses of primary nitrate standards showed essentially complete recovery in the range of 1 to 20 ppm NO?-N (4 to 80 µg N/aliquot). Results for (NH? + NO?)-N and NO?-N in soil extracts are comparable to those obtained, respectively, by macrodistillation with Devarda's alloy and by the phenoldisulfonic acid colorimetric method. The method is rapid and suitable for routine analyses of soil extracts, the equipment is inexpensive, and no interferences are apparent

Agents used for chemoprevention of prostate cancer may influence PSA secretion independently of cell growth in the LNCaP model of human prostate cancer progression

BACKGROUND: The aim of this study was to evaluate the inhibitory growth effects of different potential chemopreventive agents in vitro and to determine their influence on PSA mRNA and protein expression with an established screening platform. METHODS: LNCaP and C4-2 cells were incubated with genistein, seleno-L-methionine, lycopene, DL-alpha-tocopherol, and trans-beta-carotene at three different concentrations and cell growth was determined by the MTT assay. PSA mRNA expression was assessed by quantitative real-time RT-PCR and secreted PSA protein levels were quantified by the microparticle enzyme immunoassay. RESULTS: Genistein, seleno-l-methionine and lycopene inhibited LNCaP cell growth, and the proliferation of C4-2 cells was suppressed by seleno-L-methionine and lycopene. PSA mRNA expression was downregulated by genistein in LNCaP but not C4-2 cells. No other compound tested altered PSA mRNA expression. PSA protein expression was downregulated by genistein, seleno-L-methionine, DL-alpha-tocopherol in LNCaP cells. In C4-2 cells only genistein significantly reduced the secretion of PSA protein. CONCLUSIONS: In the LNCaP progression model PSA expression depends on the compound, its concentration and on the hormonal dependence of the cell line used and does not necessarily reflect cell growth or death. Before potential substances are evaluated in clinical trials using PSA as a surrogate end point marker, their effect on PSA mRNA and protein expression has to be considered to correctly assess treatment response by PSA