The chronoamperometric and voltammetric behaviour of glutathione at screen-printed carbon micro-band electrodes modified with cobalt phthalocyanine

Screen-printed carbon electrodes (SPCEs) incorporating the electrocatalyst cobalt phthalocyanine (CoPC) have been successfully used for the manufacture of microband electrodes for the determination of reduced glutathione (GSH). Initially investigations were performed to explore the cyclic voltammetric behaviour of these electrodes with potassium ferrocyanide. It was shown that steady state behaviour occurred which is indicative of radial diffusion at a microelectrode. Current densities of 2173 μAcm-2 were obtained compared to 464.4 μAcm-2 for conventional sized (3 mm x 3 mm) screen-printed electrodes were obtained. At scan rates between 5 and 20 mV/s no significant increase in current response was observed. The application of these microband CoPC–SPCEs, to the measurement of GSH by both chronoamperometry and cyclic voltammetry was investigated. The chronoamperometric response was found to be linear between 50 µM and 8.0 mM with a detection limit of 7.3 µM using an applied potential of +0.25 V (vs. Ag/AgCl)

Electrochemical detection of benzodiazepines, following liquid chromatography, for applications in pharmaceutical, biomedical and forensic investigations

Benzodiazepines are an important class of drugs commonly administered with a potential for abuse and environmental pollution. This review focuses on the liquid chromatographic electrochemical detection of the benzodiazepine class of drugs. These are characterised by a readily electrochemically reducible azomethine group, with a number also substituted by other electrochemically active groups. Liquid chromatography employing both single and dual electrode detection has been reported for a variety of benzodiazepines and their metabolites in biological, pharmaceutical, biomedical and forensic investigations. Recently, electrochemistry has been utilised to mimic biological oxidation processes and has been combined with liquid chromatography/mass spectroscopy for their identification and quantification of the products generated. The present review focuses on recent developments in liquid chromatographic- electrochemical determination of benzodiazepines reported since 2006, with earlier reports given in summary

Increasing β-catenin/Wnt3A activity levels drive mechanical strain-induced cell cycle progression through mitosis.

Mechanical force and Wnt signaling activate β-catenin-mediated transcription to promote proliferation and tissue expansion. However, it is unknown whether mechanical force and Wnt signaling act independently or synergize to activate β-catenin signaling and cell division. We show that mechanical strain induced Src-dependent phosphorylation of Y654 β-catenin and increased β-catenin-mediated transcription in mammalian MDCK epithelial cells. Under these conditions, cells accumulated in S/G2 (independent of DNA damage) but did not divide. Activating β-catenin through Casein Kinase I inhibition or Wnt3A addition increased β-catenin-mediated transcription and strain-induced accumulation of cells in S/G2. Significantly, only the combination of mechanical strain and Wnt/β-catenin activation triggered cells in S/G2 to divide. These results indicate that strain-induced Src phosphorylation of β-catenin and Wnt-dependent β-catenin stabilization synergize to increase β-catenin-mediated transcription to levels required for mitosis. Thus, local Wnt signaling may fine-tune the effects of global mechanical strain to restrict cell divisions during tissue development and homeostasis

Spatial distribution of cell-cell and cell-ECM adhesions regulates force balance while main-taining E-cadherin molecular tension in cell pairs.

Mechanical linkage between cell-cell and cell-extracellular matrix (ECM) adhesions regulates cell shape changes during embryonic development and tissue homoeostasis. We examined how the force balance between cell-cell and cell-ECM adhesions changes with cell spread area and aspect ratio in pairs of MDCK cells. We used ECM micropatterning to drive different cytoskeleton strain energy states and cell-generated traction forces and used a Förster resonance energy transfer tension biosensor to ask whether changes in forces across cell-cell junctions correlated with E-cadherin molecular tension. We found that continuous peripheral ECM adhesions resulted in increased cell-cell and cell-ECM forces with increasing spread area. In contrast, confining ECM adhesions to the distal ends of cell-cell pairs resulted in shorter junction lengths and constant cell-cell forces. Of interest, each cell within a cell pair generated higher strain energies than isolated single cells of the same spread area. Surprisingly, E-cadherin molecular tension remained constant regardless of changes in cell-cell forces and was evenly distributed along cell-cell junctions independent of cell spread area and total traction forces. Taken together, our results showed that cell pairs maintained constant E-cadherin molecular tension and regulated total forces relative to cell spread area and shape but independently of total focal adhesion area

Novel reductive-reductive mode electrochemical detection of Rohypnol following liquid chromatography and its determination in coffee

© 2014 Elsevier B.V. Rohypnol (flunitrazepam) has been successfully determined in coffee by high performance liquid chromatography dual electrode detection (LC-DED) in the dual reductive mode. Initial studies were performed to optimise the chromatographic conditions and these were found to be 50% acetonitrile, 50% 50mM pH 2.0 phosphate buffer at a flow rate of 0.75mLmin-1, employing a Hypersil C18, 5μm, 250mm×4.6mm column. Cyclic voltammetric studies were made to ascertain the redox behaviour of Rohypnol at a glassy carbon electrode over the pH range 2-12. Hydrodynamic voltammetry was used to optimise the applied potential at the generator and detector cells; these were identified to be -2.4V and +0.8V for the redox mode and -2.4V and -0.1V for the dual reductive mode respectively. A linear range of 0.5-100μgmL-1, with a detection limit of 20ngmL-1 was obtained for the dual reductive mode. Further studies were then performed to identify the optimum conditions required for the LC-DED determination of Rohypnol in beverage samples. A convenient and rapid method for the determination of Rohypnol in beverage samples was developed using a simple sample pre-treatment procedure. A recovery of 95.5% was achieved for a sample of white coffee fortified at 9.6μgmL-1 Rohypnol

CAP Reform and the WTO: Potential Impacts on EU Agriculture

Selected Paper prepared for presentation at the American Agricultural Economics Association Annual Meeting, Denver, Colorado.In 2003 an agreement was finalized to instigate arguably the most significant reform of the European Union's (EU) Common Agricultural Policy (CAP) since its inception. In the Luxembourg Agreement many of the direct payments that have been linked to production are decoupled and instead provided in the form of a land-based payment. The reforms did not include any significant changes to either EU border support or the ability of the EU to utilize export subsidies that have been widely criticized by other nations. Even though the reforms do not directly address trade in agricultural products it is argued that World Trade Organization (WTO) concerns played a significant role in the designs of the reforms. In this paper an analysis of the Luxembourg reforms and the European proposal for agriculture under the WTO is presented. The results are used as the basis for a discussion of the interaction of the WTO and CAP reform and the implications for the agricultural sector in the EU

Evaluation of sense-strand mRNA amplification by comparative quantitative PCR

BACKGROUND: RNA amplification is required for incorporating laser-capture microdissection techniques into microarray assays. However, standard oligonucleotide microarrays contain sense-strand probes, so traditional T7 amplification schemes producing anti-sense RNA are not appropriate for hybridization when combined with conventional reverse transcription labeling methods. We wished to assess the accuracy of a new sense-strand RNA amplification method by comparing ratios between two samples using quantitative real-time PCR (qPCR), mimicking a two-color microarray assay. RESULTS: We performed our validation using qPCR. Three samples of rat brain RNA and three samples of rat liver RNA were amplified using several kits (Ambion messageAmp, NuGen Ovation, and several versions of Genisphere SenseAmp). Results were assessed by comparing the liver/brain ratio for 192 mRNAs before and after amplification. In general, all kits produced strong correlations with unamplified RNAs. The SenseAmp kit produced the highest correlation, and was also able to amplify a partially degraded sample accurately. CONCLUSION: We have validated an optimized sense-strand RNA amplification method for use in comparative studies such as two-color microarrays

Measurement errors in body size of sea scallops (Placopecten magellanicus) and their effect on stock assessment models

Body-size measurement errors are usually ignored in stock assessments, but may be important when body-size data (e.g., from visual sur veys) are imprecise. We used experiments and models to quantify measurement errors and their effects on assessment models for sea scallops (Placopecten magellanicus). Errors in size data obscured modes from strong year classes and increased frequency and size of the largest and smallest sizes, potentially biasing growth, mortality, and biomass estimates. Modeling techniques for errors in age data proved useful for errors in size data. In terms of a goodness of model fit to the assessment data, it was more important to accommodate variance than bias. Models that accommodated size errors fitted size data substantially better. We recommend experimental quantification of errors along with a modeling approach that accommodates measurement errors because a direct algebraic approach was not robust and because error parameters were diff icult to estimate in our assessment model. The importance of measurement errors depends on many factors and should be evaluated on a case by case basis