Physical and immunoaffinity extraction of paralytic shellfish poisoning toxins from cultures of the dinoflagellate Alexandrium tamarense

In the present study the extraction of paralytic shellfish poisoning (PSP) toxins from a toxic strain of the marine dinoflagellate Alexandrium tamarense CCMP-1493 using various mechanical and/or physical procedures was investigated. PBS buffer was investigated as the extraction solvent in order for these procedures to be used directly with immuno-magnetic Ferrospheres-N. The extraction was performed following the determination of when toxin content by the algae was at its highest during batch culture. The methods used for cell lysis and toxin extraction included freeze-thawing, freeze-boiling, steel ball bearing beating, glass bead beating, and sonication. The steel ball bearing beating was determined to release a similar amount of toxin when compared to a modified standard extraction method which was reported to release 100% of toxins from the algal cells and was therefore used in the next phase of the study. This next phase was to determine the feasibility of utilising an antibody coupled to novel magnetic microspheres (Ferrospheres-N) as a simple, rapid immune-capture procedure for PSP toxins extracted from the algae. The effects of increasing mass of Ferrospheres-N on the immuno-capture of the PSP toxins from the toxic algal strain extracts were investigated. Toxin recovery was found to increase when an increasing mass of Ferrospheres-N was used until 96.2% (+/- 1.3 SD) of the toxin extracted from the cells was captured and eluted. Toxin recovery was determined by comparison to an appropriate PSP toxin standard curve following analysis by the AOAC HPLC method. (C) 2011 Elsevier B.V. All rights reserved.

Comparison of the efficiences of enzymatic and chemical hydrolysis of (nortestosterone and diethylstilboestrol) glucuronides in bovine urine

Residues of 19-nortestosterone (19-NT) and diethylstilboestrol (DES) are excreted in bovine urine, mainly conjugated to glucuronic acid. Prior to quantification, urine must be deconjugated, which is commonly performed by enzymatic or chemical hydrolysis. The efficiencies of two enzymatic and two chemical deconjugation methods were studied. The range of efficiencies obtained for DES were 51.8% (beta -glucuronidase, incubation at 37 degreesC overnight) and 2.7% (methanolic HCl), respectively. Similarly, efficiencies for NT ranged from 43.1% (beta -glucuronidase, incubation at 55 degreesC for 2 h) to 12.7% (methanolic HCl). The results highlight that within control laboratories significant underestimation of drug residue content in samples may occur, due to poor deconjugation. (C) 2001 Elsevier Science B.V. All rights reserved.

Selective Orthosteric Free Fatty Acid Receptor 2 (FFA2) Agonists IDENTIFICATION OF THE STRUCTURAL AND CHEMICAL REQUIREMENTS FOR SELECTIVE ACTIVATION OF FFA2 VERSUS FFA3

Free fatty acid receptor 2 (FFA2; GPR43) is a G protein-coupled seven-transmembrane receptor for short-chain fatty acids (SCFAs) that is implicated in inflammatory and metabolic disorders. The SCFA propionate has close to optimal ligand efficiency for FFA2 and can hence be considered as highly potent given its size. Propionate, however, does not discriminate between FFA2 and the closely related receptor FFA3 (GPR41). To identify FFA2-selective ligands and understand the molecular basis for FFA2 selectivity, a targeted library of small carboxylic acids was examined using holistic, label-free dynamic mass redistribution technology for primary screening and the receptor-proximal G protein [S-35] guanosine 5'-(3-O-thio) triphosphate activation, inositol phosphate, and cAMP accumulation assays for hit confirmation. Structure-activity relationship analysis allowed formulation of a general rule to predict selectivity for small carboxylic acids at the orthosteric binding site where ligands with substituted sp(3)-hybridized alpha-carbons preferentially activate FFA3, whereas ligands with sp(2)- or sp-hybridized alpha-carbons prefer FFA2. The orthosteric binding mode was verified by site-directed mutagenesis: replacement of orthosteric site arginine residues by alanine in FFA2 prevented ligand binding, and molecular modeling predicted the detailed mode of binding. Based on this, selective mutation of three residues to their non-conserved counterparts in FFA3 was sufficient to transfer FFA3 selectivity to FFA2. Thus, selective activation of FFA2 via the orthosteric site is achievable with rather small ligands, a finding with significant implications for the rational design of therapeutic compounds selectively targeting the SCFA receptors.

Perfluorocarbons and semifluorinated alkanes

The introduction of perfluorocarbons (PFCs) and, more recently, semifluorinated alkanes (SFAs) has greatly facilitated vitreoretinal surgery. A distinction is made between the use of these substances as intraoperative tools and internal tamponade agents. This article reviews the physical and chemical properties of PFCs and SFAs and discusses the indications, results, and complications. The effectiveness of these substances as internal tamponade agents is discussed with reference to the specific gravity, contact angle, viscosity and ability to fill model eye chambers and the vitreous cavity. The evidence for the toxicity in animal and human is examined. Copyright (C) 2000 by W.B. Saunders Company.

Examination of the physical and psychosocial determinants of health behaviour in 4-5-year-old children with congenital cardiac disease

To assess the general health and activity levels of 4- and 5-year-old children after intervention for congenital cardiac disease.

Biosensors for the analysis of microbiological and chemical contaminants in food

Increases in food production and the ever-present threat of food contamination from microbiological and chemical sources have led the food industry and regulators to pursue rapid, inexpensive methods of analysis to safeguard the health and safety of the consumer. Although sophisticated techniques such as chromatography and spectrometry provide more accurate and conclusive results, screening tests allow a much higher throughput of samples at a lower cost and with less operator training, so larger numbers of samples can be analysed. Biosensors combine a biological recognition element (enzyme, antibody, receptor) with a transducer to produce a measurable signal proportional to the extent of interaction between the recognition element and the analyte. The different uses of the biosensing instrumentation available today are extremely varied, with food analysis as an emerging and growing application. The advantages offered by biosensors over other screening methods such as radioimmunoassay, enzyme-linked immunosorbent assay, fluorescence immunoassay and luminescence immunoassay, with respect to food analysis, include automation, improved reproducibility, speed of analysis and real-time analysis. This article will provide a brief footing in history before reviewing the latest developments in biosensor applications for analysis of food contaminants (January 2007 to December 2010), focusing on the detection of pathogens, toxins, pesticides and veterinary drug residues by biosensors, with emphasis on articles showing data in food matrices. The main areas of development common to these groups of contaminants include multiplexing, the ability to simultaneously analyse a sample for more than one contaminant and portability. Biosensors currently have an important role in food safety; further advances in the technology, reagents and sample handling will surely reinforce this position.

Physical and numerical constraints in source modeling for finite difference simulation of room acoustics

In finite difference time domain simulation of room acoustics, source functions are subject to various constraints. These depend on the way sources are injected into the grid and on the chosen parameters of the numerical scheme being used. This paper addresses the issue of selecting and designing sources for finite difference simulation, by first reviewing associated aims and constraints, and evaluating existing source models against these criteria. The process of exciting a model is generalized by introducing a system of three cascaded filters, respectively, characterizing the driving pulse, the source mechanics, and the injection of the resulting source function into the grid. It is shown that hard, soft, and transparent sources can be seen as special cases within this unified approach. Starting from the mechanics of a small pulsating sphere, a parametric source model is formulated by specifying suitable filters. This physically constrained source model is numerically consistent, does not scatter incoming waves, and is free from zero- and low-frequency artifacts. Simulation results are employed for comparison with existing source formulations in terms of meeting the spectral and temporal requirements on the outward propagating wave.