Reduction of food matrix interference by a combination of sample preparation and multi-dimensional gating techniques to facilitate rapid, high sensitivity analysis for Escherichia coli serotype O157 by flow cytometry

Escherichia coli serotype O157 strains, which may be found in foods, often produce enterohemorrhagic toxins. The research goal was to facilitate rapid, sensitive detection in foods of E. coli serotype O157 by flow cytometry. Sample preparation methods were developed for potential use in 15 foods. Combined with multi-dimensional gating, these methods decreased time-to-results (TTR) for determination of low-level contamination. They mitigated the effects of interfering food components, concentrated cells for analysis without growth or, when necessary, used short-term incubation. The results showed qualitative analysis that was equivalent to culture plating in accuracy and superior in sensitivity and speed. Preparation time was 10–30 min per sample and detection took 3–4 min. Culture growth, if required, took an additional 4–6 h. A protocol for raw spinach analysis, using 4 h culture incubation, was 94% correct with one false negative for a low level inoculation. Its projected limit-of-detection (LOD) was 1 viable cell per 25 g of spinach, based on an average of 28 counts detected after growth and an estimated counts-to-threshold (C/T) ratio of 1.3. The results suggested potential uses for regulatory screening and food industry process control.     

Development of a rheological prediction model for food suspensions and emulsions

The rheological behavior of 34 commercial food dispersions was investigated and modeled with the Herschel–Bulkley model. Artificial neuronal networks (ANNs) were trained to predict the rheological parameters yield stress τ₀, consistency coefficient K and flow behavior index n in dependency of the composition of fats, carbohydrates, proteins and water. ANNs with 3 hidden layers and 2 neurons per layer showed good to very good results for all Herschel–Bulkley parameters.     

Nanoparticle Network Formation in Nanostructured and Disordered Block Copolymer Matrices

Incorporation of nanoparticles composed of surface-functionalized fumed silica (FS) or native colloidal silica (CS) into a nanostructured block copolymer yields hybrid nanocomposites whose mechanical properties can be tuned by nanoparticle concentration and surface chemistry. In this work, dynamic rheology is used to probe the frequency and thermal responses of nanocomposites composed of a symmetric poly(styrene-b-methyl methacrylate) (SM) diblock copolymer and varying in nanoparticle concentration and surface functionality. At sufficiently high loading levels, FS nanoparticle aggregates establish a load-bearing colloidal network within the copolymer matrix. Transmission electron microscopy images reveal the morphological characteristics of the nanocomposites under these conditions.     

Biosynthesis and spectroscopic characterization of 2-TM fragments encompassing the sequence of a human GPCR, the Y4 receptor

This paper presents a divide‐and‐conquer approach towards obtaining solution structures of G protein‐coupled receptors. The human Y4 receptor was dissected into two to three transmembrane helix fragments, which were individually studied by solution NMR. We systematically compared various biosynthetic routes for the expression of the fragments in Escherichia coli and discuss purification strategies. In particular, we have compared the production of transmembrane (TM) fragments as inclusion bodies by using the ΔTrp leader sequence, with membrane‐directed expression by using Mistic as the fusion partner, and developed methods for enzymatic cleavage. In addition, direct expression of two‐TM fragments into inclusion bodies is a successful route in some cases. With the exception of TM13, we could produce all fragments in isotope‐labeled form in quantities sufficient for NMR studies. Almost complete backbone resonance assignment was obtained for the first two helices, as well as for helices 5 and 7, and a high degree was obtained for TM6, while conformational exchange processes resulted in the disappearance of many signals from TM4. In addition, complete assignments were obtained for all residues of the N‐terminal domain, as well as the extracellular and cytosolic loops (with the exception of an undecapeptide segment in the second extracellular loop, EC2) and for the complete cytosolic C‐terminal tail. In total, backbone resonances of 78 % of all residues were assigned for the Y4 receptor. Predictions of secondary structure based on backbone chemical shifts indicate that most residues from the TM regions adopt helical conformations, with exception of those around polar residues or prolines. However, the domain boundaries differ slightly from those predicted for homology models. We suggest that the obtained chemical shifts might be useful in assigning the full‐length receptor.     

Validation of a contemplation ladder in an adult substance use disorder sample.

Developing brief measures of motivation to abstain from substance use that reliably predict treatment retention and outcome is a high priority in the addiction field. This study examined the psychometric properties of a contemplation ladder designed to assess readiness to abstain from alcohol and drug use respectively, on the basis of the contemplation ladder for smoking cessation developed by Biener and Abrams (1991). Participants were 394 substance-using male and female welfare recipients referred for treatment. The combined alcohol and other drug (AOD) ladder showed discriminant validity with demographic and health characteristics, convergent validity with conceptually related treatment motivation variables, concurrent validity with baseline AOD treatment and substance use variables, and predictive validity for participation in treatment services up to 1 month later and abstinence outcomes up to 1 year later. The AOD ladder showed predictive validity for those in drug-free treatment and no treatment at baseline but not for those in methadone maintenance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Smokeless tobacco reduction: preliminary study of tobacco-free snuff versus no snuff.

This preliminary study examined the effects of tobacco-free snuff (intervention, n = 52) compared with no snuff (control, n = 54) for reducing tobacco use among smokeless tobacco (ST) users not interested in quitting. Both groups received behavioral instructions, and intervention subjects received tobacco-free snuff for 8 weeks. Participants were required to reduce their intake by 50% during the first 4 weeks and by 75% during the subsequent 4 weeks. Follow-up occurred at 12 weeks. Significant reductions were observed from baseline to week 8 (end of treatment) for both treatment groups in the amount of ST use (tins/week and dips/day, p<.001); mean urinary cotinine (p<.001); and mean urinary total NNAL, a carcinogen biomarker (p<.001). At week 8 the intervention resulted in a lower mean total NNAL (p = .048). Compared with the control condition, the intervention resulted in a higher percentage of subjects achieving at least a 50% reduction in cotinine (p = .046) and total NNAL (p = .002) at the end of treatment, more quit attempts (p = .030), and a longer mean duration of abstinence (p = .013) through follow-up. An ST reduction intervention incorporating tobacco-free snuff could potentially reduce risk for ST-related disease beyond that achieved with no snuff by increasing the number of patients who achieve significant reductions in carcinogen exposure and, more important, by facilitating tobacco abstinence by increasing quit attempts and abstinence duration.