A field study of the microbiological quality of fresh produce of domestic and Mexican origin

Produce is responsible for an increasingly larger proportion of foodborne disease outbreaks. In particular, the globalization of the food supply may introduce new food safety risks and allow widespread distribution of contaminated food, particularly produce. The objectives of this study were to: (i) compare the overall quality of domestic and Mexican produce throughout the packing process; (ii) examine changes in microbiological quality of both domestic and Mexican produce at each stage of production and processing; and (iii) evaluate the prevalence of select pathogens on fresh produce, including leafy green, herbs, melons, and vegetables. Furthermore, we also sought to characterize the antibiotic resistance profiles of Enterococcus faecium and Enterococcus faecalis strains isolated from fresh produce. A total of 466 produce and matching environmental swab samples was collected from various locations in packing sheds in the southern US from November 2002 through December 2003. These samples were assayed by enumerative tests for total aerobic bacteria (APC), total coliforms, total Enterococcus, and E. coli. Produce samples were also analyzed for the presence of Salmonella, Listeria monocytogenes, Shigella, and E. coli O157:H7. A total of 112 E. faecium and E. faecalis isolates were further screened for antibiotic resistance using a panel of seventeen antibiotics. Overall, the microbiological quality of fresh produce ranged from 4.0 to 7.9 log(10) CFU/g (APC); less than 1.0 log(10) to 4.5 log(10) CFU/g (coliforms); less than 1.0 log(10) to 4.0 log(10) CFU/g (E. coli); and less than 1.0 log(10) to 5.4 log(10) CFU/g (Enterococcus). No Salmonella, Shigella, or E. coli O157:H7 were detected from the 466 25-g produce samples tested. However, three domestic cabbage samples were found to be positive for L. monocytogenes. Of the Enterococcus isolates, E. faecium had a higher degree of resistance to antibiotics in general, while Enterococcus spp. isolated from Mexican produce had a higher degree of antibiotic resistance when compared to strains isolated from produce samples of domestic origin. Despite increased attention to the role of imported produce in foodborne disease, this study does not support the assumption that domestic produce is of higher microbial quality than Mexican produce.     

NMR relaxometry and differential scanning calorimetry during meat cooking

By combining simultaneous nuclear magnetic resonance (NMR) T₂ relaxometry and differential scanning calorimetry (DSC) on pork samples heated to nine temperature levels between 25 and 75 °C, the present study investigates the relationship between thermal denaturation of meat proteins and heat-induced changes in water characteristics. Principal component analysis (PCA) on the distributed ¹H NMR T₂ relaxation data revealed that the major changes in water characteristics during heating occur between 40 and 50 °C. This is probably initiated by denaturation of myosin heads, which however, could not be detected in the DSC thermograms obtained directly on the meat. In contrast, the DSC thermograms revealed endothermic transitions at 54, 65 and 77 °C, probably reflecting the denaturation of myosin (rods and light chain), sarcoplasmic proteins together with collagen and actin, respectively. Simultaneous modelling of DSC and NMR data by partial least squares regression (PLSR) revealed a correlation between denaturation of myosin rods and light chains at 53–58 °C and heat-induced changes in myofibrillar water (T₂ relaxation time 10–60 ms) as well as between actin denaturation at 80–82 °C and expulsion of water from the meat. Accordingly, the present study demonstrates a direct relationship between thermal denaturation of specific proteins/protein structures and heat-induced changes in water mobility during heating of pork.     

MS-binding assays: kinetic, saturation, and competitive experiments based on quantitation of bound marker as exemplified by the GABA transporter mGAT1

A new kind of binding assay is described in which the amount of a nonlabeled marker bound to the target is quantified by LC-ESI-MS-MS. This new approach was successfully implemented with nonlabeled NO 711 as marker and the GABA transporter subtype mGAT1 as target. The native marker bound to the target was liberated from the receptor protein by methanol denaturation after filtration. A reliable and sensitive LC-ESI-MS-MS method for the quantitation of NO 711 was developed, and data from mass spectrometric detection were analyzed by nonlinear regression. Kinetic MS-binding experiments yielded values for k+1 and k-1, while in saturation MS-binding experiments, Kd and Bmax values were determined. In competitive MS-binding experiments, Ki values were obtained for various test compounds covering a broad range of affinities for mGAT1. All experiments were performed in 96-well plate format with a filter plate for the separation step which improved the efficiency and throughput of the procedure. The method was validated by classical radioligand-binding experiments with the labeled marker [3H2]NO 711 in parallel. The results obtained from MS-binding experiments were found to be in good agreement with the results of the radioligand-binding assays. The new kind of MS-binding assay presented herein is further adapted to the conventional radioligand-binding assay in that the amount of bound marker is securely quantified. This promises easy implementation in accordance with conventional binding assays without the major drawbacks that are inherent in radioligand or fluorescence binding assays. Therefore, MS-binding assays are a true alternative to classical radioligand-binding assays.     

Interaction between the pore and a fast gate of the cardiac sodium channel

Permeant ions affect a fast gating process observed in human cardiac sodium channels (Townsend, C., H.A. Hartmann, and R. Horn. 1997. J. Gen. Physiol. 110:11-21). Removal of extracellular permeant ions causes a reduction of open probability at positive membrane potentials. These results suggest an intimate relationship between the ion-conducting pore and the gates of the channel. We tested this hypothesis by three sets of manipulations designed to affect the binding of cations within the pore: application of intracellular pore blockers, mutagenesis of residues known to contribute to permeation, and chemical modification of a native cysteine residue (C373) near the extracellular mouth of the pore. The coupling between extracellular permeant ions and this fast gating process is abolished both by pore blockers and by a mutation that severely affects selectivity. A more superficial pore mutation or chemical modification of C373 reduces single channel conductance while preserving both selectivity of the pore and the modulatory effects of extracellular cations. Our results demonstrate a modulatory gating role for a region deep within the pore and suggest that the structure of the permeation pathway is largely preserved when a channel is closed.     

Chemical synthesis and characterization of POSS-functionalized poly[3-hydroxyalkanoates]

A polyhedral oligomeric silsesquioxane containing seven isobutyl groups and one mercaptopropyl group (POSS-SH) was linked via a free radical addition reaction to the side-chain double bonds of bacterial poly[3-hydroxyalkanoate-co-3-hydroxyalkenoate], (PHAE). PHAE with 11.5, 55, 78, and 97 mol% of double bonds were used to produce a series of inorganic-organic hybrid materials, PHAE-POSS, with increasing amounts of POSS. The reactions proceeded with high yields and limited side reactions, confirmed with NMR and GPC experiments. X-ray diffraction and ¹³C solid-state NMR analysis of these nanocomposite materials suggested the favoured crystallization of POSS, with PHAE functioning as a non-crystalline combining matrix. This is in contrast to blends of POSS-SH and PHAE, where incompatibility occurred and the two components crystallized independently. The covalent links between PHAE and POSS imposed spatial constraint which resulted in disordered crystalline POSS domains and limited crystal sizes. With increasing POSS content, the appearance of these POSS-based biopolyesters changed from non-sticky and elastic to brittle and glass-like. The covalent linking of POSS-SH to PHAE increased the heat stability such as glass transitions, and melting points could be tailored between 48 and 120 °C.     

The validity of self-reported cocaine use in two groups of cocaine abusers.

To evaluate the validity of 2 self-report methods for estimating cocaine use, Timeline Follow-Back (TLFB) and weekly calendar reports from 65 patients with a cocaine use disorder were compared with urine drug test results. The TLFB showed fair to moderate validity, and the weekly calendar showed moderate to high validity in measuring the frequency of cocaine use. Similar results were obtained when the self-report measures were used to time specific cocaine use episodes. In addition to evidence for superiority of the weekly calendar, the validity of self-reports was inversely related to the percentage of positive urine test results. Furthermore, there was some evidence that validity increased as the time window over which the comparisons were drawn increased. Given the central role of self-reports in the clinical and research evaluation of drug use, factors affecting their validity warrant further investigation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A randomized trial of cognitive therapy and imaginal exposure in the treatment of chronic posttraumatic stress disorder.

A randomized trial was performed in which imaginal exposure (IE) and cognitive therapy (CT) were compared in the treatment of chronic posttraumatic stress disorder (PTSD). Patients who continued to meet PTSD caseness at the end of a 4-week symptom-monitoring baseline period (n?=?72) were randomly allocated to either IE or CT. There was a significant improvement in all measures over treatment and at follow-up, although there were no significant differences between the 2 treatments at any assessment. A significantly greater number of patients who showed worsening over treatment received IE, although this effect was not found at follow-up. Patients who worsened showed a greater tendency to miss treatment sessions, rated therapy as less credible, and were rated as less motivated by the therapist. It was concluded that either exposure or a challenge to cognition can result in symptom reduction, although neither resulted in complete improvement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

NaCl-induced changes in structure and water mobility in potato tissue as determined by CLSM and LF-NMR

This study for the first time reports the combined use of low-field nuclear magnetic resonance (LF-NMR) and confocal laser scanning microscopy (CLSM) in the study of the effects of salting on low and high dry matter (DM) potato tissue. The simultaneous use of CLSM and NMR resulted in important information in relation to the interpretation of the origin of the NMR water populations. Salting caused the raw potato cells to loose weight, which in the microscopic images was observed as loss of turgor pressure still further away from the edges of the samples with increased salting time. The total water loss after salting was lowest for high DM potatoes. The LF-NMR analyses revealed that this could be ascribed to a faster T₂ relaxation time of the cytoplasmatic and extracellular water and thus to water being more restricted in high DM potatoes. In addition, a tendency to a faster T₂ relaxation time was observed for both low and high DM potatoes with increasing salting time, which reveals a salt-induced restriction of the cytoplasmatic and extracellular water population. The paper illustrates the aptitude of NMR and CLSM to determine and elucidate structural changes and associated changes in water mobility in potato tissue.     

Enhanced Memory for Negatively Emotionally Charged Pictures Without Selective Rumination.

Emotionally charged materials have been found to elicit higher levels of recall in many studies. However, the use of slow presentations and/or uncontrolled retention intervals may have allowed subjects to rehearse emotional materials preferentially. The authors presented a series of 5 pictures (1 emotionally charged) at a rate of 4 pictures per second, precluding selective rehearsal. In Experiment 1, subjects recalled the pictures immediately or after performing an arithmetic task for 20 s. In Experiment 2, the pictures were described as to-be-ignored distractors, and the memory test was unexpected. Stimulus emotionality greatly enhanced recall in all conditions. The speed of the presentations and the fact that enhancement did not spread to temporally adjacent items argues against some widely discussed mechanisms for emotional enhancement. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rutschblock-scale snowpack stability derived from multiple quality-controlled SnowMicroPen measurements

Stability prediction from SnowMicroPen (SMP) profiles would support avalanche forecasting operations, since objective stability information could be gathered more quickly than with standard tests, thereby allowing sampling at higher resolution and over larger spatial scales. Previous studies have related the snow properties derived from the SMP to observed snow properties at Rutschblock (RB) and compression test failure planes. The goals of this study are to show to what extent snowpack stability for artificial triggering, based on RB, can be derived from SMP measurements and how multiple measurements at the RB scale improve the results. Measurements at 36 different sites were used for the development of a classification scheme. Each site included a RB test, a manual profile, and 6 to 10 adjacent SMP measurements, for a total of 262 SMP profiles. A recently improved SMP theory was applied to estimate the micro-structural and mechanical properties of manually defined weak layers and slab layers. SMP signal quality control and different noise treatment methods were taken into consideration in the analysis. The best and most robust predictor of RB stability was the weak layer micro-scale strength. In combination with the SMP-estimated mean density of the slab layer, the total accuracy of predicting RB stability classes was 85% over the entire dataset, and 88% when signals with obvious signal dampening (11% of the dataset) were removed. The total accuracy increased when multiple SMP measurements at the RB scale were used to calculate the mean weak layer strength, when compared to using just one SMP measurement at a site. The analysis was robust to trends and offsets in the absolute SMP force, which was a frequent signal error. However, it was sensitive to dampened or disturbed SMP force micro variance. The sensitivity analysis also showed that the best predictor of instability, the weak layer micro-scale strength, was robust to the choice of SMP signal noise removal method.