Inter-rater agreement on chromosome 5 breakage in FISH-based mutagen sensitivity assays (MSAs)

In chromosome breakage assays, validated, universal criteria for selection of cells and classification of chromosome aberrations may enhance their utility for cancer susceptibility screening. To standardize a fluorescence in situ hybridization (FISH) modification of the mutagen sensitivity assay (MSA), scoring criteria were evaluated by web-based validation. Two hundred digital FISH images were assigned random identification numbers. With this set of images, criteria for inclusion of cells and measurement of the frequency of abnormal cells were evaluated by eight observers, all of whom had five or more years of experience. Observers included doctoral and MS/BS level cytogeneticists, and were drawn from a randomized pool of 54 volunteers. Questions addressed were: (1) how uniformly were criteria applied to analysis of a standard digital FISH image set and (2) did concordance vary with educational level? These data suggest inter-rater agreement within a factor of 2 for average breakage frequency, but revealed greater variability in cell selection. These results aid in estimating the components of assay variance due to definitions, technical parameters and biological variables.     

2,5-Diketopiperazines as potent and selective oxytocin antagonists 1: Identification, stereochemistry and initial SAR

This paper covers efforts to discover orally active potent and selective oxytocin antagonists. Screening pooled libraries identified a novel series of 2,5-diketopiperazine derivatives with antagonist activity at the human oxytocin receptor. We report the initial structure-activity relationship investigations and the determination of the stereochemistry of the most potent compounds.     

Ambient Air Pollution and the Progression of Atherosclerosis in Adults

Background

Cross-sectional studies suggest an association between exposure to ambient air pollution and atherosclerosis. We investigated the association between outdoor air quality and progression of subclinical atherosclerosis (common carotid artery intima-media thickness, CIMT).

Methodology/Principal Findings

We examined data from five double-blind randomized trials that assessed effects of various treatments on the change in CIMT. The trials were conducted in the Los Angeles area. Spatial models and land-use data were used to estimate the home outdoor mean concentration of particulate matter up to 2.5 micrometer in diameter (PM2.5), and to classify residence by proximity to traffic-related pollution (within 100 m of highways). PM2.5 and traffic proximity were positively associated with CIMT progression. Adjusted coefficients were larger than crude associations, not sensitive to modelling specifications, and statistically significant for highway proximity while of borderline significance for PM2.5 (P = 0.08). Annual CIMT progression among those living within 100 m of a highway was accelerated (5.5 micrometers/yr [95%CI: 0.13–10.79; p = 0.04]) or more than twice the population mean progression. For PM2.5, coefficients were positive as well, reaching statistical significance in the socially disadvantaged; in subjects reporting lipid lowering treatment at baseline; among participants receiving on-trial treatments; and among the pool of four out of the five trials.

Conclusion

Consistent with cross-sectional findings and animal studies, this is the first study to report an association between exposure to air pollution and the progression of atherosclerosis – indicated with CIMT change – in humans. Ostensibly, our results suggest that air pollution may contribute to the acceleration of cardiovascular disease development – the main causes of morbidity and mortality in many countries. However, the heterogeneity of the volunteering populations across the five trials, the limited sample size within trials and other relevant subgroups, and the fact that some key findings reached statistical significance in subgroups rather than the sample precludes generalizations to the general population.     

Explanation of the bilateral deficit in human vertical squat jumping.

In the literature, it has been reported that the mechanical output per leg is less in two-leg jumps than in one-leg jumps. This so-called bilateral deficit has been attributed to a reduced neural drive to muscles in two-leg jumps. The purpose of the present study was to investigate the possible contribution of nonneural factors to the bilateral deficit in jumping. We collected kinematics, ground reaction forces, and electromyograms of eight human subjects performing two-leg and one-leg (right leg) squat jumps and calculated mechanical output per leg. We also used a model of the human musculoskeletal system to simulate two-leg and one-leg jumps, starting from the initial position observed in the subjects. The model had muscle stimulation as input, which was optimized using jump height as performance criterion. The model did not incorporate a reduced maximal neural drive in the two-leg jump. Both in the subjects and in the model, the work of the right leg was more than 20% less in the two-leg jump than in the one-leg jump. Peak electromyogram levels in the two-leg jump were reduced on average by 5%, but the reduction was only statistically significant in m. rectus femoris. In the model, approximately 75% of the bilateral deficit in work per leg was explained by higher shortening velocities in the two-leg jump, and the remainder was explained by lower active state of muscles. It was concluded that the bilateral deficit in jumping is primarily caused by the force-velocity relationship rather than by a reduction of neural drive.     

Synthesis and activity of small molecule GPR40 agonists

The first report on the identification and structure-activity relationships of a novel series of GPR40 agonists based on a 3-(4-{[N-alkyl]amino}phenyl)propanoic acid template is described. Structural modifications to the original screening hit yielded compounds with a 100-fold increase in potency at the human GPR40 receptor and pEC(50)s in the low nanomolar range. The carboxylic acid moiety is not critical for activity but typically elicits an agonistic response higher than those observed with carboxamide replacements. These compounds may prove useful in unraveling the therapeutic potential of this receptor for the treatment of Type 2 diabetes.     

Genetic diversity of Trypanosoma cruzi parasites infecting dogs in southern Louisiana sheds light on parasite transmission cycles and serological diagnostic performance

BackgroundChagas disease is a neglected zoonosis of growing concern in the southern US, caused by the parasite Trypanosoma cruzi. We genotyped parasites in a large cohort of PCR positive dogs to shed light on parasite transmission cycles and assess potential relationships between parasite diversity and serological test performance.Methodology/principal findingsWe used a metabarcoding approach based on deep sequencing of T. cruzi mini-exon marker to assess parasite diversity. Phylogenetic analysis of 178 sequences from 40 dogs confirmed the presence of T. cruzi discrete typing unit (DTU) TcI and TcIV, as well as TcII, TcV and TcVI for the first time in US dogs. Infections with multiple DTUs occurred in 38% of the dogs. These data indicate a greater genetic diversity of T. cruzi than previously detected in the US. Comparison of T. cruzi sequence diversity indicated that highly similar T. cruzi strains from these DTUs circulate in hosts and vectors in Louisiana, indicating that they are involved in a shared T. cruzi parasite transmission cycle. However, TcIV and TcV were sampled more frequently in vectors, while TcII and TcVI were sampled more frequently in dogs.Conclusions/significanceThese observations point to ecological host-fitting being a dominant mechanism involved in the diversification of T. cruzi-host associations. Dogs with negative, discordant or confirmed positive T. cruzi serology harbored TcI parasites with different mini-exon sequences, which strongly supports the hypothesis that parasite genetic diversity is a key factor affecting serological test performance. Thus, the identification of conserved parasite antigens should be a high priority for the improvement of current serological tests.