Synthetase polyspecificity as a tool to modulate protein function

The site-specific incorporation of unnatural amino acids (UAAs) into proteins in bacteria is made possible by the evolution of aminoacyl-tRNA synthetases that selectively recognize and aminoacylate the amino acid of interest. Recently we have discovered that some of the previously evolved aaRSs display a degree of polyspecificity and are capable of recognizing multiple UAAs. Herein we report the polyspecificity of an aaRS evolved to encode a comarin containing amino acid. This polyspecificity was then exploited to introduce several UAAs into the fluorophore of GFP, altering its photophysical properties.     

Virulence Gene Profiling and Pathogenicity Characterization of Non-Typhoidal Salmonella Accounted for Invasive Disease in Humans

Human infection with non-typhoidal Salmonella serovars (NTS) infrequently causes invasive systemic disease and bacteremia. To understand better the nature of invasive NTS (iNTS), we studied the gene content and the pathogenicity of bacteremic strains from twelve serovars (Typhimurium, Enteritidis, Choleraesuis, Dublin, Virchow, Newport, Bredeney, Heidelberg, Montevideo, Schwarzengrund, 9,12:l,v:- and Hadar). Comparative genomic hybridization using a Salmonella enterica microarray revealed a core of 3233 genes present in all of the iNTS strains, which include the Salmonella pathogenicity islands 1–5, 9, 13, 14; five fimbrial operons (bcf, csg, stb, sth, sti); three colonization factors (misL, bapA, sinH); and the invasion gene, pagN. In the iNTS variable genome, we identified 16 novel genomic islets; various NTS virulence factors; and six typhoid-associated virulence genes (tcfA, cdtB, hlyE, taiA, STY1413, STY1360), displaying a wider distribution among NTS than was previously known. Characterization of the bacteremic strains in C3H/HeN mice showed clear differences in disease manifestation. Previously unreported characterization of serovars Schwarzengrund, 9,12:l,v:-, Bredeney and Virchow in the mouse model showed low ability to elicit systemic disease, but a profound and elongated shedding of serovars Schwarzengrund and 9,12:l,v:- (as well as Enteritidis and Heidelberg) due to chronic infection of the mouse. Phenotypic comparison in macrophages and epithelial cell lines demonstrated a remarkable intra-serovar variation, but also showed that S. Typhimurium bacteremic strains tend to present lower intracellular growth than gastroenteritis isolates. Collectively, our data demonstrated a common core of virulence genes, which might be required for invasive salmonellosis, but also an impressive degree of genetic and phenotypic heterogeneity, highlighting that bacteremia is a complex phenotype, which cannot be attributed merely to an enhanced invasion or intracellular growth of a particular strain.     

Kinetics of cross-slope running

The purpose of the present study was to identify kinetic responses to running on mediolaterally elevated (cross-sloped) running surfaces. Ground reaction forces (GRFs), GRF lever arms and joint moment characteristics of 19 male runners were analyzed when running at 3.5 m/s on a custom-made, tiltable runway. Tilt angles of 3° and 6° for medial and lateral elevation were analyzed using a 10 camera Vicon Nexus system and a force platform. The point of force application of the GRF showed a systematic shift in the order of 1–1.5 cm to either the lateral or medial aspect of the foot for lateral or medial inclinations, respectively. Consequently, the strongest significant effects of tilt orientation and level on joint kinetics and ground reaction force lever arms were identified at the ankle, knee and hip joint in the frontal plane of movement. External eversion moments at the ankle were significantly increased by 35% for 6° of lateral elevation and decreased by 16% for 6° of medial elevation. Altering the cross-slope of the running surface changed the pattern of ankle joint moments in the transversal plane. Effect sizes were on average larger for laterally elevated conditions, indicating a higher sensitivity of kinetic parameters to this kind of surface tilt. These alterations in joint kinetics should be considered in the choice of the running environment, especially for specific risk groups, like runners in rehabilitation processes.     

Long-Term Prognostic Value of Restitution Slope in Patients with Ischemic and Dilated Cardiomyopathies

Background

An action potential duration (APD) restitution curve with a steep slope ≥1 has been associated with increased susceptibility for malignant ventricular arrhythmias. We aimed to evaluate the “restitution hypothesis” and tested ventricular APD restitution slope as well as effective refractory period (ERP)/APD ratio for long-term prognostic value in patients with ischemic (ICM) or dilated cardiomyopathy (DCM).

Methodology/Principal Findings

Monophasic action potentials were recorded in patients with ICM (n = 32) and DCM (n = 42) undergoing routine programmed ventricular stimulation (PVS). Left ventricular ejection fraction was 32±7% and 28±9%, respectively. APD and ERP were measured at baseline stimulation (S₁) and upon introduction of one to three extrastimuli (S₂–S₄). ERP/APD ratios and the APD restitution curve were calculated and the maximum restitution slope was determined. After a mean follow-up of 6.1±3.0 years, the combined end-point of mortality and and/or implantable cardioverter-defibrillator shock was not predicted by restitution slope or ERP/APD ratios. Comparing S₂ vs. S₃ vs. S₄ extrastimuli for restitution slope (1.5±0.6 vs. 1.4±0.4 vs. 1.3±0.5; p = NS), additional extrastimuli did not lead to a steepening restitution slope. ERP/APD ratio decreased with additional extrastimuli (0.98±0.09 [S₁] vs. 0.97±0.10 [S₂] vs. 0.93±0.11 [S₃]; p = 0.03 S₁ vs. S₃). Positive PVS was strongly predictive of outcome (p = 0.006).

Conclusions/Significance

Neither ventricular APD restitution slope nor ERP/APD ratios predict outcome in patients with ICM or DCM.     

Affective Computing and the Impact of Gender and Age

Affective computing aims at the detection of users’ mental states, in particular, emotions and dispositions during human-computer interactions. Detection can be achieved by measuring multimodal signals, namely, speech, facial expressions and/or psychobiology. Over the past years, one major approach was to identify the best features for each signal using different classification methods. Although this is of high priority, other subject-specific variables should not be neglected. In our study, we analyzed the effect of gender, age, personality and gender roles on the extracted psychobiological features (derived from skin conductance level, facial electromyography and heart rate variability) as well as the influence on the classification results. In an experimental human-computer interaction, five different affective states with picture material from the International Affective Picture System and ULM pictures were induced. A total of 127 subjects participated in the study. Among all potentially influencing variables (gender has been reported to be influential), age was the only variable that correlated significantly with psychobiological responses. In summary, the conducted classification processes resulted in 20% classification accuracy differences according to age and gender, especially when comparing the neutral condition with four other affective states. We suggest taking age and gender specifically into account for future studies in affective computing, as these may lead to an improvement of emotion recognition accuracy.     

Caries-Preventive Effect of High-Viscosity Glass Ionomer and Resin-Based Fissure Sealants on Permanent Teeth: A Systematic Review of Clinical Trials

Background

Glass-ionomers are traditionally regarded to be inferior to resin as fissure sealants in protecting teeth from dental caries, due to their comparatively lower retention rate. Unlike low-viscosity glass-ionomers, high-viscosity glass-ionomer cements (HVGIC) are placed as sealants by pressing the material into pits and fissures with a petroleum-jelly-coated index finger. Hence, HVGIC sealants are assumed to penetrate pits and fissures deeper, resulting in a higher material retention rate, which may increase its caries-preventive effect.

Methods

The aim of this review was to answer the question as to whether, in patients with fully erupted permanent molar teeth, HVGIC based fissure sealants are less effective to protect against dental carious lesions in occlusal pits and fissures than resin-based fissure sealants? A systematic literature search in eight databases was conducted. Heterogeneity of accepted trials and imprecision of the established evidence were assessed. Extracted sufficiently homogenous datasets were pooled by use of a random-effects meta-analysis. Internal trial validity was evaluated. The protocol of this systematic review was registered with the International Prospective Register of Systematic Reviews (PROSPERO / Nr.: CRD42015016007).

Results

Seven clinical trials were provisionally included for further review. Of these, one was excluded. Seven trial reports reporting on six trials were accepted. From these, 11 datasets were extracted and pooled in four meta-analyses. The results suggest no statistically significant differences after up to 48 months and borderline significant differences in favour of HVGIC sealants after 60 months (RR 0.29; 95% CI: 0.09–0.95; p = 0.04 / RD -0.07; 95% CI: -0.14, -0.01). The point estimates and upper confidence levels after 24, 36, 48 and 60 months of RR 1.36; RR 0.90; RR 0.62; RR 0.29 and 2.78; 1.67; 1.21; 0.95, respectively, further suggest a chronological trend in favour of HVGIC above resin-based sealants. The internal trial validity was judged to be low and the bias risk high for all trials. Imprecision of results was considered too high for clinical guidance.

Conclusion

It can be concluded that: (i) Inferiority claims against HVGIC in comparison to resin-based sealants as current gold-standard are not supported by the clinical evidence; (ii) The clinical evidence suggests similar caries-preventive efficacy of HVGIC and resin-based sealants after a period of 48 months in permanent molar teeth but remains challenged by high bias risk; (iii) Evidence concerning a possible superiority of HVGIC above resin-based sealants after 60 months is poor (even if the high bias risk is disregarded) due to imprecision and requires corroboration through future research.