Regulation of Oxidative Stress Response by CosR, an Essential Response Regulator in Campylobacter jejuni

CosR (Campylobacter oxidative stress regulator; Cj0355c) is an OmpR-type response regulator essential for the viability of Campylobacter jejuni, a leading foodborne pathogen causing human gastroenteritis worldwide. Despite importance, the function of CosR remains completely unknown mainly because of cell death caused by its knockout mutation. To overcome this technical limitation, in this study, antisense technology was used to investigate the regulatory function of CosR by modulating the level of CosR expression. Two-dimensional gel electrophoresis (2DGE) was performed to identify the CosR regulon either by suppressing CosR expression with antisense peptide nucleic acid (PNA) or by overexpressing CosR in C. jejuni. According to the results of 2DGE, CosR regulated 32 proteins involved in various cellular processes. Notably, CosR negatively regulated a few key proteins of the oxidative stress response of C. jejuni, such as SodB, Dps, Rrc and LuxS, whereas CosR positively controlled AhpC. Electrophoretic mobility shift assay showed that CosR directly bound to the promoter region of the oxidative stress genes. DNase I footprinting assays identified 21-bp CosR binding sequences in the sodB and ahpC promoters, suggesting CosR specifically recognizes and binds to the regulated genes. Interestingly, the level of CosR protein was significantly reduced by paraquat (a superoxide generator) but not by hydrogen peroxide. Consistent with the overall negative regulation of oxidative stress defense proteins by CosR, the CosR knockdown by antisense rendered C. jejuni more resistant to oxidative stress compared to the wild type. Overall, this study reveals the important role played by the essential response regulator CosR in the oxidative stress defense of C. jejuni

DMTs and Covid-19 severity in MS: a pooled analysis from Italy and France

We evaluated the effect of DMTs on Covid-19 severity in patients with MS, with a pooled-analysis of two large cohorts from Italy and France. The association of baseline characteristics and DMTs with Covid-19 severity was assessed by multivariate ordinal-logistic models and pooled by a fixed-effect meta-analysis. 1066 patients with MS from Italy and 721 from France were included. In the multivariate model, anti-CD20 therapies were significantly associated (OR = 2.05, 95%CI = 1.39–3.02, p < 0.001) with Covid-19 severity, whereas interferon indicated a decreased risk (OR = 0.42, 95%CI = 0.18–0.99, p = 0.047). This pooled-analysis confirms an increased risk of severe Covid-19 in patients on anti-CD20 therapies and supports the protective role of interferon

Improving mechanical properties of magnesium alloy by incremental equal angular pressing (ECAP)

This presentation looks at improving mechanical properties of magnesium alloy by incremental equal angular pressing (ECAP

Microstructure evolution in AZ31B magnesium alloy subjected to tension

Incremental Equal Channel Angular Pressing (I-ECAP) is an incremental severe plastic deformation (SPD) process, which can be used to process continuous bars, plates and sheets. In the current study, commercially available AZ31B magnesium alloy bars were subjected to four passes of I-ECAP using route BC; the process was conducted at 250 °C since fracture was reported at lower temperatures. The obtained fine-grained bars were subjected to side upsetting at 200 °C to produce sheets. The significant height reduction, from 10 mm to 2 mm, was obtained without fracture. Then, flat tensile samples were machined from as-received coarse-grained bars and fine-grained, strongly textured sheets. The samples were polished and etched to enable observation of microstructure evolution during testing. Tensile testing was conducted in the SEM chamber at room temperature with constant tool velocity. It was shown that earlier fracture of coarse-grained samples, comparing to fine-grained ones, can be attributed to twinning as twin-size voids were observed in the fracture zone. Avoidance of twinning was identified as the most important factor for ductility enhancement of fine-grained and strongly textured sheets

Mechanical properties of AZ31B magnesium alloy processed by I-ECAP

Incremental equal channel angular pressing (I-ECAP) is a severe plastic deformation process used to refine grain size of metals, which allows processing very long billets. In this work, AZ31B magnesium alloy was processed by routes A, BC and C of I-ECAP. Texture and grain size effects on mechanical properties and tension-compression anisotropy were investigated. Strong influence of processing route on yield and fracture behaviour of material was established. SEM technique was used to obtain microstructure images of I-ECAPed samples subjected to tension and compression. Different deformation mechanisms were activated during tension in samples with coarse and fine grained microstructures. In coarse grained samples large amount of twins was reported while fined grained microstructure exhibited slip dominated deformation. Influence of different deformation mechanisms on mechanical properties was discussed. It was concluded that material properties of AZ31B can be tailored for various applications by using different routes of I-ECAP

Analyse de déformations et contraintes locales par couplage EBSD et microdiffraction Kossel

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