Superoxide reductase as a unique defense system against superoxide stress in the microaerophile Treponema pallidum.

International audienceAerobic life requires the presence of antioxidant enzymes, such as superoxide dismutase, catalase, and peroxidase to eliminate deleterious oxygen derivatives. Treponema pallidum, a microaerophilic bacterium responsible for venereal syphilis, is an interesting organism because it lacks all of the above-mentioned enzymes, as deduced from its recently sequenced genome. In this paper, we describe a gene in T. pallidum with sequence homologies to a new class of antioxidant systems, named superoxide reductases, recently isolated from sulfate-reducing bacteria (Lombard, M., Fontecave, M., Touati, D., and Nivière, V. (2000) J. Biol. Chem. 275, 115-121). We report that (i) expression of the T. pallidum gene fully restored to a superoxide dismutase-deficient Escherichia coli mutant the ability to grow under aerobic conditions; (ii) the corresponding protein displays a strong superoxide reductase activity; and (iii) the T. pallidum protein contains only one mononuclear nonheme ferrous center, able to reduce superoxide selectively and efficiently, whereas previously characterized superoxide reductase from Desulfoarculus baarsii contains an additional rubredoxin-like ferric center. These results suggest that T. pallidum antioxidant defenses rely on a new class of superoxide reductase and raise the question of the importance of superoxide reductases in mechanisms for detoxifying superoxide radicals

Reaction of the desulfoferrodoxin from Desulfoarculus baarsii with superoxide anion. Evidence for a superoxide reductase activity.

International audienceDesulfoferrodoxin is a small protein found in sulfate-reducing bacteria that contains two independent mononuclear iron centers, one ferric and one ferrous. Expression of desulfoferrodoxin from Desulfoarculus baarsii has been reported to functionally complement a superoxide dismutase deficient Escherichia coli strain. To elucidate by which mechanism desulfoferrodoxin could substitute for superoxide dismutase in E. coli, we have purified the recombinant protein and studied its reactivity toward O-(2). Desulfoferrodoxin exhibited only a weak superoxide dismutase activity (20 units mg(-1)) that could hardly account for its antioxidant properties. UV-visible and electron paramagnetic resonance spectroscopy studies revealed that the ferrous center of desulfoferrodoxin could specifically and efficiently reduce O-(2), with a rate constant of 6-7 x 10(8) M(-1) s(-1). In addition, we showed that membrane and cytoplasmic E. coli protein extracts, using NADH and NADPH as electron donors, could reduce the O-(2) oxidized form of desulfoferrodoxin. Taken together, these results strongly suggest that desulfoferrodoxin behaves as a superoxide reductase enzyme and thus provide new insights into the biological mechanisms designed for protection from oxidative stresses

Panton-Valentine leukocidin positive sequence type 80 methicillin-resistant Staphylococcus aureus carrying a staphylococcal cassette chromosome mec type IVc is dominant in neonates and children in an Algiers hospital

Methicillin-resistant Staphylococcus aureus (MRSA) is a major antimicrobial drug-resistant pathogen causing serious infections. It was first detected in healthcare settings, but in recent years it has also become disseminated in the community. Children and young adults are most susceptible to infection by community-acquired (CA) MRSA strains. In this study 25 MRSA isolates implicated in infections of neonates and children admitted to an Algiers hospital during an 18 month period were characterized by molecular methods including staphylococcal cassette chromosome (SCC) mec typing, PCR amplification of pvl genes, pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Fifteen out of 25 isolates were from hospital-acquired infections. Twenty-four isolates carried SCCmec type IVc and belonged to the sequence type (ST) 80, one isolate carried SCCmec type II and was ST 39. Twenty-two out of 24 ST80-MRSA-IVc isolates carried pvl genes. Our results suggest that the Panton-Valentine leukocidin positive ST80- MRSA-IVc is the dominant MRSA clone causing disease in neonates and children in Algiers

Superoxide reductase from Desulfoarculus baarsii: reaction mechanism and role of glutamate 47 and lysine 48 in catalysis.

International audienceSuperoxide reductase (SOR) is a small metalloenzyme that catalyzes reduction of O(2)(*)(-) to H(2)O(2) and thus provides an antioxidant mechanism against superoxide radicals. Its active site contains an unusual mononuclear ferrous center, which is very efficient during electron transfer to O(2)(*)(-) [Lombard, M., Fontecave, M., Touati, D., and Nivière, V. (2000) J. Biol. Chem. 275, 115-121]. The reaction of the enzyme from Desulfoarculus baarsii with superoxide was studied by pulse radiolysis methods. The first step is an extremely fast bimolecular reaction of superoxide reductase with superoxide, with a rate constant of (1.1 +/- 0.3) x 10(9) M(-1) s(-1). A first intermediate is formed which is converted to a second one at a much slower rate constant of 500 +/- 50 s(-1). Decay of the second intermediate occurs with a rate constant of 25 +/- 5 s(-1). These intermediates are suggested to be iron-superoxide and iron-peroxide species. Furthermore, the role of glutamate 47 and lysine 48, which are the closest charged residues to the vacant sixth iron coordination site, has been investigated by site-directed mutagenesis. Mutation of glutamate 47 into alanine has no effect on the rates of the reaction. On the contrary, mutation of lysine 48 into an isoleucine led to a 20-30-fold decrease of the rate constant of the bimolecular reaction, suggesting that lysine 48 plays an important role during guiding and binding of superoxide to the iron center II. In addition, we report that expression of the lysine 48 sor mutant gene hardly restored to a superoxide dismutase-deficient Escherichia coli mutant the ability to grow under aerobic conditions

A real-time early warning seismic event detection algorithm using smart geo-spatial bi-axial inclinometer nodes for Industry 4.0 applications

Earthquakes are one of the major natural calamities as well as a prime subject of interest for seismologists, state agencies, and ground motion instrumentation scientists. The real-time data analysis of multi-sensor instrumentation is a valuable knowledge repository for real-time early warning and trustworthy seismic events detection. In this work, an early warning in the first 1 micro-second and seismic wave detection in the first 1.7 milliseconds after event initialization is proposed using a seismic wave event detection algorithm (SWEDA). The SWEDA with nine low-computation-cost operations is being proposed for smart geospatial bi-axial inclinometer nodes (SGBINs) also utilized in structural health monitoring systems. SWEDA detects four types of seismic waves, i.e., primary (P) or compression, secondary (S) or shear, Love (L), and Rayleigh (R) waves using time and frequency domain parameters mapped on a 2D mapping interpretation scheme. The SWEDA proved automated heterogeneous surface adaptability, multi-clustered sensing, ubiquitous monitoring with dynamic Savitzky-Golay filtering and detection using nine optimized sequential and structured event characterization techniques. Furthermore, situation-conscious (context-aware) and automated computation of short-time average over long-time average (STA/LTA) triggering parameters by peak-detection and run-time scaling arrays with manual computation support were achieved. - 2019 by the authors.Funding: This publication was made possible by the NPRP grant # 8-1781-2-725 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

A real-time early warning seismic event detection algorithm using smart geo-spatial bi-axial inclinometer nodes for Industry 4.0 applications

Earthquakes are one of the major natural calamities as well as a prime subject of interest for seismologists, state agencies, and ground motion instrumentation scientists. The real-time data analysis of multi-sensor instrumentation is a valuable knowledge repository for real-time early warning and trustworthy seismic events detection. In this work, an early warning in the first 1 micro-second and seismic wave detection in the first 1.7 milliseconds after event initialization is proposed using a seismic wave event detection algorithm (SWEDA). The SWEDA with nine low-computation-cost operations is being proposed for smart geospatial bi-axial inclinometer nodes (SGBINs) also utilized in structural health monitoring systems. SWEDA detects four types of seismic waves, i.e., primary (P) or compression, secondary (S) or shear, Love (L), and Rayleigh (R) waves using time and frequency domain parameters mapped on a 2D mapping interpretation scheme. The SWEDA proved automated heterogeneous surface adaptability, multi-clustered sensing, ubiquitous monitoring with dynamic Savitzky-Golay filtering and detection using nine optimized sequential and structured event characterization techniques. Furthermore, situation-conscious (context-aware) and automated computation of short-time average over long-time average (STA/LTA) triggering parameters by peak-detection and run-time scaling arrays with manual computation support were achieved. - 2019 by the authors.Funding: This publication was made possible by the NPRP grant # 8-1781-2-725 from the Qatar National Research Fund (a member of Qatar Foundation). The statements made herein are solely the responsibility of the authors.Scopu

Hypocalcémie post-thyroïdectomie

Introduction : L’hypocalcémie est la complication la plus préoccupante de la thyroïdectomie totale. Elle impose un traitement substitutif et un suivi à vie. Objectifs : Le but de cette étude est d’évaluer l’incidence de l’hypocalcémie après chirurgie et d’étudier sa corrélation avec les caractéristiques cliniques, biologiques et le type de chirurgie pratiqué. Matériels et méthodes : Etude rétrospective portant sur 488 cas de thyroïdectomies, opérées entre 1992 et 1996. L’hypocalcémie est définie par une calcémie inférieure à 80 mg/l «2 mmol/l ». Les patients, toujours dépendants d’un traitement substitutif un an après la chirurgie, ont été considérés comme ayant une hypocalcémie définitive. Résultats : Dans notre étude, 368 patients ont eu une thyroïdectomie totale et 120 ont eu une thyroïdectomie subtotale. Le goitre multinodulaire était la pathologie la plus fréquente, noté dans 359 cas, suivie des cancers thyroïdiens noté dans 83 cas. L’hypocalcémie postopératoire a été retrouvée chez 54 patients (11,06%) dont 25 étaient asymptomatique. Cette hypocalcémie s’est révélée définitive chez 14 d’entre eux (2,8%). Nous n’avons pas trouvé de corrélation statistiquement significative entre l’hypoparathyroïdie définitive et les caractéristiques cliniques biologiques et le type de chirurgie.Conclusion : Dans la plupart des cas, l’hypocalcémie est liée à un hypoparathyroïdisme transitoire, secondaire au traumatisme ou à la dévascularisation des parathyroïdes. L’hypoparathyroïdie définitive est rare, elle est toujours secondaire à une lésion irréversible des parathyroïdes. Les caractéristiques cliniques initiales des patients et les examens biologiques précoces ne permettent pas de prédire l’évolution.Mots-clés : Thyroïde, chirurgie, hypocalcémie, parathyroïde