Réseaux de régulation chez Escherichia coli

L'adaptation d'une bactérie aux changements de son environnement est contrôlée par un réseau de régulation large et complexe, faisant intervenir de nombreux acteurs et modules différents. Dans ce travail, nous avons étudiés un module de régulation spécifique, contrôlant l'adaptation de la bactérie Escherichia coli à un changement de sources de carbone. Dans un milieu contenant du glucose et de l'acétate, la croissance est divisée en deux phases : les bactéries utilisent préférentiellement le glucose et commencent à métaboliser l'acétate qu'après l'épuisement du glucose. En effet, la présence du glucose réprime la transcription d'un gène nécessaire à la croissance sur acétate, le gène acs (codant pour l'acétyl-CoA synthétase). Le mécanisme régulateur fait intervenir le facteur de transcription Crp-AMPc et le système de transfert de phosphate (PTS), qui permet l'import du glucose. Plusieurs modèles décrivent en détail la cascade de réactions moléculaires à l'origine de cette répression catabolique . Cependant, certaines de nos observations expérimentales ne sont pas correctement prédites par les modèles actuels. Ces modèles doivent être révisés ou complétés. L'outil majeur que nous employons pour les expériences est la fusion transcriptionnelle : une région promotrice fusionnée en amont d'un gène rapporteur (GFP, luciferase). Avec ces constructions, nous mesurons la dynamique de l'expression génique dans différentes souches (mutants) et différentes conditions environnementales. Les observations à l'échelle de la population sont corroborées par des mesures similaires à l'échelle de la cellule unique. Nous utilisons cette même technologie pour construire de petits systèmes synthétiques qui sondent davantage le phénomène de répression catabolique. Nous avons ainsi créé un interrupteur génétique dont le fonctionnement est contrôlé par le flux glycolytique et nous avons construit un petit système de communication intercellulaire basé sur la molécule AMPc. Enfin, nous proposons une manière originale de mesurer l'état métabolique des cellules en utilisant la dépendance énergétique de la luciferase.The adaptation of bacteria to changes in their environment is controlled by a large and complex regulatory network involving many different actors and modules. In this work, we have studied a specific module controlling the adaptation of Escherichia coli to a change in carbon sources. In a medium containing glucose and acetate, growth is divided into two phases : the bacteria preferentially use glucose and start to metabolize acetate only after glucose exhaustion. Indeed, the presence of glucose represses the transcription of a gene needed for growth on acetate : the acs gene (coding for acetyl-CoA synthetase). The regulatory mechanism involves the Crp-cAMP regulator and the phosphate transfer system (PTS), which is responsible for glucose import. Several models describe the cascade of molecular reactions responsible for this catabolite repression . However, our work shows that many of our experimental observations are incorrectly predicted by current models. These models have to be amended.We use transcriptional fusion, i.e., the fusion of a promoter region upstream of a reporter gene (GFP, luciferase), to measure the dynamics of gene expression in different genetic backgrounds and environmental conditions. Observations at the population level are corroborated by similar measurements at the single cell level. We use this same technology to construct small synthetic systems that probe further aspects of the phenomenon of catabolite repression. We have thus created a genetic toggle switch controlled by the glycolytic flux and we have built an inter-cellular communication system mediated by cAMP. Finally, we propose a novel way to measure the metabolic state of cells by using the energy dependence of the luciferase enzyme.SAVOIE-SCD - Bib.électronique (730659901) / SudocGRENOBLE1/INP-Bib.électronique (384210012) / SudocGRENOBLE2/3-Bib.électronique (384219901) / SudocSudocFranceF

Historia universal de la Iglesia

Contiene: Vol. I. (XXVIII, 384 p.) -- vol. II. (444 p.) -- vol. III. (455 p. , [1] h. de map. pleg.) -- vol. IV (486 p.)Mode of access: Internet

Application of the reversed LISS-DF technique in an elderly patient to salvage infection-related failure of trochanteric fracture fixation.

Failure of cephalomedullary fixation in geriatric trochanteric fractures is a potential complication. Attempts have been made to optimize the implant fixation (e. g. cement augmentation) and several factors (e. g. malreduction, tip apex distance) have been identified as risk factors for failure. Nevertheless, if intramedullary fixation fails, it is often associated with bone defects in mostly preexisting poor bone-stock. Accordingly, conversion to total hip arthroplasty (THA) is recommended by some authors as the only valid treatment option. However, in specific situations (e. g. implant associated infection) conversion to THA might be less reasonable than an attempt to re-osteosynthesis. This article reports on the successful use of a reversed contralateral LISS-DF (LISS for the distal femur, DePuy Synthes, Zuchwil, Switzerland) application after failed cephalomedullary fixation and failed re-osteosynthesis using a blade plate in a trochanteric fracture in an elderly patient with additional implant associated infection

Effect of C-Clamp Application on Hemodynamic Instability in Polytrauma Victims with Pelvic Fracture.

Background and Objectives: C-clamp application may reduce mortality in patients with unstable pelvic fractures and hemodynamic instability. Decreasing C-clamp use over the past decades may have resulted from concerns about its effectiveness and safety. The purpose of this study was to document effective hemodynamic stabilization after C-clamp application by means of vital parameters (primary outcome parameter), and the subsequent effect on metabolic indices and volume management (secondary outcome parameters). Materials and Methods: C-clamp application was performed between 2014 and 2021 for n = 13 patients (50 ± 18 years) with unstable pelvic fractures and hemodynamic instability. Vital parameters, metabolic indices, volume management, and the correlation of factors and potential changes were analyzed. Results: After C-clamp application, increases were measured in systolic blood pressure (+15 mmHg; p = 0.0284) and mean arterial pressure (+12 mmHg; p = 0.0157), and a reduction of volume requirements (p = 0.0266) and bolus vasoactive medication needs (p = 0.0081) were observed. The earlier C-clamp application was performed, the greater the effect (p < 0.05; r > 0.6). Heart rate, shock index, and end-tidal CO2 were not significantly altered. The extent of base deficit, hemoglobin, and lactate did not correlate with changes in vital parameters. Conclusions: In the majority of hemodynamically unstable trauma patients not responding to initial fluid resuscitation and severe pelvic fracture, early C-clamp application had an additive effect on hemodynamic stabilization and reduction in volume substitution. Based on these findings, there is still a rationale for considering early C-clamp stabilization in this group of severely injured patients

The ideal site of cement application in cement augmented sacroiliac screw fixation: the biomechanical perspective.

PURPOSE To compare construct stability of cement augmented sacroiliac screws using two different cementation sites in a biomechanical fragility fracture model of the pelvis. METHODS A fracture model with an incomplete fracture of the sacral ala and complete fracture of the anterior pelvic ring mimicking a FFP IIB fragility fracture of the pelvis was established in five fresh frozen human cadaveric pelvises. Sacral fracture stabilization was achieved with bilateral 7.3 mm fully threaded sacroiliac screws. Cement augmentation was performed at the tip of the screw (body of S1; Group A) on one side, and at the midshaft of the screw (sacral ala; Group B) on the contralateral side. Biomechanical testing was conducted separately on both sides comprising cyclic loading of axial forces transferred through the tested hemipelvis from L5 to the ipsilateral acetabulum. Combined angular displacement in flexion and internal rotation ("gap angle"), angular displacement of the ilium in relation to the screw ("screw tilt ilium"), and screw tip cutout were evaluated. RESULTS Relative interfragmentary movements were associated with significantly higher values in group A versus group B for "gap angle" (2.4° vs. 1.4°; p < 0.001), and for "screw tilt ilium" (3.3° vs. 1.4°; p < 0.001), respectively. No significant difference was indicated for screw tip cutout between the two groups (0.6 mm [Group A] vs. 0.8 mm [Group B]; p = 0.376). CONCLUSION The present study demonstrated less fragment and screw displacements in a FFP IIB fracture model under physiologic cyclic loading by cement augmentation of sacroiliac screws at the level of the lateral mass compared to the center of vertebral body of S1

Terrestrial Very-Long-Baseline Atom Interferometry:Workshop Summary

This document presents a summary of the 2023 Terrestrial Very-Long-Baseline Atom Interferometry Workshop hosted by CERN. The workshop brought together experts from around the world to discuss the exciting developments in large-scale atom interferometer (AI) prototypes and their potential for detecting ultralight dark matter and gravitational waves. The primary objective of the workshop was to lay the groundwork for an international TVLBAI proto-collaboration. This collaboration aims to unite researchers from different institutions to strategize and secure funding for terrestrial large-scale AI projects. The ultimate goal is to create a roadmap detailing the design and technology choices for one or more km-scale detectors, which will be operational in the mid-2030s. The key sections of this report present the physics case and technical challenges, together with a comprehensive overview of the discussions at the workshop together with the main conclusions