Model and experiments to optimize co-adaptation in a simplified myoelectric control system

Objective. To compensate for a limb lost in an amputation, myoelectric prostheses use surface electromyography (EMG) from the remaining muscles to control the prosthesis. Despite considerable progress, myoelectric controls remain markedly different from the way we normally control movements, and require intense user adaptation. To overcome this, our goal is to explore concurrent machine co-adaptation techniques that are developed in the field of brain-machine interface, and that are beginning to be used in myoelectric controls. Approach. We combined a simplified myoelectric control with a perturbation for which human adaptation is well characterized and modeled, in order to explore co-adaptation settings in a principled manner. Results. First, we reproduced results obtained in a classical visuomotor rotation paradigm in our simplified myoelectric context, where we rotate the muscle pulling vectors used to reconstruct wrist force from EMG. Then, a model of human adaptation in response to directional error was used to simulate various co-adaptation settings, where perturbations and machine co-adaptation are both applied on muscle pulling vectors. These simulations established that a relatively low gain of machine co-adaptation that minimizes final errors generates slow and incomplete adaptation, while higher gains increase adaptation rate but also errors by amplifying noise. After experimental verification on real subjects, we tested a variable gain that cumulates the advantages of both, and implemented it with directionally tuned neurons similar to those used to model human adaptation. This enables machine co-adaptation to locally improve myoelectric control, and to absorb more challenging perturbations. Significance. The simplified context used here enabled to explore co-adaptation settings in both simulations and experiments, and to raise important considerations such as the need for a variable gain encoded locally. The benefits and limits of extending this approach to more complex and functional myoelectric contexts are discussed

Interaction between p22(phox) and Nox4 in the endoplasmic reticulum suggests a unique mechanism of NADPH oxidase complex formation.

The p22(phox) protein is an essential component of the phagocytic- and inner ear NADPH oxidases but its relationship to other Nox proteins is less clear. We have studied the role of p22(phox) in the TGF-beta1-stimulated H2O2 production of primary human and murine fibroblasts. TGF-beta1 induced H2O2 release of the examined cells, and the response was dependent on the expression of both Nox4 and p22(phox). Interestingly, the p22(phox) protein was present in the absence of any detectable Nox/Duox expression, and the p22(phox) level was unaffected by TGF-beta1. On the other hand, Nox4 expression was dependent on the presence of p22(phox), establishing an asymmetrical relationship between the two proteins. Nox4 and p22(phox) proteins localized to the endoplasmic reticulum and their distribution was unaffected by TGF-beta1. We used a chemically induced protein dimerization method to study the orientation of p22(phox) and Nox4 in the endoplasmic reticulum membrane. This technique is based on the rapamycin-mediated heterodimerization of the mammalian FRB domain with the FK506 binding protein. The results of these experiments suggest that the enzyme complex produces H2O2 into the lumen of the endoplasmic reticulum, indicating that Nox4 contributes to the development of the oxidative milieu within this organelle

Liposome-Mediated Cellular Delivery of Active gp91phox

International audienceBACKGROUND: Gp91(phox) is a transmembrane protein and the catalytic core of the NADPH oxidase complex of neutrophils. Lack of this protein causes chronic granulomatous disease (CGD), a rare genetic disorder characterized by severe and recurrent infections due to the incapacity of phagocytes to kill microorganisms. METHODOLOGY: Here we optimize a prokaryotic cell-free expression system to produce integral mammalian membrane proteins. CONCLUSIONS: Using this system, we over-express truncated forms of the gp91(phox) protein under soluble form in the presence of detergents or lipids resulting in active proteins with a "native-like" conformation. All the proteins exhibit diaphorase activity in the presence of cytosolic factors (p67(phox), p47(phox), p40(phox) and Rac) and arachidonic acid. We also produce proteoliposomes containing gp91(phox) protein and demonstrate that these proteins exhibit activities similar to their cellular counterpart. The proteoliposomes induce rapid cellular delivery and relocation of recombinant gp91(phox) proteins to the plasma membrane. Our data support the concept of cell-free expression technology for producing recombinant proteoliposomes and their use for functional and structural studies or protein therapy by complementing deficient cells in gp91(phox) protein

Synthetic receptors for the recognition and discrimination of post-translationally methylated lysines

Post-translational modifications (PTMs) describe the chemical alteration of proteins after their biosynthesis in ribosomes. PTMs play important roles in cell biology including the regulation of gene expression, cell-cell interactions and the development of different diseases. A prominent class of PTMs is the side chain methylation of lysine. For the analysis and discrimination of differently methylated lysines antibodies are widely used, though, methylated peptide and protein targets are known to be particularly difficult to be differentiated by antibody-based affinity reagents; an additional challenge can be batch-to-batch reproducibility. The application of mass spectrometry techniques for methyllysine discrimination requires a complex sample preparation and is not suited for working in cells. The desire to overcome above-named challenges promoted the development of synthetic receptor molecules that recognize and bind methyllysines. Such ‘artificial antibodies’ are of interest for a number of applications, e.g. as reagents in biochemical assays, for the isolation and purification of post-translationally methylated proteins and for the tracking of signalling pathways. Moreover, they offer new approaches in diagnostics and therapy. This review delivers an overview of the broad field of methyllysine binding and covers a wide range of synthetic receptors used for the recognition of methylated lysines including calixarenes, resorcinarenes, pillararenes, disulfide cyclophanes, cucurbituriles and acyclic receptors

Analyse biomécanique des transferts tendineux de la main (technique Tsugé) Modélisation des tensions Suivi longitudinal des patients

This study is lodged by a hospital program of clinical research. The objective was to develop a tool for hand motricity evaluation to characterize the motor reorganization associated with the restoration with a radial paralysis (Tsugé's technique). We showed that the minimization of the secondary moments was a robust biomechanical principle to explain the biomechanical interactions between the fingers. This principle has to be better explored in extension. The use of the biomechanical model showed the need for including the balance of the wrist in the procedure. The analysis of the motor reorganization shows the tendons tensions dynamic redistribution and the Co-contraction installation. The whole of this step opens interesting prospects for analysis of the motricity of the hand.Cette étude est hébergée par un programme hospitalier de recherche clinique. L'objectif était de développer un outil d'évaluation de la motricité de la main pour caractériser la réorganisation motrice associée à la restauration d'une paralysie radiale (technique de Tsugé). Nous avons montré que la minimisation des moments secondaires était un principe biomécanique robuste pour expliquer les interactions biomécaniques entre les doigts. Ce principe reste toutefois à mieux explorer en extension. L'utilisation du modèle biomécanique a montré la nécessité d'inclure l'équilibre du poignet dans la procédure. L'analyse de la réorganisation motrice montre la redistribution dynamique des tensions des tendons et la mise en place de co-contraction. L'ensemble de cette démarche ouvre des perspectives d'analyse de la motricité de la main intéressantes

La souffrance du compartiment fémoro-tibial interne : la place de l'arthroscopie thérapeutique

Contains fulltext : mmubn000001_069915687.pdf (publisher's version ) (Open Access)Promotor : W. Levelt184 p

Motor control theories improve biomechanical model of the hand for finger pressing tasks

International audienceBiomechanical models are a useful tool to estimate tendon tensions. Unfortunately, in previous fingers' models, each finger acts independently from the others. This is contradictory with hand motor control theories which show that fingers are functionally linked in order to balance the wrist/forearm joint with minimal tendon tensions. (i.e. principle of minimization of the secondary moments). We propose to adapt a hand biomechanical model according to this principle by including the wrist joint. We will determine whether the finger tendon tensions changed with the wrist joint added to the model