Epilepsy, Regulation of Brain Energy Metabolism and Neurotransmission

Seizures are the result of a sudden and temporary synchronization of neuronal activity, the reason for which is not clearly understood. Astrocytes participate in the control of neurotransmitter storage and neurotransmission efficacy. They provide fuel to neurons, which need a high level of energy to sustain normal and pathological neuronal activities, such as during epilepsy. Various genetic or induced animal models have been developed and used to study epileptogenic mechanisms. Methionine sulfoximine induces both seizures and the accumulation of brain glycogen, which might be considered as a putative energy store to neurons in various animals. Animals subjected to methionine sulfoximine develop seizures similar to the most striking form of human epilepsy, with a long pre-convulsive period of several hours, a long convulsive period during up to 48 hours and a post convulsive period during which they recover normal behavior. The accumulation of brain glycogen has been demonstrated in both the cortex and cerebellum as early as the pre-convulsive period, indicating that this accumulation is not a consequence of seizures. The accumulation results from an activation of gluconeogenesis specifically localized to astrocytes, both in vivo and in vitro. Both seizures and brain glycogen accumulation vary when using different inbred strains of mice. C57BL/6J is the most “resistant” strain to methionine sulfoximine, while CBA/J is the most “sensitive” one. The present review describes the data obtained on methionine sulfoximine dependent seizures and brain glycogen in the light of neurotransmission, highlighting the relevance of brain glycogen content in epilepsies

Influence de l'hétérogénéité du massif rocheux sur le calcul des contraintes in situ

RÉSUMÉ Parmi les diff´erentes techniques disponibles pour la mesure de contraintes dans les massifs rocheux, la technique du Doorstopper propose de nombreux avantages tant par la facilité de r´ealisation des mesures que par la capacit´e des mod`eles d’interpr´etation existant `a refl´eter le comportement des roches aux points de mesure. Se d´emarquant des autres, cette technique permet l’obtention du tenseur tridimensionnel des contraintes dans les zones tr`es fractur´ees ou ´etant le si`ege de pressions naturelles tr`es importantes. Bas´ee sur le principe de r´ecup´eration, cette technique consiste `a mesurer les d´eformations au fond d’un forage suite au relˆachement des contraintes y existant, relˆachement provoqu´e par le prolongement du forage. L’obtention du tenseur de contraintes tridimensionnel par la technique du Doorstopper requiert le forage de trois trous non parall`eles ainsi que la d´etermination des param`etres d’´elasticit´e du massif. Des am´eliorations r´ecentes ont permis de r´eduire le nombre de forages `a deux lorsque la m´ethode RPR est utilis´ee pour l’interpr´etation des mesures. Il existe deux approches sensiblement diff´erentes pour ´etablir le tenseur de contraintes tridimensionnel par la technique du Doorstopper, apr`es r´ecup´eration des d´eformations en fond des trous de forage : – soit en d´eterminant le tenseur de d´eformation 3D `a partir des tenseurs partiels de d´eformation, puis en ´etablissant le tenseur de contrainte 3D. Cette m´ethode, propos´ee par Gray et Toews, utilise des param`etres de d´eformabilit´e moyens ; – soit en d´eterminant le tenseur de contrainte 3D `a partir des tenseurs partiels de contrainte de pr´eforage aux points de mesure. Les param`etres de d´eformabilit´e de la roche propres `a chaque point de mesure sont utilis´es pour ´etablir les tenseurs partiels. La premi`ere approche est la plus utilis´ee dans le monde `a ce jour. Cependant, les hypoth`eses de travail, stipulant que le massif rocheux est homog`ene dans le volume concern´e par les mesures, tendent `a affaiblir ses r´esultats en milieu fortement h´et´erog`ene. La relation contraintes-d´eformations utilisant un seul couple de param`etres ´elastiques semble ˆetre le point faible de cette m´ethode. L’autre approche permet en revanche de rendre compte de l’h´et´erog´en´eit´e en associant `a chaque tenseur partiel de contrainte les caract´eristiques de la roche au point de mesure.----------ABSTRACT Among the different measurements techniques which can be used to establish the state of stress in rock mass, the doorstopper’s offers numerous advantages such as easy measurements realization or the ability of the interpretation models to reflect the rock behaviour at the measuring point. Distinguishing itself from the others, this technique enables to obtain the 3D stress tensor in highly fractured zones or in which natural pressure is very important. Overcoring stress measurements are based on the recovery principle which consists in measuring the deformations observed at the flat end of the borehole following the stress relief. Determining the in situ state of stress by the Doorstopper technique requires a minimum of three non parallel boreholes and the determination of elastic parameters of the rock mass. Recent improvements enable to reduce the number of boreholes to two when RPR method is used for measurements interpretation. There are two approaches roughly different to establish the stress tensor by the Doorstopper technique, after deformations recovery at the flat end of the borehole: – By determining the 3D deformation tensor from the partial deformation tensors, then by determining the 3D stress tensor. This Gray and Toews’ method uses average deformability parameters; – By determining the 3D stress tensor from the partial stress tensors at the measuring points. Different rock deformability parameters are used to establish the partial tensors. The first approach is the most current used nowadays. However, the working hypothesis, which mean that the rock mass is homogeneous in the volume involved in measurements, tend to weaken results in heterogeneous rocks. The fact of using a single couple of elastic parameters in the stress-deformation relation seems to be the weak spot of the method. On the other hand, the second approach enables to take in consideration heterogeneity by associating with each partial stress tensor the rock characteristics at the measuring point

Walking Behavior Change Detector for a “Smart” Walker

AbstractThis study investigates the design of a novel real-time system to detect walking behavior changes using an accelerometer on a rollator. No sensor is required on the user. We propose a new non-invasive approach to detect walking behavior based on the motion transfer by the user on the walker. Our method has two main steps; the first is to extract a gait feature vector by analyzing the three-axis accelerometer data in terms of magnitude, gait cycle and frequency. The second is to classify gait with the use of a decision tree of multilayer perceptrons. To assess the performance of our technique, we evaluated different sampling window lengths of 1, 3 an 5seconds and four different Neural Network architectures. The results revealed that the algorithm can distinguish walking behavior such as normal, slow and fast with an accuracy of about 86%. This research study is part of a project aiming at providing a simple and non-invasive walking behavior detector for elderly who use rollators

The arabidopsis RCC1 family protein TCF1 regulates freezing tolerance and cold acclimation through modulating lignin biosynthesis

Cell water permeability and cell wall properties are critical to survival of plant cells during freezing, however the underlying molecular mechanisms remain elusive. Here, we report that a specifically cold-induced nuclear protein, Tolerant to Chilling and Freezing 1 (TCF1), interacts with histones H3 and H4 and associates with chromatin containing a target gene, BLUE-COPPER-BINDING PROTEIN (BCB), encoding a glycosylphosphatidylinositol-anchored protein that regulates lignin biosynthesis. Loss of TCF1 function leads to reduced BCB transcription through affecting H3K4me2 and H3K27me3 levels within the BCB gene, resulting in reduced lignin content and enhanced freezing tolerance. Furthermore, plants with knocked-down BCB expression (amiRNA-BCB) under cold acclimation had reduced lignin accumulation and increased freezing tolerance. The pal1pal2 double mutant (lignin content reduced by 30% compared with WT) also showed the freezing tolerant phenotype, and TCF1 and BCB act upstream of PALs to regulate lignin content. In addition, TCF1 acts independently of the CBF (C-repeat binding factor) pathway. Our findings delineate a novel molecular pathway linking the TCF1-mediated cold-specific transcriptional program to lignin biosynthesis, thus achieving cell wall remodeling with increased freezing tolerance

Relevance of inverse method to characterize structure borne noise sources: application on an industrial case and comparison with a direct method

Le présent papier s'appuie sur le travail réalisé au sein du projet de recherche collaboratif TESSA (« Transfert des Efforts des Sources Solidiennes Actives »). L'une des tâches rattachées au projet TESSA consiste à caractériser la variabilité de mesures inter-laboratoires des forces de blocage sur une pompe à eau de moteur thermique. Ce papier décrit uniquement les mesures réalisées au sein du laboratoire Vibratec. Deux méthodes de mesure des efforts de blocage ont été mises en ?uvre : une mesure directe, à l'aide de capteurs d'efforts, faisant l'objet des mesures inter-laboratoire, ainsi que l'application d'une méthode inverse ne nécessitant pas d'utiliser de capteurs d'effort. Des tests de répétabilité et de reproductibilité ont été réalisés afin de quantifier les écarts de mesures au sein d'un même laboratoire en vue de l'analyse de la dispersion inter-laboratoire. Des montages répondants aux spécificités de chacune des deux méthodes ont été conçus : bloc très rigide en aluminium pour la méthode directe et un support dédié à la méthode inverse, avec notamment un fort recouvrement et amortissement modal dans la bande de fréquence d'intérêt. La comparaison des résultats obtenus par les deux méthodes montre que la méthode inverse est acceptable pour mesurer des efforts de blocage sur un banc « non rigide » et qu'il est ainsi envisageable de l'appliquer « in-situ », avec la source dans son environnement de fonctionnement réel

Functional characterisation of Arabidopsis phototropin 1 in the hypocotyl apex

Phototropin (phot1) is a blue light-activated plasma membrane-associated kinase that acts as the principal photoreceptor for shoot phototropism in Arabidopsis in conjunction with the signalling component Non-Phototropic Hypocotyl 3 (NPH3). PHOT1 is uniformly expressed throughout the Arabidopsis hypocotyl, yet decapitation experiments have localised the site of light perception to the upper hypocotyl. This prompted us to investigate in more detail the functional role of the hypocotyl apex, and the regions surrounding it, in establishing phototropism. We used a non-invasive approach where PHOT1-GFP (P1-GFP) expression was targeted to the hypocotyl apex of the phot-deficient mutant using the promoters of CUP-SHAPED COTYLEDON 3 (CUC3) and AINTEGUMENTA (ANT). Expression of CUC3::P1-GFP was clearly visible at the hypocotyl apex, with weaker expression in the cotyledons, whereas ANT::P1-GFP was specifically targeted to the developing leaves. Both lines showed impaired curvature to 0.005 μmol m-2 s-1 unilateral blue light, indicating that regions below the apical meristem are necessary for phototropism. Curvature was however apparent at higher fluence rates. Moreover, CUC3::P1-GFP partially or fully complemented petiole positioning, leaf flattening and chloroplast accumulation, but not stomatal opening. Yet, tissue analysis of NPH3 de-phosphorylation showed that CUC3::P1-GFP and ANT::P1-GFP mis-express very low levels of phot1 that likely account for this responsiveness. Our spatial targeting approach therefore excludes the hypocotyl apex as the site for light perception for phototropism and shows that phot1-mediated NPH3 de-phosphorylation is tissue autonomous and occurs more prominently in the basal hypocotyl

Mitochondrial permeabilization engages NF-κB-dependent anti-tumour activity under caspase deficiency

Apoptosis represents a key anti-cancer therapeutic effector mechanism. During apoptosis, mitochondrial outer membrane permeabilization (MOMP) typically kills cells even in the absence of caspase activity. Caspase activity can also have a variety of unwanted consequences that include DNA damage. We therefore investigated whether MOMP-induced caspase-independent cell death (CICD) might be a better way to kill cancer cells. We find that cells undergoing CICD display potent pro-inflammatory effects relative to apoptosis. Underlying this, MOMP was found to stimulate NF-κB activity through the downregulation of inhibitor of apoptosis proteins. Strikingly, engagement of CICD displays potent anti-tumorigenic effects, often promoting complete tumour regression in a manner dependent on intact immunity. Our data demonstrate that by activating NF-κB, MOMP can exert additional signalling functions besides triggering cell death. Moreover, they support a rationale for engaging caspase-independent cell death in cell-killing anti-cancer therapies

The initiator methionine tRNA drives secretion of type II collagen from stromal fibroblasts to promote tumor growth and angiogenesis

Summary: Expression of the initiator methionine tRNA (tRNAi Met) is deregulated in cancer. Despite this fact, it is not currently known how tRNAi Met expression levels influence tumor progression. We have found that tRNAi Met expression is increased in carcinoma-associated fibroblasts, implicating deregulated expression of tRNAi Met in the tumor stroma as a possible contributor to tumor progression. To investigate how elevated stromal tRNAi Met contributes to tumor progression, we generated a mouse expressing additional copies of the tRNAi Met gene (2+tRNAi Met mouse). Growth and vascularization of subcutaneous tumor allografts was enhanced in 2+tRNAi Met mice compared with wild-type littermate controls. Extracellular matrix (ECM) deposited by fibroblasts from 2+tRNAi Met mice supported enhanced endothelial cell and fibroblast migration. SILAC mass spectrometry indicated that elevated expression of tRNAi Met significantly increased synthesis and secretion of certain types of collagen, in particular type II collagen. Suppression of type II collagen opposed the ability of tRNAi Metoverexpressing fibroblasts to deposit pro-migratory ECM. We used the prolyl hydroxylase inhibitor ethyl- 3,4-dihydroxybenzoate (DHB) to determine whether collagen synthesis contributes to the tRNAi Met-driven pro-tumorigenic stroma in vivo. DHB had no effect on the growth of syngeneic allografts in wild-type mice but opposed the ability of 2+tRNAi Met mice to support increased angiogenesis and tumor growth. Finally, collagen II expression predicts poor prognosis in high-grade serous ovarian carcinoma. Taken together, these data indicate that increased tRNAi Met levels contribute to tumor progression by enhancing the ability of stromal fibroblasts to synthesize and secrete a type II collagen-rich ECM that supports endothelial cell migration and angiogenesis

Venetoclax causes metabolic reprogramming independent of BCL-2 inhibition

BH3-mimetics are a new class of anti-cancer drugs that inhibit anti-apoptotic Bcl-2 proteins. In doing so, BH3-mimetics sensitise to cell death. Venetoclax is a potent, BCL-2 selective BH3-mimetic that is clinically approved for use in chronic lymphocytic leukaemia. Venetoclax has also been shown to inhibit mitochondrial metabolism, this is consistent with a proposed role for BCL-2 in metabolic regulation. We used venetoclax to understand BCL-2 metabolic function. Similar to others, we found that venetoclax inhibited mitochondrial respiration. In addition, we also found that venetoclax impairs TCA cycle activity leading to activation of reductive carboxylation. Importantly, the metabolic effects of venetoclax were independent of cell death because they were also observed in apoptosis-resistant BAX/BAK-deficient cells. However, unlike venetoclax treatment, inhibiting BCL-2 expression had no effect on mitochondrial respiration. Unexpectedly, we found that venetoclax also inhibited mitochondrial respiration and the TCA cycle in BCL-2 deficient cells and in cells lacking all anti-apoptotic BCL-2 family members. Investigating the basis of this off-target effect, we found that venetoclax-induced metabolic reprogramming was dependent upon the integrated stress response and ATF4 transcription factor. These data demonstrate that venetoclax affects cellular metabolism independent of BCL-2 inhibition. This off-target metabolic effect has potential to modulate venetoclax cytotoxicity