2,421 research outputs found
Mr Alain Elkann Author and Journalist Italian Republic
No full textVisit by Mr Alain Elkann Author and Journalist Italian Republi
Suitability of hSC and hiPSC derived cardiomyocytes as in vitro cell model that represents the physiological conditions for cardiotoxicity screening
No full textAbstract: Cardiotoxicity is one of the most prevalent unwanted side effects of new drugs in development. To improve the early detection of these side effects, an in vitro model that captures the in vivo physiology is desired in the non-clinical safety screening of new drug compounds. A promising model are human induced pluripotent stem cell derived cardiomyocytes (hiPSC-CM). Starting from differentiated cells of a human donor, the cells are de-differentiated into a pluripotent state. The hiPSC cells can then be differentiated again into specific cell types such as cardiomyocytes (CM). These hiPSC-CMs express a broader repertoire of cardiac proteins than expected for heterologous cell expression systems, which overexpress one protein of interest. Therefore, a more physiological model is created. However, the model is still too immature compared to native CM as their morphology and electrophysiological parameters correspond more to an embryonic like state. The resting membrane potential (RMP) is for example more depolarised compared to mature CM, which can influence ion channel characteristics and possibly their pharmacological profile. Depolarization of the RMP is caused by a decreased expression of Kir2.1, as reported in literature, and/or due to a technical issue when recording AP data in the patch-clamp setup when large leak currents are present. Other factors that might affect ion channel pharmacology are auxiliary subunits that interact with the ion channel subunits or by changes in cellular conditions such as membrane cholesterol. In this thesis the Nav1.5 channel, responsible for the fast depolarization of the action potential (AP), was researched. Nav1.5 availability for activation was found to be dependent on the RMP as at membrane potentials more depolarized than -60 mV all channels were inactivated. RMP values, determined with the patch-clamp technique, were in isolated cells around -50 mV while hiPSC-CMs in syncytium had a RMP of approximately -70 mV, which is closer to the physiological RMP. The more hyperpolarised RMP reflected in a faster upstroke of the AP as more Nav1.5 channels were available. This indicates that pharmacological screening of drugs, targeting Nav1.5, will not be detected during AP recordings if the RMP is too depolarised. We also researched if the heterologous expression systems, expressing Nav1.5 alone or in co-expression with \u3b21, can be compared to the hiPSC-CM INa and if the pharmacological profile is changed. From our data we concluded that the hiPSC-CM model compared the most to the heterologous model expressing both Nav1.5 and its \u3b21 subunit and both had a similar pharmacological profile. Afterwards, the effect of membrane cholesterol on the repolarizing cardiac ion channels and their pharmacological profile for the drug quinidine was evaluated, in order to research the possible need for a hypercholesterolemia model in cardiotoxicity screening. Cholesterol is known to have an effect on ion channels and is elevated in hypercholesterolemia patients. However, 9 due to the broad effects of cholesterol on AP data it is difficult to translate the obtained and reported data from heterologous cell models to the hiPSC-CMs model. Perspectives are suggested for future research and to make a conclusion on the need for a hypercholesterolemia model in cardiotoxicity screening. In conclusion, the hiPSCCM model is a suitable model for cardiotoxicity screening when being precautious for its current limitations e.g. the RMP. It is therefore advised to use hiPSC-CM in a syncytium when wanting to analyse RMP values and AP data. High throughput systems which do not need access to the cell can be performed on isolated cells or monolayers but determination of the upstroke velocity can be used as quality control, as it is correlated to the RMP. It has to be noted, however, for researching the mechanisms of how an ion channel is modulated, due to a compound or cellular changes, that it is still advised to use heterologous expression models. The hiPSC-CM model is, at present, still immature and too variable but maturation studies are being performed to solve these limitations
Résister à la normalisation des conduites : Entretien avec Roland Gori, propos recueillis par Alain Policar
No full textCo-initiator of the call of calls denouncing the ideology of a neuroeconomic man in whose name the current reforms break and redial our jobs and tasks of care, social works, education, research, justice, information and culture, the author analyzes mainly the psychiatric knowledge and practice as facts of civilization.Co-initiateur de l'Appel des appels qui dénonce l'idéologie d'un «homme économique» au nom de laquelle les réformes actuelles défont et recomposent les métiers et les missions du soin, du travail social, de l'éducation, de la recherche, de la justice, de l'information et de la culture, l'auteur analyse ici principalement les savoirs et les pratiques psychiatriques comme «des faits de civilisation».Policar Alain, Gori Roland. Résister à la normalisation des conduites : Entretien avec Roland Gori, propos recueillis par Alain Policar. In: Raison présente, n°171, 3e trimestre 2009. Savoir, connaitre, agir. pp. 87-94
Acute en vertraagde geneesmiddel effecten op spanningsgevoelige kaliumkanalen
No full textAbstract: The voltage-dependent K\u207a (Kv) channel family is large compared to other ion channel families, owing to a diverse array of genes encoding different \u3b1-subunits. In some subfamilies, these subunits can "mix-and-match" to form functional tetrameric Kv channels, further expanding this channel family. As a result, Kv channels are involved in a wide range of (patho)physiological processes. Consequently, there is interest in developing selective drugs that target specific Kv channels. However, drug specificity remains a major challenge due to the homology within the Kv channel family. In parallel, safety pharmacology is increasingly incorporating a broader range of Kv channels to prevent adverse side effects in newly developed drugs. Current in vitro testing procedures primarily focus on acute drug effects, often overlooking delayed effects that manifest slowly and are not yet routinely included in drug screening. In this thesis, we investigate a potential new selective drug binding site in Kv channels, and the importance of optimizing experimental conditions to ensure reliable and relevant drug screening outcomes. Using the whole-cell voltage-clamp technique, we demonstrated that extracellular charge substitutions in the S1-S2 linker of the Kv1.5 channel significantly modulate its gating properties. Specifically, a charge reversal from positive to negative (R276E) shifted the voltage dependence of channel activation in the hyperpolarized direction, while the opposite reversal (E274K and E278K) shifted it in the depolarized direction. Notably, the sequence of the S1-S2 linker is highly variable among Kv1 channels, making this region a promising target for selective inhibition or activation of Kv channels. Additionally, we explored how the choice of expression system can influence the potency of a novel Kv1.3 inhibitor. Factors such as cell size, morphological characteristics, endogenous currents, and auxiliary proteins all contribute to the pharmacological response of Kv channels, highlighting the need to carefully select the most appropriate expression system for drug screening. Finally, we investigated delayed drug effects that impact the trafficking or degradation of channel proteins, leading to reduced expression of mature ion channels at the plasma membrane. These effects are often missed in early drug development and may only become apparent during later stages. We propose a potential method to accelerate the onset of delayed drug effects. Removing (fetal bovine) serum from the cell culture medium seems to increase the potency of a delayed-action compound. This PhD thesis aims to deepen our understanding of Kv channel pharmacology and the factors that modulate their function
Alain de Lille
No full textAlain de Lille (c. 1128-1202) was a French monk and the author of the very popular and influential Ars Praedicandi (Art of Preaching).https://mds.marshall.edu/sermonstudies_gallery/1001/thumbnail.jp
Illuminating voltage-gated ion channels and their allosteric coupling in slow inactivation processes
No full textAbstract: In this thesis, voltage-gated ion channels were studied both from a fundamental as a therapeutic viewpoint. In part I, the allosteric coupling between the selectivity filter and the activation gate of the U-type inactivating Kv2.1 and Kv3.1 channels was studied. With the obtained results, a role of the selectivity filter has been proven and more specifically for the second threonine residue of the signature sequence TTVGYG, similar to observations in C-type inactivating Kv channels. Secondly, the Shaker-IR-W434F mutant channel was studied as this channel is often considered as a model for C-type inactivation. However, here it is shown that the W434F mutation stabilizes Shaker in a non-conducting state that is not physiologically relevant. Most surprisingly, in the presence of an activation gate that does not close completely, the W434F-containing selectivity filter dilates during recovery of inactivation to the extend that NMDG conduction could be observed. In the second part of this thesis, the use of voltage gated ion channels as a target for an enhanced photothermal ablation technique was investigated. While several candidate antibodies were validated for binding their extracellular target specifically, a photothermal ablation protocol using gold nanoparticles was optimized for HEK293 and hiPSC-CMs
Mas-related G protein-coupled receptors : activations, interactions, and their role in inflammation
No full textAbstract: The largest family of membrane receptors, known as G protein-coupled receptors (GPCRs), are essential to cellular signaling and regulate physiological processes. Presently, ~35%\u201340% of US FDA-approved medications target GPCRs. A subfamily of GPCRs, Mas-related G protein-coupled receptors (MRGPRs), which belong to the \u3b4-group of the rhodopsin-like GPCRs, was discovered two decades ago. MRGPRs are expressed by small non-myelinated sensory neurons of the dorsal root ganglia and trigeminal ganglia, mast cells, neutrophils, and macrophages and are known to play a role in itch, pain, and pseudo-allergic drug reactions. Moreover, MRGPRs have been identified as mediators in the renin-angiotensin system and cardiovascular biology. In addition, literature suggests that MRGPRs are also involved in inflammatory processes. Despite the fact that humans express eight MRGPRs (MRGPRD to G and X1-X4), information about their activation, signaling pathways, and role in inflammation is insufficient, and most of them are still classified as orphans. Since MRGPRs are involved in itch, pain, and inflammation, which are important physiological processes, the goal of this PhD was to: i) examine the role of MRGPRs in inflammation biology; ii) decipher the activation mechanism of MRGPRs; and iii) elucidate the oligomeric interaction of MRGPRs. Firstly, it was investigated whether \u3b2-alanine or alamandine-activated MRGPRD induces interleukin-6 (IL-6) release. It was observed that \u3b2-alanine activated MRGPRD-induced IL-6 release via the G\u3b1q/Phospholipase C/NF-kB signaling pathway. Moreover, using IL-6 as a marker for MRGPRD activation, the mechanosensitivity of the MRGPRD and the effect of sterol derivatives, i.e., cholesterol and bile acids, on the activation of MRGPRD were established. Furthermore, it was discovered that the MRGPRD was constitutive (ligand-independent) active. In addition, it was discovered that methyl-\u3b2-cyclodextrin, which is known to remove sterols from the plasma membrane, triggered the MRGPRD-mediated IL-6 release. Secondly, in an effort to deorphanize MRGPRs, it was established that cysteine protease cathepsin S activates MRGPRD and MRGPRF. Lastly, using biophysical and biochemical techniques such as luciferase complementation, bioluminescence resonance energy transfer, and co-immunoprecipitation assays, the heteromeric interactions between MRGPRE and MRGPRF were unambiguously detected. Overall, in this doctoral thesis, the primary objective was to improve understanding of the involvement of MRGPRs in inflammatory biology, the activation mechanisms of MRGPRs, and the oligomeric interaction of MRGPRs
From knowledge to skills: training for transition jobs. Interview with Alain Grandjean
No full textInternational audienceAlain Grandjean is an economist and author specializing on green finance. He is also cofounder and partner of Carbone 4, a consultancy firm focusing on energy transition and adaptation to climate change. The interview first revolves around the academic content Alain Grandjean considers as the bare necessities to be taught in higher education, no matter the curriculum. This should take the form of a basic synthetic training which takes into account the major environmental issues without too much technicality as well as lessons in accounting and economics, which he considers essential. The interview also looks more specifically at engineering and business schools. Then Alain Grandjean shares his views on the effectiveness of different ways to engage for the transition -like radical individual lifestyle transformations and civil disobiedience. He also evokes the roles that trade unions as well as NGOS can play and he talks about collapsology
Justice et politique (24) - face A
No full textSéminaire dirigé par Alain Bancaud, Anne Boigeol, Henry Rousso et Francine Soubiran-Paillet. Enregistré à l'IHTP (Paris), entre 1995 et1998
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