Récupération d'Energie Biomécanique et Systèmes Autonomes

National audienceLa récupération d'énergie (Energy Harvesting) est une thématique en plein essor visant à utiliser l'énergie ambiante (lumière, vibrations, gradients thermiques) présente dans l'environnement direct de dispositifs électroniques (capteurs, équipements mobiles) pour les alimenter, de façon à prolonger leur durée de fonctionnement, voire à les rendre totalement autonomes. La récupération d'énergie est généralement mise en œuvre pour alimenter de petits systèmes électroniques tels que des capteurs autonomes communicants pour le transport, l'industrie ou l'habitat du fait des puissances récupérées assez faibles; appliquée au cas de l'Homme, la récupération d'énergie peut atteindre des puissances de plusieurs milliwatts voire de plusieurs watts permettant d'alimenter des systèmes plus complexes tels que des lecteurs MP3, des téléphones portables ou des systèmes de localisation GPS. De nombreuses sources d'énergie présentes dans l'environnement de l'Homme peuvent être exploitées: le soleil, le gradient thermique entre la peau et l'extérieur, la déformation des vêtements, les contraintes dans les chaussures... . Cet article se focalise plus particulièrement sur la récupération d'énergie mécanique issue du corps humain et présente des exemples de dispositifs et d'applications issus de l'état de l'art montrant que la récupération d'énergie est déjà une réalité; et qu'elle permettra sur le plus long terme d'alimenter des dispositifs placés directement à l'intérieur du corps humain tels que des implants médicaux ou des pacemakers

The trophectoderm acts as a niche for the inner cell mass through C/EBPα-regulated IL-6 signaling

IL-6 has been shown to be required for somatic cell reprogramming into induced pluripotent stem cells (iPSCs). However, how Il6 expression is regulated and whether it plays a role during embryo development remains unknown. Here, we describe that IL-6 is necessary for C/EBPα-enhanced reprogramming of B cells into iPSCs but not for B cell to macrophage transdifferentiation. C/EBPα overexpression activates both Il6 and Il6ra genes in B cells and in PSCs. In embryo development, Cebpa is enriched in the trophectoderm of blastocysts together with Il6, while Il6ra is mostly expressed in the inner cell mass (ICM). In addition, Il6 expression in blastocysts requires Cebpa. Blastocysts secrete IL-6 and neutralization of the cytokine delays the morula to blastocyst transition. The observed requirement of C/EBPα-regulated IL-6 signaling for pluripotency during somatic cell reprogramming thus recapitulates a physiologic mechanism in which the trophectoderm acts as niche for the ICM through the secretion of IL-6.Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved

Rôle de Dkk1 et Noggin pendant la différenciation de l'endoderme extraembryonnaire au cours du développement murin

A 3,5 jours de développement (E3.5), l'embryon de souris est composé d'une couche externe de trophectoderme (TE) entourant la cavité blastocélique et la masse cellulaire interne (MCI). La MCI comprend une population hétérogène de précurseurs d'épiblaste (Epi) et d'endoderme primitif (EPr) dans une configuration "poivre et sel". A E4.5, ces cellules ségrégent, les cellules d'EPr migrant vers la surface de la MCI pour former un épithélium. A E4.75 cet épithélium donne naissance à 2 tissus distincts : un épithélium d'endoderme viscéral (EP) et à l'endoderme pariétal (EP) qui migre le long du TE. Une transition épithélium-mésenchyme est impliquée dans la formation de l'EP. Je m'intéresse au rôle de Dkk1, un inhibiteur de la voie Wnt canonique et activateur de la voie Wnt/PCP, et Noggin, un inhibiteur des BMP, dans la différenciation de l'endoderme extraembryonnaire. J'ai montré que Dkk1 est un marqueur de l'EPr qui devient apicalement polarisé à E4.5. Son expression est ensuite restreinte aux cellules de l'EP. J'ai aussi montré que Noggin est exprimé dès la préimplantation puis dans l'EP et au niveau de la charnière EV-Ep. Par des expériences de perte et de gain de fonction des voies Wnt et BMP et en utilisant les souris mutantes j'ai analysé le rôle de ces deux facteurs dans la différenciation de l'endoderme extraembryonnaire.At 3.5 days of development (E3.5), the mouse embryo consists of an outer layer of trophectoderm (TE) surrounding the blastocelic cavity and the inner cell mass (ICM). The ICM is composed of intermingled populations of epiblast (Epi) and primitive endoderm (PrE) precursors, that sort to form two distinct tissues. At E4.75 this epithelium differentiates into visceral endoderm (VE) and parietal endoderm (PE) that migrates along TE. An epithelium-mesenchyme transition (EMT) is involved in PE formation while the VE is maintained as an epithelium. My work focuses on the role of Dkk1, a Wnt canonical pathway inhibitor and Wnt/PCP pathway activator, and Noggin, a BMP pathway inhibitor, in extraembryonic endoderm differentiation. I have shown that Dkk1 is a marker of PrE precursors and is apically polarised at E4.5. Afterwards, its expression is restricted to PE. Noggin is expressed during preimplantation and then in PE and EV-EP hinge. By gain and loss of fonction experiments of Wnt and BMP pathways and by using mutant mice, I studied the role of these two factors in extraembryonic endoderm differentiation

Fluorescent mRNA labeling through cytoplasmic FISH

International audienceRNA in situ hybridization (ISH) has been widely used in cell and developmental biology research to study gene expression. Classical ISH protocols use colorimetric staining approaches, such as the assay with nitro blue tetrazolium/5-bromo-4-chloro-3-indolyl-phosphate (NBT/BCIP), which do not allow the implementation of multiple probe analyses and do not enable investigators to achieve cellular resolution. Here we describe a protocol to determine the presence of target cytoplasmic RNA via cytoplasmic fluorescence ISH (cFISH), an approach that renders possible the visualization of specific RNA strands from the whole tissue down to the cell. This fluorescence technique, adapted here for use in mouse embryos, enables researchers to implement multiple labeling by combining several RNA probes and/or antibodies in immuno-cFISH. Depending on the options chosen, the protocol can be completed within 2 or 3 d

Le développement pré-implantatoire

Chapitre 18National audienc

Thermoelastic properties of microcracked polycrystals. Part II : The case of jointed polycrystalline TATB

International audienceThe thermoelastic responses of a cracked TATB polycrystal is modeled using Fourier-based numerical computations and linear homogenization estimates. The numerical method is based on a Fourier scheme previously investigated (Gasnier et al., 2018) and the homogenization schemes include a new self-consistent estimate recently developed for cracked polycrystals. The effect of various populations of intergranular and transgranular microcracks are compared, with special attention to thermal behavior in the percolating regime. A model of micro-cracks is proposed for the TATB material in its initial state and the variations of the volumetric expansion coefficient of the TATB polycrystal under thermal cycles, during cooling and heating, are interpreted

Expanding Actin Rings Zipper the Mouse Embryo for Blastocyst Formation

Transformation from morula to blastocyst is a defining event of preimplantation embryo development. During this transition, the embryo must establish a paracellular permeability barrier to enable expansion of the blastocyst cavity. Here, using live imaging of mouse embryos, we reveal an actin-zippering mechanism driving this embryo sealing. Preceding blastocyst stage, a cortical F-actin ring assembles at the apical pole of the embryo's outer cells. The ring structure forms when cortical actin flows encounter a network of polar microtubules that exclude F-actin. Unlike stereotypical actin rings, the actin rings of the mouse embryo are not contractile, but instead, they expand to the cell-cell junctions. Here, they couple to the junctions by recruiting and stabilizing adherens and tight junction components. Coupling of the actin rings triggers localized myosin II accumulation, and it initiates a tension-dependent zippering mechanism along the junctions that is required to seal the embryo for blastocyst formation. Expanding actin rings zipper the mouse embryo to seal it and allow formation of the blastocyst cavity.Fil: Zenker, Jennifer. Institute Of Molecular And Cell Biology; SingapurFil: White, Melanie D.. Institute Of Molecular And Cell Biology; SingapurFil: Gasnier, Maxime. Institute Of Molecular And Cell Biology; SingapurFil: Alvarez, Yanina Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Lim, Hui Yi Grace. Institute Of Molecular And Cell Biology; SingapurFil: Bissiere, Stephanie. Institute Of Molecular And Cell Biology; SingapurFil: Biro, Maté. Institute Of Molecular And Cell Biology; SingapurFil: Plachta, Nicolas. Institute Of Molecular And Cell Biology; Singapu

A Fourier-based numerical homogenization tool for an explosive material

Typo in Ref. 7 corrected, and acknowledgements addedInternational audienceThis paper describes the development of a numerical homogenization tool adapted to TATB-based pressed explosives. This is done by combining virtual microstructure modeling and Fourier-based computations. The polycrystalline microstructure is represented by a Johnson-Mehl tessellation model with Poisson random nucleation and anisotropic growth of grains. Several calculations are performed with several sets of available data for the thermoelastic behavior of TATB. Good agreement is found between numerical predictions and experimental data regarding the overall thermal expansion coefficient. The results are shown to comply with available bounds on polycrystalline anisotropic thermoelasticity. Finally, the size of the representative volume element is derived for the bulk, shear and volumetric thermal expansion moduli

A low power and efficient microcontroller-based extraction circuit for HVAC applications

International audienceIn this paper, we report a low power implementation of a Power Management Circuit (PMC) performed by means of a microcontroller unit (MCU) surrounded by discrete components. In the context of HVAC applications with the aim of converting rotational movements into electrical energy, a non-linear extraction technique is implemented by controlling a Flyback converter at the maximum voltage of a magnetoelectric harvester.Compared with the Standard Energy Harvesting (SEH) interface, a power gain up to 1.75 was measured at a frequency of 47 Hz and a Flyback efficiency up to 80% for an output power of 0.5 mW. This architecture contributes to increase the versatility of PMCs addressing lowly-coupled piezoelectric harvesters (PEHs)