Pléchâtel – Les Landes de Lanserva

À environ 200 m au sud du site néolithique de La Hersonnais, plusieurs tertres à faible élévation et de forme oblongue avaient été signalés dans les Landes de Lanserva et l’un d’eux a fait l’objet d’une opération préventive en 1981 (rapport de Maurice Gautier, 1981), en prévision de la réalisation du nouvel axe routier Rennes-Nantes. En l’absence de structures et de mobilier, les sondages de reconnaissance s’étaient révélés négatifs sur ce premier tertre aujourd’hui disparu. Parallèlement à l..

Mouvements actifs, regules par le calcium, de la touffe ciliaire des cellules ciliées mecano-sensorielles de l'oreille interne. .

The dynamical behaviour of a hair bundle – the mechanosensitive organelle of the hair cells found in the inner ear – is rich. A hair bundle can oscillate spontaneously, “twitch” or simply relax in response to a force step.Using iontophoresis to affect the Ca2+ concentration near a hair bundle from the bullfrog’s sacculus and displacement-clamp measurements of the bundle’s force-displacement relations, we were able to reconcile these contrasting manifestations of active hair-bundle motility. We used Ca2+ and offsets of the bundle’s mean position to control the fraction of open transduction channels at steady state and thus the bundle’s operating point. In the case of non oscillatory hair bundles, we found that the polarity and kinetics of active hair-bundle movement evoked by a step stimulus depended on the bundle’s operating point in the nonlinear force- displacement relation. When the force-displacement relation displayed a region of negative stiffness, spontaneous hair-bundle oscillations arose when the hair bundle was required to operate within this unstable region.Only two ingredients are necessary to account for the various incarnations of active hair-bundle motility: non-linear gating compliance of the transduction apparatus and the Ca2+-regulated activity of the myosin-based adaptation motor. Numerical simulations successfully reproduced a wide range of observations from different experimental situations and animal species, thereby suggesting that only one force-generating mechanism is needed to describe the seemingly opposite movements that the hair-bundle can produce.Le comportement dynamique d’une touffe ciliaire (l’organelle mécano-sensible des cellules ciliées de l’oreille interne) est très varié. Une touffe ciliaire peut osciller spontanément, avoir une réponse de type « excitable » ou simplement relaxer en réponse à un échelon de force.En utilisant la iontophorèse pour modifier la concentration en calcium à proximité d’une touffe ciliaire du saccule de la grenouille taureau, et en mesurant les relations force/déplacements de cette organelle, nous sommes parvenus à réconcilier ces manifestations contrastées de sa motilité active. Nous utilisons le calcium et/ou des biais statiques appliqués à la position de la touffe ciliaire pour contrôler la probabilité d’ouverture au repos et par là, son point de fonctionnement. Dans le cas de touffes ciliaires non oscillantes, nous montrons que la polarité et la cinétique des mouvements ciliaires actifs observés en réponse à un échelon de stimulation dépendent du point de fonctionnement de la cellule. Lorsque la relation force/déplacement de la touffe ciliaire possède une région de raideur négative, des oscillations spontanées peuvent être déclenchées lorsque le point de fonctionnement est placé au sein de cette région instable.Seuls deux ingrédients sont nécessaires pour interpréter ces manifestations de la motilité ciliaire active : l’existence d’une relation force/déplacement non linéaire conséquence de l’activation mécanique directe des canaux de transduction, et l’activité du moteur d’adaptation, fondé sur les myosines et dépendant du calcium. Des simulations numériques reproduisent avec succès un grand nombre d’observations expérimentales, dans des conditions différentes et sur des animaux variés, suggérant qu’un seul mécanisme actif est nécessaire pour décrire toute la gamme des mouvements actifs observés sur les touffes ciliaires des cellules ciliées

Villevêque – Les Pâtures

Cette intervention a fait suite à des prospections systématiques le long du tracé de l’autoroute A11 Le Mans-Angers. À la confluence de deux petits ruisseaux, sur une légère pente exposée au nord, est apparue une zone de plus forte concentration de silex (avec nucléus à débitage lamellaire). Après décapage mécanique de la terre labourée, environ 48 m2 ont été fouillés. La nature générale des sédiments est un sable alluvionnaire reposant sur des marnes à ostracées. Dans la couche supérieure, d..

Saint-Sylvain-d’Anjou – Les Grandes Valinières

Sur le tracé de l’autoroute A11 Angers-Le Mans a été découvert puis fouillé un site rural du Ha ut Moyen Âge. Sur près de 2 ha, les vestiges se sont présentés sous forme de plus de mille structures en creux (trous de poteaux, silos, fosses, puits, sépultures, fossés). Plusieurs phases de construction en rendent l’interprétation difficile. Le site semble avoir été occupé intensivement dès l’époque mérovingienne jusqu’à la fin de la période carolingienne, avec des prolongements jusqu’au xiiie o..

LPS-Induced Systemic Inflammation Affects the Dynamic Interactions of Astrocytes and Microglia with the Vasculature of the Mouse Brain Cortex

The Neurovascular Unit (NVU), composed of glia (astrocytes, oligodendrocytes, microglia), neurons, pericytes and endothelial cells, is a dynamic interface ensuring the physiological functioning of the central nervous system (CNS), which gets affected and contributes to the pathology of several neurodegenerative diseases. Neuroinflammation is a common feature of neurodegenerative diseases and is primarily related to the activation state of perivascular microglia and astrocytes, which constitute two of its major cellular components. Our studies focus on monitoring in real time the morphological changes of perivascular astrocytes and microglia, as well as their dynamic interactions with the brain vasculature, under physiological conditions and following systemic neuroinflammation triggering both microgliosis and astrogliosis. To this end, we performed 2-photon laser scanning microscopy (2P-LSM) for intravital imaging of the cortex of transgenic mice visualizing the dynamics of microglia and astroglia following neuroinflammation induced by systemic administration of the endotoxin lipopolysaccharide (LPS). Our results indicate that following neuroinflammation the endfeet of activated perivascular astrocytes lose their close proximity and physiological cross-talk with vasculature, an event that most possibly contributes to a loss of blood–brain barrier (BBB) integrity. At the same time, microglial cells become activated and exhibit a higher extent of physical contact with the blood vessels. These dynamic responses of perivascular astrocytes and microglia are peaking at 4 days following LPS administration; however, they still persist at a lower level at 8 days after LPS injection, revealing incomplete reversal of inflammation affecting the glial properties and interactions within the NVU

JDLL: A library to run Deep Learning models on Java bioimage informatics platforms

We present JDLL, an agile Java library that offers a comprehensive toolset/API to unify the development of high-end applications of DL for bioimage analysis and to streamline their installation and maintenance. JDLL provides all the functions required to consume DL models seamlessly, without being burdened by the configuration of the Python-based DL frameworks, within Java bioimage informatics platforms. Moreover, it allows the deployment of pre-trained models in the Bioimage Model Zoo (BMZ) by shipping the logic to connect to the BMZ website, download and run a selected model inference

Imaging of Red-Shifted Light From Bioluminescent Tumors Using Fluorescence by Unbound Excitation From Luminescence

Early detection of tumors is today a major challenge and requires sensitive imaging methodologies coupled with new efficient probes. In vivo optical bioluminescence imaging has been widely used in the field of preclinical oncology to visualize tumors and several cancer cell lines have been genetically modified to provide bioluminescence signals. However, the light emitted by the majority of commonly used luciferases is usually in the blue part of the visible spectrum, where tissue absorption is still very high, making deep tissue imaging non-optimal, and calling for optimized optical imaging methodologies. We have previously shown that red-shifting of bioluminescence signal by Fluorescence Unbound Excitation from Luminescence (FUEL) is a mean to increase bioluminescence signal sensitivity detection in vivo. Here, we applied FUEL to tumor detection in two different subcutaneous tumor models: the auto-luminescent human embryonic kidney (HEK293) cell line and the murine B16-F10 melanoma cell line previously transfected with a plasmid encoding the Luc2 firefly luciferase. Tumor size and bioluminescence were measured over time and tumor vascularization characterized. We then locally injected near infrared emitting Quantum Dots (NIR QDs) in the tumor site and observed a red-shifting of bioluminescence signal by (FUEL) indicating that FUEL could be used to allow deeper tumor detection in mice

Bidirectional intraflagellar transport is restricted to two sets of microtubule doublets in the trypanosome flagellum

Intraflagellar transport (IFT) is the rapid bidirectional movement of large protein complexes driven by kinesin and dynein motors along microtubule doublets of cilia and flagella. In this study, we used a combination of high-resolution electron and light microscopy to investigate how and where these IFT trains move within the flagellum of the protist Trypanosoma brucei. Focused ion beam scanning electron microscopy (FIB-SEM) analysis of trypanosomes showed that trains are found almost exclusively along two sets of doublets (3–4 and 7–8) and distribute in two categories according to their length. High-resolution live imaging of cells expressing mNeonGreen::IFT81 or GFP::IFT52 revealed for the first time IFT trafficking on two parallel lines within the flagellum. Anterograde and retrograde IFT occurs on each of these lines. At the distal end, a large individual anterograde IFT train is converted in several smaller retrograde trains in the space of 3–4 s while remaining on the same side of the axoneme

Harmonin-b, an actin-binding scaffold protein, is involved in the adaptation of mechanoelectrical transduction by sensory hair cells

We assessed the involvement of harmonin-b, a submembranous protein containing PDZ domains, in the mechanoelectrical transduction machinery of inner ear hair cells. Harmonin-b is located in the region of the upper insertion point of the tip link that joins adjacent stereocilia from different rows and that is believed to gate transducer channel(s) located in the region of the tip link's lower insertion point. In Ush1cdfcr-2J/dfcr-2J mutant mice defective for harmonin-b, step deflections of the hair bundle evoked transduction currents with altered speed and extent of adaptation. In utricular hair cells, hair bundle morphology and maximal transduction currents were similar to those observed in wild-type mice, but adaptation was faster and more complete. Cochlear outer hair cells displayed reduced maximal transduction currents, which may be the consequence of moderate structural anomalies of their hair bundles. Their adaptation was slower and displayed a variable extent. The latter was positively correlated with the magnitude of the maximal transduction current, but the cells that showed the largest currents could be either hyperadaptive or hypoadaptive. To interpret our observations, we used a theoretical description of mechanoelectrical transduction based on the gating spring theory and a motor model of adaptation. Simulations could account for the characteristics of transduction currents in wild-type and mutant hair cells, both vestibular and cochlear. They led us to conclude that harmonin-b operates as an intracellular link that limits adaptation and engages adaptation motors, a dual role consistent with the scaffolding property of the protein and its binding to both actin filaments and the tip link component cadherin-23

Objective comparison of particle tracking methods

Particle tracking is of key importance for quantitative analysis of intracellular dynamic processes from time-lapse microscopy image data. Because manually detecting and following large numbers of individual particles is not feasible, automated computational methods have been developed for these tasks by many groups. Aiming to perform an objective comparison of methods, we gathered the community and organized an open competition in which participating teams applied their own methods independently to a commonly defined data set including diverse scenarios. Performance was assessed using commonly defined measures. Although no single method performed best across all scenarios, the results revealed clear differences between the various approaches, leading to notable practical conclusions for users and developers