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Letteratura scientifica selezionata sul tema "Microscopie cellulaire"

Autore: Grafiati

Pubblicato: 21 dicembre 2024

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Articoli di riviste sul tema "Microscopie cellulaire"

Laporte, Marine H., Éloïse Bertiaux, Virginie Hamel e Paul Guichard. "L’organisation native de la cellule révélée grâce à la cryo-microscopie à expansion". médecine/sciences 39, n. 4 (aprile 2023): 351–58. http://dx.doi.org/10.1051/medsci/2023052.

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Abstract (sommario):

La plupart des techniques d’imagerie cellulaire, telles que la microscopie photonique ou la microscopie électronique, nécessitent que l’échantillon biologique soit préalablement fixé par des agents chimiques, une étape qui est connue pour endommager l’organisation sub-cellulaire. Pour pallier à ce problème, la cryo-fixation, inventée il y a plus de 40 ans, consiste à vitrifier les échantillons biologiques afin de préserver leur état natif. Cette méthode n’avait cependant été que très peu utilisée en microscopie photonique. Dans cette revue, nous présentons en détail la microscopie d’expansion, une technique de super-résolution développée récemment et qui, couplée à la cryo-fixation, permet de visualiser l’architecture cellulaire au plus près de son état natif.

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Méry, Annabelle, e Michel Pucéat. "Visualisation de la différenciation cellulaire cardiaque par microscopie confocale". Journal de la Société de Biologie 198, n. 2 (2004): 145–51. http://dx.doi.org/10.1051/jbio/2004198020145.

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Arizono, Misa, e U. Valentin Nägerl. "Plus vive, plus nette : la microscopie STED du cerveau". Photoniques, n. 114 (2022): 36–39. http://dx.doi.org/10.1051/photon/202111436.

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La microscopie à super-résolution (SRM) désigne une nouvelle catégorie de techniques de microscopie optique qui permettent de surmonter la barrière de diffraction classique,- barrière qui a rendu difficile l’observation des structures et des activités qui constituent la base de la vie cellulaire biologique. La microscopie STED, qui est l'une des techniques SRM, a attiré l'attention des neurobiologistes, car elle permet de révéler la nanostructure des cellules cérébrales non seulement dans une boîte de Pétri, mais aussi à l'intérieur du tissu cérébral réel, voire dans le cerveau intact in vivo.

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Jouchet, Pierre, Abigail Illand, Guillaume Dupuis, Emmanuel Fort e Sandrine Lévêque-Fort. "Dépasser la limite de diffraction en microscopie de fluorescence". Photoniques, n. 108 (maggio 2021): 44–48. http://dx.doi.org/10.1051/photon/202110845.

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La microscopie de fluorescence est un outil de référence dans l’étude des systèmes biologiques, alliant la spécificité offerte par la fluorescence et la possibilité d’un suivi non invasif en milieu vivant. Cependant comme l’ensemble des techniques de microscopie, elle est soumise au phénomène de diffraction introduit par l’objectif, qui limite la résolution de l’instrument. Ce texte présente les différentes méthodes permettant de dépasser cette contrainte en associant développement instrumental en optique et contrôle de la photophysique des fluorophores afin de révéler l’organisation cellulaire à l’échelle nanométrique.

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Sentenac, Anne. "Améliorer la résolution de la microscopie optique de fluorescence". Photoniques, n. 114 (2022): 45–50. http://dx.doi.org/10.1051/photon/202111445.

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La microscopie de fluorescence est un outil majeur, en particulier pour étudier le fonctionnement du vivant au niveau cellulaire, mais sa résolution est limitée à quelques centaines de nanomètres. Ces vingt dernières années, différentes techniques ont été proposées pour descendre la résolution sous la barre des 100 nm. Cet article essaie de présenter leurs principes de manière unifiée.

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Giocondi, Marie-Cécile, Pierre Emmanuel Milhiet, Eric Lesniewska e Christian Le Grimellec. "Microscopie à force atomique : de l’imagerie cellulaire à la manipulation moléculaire". médecine/sciences 19, n. 1 (gennaio 2003): 92–99. http://dx.doi.org/10.1051/medsci/200319192.

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Illand, Abigail, Pierre Jouchet, Emmanuel Fort e Sandrine Lévêque-Fort. "Localisation nanométrique de molécules uniques par modulation du signal de fluorescence". Photoniques, n. 114 (2022): 30–35. http://dx.doi.org/10.1051/photon/202111430.

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Abstract (sommario):

La microscopie de localisation de molécules individuelles permet de dépasser la limite de diffraction, révélant ainsi l’organisation cellulaire à l’échelle nanométrique. Cette méthode reposant sur l’analyse spatiale du signal émis par les molécules, reste souvent limitée à l’observation d’objets biologiques à de faibles profondeurs, ou très peu aberrants. Nous montrons ici que l’introduction d’un paramètre temporel dans le processus de localisation via l’introduction d’une excitation modulée permet d’adresser ces limitations.

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Lévy, Daniel, Aurélie Di Cicco, Aurélie Bertin e Manuela Dezi. "La cryo-microscopie électronique révèle une nouvelle vision de la cellule et de ses composants". médecine/sciences 37, n. 4 (aprile 2021): 379–85. http://dx.doi.org/10.1051/medsci/2021034.

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La cryo-microscopie électronique (cryo-EM) est une technique d’imagerie du vivant qui prend désormais une place prépondérante en biologie structurale, avec des retombées en biologie cellulaire et du développement, en bioinformatique, en biomédecine ou en physique de la cellule. Elle permet de déterminer des structures de protéines purifiées in vitro ou au sein des cellules. Cette revue décrit les principales avancées récentes de la cryo-EM, illustrées par des exemples d’élucidation de structures de protéines d’intérêt en biomédecine, et les pistes de développements futurs.

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Perrot, J. L., B. Labeille e F. Cambazard. "Visualisation de la nécrose cellulaire d’un carcinome basocellulaire traité par photothérapie dynamique en microscopie confocale". Annales de Dermatologie et de Vénéréologie 138, n. 12 (dicembre 2011): A211. http://dx.doi.org/10.1016/j.annder.2011.10.211.

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Perrot, J. L., A. Biron, E. Couty, L. Tognetti, C. Couzan, R. Rossi, P. Rubegni e E. Cinotti. "Premiers cas de corrélation parfaite à l’échelle cellulaire entre image de microscopie confocale in vivo et dermatoscopie". Annales de Dermatologie et de Vénéréologie 145, n. 12 (dicembre 2018): S186. http://dx.doi.org/10.1016/j.annder.2018.09.261.

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Più fonti

Tesi sul tema "Microscopie cellulaire"

Mercier, Luc. "Disséquer la cascade métastatique par des approches innovantes d'imagerie cellulaire". Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAJ091/document.

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La métastase peut être considérée comme le produit final d’un processus à la fois biologique mécanique et chimique où les cellules cancéreuses disséminent dans l’organisme pour envahir un nouvel organe à distance en s’établissant dans un nouvel microenvironnement tissulaire. Bien que les métastases soient la principale cause de décès liée au cancer, les principaux mécanismes impliqués dans ce processus restent à élucider. La communauté scientifique manque de techniques d’imagerie adaptées pour disséquer avec la plus haute résolution possible le comportement des cellules tumorales in vivo. Par conséquent, le but principal de ma thèse a été de développer une approche d’imagerie intravitale non-invasive appliquée à la souris. Cette approche a été inclue dans le développement d’un protocole de microscopie corrélative intravitale permettant l’étude de cellules tumorales à différentes échelles dans leur environnement naturel. Ce protocole a été utilisé dans l’étude de cellules invasives tumorales uniques dans l’oreille et le cerveau de la souris. Le but était de décrire les détails des protrusions cellulaires ainsi que les interactions cellule-matrice lors de l’invasion et l’intravasation de cellules cancéreuses
Metastasis can be considered as the end product of a multistep bio-mechano-chemical process where cancer cells disseminate to anatomically distant organs and home and establish themselves in a new tissue microenvironment. Although metastasis is the leading cause of cancer-related death, the main cellular mechanisms enabling this process remain to be elucidated. Importantly, the scientific community lacks adapted imaging technologies to accurately dissect, at the highest resolution possible, tumor cell behavior in vivo. Therefore, the main goal of my PhD thesis was to develop an intravital and non-invasive imaging approach to track tumor progression in the living mouse. This approach was included in the development of an intravital Correlative Light and Electron Microscopy protocol allowing to track tumor cells at different scales in their natural environment. It was used to study single invasive tumor cells in the mouse ear and brain and to describe the details of cell protrusions and cell-matrix interactions during invasion and intravasation of cancer cells

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Moreaux, Laurent. "Microscopie par génération du second harmonique : applications à l'imagerie cellulaire". Paris 11, 2002. http://www.theses.fr/2002PA112113.

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La microscopie bi-photonique est la forme de microscopie non linéaire la plus populaire pour l'imagerie des cellules biologiques. Une forme moins populaire basée sur la génération du second harmonique (SHG) par des surfaces ou par des tissus endogènes a été cependant utilisée plusieurs années avant l'invention de la microscopie bi-photonique. En raison des difficultés d'interprétation du signal, la microscopie SHG a été peu exploitée jusqu'à un regain d'intérêt récent. Cette thèse présente une analyse expérimentale et théorique de la microscopie par génération du second harmonique utilisée pour l'imagerie des membranes biologiques dans lesquelles des sondes exogènes sont insérées. En particulier, ce travail démontre la possibilité de combiner à la fois SHG et fluorescence bi-photonique pour l'imagerie des membranes dans lesquelles des chromophores sont insérés. Nous montrons que les résolutions deux microscopies sont identiques, ce qui rends les deux modes de contrastes optiques facilement combinables dans un seul et même instrument. Grâce à un modèle basé sur la théorie des antennes, nous avons établi l'expression de la puissance totale rayonnée, de la distribution angulaire et des propriétés de polarisation du SHG en champ lointain dans le cas de chromophores parfaitement alignés ou non dans la membrane. De plus, nous avons défini une section efficace SHG afin de permettre un comparaison direct avec la fluorescence induite par absorption à deux photons. Malgré leurs similitudes, la SHG et la fluorescence bi-photonique sont des phénomènes intrinsèquement différents. Le premier est cohérent et le second ne l'est pas. Nous montrons que cette différence offre de nouvelles possibilités pour l'étude de l'organisation moléculaire. Enfin, nous présentons une technique permettant d'étudier la nature de la réponse à un champ électrique trans-membranaire dans le but d'une application directe de la microscopie par SHG à l'imagerie des potentiels membranaires
By far the most well known form of non-linear microscopy is based on two-photon excited fluorescence (TPEF), which bas now become a laboratory standard for biological imaging. A lesser known form of this microscopy, however, was used several years prior to the invention of TPEF microscopy, based on the generation of second harmonic light either from surfaces or from endogenous tissue structures. Because of difficulties in signal, second-harmonic generation (SHG) microscopy has gone by relatively unnoticed until only very recently. This work present a detailed experimental and theoretical analysis of the generation of second-harmonic radiation from biological membranes labeled with exogenous markers. We demonstrate that simultaneous second-harmonic generation and two-photon excited fluorescence can be used to image biological membranes labeled with properly designed chromophore. Moreover, we show that spatial resolutions provided by SHG and TPEF microscopies are commensurate, meaning that the two contrast modes can very often be conveniently derived from the same instrument. Based on phased-array antennas model, we derive expressions for the SHG radiation power, angular distribution and polarization dependence in the cases of ideal or non-ideal molecular alignment in the membrane. We define an SHG cross-section similar to that used in two-photon excited fluorescence to allow direct comparison. Despite their similarities, however, SHG and TPEF are fundamentally different phenomena. The first is coherent whereas the second is not. We demonstrate, moreover, that this basic difference provides a unique window into molecular spatial organization which is inaccessible to fluorescence. At least, we present a screening technique to quantify and ascertain the nature of the second-harmonic generation response of chromophores to a trans-membrane electric field. These results are specifically directed to the optimisation of membrane potential response in SHG microscopy

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Colomb, Evelyne. "Etude du cycle cellulaire de l'épithelium mammaire humain par microscopie quantitative". Aix-Marseille 2, 1991. http://www.theses.fr/1991AIX22026.

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Le cycle cellulaire d'une cellule somatique eucaryote type est caracterise par quatre phases successives: g1, s, g2 et m. La progression de la cellule dans le cycle est etroitement surveillee par des controles extracellulaires et intracellulaires. Notamment, en phase g1, des facteurs extracellulaires engendres par des interactions moleculaires et cellulaires determinent l'etat proliferant/non proliferant de la cellule. Des perturbations de ces processus de regulation peuvent entraine la naissance de cellules cancereuses: ces cellules se reproduisent malgre les restrictions et finissent par envahir et coloniser des sites normalement reserves a d'autres types cellulaires. Pour aborder le role des interactions cellulaires dans la regulation de la proliferation cellulaire, une methodologie a ete developpee a partir du systeme d'analyse microphotometrique a balayage automatique (samba 200), pour determiner la phase du cycle (g0/g1, g2 ou m) des cellules de l'epithelium mammaire humain en culture, tout en preservant leur topographie cellulaire. In situ, les cellules sont colorees par la reaction nucleale stchiometrique de feulgen. La mesure de 15 parametres caracteristiques de la teneur en adn et de la texture nucleaire, sur chaque noyau suivie d'analyses multiparametriques des donnees permet de determiner la phase de chaque cellule analysee, et d'evaluer la repartition d'une population cellulaire dans les differentes phases. Cette methode s'applique parfaitement aux populations cellulaires presentant un profil de distribution de leur teneur en adn unimodal, a condition toutefois que l'integrite du noyau soit preservee. Elle a permis non seulement d'etudier l'effet de diverses molecules (hormones, facteurs de croissance, anthracyclines) sur la progression des cellules dans le cycle, mais aussi de detecter des modifications de la morphologie nucleaire consecutives a un traitement par les anthracyclines. Enfin, une methode a ete elaboree pour reconnaitre et denombrer les cellules sensibles aux anthracyclines

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Valon, Léo. "Contrôle Optogénétique de la Polarité Cellulaire". Thesis, Paris, Ecole normale supérieure, 2014. http://www.theses.fr/2014ENSU0008/document.

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Dans cette thèse, nous avons concentré notre étude sur les mécanismes qui génèrent la polarité cellulaire, en particulier dans le cas de la migration cellulaire. Malgré les derniers développements concernant l’observation de l’activité des RhoGTPases, les principes qui dictent la capacité des cellules à coordonner plusieurs modules de signalisation en parallèle ne sont toujours pas compris. L’optogénétique est un outil d’intérêt pour disséquer ces réseaux de signalisation à partir de la création d’une perturbation dont les caractéristiques spatiotemporelles sont contrôlées. Tout d’abord, à partir de la caractérisation des différents processus biophysiques en jeu, nous avons établi les relations quantitatives entre l’illumination et les gradients moléculaires que l’on induit. Nous avons déterminé qu’il est possible de créer des gradients subcellulaires avec une résolution spatiale de l’ordre de 5 μm et temporelle d’environ 3 minutes Ensuite, nous avons utilisé cette approche optogénétique pour contrôler l’activité de Cdc42, Rac1 et RhoA. Nous avons caractérisé les effets subcellulaires de l’activation de ces RhoGTPases en utilisant l’activité de membrane, les changements de forme cellulaire et leurs déplacements comme rapporteurs de la polarisation et de la migration. Nous avons ainsi montré qu’une activation locale de RhoGTPase permet la réorganisation interne des cellules jusqu’à générer un phénotype de migration.Enfin, nous avons caractérisé les effets d’une activation locale de RhoA sur différents acteurs moléculaires comme les points focaux d’adhésion, l’actine et les moteurs moléculaires myosines. Nous avons mesuré alors la dynamique de l’intégration des points focaux dans le cytosquelette et analysé la réponse du réseau d’acto-myosine au cours d’évènements de rétraction.Notre approche optogénétique couple le contrôle d’une perturbation à la mesure de la réponse cellulaire simultanément de manière directe et reproductible. Elle apporte une méthode pour contrôler la polarité cellulaire et une manière de disséquer des réseaux de signalisation à l’échelle subcellulaire
In this thesis we focus on the mechanisms that establish cell polarization, particularly during cell migration. Despite latest developments that enable visualization of RhoGTPases activity, the underlying principles dictating the cell’s ability to coordinates multiple signaling modules is still unclear. Optogenetic methods have been recognized as promising tools to dissect these intracellular signaling networks by allowing perturbations to be spatially and temporally controlled. We established the quantitative relationship between illumination patterns and the corresponding gradients of induced signaling activity through the characterization of the biophysical properties of CRY2/CIBN. We determined that it is possible to create subcellular gradients of recruited proteins of different shapes of choice up to spatial resolutions of 5μm and temporal ones of ca. 3 minutes.We applied the aforementioned optogenetic approach as a means to perturb the activity of cdc42, Rac1 and RhoA. We characterized the effects of subcellular activation of those RhoGTPases using membrane activity, cell shape changes and cell displacement as reporters of cell polarization and migration. We show that localized activation of RhoGTPases can trigger cellular organization and drive the cell into a migrating state.We also characterized the effects of local activation of RhoA on different cellular effectors as focal adhesion complexes, actin filaments and myosin molecular motors. We measured the dynamics of the newly formed focal adhesion complexes and the acto-myosin complex during retraction events.Altogether, our optogenetic methodology enables simultaneous measurement of the imposed perturbation and the cell response in a straightforward and reproducible way. It provides a quantitative way to control cell polarity and a step forward in the dissection of subcellular signaling networks

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Combes, Julien. "Etude de l'adhésion d'ostéoblastes sur substituts apatitiques par microscopie à force atomique". Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2009. http://tel.archives-ouvertes.fr/tel-00445705.

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L'objectif de cette étude s'inscrit dans une démarche de développement de céramiques apatites phosphocalciques et de leur évaluation biologique. Les matériaux étudiés sont des hydroxyapatites silicatées ou carbonatés denses en monophasées. Il s'agit d'un travail interdisciplinaire, qui va de la synthèse et la mise en œuvre de matériaux céramiques à la biomécanique cellulaire et les essais de cultures cellulaires in vitro. La dimension originale du projet concerne le suivi de la réponse des cellules osseuses déposées sur ces céramiques par l'indentation à l'aide d'un AFM. Ces travaux montrent d'une part, que la bioactivité des matériaux étudiés était semblables et d'autre part, que la relaxation de cellules ensemencées sur TA6V et hydroxyapatite stochiométrique suivent une loi puissance (exposant ≈ 0.2) sur 2-200 secondes. La méthode originale utilisée montre par ailleurs que la relaxation d'une fibre d'actine est différentiable de la relaxation de la membrane cellulaire.

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Caillat, Ludovic. "Nano-sondes optiques à forte non-linéarite pour l'imagerie cellulaire à haute résolution". Paris 6, 2013. http://www.theses.fr/2013PA066059.

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L’un des enjeux du XXI siècle concerne la compréhension de la machine cellulaire. Le principal problème à l’heure actuelle que rencontrent les biologistes est la diffraction due à la nature ondulatoire de la lumière qui limite la résolution des instruments optiques. Dans cette thèse, nous avons montré pour la première fois que l’up-conversion présent dans les nanoparticules dopées terres rares pouvaient dépasser la limite d’Abbe. Nous avons montré que la résolution latérale dans notre microscope pouvait dépasser λ/5 bien supérieure à la limite d’abbe. Ce concept permet d’atteindre des résolutions proches de 180 nm pour des processus à 4 photons. Ces résultats sont intéressants, ils permettent d’obtenir des résolutions proches d’un microscope confocal, tout en conservant l’excitation infrarouge de faible puissance de l’ordre de quelques µW, permettant de nous s’affranchir d’un laser femto-seconde, et donc de développer un microscope multi-photon à bas cout
Major bottleneck in microscopic imaging is the limited lateral resolution due to the diffraction of light. To overcome this limit, here we demonstrate the up-conversion process in the rare earth doped nanoparticles, which may serve as an original fluorescence source mechanism. Rare earth doped nanoparticles, have been reported to serve as efficient bio-labels for cellular and small animal imaging. In this work, we demonstrate that non-linearity of up-conversion allows achieving high lateral resolution in the images using multiphoton microscopy, demonstrating significant improvement in lateral resolution, using low pumping laser power. This new technique may serve as another approach for high-resolution optical imaging

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Aimon, Sophie. "Study of a voltage-gated potassium channel in giant unilamellar vesicles". Paris 6, 2011. http://www.theses.fr/2011PA066196.

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Il est difficile d'étudier in vivo le rôle de la membrane dans l'excitabilité des cellules car les paramètres pertinents (composition et état mécanique de la membrane, densité de canaux. . . ) sont activement régulés par la cellule elle-même et donc difficilement ajustables expérimentalement. J’ai donc développé une méthode pour reconstituer un canal voltage-dépendant dans une membrane où ces paramètres peuvent être contrôlés. Pour cela j’ai exprimé, purifié et marqué KvAP, un canal potassique voltage-dépendant. J’ai ensuite adapté une méthode existante pour le reconstituer dans des Vésicules Unilamellaires Géantes (GUVs). J’ai mesuré la densité des canaux dans les GUVs grâce à la microscopie confocale. Des expériences d’électrophysiologie ont, de plus, montré que le canal reste fonctionnel après reconstitution. Ce système m’a permis d’étudier tout d’abord l’affinité du canal pour les membranes courbées. Pour cela, j’ai tiré des nanotubes de rayon contrôlé à partir de ces GUVs et j’ai mesuré la distribution du canal entre la vésicule et le tube par microscopie confocale. J’ai montré que le canal est enrichi dans le tube proportionnellement à sa courbure. Ce résultat est en accord avec une théorie basée sur l’élasticité de la membrane. Nous avons également étudié l’effet du confinement de la membrane sur la diffusion de KvAP. Par des expériences de suivi de particule unique, nous avons montré que le coefficient de diffusion le long du tube diminue d’un facteur 3 lorsque le rayon du tube décroît de 250 à 10 nm. Ce résultat est en accord avec le modèle hydrodynamique de Saffman et Delbrück appliqué à la géométrie cylindrique

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Schultz, Patrick. "Etudes structurales du minichromosome du virus sv40 et de la chromatine cellulaire : approches en microscopie electronique". Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13082.

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Cayron, Julien. "Caractérisation de la réponse cellulaire associée à différents stress chez la bactérie Escherichia coli". Thesis, Lyon, 2019. https://n2t.net/ark:/47881/m6qv3kv7.

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La prolifération bactérienne requiert la coordination entre les grands processus du cycle cellulaire qui sont la réplication et la ségrégation de l’ADN, l’élongation et la division cellulaire. Durant leur vie, les bactéries sont exposées à différents stress endogènes ou exogènes (antibiotiques, pH, manque de nutriments…) qui peuvent perturber le cycle cellulaire. Ces conditions défavorables activent alors une réponse cellulaire qui vise à améliorer la survie aux stress. Chez E. coli, la formation de cassures sur le chromosome induit la réponse SOS qui inhibe la division des cellules. Dans ce contexte, la bactérie continue à s’allonger ce qui aboutit à la formation d’une cellule filamenteuse. La filamentation a longtemps été considérée comme un symptôme de mort cellulaire, mais des études récentes suggèrent qu’il s’agirait plutôt d’un changement de morphologie transitoire qui améliorerait la survie en conditions défavorables. L’objectif principal de cette thèse est de caractériser le processus de filamentation et surtout le redémarrage de la division du filament, permettant un retour à une croissance normale de la bactérie. J’ai pour cela mis en place une approche combinant la microscopie en cellules vivantes en chambre microfluidique, la cytométrie en flux, la microbiologie traditionnelle et la génétique bactérienne. L’association de ces techniques constitue une approche globale permettant de caractériser l’effet d’un stress sur la viabilité, la morphologie et le contenu en ADN des bactéries, et ce de la cellule unique à l’échelle de la population. Cette approche a permis de décrire comment les cellules filamenteuses se divisent rapidement en cellules viables et de comprendre comment cet état de différenciation cellulaire transitoire et réversible constitue une stratégie efficace de survie aux stress. Par ailleurs, l’expertise développée au cours de ces travaux m’a permis d’être impliqué dans l ‘étude du transfert de gène de résistance à la tétracycline par conjugaison bactérienne. Ces mêmes expertisent ont aussi permis la caractérisation de l’effet de biocides induisant la réponse aux stress de l’enveloppe et la visualisation de l’effet de la production chez E. coli de deux toxines prédites pour être impliquées dans un système d’inhibition de croissance contact-dépendant chez A. baumannii
Bacterial growth requires coordination between the main cell cycle processes that are DNA replication and segregation, elongation and cell division. During their life, bacteria are exposed to different endogenous or exogenous stresses (antibiotics, pH, nutrients starvation…) that can disturb the bacteria cell cycle. Those hostile life conditions trigger a cellular response aiming at improving survival in stress conditions. In E. coli, DNA breaks induce the SOS response that inhibits cell division while the bacteria continue to elongate, resulting in the formation of a filamentous cell. Filamentation has long been considered as a symptom of cell death, however recent studies suggest that this phenotype could instead be a transient morphology change improving the survival in hostile environments. The main objective of this thesis is to characterize the filamentation process, especially the restart of the filament division allowing to resume normal bacterial growth. To do so, I developped an approach combining live-cell microscopy in microfluidic chamber, flow cytometry, traditional microbiology technics and bacterial genetics. Association of those techniques constitutes a global approach allowing characterization of the stress effect on bacterial viability, morphology and DNA content, from the single cell to the population level. This experimental framework allowed to describe how filamentous cells quickly divide into viable cells, thus understanding how this transient and reversible cellular differentiation state constitute an efficient stress-survival strategy. Furthermore, the expertise I developed during this ph.D. project allowed me to be involved into the study of drug-resistance acquisition by gene transfer through bacterial DNA conjugation. Besides, I contributed to the characterization of the effects of biocides inducing envelop stress response and to the characterize the impact on E. coli of the production of Acinetobacter baumannii toxins predicted to be involved in contact-dependant growth inhibition

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Becker, Martine. "Une structure de membrane en microscopie électronique dans les leucémies aiguës de l'adulte". Bordeaux 2, 1988. http://www.theses.fr/1988BOR23016.

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Libri sul tema "Microscopie cellulaire"

1961-, Duijn Bert van, e Wiltink Anneke 1961-, a cura di. Signal transduction--single cell techniques. Berlin: Springer, 1998.

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Richard, McIntosh J., a cura di. Cellular electron microscopy. Amsterdam: Elsevier/Academic Press, 2007.

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Cheville, Norman F. Ultrastructural pathology: An introduction to interpretation. Ames: Iowa State University Press, 1994.

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Ammasi, Periasamy, a cura di. Methods in cellular imaging. Oxford: Published for the American Physiological Society by Oxford University Press, 2001.

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László, Módis. Organization of the extracellular matrix: A polarization microscopic approach. Boca Raton, Fla: CRC Press, 1991.

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L, Shorte Spencer, e Frischknecht Friedrich, a cura di. Imaging cellular and molecular biological functions. Berlin: Springer, 2007.

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Robert, Jacques. Signalisation cellulaire et cancer: Un manuel pour les étudiants et les oncologues. Paris: Springer-Verlag Paris, 2010.

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L, Shorte Spencer, e Frischknecht Friedrich, a cura di. Imaging cellular and molecular biological functions. Berlin: Springer, 2007.

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Culling, C. F. A. Cellular pathology technique. 4^a ed. London: Butterworths, 1985.

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T, Allison R., Barr W. T e Culling C. F. A, a cura di. Cellular pathology technique. 4^a ed. London: Butterworths, 1985.

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Capitoli di libri sul tema "Microscopie cellulaire"

Cinquin, Bertrand, Joyce Y. Kao e Mark L. Siegal. "i.2.i. with the (Fruit) Fly: Quantifying Position Effect Variegation in Drosophila Melanogaster". In Bioimage Data Analysis Workflows ‒ Advanced Components and Methods, 147–74. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-76394-7_7.

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AbstractMany of the methods developed for the analysis of bioimages focus on microscopy images on the cellular level. However, bioimages can also be used by biologists to assess non-cellular level morphological phenotypes. Collecting non-cellular images and developing image workflows for them is similar to working with microscopic images, but also has its unique challenges.

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de Chastellier, Chantal. "Electron Microscopy". In Cellular Microbiology, 451–71. Washington, DC, USA: ASM Press, 2014. http://dx.doi.org/10.1128/9781555817633.ch19.

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Loseva, Elizaveta, Jaap van Krugten, Aniruddha Mitra e Erwin J. G. Peterman. "Single-Molecule Fluorescence Microscopy in Sensory Cilia of Living Caenorhabditis elegans". In Single Molecule Analysis, 133–50. New York, NY: Springer US, 2023. http://dx.doi.org/10.1007/978-1-0716-3377-9_7.

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AbstractIntracellular transport of organelles and biomolecules is vital for several cellular processes. Single-molecule fluorescence microscopy can illuminate molecular aspects of the dynamics of individual biomolecules that remain unresolved in ensemble experiments. For example, studying single-molecule trajectories of moving biomolecules can reveal motility properties such as velocity, diffusivity, location and duration of pauses, etc. We use single-molecule imaging to study the dynamics of microtubule-based motor proteins and their cargo in the primary cilia of living C. elegans. To this end, we employ standard fluorescent proteins, an epi-illuminated, widefield fluorescence microscope, and primarily open-source software. This chapter describes the setup we use, the preparation of samples, a protocol for single-molecule imaging in primary cilia of C. elegans, and data analysis.

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Spring, Kenneth R. "Detectors for Fluorescence Microscopy". In Methods in Cellular Imaging, 40–52. New York, NY: Springer New York, 2001. http://dx.doi.org/10.1007/978-1-4614-7513-2_3.

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Axelrod, Daniel. "Total Internal Reflection Fluorescence Microscopy". In Methods in Cellular Imaging, 362–80. New York, NY: Springer New York, 2001. http://dx.doi.org/10.1007/978-1-4614-7513-2_21.

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Weimar, Jörg R. "Coupling Microscopic and Macroscopic Cellular Automata". In Cellular Automata: Research Towards Industry, 38–41. London: Springer London, 1998. http://dx.doi.org/10.1007/978-1-4471-1281-5_4.

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Gladstein, Scott, Andrew Stawarz, Luay M. Almassalha, Lusik Cherkezyan, John E. Chandler, Xiang Zhou, Hariharan Subramanian e Vadim Backman. "Measuring Nanoscale Chromatin Heterogeneity with Partial Wave Spectroscopic Microscopy". In Cellular Heterogeneity, 337–60. New York, NY: Springer New York, 2018. http://dx.doi.org/10.1007/978-1-4939-7680-5_19.

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Cheng, Li, Ning Ye, Weimiao Yu e Andre Cheah. "Discriminative Segmentation of Microscopic Cellular Images". In Lecture Notes in Computer Science, 637–44. Berlin, Heidelberg: Springer Berlin Heidelberg, 2011. http://dx.doi.org/10.1007/978-3-642-23623-5_80.

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Zaborina, Olga, John Alverdy, Megha Shah e Yimei Chen. "Microscopic Analysis: Morphotypes and Cellular Appendages". In Methods in Molecular Biology, 99–107. New York, NY: Springer New York, 2014. http://dx.doi.org/10.1007/978-1-4939-0473-0_11.

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So, Peter T. C., Ki H. Kim, Christof Buehler, Barry R. Masters, Lily Hsu e Chen-Yuan Dong. "Basic Principles of Multiphoton Excitation Microscopy". In Methods in Cellular Imaging, 147–61. New York, NY: Springer New York, 2001. http://dx.doi.org/10.1007/978-1-4614-7513-2_9.

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Atti di convegni sul tema "Microscopie cellulaire"

Huang, Han-Xiong, Xiao-Hui Sun e Jian-Kang Wang. "Effect of Nano-Particles on Cellular Structure of Foamed PP-HDPE Blend Using Supercritical Fluid". In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-43906.

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Microcellular foaming of general polypropylene (PP) is a hot subject, but there are some difficulties in its foaming due to its low melt strength, narrow foaming temperature window, and so on. This work attempted to the improvement of PP microcellular foaming by adding nano-montmorillonite and nano-calcium carbonate into PP-high-density polyethylene (HDPE) blend. The nanocomposites were prepared using a twin-screw extruder. The foaming was carried out by a batch process with supercritical carbon dioxide as a blowing agent. Microstructure of the nanocomposites was examined using transmission electron microscopy. The cellular structure of foams was examined using a scanning electron microscope. The effects of nano-particle concentration and type on the cellular structure, cell density, cell diameter, and sample density were investigated. The results showed that the main factor controlling the cellular structure of foamed nanocomposites is the distribution of nano-particles.

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Agard, David A., Yashushi Hiraoka e John W. Sedat. "Three-dimensional Optical Microscopy of Biological Specimens". In Signal Recovery and Synthesis. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/srs.1986.thd1.

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The ability to analyze biological specimens in three dimensions represents one of the major achievements of modern structural biology. For all but the simplest repeating structures, three-dimensional analysis is a crucial prerequisite for understanding complex biological assemblies. Near atomic resolution analysis of of crystalline proteins, nucleic acids, and viruses by X-ray crystallography approaches the routine. The current frontier focuses on the three dimensional analysis of non-crystalline, non-symmetric biological structures of cellular dimension. Electron microscope tomography and three dimensional optical microscopy are perhaps the most powerful methods for these studies.

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Nessaee, Ameer, Kivanc Kose, Elena F. Brachtel e Dongkyun Kang. "Deep Neural Network-Based Classification of Spectrally Encoded Confocal Microscopy Images of Breast Cancer Tissue". In Microscopy Histopathology and Analytics. Washington, D.C.: Optica Publishing Group, 2024. http://dx.doi.org/10.1364/microscopy.2024.mm3a.6.

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Spectrally Encoded Confocal Microscopy (SECM) previously demonstrated the ability to visualize cellular features of malignant breast tissues. In this paper, we developed a deep neural network-based method for automatically classifying SECM breast images.

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Tu, Haohua. "Supercontinuum Intrinsic Fluorescence Imaging (SCIFI) Empowers Biomarker Discovery". In Microscopy Histopathology and Analytics. Washington, D.C.: Optica Publishing Group, 2024. http://dx.doi.org/10.1364/microscopy.2024.mm5a.3.

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In contrast to other forms of fluorescence microscopy, SCIFI maximizes the information content beyond fluorescence intensity while minimizing the harm to fragile living systems, resulting in abundant label-free cellular/molecular biomarkers in biology and medicine.

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Sugimura, Momoka, Kenneth Marcelino, Rafael Romero, Jingwei Zhao, Kyungjo Kim, Ameer Nessaee, Yongjun Kim et al. "Speckle Noise Reduction in Portable Confocal Microscopy for in vivo Human Skin Imaging". In Microscopy Histopathology and Analytics. Washington, D.C.: Optica Publishing Group, 2024. http://dx.doi.org/10.1364/microscopy.2024.mm1a.6.

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Portable Confocal Microscopy (PCM) is a low-cost reflectance confocal microscopy designed for in vivo imaging of skin at cellular resolution. We developed a Speckle-Modulating PCM (SM-PCM) which reduces speckle noise while achieving high-speed imaging.

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Boppart, Stephen A., Gary J. Tearney, Brett E. Bouma, James G. Fujimoto e Mark E. Brezinski. "Optical Coherence Tomography of Embryonic Morphology During Cellular Differentiation". In Advances in Optical Imaging and Photon Migration. Washington, D.C.: Optica Publishing Group, 1996. http://dx.doi.org/10.1364/aoipm.1996.cit231.

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Improved imaging of morphological changes has the potential of offering new insight into the complex process of embryonic development. Optical coherence tomography (OCT), is a new imaging technique for performing in vivo cross-sectional imaging of architectural morphology by measuring backscattered infrared light. This study investigates the application of OCT for imaging developing structure in Xenopus laevis (African frog) and Brachydanio rerio (zebra fish), two developmental biology animal models. Images are compared to corresponding histological preparations. Cross sectional imaging can be performed and structural morphology identified at greater imaging depths than possible with confocal and light microscopy. Repeated OCT imaging may be performed in vivo in order to track structural changes throughout development. Imaging in vivo microscopic embryonic morphology with OCT is a fundamental biological research application for the study of genetic disease.

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Azartash, Kaveh, e Enrico Gratton. "Measuring the Cell-Induced Deformation of Collagen Matrix Detected With Digital Holographic Microscopy". In ASME 2007 2nd Frontiers in Biomedical Devices Conference. ASMEDC, 2007. http://dx.doi.org/10.1115/biomed2007-38064.

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A modified Mach-Zender set-up in reflection is applied to record and reconstruct holographic amplitude and phase images. A charged couple device (CCD) is used to record a hologram and numerical reconstruction algorithms are then applied to rebuild the hologram for obtaining both phase and amplitude information. One could also focus on multiple focal planes from a single hologram, similar to the focusing control of a conventional microscope. The morphology and behavior of mammalian cells is determined by an interaction between signals from the intracellular matrix and the cellular responses. It is important to note that the physical aspect of the extracellular matrix is as significant as the chemical nature of it. Specifically the stresses, mechanical forces, and the profile of the external environment have major effects on cell behavior. The mechanical and physical characteristics of a tissue are greatly dependent on a hierarchical spatial arrangement of its extra-cellular matrix components. A key player in the ECM is collagen which exhibits significant tensile strength on the cellular scale. Digital holographic microscopy (DHM) is applied to study the deformation of collage matrix in response to cell migration.

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Aguirre, Paulina. "Image processing of microscopic cellular samples". In MELECON 2012 - 2012 16th IEEE Mediterranean Electrotechnical Conference. IEEE, 2012. http://dx.doi.org/10.1109/melcon.2012.6196450.

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Kachouie, Nezamoddin N., e Paul Fieguth. "Background estimation for microscopic cellular images". In 2008 15th IEEE International Conference on Image Processing. IEEE, 2008. http://dx.doi.org/10.1109/icip.2008.4712436.

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Dong, Chen-Yuan, Hayden Huang, Jason D. B. Sutin, Hyuk-Sang Kwon, George E. Cragg, R. Gilbert, Richard T. Lee et al. "Magnetic tweezers microscope for cellular manipulation". In BiOS 2000 The International Symposium on Biomedical Optics, a cura di Daniel L. Farkas e Robert C. Leif. SPIE, 2000. http://dx.doi.org/10.1117/12.384210.

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Rapporti di organizzazioni sul tema "Microscopie cellulaire"

Sadot, Einat, Christopher Staiger e Zvi Kam Weizmann. functional genomic screen for new plant cytoskeletal proteins and the determination of their role in actin mediated functions and guard cells regulation. United States Department of Agriculture, gennaio 2003. http://dx.doi.org/10.32747/2003.7587725.bard.

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The original objectives of the approved proposal were: 1. To construct a YFP fused Arabidopsis cDNA library in a mammalian expression vector. 2. To infect the library into a host fibroblast cell line and to screen for new cytoskeletal associated proteins using an automated microscope. 3. Isolate the new genes. 4. Characterize their role in plants. The project was approved as a feasibility study to allow proof of concept that would entail building the YFP library and picking up a couple of positive clones using the fluorescent screen. We report here on the construction of the YFP library, the development of the automatic microscope, the establishment of the screen and the isolation of positive clones that are plant cDNAs encoding cytoskeleton associated proteins. The rational underling a screen of plant library in fibroblasts is based on the high conservation of the cytoskeleton building blocks, actin and tubulin, between the two kingdoms (80-90% homology at the level of amino acids sequence). In addition, several publications demonstrated the recognition of mammalian cytoskeleton by plant cytoskeletal binding proteins and vice versa. The major achievements described here are: 1. The development of an automated microscope equipped with fast laser auto-focusing for high magnification and a software controlling 6 dimensions; X, Y position, auto focus, time, color, and the distribution and density of the fields acquired. This system is essential for the high throughput screen. 2. The construction of an extremely competent YFP library efficiently cloned (tens of thousands of clones collected, no empty vectors detected) with all inserts oriented 5't03'. These parameters render it well representative of the whole transcriptome and efficient in "in-frame" fusion to YFP. 3. The strategy developed for the screen allowing the isolation of individual positive cDNA clones following three rounds of microscopic scans. The major conclusion accomplished from the work described here is that the concept of using mammalian host cells for fishing new plant cytoskeletal proteins is feasible and that screening system developed is complete for addressing one of the major bottlenecks of the plant cytoskeleton field: the need for high throughput identification of functionally active cytoskeletal proteins. The new identified plant cytoskeletal proteins isolated in the pilot screen and additional new proteins which will be isolated in a comprehensive screen will shed light on cytoskeletal mediated processes playing a major role in cellular activities such as cell division, morphogenesis, and functioning such as chloroplast positioning, pollen tube and root hair elongation and the movement of guard cells. Therefore, in the long run the screen described here has clear agricultural implications.

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Loo, Jr., Billy W., W. Meyer-Ilse e S. S. Rothman. Mechanism of cellular secretion studied by high resolution soft-x-ray microscopy. Office of Scientific and Technical Information (OSTI), aprile 1997. http://dx.doi.org/10.2172/603457.

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Yang, Haw, e Preston Snee. Final Scientific/Technical Report for Time-Resolved 3D Multi-Resolution Microscopy for Real-Time Cellulase Actions in Situ. Office of Scientific and Technical Information (OSTI), settembre 2022. http://dx.doi.org/10.2172/1887802.

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Stead, A. D., T. W. Ford, A. M. Page, J. T. Brown e W. Meyer-Ilse. X-ray dense cellular inclusions in the cells of the green alga Chlamydomonas reinhardtii as seen by soft-x-ray microscopy. Office of Scientific and Technical Information (OSTI), aprile 1997. http://dx.doi.org/10.2172/603459.

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WANG, MIN, Sheng Chen, Changqing Zhong, Tao Zhang, Yongxing Xu, Hongyuan Guo, Xiaoying Wang, Shuai Zhang, Yan Chen e Lianyong Li. Diagnosis using artificial intelligence based on the endocytoscopic observation of the gastrointestinal tumours: a systematic review and meta-analysis. InPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, febbraio 2023. http://dx.doi.org/10.37766/inplasy2023.2.0096.

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Review question / Objective: With the development of endoscopic techniques, several diagnostic endoscopy methods are available for the diagnosis of malignant lesions, including magnified pigmented endoscopy and narrow band imaging (NBI).The main goal of endoscopy is to achieve the real-time diagnostic evaluation of the tissue, allowing an accurate assessment comparable to histopathological diagnosis based on structural and cellular heterogeneity to significantly improve the diagnostic rate for cancerous tissues. Endocytoscopy (ECS) is based on ultrahigh magnification endoscopy and has been applied to endoscopy to achieve microscopic observation of gastrointestinal (GI) cells through tissue staining, thus allowing the differentiation of cancerous and noncancerous tissues in real time.To date, ECS observation has been applied to the diagnosis of oesophageal, gastric and colorectal tumours and has shown high sensitivity and specificity.Despite the highly accurate diagnostic capability of this method, the interpretation of the results is highly dependent on the operator's skill level, and it is difficult to train all endoscopists to master all methods quickly. Artificial intelligence (AI)-assisted diagnostic systems have been widely recognized for their high sensitivity and specificity in the diagnosis of GI tumours under general endoscopy. Few studies have explored on ECS for endoscopic tumour identification, and even fewer have explored ECS-based AI in the endoscopic identification of GI tumours, all of which have reached different conclusions. Therefore, we aimed to investigate the value of ECS-based AI in detecting GI tumour to provide evidence for its clinical application.

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Ehrlich, Marcelo, John S. Parker e Terence S. Dermody. Development of a Plasmid-Based Reverse Genetics System for the Bluetongue and Epizootic Hemorrhagic Disease Viruses to Allow a Comparative Characterization of the Function of the NS3 Viroporin in Viral Egress. United States Department of Agriculture, settembre 2013. http://dx.doi.org/10.32747/2013.7699840.bard.

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Project Title: "Development of a plasmid-based reverse genetics system for the Bluetongue and Epizootic Hemorrhagic Disease viruses to allow comparative characterization of the function of the NS3 viroporin in viral egress". Project details: No - IS-4192-09; Participants – Ehrlich M. (Tel Aviv University), Parker J.S. (Cornell University), DermodyT.S. (Vanderbilt University); Period - 2009-2013. Orbiviruses are insect-borne infectious agents of ruminants that cause diseases with considerable economical impact in Israel and the United States. The recent outbreaks of BTV in Europe and of Epizootic Hemorrhagic Disease Virus (EHDV) in Israel, underscore the need for: (i) a better comprehension of the infection process of orbiviruses, (ii) the identification of unique vs. common traits among different orbiviruses, (iii) the development of novel diagnosis and treatment techniques and approaches; all aimed at the achievement of more effective control and treatment measures. It is the context of these broad goals that the present project was carried out. To fulfill our long-term goal of identifying specific viral determinants of virulence, growth, and transmission of the orbiviruses, we proposed to: (i) develop reverse genetics systems for BTV and EHDV2-Ibaraki; and (ii) identify the molecular determinants of the NS3 nonstructural protein related to viroporin/viral egress activities. The first objective was pursued with a two-pronged approach: (i) development of a plasmid-based reverse genetics system for BTV-17, and (ii) development of an "in-vitro" transcription-based reverse genetics system for EHDV2-Ibaraki. Both approaches encountered technical problems that hampered their achievement. However, dissection of the possible causes of the failure to achieve viral spread of EHDV2-Ibaraki, following the transfection of in-vitro transcribed genomic segments of the virus, revealed a novel characteristic of EHDV2-Ibaraki infection: an uncharacteristically low fold increase in titer upon infection of different cell models. To address the function and regulation of NS3 we employed the following approaches: (i) development (together with Anima Cell Metrology) of a novel technique (based on the transfection of fluorescently-labeledtRNAs) that allows for the detection of the levels of synthesis of individual viral proteins (i.e. NS3) in single cells; (ii) development of a siRNA-mediated knockdown approach for the reduction in levels of expression of NS3 in EHDV2-Ibaraki infected cells; (iii) biochemical and microscopy-based analysis of the localization, levels and post-translational modifications of NS3 in infected cells. In addition, we identified the altered regulation and spatial compartmentalization of protein synthesis in cells infected with EHDV2-Ibaraki or the mammalian reovirus. In EHDV2-Ibaraki-infected cells such altered regulation in protein synthesis occurs in the context of a cell stress reponse that includes the induction of apoptosis, autophagy and activation of the stressrelated kinase c-Jun N-terminal Kinase (JNK). Interestingly, inhibition of such stress-related cellular processes diminishes the production of infectious virions, suggesting that EHDV usurps these responses for the benefit of efficient infection. Taken together, while the present project fell short of the generation of novel reverse genetics systems for orbiviruses, the development of novel experimental approaches and techniques, and their employment in the analysis of EHDV-infected cells, yielded novel insights in the interactions of orbiviruses with mammalian cells.

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Droby, Samir, Michael Wisniewski, Ron Porat e Dumitru Macarisin. Role of Reactive Oxygen Species (ROS) in Tritrophic Interactions in Postharvest Biocontrol Systems. United States Department of Agriculture, dicembre 2012. http://dx.doi.org/10.32747/2012.7594390.bard.

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To elucidate the role of ROS in the tri-trophic interactions in postharvest biocontrol systems a detailed molecular and biochemical investigation was undertaken. The application of the yeast biocontrol agent Metschnikowia fructicola, microarray analysis was performed on grapefruit surface wounds using an Affymetrix Citrus GeneChip. the data indicated that 1007 putative unigenes showed significant expression changes following wounding and yeast application relative to wounded controls. The expression of the genes encoding Respiratory burst oxidase (Rbo), mitogen-activated protein kinase (MAPK) and mitogen-activated protein kinase kinase (MAPKK), G-proteins, chitinase (CHI), phenylalanine ammonia-lyase (PAL), chalcone synthase (CHS) and 4-coumarate-CoA ligase (4CL). In contrast, three genes, peroxidase (POD), superoxide dismutase (SOD) and catalase (CAT), were down-regulated in grapefruit peel tissue treated with yeast cells. The yeast antagonists, Metschnikowia fructicola (strain 277) and Candida oleophila (strain 182) generate relatively high levels of super oxide anion (O2−) following its interaction with wounded fruit surface. Using laser scanning confocal microscopy we observed that the application of M. fructicola and C. oleophila into citrus and apple fruit wounds correlated with an increase in H2O2 accumulation in host tissue. The present data, together with our earlier discovery of the importance of H₂O₂ production in the defense response of citrus flavedo to postharvest pathogens, indicate that the yeast-induced oxidative response in fruit exocarp may be associated with the ability of specific yeast species to serve as biocontrol agents for the management of postharvest diseases. Effect of ROS on yeast cells was also studied. Pretreatment of the yeast, Candida oleophila, with 5 mM H₂O₂ for 30 min (sublethal) increased yeast tolerance to subsequent lethal levels of oxidative stress (50 mM H₂O₂), high temperature (40 °C), and low pH (pH 4). Suppression subtractive hybridization analysis was used to identify genes expressed in yeast in response to sublethal oxidative stress. Transcript levels were confirmed using semi quantitative reverse transcription-PCR. Seven antioxidant genes were up regulated. Pretreatment of the yeast antagonist Candida oleophila with glycine betaine (GB) increases oxidative stress tolerance in the microenvironment of apple wounds. ROS production is greater when yeast antagonists used as biocontrol agents are applied in the wounds. Compared to untreated control yeast cells, GB-treated cells recovered from the oxidative stress environment of apple wounds exhibited less accumulation of ROS and lower levels of oxidative damage to cellular proteins and lipids. Additionally, GB-treated yeast exhibited greater biocontrol activity against Penicillium expansum and Botrytis cinerea, and faster growth in wounds of apple fruits compared to untreated yeast. The expression of major antioxidant genes, including peroxisomal catalase, peroxiredoxin TSA1, and glutathione peroxidase was elevated in the yeast by GB treatment. A mild heat shock (HS) pretreatment (30 min at 40 1C) improved the tolerance of M. fructicola to subsequent high temperature (45 1C, 20–30 min) and oxidative stress (0.4 mol-¹) hydrogen peroxide, 20–60 min). HS-treated yeast cells showed less accumulation of reactive oxygen species (ROS) than non-treated cells in response to both stresses. Additionally, HS-treated yeast exhibited significantly greater (P≥0.0001) biocontrol activity against Penicillium expansum and a significantly faster (Po0.0001) growth rate in wounds of apple fruits stored at 25 1C compared with the performance of untreated yeast cells. Transcription of a trehalose-6-phosphate synthase gene (TPS1) was up regulated in response to HS and trehalose content also increased.

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Epel, Bernard L., Roger N. Beachy, A. Katz, G. Kotlinzky, M. Erlanger, A. Yahalom, M. Erlanger e J. Szecsi. Isolation and Characterization of Plasmodesmata Components by Association with Tobacco Mosaic Virus Movement Proteins Fused with the Green Fluorescent Protein from Aequorea victoria. United States Department of Agriculture, settembre 1999. http://dx.doi.org/10.32747/1999.7573996.bard.

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The coordination and regulation of growth and development in multicellular organisms is dependent, in part, on the controlled short and long-distance transport of signaling molecule: In plants, symplastic communication is provided by trans-wall co-axial membranous tunnels termed plasmodesmata (Pd). Plant viruses spread cell-to-cell by altering Pd. This movement scenario necessitates a targeting mechanism that delivers the virus to a Pd and a transport mechanism to move the virion or viral nucleic acid through the Pd channel. The identity of host proteins with which MP interacts, the mechanism of the targeting of the MP to the Pd and biochemical information on how Pd are alter are questions which have been dealt with during this BARD project. The research objectives of the two labs were to continue their biochemical, cellular and molecular studies of Pd composition and function by employing infectious modified clones of TMV in which MP is fused with GFP. We examined Pd composition, and studied the intra- and intercellular targeting mechanism of MP during the infection cycle. Most of the goals we set for ourselves were met. The Israeli PI and collaborators (Oparka et al., 1999) demonstrated that Pd permeability is under developmental control, that Pd in sink tissues indiscriminately traffic proteins of sizes of up to 50 kDa and that during the sink to source transition there is a substantial decrease in Pd permeability. It was shown that companion cells in source phloem tissue export proteins which traffic in phloem and which unload in sink tissue and move cell to cell. The TAU group employing MP:GFP as a fluorescence probe for optimized the procedure for Pd isolation. At least two proteins kinases found to be associated with Pd isolated from source leaves of N. benthamiana, one being a calcium dependent protein kinase. A number of proteins were microsequenced and identified. Polyclonal antibodies were generated against proteins in a purified Pd fraction. A T-7 phage display library was created and used to "biopan" for Pd genes using these antibodies. Selected isolates are being sequenced. The TAU group also examined whether the subcellular targeting of MP:GFP was dependent on processes that occurred only in the presence of the virus or whether targeting was a property indigenous to MP. Mutant non-functional movement proteins were also employed to study partial reactions. Subcellular targeting and movement were shown to be properties indigenous to MP and that these processes do not require other viral elements. The data also suggest post-translational modification of MP is required before the MP can move cell to cell. The USA group monitored the development of the infection and local movement of TMV in N. benthamiana, using viral constructs expressing GFP either fused to the MP of TMV or expressing GFP as a free protein. The fusion protein and/or the free GFP were expressed from either the movement protein subgenomic promoter or from the subgenomic promoter of the coat protein. Observations supported the hypothesis that expression from the cp sgp is regulated differently than expression from the mp sgp (Szecsi et al., 1999). Using immunocytochemistry and electron microscopy, it was determined that paired wall-appressed bodies behind the leading edge of the fluorescent ring induced by TMV-(mp)-MP:GFP contain MP:GFP and the viral replicase. These data suggest that viral spread may be a consequence of the replication process. Observation point out that expression of proteins from the mp sgp is temporary regulated, and degradation of the proteins occurs rapidly or more slowly, depending on protein stability. It is suggested that the MP contains an external degradation signal that contributes to rapid degradation of the protein even if expressed from the constitutive cp sgp. Experiments conducted to determine whether the degradation of GFP and MP:GFP was regulated at the protein or RNA level, indicated that regulation was at the protein level. RNA accumulation in infected protoplast was not always in correlation with protein accumulation, indicating that other mechanisms together with RNA production determine the final intensity and stability of the fluorescent proteins.

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