Tesis sobre el tema "Ascidian"
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Guignard, Léo. "Analyse quantitative de la morphogenèse animale : de l'imagerie laser haut-débit à l'embryon virtuel chez les ascidies". Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS048/document.
Texto completoAscidian embryos develop with stereotyped and evolutionarily conserved invariant cell lineages to produce in a few hours or days tadpole larvae with a small number of cells. They thus provide an attractive framework to describe with cellular resolution the developmental program of a whole organism. During my PhD, I developed a quantitative approach to describe the evolution of embryonic morphologies during the development of the ascidian Phallusia mammillata. I then used this approach to systematically characterize in detail the logic of cell fate induction events. To quantitatively characterize cell behaviors during embryogenesis, we used multi-angle light-sheet microscopy to image with high spatio-temporal resolution entire live embryos with fluorescently labeled plasma membranes. To extract biological information from this imaging dataset, I then developed a conceptually novel automated method for 4D cell segmentation, ASTEC. Applied to a Phallusia mammillata embryo imaged for 6 hours between the 64-cell and the initial tailbud stages, this method allows the accurate tracking and shape analysis of 1030 cells across 640 cell divisions. The resulting 4D digital embryo can be formalized as a dynamic graph, in which cells are represented by nodes, linked within a time point by edges that represent their spatial neighborhood, and between time points by temporal edges describing cell lineages.Based on this quantitative digital representation, we systematically identified cell fate specification events up to the late gastrula stage. Computational simulations revealed that remarkably simple rules integrating measured cell-cell contact areas with boolean spatio-temporal expression data for extracellular signalling molecules are sufficient to explain most early cell inductions. This work suggests that in embryos establishing precise stereotyped contacts between neighboring cells, the genomic constraints for precise gene expression levels are relaxed, thereby allowing rapid genome evolution
Evans, Rowan. "Reproduction of the unitary, larviparous ascidian Dendroda grossularia". Thesis, University of Liverpool, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260360.
Texto completoMadgwick, Alicia. "Evolution des programmes transcriptionnels développementaux des ascidies Ciona robusta et Phallusia mammillata". Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT137/document.
Texto completoHow can embryonic morphogenesis be evolutionarily conserved in spite of extensive divergence in coding and non-coding genome sequences? To address this question, we worked on the early development of two very divergent ascidians, Phallusia mammillata and Ciona intestinalis. These species share an almost identical early morphogenesis and stereotyped cell lineages. Remarkably, however, their genomes are divergent to the extent that their non-coding sequences cannot be aligned and gene order has not been conserved.We focus our attention on the behaviour of endoderm precursors throughout two important evolutionarily conserved developmental processes: initial fate specification and early gastrulation. We first compared by in situ hybridisation the transcriptional expression of orthologous regulatory genes in Phallusia and in Ciona. We found that the endodermal expression of 8 regulatory genes known to be involved in these developmental processes is qualitatively conserved between the two species.To study how these genes conserved their regulation in spite of extensive non-coding sequence divergence, we collaborated with the Gomez-Skarmeta lab to map, by ATAC-seq, open chromatin regions in both species to identify active regulatory regions genomewide. Three quarters of the 39 open chromatin regions for endodermal genes behaved as active regulatory sequences by the larval stage, when tested by electroporation in embryos. Many of the tested sequences had conserved cis-regulatory activity in both species in spite of sequence divergence. We have identifed putative transcription factor binding sites in endodermal enhancers in both species to identify conserved upstream regulators shared between Phallusia and Ciona.Taken together our results suggest that extensive transcription factor binding site turn over, without radical change in GRNs architecture, may explain the qualitative conservation of gene expression patterns between highly divergent ascidian genomes. Furthermore, we found that shadow enhancers are much more prevalent than initially anticipated.Taken together our results suggest that extensive transcription factor binding site turn over, without radical change in GRNs architecture, may explain the qualitative conservation of gene expression patterns between highly divergent ascidian genomes. Furthermore, we found that shadow enhancers are much more prevalent than initially anticipated
西川, 輝昭, Teruaki Nishikawa, D. D. Bishop John y Dorothea Sommerfeldt A. "Occurrence of the alien ascidian Perophora japonica at Plymouth". Cambridge University Press, 2000. http://hdl.handle.net/2237/10552.
Texto completoJohnson, Sheri L. "Mating System Dynamics in a Free-Spawning Colonial Ascidian". Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/JohnsonSL2007.pdf.
Texto completoBevis, Peter John. "Studies on gastrointestinal peptides in the ascidian Styela clava". Thesis, Royal Holloway, University of London, 1985. http://repository.royalholloway.ac.uk/items/2ce39101-08bf-48be-be30-1042d191f253/1/.
Texto completoPeddie, Clare M. "Lymphocyte-like functions in the solitary ascidian Ciona intestinalis". Thesis, University of St Andrews, 1995. http://hdl.handle.net/10023/13994.
Texto completoKhandelwal, Mudrika. "Structure and processing of fibrous cellulose : bacterial and ascidian material". Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/244716.
Texto completoCleto, Cynthia. "Analysis of transcriptional elements of an ascidian troponin I gene". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33733.
Texto completoPemberton, A. J. "Aspects of mate choice in the colonial ascidian Diplosoma listerianum". Thesis, University of Aberdeen, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.593279.
Texto completoCasso, Carrasco Maria. "Genomic analysis of an introduced ascidian and implications for invasiveness". Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/673998.
Texto completoYu, Deli. "Temporal control of muscle gene expression in an ascidian embryo". Kyoto University, 2019. http://hdl.handle.net/2433/242897.
Texto completoStoner, Douglas Steven. "Life History and Populationi Biology of the Colonial Ascidian Diplosoma Similis". Thesis, University of Hawaii, Honolulu, 1989. http://hdl.handle.net/10125/18144.
Texto completoTypescript. Thesis (Ph. D.)--University of Hawaii at Manoa, 1989. Includes bibliographical references.
Mortimer, Sandra 1981. "Experimental analysis of trans-splicing of an ascidian troponin I gene". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101643.
Texto completoDavis, Martin Herbert. "Physical factors influencing larval behaviour in three species of solitary ascidian". Thesis, Open University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388307.
Texto completoMilne, Bruce Forbes. "Theoretical studies of cyclic octapeptides from the marine ascidian Lissoclinum patella". Thesis, University of Aberdeen, 2002. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU168052.
Texto completoHaupaix, Nicolas. "Régulation de la voie MEK/ERK par la signalisation éphrine lors du développement neural chez l'ascidie Ciona intestinalis". Phd thesis, Université Nice Sophia Antipolis, 2014. http://tel.archives-ouvertes.fr/tel-01059798.
Texto completoCallahan, Ashley G. "Harbour survey and genetic analysis of non-indigenous ascidian tunicates in Newfoundland /". Internet access available to MUN users only. Search for this title in:, 2009.
Buscar texto completoGreen, Kathryn Margaret. "Morphological changes during normal and pertubed metamorphosis of the ascidian herdmania curvata /". St. Lucia, Qld, 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16468.pdf.
Texto completoChowdhury, Rafath. "Formation du système nerveux périphérique ventral chez l'ascidie et l'amphioxus : aperçu de son origine au sein des chordés". Electronic Thesis or Diss., Sorbonne université, 2021. http://www.theses.fr/2021SORUS405.
Texto completoVertebrates develop their peripheral nervous system from unique dorsal structures, the neural crest and the ectodermal placodes. By contrast, in the invertebrate chordates, amphioxus and ascidians, a part of the PNS originates from a ventral neurogenic field. In both groups, a biphasic mechanism regulates ventral PNS formation: high BMP levels specify the ventral ectoderm as a neurogenic territory within which epidermal sensory neurons formation is controlled by the Notch pathway. Thus, it is likely that ventral PNS is an ancestral feature in chordates and that it has been lost in vertebrates or redeployed dorsally to form the neural crest and placodes. In order to test this hypothesis, my project aims at studying the origin and evolution of the vPNS in invertebrate chordates. To this end, a comparative analysis of the ascidian Phallusia mammillata and the amphioxus Branchiostoma lanceolatum was performed. Transcriptomic analyses allowed me to identify novel vPNS markers in both species and to propose two hypothetical gene regulatory networks. Despite low conservation in invertebrate chordates, similarities were observed with vertebrate PNS, suggesting that ancestral vPNS gene networks have been redeployed in vertebrates. Then, in order to validate these networks, I set up a new injection method and established gene inactivation using the CRISPR/Cas9 system in B. lanceolatum. Finally, transcriptomic data mining led me to study the formation of the ascidian palps. Functional studies revealed essential roles for BMP and Wnt signalling pathways in the formation of the palps and suggest similarities with the formation of the anterior telencephalon of vertebrates
Davis, Rohan Andrew y davis_rohan@hotmail com. "Chemical Investigations of Great Barrier Reef Ascidians - Natural Product and Synthetic Studies". Griffith University. School of Science, 2000. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030102.104858.
Texto completoKhare, Parul. "CIS-regulatory elements driving muscle-specific expression of an ascidian troponin I gene". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84044.
Texto completoLiu, Boqi. "The gene regulatory network in the anterior neural plate border of ascidian embryos". Kyoto University, 2020. http://hdl.handle.net/2433/253119.
Texto completoCorbo, Joseph C. "Molecular aspects of notochord and nervous system development in the ascidian, Ciona intestinalis /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9735267.
Texto completoVirata, Michael J. "A novel invertebrate chordate model for Alzheimer's disease using the ascidian ciona intestinalis". Diss., [La Jolla, Calif.] : [San Diego] University of California, San Diego ; San Diego State University, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3372801.
Texto completoTitle from first page of PDF file (viewed October 22, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
Yagi, Kasumi. "Studies on function of Zic family transcription factor genes in early ascidian embryos". 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147859.
Texto completoPrünster, Maria Mandela. "De novo myogenesis and neurogenesis during budding of the colonial ascidian, Botryllus schlosseri". Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS586.
Texto completoThe aim of this work is to describe via molecular-biological methods the asexual form of development of the colonial ascidian Botryllus schlosseri focusing on the formation of different tissues, namely muscles and nervous system, as well as exploring the potential presence of structures or cells homologous to the neural crest. Ascidians belong to the subphylum tunicates, sister group of vertebrates and are the closest relatives to man that can reproduce asexually, by budding. As colonial ascidian, the metamorphosis of Botryllus schlosseri specimen is followed by a lifelong, recurring, highly coordinated budding process, where multiple individuals (zooids) are connected and embedded in a common tunic. During asexual development, zooids can develop in a direct manner without embryonic and larval stages. To study the cellular origin and mechanisms of non-embryonic myogenesis I followed the expression pattern and dynamics of myogenic genes during asexual development and reconstructed muscle precursors. Orthologs of these genes are not only expressed during muscle formation via larval development but also during the formation of cardio-pharyngeal muscles in the vertebrate embryogenesis. I further drew a comparison of the regionalization of a transitory neurogenic structure, the dorsal tube, along the anteroposterior axis during budding with its larval counterpart, the neural tube, thus adding a RNA-expression profile of neural genes hereby proposing a scenario of cerebral ganglion formation by delamination. To better understand the nature of the dorsal tube and gangliogenesis I investigated potential involvement gene orthologs implemented in vertebrate neural crest formation
Michelin, Gaël. "Outils d'analyse d'images et recalage d'individus pour l'étude de la morphogenèse animale et végétale". Thesis, Université Côte d'Azur (ComUE), 2016. http://www.theses.fr/2016AZUR4088/document.
Texto completoIn developmental biology, the study of model organisms aims for theunderstanding of genetic mechanisms responsible of morphogenesis. Today,fluorescent confocal microscopy is a means for in vivo imaging of developingorganisms at cell level with a high spatio-temporal resolution. To handle such3D+t image sequences, adapted computer-assisted methods are highlydesirable.In this thesis, we build dedicated tools for the study of two developingorganisms, the ascidian Phallusia mammillata's embryo and the Arabidopsisthaliana's floral meristem.We first develop a method for segmentation comparison adapted to developingorganism epithelial tissue images. This tool is then used to validate our secondcontribution that is about the development of a cell membranes detection andreconstruction tool for cell shape segmentation process applied to ascidian andarabidopsis images.We then use the previously introduced membrane detection tool to build aninter-individual spatial registration strategy applied to ascidian embryo images.Finally, we develop an inter-individual spatio-temporal registration strategyapplied to 3D image sequences of arabidopsis floral meristems
Carroll, Michael. "Generation and propagation of sperm induced Ca²⺠waves in the ascidian oocyte". Thesis, University of Newcastle Upon Tyne, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246669.
Texto completoArmsworthy, Shelley L. "Effects of suspended bottom sediment on the feeding activity of the ascidian, Halocynthia pyriformis (Rathke)". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq23775.pdf.
Texto completoArmsworthy, Shelley L. "Effects of suspended bottom sediment on the feeding activity of the ascidian, Halocynthia pyriformis (Rathke)". Thesis, University of New Brunswick, 1996. http://hdl.handle.net/1882/495.
Texto completoSwallow, Michael Andrew Carleton University Dissertation Biology. "Determination and differentiation of muscle cells in the tadpole larva of the Ascidian Boltenia Villosa". Ottawa, 1992.
Buscar texto completoRosfelter, Anne. "Le positionnement du fuseau mitotique chez le zygote d'ascidie et son rôle dans la répartition des organelles". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS063.
Texto completoAfter oocyte fertilization, a microtubule aster forms around the male DNA. The sperm aster brings the female pro-nucleus to the male pro-nucleus so they can fuse, but it also moves the fused nuclei to the cell center to ensure an equitable cell division. Numerous studies performed in vitro, by modeling or experimentally in species such as C. elegans, P. lividus, and M. musculus, addressed the aster and spindle centration mechanisms. Three main mechanisms emerged; pushing, cortical pulling, and cytoplasmic pulling. By studying aster centration in the zygote of the ascidian P. mammillata, I discovered a system that combines these three mechanisms based on the cell cycle stages. In meiosis, the aster uses the polymerization of its microtubules to push against the actin cortex and move away from it (pushing). Once in interphase, the aster returns to the cortex by a pull exerted by the membrane on the microtubules (cortical pulling). At mitosis entry, cortical pulling stops, and releases the mitotic spindle's asters. In consequence, the asters give in to the forces exerted by the transport of organelles to the aster center (cytoplasmic pulling), that appeared constant during the cell cycle. Cytoplasmic pulling hence participate in centering the spindle While the aster forms and moves, the intracellular compartments reorganize. To understand how intracellular organization can be disrupted by aster formation, I studied the case of yolk. The yolk, in the form of vesicles (called granules or platelets), is initially abundant and homogeneous in the unfertilized oocyte. However, as soon as the aster appears, its distribution changes and the yolk platelets are excluded from the region containing the aster. This exclusion generated by the aster formation in the zygote is maintained during development. I observed that yolk exclusion is mainly due to the accumulation at the aster of other organelles such as the endoplasmic reticulum. The transport function of the aster microtubules is therefore sufficient to completely reorganize the cell by excluding some organelles and accumulating others. The movements of the aster and the spindle, their regulation by cell cycle, and the intracellular reorganization, identified here in the ascidian zygote, rely on basic elements of a cell, namely: the microtubules, the actin cortex, the endoplasmic reticulum, the proteins of the cell cycle, etc. Thus, the discoveries presented here cover a broad scope, and seem adaptable to the specificities of different cell types
Scelzo, Marta. "Vasal budding : characterization of a new form of non-embryonic development in the colonial ascidian Polyandrocarpa zorritensis". Electronic Thesis or Diss., Sorbonne université, 2020. http://www.theses.fr/2020SORUS467.
Texto completoColonial tunicates can generate a new adult body by asexual reproduction and whole body regeneration, two forms of non-embryonic development (NED). Different modes of NED are defined depending on the nature of the organogenetic tissues. Interestingly, this capacity is scattered across the sub-phylum, with species able of NED (colonial) closely related to species where regenerative capabilities are absent or reduced (solitary). This suggests that NED has been acquired or lost several times among the group. In recent phylogeny of family Styelidae, the colonial species Polyandrocarpa zorritensis seems to have acquired independently the capability of NED. During my PhD, I characterized the NED in this species, identifying the stages of NED under laboratory conditions and the tissues/cells involved. By histological and ultrastructural analyses, I highlighted the participation to NED of vascular epithelium and mesenchymal cells. This type of NED was undescribed before, and we decided to call it “vasal budding”. During the early stages of vasal budding I observed undifferentiated mesenchymal cells cluster and proliferate at the regenerative point; their distribution varies during vasal budding, increasing in the developing areas. I described the mesenchymal cells, identifying in the proliferating cells an undifferentiated morphotype, the hemoblasts, known as putative stem cells in other colonial ascidian. In addition, I defined the presence of a dormant stage, the spherule, in the life cycle of P. zorritensis and I characterized the environmental variable and the molecular mechanisms involved in dormancy in this species and in a distantly related species, Clavelina lepadiformis
Haupaix, Nicolas. "Régulation de la voie MEK/ERK par la signalisation éphrine lors du développement neural chez l'ascidie Ciona intestinalis". Electronic Thesis or Diss., Nice, 2014. http://theses.unice.fr/2014NICE4003.
Texto completoDuring my thesis study, I was involved in functional studies to demonstrate that p120-RasGAP, a GTPase-activating-protein (GAP), is a cytoplasmic mediator of the ephrin-mediated ERK attenuation. To confirm this notion, I conducted a co-immunoprecipitation experiment and demonstrated that p120-RasGAP associates with an ephrin receptor, Eph3, when the latter is activated by an ephrin ligand in ascidian embryos. These results strongly indicate that FGF and ephrin signals converge at the level of Ras and control its activity antagonistically. Following this finding, I looked for other cell fate specification events controlled by the antagonism between ephrin and FGF signals. In ascidian embryos, FGF signals are known to induce neural fates in ectodermal cells which otherwise adopt epidermal fates. Ascidian neural induction takes place at the 32-cell stage, resulting in specification of specific four cells as ERK1/2-active neural precursors among 16 ectodermal cells. I was able to demonstrate that ephrin/Eph/RasGAP signals counterbalance FGF neural inducing signals to generate the ON-OFF response of ERK activation among the ectodermal cells. Finally, in collaboration with a PhD student in Dr. Mike Levine’s lab (UC Berkeley), the antagonism between ephrin and FGF signals plays a role in regionalisation of the neural plate along the anterior-posterior axis
Stanley, MacIsaac Sarah. "Ultrastructure of the visceral ganglion in the ascidian larva Ciona intestinalis, cell circuitry and synaptic distribution". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0017/MQ57329.pdf.
Texto completoSato, Kaoru. "Isolation and characterization of β-catenin downstream genes in early embryos of the ascidian Ciona savignyi". 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/149114.
Texto completoDegasperi, Valentina. "Nervous system differentiation in the colonial ascidian Botryllus schlosseri: molecular and cellular aspects and evolutive implications". Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3426922.
Texto completoNegli ultimi anni numerosi studi si sono rivolti all’approfondimento di quei meccanismi che hanno permesso la comparsa ed evoluzione di strutture ritenute di estrema importanza nella radiazione dei vertebrati. La comparsa dei vertebrati è stata accompagnata da un enorme balzo nella complessità del piano strutturale degli organismi, largamente ascrivibile all’evoluzione di strutture associate al sistema nervoso come le creste neurali, i placodi craniali ed un cervello elaborato. La tematica trattata durante lo svolgimento del progetto di dottorato si inserisce in questa attuale linea di ricerca. In particolare, l’attenzione è stata rivolta a quei caratteri che nei cordati non-vertebrati possono essere letti come cruciali per la successiva evoluzione del piano strutturale dei vertebrati. Il punto di partenza è rappresentato da precedenti studi morfologici che hanno evidenziato la presenza, nell’embrione dei tunicati, di territori ectodermici transitori e multipotenti localizzati al confine con la piastra neurale. Il nostro studio, svolto mediante l'utilizzo di vari approcci metodologici, si è rivolto alla caratterizzazione e descrizione delle strutture che queste aree sono in grado di differenziare. A questo proposito, è stata analizzata l’organizzazione delle papille larvali e la loro formazione a partire dal placode rostrale. Queste strutture giocano un ruolo primario nell’innescare i meccanismi e i cambiamenti che caratterizzano la metamorfosi, ovvero quel processo che nelle ascidie segna la perdita del piano corporeo da cordato della larva e il passaggio alla fase post-embrionale sessile. L’analisi riguardante strutture sensoriali presenti nelle ascidie, allo scopo di identificare eventuali omologie con le corrispondenti strutture derivanti dai placodi nei vertebrati, è stata poi estesa all’organo coronale. L’organo coronale è stato scoperto solo recentemente e presenta caratteristiche morfologiche generali, posizionali e ultrastrutturali tali, come la presenza di cellule capellute, che lo rendono comparabile alla linea laterale ed all’orecchio interno dei vertebrati, i cui componenti derivano dai placodi acustico-laterali. Una parte consistente del lavoro è stata dedicata all’indagine, da un punto di vista molecolare, della presenza di strutture accomunabile ai placodi neurali nelle ascidie. L’attenzione è stata rivolta all’ascidia coloniale Botryllus schlosseri, che permette di svolgere uno studio comparativo sui meccanismi e reti geniche che intervengono sia durante lo sviluppo embriogenetico che blastogenetico. Abbiamo caratterizzato specifici geni e prodotto sonde utilizzate in esperimenti di ibridazione in situ. Durante le fasi di differenziamento della gemma sono stati individuati specifici territori caratterizzati da espressione di alcuni geni normalmente coinvolti nell’induzione e specificazione placodale nei vertebrati. Grazie alla loro posizione e potenzialità differenziativa, queste stesse regioni sono apparse confrontabili con altri territori embrionali di B. schlosseri e di altre ascidie considerati omologhi a placodi neurali dei vertebrati. La larva delle ascidie presenta una muscolatura simmetrica striata, con caratteri comuni a quella dei vertebrati, la quale fiancheggia il tubo dorsale e la notocorda e che rappresenta una proprietà peculiare dei cordati. L’acquisizione di questo nuovo sistema locomotorio ha verosimilmente richiesto la comparsa parallela di un sofisticato sistema di controllo della coordinazione. Il sistema nervoso ha stabilito nuove interazioni e differenziato strutture sensoriali che hanno permesso all’organismo mobile la rapida percezione dell’ambiente circostante. Alla metamorfosi, la muscolatura larvale viene completamente riassorbita, mentre le fibre muscolari non striate della parete del corpo e quelle cardiache si differenziano de novo da cellule mesenchimali circolanti. Questa plasticità sta alla base della potenzialità evolutiva delle ascidie e quindi ne abbiamo indagato le basi molecolari e morfologiche. Abbiamo quindi isolato e caratterizzato trascritti e geni muscolo-specifici, studiandone l’espressione durante il ciclo blastogenetico di Botryllus, dalla comparsa della gemma alla regressione dell’adulto. L ’utilizzo di vari approcci ha permesso la descrizione dell’organizzazione e differenziamento della muscolatura non striata, confermandone le caratteristiche uniche. Nel complesso i diversi risultati rappresentano contributi significativi per la conoscenza delle origini e sviluppo quelle strutture che hanno rappresentato un punto di partenza importante nell’evoluzione e radiazione dei vertebrati.
Williaume, Géraldine. "Graded signal inputs to binary cell fate decisions : a quantitative approach based on ascidian neural induction". Electronic Thesis or Diss., Sorbonne université, 2020. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2020SORUS426.pdf.
Texto completoTo address how a cell interprets a graded signal to generate a threshold response, I studied the initial step of ascidian neural induction. During this process, four ectoderm cells among sixteen are selected as neural precursors. FGF9/16/20, derived from mesendoderm cells, acts as a neural inducer and activates Otx expression through the ERK pathway. Quantitative measurement of cell surface contacts (CSC) between ectoderm cells and FGF-expressing cells has revealed that each ectoderm cell is exposed to FGF, with neural precursors having the largest area of CSC with FGF-expressing cells. Using quantitative measurements of endogenous ERK activation and Otx expression, we have revealed that each ectoderm cell exhibits a level of ERK activation corresponding to its area of CSC with FGF-expressing mesendoderm cells while Otx expression is restricted to only the four neural precursors. An ephrin ligand is expressed in the ectoderm cells and act antagonistically to FGF signals. In embryos inhibited for ephrin/Eph signals, ERK levels are increased in all ectoderm cells, proportionally to their CSC with the FGF-expressing cells. Under these conditions, the spatial precision of Otx expression is lost with additional ectoderm cells exhibiting Otx expression suggesting that ephrin/Eph signals act to reduce the overall levels of ERK activation, such that the non-neural ectoderm cells remain below the threshold required for Otx activation. We tested this hypothesis by treating embryos, in which ephrin signals were blocked, with low doses of the MEK inhibitor U0126. This treatment was sufficient to re-establish the normal Otx expression profile in the four neural precursors
Cole, Alison G. "Cell-lineage of the larval CNS in the ascidian Ciona intestinalis, neurula stage through to hatched larva". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0021/MQ57277.pdf.
Texto completoYeats, Brendan. "Spliced leader (SL) «trans»-splicing in the ascidian tunicate «Ciona intestinalis»: molecular characterization of the SL RNA". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=67011.
Texto completoAu d'épart, j'ai entrepris d'identifier la structure coiffe de l'ARN spliced leader de Ciona intestinalis. Durant cette recherche, j'ai découvert un nouveau transcript d'RN de 53 nt qui contient la séquence spliced leader. Ce transcrit contient la coiffe usuele des ARNs spliced leader des métazoaires, le trimethylguanosine, tandis que l'ARN spliced leader canonique ne possède pas cette modification, mais contient, fort probablement, une coiffe mP7PG. La structure de la coiffe de l'ARNm de la troponine I trans-épissé correspond à celle de l'ARN spliced leader canonique, indiquant que l'ARN spliced leader est le donneur pour la troponine I, et non l'ARN de 53 nt. Des études d'immunoprécipitation supplémentaires ont montré que l'ARN spliced leader canonique et le nouvel ARN de 53 nt existent en association avec des protéines Sm.J'ai cloné une sequence d'ADN génomique contenant quatre repetitions en tandem du gène l'ARN spliced leader. Ce clone a été utilisé comme sonde lors d'une experience d'hybridation in situ qui a montré que la grande majorité des gènes l'ARN spliced leader réside sur le chromosome 8.Finalement, j'ai effectué une étude préliminaire montrant que les outrons, les segments 5' des ARNs pré-messagers enlevés par le trans-épissage, existent en quantité suffisante et peuvent être détecté par l'amplification PCR.
Häussler, Maximilian. "Prediction of tissue-specific cis-regulatory sequences : application to the ascidian Ciona intestinalis and the anterior neurectoderm". Paris 11, 2009. http://www.theses.fr/2009PA112078.
Texto completoIn this thesis, a procedure is presented to rank combinations of short sequence motifs by their distribution around a set of genes. The better a combination matches around genes expressed in a certain tissue, the higher is its score. I applied this to an already characterized enhancer of C. Intestinalis expressed in the anterior neurectoderm which had been found by systematic mutations to be composed of a duplicated structure. The results of my procedure indicated that duplicated GA TTA-sites are an essential feature of cis-regulatory elements active in the anterior neurectoderm. Searching the genome for matches to this signature resulted in putative enhancers that drive a reporter gene in 50% of the cases in the anterior neurectoderm. In addition, I tried to improve the curation of already published cis-regulatory elements by extracting them automatically from the full text of the biological research articles. Thanks to the thriving open access publishing model and the improvement in experimental assays, more and more of this data is becoming available. Finally, I showed that in the absence of non-coding sequence alignments between the genomes of vertebrate and C. Intestinalis, one can nevertheless find a handful of loci with a very unusually conserved gene order. In these cases, the cis-regulatory search space is reduced to a set of introns, some of which were recently shown to harbor enhancers. Many of these loci have not been analyzed yet. Together, these computational approaches should lead to a better characterization of cis-regulatory sequences and pave the way for further experimental validations
Suwandy, Jason. "Temporal Currency: Life-history strategies of a native marine invertebrate increasingly exposed to urbanisation and invasion". Thesis, University of Canterbury. School of Biological Sciences, 2012. http://hdl.handle.net/10092/7322.
Texto completoPyriohou, Anastasis. "Regeneration of the neural complex in the ascidian Ciona intestinalis with particular reference to the role of hemocytes". Thesis, Royal Holloway, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298362.
Texto completoMorris, Linda Anne. "Studies on the Cu(II) and Zn(II) binding properties of cyclic peptides from the ascidian Lissoclinum patella". Thesis, University of Aberdeen, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300904.
Texto completoMontenegro, Tasso Gabriel Coelho. "Chemoenzymatic synthesis of chloramphenicol and thiamphenicol derivatives and bioguided chemical study of fungi associated with ascidian eudistoma vannamei". Universidade Federal do CearÃ, 2011. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7062.
Texto completoEste trabalho descreve: 1) sÃntese quimioenzimÃtica de Ãsteres do cloranfenicol (1) e tianfenicol (2), utilizando lipases como fonte biocatalÃtica; 2) avaliaÃÃo do potencial atitumoral de fungos marinhos isolados da ascÃdia Eudistoma vannamei. Na primeira parte, realizou-se a sÃntese enzimÃtica de dois derivados monoacilados do cloranfenicol (1), atravÃs de reaÃÃes de hidrÃlise de derivados diacilados, e oito derivados monoacilados do tianfenicol (2), pela acilaÃÃo e hidrÃlise enzimÃtica do tianfenicol e derivados diacilados, respectivamente. Os seguintes parÃmetros foram variados: enzima, solvente, temperatura, pH e proporÃÃo entre solvente e agente hidrolÃtico e, na hidrÃlise enzimÃtica dos derivados de cloranfenicol diacilados, os melhores resultados foram com a mistura de CH3CN:tampÃo fosfato (pH 7) na proporÃÃo de 20:80, CAL-B como biocatalisador, temperatura de 20 ÂC, agitaÃÃo de 250 rpm e tempo reacional de 24 h. A reaÃÃo de acilaÃÃo enzimÃtica do tianfenicol (2), utilizando CAL-B como biocatalisador e Ãsteres vinÃlicos como doadores de grupos acila, se mostrou bastante eficiente, com altos Ãndices de conversÃo e seletividade. Os processos forneceram unicamente os produtos de acilaÃÃo da hidroxila menos impedida (3â-OH). A eficiÃncia da enzima CAL-B reciclada na reaÃÃo de acilaÃÃo do tianfenicol (2) foi investigada, sendo possÃvel concluir que esta se mantÃm ativa durante os cinco processos reacionais testados. A hidrÃlise enzimÃtica dos derivados diacilados do tianfenicol forneceu, majoritariamente, os produtos de hidrÃlise na posiÃÃo 3. Na segunda parte do trabalho, foram isoladas 11 cepas fÃngicas (EV1 a EV11) da ascÃdia E. vannamei, as quais foram cultivadas em meio lÃquido BD (batata-dextrose) com objetivo de realizar um estudo bioguiado atravÃs da avaliaÃÃo da atividade citotÃxica de seus extratos e fraÃÃes. Foram ensaiados os extratos acetoetÃlico do meio lÃquido e metanÃlico do micÃlio, previamente separados. Os extratos mais ativos foram os oriundos de EV10 e EV11, os quais foram identificados como Aspergillus sp. por anÃlise molecular. O fungo EV10 foi cultivado em grande escala para fracionamento bioguiado e isolamento dos metabÃlitos secundÃrios bioativos. Foi possÃvel isolar quatro micotoxinas: meleÃna, cis-4-hidroximeleÃna, trans-4-hidroximeleÃna e Ãcido penicÃlico, dentre as quais, somente o Ãcido penicÃlico foi identificado como responsÃvel pela atividade do extrato.
This work describes: 1) chemoenzymatic synthesis of chloramphenicol (1) and thiamphenicol (2) esters, using lipases as biocatalyst source; 2) investigation of the antitumor potential of fungi isolated from the marine ascidian Eudistoma vannamei. In the first part, it was carried out the enzymatic synthesis of two monoacyl derivatives of chloramphenicol (1), through the hydrolysis of the diacyl derivatives, and eight monoacyl derivatives of thiamphenicol (2), by the enzymatic acylation and hydrolysis of thiamphenicol and diacyl derivatives, respectively. The following p arameters were varied: enzyme, solvent, temperature, pH and proportion between solvent and agent hydrolytic, and in enzymatic hydrolysis of the diacyl derivatives of chloramphenicol, the best results were reached when using a mixture of CH3CN: phosphate buffer (pH 7) in the proportion 20:80, CAL-B as biocatalyst, temperature of 20 Â C, 250 rpm and reaction time of 24 h. The enzymatic acylation of thiamphenicol (2), using CAL-B as biocatalyst and vinyl esters as acyl donor groups, was very efficient, with high conversion and selectivity. The processes provided only products of the ac ylation of the less hindered hydroxyl group (3'-OH). The efficiency of the recycled CAL-B in the acylation of thiamphenicol (2) was investigated, being possible to conclude that its activity was maintained during the five tested reactions. Enzymatic hydrolysis of diacylated derivatives of thiamphenicol, provided mostly the hydrolysis products in position 3. In the second part of this work, we isolated 11 fungal strains (EV1 to EV11) associated to the ascidian E. vannamei, which were cultivated in liquid BD (potato dextrose) in order to conduct a bioguided study by evaluating the cytotoxic activity of their extracts and fractions. The ethylacetate extracts of the liquid medium and methanol extracts from the mycelium, previously separate, were assayed and the most active extracts were those from EV10 and EV11, which were identified as Aspergillus sp. by molecular analysis. EV10 was grown on a larger scale allowing the bioguided fractionation and isolation of bioactive secondary metabolites. It was possible to isolate four mycotoxins: mellein, cis-4-hydroxymellein, trans-4-hydroxymellein and penicillic acid, among which only the later compound was identified as responsible for the activity of the extract.
Davis, Rohan. "Chemical Investigations of Great Barrier Reef Ascidians - Natural Product and Synthetic Studies". Thesis, Griffith University, 2000. http://hdl.handle.net/10072/366561.
Texto completoThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Science
Full Text
Ricci, Lorenzo. "A new model to study alternative developments : asexual propagation and regeneration in the basal chordate Botryllus schlosseri". Electronic Thesis or Diss., Paris 6, 2015. http://www.theses.fr/2015PA066683.
Texto completoIn addition to embryogenesis, the colonial ascidians Botryllus schlosseri evolved two alternative developmental pathways leading to the same final structure: the adult body, or zooid. These non-embryonic ontogenesis occur during distinct biological processes: palleal budding (PB) and vascular budding (VB). PB is a process of asexual propagation, with a very stereotyped morphogenesis. Conversely, VB is a purely regenerative phenomenon, induced in the vascular system of the colony by the ablation of all zooids and palleal buds. My research work followed the objective to characterize the molecular and cellular basis of both PB and VB in B. schlosseri. The study of meso-, endo- and ectodermal lineage marker genes revealed the existence of presumptive territories of these lineages in the early palleal and vascular buds and that a single developmental program was launched in both VB and PB. Neural and muscle fates were studied in more detail for PB, indicating a potential double function, both neuro- and myo-genic for the dorsal tube, a structure so far associated with the nervous system only. A detailed morphological description of VB allowed to identify stereotyped stages during early regeneration. Eventually, a transcriptomic characterization of early VB and PB processes initiated an unbiased study of the molecular basis underlying the budding phenomenon in Botryllus. The overall goal of these research works is to unravel the molecular and genetic basis that facilitated, in Botryllus and globally in metazoan, the evolution of alternative developmental pathways
Manenti, R. "DEVELOPMENT OF THE LARVAL PERIPHERAL NERVOUS SYSTEM IN THE ASCIDIAN CIONA INTESTINALIS: ROLE OF THE RETINOIC ACID AND FGF/WNT SIGNALLING PATHWAYS AND OF THE POU TRANSCRIPTION FACTORS". Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/150061.
Texto completoRicci, Lorenzo. "A new model to study alternative developments : asexual propagation and regeneration in the basal chordate Botryllus schlosseri". Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066683.
Texto completoIn addition to embryogenesis, the colonial ascidians Botryllus schlosseri evolved two alternative developmental pathways leading to the same final structure: the adult body, or zooid. These non-embryonic ontogenesis occur during distinct biological processes: palleal budding (PB) and vascular budding (VB). PB is a process of asexual propagation, with a very stereotyped morphogenesis. Conversely, VB is a purely regenerative phenomenon, induced in the vascular system of the colony by the ablation of all zooids and palleal buds. My research work followed the objective to characterize the molecular and cellular basis of both PB and VB in B. schlosseri. The study of meso-, endo- and ectodermal lineage marker genes revealed the existence of presumptive territories of these lineages in the early palleal and vascular buds and that a single developmental program was launched in both VB and PB. Neural and muscle fates were studied in more detail for PB, indicating a potential double function, both neuro- and myo-genic for the dorsal tube, a structure so far associated with the nervous system only. A detailed morphological description of VB allowed to identify stereotyped stages during early regeneration. Eventually, a transcriptomic characterization of early VB and PB processes initiated an unbiased study of the molecular basis underlying the budding phenomenon in Botryllus. The overall goal of these research works is to unravel the molecular and genetic basis that facilitated, in Botryllus and globally in metazoan, the evolution of alternative developmental pathways