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1
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.
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Les embryons d'ascidies se développent avec un lignage cellulaire stéréotypé et évolutionairement conservé pour produire en quelques heures ou jours un têtard comportant un petit nombre de cellules. De ce fait, ils fournissent un cadre intéressant pour décrire avec une résolution cellulaire le programme de développement d’un organisme complet. Pendant mon doctorat, j’ai développé une approche quantitative pour décrire l’évolution morphologique embryonnaire pendant le développement de Phallusia mammillata. J’ai ensuite utilisé cette approche pour systématiquement caractériser en détail les logiques des événements de spécifications de destin cellulaire.Pour caractériser quantitativement les comportements cellulaires pendant l’embryogenèse, nous avons utilisé de la microscopie à feuille de lumière multi-angles pour imager des embryons entiers à haute résolution spatio-temporelle. Les membranes plasmiques étaient marquées pour permettre l’identification des cellules. Pour extraire les informations biologiques de ce jeu de donnés, j’ai développé une nouvelle méthode pour segmenter les cellules en 4D, ASTEC. Une fois appliquée aux embryons de Phallusia mammillata imagés pendant 6 heures entre le stade 64 cellules et le début des stades bourgeon caudal, cette méthode a permis de récupérer la forme et de suivre 1030 cellules pendant 640 divisions. L’embryon digital 4D résultant peut être formalisé par un graphe dynamique, dans lequel les cellules sont représentées par des sommets reliés par des arrêtes représentant au sein d’un point de temps leur voisinage spatial, et entre différents points de temps leur lignage cellulaire.Basé sur cette représentation digitale et quantitative, nous avons systématiquement identifié les événements de spécification cellulaire jusqu’au dernier stade de la gastrulation. Des simulations informatiques ont révélé que des règles remarquablement simples intégrant les aires de contacts cellulaires et les expressions spatio-temporelles booléennes de signaux moléculaires extracellulaires sont suffisantes pour expliquer les inductions cellulaires au cours du développement précoce. Ce travail suggère que pour les embryons établissant des contacts stéréotypés et précis entre cellules voisines, les contraintes génomiques sont relâchées, ce qui permet une évolution plus rapide du génomeAscidian 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
2
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.
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Madgwick, Alicia. "Evolution des programmes transcriptionnels développementaux des ascidies Ciona robusta et Phallusia mammillata". Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT137/document.
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Comment la morphogenèse embryonnaire peut-elle être conservée malgré une divergence importante des séquences codantes et non-codantes ? Pour répondre à cette question, nous avons travaillé sur le développement précoce d’ascidies divergentes, Phallusia mammillata et Ciona intestinalis. Ces espèces partagent une morphogénèse pratiquement identique et des lignages cellulaires stéréotypés. Or, leurs génomes sont tellement divergents que leurs séquences ne peuvent pas être alignées.Nous avons choisi d’étudier les cellules précurseuses de l’endoderme au cours de deux processus développementaux conservés : spécification du destin et la gastrulation. Nous avons comparé par hybridation in situ l’expression transcriptionelle des gènes régulateurs orthologues dans Phallusia et Ciona. Nous avons trouvé que l’expression dans l’endoderme de 8 gènes régulateurs impliqués dans ces processus développementaux est qualitativement conservée entre les deux espèces.Pour étudier comment ces gènes ont conservé leur régulation malgré une divergence non-codante importante, nous avons collaboré avec l’équipe Gomez-Skarmeta pour cartographier, par ATAC-seq, la chromatine ouverte dans les deux espèces pour identifier les régions régulatrices actives à l’échelle du génome. 35 sur les 39 séquences ouvertes avoisinant les gènes de l’endoderme ont été trouvé active avant le stade larval, par éléctroporation. La plupart des séquences testées ont conservé leur activité dans les deux espèces malgré la divergence de séquence. Nous avons alors identifié des sites de fixations pour facteurs de transcription potentiels se trouvant dans les enhancers pour l’endoderme pour identifier les régulateurs dans Phallusia et Ciona.Nos résultats suggèrent des changements assez importants de l’ordre des sites de fixations sans pour autant avoir de changement dans l’architecture dans les réseaux de gènes régulateurs ; ceci explique la conservation qualitative de l’expression des gènes entre ces ascidies divergentes. En outre, nous avons trouvé que les shadow enhancers sont plus répandus qu’anticipéHow 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
4
西川, 輝昭, Teruaki Nishikawa, D. D. Bishop John i Dorothea Sommerfeldt A. "Occurrence of the alien ascidian Perophora japonica at Plymouth". Cambridge University Press, 2000. http://hdl.handle.net/2237/10552.
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Johnson, 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.
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Bevis, 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/.
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Cells analogous to vertebrate endocrine cells have been described in the gut epithelium of the ascidian Styela clava. As well as some histochemical similarities, ultrastructural correlations have been demonstrated, particularly the presence of electron dense granules, clustered around and mainly below the nucleus, thinning out towards the apex. Like the endocrine cells of the vertebrate gut, the cells are often pyramidal, with a narrow apex which is occasionally observed to extend to the lumen of the gut. In addition, strong secretin immunofluorescence was observed in the endocrine-like (E-L) cells of the mucous cap of the gastric ridges. Because of these observations, acid extracts of Styela gut were assayed for secretin in the rat and in the turkey. The Styela extracts as prepared were inactive but it is possible that this reflected faults in the extraction technique. Development of a perfused Styela gut preparation, however, produced evidence to support the hypothesis that a CCK-like peptide is released into the circulation, presumably from the E-L cap cells, although CCK-like immunoreactivity is not demonstrable in these cells. The observation that in addition to CCK, bombesin and physalaemin also induce enzyme release suggests that the pre-pancreatic zymogen cells contain a rich complement of receptors, corresponding to all the classes of PI stimulating receptors which have been found on vertebrate acinar cells. There is therefore the implication that these hormones or analogues may be present in Styela. As secretin was found not to act as a secretagogue in this system, the significance of its production is unclear. By analogy with vertebrate systems it may exert some control over the secretion of mucus by the cap cells.
7
Peddie, Clare M. "Lymphocyte-like functions in the solitary ascidian Ciona intestinalis". Thesis, University of St Andrews, 1995. http://hdl.handle.net/10023/13994.
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The blood cells of the solitary ascidian, Ciona intestinalis, were examined for lymphocyte-like functions with a view to clarifying the phylogenetic origin of lymphocytes in invertebrates. It was found that cells, present in the circulating blood, mediate the haemolysis of sheep red blood cells, and that a different cell type mediates cytotoxic activity against a range of mammalian tumour cell lines in vitro. The blood cells, cytotoxic to mammalian cell lines, were enriched by continuous density gradient centrifugation, and their activity was ameliorated by heat-treatment. Parameters of cytotoxic activity against the target cell line, WEHI, a mouse myelomonocytic leukemic cell (strain 3B), were ascertained by fluorochromasia and the phenomenon was found to be rapid, temperature dependent and sensitive to osmotic conditions. Cytotoxicity was also found to be dependent upon the presence of magnesium and calcium ions, effector to target cell binding, and active metabolic, cytoskeletal and secretory processes in the effector cells. The cytotoxic cells were non-adherent to glass or nylon wool and transmission electron microscope studies of the target-binding cells showed that they were undifferentiated, with a high nucleus to cytoplasm ratio, containing a few large mitochondria, some profiles of rough endoplasmic reticulum and many free ribosomes. In addition, TEM studies revealed close inter-digitation of the effector and target cell membranes and evidence of secretory activity within the effector cell, in the area of target cell binding. The effector cell population was cultured in vitro and proliferation in response to concanavalin A, phytohaemagglutinin-B, lipopolysaccharide, or allogeneic leucocytes, measured by the uptake of tritiated thymidine, showed that these cells respond to both T and B cell mitogens and exhibit a mixed leucocyte reaction. In addition, the culture of pharyngeal explants and the measurement of cytotoxic activity by cells migrating from the explants indicates that the cytotoxic cells originate in a thymus-like haemopoietic tissue. Therefore, the undifferentiated blood cells of C. intestinalis, possess functional and morphological properties consistent with phylogenetic precursors of vertebrate lymphocytes.
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Khandelwal, 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.
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Cleto, 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.
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A long-range research interest of this laboratory is the evolution of the transcriptional control mechanisms of the vertebrate troponin I (TnI) gene family. It is likely that the vertebrate TnI gene family arose from a single TnI gene present in early chordate ancestors. Analysis of transcriptional control mechanisms of the TnI gene of a primitive chordate, such as the ascidian Ciona intestinalis, may therefore provide insight into the regulatory mechanisms of the vertebrate ancestral TnI gene. As an initial step in such a study, I localized transcriptional control regions within 1.5 kb of 5'-flanking DNA of the Ciona TnI gene. I prepared a series of deletion constructs in which Ciona TnI 5'-flanking DNA segments were fused to a nuclear-targeted beta-galactosidase reporter gene. Constructs were introduced into fertilized Ciona eggs by electroporation, and following development up to the mid tailbud stage (12 h), reporter gene expression was assessed by whole-mount beta-galactosidase histochemistry. (Abstract shortened by UMI.)
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Pemberton, 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.
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The hermaphrodite, colonial ascidian Diplosoma listerianum (Chordata: Urochordata) mates by releasing sperm that disperse to neighbours, where they fertilise eggs that have been retained internally rather than spawned. The species is able to utilise highly dilute sperm: comparison with published information on a sea urchin, which released both eggs and sperm for external fertilisation, showed that D. listerianum maintained comparable levels of fertilisation at sperm concentrations two or three orders of magnitude lower than the echinoderm. Laboratory clones of D. listerianum displayed surprisingly high levels of sexual incompatibility. Fecundities of numerous pairwise crosses varied widely and suggested a continuous scale of computability. Although correlations of computability between reciprocal crosses appeared positive, considerable noise was present in the data and some crosses showed strongly asymmetrical compatibility. Patterns of sperm precedence with a five-day mating internal showed clear initial bias towards the first of two acting males. The proportion of second-male paternity (P2) subsequently increased with time. Estimated P2 for entire progeny arrays was consistently greater than 0.5, but varied widely. When mating interval was reduced, mate order effects appeared to be moderated. In competition with an alternative sperm source, acting males fathered more progeny if previously mated to a particular female than if no mating history existed, an advantage probably derived from fertilisations by stored sperm. When virgin acting female colonies were given mixtures of sperm at widely divergent concentrations, offspring were shared between the two sperm sources in approximately the ratio of each mixture. However, there existed a small but statistically significant deviation from the fair raffle model, in that sperm at the lower concentration consistently achieved a greater than expected share of paternity. Environmentally-determined fixed female preferences could be responsible for this negative frequency dependence ('rare male effect').
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Casso, Carrasco Maria. "Genomic analysis of an introduced ascidian and implications for invasiveness". Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/673998.
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Invasive species constitute a major threat to global biodiversity and cause important economic losses and ecological impacts. In the marine realm, ascidians include several aggressive invasive species, some of which have worldwide colonisation ranges, such as Didemnum vexillum. In this thesis, some biological and ecological characteristics implicated in the invasiveness of the species are assessed. First, we performed a 20 month monitoring to determine settlement and growth preferences of invasive ascidian species in the Ebro Delta aquaculture facility, including D. vexillum. Our results indicated that D. vexillum has a preference for complex substrates. To minimise fouling on bivalves, spat immersion during fall and below 1 m depth is recommended. To detect new introduced species, a follow-up program based on occurrences would be sufficient. Second, a protocol for small DNA samples combining whole genome amplification (WGA) and genotyping-by-sequencing (GBS) was developed and applied to D. vexillum using a single zooid per colony to determine patterns of genomic diversity and differentiation, describe the colonisation history of the species, and study its capability to form chimeras. Our results confirmed that Japan is in the native area of the species and only one clade spread worldwide. We found that the two main mitochondrial clades are strongly differentiated at the genomic level suggesting reproductive isolation, we determined that three independent colonisation events shaped the global distribution of the species, and we found that populations are diverse and well differentiated indicating a high expansion potential of D. vexillum. Third we detected high prevalence of chimerism, and fusion was unlinked to global genetic relatedness. Finally, we analysed the microbiome of D. vexillum that showed markedly different composition than a congeneric species and water. The invasive clade had a small but abundant core and a highly diverse variable microbiome component with a strong capacity to enrich the symbionts from the environment. The microbiome structure correlated to host genetic distance, temperature and geographical distances, pointing to vertical and horizontal transmission. In conclusion, D. vexillum is an aggressive invasive species with a high adaptive capacity that may contribute to the invasiveness of this global pest.
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Yu, Deli. "Temporal control of muscle gene expression in an ascidian embryo". Kyoto University, 2019. http://hdl.handle.net/2433/242897.
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Stoner, 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.
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This dissertation examines two issues related to the
ecological and evolutionary consequences of sexual and
asexual reproduction in colonial marine invertebrates.
The first two chapters explore the extent to which the
planktonic larval phase limits the distribution and
abundance of a colonial ascidian, Oiplosoma similis. The
third chapter examines some of the fitness consequences
of alterations in the pattern of asexual reproduction by
colony fragmention in similis. All research was
carried out on the fringing coral reef surrounding
Coconut Island which is located in Kaneohe Bay, Oahu,
Hawaii.Typescript. Thesis (Ph. D.)--University of Hawaii at Manoa, 1989. Includes bibliographical references.
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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.
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I investigated SL trans-splicing in the troponin I gene of Ciona intestinalis. Experimental mutation of the AG dinucleotide adjacent to the natural trans-splice acceptor site (-64) in CiTnI/nuclacZ constructs eliminated trans-splicing to that site in Ciona embryos but activated trans-splicing at cryptic acceptor sites at -76 and -39, adjacent to the nearest AG dinucleotides. However, not all AG dinucleotides specify cryptic acceptor sites because outron internal deletions or 3'truncation mutants were trans-spliced at a far-upstream AG-adjacent cryptic site (-346), leaving many AGs in the retained outron segments. Thus, additional sequence elements that are present only in the -346 and -76/-64/-39 regions are required for cryptic acceptor activity. All mutant constructs generated detectable beta-gal enzyme expression, although the mutant with the longest retained-outron segment appeared less active. Therefore, mRNA accumulation and translation do not require trans-splicing to the natural acceptor site, although they may be facilitated by the normal removal of the outron during trans-splicing.
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Davis, 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.
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Milne, 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.
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A comparative theoretical study of oxazole and thiazole was carried out in order to evaluate the performance of several theoretical methods that might be useful in studies on the much larger patellamides (1-8), a family of cyclic octapeptides from the marine ascidian Lissoclinum patella. Several density functional theory (DFT) methods were included in this study and it was found that whilst all the functionals tested performed well, HCTH and B3LYP gave results that were better than those obtained at the Hartree-Fock level and equal to or better that the MP2 method but at reduced computational cost. As a result of this preliminary work the B3LYP functional was chosen and the 6-31G(d,p) basis selected for use in the patellamide study. This level of theory was also chosen for studies of the Cu2+ binding site in the patellamides with the SBKJC effective core potential basis. (Fig. 3772) Equilibrium geometries and energies were obtained for a number of conformers/rotamers of ascidiacyclamide (1) and patellamides A (2), C (4) and D (5) at the B3LYP/6-31G(d,p) level and were used to help rationalise the empirical observations that substitutional asymmetry appears to be responsible for determining the conformational (folding) preferences in these peptides. The results showed that the energy change on folding (DeltaEfolding) was positive for all four peptides but that the various substitutions significantly reduced the magnitude of DEfolding compared with the C2 symmetric 1. Desymmetrisation of the oxazoline rings in 2 gives rise to changes in the b-turn forming portions of the macrocycle, leading to improved folding at these positions. Alternatively, the local structure around the two thiazole ring containing regions can be altered by substitution at R1 and R3, leading to improved closure of the macrocycle outwith the beta-turn and improved pi-stacking between these moieties and shorter hydrogen bonding distances in other areas of the macrocycle.
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Haupaix, 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.
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Durant ma thèse, j'ai participé à une étude fonctionnelle qui a démontré que p120-RasGAP, une protéine appartenant à la famille GAP (GTPase-activating protein), est le médiateur cytoplasmique de l'éphrine lors de l'atténuation d'ERK1/2. Pour confirmer cela, j'ai réalisé une expérience de co-immunoprécipitation et j'ai démontré que p120-RasGAP s'associe au récepteur de l'éphrine, Eph3, quand celui-ci est activé par un ligand éphrine. Ce résultat indique fortement que les signaux FGF et éphrine convergent au niveau de Ras et qu'ils contrôlent de manière antagoniste son activité. Dès lors, j'ai analysé les autres événements de spécification cellulaire impliquant l'antagonisme FGF/éphrine. Chez l'embryon d'ascidie, le signal FGF est décrit comme inducteur du destin neural dans les cellules ectodermiques qui, en absence du signal FGF, adoptent le destin épidermique. L'induction neurale des ascidies a lieu au stade 32 cellules et se traduit par la spécification de quatre précurseurs neuraux (ERK+) parmi les 16 cellules ectodermiques. J'ai démontré que le signal éphrine/Eph/RasGAP antagonise le signal FGF pour générer une activation d'ERK1/2 de type tout ou rien parmi les cellules ectodermiques. Enfin, en collaboration avec Philip Abitua, doctorant dans le laboratoire du Dr. Mike Levine (UC Berkeley), nous démontrons que l'antagonisme entre les signaux éphrine et FGF est impliqué dans la régionalisation antéro-postérieure de la plaque neurale
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Callahan, 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.
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Green, 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.
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Chowdhury, 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.
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Le système nerveux périphérique des vertébrés se forme à partir de structures dorsales qui leurs sont propres : la crête neurale et les placodes ectodermiques. À l’inverse, chez les invertébrés chordés, les amphioxus et les ascidies, une partie du SNP provient d’une région neurogénique ventrale. Chez les deux groupes, il a été montré qu’un fort signal BMP induit l’ectoderme ventral à devenir neurogénique au sein de laquelle la formation de neurones épidermiques sensorielles est contrôlée par la voie Notch. Ainsi, il est probable que le système nerveux périphérique ventral soit un caractère ancestral chez les chordés, qui a été perdu chez les vertébrés. Afin de tester cette hypothèse, mon projet vise à étudier l’origine et l’évolution du SNPv des invertébrés chordés. Pour cela, j’ai réalisé une analyse comparative du modèle ascidie Phallusia mammillata avec le modèle amphioxus Branchiostoma lanceolatum. Des analyses transcriptomiques m’ont permis d’identifier de nouveaux marqueurs du SNPv chez les deux espèces et de proposer deux réseaux de régulation de gènes hypothétiques. Malgré une faible conservation au sein des invertébrés chordés, plusieurs similitudes ont été observées avec le SNP des vertébrés, suggérant un recyclage de certains modules de ces réseaux au niveau du SNP dorsal des vertébrés. Ensuite, j’ai mis en place une nouvelle méthode d’injection et validé l’inactivation génique grâce au système CRISPR/Cas9 chez l’amphioxus. Enfin, je me suis intéressé à la formation des palpes des ascidies. La fonction des voies de signalisation BMP et Wnt dans la formation des palpes suggère des similarités avec la mise en place du télencéphale antérieur des vertébrésVertebrates 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
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Davis, Rohan Andrew, i 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.
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This thesis describes the chemical investigations of several ascidian species collected from the Great Barrier Reef, Queensland, Australia. The thesis is divided into two separate components, Part A focuses on the isolation and structure elucidation of 11 previously undescribed ascidian metabolites. All structures were assigned using a combination of spectroscopic and/or chemical methods. Part B relates to the isolation and chemical conversion of a natural product to a combinatorial template. The natural product template was subsequently used in the generation of a solution-phase combinatorial chemistry library. A further two combinatorial libraries were generated from a synthesised model compound that was related to the natural product template. Part A. Investigation of Aplidium longithorax collected from the Swains Reefs resulted in the isolation of two new para-substituted cyclofarnesylated quinone derived compounds, longithorones J (30) and K (31). The former compound had its absolute stereochemistry determined by the advanced Mosher method. From an Aplidium longithorax collected from Heron Island, two new cyclofarnesylated hydroquinone compounds, longithorols C (46) and D (47) and a novel macrocyclic chromenol, longithorol E (48) were isolated. Longithorol C (46) had its absolute stereochemistry determined by the advanced Mosher method. Chemical investigation of the deep-purple colonial ascidian, Didemnum chartaceum collected from Swains Reefs led to the isolation of five new lamellarin alkaloids, which included the 20-sulfated derivatives of lamellarins B (94), C (95) and L (96), the 8-sulfated derivative of lamellarin G (97) and the non-sulfated compound, lamellarin Z (98). The known lamellarins A (63), B (80), C (64), E (65), G (67), and L (71) plus the triacetate derivatives of lamellarin D (82) and N (83) were also isolated. An aberration in the integration of signals in the 1H NMR spectra of the 20-sulfated derivatives (94-96) led to NMR relaxation studies. T1 values were calculated for all protons in the sulfated lamellarins (94-97) and their corresponding non-sulfated derivatives (80, 64, 71, 67). The protons ortho to the sulfate group in compounds (94-97) had T1 values up to five times larger than the corresponding protons in their non-sulfated derivatives (80, 64, 71, 67). A specimen of Eudistoma anaematum collected from Heron Island was shown to contain a new b-carboline alkaloid, eudistomin V (130), in addition to the two known metabolites, eudistomin H (105) and I (106). Part B. The known natural products, 1,3-diphenethylurea (29), 1,3-dimethylxanthine (30), 1,3-dimethylisoguanine (31) and the salts of tambjamine C (16), E (18) and F (19) were isolated from the ascidian, Sigillina signifera collected in Blue Lagoon, Lizard Island. Base hydrolysis on mixtures of the salts of tambjamine C (16), E (18) and F (19) resulted in the production of 4-methoxy-2,2-bipyrrole-5-carbaldehyde (26). This natural product template (26) was used in the generation of an enamine combinatorial chemistry library (98, 103-111) using solution-phase parallel synthesis. The biaryl compound, 4-(2-thienyl)-1H-pyrrole-2-carbaldehyde (59) was successfully synthesised using Suzuki-Miyaura coupling conditions and subsequently used as a template in the generation of an amine (67, 77, 80-87) and imine (78, 92-95) combinatorial library using solution-phase parallel synthesis.
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Khare, 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.
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My research goal was to functionally dissect the regulatory region of the gene encoding the muscle protein troponin I (TnI) in the simple chordate Ciona intestinalis. Based on evolutionary sequence conservation and computational prediction of cis-elements in the regulatory region, I designed mutants and assayed their effects in a recombinant DNA construct reporter system. I electroporated TnI DNA-linked reporter constructs into Ciona zygotes and assayed reporter activity following 12-14 hr of development. These studies showed that a conserved E-box is essential for high-level embryonic tail muscle-specific expression whereas conserved MEF-2 and overlapping CREB/TEF-1 sites were not. I carried out functional promoter identification experiments and 5' RACE studies and localized the core-promoter/transcription start-site in the Ciona TnI gene. My results point out the similarities/differences between Ciona and vertebrate Tnl gene regulation, which presumably reflect the conservation/modification of TnI gene regulatory mechanisms during chordate/vertebrate evolution.
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Liu, Boqi. "The gene regulatory network in the anterior neural plate border of ascidian embryos". Kyoto University, 2020. http://hdl.handle.net/2433/253119.
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Corbo, 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.
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Virata, 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.
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Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2009.Title from first page of PDF file (viewed October 22, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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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.
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Prünster, 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.
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Le but de mon projet était de décrire les molécules impliquées dans le développement asexué de l'ascidie coloniale Botryllus schlosseri et d'en déduire les mécanismes associés. Les ascidies appartiennent au sous embranchement des Tuniciers, groupe frère des Vertébrés. Elles sont les organismes les plus proches de l'humain capable de se reproduire de manière asexuée par bourgeonnement. Le travail a été réalisé sur l'ascidie coloniale Botryllus qui est composée de plusieurs individus (zoïde) réunis dans une tunique commune. Lors du développement asexué de Botryllus le zoïde peut sauter les stades embryonnaires et larvaires pour directement former un nouveau corps adulte incluant toute la musculature et le système nerveux en bourgeonnant. Dans le but d'étudier l'origine cellulaire et les mécanismes sous-jacents potentiels à la myogenèse non embryonnaire, j'ai suivi l'expression de ces gènes myogéniques lors du bourgeonnement de Botryllus et j'ai reconstruit la dynamique des précurseurs des muscles. Les orthologues de ces molécules ne sont pas exprimés seulement chez les ascidies mais également lors du développement du muscle cardio-pharyngé chez les Vertébrés et l'origine commune du cœur et des muscles pharyngés dans le champ cardio-pharyngé était déjà présente chez l'ancêtre commun des Tuniciers et des Vertébrés. En étudiant l'origine cellulaire lors de la neurogenèse j'ai pu observer que des gènes larvaires qui déterminent l'axe antérieur postérieur (AP) ont été cooptés dans une structure transitoire neuronale qui donne le ganglion cérébroïde. Ils divisent la structure en trois parties, évoquant ainsi de la tripartition de système nerveux des VertébrésThe 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
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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.
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En biologie développementale, l'étude d'organismes modèles vise à comprendreles mécanismes génétiques responsables de la morphogenèse chez le vivant. Lamicroscopie confocale à fluorescence permet aujourd'hui d'observer in vivo àl'échelle de la cellule et avec une haute fréquence temporelle le développementd'organismes. Les séquences d'images 3D+t ainsi obtenues nécessitent d'avoirdes outils de traitement d'images adaptés.Dans cette thèse, nous construisons des outils dédiés à l'étude dudéveloppement de deux organismes, l'embryon de l'ascidie Phallusiamammillata et le bouton floral d'Arabidopsis thaliana.Nous développons d'abord une méthode de comparaison de segmentationsadaptée aux images de tissus épithéliaux d'organismes en développement.Nous nous appuyons sur cet outil pour valider notre seconde contribution quiporte sur la mise en place d'un outil de détection et de reconstruction demembranes cellulaires conçu afin de procéder à la segmentation de cellulesdans les images d'ascidies et d'arabidopsis.Nous utilisons ensuite l'outil de segmentation de membranes précédemmentintroduit pour construire une stratégie de recalage spatial inter-individusappliquée aux embryons d'ascidies. Enfin, nous élaborons une stratégie derecalage spatio-temporel inter-individus appliquée à des séquences d'images 3Dde méristèmes florauxIn 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
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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.
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Armsworthy, 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.
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Armsworthy, 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.
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Swallow, Michael Andrew Carleton University Dissertation Biology. "Determination and differentiation of muscle cells in the tadpole larva of the Ascidian Boltenia Villosa". Ottawa, 1992.
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Rosfelter, 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.
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Après la fécondation d’un ovocyte, un aster de microtubules se forme autour de l’ADN mâle. Cet aster spermatique permet d’amener le pro-noyau femelle jusqu’au pro-noyau mâle pour qu’ils puissent fusionner. Il permet aussi de déplacer l’ADN fusionné jusqu’au centre de la cellule pour assurer une division cellulaire équitable. Les mécanismes de centration d’un aster ou d’un fuseau ont donné lieu à de nombreuses recherches, que ce soit par modélisation, expérimentalement chez des espèces telles C. elegans, P. lividus, M.musculus ou in vitro sur des extraits de Xenopus laevis. Trois mécanismes principaux se dégagent : le pushing, le cortical pulling et le cytoplasmic pulling (ou bulk pulling). En étudiant le déplacement de l’aster et du fuseau mitotique chez le zygote de l’ascidie P. mammillata j’ai découvert un système qui combine ces trois mécanismes en s’appuyant sur l’alternance des étapes du cycle cellulaire. En méiose, l’aster utilise la polymérisation des microtubules qui le composent pour pousser contre le cortex d’actine et s’en décoller (pushing). Arrivé en interphase, l’aster retourne contre le cortex grâce à une traction qu’exerce la membrane sur les microtubules (cortical pulling). Enfin à l’entrée en mitose, la traction membranaire cesse et libère les asters du fuseau mitotique, qui cèdent donc aux forces exercées par le transport d’organelles vers le centre de l’aster (cytoplasmic pulling) qui semblent constantes durant le cycle cellulaire. Cela permet de centrer le fuseau. En même temps que l’aster se forme et se déplace, une réorganisation des compartiments intracellulaires se met en place. Pour comprendre de quelle manière l’organisation intracellulaire peut être perturbée par la formation de l’aster, j’ai étudié le cas du vitellus. En effet, le vitellus, qui est présent sous forme de vésicules, est initialement abondant et homogène dans l’ovocyte non fécondé. Cependant, dès que l’aster apparaît, sa répartition change et les vésicules de vitellus sont exclues de la zone contenant l’aster. Cette exclusion générée à la formation de l’aster chez le zygote, est maintenue au cours du développement. Dans mes travaux, j’ai pu observer qu’elle est majoritairement due à l’accumulation à l’aster d’autres organelles comme le réticulum endoplasmique. La fonction de transport des microtubules de l’aster suffit donc à réorganiser complètement la cellule en excluant certaines organelles et en en accumulant d’autres. Les déplacements de l’aster et du fuseau mitotique, leur régulation par le cycle cellulaire, et la réorganisation intracellulaire, identifiés ici chez le zygote d’ascidie, s’appuient sur le fonctionnement d’éléments fondamentaux d’une cellule, à savoir : les microtubules, le cortex d’actine, le réticulum endoplasmique, les protéines du cycle cellulaire, etc. Les découvertes présentées revêtent ainsi une portée universelle, adaptable aux spécificités de différents types cellulairesAfter 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
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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.
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Les tuniciers coloniaux peuvent générer un nouveau corps par reproduction asexuée et par la régénération entière du corps, deux formes de développement non-embryonnaire (DNE). Les différents modes de DNE sont définis en fonction de la nature des tissus organogénétiques. Curieusement, cette capacité est dispersée au sein du sous-phylum, qui contient des espèces capables de DNE (colonial) proches phylogénétiquement d’espèces ou les capacités régénératives sont absentes ou réduites (solitaire). Cela suggère que le DNE a été acquis et perdu plusieurs fois au sein du groupe. L’espèce coloniale Polyandrocarpa zorritensis semble avoir indépendamment acquis la capacité de DNE. Au cours de ma thèse, j’ai caractérisé le DNE dans cette espèce, en identifiant les étapes de DNE en conditions de laboratoire ainsi que les tissus et cellules mises en jeu. J’ai mis en évidence la participation des cellules mesenchymales et de l’épithélium vasculaire dans ce type de DNE. Ça n’a été pas décrit auparavant, et nous avons décidé de l’appeler ‘bourgeonnement vasale’. J’ai observé des cellules mesenchymales non-différenciées se regrouper et proliférer au point de régénération. J’ai décrit les cellules mesenchymales, en identifiant dans les cellules qui prolifèrent un morphotype non-différencié, les hémoblastes, aussi connues comme étant des cellules-souches putatives chez d’autres ascidies coloniales. De plus, j’ai défini la présence d’une étape de quiescence, la sphérule, dans le cycle de vie de P. zorritensis et j’ai caractérisé les variables environnementales et les mécanismes moléculaires mis en jeu dans la quiescence de cette espèce et dans une espèce éloignée, Clavelina lepadiformisColonial 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
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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.
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Durant ma thèse, j’ai participé à une étude fonctionnelle qui a démontré que p120-RasGAP, une protéine appartenant à la famille GAP (GTPase-activating protein), est le médiateur cytoplasmique de l’éphrine lors de l’atténuation d’ERK1/2. Pour confirmer cela, j’ai réalisé une expérience de co-immunoprécipitation et j’ai démontré que p120-RasGAP s’associe au récepteur de l’éphrine, Eph3, quand celui-ci est activé par un ligand éphrine. Ce résultat indique fortement que les signaux FGF et éphrine convergent au niveau de Ras et qu’ils contrôlent de manière antagoniste son activité. Dès lors, j’ai analysé les autres événements de spécification cellulaire impliquant l’antagonisme FGF/éphrine. Chez l’embryon d’ascidie, le signal FGF est décrit comme inducteur du destin neural dans les cellules ectodermiques qui, en absence du signal FGF, adoptent le destin épidermique. L’induction neurale des ascidies a lieu au stade 32 cellules et se traduit par la spécification de quatre précurseurs neuraux (ERK+) parmi les 16 cellules ectodermiques. J’ai démontré que le signal éphrine/Eph/RasGAP antagonise le signal FGF pour générer une activation d’ERK1/2 de type tout ou rien parmi les cellules ectodermiques. Enfin, en collaboration avec Philip Abitua, doctorant dans le laboratoire du Dr. Mike Levine (UC Berkeley), nous démontrons que l’antagonisme entre les signaux éphrine et FGF est impliqué dans la régionalisation antéro-postérieure de la plaque neuraleDuring 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
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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.
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Sato, 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.
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Degasperi, 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.
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In the last years, several studies are addressed to the investigation of mechanisms that permitted the appearance and evolution of those structures considered as extremely important in the vertebrates radiation. The rise of vertebrates was accompanied by the acquisition of a great complexity in the structural plan of the organisms that is related to the evolution of features associated with the nervous system, such as neural crests, cranial placodes and an elaborated brain.
The aim of the doctoral project is inserted in this line of research. Particularly, the attention is addressed to those characters, which in the non- vertebrate chordates can be interpreted as crucial for the subsequent evolution of the vertebrate body-plan. The starting point is represented by previous morphological studies that evidenced the presence, in the tunicate embryo, of transitory ectodermal and multipotential territories located at the neural plate border. Our research, carried out using different approaches, is focused on the characterisation and description of structures that differentiate from these domains. In this regard, it is investigated the organisation of the larval papillae and their formation from the rostral placode. These structures play a pivotal role in triggering the mechanisms and changes that characterise the metamorphosis, which in ascidians constitute the lost of the chordate body-plan of the larva and the begin of the sessile post-embryonic phase.
The analysis of the sensory components in ascidians, finalised to the identification of homologies with the structures that derive form the placodes in vertebrates, is also extended to the coronal organ. The coronal organ is recently discovered and possesses morphological, positional and ultrastructural features that, together with the presence of hair cells, are comparable to the lateral line and inner ear of vertebrates, which components derive from the acoustic-lateral placodes.
A substantial part of the work is dedicated to the investigation, with a molecular approach, of the presence of structures comparable to the neural placodes in ascidians. The attention is focused on the colonial ascidian Botryllus schlosseri that permits a comparative study on the mechanisms and genic networks involved in both embryogenetic and blastogenetic development. We characterised orthologues of placodal genes and constructed probes for in situ hybridisation experiments. During the stages of bud differentiation, we localised territories interested by expression of genes normally involved in the placodal induction and specification in vertebrates. These regions, for their position and differentiative potentialities, are comparable to other embryonic domains of B. schlosseri that are considered as homologues to the neural placodes.
The larva of ascidians possesses a striated symmetrical musculature sharing some features with that of vertebrates and it flanks the dorsal tube and the notochord, representing a peculiar propriety of chordates. The acquisition of this new locomotory system probably required the parallel appearance of a sophisticated control of the coordination. The nervous system established new interactions and differentiated sensory structures that permitted the rapid perception of the environment by the mobile organism. At metamorphosis, the larval musculature is reabsorbed, while the cardiac and unstriated muscle fibres differentiate de novo from circulating mesenchymal cells. This plasticity constitutes the source of the evolutive potentiality of ascidians and thus we investigate its molecular and morphological bases. We isolated and characterised transcripts coding for muscle-specific genes, analysing the expression during the blastogenetic cycle of Botryllus, from the bud appearance to the adult regression. The use of different methods allowed the description of the organisation and differentiation of the unstriated muscle, confirming its unique proprieties. Taking together, our results contribute to the understanding of the origin and development of structures that represent an important starting point in the evolution and radiation of vertebrates.Negli 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.
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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.
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Afin de comprendre comment les cellules interprètent un signal graduel en une réponse binaire, j’ai étudié l’induction neurale de l’ascidie. Lors de ce processus, quatre cellules ectodermiques parmi les seize vont adopter un destin neural. FGF9/16/20, exprimé par les cellules mésendodermiques, est l’inducteur neural et active l’expression du gène Otx via ERK. Les surfaces de contact (SC) quantifiées entre les cellules ectodermiques et les cellules mésendodermiques exprimant FGF montrent que chaque cellule ectodermique est exposée à FGF et que les précurseurs neuraux ont les plus grandes SC avec les cellules mésendodermiques. En quantifiant l’activation d’ERK et de l’expression d’Otx, nous avons montré que chaque cellule ectodermique montre un niveau d’activation d’ERK proportionnel à sa SC avec les cellules exprimant FGF alors que l’expression d’Otx est restreinte aux quatre précurseurs neuraux. Un ligand ephrine est exprimé par les cellules ectodermiques et joue un rôle antagoniste à FGF. Dans les embryons où le signal ephrine a été bloqué, le niveau d’ERK augmente dans toutes les cellules ectodermiques proportionnellement aux SC avec les cellules exprimant FGF. Dans ces conditions, d’autres cellules ectodermiques montrent une expression ectopique d’Otx. Cela suggère que le signal ephrine réduit le niveau d’activation total d’ERK pour maintenir les cellules ectodermiques non neural sous le seuil requis pour l’expression d’Otx. Nous avons testé cette hypothèse en traitant des embryons, où la voie ephrine était inhibée, avec de faibles doses d’UO126 (inhibiteur de MEK). Ce traitement a suffi à rétablir l’expression normale d’Otx dans les quatre précurseurs neurauxTo 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
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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.
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Yeats, 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.
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I initially set out to identify the cap structure on the spliced leader RNA of Ciona intestinalis. During this investigation, I discovered a previously unobserved 53 nt transcript containing the spliced leader sequence. This transcript contained the usual metazoan spliced leader RNA cap, trimethylguanosine, while the canonical spliced leader RNA lacked this moiety, but likely contained a mP7PG cap. The cap structure of the trans-spliced troponin I mRNA matched that of the canonical spliced leader RNA, indicating that the canonical spliced leader RNA, not the 53 nt transcript, is the donor for troponin I. Further immunoprecipitation studies showed that both the canonical spliced leader RNA and the novel 53 nt transcript exist in association with Sm proteins. I cloned a genomic DNA segment containing four tandem repeats of the spliced leader RNA gene, and this was used as a probe in an in situ hybridization study that showed the vast majority of the spliced leader RNA genes reside on chromosome 8. Finally, I performed some preliminary work showing that outrons, the 5'-segments of pre-mRNAs removed by trans-splicing, may exist in sufficient quantities as to be detected by PCR amplification.Au 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.
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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.
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Au cours de mon travail de thèse, j'ai établi une procédure pour ordonner des motifs courts selon leur distribution dans le génome de C. Intestinalis autour d'un ensemble de gènes : plus une combinaison de motifs est regroupée autour des gènes exprimés spécifiquement dans un tissu, plus le score est élevé. Dans cette approche, j'ai intégré les résultats de la dissection d'un enhancer exprimé dans le neurectoderme antérieur qui indiquait une structure dupliquée. Ma procédure montre que les sites GATTA dupliqués sont une caractéristique générale des éléments cis-régulateurs du neurectoderme antérieur. Une recherche dans le génome entier pour ces séquences suivi par un test in-vivo montre une expression dans ce territoire pour la moitié des éléments. Par la suite, j'ai essayé d'améliorer l'annotation des séquences cis-régulatrices déjà publiées, par une extraction automatique à partir de la littérature. Grâce à l'augmentation du nombre de publications en accès libre et l'amélioration des procédures expérimentales de plus en plus de ce type de données est disponible. Finalement, j'ai montré que malgré l'absence d'alignements non-codants entre les génomes des vertébrés et C. Intestinalis, on peut cependant trouver quelques loci avec une conservation extrême de l'arrangement des gènes. Pour ces cas, la recherche des éléments cis-régulateurs peut être limitée aux introns du gène voisin, ce qui était confirmé dans la littérature pour certains. Ces trois approches montrent l'utilité de la bioinformatique pour une meilleure caractérisation des séquences cis-régulatrices et ouvrent la voie aux validations expérimentales supplémentairesIn 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
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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.
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Biological invasions pose a serious threat to biodiversity world-wide. Through various means, such as competition or predation, invaders can radically change species composition and the functioning of native ecosystems. Even though our understanding of the mechanisms underlying invasion success is improving, there is still a lack of knowledge on the response of native species under pressure from invasion. This study adds to existing knowledge on the responses of a native species to invasion by non-indigenous species.
Pyura pachydermatina is a native ascidian in the southeast coast of New Zealand currently under pressure from increased urbanisation and invasion by other ascidian species. The
reproductive strategies employed by P. pachydermatina are investigated and the role of these strategies to increase its resistance to invasion are assessed. A population study on the status of P. pachydermatina around the Banks Peninsula was carried out in Camp Bay, Pigeon Bay, and Wainui. Spawning experiments using P. pachydermatina and gonad histology were done regularly during the one year study period to assess its ability to self-fertilise and determine
its reproductive period. In addition, predation experiments were carried out to assess the susceptibility of P. pachydermatina early life stages to two amphipod predators.
The surveys indicated that the populations of P. pachydermatina in the three sites are different from one another. Wainui has on average the largest individuals of P.
pachydermatina and Camp Bay, the smallest. Abundance of P. pachydermatina was highest in Pigeon Bay and lowest in Wainui. The three life stages of Pyura pachydermatina; recruits, juveniles, and adults, were present in all sites at all seasons. The spawning experiments confirmed the species’ ability to self-fertilise and that it has a year-round spawning period.
The two amphipod predators, Jassa marmorata and Caprella mutica, were efficient in consuming the egg and larval stages of P. pachydermatina, but did not feed on the settlers.
Year-round reproduction and the ability to self-fertilise potentially give P. pachydermatina increased resistance to the effects of urbanisation and invasion. This population study
suggested that the species is thriving around the Banks Peninsula. This, combined with previous studies on the non-indigenous ascidian Styela clava that stated the static or declining populations of the potential invaders, gives a positive outlook for the native species for the future. I suggest the use of genetic techniques to assess, in more detail, the population structure and dispersal potential of this native species. I also suggest constant monitoring of native species is required to keep up to date with the current status of the species, which will in turn help management decisions should regional spread of the Lyttelton S. clava invasion
occur in the future.
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Pyriohou, 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.
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Morris, 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.
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Three modified cyclic peptides were isolated from a sample of the ascidian Lissoclinum patella by solvent extraction methods and their structures elucidated using NMR and MS. The major compound was identified as petallamide C and the two minor compounds as new members of the lissoclinamide family of peptides. They were named lissoclinamide 9 and lissoclinamide 10. The metal binding properties of the three cyclic peptides were then studied by circular dichroism (CD ) and by MS. All three were found to bind copper and zinc, and binding constants for these were calculated from CD titrations and from MS monitored titrations. Competition experiments showed that both patellamide C and lissoclinamide 10 selectively bound copper in the presence of zinc. No selectivity was shown by lissoclinamide 9. None of the compounds were found to bind any other metals. Patellamide C was found to alter conformation on binding to copper. It's binding properties were compared to those of petellamide A, a related compound from Lissoclinum patella. Solution conformations of patellamide C and lissoclinamide 9 were generated computationally using nOe restrained modelling. The solution conformations of zinc bound and of copper bound patellamide C were also produced by this method. Binding sites for copper within the patellamides and the lissoclinamides were proposed.
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Montenegro, 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.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoEste 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.
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Davis, Rohan. "Chemical Investigations of Great Barrier Reef Ascidians - Natural Product and Synthetic Studies". Thesis, Griffith University, 2000. http://hdl.handle.net/10072/366561.
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This thesis describes the chemical investigations of several ascidian species collected from the Great Barrier Reef, Queensland, Australia. The thesis is divided into two separate components, Part A focuses on the isolation and structure elucidation of 11 previously undescribed ascidian metabolites. All structures were assigned using a combination of spectroscopic and/or chemical methods. Part B relates to the isolation and chemical conversion of a natural product to a combinatorial template. The natural product template was subsequently used in the generation of a solution-phase combinatorial chemistry library. A further two combinatorial libraries were generated from a synthesised model compound that was related to the natural product template. Part A. Investigation of Aplidium longithorax collected from the Swains Reefs resulted in the isolation of two new para-substituted cyclofarnesylated quinone derived compounds, longithorones J (30) and K (31). The former compound had its absolute stereochemistry determined by the advanced Mosher method. From an Aplidium longithorax collected from Heron Island, two new cyclofarnesylated hydroquinone compounds, longithorols C (46) and D (47) and a novel macrocyclic chromenol, longithorol E (48) were isolated. Longithorol C (46) had its absolute stereochemistry determined by the advanced Mosher method. Chemical investigation of the deep-purple colonial ascidian, Didemnum chartaceum collected from Swains Reefs led to the isolation of five new lamellarin alkaloids, which included the 20-sulfated derivatives of lamellarins B (94), C (95) and L (96), the 8-sulfated derivative of lamellarin G (97) and the non-sulfated compound, lamellarin Z (98). The known lamellarins A (63), B (80), C (64), E (65), G (67), and L (71) plus the triacetate derivatives of lamellarin D (82) and N (83) were also isolated. An aberration in the integration of signals in the 1H NMR spectra of the 20-sulfated derivatives (94-96) led to NMR relaxation studies. T1 values were calculated for all protons in the sulfated lamellarins (94-97) and their corresponding non-sulfated derivatives (80, 64, 71, 67). The protons ortho to the sulfate group in compounds (94-97) had T1 values up to five times larger than the corresponding protons in their non-sulfated derivatives (80, 64, 71, 67). A specimen of Eudistoma anaematum collected from Heron Island was shown to contain a new b-carboline alkaloid, eudistomin V (130), in addition to the two known metabolites, eudistomin H (105) and I (106). Part B. The known natural products, 1,3-diphenethylurea (29), 1,3-dimethylxanthine (30), 1,3-dimethylisoguanine (31) and the salts of tambjamine C (16), E (18) and F (19) were isolated from the ascidian, Sigillina signifera collected in Blue Lagoon, Lizard Island. Base hydrolysis on mixtures of the salts of tambjamine C (16), E (18) and F (19) resulted in the production of 4-methoxy-2,2-bipyrrole-5-carbaldehyde (26). This natural product template (26) was used in the generation of an enamine combinatorial chemistry library (98, 103-111) using solution-phase parallel synthesis. The biaryl compound, 4-(2-thienyl)-1H-pyrrole-2-carbaldehyde (59) was successfully synthesised using Suzuki-Miyaura coupling conditions and subsequently used as a template in the generation of an amine (67, 77, 80-87) and imine (78, 92-95) combinatorial library using solution-phase parallel synthesis.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Science
Full Text
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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.
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Chez l’ascidie coloniale Botryllus schlosseri, en plus de l’embryogénèse existent deux voies de développement aboutissant à la production de la même structure : l’organisme adulte ou zooide. Ces développements alternatifs ont lieu lors de processus biologiques distincts : le bourgeonnement palléal (BP) et le bourgeonnement vasculaire (BV). Le BP est un processus de multiplication asexuée présentant une ontogénèse stéréotypée. En revanche, le BV est un phénomène régénératif, induit dans les vaisseaux sanguins de la colonie par l’ablation de tous les zooides et bourgeons palléaux. Mes travaux de recherche ont eu pour objectif de caractériser les bases moléculaires et cellulaires régissant le BP et le BV chez B. schlosseri. L’étude de gènes marqueurs des lignées méso-, endo- et ectodermiques a révélé l’existence de territoires présomptifs pour chacune de ces lignées, dès les premiers stades du BV et du BP, et suggéré l’existence d’un programme unique aux deux processus. Les lignées neurales et musculaires ont été étudiées plus en détail lors du BP, indiquant un double rôle potentiel, neuro- et myo-génétique, au tube dorsal, une structure jusqu’à présent uniquement associée au système nerveux. Une caractérisation morphologique poussée a mené à l’identification de stades précoces stéréotypés du BV lors de la régénération. Enfin, l’analyse de transcriptomes de différents stades du BP et de la régénération ont initié l’étude non biaisée des bases moléculaires du bourgeonnement chez Botryllus. L’objectif à long terme de ces travaux est de décrypter les bases moléculaires et génétiques facilitant, chez les métazoaires, l’évolution de voies de développement alternativesIn 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
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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.
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The research presented in this document focuses on the development of the larval peripheral nervous system of the Tunicate Ciona intestinalis with two main aims: a) to understand how the interactions between Retinoic Acid (RA) and the FGF/WNT pathways control its development; b) to study the role played by transcription factors of the POU family in its differentiation. Within chordates, tunicates represent the sister group of vertebrates and their larvae have a typical chordate body plan. Notably, larval nervous system is formed by few cells whose organization mirrors that of vertebrates. For these reasons the species C. intestinalis, whose genome is completely sequenced, is a good animal model often used to understand the basic mechanisms of Chordate development. POU genes are an important family of transcription factors with several members that regulate the neural patterning and differentiation in both vertebrate and invertebrate embryos. C. intestinalis has only three genes coding for POU transcription factors: Ci-POU-2 Ci-POU-IV and Ci-POU-like. The gene Ci-POU-IV is specifically expressed in all peripheral nervous system (PNS) territories and in some cells of the central nervous system (CNS) during development. Since the expression of the two other genes was not previously studied in detail, a part of this research consisted in their characterization. Several experiments of in situ hybridization showed that the transcripts of Ci-POU-2 are present early during cleavage stages while Ci-POU-like gene expression is restricted to the lateral mesenchime cells of the larva and to their precursors during embryonic development. Thus the research was focused on the Ci-POU-IV gene. Its expression had been formerly studied by the research team of Prof. De Bernardi that discovered the existence of two alternative transcripts. In order to study the role that they play in neural differentiation Morpholino oligos were designed to perform gene knock-down experiments for the two different isoforms. The results from these experiments revealed that the expression of the serotonin rate-limiting synthesis enzyme, tryptophane hydroxylase (TPH), and glutamate transporter (vGlut) in the PNS neurons could be regulated by the product of the long transcript. To verify if the alternative transcripts were expressed in different PNS neuron populations in situ hybridizations were performed with a probe selective for the short isoform. These in situ hybridizations, compared to the whole expression profile of Ci-POU-IV, showed a lack of expression of the short form in the sensory epidermal neurons of the trunk. Moreover experiments were performed to understand the relationship between Ci-POU-IV and the Delta/Notch pathway. The latter has an important role in determining the cell to cell interactions in a number of taxa and to affect the neural or the epidermal fate of the PNS precursors. The Delta/Notch pathway was inhibited both using DAPT that inhibits the –secretase, responsible of the correct functioning of the pathway and electroporing the pFOG::VeSu(H)DBM construct that blocks the pathway activity. Embryos treated showed an abnormal development of epidermic sensorial neurons and the following in situ hybridizations for Ci-POU-IV pointed out an ectopic expression of the gene. Furthermore the study looked for the Ci-POU-IV targets in order to identify the genes regulated by Ci-POU-IV during the PNS differentiation. A bioinformatic approach was used. The possible consensus sequences were obtained by bibliographic research of those known for the POU IV family in both invertebrates and vertebrates. These sequences have been used to build a matrix that was employed to perform a bioinformatic research in the whole C. intestinalis genome with a software elaborated by the Lemaire team of the IBDML of Marseille. The search identified 19 possible targets of Ci-POU-IV; 8 regions, corresponding to 6 genes including TPH, have been preliminary selected. The activity of the selected regions is being evaluated.
The second part of the thesis has been developed during a period of research with Dr. A. Pasini at the Institut de Biologie du Développent of Marseille. The aim was to identify the mechanisms with which RA and the FGF/WNT pathways act on antero-posterior differentiation of PNS during C. intestinalis embryonic development. In vertebrates it was already known that during the antero-posterior extension of the body axis these pathways antagonize each other to coordinate mesoderm and nervous system differentiation. For this reason the hypothesis that an analogous mechanism could occur in other Chordates, including tunicates was tested. Thus in C. intestinalis I performed in situ hybridizations for different genes potentially involved in this mechanism. I employed also the electroporation technique with specific constructs. In particular results showed that the expression of the gene Ci-Raldh that codes for Retinaldehyde dehydrogenase, the enzyme responsible of RA synthesis, is confined to the anterior part of the tail in tailbud stage embryos. To this region is limited also the expression of some gene responsive to RA such as Ci-Hox-1 and Ci-Cyp26. On the contrary, at the posterior extremity of the tail it is predictable the existence of a source of FGF and WNT signals as shown by the expression of Ci-FGF-8 and Ci-WNT-5. Moreover, embryos treated with RA showed Ci-Hox-1 up-regulation at throughout tail epidermis and the inhibition of the posterior Ci-Hox-12 expression. On the contrary, embryos treated with FGF showed an opposite situation with Ci-Hox-12 activation and Ci-Hox-1 inhibition. Moreover, quantifications of differentiated caudal epidermal neurons and meticulous analysis of their position along the tail have been performed in late stage embryos treated with RA, FGF, their respective inhibitors and an inhibitor of the enzyme Ci-Cyp26, responsible for RA catabolism. This showed significant alterations in both the number of neurons and their position. In particular RA treatment increased the oveall number of caudal epidermal neurones but causes the loss of the most posterior ones; on the contrary FGF treatment induced a decrease in the number of neurons but maintained the posterior ones. Treatment with FGF and Ci-Cyp26 inhibitors mimicks the effects of RA while treatment with RA synthesis inhibitor mimicks the effect of FGF. On the whole a complex picture of antagonistic interactions, both direct and indirect has been revealed posing interesting questions from an evolutionary point of view.
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Ricci, 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.
Pełny tekst źródłaStreszczenie:
Chez l’ascidie coloniale Botryllus schlosseri, en plus de l’embryogénèse existent deux voies de développement aboutissant à la production de la même structure : l’organisme adulte ou zooide. Ces développements alternatifs ont lieu lors de processus biologiques distincts : le bourgeonnement palléal (BP) et le bourgeonnement vasculaire (BV). Le BP est un processus de multiplication asexuée présentant une ontogénèse stéréotypée. En revanche, le BV est un phénomène régénératif, induit dans les vaisseaux sanguins de la colonie par l’ablation de tous les zooides et bourgeons palléaux. Mes travaux de recherche ont eu pour objectif de caractériser les bases moléculaires et cellulaires régissant le BP et le BV chez B. schlosseri. L’étude de gènes marqueurs des lignées méso-, endo- et ectodermiques a révélé l’existence de territoires présomptifs pour chacune de ces lignées, dès les premiers stades du BV et du BP, et suggéré l’existence d’un programme unique aux deux processus. Les lignées neurales et musculaires ont été étudiées plus en détail lors du BP, indiquant un double rôle potentiel, neuro- et myo-génétique, au tube dorsal, une structure jusqu’à présent uniquement associée au système nerveux. Une caractérisation morphologique poussée a mené à l’identification de stades précoces stéréotypés du BV lors de la régénération. Enfin, l’analyse de transcriptomes de différents stades du BP et de la régénération ont initié l’étude non biaisée des bases moléculaires du bourgeonnement chez Botryllus. L’objectif à long terme de ces travaux est de décrypter les bases moléculaires et génétiques facilitant, chez les métazoaires, l’évolution de voies de développement alternativesIn 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