Dissertations / Theses: 'Developmental biology/pattern formation'

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Hunt, Gordon S. "Mathematical modelling of pattern formation in developmental biology." Thesis, Heriot-Watt University, 2013. http://hdl.handle.net/10399/2706.

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The transformation from a single cell to the adult form is one of the remarkable wonders of nature. However, the fundamental mechanisms and interactions involved in this metamorphic change still remain elusive. Due to the complexity of the process, researchers have attempted to exploit simpler systems and, in particular, have focussed on the emergence of varied and spectacular patterns in nature. A number of mathematical models have been proposed to study this problem with one of the most well studied and prominent being the novel concept provided by A.M. Turing in 1952. Turing's simple yet elegant idea consisted of a system of interacting chemicals that reacted and di used such that, under certain conditions, spatial patterns can arise from near homogeneity. However, the implicit assumption that cells respond to respective chemical levels, di erentiating accordingly, is an oversimpli cation and may not capture the true extent of the biology. Here, we propose mathematical models that explicitly introduce cell dynamics into pattern formation mechanisms. The models presented are formulated based on Turing's classical mechanism and are used to gain insight into the signi cance and impact that cells may have in biological phenomena. The rst part of this work considers cell di erentiation and incorporates two conceptually di erent cell commitment processes: asymmetric precursor di erentiation and precursor speci cation. A variety of possible feedback mechanisms are considered with the results of direct activator upregulation suggesting a relaxation of the two species Turing Instability requirement of long range inhibition, short range activation. Moreover, the results also suggest that the type of feedback mechanism should be considered to explain observed biological results. In a separate model, cell signalling is investigated using a discrete mathematical model that is derived from Turing's classical continuous framework. Within this, two types of cell signalling are considered, namely autocrine and juxtacrine signalling, with both showing the attainability of a variety of wavelength patterns that are illustrated and explainable through individual cell activity levels of receptor, ligand and inhibitor. Together with the full system, a reduced two species system is investigated that permits a direct comparison to the classical activator-inhibitor model and the results produce pattern formation in systems considering both one and two di usible species together with an autocrine and/or juxtacrine signalling mechanism. Formulating the model in this way shows a greater applicability to biology with fundamental cell signalling and the interactions involved in Turing type patterning described using clear and concise variables.

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Cruywagen, Gerhard C. "Tissue interaction and spatial pattern formation." Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:f242b785-9b46-4c21-a789-477b025ce4b3.

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The development of spatial structure and form on vertebrate skin is a complex and poorly understood phenomenon. We consider here a new mechanochemical tissue interaction model for generating vertebrate skin patterns. Tissue interaction, which plays a crucial role in vertebrate skin morphogenesis, is modelled by reacting and diffusing signal morphogens. The model consists of seven coupled partial differential equations, one each for dermal and epidermal cell densities, four for the signal morphogen concentrations and one for describing epithelial mechanics. Because of its complexity, we reduce the full model to a small strain quasi-steady-state model, by making several simplifying assumptions. A steady state analysis demonstrates that our reduced system possesses stable time-independent steady state solutions on one-dimensional spatial domains. A linear analysis combined with a multiple time-scale perturbation procedure and numerical simulations are used to examine the range of patterns that the model can exhibit on both one- and two-dimensions domains. Spatial patterns, such as rolls, squares, rhombi and hexagons, which are remarkably similar to those observed on vertebrate skin, are obtained. Although much of the work on pattern formation is concerned with synchronous spatial patterning, many structures on vertebrate skin are laid down in a sequential fashion. Our tissue interaction model can account for such sequential pattern formation. A linear analysis and a regular perturbation analysis is used to examine propagating epithelial contraction waves coupled to dermal cell invasion waves. The results compare favourably with those obtained from numerical simulations of the model. Furthermore, sequential pattern formation on one-dimensional domains is analysed; first by an asymptotic technique, and then by a new method involving the envelopes of the spatio-temporal propagating solutions. Both methods provide analytical estimates for the speeds of the wave of propagating pattern which are in close agreement with those obtained numerically. Finally, by numerical simulations, we show that our tissue interaction model can account for two-dimensional sequential pattern formation. In particular, we show that complex two-dimensional patterns can be determined by simple quasi-one-dimensional patterns.

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Baker, Ruth E. "Periodic pattern formation in developmental biology : a study of the mechanisms underlying somitogenesis." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418815.

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Somitogenesis, the sequential formation of a periodic pattern along the antero-posterior axis of vertebrate embryos, is one of the most obvious examples of the segmental patterning processes that take place during embryogenesis and also one of the major unresolved events in developmental biology. The principal aim of this thesis is to develop a series of mathematical models for somite formation. We begin by reviewing the current models for somitogenesis in the light of new experimental evidence regarding the presence of a segmentation clock and graded expression of FGF8. We conduct a preliminary investigation into the wavefront of FGF8 along the antero-posterior axis and integrate this model into the framework of an existing model for a signalling process. We demonstrate that this new “Clock and Wavefront” model can produce coherent series’ of somites in a manner that is tightly regulated in both space and time, and that it can also mimic the effects seen when FGF8 expression is perturbed locally. We then use the model to make some experimentally testable predictions. The latter part of the thesis concentrates on building more biologically accurate model for the FGF8 gradient. We move to consider a model for the FGF8 gradient which involves a complex network of biochemical interactions with negative feedback between FGF8 and retinoic acid. The resulting system of seven coupled non-linear equations, including both ordinary and partial differential equations, is difficult to analyse. To facilitate our understanding of the non-linear interactions between FGF8 and retinoic acid, we finally consider a reduced model which can display travelling wavefronts of opposing FGF8 and retinoic acid concentrations moving down the antero-posterior axis. The model allowed us to calculate a minimum wave speed for the wavefronts as a function of key model parameters such as the rate of FGF8 and retinoic acid decay; strong dependence on the values of these parameters is a result that is hypothesised to occur in vivo.

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Williamson, Carly Zoe. "A Computational Model of Divergent Pattern Formation in Caenorhabditis elegans and Caenorhabditis briggsae Vulval Development." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1460574181.

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Sadeghi, Nazlie. "The N-cadherin prodomain: regulation of synpase formation «in vivo» and developmental expression pattern in the zebrafish central nervous system." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=19229.

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The formation of neuronal connections in the central nervous system (CNS) occurs as nascent pre- and postsynaptic membranes are primed to generate a mature synaptic junctional complex. Although the precise sequence of events leading to synapse assembly is not well understood, the presence and adhesive capacity of a limited number of highly specialized molecules on the pre and post-synaptic membranes are thought to determine where and when synapses will form (Sperry et al, 1963; Fannon and Colman 1996; Craig et al, 2001). According to recent models of synaptogenesis, signaling through adhesion molecules at cell-cell contact sites leads to the progressive recruitment of pre- and postsynaptic constituents to these sites, resulting in synapse maturation. Presynaptic transport packets (also known as piccolo-bassoon transport packets or active zone precursor vesicles) are thought to deliver proteins en masse to nascent synapses (Zhai et al., 2001; Ziv and Garner 2004). Since N-cadherin is a prominent synaptic adhesion molecule and a significant constituent of these presynaptic transport packets, we hypothesized that it would play an important role in early synaptic development. Using time-lapse confocal microscopy on living embryonic zebrafish Rohon-Beard neurons, we found that modifying N-cadherin to contain an uncleavable prodomain prevents its targeting to microdomains and transiently suppresses synapse formation. Because neurogenesis and synapse formation continue to occur in defined areas of the adult fish brain, we performed an immunohistological survey of the expression pattern of the N-cadherin prodomain in adult zebrafish. The highest levels of expression were in areas believed to have elevated levels of synaptic plasticity
Le pro-domaine de la N-cadherin: Rôle dans la régulation de la synaptogenèse in vivo et expression pendant le développement du système nerveux central chez le poisson zébré. La formation de connections neuronales dans le système nerveux central (SNC) se produit lorsque des membranes pré et post-synaptiques nouvellement formées sont conditionnées à générer un complexe synaptique mature. Malgré notre compréhension limitée de la séquence précise d'évènements conduisant à la formation d'une synapse, la présence et le potentiel adhésif d'un petit nombre de molécules hautement spécialisées retrouvées sur certains sites pré et post-synaptiques semblent déterminer où et quand des synapses seront formées (Sperry et al, 1963; Fannon and Colman 1996; Craig et al, 2001). Selon les théories actuelles sur la synaptogenèse, un signalement intercellulaire par le biais de molécules adhésives présentes à certains sites de contact cellulaire conduit au recrutement graduel de constituants pré et post-synaptiques à ces sites, résultant ainsi en une maturation de la synapse. Dans la neurone pré-synaptique, il est conçu que les colis cellulaires (connus sous le nom de "piccolo-bassoon transport packets", "active zone precursor vesicles" ou tout simplement "transport packets" en anglais) livrent de grandes quantités de protéines aux synapses nouvellement générées (Zhai et al., 2001; Ziv and Garner 2004). Parce que la N-cadherin est une molécule adhésive prééminente de même qu'une constituante principale de ces colis cellulaires, nous avons émis l'hypothèse qu'elle pouvait jouer un rôle important aux origines du développement nerveux. En imageant des neurones "Rohon-Beard" de poissons zébrés à

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Srivastava, Vinit. "Pattern formation in the mammalian striatum, the development of the thalamostriatal projection in the rodent." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0023/MQ50884.pdf.

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Saavedra, Pedro Almeida Dias Guedes. "Pattern formation and planar cell polarity in Drosophila larval development : insights from the ventral epidermis." Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708010.

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Cheesman, Sarah Emily. "Dorsal ventral patterning of the central nervous system : lessons from flies and fish /." view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3113005.

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Thesis (Ph. D.)--University of Oregon, 2003.
Typescript. Includes vita and abstract. Includes bibliographical references (leaves 95-102). Also available for download via the World Wide Web; free to University of Oregon users.

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Schweickart, Robert Allen. "FRAZZLED PLAYS A ROLE IN THE FORMATION OF CELL DENSITY PATTERNS IN THE EARLY DROSOPHILA EMBRYO." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1545181299374722.

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Marín, de Mas Igor Bartolomé. "Development and application of novel model-driven and data-driven approaches to study metabolism in the framework of systems medicine." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/296313.

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The general aim of this thesis is to develop and apply new computational tools to overcome existing limitations in the analysis of metabolism. This thesis is focused on developing new computational strategies to overcome the following identified limitations: i) The existing metabolic flux analysis tools does not account for the existence of metabolic channeling: Here we developed a new computational tool based on non-stationary 13 C-FBA to evaluate different models reflecting different topologies of intracellular metabolism, using the channeling in hepatocytes as case of concep ii) Metabolic drug-target discovery based on GSMM does not consider the different cell subpopulations existing within the tumor: Here we develope a method that integrate trancriptomic data into a comparative genome-scale metabolic network reconstruction analysis in the context of intra-tumoral heterogeneity . We determined subpopulation-specific drug targets . Additionally we determined a metabolic gene signature associated to tumor progression in pc that was correlated with other types of cancer. Iii) Current mechanistic and probabilistic computational approaches are not suitable to study the complexity of the crosstalk between metabolic and gene regulatory networks.: Here we developed a novel computational method combining probabilistic and mechanistic approaches to integrate multi-level omic data into a discrete model-based analysis. This method allowed to analyze the mechanism underlying the crosstalk between metabolism and gene regulation, using as case of concept the study of the abnormal adaptation to training in COPD patients.
La presente tesis doctoral se centra en el desarrollo de herramientas computacionales que permitan el estudio de los mecanismos moleculares que ocurren dentro de la célula. Mas específicamente estudia el metabolismo celular desde diferentes puntos de vista usando y desarrollando métodos computacionales basados en diversas metodologías. Así pues en un primer capitulo se desarrolla un método basado en el analista de los flujos metabólicos en estado no estacional isotópico utilizando modelos cinéticos para estudiar el fenómeno de la canalización metabólica en hepatocitos. Este fenómeno modifica la topología metabólica alterando el fenotipo. Nuestro método nos permitió discriminar varios modelos con distintas topología prediciendo la existencia de canalización metabólica en la glucólisis. En el segundo capitulo se desarrolló un método para analizar el metabolismo tumoral teniendo en cuenta la heterogeneidad de poblaciones. En concreto estudiamos dos subpoblaciones extraídas de una linea celular de cáncer de próstata. Para ello utilizamos un modelo a gran escala de todo el metabolismo celular humano. El análisis reflejó la existencia de diferencias notables a nivel de vías metabólicas concretas, confiriendo a cada subpoblacion sensibilidades distintas a diferentes fármacos. En esta linea se demostró que mientras las células PC-3M eran sensibles al etomoxir e insensibles al calcitriol, las PC-3S presentaban una sensibilidad opuesta. En el tercero y ultimo capitulo de la tesis desarrollamos un nuevo método computacional que integra aproximaciones probabilísticas y mecanicistas para integrar diferentes tipos de datos en un análisis basado en modelos discretos. Para ello utilizamos como caso de concepto el estudio de la adaptación anómala al entrenamiento de pacientes con EPOC. El análisis reveló diferencias importantes a nivel de metabolismo energético en comparación con el grupo control.

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Reed, Robert Dale Jr. "The evolution of pattern formation in butterfly wings." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/290156.

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In this dissertation I employ a comparative gene expression approach to address the evolution of butterfly wing pattern formation at several levels, with emphasis on early pattern determination and pigment gene regulation during late development. Expression analysis of the receptor molecule Notch suggested previously unknown roles for Notch signaling in butterfly wing patterning. Notch upregulation was found to precede the activation of the transcription factor Distal-less during early eyespot color pattern determination. A phylogenetic comparison of expression time series from multiple moth and butterfly species suggested that changes in a Notch/Distal-less temporal pattern formation process were associated with the gain and loss of both eyespot and midline color patterns during wing pattern evolution. Additionally, Notch expression was found to occur in a grid-like pattern in the butterfly wing epithelium shortly after pupation. This observation, together with previous expression and simulation studies, support a Notch-mediated lateral inhibition model of wing scale organization. Tryptophan-derived ommochrome pigments are a derived feature of nymphalid butterfly wings. I found that multiple genes in the ommochrome biosynthetic pathway were expressed in the wings of selected nymphalid butterflies. Additionally, transcriptional regulation of genes encoding the ommochrome synthesis enzymes vermilion and cinnabar was found to be temporally and spatially associated with the polymorphism and development of forewing band patterns in the mimetic butterfly Heliconius erato. These findings provide evidence that changes in ommochrome gene regulation underlie the evolution and development of major nymphalid wing pattern elements.

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Yang, Xige. "MATHEMATICAL MODELS OF PATTERN FORMATION IN CELL BIOLOGY." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1542236214346341.

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Crawford, David Michael. "Analysis of biological pattern formation models." Thesis, University of Oxford, 1989. http://ora.ox.ac.uk/objects/uuid:aaa19d3b-c930-4cfa-adc6-8ea498fa5695.

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In this thesis we examine mathematical models which have been suggested as possibile mechanisms for forming certain biological patterns. We analyse them in detail attempting to produce the requisite patterns both analytically and numerically. A reaction diffusion system in two spatial dimensions with anisotropic diffusion is examined in detail and the results compared with certain snakeskin patterns. We examine two other variants to the standard reaction diffusion system: a system where the reaction kinetics and the diffusion coefficients depend upon the cell density suggested as a possible model for the segmentation sequence in Drosophila and a system where the model parameters have one dimensional spatial gradients. We also analyse a model derived from known cellular processes used to model the branching behaviour in bryozoans and show that, in one dimension, such a model can, in theory, give all the required solution behaviour. A genetic switch model for pattern elements on butterfly wings is also briefly examined to obtain expressions for the solution behaviour under coldshock.

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Ren, Xiaojing. "Modeling pattern formation of swimming E.coli." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43704001.

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Tewari, Aneesha G. (Aneesha Ghanhi). "Pattern formation and essential responses for regeneration in planarians." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122068.

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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
The fundamental requirements for regeneration are poorly understood. Planarians can robustly regenerate all tissues after injury, involving stem cells, patterning cues and a set of cellular and molecular responses collectively called the "missing tissue" or "regenerative" response. The missing tissue response has long been considered a fundamental requirement of planarian regeneration. follistatin, which encodes an extracellular Activin inhibitor, is required for the missing tissue response after head amputation, and for subsequent regeneration. We found that follistatin is required for the missing tissue response regardless of the wound context, but only causes regeneration failure after head amputation. This head regeneration failure involves follistatin-mediated regulation of Wnt signaling at wounds, and is not a consequence of a diminished missing tissue response.
We found that all tested contexts of regeneration, including head regeneration, could occur with a defective missing tissue response, however, at a slower pace. Our findings suggest that in the absence of major cellular and molecular programs induced by large injuries, regulation of wound-induced Wnt signaling to enable regenerative re-patterning along with continuous tissue turnover can mediate successful regeneration in essentially any wound context. Wnt signaling regulates primary body axis formation across the Metazoa, with high Wnt signaling specifying posterior identity. Whether a common Wnt-driven transcriptional program accomplishes this broad role is poorly understood. We identified genes acutely affected after Wnt signaling inhibition in the posterior of two regenerative species, the planarian Schmidtea mediterranea and the acoel Hofstenia miamia, which are separated by >550 million years of evolution.
Wnt signaling was found to maintain positional information in muscle and regional gene expression in multiple differentiated cell types. sp5, Hox genes, and Wnt pathway components are down-regulated rapidly after [beta]-catenin RNAi in both species. brachyury, a vertebrate Wnt target, also displays Wnt-dependent expression in Hofstenia. Planarian sp5 inhibits Wnt-dependent expression of trunk genes in the tail, promoting separate tail-trunk body domains. We propose that common regulation of a small gene set - Hox, sp5, and brachyury - might underlie the widespread utilization of Wnt signaling in primary axis patterning across the Bilateria.
by Aneesha G. Tewari.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Biology

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Lewis, Mark A. "Analysis of dynamic and stationary biological pattern formation." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276976.

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Thomson, J. Ross. "Models of pattern formation on the primate visual cortex." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55635.

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Marshall, Heather. "Retinoic acid and the developmental regulation of the Hoxb-1 gene during embryogenesis." Thesis, Open University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282309.

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Ren, Xiaojing, and 任晓晶. "Modeling pattern formation of swimming E.coli." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B43704001.

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Duran, Nebreda Salvador 1987. "Artificial multicellularity and pattern formation." Doctoral thesis, Universitat Pompeu Fabra, 2016. http://hdl.handle.net/10803/403584.

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En aquesta tesi hem intentat atacar preguntes relacionades amb els orígens de la vida multicel•lular i dels comportaments cooperatius a la nostra biosfera. Particularment hem fet ús de mètodes “no naturals”: la vida artificial i la biologia sintètica. A diferencia dels enfocs més tradicionals com la caracterització filogenètica i la biologia teòrica, aquests mètodes permeten observar les transicions en individualitat i complexitat a mesura que tenen lloc. Més concretament, en aquest projecte hem proposat noves regles per aconseguir sistemes de trencament de simetria espacial i com la multicel•lularitat amb diferenciació pot ser seleccionada des de genotips unicel•lulars amb les pressions selectives apropiades.
This project has tackled unanswered questions regarding the origins of multicellular life and cooperation using artificial approaches, namely: artificial evolution and synthetic biology. These offer unique opportunities to watch the evolution of complexity unfold and complement the extensively used methods of characterization of extant multicellular systems and theoretical biology. In particular we have proposed new mechanisms to create periodical structures in synthetic systems and how differentiated multicellularity might arise from Darwinian entities.

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Schrader, Jarmo. "Developmental biology of wood formation : finding regulatory factors through functional genomics /." Umeå : Dept. of Forest Genetics and Plant Physiology, Swedish Univ. of Agricultural Sciences, 2003. http://epsilon.slu.se/s292.pdf.

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Ferguson, James. "THE SPATIAL AND TEMPORAL ROLE OF EZH2 IN SKULL BONE FORMATION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1530898825341447.

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Fregoso, Santiago. "Pattern and Mechanism of Calcium Mobilization During Embryonic Development in a Viviparous Snake, Virginia striatula." Digital Commons @ East Tennessee State University, 2010. https://dc.etsu.edu/etd/1712.

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Yolk supplies the majority of embryonic calcium in snakes. Oviparous and viviparous snakes also receive calcium late in development from the eggshell and placenta, respectively. The pattern and mechanism of calcium transport are partly understood for oviparous snakes. I studied a viviparous snake, Virginia striatula, to determine the pattern of embryonic calcium accumulation as well as the ontogenetic expression of calcium transporting proteins in extraembryonic tissues. The pattern of embryonic calcium uptake of V. striatula occurs late in development, during the phase of highest embryonic growth. Calbindin-D28k, Ca2+ ATPase, and carbonic anhydrase II are expressed in chorioallantoic membrane, while yolk sac only expresses calbindin-D28k, coincident with the timing of calcium transport in embryos of V. striatula. Thus, the pattern of embryonic calcium accumulation in V. striatula is similar to that of oviparous snakes. Although calbindin-D28k and Ca2+ ATPase are likely active in embryonic calcium transport, the role of carbonic anhydrase II remains less clear.

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Joy, Ryan Mears. "Dcbld2/esdn Is Essential For Proper Optic Tract Formation And Retinal Lamination." ScholarWorks @ UVM, 2016. http://scholarworks.uvm.edu/graddis/563.

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ABSTRACT The Discoidin, CUB and LCCL domain-containing protein 2 (DCBLD2/ESDN/CLCP1) is a type-I, transmembrane receptor that mediates diverse cellular processes such as angiogenesis, vascular remodeling, cellular migration and proliferation. Identification of DCBLD2 in a proteomics screen to identify substrates of Src family tyrosine kinases that bind the Src homology 2 domain of CT10 regulator of kinase-Like (CrkL), a critical scaffolding protein for neuronal development, led to a need for further characterization of the protein. To elucidate the role of this interaction and potential novel function of DCBLD2, an in vivo approach utilizing Danio rerio (zebrafish) was conducted. dcbld2 was found localized in neuronal tissues during development, with strong expression in the retina. Knockdown of the protein led to a deficiency of retinal ganglion cells and the optic tracts, or nerve bundles, they project to innervate the brain. Serial sections revealed malformation of the normally discrete layering of retinal cell types, and smaller eye area overall. These findings suggest a role for dcbld2 in developing nervous tissue, specifically neuronal migration during interkinetic nuclear migration. While it is has been shown that dcbld2 has a role in the developmental patterning of intersegmental vessels in the tail of zebrafish, the protein has not been investigated in the context of neurogenesis. The loss of RGCs and lamination defects observed in the eye, along with its association with the CrkL-SH2 domain, implicate it in processes that allow for the proper differentiation of neurons. This study has brought us further down the path to understanding the multiple functions of the receptor; however, further studies are required to delineate the exact mechanistic function of the dcbld2 receptor.

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Liu, Chenli, and 刘陈立. "Formation of novel biological patterns by controlling cell motility." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B46541913.

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The Best PhD Thesis in the Faculties of Dentistry, Engineering, Medicine and Science (University of Hong Kong), Li Ka Shing Prize,2010-11
published_or_final_version
Biochemistry
Doctoral
Doctor of Philosophy

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Uygur, Aysu N. "Evolution of Morphology: Modifications to Size and Pattern." Thesis, Harvard University, 2014. http://dissertations.umi.com/gsas.harvard:11609.

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A remarkable property of developing organisms is the consistency and robustness within the formation of the body plan. In many animals, morphological pattern formation is orchestrated by conserved signaling pathways, through a process of strict spatio-temporal regulation of cell fate specification. Although morphological patterns have been the focus of both classical and recent studies, little is known about how this robust process is modified throughout evolution to accomodate different morphological adaptations.

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Fu, Xiongfei, and 傅雄飞. "Quantitative study of pattern formation on a density-dependent motility biological system." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48199424.

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Quantitative biology is an emerging field that attracts intensive research interests. Pattern formation is a widely studied topic both in biology and physics. Scientists have been trying to figure out the basic principles behind the fascinating patterns in the nature. It’s still difficult to lift the complex veil on the underling mechanisms, especially in biology, although lots of the achievements have been achieved. The new developments in synthetic biology provide a different approach to study the natural systems, test the theories, and develop new ones. Biological systems have many unique features different from physics and chemistry, such as growth and active movement. In this project, a link between cell density and cell motility is established through cell-cell signaling. The genetic engineered Escherichia coli cell regulates its motility by sensing the local cell density. The regulation of cell motility by cell density leads to sequential and periodical stripe patterns when the cells grow and expand on a semi-solid agar plate. This synthetic stripe pattern formation system is quantitative studied by quantitative measurements, mathematical modeling and theoretical analysis. To characterize the stripe pattern, two novel methods have been developed to quantify the key parameters, including cell growth, spatiotemporal cell density profile and cell density-dependent motility, besides the standard molecular biological measurements. To better understand the underlying principle of the stripe pattern formation, a quantitative model is developed based on the experiments. The detailed dynamic process is studied by computer simulation. Besides, the model predicts that the number of stripes can be tuned by varying the parameters in the system. This has been tested by quantitatively modulation of the basal expression level of a single gene in the genetic circuit. Moreover, theoretical analysis of a simplified model provides us a clear picture of the stripe formation process. The steady state traveling wave solution is obtained, which leads to an analytic ansatz that can determine the phase boundary between the stripe and the no-stripe phases. This study does not only provide a quantitative understanding about the novel mechanism of stripe pattern formation, but also sets an good example of quantitative studies in biology. The techniques, methods and knowledge gleaned here may be applied in various interdisciplinary fields.
published_or_final_version
Physics
Doctoral
Doctor of Philosophy

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So, Young Lee. "Initiation of Innate Immune Responses in the Freshwater Crayfish Pacifastacus leniusculus." Doctoral thesis, Uppsala University, Department of Evolutionary Biology, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-623.

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Prophenoloxidase (proPO) is a key enzyme for generation of melanin and is activated by the proPO activating enzyme (ppA) to its active form, PO. The active ppA was purified and cloned from crayfish hemocytes and it is a typical serine proteinase containing a clip, a proline-rich, and a glycine-rich domain. A recombinant protein containing the clip-domain, with homology to horseshoe crab big defensin and mammalian â-defensin, had antibacterial activity in vitro against gram-positive bacteria.

The proPO activating system (proPO system) is triggered by lipopolysaccharides (LPS) or â-1,3-glucans. An LPS and â-1,3-glucan binding protein (LGBP) was characterized from crayfish hemocytes. The results of an LGBP antibody inhibition assay suggest that LGBP is directly involved in the proPO system.

The primary structure of a crayfish masquerade-like (mas) protein has homology to serine proteinases except for a substitution within the catalytic triad, which renders it without proteinase activity. The crayfish mas-like protein has also binding activity to various gram-negative bacteria and yeast. When the mas-like protein binds to microorganisms, it is processed by a proteolytic enzyme. The mas-like protein exhibited cell adhesion and opsonic activities suggesting that it plays a role in defense against parasites.

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Karam, Sana. "Mechanisms of pattern formation in the developing cerebellum : role for Eph receptor gene family /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/10557.

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30

Melville, Heather. "Spatiotemporal analysis of apoptosis patterns in the developing brain of the Brd2-knockdown zebrafish embryo." Click here for download, 2009. http://proquest.umi.com/pqdweb?did=1851609811&sid=1&Fmt=2&clientId=3260&RQT=309&VName=PQD.

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31

Nodine, Michael. "The Analysis of Two Receptor-like Kinases Redundantly Required for Pattern Formation during Arabidopsis Embryogenesis." Diss., The University of Arizona, 2007. http://hdl.handle.net/10150/194199.

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The coordination of various cellular differentiation and morphogenetic programs during plant embryogenesis is required to establish the basic adult body plan. The molecular basis of these patterning events remains to be fully understood. In particular, little is known about the roles of cell-cell signaling during embryonic pattern formation.I identified two receptor-like kinases, RECEPTOR-LIKE PROTEIN KINASE1 (RPK1) and TOADSTOOL2 (TOAD2), redundantly required for Arabidopsis thaliana embryonic pattern formation. Genetic analysis indicates that RPK1 and TOAD2 have overlapping embryonic functions. The zygotic gene dosage of TOAD2 in an rpk1 background is of critical importance, suggesting that signaling mediated by RPK1 and TOAD2 must be above a threshold level for proper embryo development. The localization of RPK1 and TOAD2 translational fusions to GFP coupled with the analysis of cell-type specific markers indicate that RPK1 and TOAD2 are redundantly required for both pattern formation along the radial axis and differentiation of the basal pole during early embryogenesis.I found that RPK1 and TOAD2 also have overlapping functions required for cotyledon primordia initiation during Arabidopsis embryogenesis. Genetic analyses indicate that cotyledon initiation is sensitive to TOAD2 gene dosage in an rpk1 background. Analysis of cell-specific markers suggest that RPK1 and TOAD2 are primarily required for the differentiation of cell types (i.e. the central domain protoderm) subjacent to the cotyledon primordia, and that the cotyledon initiation defects are caused by defects in the central domain protoderm. In addition, RPK1-GFP and TOAD2-GFP translational fusions had overlapping localization patterns in the central domain protodermal cells when cotyledon primordia were first recognizable. I propose that RPK1 and TOAD2 are primarily required to maintain central domain protoderm cell fate and that the loss of this key embryonic cell type in mutant embryos results in patterning defects throughout the embryo including the failure to initiate cotyledon primordia.This work has identified two putative receptors for cell-cell signals that mediate key patterning events during plant embryogenesis. The future identification of components in the RPK1 and/or TOAD2 signaling pathways will yield further insight into the molecular basis of the generation and assembly of diverse embryonic cell types.

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32

Kershner, Leah. "RACK1 regulates point contact formation and local translation in neuronal growth cones." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1524159362714285.

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33

Conner, Rebecca. "The Effects of Adjacent Cell Fusion and Ultraviolet Radiation Exposure on Viral Plaque Formation with Herpes Simplex Virus Type I." TopSCHOLAR®, 1986. http://digitalcommons.wku.edu/theses/1906.

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In mammalian cell-virus systems, it has been observed that damage caused by exposure of the cell to ultraviolet radiation (UV) will result in an increase in viral plaque development rate. This phenomenon is termed the Large Plaque Effect (LPE). Apparently, viral plaque development increases at a faster rate for Herpes Simplex Virus (HSV) when it is assayed on certain UV-irradiated mammalian cells. The consequence of this increase in plaque development rate is that viral plaques appear larger on irradiated monolayers of cells when compared to plaques that developed on unirradiated cellular monolayers. The cause of the LPE is not yet understood. It is though that the enhancement of plaque development, due to UV damage, is a manifestation of the excision repair mechanisms operating on the cellular genome. It is known that agents that act like UV and inhibit DNA synthesis, such as hydroxyurea, caffeine, and the carcinogen N-acetoxy-2-acetylaminofluorene, can produce the LPE. Conversely, cyclohexamide, which inhibits de novo protein synthesis, can completely prevent the LPE caused by UV. There is also some evidence of a cellular membrane effect involved in generating a non-UV LPE as observed in work with dimethyl sulfoxide. In addition, certain syncytial mutants of HSV are known to enhance membrane fusion.

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Kendall, Bruce Edward. "Spatial structure and transient periodicity in biological dynamics." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/187496.

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Structure, in its many forms, is a central theme in theoretical population ecology. At a mathematical level, it arises as nonuniformities in the topology of nonlinear dynamical systems. I investigate a mechanism wherein a chaotic time series can have episodes of nearly periodic dynamics interspersed with more 'typical' irregular dynamics. This phenomenon frequently appears in biological models, and may explain patterns of alternating biennial and irregular dynamics in measles epidemics. I investigate the interaction between spatial structure and density-dependent population regulation with a simple model of two logistic maps coupled by diffusive migration. I examine two different consequences of spatial structure: scale-dependent interactions ("nonlocal interactions") and spatial variation in resource quality ("environmental heterogeneity"). Nonlocal interactions allow three general dynamical regimes: in-phase, out-of-phase, and uncorrelated. With environmental heterogeneity, the dynamics of the total population size can be approximated by a logistic map with the mean growth parameter of the two patches; the dynamics within a single patch are often less regular. Adding environmental heterogeneity to non-local interactions has little qualitative effect on the dynamics when the differences between patches are small; when the differences are large, uncorrelated dynamics are most likely to be seen, and there are interesting consequences for the stability of source-sink systems. A third type of structure arises when individuals differ from one another. Accurate prediction of extinction risk in small populations requires that a distinction be made between demographic stochasticity (variation among individuals) and environmental stochasticity (variation among years or sites). I describe and evaluate two tests to determine whether all the variation in population survivorship can be explained by demographic stochasticity alone. Both tests have appropriate probabilities of type I error, unless the survival probability is very low or very high. Small amounts of environmental stochasticity are often not detected by the tests, but the hypothesis of demographic stochasticity alone is consistently rejected when environmental stochasticity is large. I also show how to factor out deterministic sources of variability, such as density-dependence. I illustrate these tests with data on a population of Acorn Woodpeckers.

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Easley-Neal, Courtney Nichelle 1981. "Synapse Formation in the Zebrafish Spinal Cord." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/12028.

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xv, 102 p. : ill. (some col.)
This dissertation describes research to elucidate the early steps in the process of synapse formation in the zebrafish spinal cord. One question is how presynaptic proteins are trafficked and recruited to nascent synapses. Previous work has suggested two possible models of presynaptic transport, either (1) most presynaptic proteins are transported together or (2) two types of transport packets, synaptic vesicle (SV) protein transport vesicles (STVs) and Piccolo-containing active zone precursor transport vesicles (PTVs), transport the necessary components separately. We tested these models using in vivo imaging in zebrafish spinal cord and found that the recruitment of at least three distinct transport packets during presynaptic assembly of a glutamatergic synapse occurs in an ordered sequence. First, STVs are stabilized at future synaptic sites, then PTVs, followed by a third transport packet type carrying Synapsin, a cytosolic protein that can tether SVs to actin. These results identify an order to the assembly of the presynaptic terminal in vivo, suggesting that a single synaptogenic interaction may precipitate the cascade of recruitment steps. We next examined the Cadm/SynCAM family of cell adhesion molecules, a family of proteins that has been shown to be able to induce synapse formation in vitro and was thought to play a role in recruitment of presynaptic proteins. As the role of these proteins in vivo was not well understood, we chose to examine the role of the cadms in zebrafish spinal cord. We found that zebrafish possess six cadm genes, and all are expressed throughout the nervous system both during development and in the adult. We then looked at the role of one of the Cadms, Cadm2a, in vivo in the zebrafish spinal cord. We found that knockdown of cadm2a significantly decreases the ability of zebrafish embryos to respond to touch. We also found that there is a significant reduction in the number of synapses, as shown by immunohistochemistry, formed between Rohon-Beard and CoPA neurons, the first two cell types in the touch response circuit. These data suggest that Cadm2a plays an important role in synapse formation in vivo. This dissertation contains both my previously published and unpublished co-authored material.
Committee in charge: Monte Westerfield Chairperson; Philip Washbourne, Advisor; Judith Eisen, Member; Tory Herman, Member; Mike Wehr, Outside Member

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Song, Yuntao. "Epigenetic repression of retinoic acid responsive genes for cardiac outflow tract formation." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563295948947138.

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37

Hatem, Iyad. "Hybrid multivariate classification technique and its application in tissue image analysis /." free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3091929.

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38

Vasanthi, G. "Hormones and Cuscuta Development Abscisic Acid And Its Conjugates-Endogenous Levels And Metabolism During Growth And Haustoria Formation." Thesis, Indian Institute of Science, 1994. http://hdl.handle.net/2005/102.

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Cuscuta or dodder is one of the best known higher plant parasite with around 158 species over 5 continents parasitising a wide variety of host plants (Yuncker,1932) Dodders are characterised by their interesting parasitic behaviour and extraordinary appearance among the obligate parasitic flowering plants (Kuijt, 1969)

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Kuerbitz, Jeffrey S. "Formation and Function of Amygdala Circuitry: Differentiation and Migration of Intercalated Cells (ITCs) and their Role in Fear, Depression and Social Behavior." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535457845286194.

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40

Zhang, Xinghao. "A Comprehensive Structure-Function Study of Neurogenin3 during Human Endocrine Cell Formation in the Pancreas and Intestine." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1583155296519998.

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41

Vithayathil, Joseph. "Developmental and Post-natal Roles for ERK1/2 Signaling in the Hippocampus." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1435760090.

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42

Ddumba, Hassan. "Repulsive-attractive models for the impact of two predators on prey species varying in anti-predator response." Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/d1010995.

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This study considers the dynamical interaction of two predatory carnivores (Lions (Panthera leo) and Spotted Hyaenas (Crocuta crocuta)) and three of their common prey (Buffalo (Syncerus caffer), Warthog (Phacochoerus africanus) and Kudu (Tragelaphus strepsiceros)). The dependence on spatial structure of species’ interaction stimulated the author to formulate reaction-diffusion models to explain the dynamics of predator-prey relationships in ecology. These models were used to predict and explain the effect of threshold populations, predator additional food and prey refuge on the general species’ dynamics. Vital parameters that model additional food to predators, prey refuge and population thresholds were given due attention in the analyses. The stability of a predator-prey model for an ecosystem faced with a prey out-flux which is analogous to and modelled as an Allee effect was investigated. The results highlight the bounds for the conversion efficiency of prey biomass to predator biomass (fertility gain) for which stability of the three species ecosystem model can be attained. Global stability analysis results showed that the prey (warthog) population density should exceed the sum of its carrying capacity and threshold value minus its equilibrium value i.e., W >(Kw + $) −W . This result shows that the warthog’s equilibrium population density is bounded above by population thresholds, i.e., W < (Kw+$). Besides showing the occurrence under parameter space of the so-called paradox of enrichment, early indicators of chaos can also be deduced. In addition, numerical results revealed stable oscillatory behaviour and stable spirals of the species as predator fertility rate, mortality rate and prey threshold were varied. The stabilising effect of prey refuge due to variations in predator fertility and proportion of prey in the refuge was studied. Formulation and analysis of a robust mathematical model for two predators having an overlapping dietary niche were also done. The Beddington-DeAngelis functional and numerical responses which are relevant in addressing the Principle of Competitive Exclusion as species interact were incorporated in the model. The stabilizing effect of additional food in relation to the relative diffusivity D, and wave number k, was investigated. Stability, dissipativity, permanence, persistence and periodicity of the model were studied using the routine and limit cycle perturbation methods. The periodic solutions (b 1 and b 3), which influence the dispersal rate (') of the interacting species, have been shown to be controlled by the wave number. For stability, and in order to overcome predator natural mortality, the nutritional value of predator additional food has been shown to be of high quality that can enhance predator fertility gain. The threshold relationships between various ecosystem parameters and the carrying capacity of the game park for the prey species were also deduced to ensure ecosystem persistence. Besides revealing irregular periodic travelling wave behaviour due to predator interference, numerical results also show oscillatory temporal dynamics resulting from additional food supplements combined with high predation rates.

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Bury, Luke Andrew Dascenzo. "Examining Dynamic Aspects of Presynaptic Terminal Formation via Live Confocal Microscopy." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1435336355.

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Lee, Jin. "How fast can we see? : the latency development in human infants to pattern, orientation, and direction-reversal visual evoked potentials." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:09c7d3e8-7031-43e4-b03a-fe2dba219ceb.

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The goal of this thesis is to track latency changes in three visual evoked potentials (VEP) stimuli as an indication of overall brain development, in order to provide a normative baseline to differentiate visual and neurological development from pathological processes. VEP- neural electrical activity recorded from the scalp surface and synchronized with visual stimulus transitions- is one of the common techniques in understanding infant vision development. Past work has concentrated on responses to pattern reversal and to the latency of the initial positive peak. Here we compare the timing of responses to pattern, orientation, and direction-reversal VEPs, and transient peak latencies to those calculated from the gradient of steady-state phase against reversal rate. The three stimuli were tested in 81 adults at 1- 16 r/s and 137 infants (3.6- 79.0 weeks) at 2- 8 r/s. Initial responses to orientation and direction were as fast as for contrast- around 100 ms, consistent with other findings that V1 is orientation selective. Cortical processing for both OR and DR yielded longer latencies (200 ms) by the calculated method, perhaps reflecting more involvement of higher visual processing in comparison to PR. Orientation and direction latencies also had a delayed onset and longer developmental period to reach maturity. Infants reached adult transient PR latency values by 15 weeks, for OR by 50 weeks, and for DR by 10 weeks. For the calculated latency, infants reached both adult PR and DR latencies by 30 weeks while OR showed little change across age. We successfully confirmed that (1) phase-based calculation of latency is effective, easy to use, and taps into a different cortical pathway; (2) motion processing has an additional, faster, subcortical pathway; (3) a parallel processing of initial contrast and orientation; and (4) later visual processing is not only developmentally delayed for all three stimuli but also more vulnerable to perinatal brain damage. These latency differences provided a baseline for clinical evaluations where identification of delayed latencies should aid early diagnosis and guide therapies for adults and infants.

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Pantazis, Periklis. "Role of endocytic trafficking during Dpp gradient formation." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2004. http://nbn-resolving.de/urn:nbn:de:swb:14-1106665288062-25959.

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Morphogens are secreted signalling molecules that are expressed in restricted groups of cells within the developing tissue. From there, they are secreted and travel throughout the target field and form concentration gradients. These concentration profiles endow receiving cells with positional information. A number of experiments in Drosophila demonstrated that the morphogen Decapentaplegic (Dpp) forms activity gradients by inducing the expression of several target genes above distinct concentration thresholds at different distances from the source. This way, Dpp contributes to developmental fates in the target field such as the Drosophila wing disc. Although the tissue distribution as well as the actual shape and size of the Dpp morphogen concentration gradient has been visualized, the cell biological mechanisms through which the morphogen forms and maintains a gradient are still a subject of debate. Two hypotheses as to the dominant mechanism of movement have been proposed that can account for Dpp spreading throughout the Drosophila wing imaginal target tissue: extracellular diffusion and planar transcytosis, i. e. endocytosis and resecretion of the ligand that is thereby transported through the cells. Here, I present data indicating that implications of a theoreticalanalysis of Dpp spreading, where Dpp transport through the target tissue is solely based on extracellular diffusion taking into account receptor binding and subsequent internalization, are inconsistent with experimental results. By performing Fluorescence Recovery After Photobleaching (FRAP) experiments, I demonstrate a key role of Dynamin-mediated endocytosis for Dpp gradient formation. In addition, I show that most of GFP-Dpp traffics through endocytic compartments at the receiving epithelial cells, probably recycled through apical recycling endosomes (ARE). Finally, a Dpp recycling assay based on subcellular photouncage of ligand is presented to address specifically the Dpp recycling event at the receiving cells.

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Pegg, Timothy Joseph. "Cell Wall Carbohydrate Modifications during Flooding-Induced Aerenchyma Formation in Fabaceae Roots." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1626443795433208.

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47

Peralta, Angela. "Generation of A L. Hesperus embryonic cDNA library for the isolation of genes involved in early pattern formation." Scholarly Commons, 2010. https://scholarlycommons.pacific.edu/uop_etds/755.

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While development in flies is well understood, pattem formation and the evolution thereof in arachnids have yet to be clarified. Flies and other metazoans primarily use two families of genes called Hox genes and Pax genes to regulate embryogenesis. Because of the high evolutionary conservation of Hox and Pax proteins, I hypothesize that arachnids also use this system to organize their body pattern. To enable studies of the Westem black widow spider, Latrodectus hesperus, an embryonic eDNA library and a fixation protocol were developed for L. hesperus embryos. The generation of these tools will allow comprehensive analysis of black widow spider development and give insight into whether, and how, spiders use Hox and Pax genes to organize their bodies. Finally, it will provide a more thorough understanding of how different developmental mechanisms have evolved and ultimately how changes in gene expression can lead to a change in overall body plan.

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Hu, Jimmy Kuang-Hsien. "Diverse Roles of Cell Signaling during Early and Late Phases of Limb Development." Thesis, Harvard University, 2011. http://dissertations.umi.com/gsas.harvard:10015.

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The development of the vertebrate limb is a progressive process characterized by initial induction and patterning, concomitant growth and morphogenesis, and subsequent cell differentiation and tissue formation. Many of these processes are regulated by specific signaling centers and the environment they create. Through both classical approaches and recent molecular studies, we are beginning to understand the roles of these signaling events during limb development. However, several questions still remain and need to be further addressed. In this dissertation, I first examine how signaling molecules regulate the proximal-distal (PD) patterning of the limb. We demonstrate that early limb mesenchyme is initially maintained in a state capable of generating all limb segments by a combination of proximal and distal signals. As the limb grows, the proximal limb is established by exposure to flank-derived signal(s), whereas the distal segments are determined by distal signals when cells grow beyond the proximal influence. Thus, these results support the “two signal model” and contradict the classical view of PD patterning by a clock-based system that was postulated in the “progress zone model”. In the second part of this work, I focus on a later developmental event and study the cell- and non-cell-autonomous function of Sonic hedgehog (Shh) during limb muscle formation. Muscle progenitor cells migrate from the lateral somites into the developing limb, where they undergo patterning and differentiation in response to local signals. We find that Shh patterns limb musculature non-cell-autonomously, acting through adjacent non-muscle mesenchyme. However, Shh functions cell-autonomously to maintain cell survival in the dermomyotome and promote slow muscle differentiation. Finally, Shh signaling is required cell-autonomously to maintain Net1 expression, which in turn regulates directional muscle cell migration in the distal limb. The dissertation ends with three appendices, describing separate studies: first, mechanisms of limb loss in snakes, second, the role of Hippo signaling in limb development, and lastly a collaborative work with Dr. Jérôme Gros on limb morphogenesis. Taken together, this dissertation provides a glimpse into the diverse roles of signaling pathways during various stages of vertebrate limb development.

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Bentaya, Souhila. "Etude de la fonction de la protéine de liaison à l'ARN XSEB4R dans la formation de l'ectoderme chez le xénope." Doctoral thesis, Universite Libre de Bruxelles, 2013. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209490.

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Une étape initiale fondamentale dans le développement des vertébrés est l'organisation des cellules de l'embryon en trois feuillets embryonnaires primordiaux: ectoderme, mésoderme et endoderme. Chez l'embryon de xénope, le développement de l'endoderme et l’induction du mésoderme est initié par le gène maternel VegT codant pour un facteur de transcription à boîte T dont l'ARNm est localisé au pôle végétatif de l'ovocyte. Actuellement, les facteurs et mécanismes impliqués dans la formation de l'ectoderme, qui reste pluripotent jusqu'à la gastrulation, sont mal connus.

Des travaux récents du laboratoire ont montré que le gène XSeb4R, codant pour une protéine de liaison à l'ARN à motif RRM, présente maternellement de manière ubiquitaire dans la blastula, interagit directement avec la région 3'UTR de l'ARNm VegT, stabilisant et stimulant sa traduction. La déplétion de XSEB4R inhibe la formation de l'endoderme et du mésoderme et sa surproduction produit l’effet inverse. Ces observations ont montré que XSeb4R joue un rôle essentiel via VegT dans la formation de l'endoderme et du mésoderme.

Dans cette étude, nous avons testé l’hypothèse selon laquelle XSeb4R jouerait également un rôle au pôle animal dans la spécification de l’ectoderme. Nos résultats montrent que la protéine XSEB4R lie les régions 3’UTR des transcrits Sox3, Zic2a et Zic2b. Nous avons observé que la surexpression de XSeb4R stabilise les transcrits maternels Sox3 et Zic2 a et b, et qu’elle active la traduction des transcrits Zic2b mais pas celle de Sox3 ou Zic2a. Enfin, nous avons montré que la perte de fonction de XSeb4R induit une expansion du mésoderme vers l’ectoderme dans l’embryon au stade blastula. Ces résultats démontrent que XSeb4R joue un rôle important dans la spécification de l’ectoderme chez l’embryon de xénope.

Doctorat en Sciences
info:eu-repo/semantics/nonPublished

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Gogia, Neha. "Drosophila Eye Model to Study Dorso-Ventral (DV) Patterning and Neurodegenerative Disorders." University of Dayton / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1572279564626749.

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Dissertations / Theses on the topic 'Developmental biology/pattern formation'

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