4,056 research outputs found

    Quantitative Analysis of Hedgehog Gradient Formation Using an Inducible Expression System: a Dissertation

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    The Hedgehog (Hh) family of proteins are secreted growth factors that play an essential role in the embryonic development of all organisms and the main components in the pathway are conserved from insects to humans. These proteins affect patterning and morphogenesis of multiple tissues. Therefore, mutations in the Hh pathway can result in a wide range of developmental defects and oncogenic diseases. Because the main components in the pathway are conserved from insects to humans, Drosophilahas been shown to provide a genetically tractable system to gain insight into the processes that Hh is involved in. In this study, the roles of Hh cholesterol modification and endocytosis during gradient fonnation are explored in the Drosophila larval wing imaginal disc. To exclude the possibility of looking at a redistribution of preexisting Hh instead of Hh movement, a spatially and temporally regulated system has been developed to induce Hh expression. Functional Hh-GFP with and without the cholesterol-modification was expressed in a wild-type or shi-tslendocytosis mutant background. The Gal80 system was used to temporally express (pulse) the Hh-GFP transgenes to look at the rate of Hh gradient formation over time and determine whether this process was affected by cholesterol modification and/or endocytosis. Hh with and without cholesterol were both largely detected in punctate structures and the spreading of the different forms of Hh was quantified by measuring distances of these particles from the expressing cells. Hh without cholesterol showed a greater range of distribution, but a lower percentage of particles near the source. Loss of endocytosis blocked formation of intracellular Hh particles, but did not dramatically alter its movement to target cells. Staining for Hh, its receptor Ptc and cortical actin revealed that these punctate structures could be classified into four types of Hh containing particles: cytoplasmic with and without Ptc, and cell surface with and without Ptc. Cholesterol is specifically required for the formation of cytoplasmic particles lacking Ptc. While previous studies have shown discrepancies in the localization of Hh following a block in endocytosis, Hh with and without cholesterol is detected at both apical and basolateral surfaces, but not at basal surfaces. In the absence of cholesterol and endocytosis, Hh particles can be observed in the extracellular space. Through three-dimensional reconstruction and quantitative analysis, this study concludes that the cholesterol modification is required to restrict Hh movement. In addition, the cholesterol modification promotes Ptc-independent internalization. This study also observes that Dynamin-dependent endocytosis is necessary for internalization but does not play an essential role in Hh distribution. The data in this thesis supports the model in which Hh movement occurs via planar diffusion

    Georgia Library Association - Coastal Georgia Library Collaborative

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    The Coastal Georgia Library Collaborative celebrated the end of a successful year with a Holiday Hoopla at the Learning Commons on the Armstrong campus of Georgia Southern University. Brenda Poku became our chair and Nikki Cannon-Rech was selected as the vice-chair

    LingitX Haa Sateeyi, We Who Are Tlingit: Contemporary Tlingit Identity And The Ancestral Relationship To The Landscape

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    Thesis (Ph.D.) University of Alaska Fairbanks, 2008Divergent views on the Tlingit ancestral relationship to the landscape of Southeast Alaska often leads to conflicts between Western-orientated government agencies, public entities, and the Tlingit people themselves. To better understand this subject, I collected nine personal narratives from research participants from within the Tlingit nation. The narratives provide insight into the dynamics at the intersection of conflicting worldviews, and the role this plays in shaping contemporary Tlingit identity. The results of exploring these diverging worldviews has illuminated three factors influencing contemporary Tlingit identity: the loss and struggle with maintaining the Lingit language, implementation of subsistence regulations and resultant conflicts, and diminishment of the ceremony called a koo.eex' (a memorial party). In addition, within the Tlingit worldviews there are oral histories, traditional values, and concepts such as balance, respect, and at.oow, which define ancestral relationships and identity. These findings also reveal that the means of imparting cultural knowledge and worldviews have changed. The narratives are organized into themes reflecting common factors: Residing in the ancestral landscape, Lingit language and thinking, the Tlingit artist and the ancestral relationship to the landscape, and contemporary Tlingit identity. The results demonstrate the significance of identity markers, such as the Lingit language, as a means for healing social trauma. Moreover, the lives of the Tlingit artists illustrate that maintaining an ancestral relationship utilizes both traditional and contemporary methods. In addition, the narratives provide documentation concerning the changes in a subsistence lifestyle that affect the social lives of the Tlingit in contemporary society

    New dispatching paradigm in power systems including EV charging stations and dispersed generation: A real test case

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    Electric Vehicles (EVs) are becoming one of the main answers to the decarbonization of the transport sector and Renewable Energy Sources (RES) to the decarbonization of the electricity production sector. Nevertheless, their impact on the electric grids cannot be neglected. New paradigms for the management of the grids where they are connected, which are typically distribution grids in Medium Voltage (MV) and Low Voltage (LV), are necessary. A reform of dispatching rules, including the management of distribution grids and the resources there connected, is in progress in Europe. In this paper, a new paradigm linked to the design of reform is proposed and then tested, in reference to a real distribution grid, operated by the main Italian Distribution System Operator (DSO), e-distribuzione. First, in reference to suitable future scenarios of spread of RES-based power plants and EVs charging stations (EVCS), using Power Flow (PF) models, a check of the operation of the distribution grid, in reference to the usual rules of management, is made. Second, a new dispatching model, involving DSO and the resources connected to its grids, is tested, using an Optimal Power Flow (OPF) algorithm. Results show that the new paradigm of dispatching can effectively be useful for preventing some operation problems of the distribution grids
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