UMD Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/3
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.
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Item Physiological dynamics of injury and regeneration in the clonal freshwater annelid Pristina leidyi(2022) Rennolds, Corey William; Bely, Alexandra E; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The threat that mechanical injury poses to homeostasis and survival has spurred the evolution of diverse processes to mitigate these effects. The most dramatic of these is regeneration, a process that restores the form and function of lost body parts. The apparent benefits of regeneration may come at considerable cost, however, and these may substantially diminish regeneration’s adaptive value in certain contexts, potentially contributing to evolutionary losses of regeneration. The costs and benefits of regeneration are poorly understood in most animals, precluding more than speculation of the evolutionary drivers of regeneration. Naids are a group of small, clonally reproducing freshwater annelids that feature great diversity of regenerative ability and are well suited to experimental studies. I used the species Pristina leidyi to determine how injury and regeneration affect organismal function and fitness, integrating physiological and molecular approaches. I first investigated how injury and regeneration differentially affect an individual’s ability to tolerate environmental stress, an ecologically relevant and energetically demanding task. I found that stress tolerance is reduced by regeneration in a stressor- and tissue-specific manner while, unexpectedly, tolerance is temporarily improved shortly after injury. These effects are unrelated to whole-organism metabolic rate, which surprisingly does not differ between early and late injury recovery. Using 3’ TagSeq, I found that, while injury and heat stress elicit largely distinct responses, both upregulate certain shared damage control pathways. I then tested whether the physiological cost of regeneration has potential to translate into fitness costs by examining the interaction between regeneration and reproduction, which occurs by asexual fission in this species. By modulating resource availability, I found evidence for an energetic trade-off between regeneration and reproduction that is masked when food is abundant. This tradeoff is manifested through a reduction in per-offspring allocation rather than reproductive rate. Overall, my results demonstrate that injury and regeneration costs are highly context dependent in P. leidyi. More broadly, these findings contrast in key ways from evolutionarily distant animals with very different life history traits, illustrating the importance of investigating the physiological mechanisms that may mediate selection on regeneration in diverse lineages.Item How Far Does the Grid Go?(2019) Pantelis, Irene Noemi; Richardson, William C; Art; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)My artwork probes the connection between daily life and what I perceive as the larger grid out there—a mesh that entangles all peoples, beings and things, cuts across all time, and is always in flux. Drawing from my everyday life and experiences as a Latin American immigrant, I incorporate materials from my suburban home environment in my multidisciplinary approach. I create organic forms and grids that abstract, excavate, ground and find universal truths in the quotidian. They also serve as platforms for engaging obliquely with history, science, archeology, philosophy, and magic realism. My artwork invites viewers to reach interpretations based on their own associations, experiences, and feelings. It thus brings attention to the power of our imagination to infuse the material world, particularly nature, with fluid possibilities of meaning and subjectivity.Item Ruins and Wrinkles: Revaluing Age through Architecture(2014) Moore, Lucy Eleanor; Lamprakos, Michele; Architecture; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this thesis I argue that an architecture that selectively intervenes in the aging landscape to provide opportunities for regeneration and mentorship can weaken our societal divisions. I tested this hypothesis in the context of an adaptive reuse, multi-generational, mixed use design for the Bailey Power Plant, Factory 60, and their surroundings: the former R.J. Reynolds tobacco district in my hometown of Winston-Salem, North Carolina. After a close study of the site's history and its urban morphology, I propose a design based on the concept of urban regeneration in the form of reclamation, adaptation, and mentorship established through a system of green infrastructure that weaves existing neighborhoods into new diverse, multi-generational communities, housed within existing but altered architecture.Item Physical properties of lamprey spinal cord regeneration: adaptive vs. maladaptive recovery(2014) Luna Lopez, Carlos; Aranda-Espinoza, Helim J.; Bioengineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Spinal cord injury (SCI) is a physical trauma that can result in paralysis and even death; to date no treatment exists that can successfully promote functional or adaptive recovery. Although humans are unable to regenerate after complete SCI, there are animal models that have been studied for their ability to regrow and reconnect their nerve fibers. From the group of animals that are capable of spinal cord regeneration, in the best studied is the lamprey (Petromyzon Marinus) it has been noted that recovery can be maladaptive. When left to recover at warm temperature (23 ⁰C) most lampreys had adaptive behavior, but at cold temperature (10 ⁰C) most lampreys showed maladaptive behavior. In this thesis we studied the physical factors that influence adaptive and maladaptive recovery in lampreys. In the first part, we analyzed axonal regeneration and blood clot formation at early time points after injury (1-2 weeks). We found that lampreys in cold temperature have a blood clot that could be blocking spinal cord regeneration. In the second part of this work, we analyzed the biomechanical and structural differences between lampreys in warm and cold temperature. We used in vivo X-ray imaging and tensile loading testing of the spinal cord and notochord structures, before and after injury. We found that lampreys at warm temperature are more favorable to create a permissive mechanical and structural environment for regeneration. Lastly, we used those lessons learned previously to enhance regeneration of maladaptive animals. We removed the blood clot at the injury site and created a time frequency analysis to measure the recovery of coordination. We found that lampreys in cold temperature with clot removal had a more adaptive recovery after injury than those without removal. In summary, by using the lamprey we were able to compare the differences between regeneration in warm and cold temperature and found the physical factors that influence maladaptive recovery. Removing one of these factors, in this case the blood clot, successfully enhanced the recovery of coordination. These results have the potential to be translated to higher animals and aid in the creation of successful treatments for SCI.Item Regeneration, Fission and the Evolution of Developmental Novelty in Naid Annelids(2012) Zattara, Eduardo Enrique; Bely, Alexandra E; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Regeneration of lost structures and asexual reproduction by fission are post-embryonic trajectories related at the evolutionary and developmental levels. Their phylogenetic distribution within Metazoa has led to the hypothesis that fission can evolve by co-opting regenerative abilities. Fission has evolved multiple times within Annelida, including independent origins at the base of the Pristininae and Naidinae lineages of naid worms. Naids are thus a great system to study the evolution of developmental trajectories of regeneration and fission and their mutual physiological interactions. I made a comparative study of morphogenesis during regeneration and fission in a representative species, Pristina leidyi Smith (Pristininae), to test the hypothesis that both trajectories are closely linked by common origin, yet have undergone functional divergence; results show that regeneration and fission share numerous, sometimes exclusive developmental processes, but also present a number of differences spread out along their trajectories. I also examined cell proliferation and growth patterns in P. leidyi to characterize the resource allocation strategies it uses to integrate multiple developmental trajectories. I found evidence for a non-linear antero-posterior gradient in proliferation potential and clear interactions between regeneration and fission that strongly depend on fission stage and what body part is lost; similar interactions have been described for naidine annelids and turbellarian flatworms representing independent origins of fission, indicating convergence of fission-associated allocation strategies. I then extended the fission-regeneration comparative study in P. leidyi to additional annelids, describing and comparing regeneration and fission in another pristinine, seven naidine and one outgroup species, and found very similar regeneration trajectories among all of them, along with striking levels of convergence of paratomic fission trajectories. Despite similarities, the two paratomic clades presented a distinctive mode of central nervous system development. Finally, I developed novel protocols for dynamic studies of the cellular basis of regeneration, laying groundwork for future comparisons at that level. Altogether, these results strongly support that fission originated multiple times by co-option of regenerative abilities; furthermore, convergence of fission trajectories and resource allocation strategies suggests that similar developmental capabilities, functional constraints and ecophysiological contexts can channel evolutionary trajectories into parallel paths, both in close and distant lineages.Item IDENTIFICATION OF THE MOLECULAR MECHANISMS OF ZEBRAFISH INNER EAR HAIR CELL REGENERATION USING HIGHTHROUGHPUT GENE EXPRESSION PROFILING(2010) Liang, Jin; Popper, Arthur N.; Neuroscience and Cognitive Science; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)All nonmammalian vertebrates studied can regenerate inner ear mechanosensory receptors, i.e. hair cells, but mammals only possess a very limited capacity for regeneration after birth. As a result, mammals suffer from permanent deficiencies in hearing and balance once their inner ear hair cells are lost. The mechanisms of hair cell regeneration are poorly understood. Because the inner ear sensory epithelium is highly conserved in all vertebrates, we chose to study the hair cell regeneration mechanism in adult zebrafish, hoping the results would be transferrable to inducing hair cell regeneration in mammals. We defined the comprehensive network of genes involved in hair cell regeneration in the inner ear of adult zebrafish with the powerful transcriptional profiling technique, Digital Gene Expression (DGE), which leverages the power of next-generation sequencing. We also identified a key pathway, stat3/socs3, and demonstrated its role in promoting hair cell regeneration through stem cell activation, cell division, and differentiation. In addition, transient pharmacological up-regulation of stat3 signaling accelerated hair cell regeneration without over-producing cells. Taking other published datasets into account, we propose that the stat3/socs3 pathway is a key response in all tissue regeneration and thus an important therapeutic target not only for hair cell regeneration, but also for a much broader application in tissue repair and injury healing. The dissertation contains four supplemental files. Supplemental file 1 contains raw data of five expression profiles generated by DGE. It is a tab-delimited text file with six columns. The first column contains the sequences of the tags and the second to sixth columns contain the count of the corresponding tags in control, 0-hpe, 24-hpe, 48-hpe, and 96-hpe profiles respectively. Supplemental file 2 contains UniGene clusters identified from unambiguously mapped tags. It is a tab-delimited text file with six columns. The first column contains the UniGene IDs. The second to sixth columns contain the count of the corresponding UniGene clusters in control, 0-hpe, 24-hpe, 48-hpe, and 96-hpe profiles respectively. Supplemental file 3 contains candidate genes identified by comparison of the expression profiles during regeneration to the control profiles. It is a tab-delimited text file with 19 columns. The contents in each column are specified in the header. Supplemental file 4 contains a list of the candidate genes known to be expressed in the inner ear and/or the lateral line system during development. It is a tab-delimited text file with four columns which contain UniGene IDs, ZFIN IDs, Entrez Gene IDs, and gene symbols respectively.Item MANAGEMENT MATTER? EFFECTS OF CHARCOAL PRODUCTION MANAGEMENT ON WOODLAND REGENERATION IN SENEGAL(2010) Wurster, Karl; Defries, Ruth; Geography; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In Senegal, as in many parts of Africa, nearly 95% of its growing urban population depends on charcoal as their primary cooking energy. Extraction of wood for charcoal production is perceived to drive forest degradation. The Senegalese government and international donor agencies have created different forest management types with the ultimate goal of sustainably managing forests. This research combines local ecological knowledge, ecological surveys and remote sensing analysis to better understand questions related to how extraction for charcoal production and forest management affect Senegalese forests. Information derived from 36 semi-structured interviews suggests that the forests are degrading, but are depended on for income, grazing and energy. Interviewees understand the rules governing forest management types, but felt they had limited power or responsibility to enforce forest regulations. Ecological survey results confirmed that plots harvested for charcoal production are significantly different in forest structure and tree species composition than undisturbed sites. Across harvested and undisturbed and within forest management types the Combretum glutinosum species dominated (53% of all individuals and the primary species used for charcoal production) and demonstrated robust regenerative capacity. Few large, hardwood or fruiting trees were observed and had insufficient regenerative capacity to replace current populations. Species diversity was higher in co-managed areas, but declined after wood was harvested for charcoal production. Proximity to villages, roads and park edges in harvested and undisturbed plots and within forest management types had little impact on forest structure and tree diversity patterns with the harvesting of trees for charcoal spread consistently throughout the landscape. Remote sensing analysis with the MISR derived k(red) parameter demonstrated its ability to accurately classify broad land classes and showed potential when differentiating between pre- and post-harvest conditions over a three year time period, but could not accurately detect subtle changes in forest cover of known harvest time since last harvest in a single MISR scene. This research demonstrated the utility of multidisciplinary research in assessing the effects of charcoal production and forest management types on Senegalese forests; concluding that the effects of charcoal production on forest characteristics and regenerative capacity are consistent throughout all forest management types.