Honors Projects
Showing 501 - 510 of 564 Items
Date: 2020-01-01
Creator: William Allen
Access: Open access
- Central pattern generators (CPGs) are neural circuits whose component neurons possess intrinsic properties and synaptic connections that allow them to generate rhythmic motor outputs in the absence of descending inputs. The cardiac ganglion (CG) is a nine-cell CPG located in the American lobster, Homarus americanus. Stretch of the myocardium feeds back to the CG through mechano-sensitive dendrites and is thought to play a role in maintaining regularity in the beating pattern of the heart. The novel peptide AMGSEFLamide has been observed to induce irregular beating patterns when applied at high concentrations. This study investigated the interaction between stretch-related feedback and AMGSEFLamide modulation in generating irregular beating patterns in the whole heart of Homarus americanus. It was hypothesized that greater longitudinal stretch of the heart would result in greater regularity in the instantaneous beat frequency, based on previous findings that stretch-sensitive dendrites play a role in the regulation of the heartbeat. Furthermore, it was predicted that the elimination of stretch feedback via deafferentation of the heart would augment the irregularity induced by AMGSEFLamide. Data showed significantly increased irregularity in beating in response to 10-6 M AMGSEFLamide application. Longitudinal stretch did not reliably alter baseline variability in frequency, nor did it influence the modulatory effect of AMGSEFLamide. Deafferentation did not significantly alter baseline irregularity. Deafferented preparations did exhibit a trend of responding to AMGSEFLamide with a greater percent increase in irregularity compared to when afferents were intact, suggesting a potential role of stretch-stabilization in response to modulatory perturbations in the Homarus heart.
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Date: 2020-01-01
Creator: Frances DeCamp Hobart Zorensky
Access: Access restricted to the Bowdoin Community
Date: 2020-01-01
Creator: Jacob Salman Kazmi
Access: Open access
- Neuromodulation may be a substrate for the evolution of behavioral diversity. The extent to which a central pattern generator is modulated could serve as a mechanism that enables variability in motor output dependent on an organism’s need for behavioral flexibility. The pyloric circuit, a central pattern generator in the crustacean stomatogastric nervous system (STNS), stimulates contractions of foregut muscles in digestion. Since neuromodulation enables variation in the movements of pyloric muscles, more diverse feeding patterns should be correlated with a higher degree of STNS neuromodulation. Previous data have shown that Cancer borealis, an opportunistic feeder, is sensitive to a wider array of neuromodulators than Pugettia producta, a specialist feeder. The observed difference in modulatory capacity may be coincidental since these species are separated by phylogeny. We predict that the difference in modulatory capacity is a product of a differential need for variety in foregut muscle movements. This study examined two members of the same superfamily as P. producta, the opportunistically feeding snow crab (Chionoecetes opilio) and portly spider crab (Libinia emarginata). Using extracellular recording methods, the responses of isolated STNS preparations to various neuromodulators were measured. Initial qualitative results indicate that the STNS of C. opilio is sensitive to all of these neuromodulators. Additionally, previous data on the neuromodulatory capacity of L. emarginata was supported through similar electrophysiological analysis of the isolated STNS. As a first step in determining the mechanism of differential sensitivity between species, tissue-specific transcriptomes were generated and mined for neuromodulators.
Date: 2023-01-01
Creator: Patrick Rochford
Access: Open access
- In the decades following World War II, mass suburbanization remade the American landscape. While suburbs accounted for 83% of the nation’s growth between 1950 and 1970, cities bled their populations and natural resources dwindled. Treating the postwar era as a critical juncture, this thesis examines the political history of twentieth-century state land use policy to illuminate how competing interests have shaped policy outcomes across the United States. Specifically, the paper seeks to explain the passage of statewide growth management and smart growth programs. After providing a history of American suburbanization, the paper considers an emergent challenge to the postwar growth paradigm as manifested through resistance to urban renewal, open space loss, and diverse anti-freeway coalitions that combined actors from each movement. Thereafter, I detail the development of statewide growth management and smart growth programs before employing a set of case studies to discern causal factors associated with the success or failure of such legislation. Testing the theory that broad-based coalitions were essential to the passage of state growth management legislation, I perform a controlled comparison of two pairs of states, Maryland and Virginia and Oregon and Washington, employing additional within-case analysis for Washington. In so doing, I find evidence that diverse coalitions—from environmentalists and housing advocates to farmers and historic preservationists—were essential to the passage of state growth management programs. I conclude by considering the implications of these findings and the relevance of state land use policy to contemporary issues such as affordable housing and climate change.
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- Restriction End Date: 2028-06-01
Date: 2023-01-01
Creator: Christoph Anders Tatgenhorst
Access: Access restricted to the Bowdoin Community
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- Embargo End Date: 2028-05-18
Date: 2023-01-01
Creator: Eliana Roberts
Access: Embargoed
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Date: 2024-01-01
Creator: Zackery D. Reynolds
Access: Access restricted to the Bowdoin Community
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- Restriction End Date: 2025-06-01
Date: 2024-01-01
Creator: Aditya S Pall-Pareek
Access: Access restricted to the Bowdoin Community
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- Embargo End Date: 2027-05-16
Date: 2024-01-01
Creator: Tess Davis
Access: Embargoed
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Date: 2016-01-01
Creator: Emily M King
Access: Access restricted to the Bowdoin Community