Showing 171 - 180 of 583 Items
Determining the sites at which neuromodulators exert peripheral effects in the cardiac neuromuscular system of the American Lobster, Homarus americanus
Date: 2021-01-01
Creator: Audrey Elizabeth Jordan
Access: Open access
- Networks of neurons known as central pattern generators (CPGs) generate rhythmic patterns of output to drive behaviors like locomotion. CPGs are relatively fixed networks that produce consistent patterns in the absence of other inputs. The heart contractions of the Homarus americanus are neurogenic and controlled by the CPG known as the cardiac ganglion. Neuromodulators can enable flexibility in CPG motor output, and also on muscle contractions by acting on the neuromuscular junction and the muscle itself. A tissue-specific transcriptome gleaned from the cardiac ganglion and cardiac muscle of the American lobster was used to predict the sites and sources of a variety of crustacean neuromodulators. If corresponding receptors were predicted to be expressed in the cardiac muscle, then it was hypothesized that the neuropeptide had peripheral effects. One peptide for which a cardiac muscle receptor was identified is myosuppressin. Myosuppressin has been shown to have modulatory effects at the cardiac neuromuscular system of the American lobster. In previous research, myosuppressin had modulatory effects on the periphery of cardiac neuromuscular system alone. It remains an open question of whether myosuppressin acts on the cardiac muscle directly, if it is exerting its effects at the neuromuscular junction (NMJ), or both. To test this, I performed physiological experiments on the isolated NMJ. Myosuppressin did not modulate the amplitude of the excitatory junction potentials. Since no modulatory effects were seen at the NMJ, the cardiac muscle was isolated from the cardiac ganglion and then glutamate-evoked contractions were stimulated. I showed that myosuppressin increased glutamate-evoked contraction amplitude. These data suggest myosuppressin exerts its peripheral effects at the cardiac muscle and not the NMJ.
Los trucos debajo de la mesa: Juegos y simulacros en la cultura y literatura argentina Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2025-06-01
Date: 2020-01-01
Creator: Eliana Miller
Access: Access restricted to the Bowdoin Community
Investigating the Effect of Side Chains with Hydrogen Bonding Capabilities on Peptoid Catalysts for Enantioselective Trifluoromethylation of 4-Chlorobenzaldehyde Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2025-06-01
Date: 2020-01-01
Creator: Rebecca Londoner
Access: Access restricted to the Bowdoin Community
Characterization of O-Linked Glycosylated Neuropeptides in the American Lobster (Homarus americanus): The Use of Peptide Labeling Following Beta Elimination
Date: 2020-01-01
Creator: Edward Myron Bull
Access: Open access
- Neuropeptides are a class of small peptides that govern various neurological functions, and the American lobster (Homarus americanus) provides a model system for their characterization. Neuropeptides are commonly post-translationally modified (PTM), and one common PTM is glycosylation. Past research in the Stemmler lab has found glycosylated neuropeptides in H. americanus; however, the extent and biological role of this modification has not been well characterized. This study was undertaken to determine the number of glycosylated peptides in the sinus glands of H. americanus and to develop an approach to tag the site of glycosylation using beta-elimination chemistry. LC-MS paired with high pH reverse phase fractionation was used to survey for glycosylated neuropeptides and beta elimination with an amine tag was used as an approach to characterize the site of glycosylation. Our results indicate that high pH fractionation is a useful approach to simplify complex mixtures of neuropeptides and improve glycopeptide detection. Efforts to use beta elimination and tagging to characterize glycosylated neuropeptides have been less successful. Beta elimination of full length peptides resulted in peptide degradation. An approach utilizing chymotrypsin to reduce peptide size coupled with beta elimination and labeling with 2-dimethylaminoethanethiol showed less evidence for degradation, and this approach yielded data isolating two potential serine residues for the site of glycosylation; however, the data was not sufficient to distinguish the two sites. Work to optimize reaction conditions using a glycopeptide standard showed that multiple isomeric products were formed during beta elimination. With the goal of optimizing reaction conditions, future work will further examine reaction kinetics to eventually apply the approach to the entire sinus gland
Classifying Flow-kick Equilibria: Reactivity and Transient Behavior in the Variational Equation
Date: 2020-01-01
Creator: Alanna Haslam
Access: Open access
- In light of concerns about climate change, there is interest in how sustainable management can maintain the resilience of ecosystems. We use flow-kick dynamical systems to model ecosystems subject to a constant kick occurring every τ time units. We classify the stability of flow-kick equilibria to determine which management strategies result in desirable long-term characteristics. To classify the stability of a flow-kick equilibrium, we classify the linearization of the time-τ map given by the time-τ map of the variational equation about the equilibrium trajectory. Since the variational equation is a non-autonomous linear differential equation, we conjecture that the asymptotic stability classification of each instantaneous local linearization along the equilibrium trajectory indicates the stability of the variational time-τ map. In Chapter 3, we prove this conjecture holds when all of the asymptotic and transient behavior of the instantaneous local linearizations is the same. To explore whether the conjecture holds in general, we ask: To what degree can transient behavior differ from asymptotic behavior? Under what conditions can this transient behavior accumulate asymptotically? In Chapter 4, we develop the radial and tangential velocity framework to characterize transient behavior in autonomous linear systems. In Chapter 5, we use this framework to construct an example of a non-autonomous linear system whose time-τ map has asymptotic behavior that differs from the asymptotic behavior of each instantaneous linear system that composes it. Future work seeks to determine whether this constructed example can arise as a variational equation, and thus provide a counterexample for our conjecture.
Reading & Teaching Chaucer: the "Good Wif"?
Date: 2020-01-01
Creator: Sophie Friedman
Access: Open access
- This two-chapter project applies formalist and feminist thinking to the thirty-line description of the Wife of Bath in Geoffrey Chaucer’s medieval, British work The Canterbury Tales. It is an interdisciplinary project; it studies how to read and teach Chaucer at the secondary level based off of these two approaches. In this formalist chapter, I study narrative voice, rhyme, irony, and ekphrasis, writing about the history and function of each of those tools and their role in the passage. I argue that the formalist close reading approach is an excellent teaching tool that generates thorough, rigorous, and joyful reading. In this feminist chapter, I compile a critical literary history of scholarly feminist and pre-feminist engagement with the passage over time. I read into an underlying genotype text, arguing that the Wife of Bath was a female entrepreneur who used textiles as a means of social, professional, and aesthetic expression and empowerment. Then I advocate for a feminist ethical teaching approach—one where we use the text as a non-ethical space in which to explore ethical questions surrounding gender. Ultimately, I argue that feminist and formalist approaches are interdependent and complementary; for both reading and teaching Chaucer, they stand stronger together.
A Stepping-Stone? An Analysis of How the Minimum Wage Impacts the Wage Growth of Individuals in Monopsonistic Industries
Date: 2022-01-01
Creator: Levi McAtee
Access: Open access
- Do minimum wage increases serve as stepping-stones to higher-paying jobs for low-pay workers? This paper analyzes the impact of state minimum wage policy on the one-year wage growth rates of individuals across the wage distribution and whether that impact changes for individuals in highly monopsonistic industries. I review the recent literature on the disemployment effect, the impact of the minimum wage on wage growth rates, the nature of monopsonistic industries, and the relationship between the minimum wage and monopsony power. I offer theoretical reasons why the minimum wage may impact the wage growth rates of individuals in monopsonistic industries differently than it impacts those of individuals in competitive industries. I then re-estimate Lopresti’s and Mumford’s (2016) panel fixed effects model to determine how the effect of a minimum wage increase depends nonlinearly on the size of the increase. Using data from 2005-2008, Lopresti and Mumford found that small minimum wage increases have a significant negative impact on wage growth rates, while large minimum wage increases have a significant positive impact. Using data from 2016-2019, I find similar results. As my primary empirical contribution, I test whether individuals in highly monopsonistic industries experience minimum wage changes differently than individuals in more competitive industries. I find monopsony power in the form of high labor immobility primarily impacts the wage growth rates of high-pay workers and does not influence how low-pay workers experience minimum wage changes. Finally, I recommend policymakers impose larger minimum wage increases to avoid impeding the wage-growth of low-pay workers.
The Structure and Unitary Representations of SU(2,1)
Date: 2015-05-01
Creator: Andrew J Pryhuber
Access: Open access
Guarding Whiteness: Disability, Eugenics, and Rhetorical Agency in Southern Renaissance Fiction
Date: 2023-01-01
Creator: Philip Carl Bonanno
Access: Open access
- This project explores fiction from white authors in the Southern Renaissance, specifically William Faulkner, Flannery O’Connor, and Carson McCullers. By examining their work alongside some of the performers that appeared historically in freak shows of the South, chapter one investigates how physically enfreaked individuals (usually phenotypically white) have access to power and the powers of whiteness. Chapter 2 interrogates how the South pathologizes promiscuity as mental illness with words such as moronic or feeble-mindedness, and the ramifications it has for the stratification on class divides among Southern elites and “White Trash.” The chapter seeks to answer the question of why, for a short period in the 1940s, white women were more likely to be punished with forced sterilization than Black women. Chapter 3 uncovers the rhetorical agency used by Benjy in Faulkner’s The Sound and the Fury, looking at how he resists the powers of whiteness through crip time and his trauma responses to his family that seeks to reinsert the Antebellum South. Using an intersectional approach of critical whiteness studies, disability studies, crip theory, and queer theory, relies on a variety of scholars including, but not limited to; David Mitchell and Sharon Snyder, Rosemarie Garland-Thompson, Richard Dyer, Matt Wray, Jasbir Puar, Ellen Samuels, and Allison Kafer. The primary works examined include promotional materials of historical freaks, McCullers’ The Ballad of a Sad Café, William Faulkner’s The Hamlet and The Sound and the Fury, and Flannery O’Connor short stories “Good Country People” and “A Temple of the Holy Ghost.”
Parole lievitanti: La panificazione spirituale di S. Caterina di Bologna This record is embargoed.
- Embargo End Date: 2027-05-19
Date: 2022-01-01
Creator: Katherine Aiello McKee
Access: Embargoed