Showing 591 - 600 of 681 Items
Receptors and Neuropeptides in the Cardiac Ganglion of the American Lobster, Homarus americanus: A Bioinformatics and Mass Spectrometric Investigation
Date: 2019-01-01
Creator: Louis Mendez
Access: Open access
- Central pattern generators (CPGs) are neural networks that generate rhythmic motor patterns to allow organisms to perform stereotypical tasks, such as breathing, scratching, flying, and walking. The American lobster, Homarus americanus, is a simple model system whose CPGs are functionally analogous to those in vertebrate models and model complex rhythmic behaviors. CPGs in many Crustacea, including the American lobster, have been studied because of their ability to maintain biological function after isolation in physiologically relevant conditions. The cardiac ganglion (CG) is a CPG consisting of five larger motor neurons and four smaller pacemaker neurons that innervate the cardiac neuromuscular system and generate electrical bursts that drive patterned behaviors. Neuromodulators, such as neuropeptides, are known to modulate neural output in the CPGs of the American lobster. Currently, neuromodulators affecting the cardiac ganglia are thought to be mainly expressed and secreted outside of the cardiac ganglia, acting as extrinsic neuromodulators. However, there is current evidence to support the idea that neuromodulators can be intrinsically expressed within the cardiac ganglion of the American lobster. Preliminary studies using transcriptomic techniques on genomic and transcriptomic information indicate that neuropeptides are likely expressed within the cardiac ganglion. However, little research has been done to determine whether these neuropeptides are expressed in the cardiac ganglion of the American lobster. Therefore, the purpose of this study is to combine bioinformatics and mass spectrometric techniques to determine whether select neuropeptides are present in the cardiac ganglion within the cardiac neuromuscular system of the American lobster, Homarus americanus. Our data mining techniques using protein query sequences obtained from previously annotated brain and eyestalk transcriptomes resulted in the identification of 22 putative neuropeptides preprohormones from 17 neuropeptide families and 20 putative neuropeptide receptors from 17 neuropeptide receptor families in the CG transcriptome. Additionally, 9 putative neuropeptide receptors from 7 neuropeptide receptor families were detected in the cardiac muscle transcriptome. Of the 17 neuropeptide families detected, receptors for 9 of these neuropeptide families were detected in the CG transcriptome. Receptors for 6 of the neuropeptide families were also present in the cardiac muscle transcriptome. Interestingly, receptors for 6 of neuropeptide families detected were not found in either the CG or cardiac muscle transcriptomes, and receptors for 4 neuropeptide families that weren’t detected in the CG transcriptome were found in the cardiac muscle transcriptome. Therefore, our research suggests that neuropeptides are able to modulate CPG activity extrinsically, either though hormonal or local delivery, or intrinsically. Additionally, neuropeptides were extracted from the stomatogastric ganglion and the commissural ganglion using a scaled-down neuropeptide extraction protocol to estimate the number of tissues required to obtain sufficiently strong mass spectrometry signals. Pooled samples with two commissural ganglia and single samples of a commissural ganglion and a stomatogastric ganglion displayed little signal and an increase in larger peptides and impurities relative to single-tissue samples. Therefore, further optimization of the scaled-down neuropeptide extraction protocol must be done prior to analysis of a cardiac ganglion in the American lobster.
"This is N.Y.C. Not Little Rock": The Battle to Integrate New York City's Public Schools
Date: 2019-01-01
Creator: Anne Fraser Gregory
Access: Open access
- The landmark Brown vs. Board of Education decision of 1954, and its subsequent implementation, offer an essential question: Are segregated schools inherently evil, and is integration the only solution to unequal education? The statistics that illustrate the effects of segregated schooling are indeed staggering. According to a 2016 Government Accountability Office study, the number of schools segregated along racial and economic lines doubled between 2000 and 2013. In New York City, the achievement gap between Black and white students has continued to grow. In 2018, the National Assessment of Achievement Progress reported that 48 percent of white fourth-graders were proficient in math, while only 16 percent of black students met the standard. With a gap of 32 percentage points—growing 5 points since 2015—Black children in New York are consistently behind their white peers in academics. Sixty years ago, New York's Black and Latino parents parents grappled with this same issue as they fought to desegregate the city’s schools. This Honors Project will discuss segregated schooling in New York City during the 1950s and 60s, and the actors who fought to disrupt the system. Throughout this work, I will attempt to illustrate the power of community in New York City, for both good and evil, for equality and bigotry. Parents—Black, white, and Puerto Rican—function as key players in this story, as they continually fought local and state Boards to access the education they believed to be rightfully theirs and their children’s. I will also assert the notion that segregation was not solely a Southern issue: the similarities between the fight for school integration in both North and South are striking, and highlight the far reaches of prejudice in the nation both then and now. Most importantly, I argue that unequal education may not be solved by integration alone, and that believing in integration as the only viable option perpetuates the incorrect notion that children of color require proximity to white students in order to be academically successful.
The Future Regained: Toward a Modernist Ethics of Time
Date: 2020-01-01
Creator: Jack Rodgers
Access: Open access
- This project explores the convergence of futurity and ethics through an examination of key figures in modernist literature. It studies works by Virginia Woolf, Marcel Proust, and James Joyce in order to conceptualize an encounter with the future which goes beyond a traditionally linear and teleological model of time, setting out to reimagine the role of both temporality and ethics in novels including Orlando, Mrs. Dalloway, In Search of Lost Time, and Ulysses. Key facets of this exploration, which is metaphorized and guided by the image of a window, include temporal otherness, transgression and fracturing of the self (primarily understood through the paradoxical experience of dying), and the arrival of the future into the present. Major theoretical influences include queer theory, poststructuralism, and anti-dialectics. Ultimately, the project makes the case that it is possible to construct a modernist ethics which embraces the messianic potential of absences, blanks, and blind spots, a proposition made possible by our encounter with an incomprehensible yet imminent fragment of the future out of place in the present. At the close, it suggests an ethical imperative towards “affirmative negation”—a messianic, annunciatory, affirmation of that which is missing or omitted.
Differential gene expression during compensatory plasticity in the prothoracic ganglion of the cricket, Gryllus bimaculatus Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2020-01-01
Creator: Felicia F. Wang
Access: Access restricted to the Bowdoin Community
Interaction of stretch feedback and beat regularity in response to AMGSEFLamide in the heart of Homarus americanus
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.
Regulation of eyes absent gene expression in Drosophila melanogaster by Polycomb Group Response Elements 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: Boris S. Dimitrov
Access: Access restricted to the Bowdoin Community
Mémoire et souvenir dans l'imaginaire antillais - Maryse Condé et Fabienne Kanor: Identité et existence noire aux Antilles et en France
Date: 2020-01-01
Creator: Elijah B Koblan-Huberson
Access: Open access
- L’histoire d’un peuple est en grande partie liée à sa mémoire, aux souvenirs et commémorations des évènements passés et des ancêtres.En raison de la colonisation et ses conséquences, les habitants des îles de la Guadeloupe et de la Martinique vivent un malaise vis-à-vis de la mémoire en tant que peuple antillais.Par conséquent, il est important de se demander comment, après la déshumanisation effectuée par l’extermination des premiers habitants, les Caraïbes et les Arawaks, l’esclavagisation des Africains, et la colonisation des territoires antillais, une nouvelle conceptualisation de la mémoire peut mener à une nouvelle conceptualisation de l’existence et de l’identité pour l’être humain antillais qui provient de ceux qui ont été esclavagisés. Pour répondre à la question nous examinerons les romans de Maryse Condé et de Fabienne Kanor.
Enemy Combatants and Unitary Executives: Presidential Power in Theory and Practice During the War on Terror
Date: 2020-01-01
Creator: Rohini Kurup
Access: Open access
- In the wake of the September 11 attacks, the Bush administration decided that suspected terrorists and those determined to have aided terrorists would be detained and classified as “enemy combatants.” This was a largely new category of prisoners who were neither prisoners of war protected under international law nor civilians. They included noncitizens and citizens—those captured on foreign battlefields and on American soil. They would be detained by the United States, held indefinitely without charge or access to a lawyer, and subject to trial by military commission. The administration’s enemy combatant policies were based on a theory of inherent executive power—that the Constitution gave the president vast and exclusive powers, which allowed him to act unilaterally without Congressional interference or judicial review. This thesis charts the development of and challenges to the enemy combatant policies to understand how they were conceived and what their implications are to the American political system. I argue that by appealing to a theory of inherent executive power to create the policies, the administration subverted traditional checks on presidential power and undermined the rule of law. Ultimately, the dismantling of some of the enemy combatant policies, largely a result of court rulings that challenged the administration’s premise of power, signified a reining in of executive authority. Yet, many aspects of the administration’s counterterrorism apparatus remained past Bush’s years in the White House, leaving a legacy of expanded presidential power for future presidents.
Isolation of Cell Adhesion Mutations in Arabidopsis thaliana Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2020-01-01
Creator: Frances DeCamp Hobart Zorensky
Access: Access restricted to the Bowdoin Community
The role of behavioral diversity in determining the extent to which central pattern generators are modulated
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.