Showing 5431 - 5440 of 5831 Items
Effects of Arabidopsis wall associated kinase mutations on ESMERALDA1 and elicitor induced ROS
Date: 2021-05-01
Creator: Bruce D. Kohorn, Bridgid E. Greed, Gregory Mouille, Stéphane Verger, Susan L., Kohorn
Access: Open access
- Angiosperm cell adhesion is dependent on interactions between pectin polysaccharides which make up a significant portion of the plant cell wall. Cell adhesion in Arabidopsis may also be regulated through a pectin-related signaling cascade mediated by a putative O-fucosyltransferase ESMERALDA1 (ESMD1), and the Epidermal Growth Factor (EGF) domains of the pectin binding Wall associated Kinases (WAKs) are a primary candidate substrate for ESMD1 activity. Genetic interactions between WAKs and ESMD1 were examined using a dominant hyperactive allele of WAK2, WAK2cTAP, and a mutant of the putative O-fucosyltransferase ESMD1. WAK2cTAP expression results in a dwarf phenotype and activation of the stress response and reactive oxygen species (ROS) production, while esmd1 is a suppressor of a pectin deficiency induced loss of adhesion. Here we find that esmd1 suppresses the WAK2cTAP dwarf and stress response phenotype, including ROS accumulation and gene expression. Additional analysis suggests that mutations of the potential WAK EGF O-fucosylation site also abate the WAK2cTAP phenotype, yet only evidence for an N-linked but not O-linked sugar addition can be found. Moreover, a WAK locus deletion allele has no effect on the ability of esmd1 to suppress an adhesion deficiency, indicating WAKs and their modification are not a required component of the potential ESMD1 signaling mechanism involved in the control of cell adhesion. The WAK locus deletion does however affect the induction of ROS but not the transcriptional response induced by the elicitors Flagellin, Chitin and oligogalacturonides (OGs).
A "Peculiarly American" Enthusiasm: George Bellows, Traditional Masculinity, and The Big Dory
Date: 2014-01-01
Creator: James W. Denison, IV
Access: Open access
- A “Peculiarly American” Enthusiasm: George Bellows, Traditional Masculinity, and The Big Dory investigates the portrayal of masculinity in the oeuvre of the much-lauded yet enigmatic American painter George Bellows (1882-1925). Rather than relying on Bellows’ urban works for source material, a significant portion of this investigation is conducted via a case study of Bellows’ 1913 panel The Big Dory, a scene of fishermen pushing a boat into the North Atlantic off Monhegan Island, Maine that the artist painted during a sojourn on the island in the months after his involvement in the landmark Armory Show in New York. The paper situates The Big Dory within the greater context of the history of the depiction of Maine through the lens of the heroic fisherman. Bellows achieved a heroic effect by forcing the viewer to focus on the labor of the fishermen via their positioning in the near middleground and by echoing the hues and forms of the men elsewhere in the painting, giving the work a sense of visual unity. I argue that these strategies highlight Bellows’ interest in tradition rather than modernism. Armed with this knowledge, Bellows’ other works come more sharply into focus. I reveal that the traditional heterosexual mode of white male identity Bellows represented in The Big Dory was not simply echoed in Bellows’ personal comportment, but in fact pervaded his oeuvre; such masculinity was a reaction by patriarchal American society against the perceived growth of other influences in the early twentieth century. The portrayal of such masculinity is then established as the key underlying feature of the sense of “Americanism” which has traditionally dominated reception of Bellows’ art.
Parterre: An Installation by Lauren Fensterstock
Date: 2008-01-01
Creator: Alison Ferris
Access: Open access
- Catalog of an exhibition held at the Bowdoin College Museum of Art from Oct. 3, 2008 through Jan.11, 2009. Essay by Alison Ferris.
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.
Forces generated during stretch in the heart of the lobster Homarus americanus are anisotropic and are altered by neuromodulators
Date: 2016-01-01
Creator: E. S. Dickinson, A. S. Johnson, O. Ellers, P. S. Dickinson
Access: Open access
- Mechanical and neurophysiological anisotropies mediate three-dimensional responses of the heart of Homarus americanus. Although hearts in vivo are loaded multi-axially by pressure, studies of invertebrate cardiac function typically use uniaxial tests. To generate whole-heart length-tension curves, stretch pyramids at constant lengthening and shortening rates were imposed uniaxially and biaxially along longitudinal and transverse axes of the beating whole heart. To determine whether neuropeptides that are known to modulate cardiac activity in H. americanus affect the active or passive components of these length-tension curves, we also performed these tests in the presence of SGRNFLRFamide (SGRN) and GYSNRNYLRFamide (GYS). In uniaxial and biaxial tests, both passive and active forces increased with stretch along both measurement axes. The increase in passive forces was anisotropic, with greater increases along the longitudinal axis. Passive forces showed hysteresis and active forces were higher during lengthening than shortening phases of the stretch pyramid. Active forces at a given length were increased by both neuropeptides. To exert these effects, neuropeptides might have acted indirectly on the muscle via their effects on the cardiac ganglion, directly on the neuromuscular junction, or directly on the muscles. Because increases in response to stretch were also seen in stimulated motor nerve-muscle preparations, at least some of the effects of the peptides are likely peripheral. Taken together, these findings suggest that flexibility in rhythmic cardiac contractions results from the amplified effects of neuropeptides interacting with the length-tension characteristics of the heart.
Elizabeth Peak: Prints and Drawings
Date: 1982-01-01
Access: Open access
- Exhibition held March 18-April 25, 1982 at Bowdoin College Museum of Art. Catalog by Alan Shestack.
"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.
A super MHV vertex expansion for n=4 SYM theory
Date: 2009-07-06
Creator: Michael Kiermaier, Stephen G. Naculich
Access: Open access
- We present a supersymmetric generalization of the MHV vertex expansion for all tree amplitudes in = 4 SYM theory. In addition to the choice of a reference spinor, this super MHV vertex expansion also depends on four reference Grassmann parameters. We demonstrate that a significant fraction of diagrams in the expansion vanishes for a judicious choice of these Grassmann parameters, which simplifies the computation of amplitudes. Even pure-gluon amplitudes require fewer diagrams than in the ordinary MHV vertex expansion. We show that the super MHV vertex expansion arises from the recursion relation associated with a holomorphic all-line supershift. This is a supersymmetric generalization of the holomorphic all-line shift recently introduced in arXiv:0811.3624. We study the large-z behavior of generating functions under these all-line supershifts, and find that they generically provide 1/z k falloff at (Next-to) kMHV level. In the case of anti-MHV generating functions, we find that a careful choice of shift parameters guarantees a stronger 1/z k+4 falloff. These particular all-line supershifts may therefore play an important role in extending the super MHV vertex expansion to = 8 supergravity. © SISSA 2009.