Showing 331 - 340 of 2039 Items
American Paintings of the 19th and 20th Centuries: From the Collection of Mr. and Mrs. Norman B. Woolworth
Date: 1961-01-01
Access: Open access
- Catalogue of an exhibition held Jan. 29-Feb. 28, 1961 at the Bowdoin College Museum of Art, Brunswick, Maine.
Interview with Jenna Burton (Class of 1994) by Emma Kellogg
Date: 2019-05-31
Creator: Jenna Burton
Access: Open access
- Jenna Burton (Class of 1994) describes the process of making friends through Hyde Hall and the sailing team. She also speaks about her experience being part of the Kappa Sigma fraternity and becoming its first female president. Burton reminisces about the hurdles and triumphs of starting the women’s rugby team and discusses the camaraderie and support she found within the team. Additionally, Burton talks about her on-campus job as a Resident Assistant, her Biology major, and reflects on working with Safe Space to critically examine the College’s sexual harassment policy. Finally, she touches on some of her favorite memories, like long brunches in Thorne Dining Hall and broom hockey on the quad.
GIS analysis of historical cod fisheries in the Gulf of Maine
Date: 2014-08-01
Creator: Nora Hefner
Access: Open access
- Gulf of Maine cod fisheries, once essential to Maine’s economy and culture, are currently in a state of collapse. Following a long decline throughout the 1800s and two collapses in the 1900s – one in the middle of the century and one in the 1990s, cod populations along the coast exist now as small fractions of their former bounty. Though the connection was largely forgotten in the twentieth century, fishermen in the nineteenth century attributed the decline of the cod fishery to the loss of alewives, an anadromous river herring upon which cod prey. Alewives have been cut off from their spawning and nursery habitat along much of the Gulf of Maine due to the damming of rivers that empty into the Gulf. My research is a part of an ongoing study that aims to establish the historical relationship between cod and other gadoid groundfish fisheries, their ecosystems, and anadromous alewives using spatial data from geographic information systems (GIS). GIS maps were created with the positions of 466 historical Gulf of Maine cod fishing grounds, identified using a database developed by fisheries scientist Ted Ames (whose work is largely responsible for fisheries scientists’ renewed interest in the groundfish-alewife connection). The spatial database generated from these data will be analyzed using a logistical regression to identify characteristics of fishing grounds that define them as fishing grounds, as well as characteristics that determine the relative quality of individual fishing grounds. The Ames database contains data in two main categories: biophysical (ecosystem characteristics) and socioeconomic (infrastructure). The focus of my research was on generating two specific data sets from historical literature, government reports, and experts in the field, and on mapping that data using GIS software (see Figure 1). The first was a list of rivers that supported annual alewife runs before the mid-twentieth century cod groundfish fishery collapse. Using GIS software, I mapped the locations at which these rivers enter the ocean, creating spatial data that show the point at which cod in the Gulf and alewives in the rivers would meet. The second data set was a list of ports and harbors that supported the groundfish industry, also before the mid-twentieth century collapse. These locations were mapped as the areas from which fishing boats would set out in pursuit of groundfish, again creating a set of spatial data points. Both of these data sets were added to the existing spatial database. My data and Ames’ data will be used to calculate distances between individual groundfish fishing grounds and historic alewife runs and between fishing grounds and ports and harbors. Statistical analyses will determine both whether those two factors have any significant relationship with fishing ground quality and the nature of their effects, if any. Ultimately, the results of these analyses will contribute to an increasingly detailed picture of the Gulf of Maine as it existed – physically, ecologically, and economically – when it still supported astoundingly large populations of cod and other groundfish. With a better idea of what the system looked like when it worked properly, we can make a more informed and focused attempt to rebuild it. This research provided me with opportunities to develop practical skills like use of GIS software, contacting and collaborating with scientists, researchers, and government agencies in my field, and data management. I also gained a greater understanding of and appreciation for the complexity and challenge of trying to bring research from the science level to management policy and action. Final Report of research funded by the Cooke Environmental Research Fellowship
Pyrokinin peptides’ effect on the stomatogastric nervous system in the American lobster, Homarus americanus
Date: 2014-08-01
Creator: Xuan Qu
Access: Open access
- Central pattern generators are networks of neurons that produce rhythmic and repetitiveoutputs. These outputs control behaviors such as walking, breathing and digestion. In the Americanlobster, central pattern generators control the behavior of muscles in its foregut, which allows thedigestion of a variety of food types. The stomatogastric ganglion (STG) is a bundle of about thirtyneurons in the foregut of American lobsters. It has been studied extensively since each one of theneurons in it is both identifiable and produces simple patterned outputs. The analysis of American lobster’s stomach behaviors and the neural mechanisms controlling them could provide general insights into how rhythmic motor patterns for locomotion are produced. A large number of the neurons in the STG are modulatory neurons that use neuromodulators for at least part of their synaptic receptions. These neuromodulators are released by neurons and cause long-lasting changes in the synaptic efficacies of the targets. At present, many types of neuropeptides have been identified within the crustacean stomatogastric nervous system. The pyrokinins are members of one peptide family, PBAN. PBAN peptides all share the common Cterminalpentapeptide FXPRL-amide, in which X can be S, T, G, N, or V. Previous studies, using immunohistochemistry, have found that there are pyrokinin peptides present in both the STG and the cardiac ganglion (CG) of American lobsters. My research tests five different kinds of pyrokinin peptides, including PevPK1 (DFAFSPRLamide) and PevPK2 (ADFAFNPRLamide) from the shrimp L.vannamei (Torfs et al., 2001; Ma et al., 2010), CabPK1 (TNFAFSPRLamide) and CabPK2(SGGFAFSPRLamide from the crab C.borealis (Saideman et al., 2007;Ma et al., 2009) and Conserved Sequence (FSPRLamide) from the lobster, H.americanus (Ma, et al, 2008). ConservedSequence, the only pyrokinin identified in the American lobster so far, is highly conserved among many other pyrokinin peptides. Therefore, it is believed to be just a fragment with the complete sequence yet to be identified. Thus, we predicted that it might produce a weaker effect on the STG. Previous studies on the pyrokinin peptides have shown that in crabs, CabPK1, CabPK2 and LeucoPK (identified in an insect), all had a virtually identical effect on the CG, suggesting that the differences among these pyrokinin peptides are not important and the receptors for these peptides are the same. However, research done by Bowdoin students in 2011-2012 showed that among PevPK1,PevPK2, CabPK1, CabPK2, and Conserved Sequence, all but Conserved Sequence (not yet tested) had strong effects on the STG. However, only PevPK2 had an effect on the CG. My goal for this summer research was to determine whether or not there are differences between the responses of the STG to the different peptides in order to further determine the cause for the differences between the responses of the CG and those of the STG. The results from the extracellular recordings from the identified neurons in my research have shown that none of the five kinds of pyrokinin peptides affect the pyloric rhythm, which controls the pumping and filtering of food through the pylorus in Americanlobsters. They all, however, excite the gastric mill rhythm, which controls the movements of the teeth that grind up the food before it is transferred into the pylorus. Moreover, there is no significant difference among the effects of these five kinds of pyrokinin peptides. Conserved Sequence, which was predicted to produce a relatively weaker effect, proved to produce virtually identical effect asfour other kinds of pyrokinin peptides. Future research will focus on studying the differences between the STG and CG to determine the cause of the varied responses between them. Final Report of research funded by the Doherty Coastal Studies Research Fellowship.
Quantification and Characterization of AST-C Peptides in Homarus americanus Using Mass Spectrometry
Date: 2014-08-01
Creator: Amanda Howard
Access: Open access
- Neuropeptides are small signaling molecules found throughout the nervous system that are responsible for influencing animal behavior. They consist of short amino acid chains and interact with cell-membrane receptors in order to regulate behavioral responses (Fig. 1a). The American lobster, Homarus americanus, has proven to be a strong model organism in which to study such activity due to the simplicity of the system and the wealth of existing knowledge about the animal. One neuropeptide found in H. americanus is a C-type allatostatin (AST-C). Allatostatins are a family of neuropeptides originally identified in insects that inhibits juvenile hormone production. The H. americanus AST-C has a pyroglutamate blocked N-terminus and an unmodified C-terminus (Fig. 1b). In addition to AST-C, a different, yet structurally similar neuropeptide has been found in H. americanus. This peptide has an unmodified N-terminus and an amidated C-terminus (Fig. 1c). Both forms of AST-C (referred to as ASTC-real and ASTC-like) also have a disulfide bond between their two cysteine residues. In the lobster, both peptides influence cardiac muscle contraction patterns and have been found in various tissues throughout the nervous system [1, 2]. In order to establish the purpose of the observed post-translational modifications, this study aims to find whether these peptides exist in other forms in the lobster and to determine their relative and absolute concentrations.Liquid chromatography-mass spectrometry (LC-MS) and tandem mass spectrometry (MS/MS) are often used in analytical chemistry to characterize complex samples and identify neuropeptides. First, sample components are separated by chromatography based on properties such as size and hydrophobicity. Using mass spectrometry (MS), peptides are protonated (positively charged) and their mass is determined from their measured mass-to-charge ratios. These peptides are lastly fragmented into many ions using MS/MS, which ultimately allows them to be sequenced in order to determine their identity. This summer, standards of the two AST-C peptides have been characterized by LC-MS/MS. The reduced forms of both peptides have been synthesized by chemically reducing the disulfide bond and were also analyzed by MS/MS. As expected, the structural stability provided by the disulfide bond prevented fragmentation during MS/MS analysis; that is, there was evidence of more fragmentation in the reduced forms than in the fully processed forms (Fig. 2). When looking for other forms of ASTC, these findings will facilitate the identification of the reduced forms in crustacean tissue.To assess the accuracy of the detection method used, detection limits were assessed by analyzing sample matrices augmented with known amounts of peptide standards. The smallest amount of peptide detected from a single injection was 25 fmol (2.5·10-14 mol) peptide. There appeared to be a strongly linear relationship between the amount of ASTC-real injected and the instrument response (chromatographic peak area) (R2=0.996, n=6). However, the relationship between the amount of ASTC-like injected and the instrument response was less linear (R2=0.802, n=5), and the calibration slope was more shallow, indicating that this peptide is more difficult to detect. This is possibly because ASTC-real, unlike ASTC-like, contains an arginine (R) and a histidine (H) residue, two basic amino acids susceptible to protonation. Therefore, it seems that ASTC-real is more easily protonated during the ionization process in MS analysis, causing it to be more readily detected.Lastly, ASTC-real has been identified in the pericardial organ (PO), a tissue responsible for delivering neuropeptides manufactured in the thoracic ganglion to the heart in order to control muscle contraction. ASTC-like is also believed to be present in the PO based on previous work in the Dickinson lab (E. Dickinson, unpublished data), but it is likely that it has not yet been detected in this study due to the detection limitations described above. To address these issues, more tissues will be pooled to increase the amount of peptide in each sample analyzed.Currently, tissue extraction methods are being optimized to eliminate phospholipid contamination and to maximize detection sensitivity. Specifically, two separate extraction solvents as well as a chloroform delipidation procedure are being tested. Future goals include quantifying peptide levels by adding a known amount of internal standard to the samples and comparing instrument responses for ASTC and for internal standard. Additionally, known amounts of peptide standard will be brought through the extraction process to determine the amount of peptide loss throughout this procedure. During the upcoming academic year, this study will be continued as an Honor’s project. Further research in these areas will ultimately help explain how neuropeptides interact to regulate behavior within the lobster and in more complex systems. Final Report of research funded by the Henry L. and Grace Doherty Charitable Foundation Coastal Studies Research Fellowship.
Lesley Vance
Date: 2011-01-01
Creator: Diana K. Tuite
Access: Open access
- Catalog of an exhibition held April 12-July 1, 2012, at the Bowdoin College Museum of Art, Brunswick, Maine. Includes essay "Conspiring forms" by Diana Tuite (p. 2-3)