Showing 3401 - 3450 of 6401 Items
Date: 2023-01-01
Creator: Maya Y. Chandar-Kouba
Access: Open access
- Monitoring forest carbon storage is necessary in accurately modelling the global carbon cycle. In the Northeast, terrestrial forests represent a major carbon sink with above-ground biomass (AGB) accounting for 40% of stored forest carbon. Therefore, understanding how AGB varies spatiotemporally is essential in predicting future carbon storage. Repeated measurements in permanent, long-term plots provide an opportunity to examine how carbon stored in AGB is changing over time. I used 29 years of data from the Harvard Forest Environmental Monitoring Systems (HF EMS) Site to determine how stand composition, intrinsic factors, and extrinsic environmental factors influenced rates of carbon storage in AGB over time. Using a partition around medoids (PAM) clustering method, I separated the 34 ground plots at the EMS stand into their respective stand types. I found that each stand type at the HF EMS plots accumulates carbon at consistent rates throughout the study period, although rates of carbon accumulation between stands were significantly different. Red Pine stands experience a rapid decline in biomass in 2018 due to the introduction of the Southern Pine Beetle. Across all stand types, sporadic mortality events determine variations in yearly rates of carbon accumulation, although this has little significant influence on total AGB accumulation. Leaf area index (LAI) and foliar N contents have no effect on growth increments. Extrinsic environmental variables had mixed effects on growth and mortality, highlighting the complexities of predicting forest carbon storage under changing climate conditions.
Date: 2023-01-01
Creator: Kenneth Garcia
Access: Open access
- Neuromodulation allows for the flexibility of neural circuit dynamics and the outputs they produce. Studies of the stomatogastric nervous system (STNS) have expanded our knowledge on the actions of neuromodulators, small molecules that most often activate G-protein coupled receptors and reconfigure circuit activity and composition. In these systems, modulation has been found to occur at every level, from sensory-motor coupling to neuromuscular transmission (Harris-Warrick and Marder 1991). Neuromodulators have complex effects on motor output; they can alter the firing of individual neurons while also modulating muscle properties, neuromuscular transmission, and sensory neuron response to muscle activity (Fort et al. 2004). We investigated this further by recording the motor output produced by the gastric mill rhythm of the lobster STNS under neuromodulator conditions. How is this neuromuscular system as a whole modulated to produce motor flexibility? We hypothesized that these neuromodulators act on individual receptors of component neurons of central pattern generator (CPG)-effector system themselves and at the periphery, coordinately altering muscle contraction by altering all levels of the crustacean neuromuscular system. Application of NRNFLRFamide, RPCH, oxotremorine, and proctolin to the gastric mill 4 (gm4) muscles of the Cancer crab showed that neuromodulators that have been found to have variable, yet significant effects on the activity of the neurons of the STNS directly alter the activity of the gm4 muscles as well, suggesting that coordination of peripheral actions and direct neuronal modulation regulates patterned motor output.
- Embargo End Date: 2026-05-18
Date: 2023-01-01
Creator: Lily Randall
Access: Embargoed
- Restriction End Date: 2028-06-01
Date: 2023-01-01
Creator: Ean Lev Small
Access: Access restricted to the Bowdoin Community
Date: 2023-01-01
Creator: Jane L. Godiner
Access: Open access
- "Invisible Ailments" is a collection of short stories that trace the depth, breath, and sweeping range of lived experiences of people struggling with mental illness. While it is a work of fiction, the people in these stories might feel eerily familiar — to your friends, your family members, your loved ones, or, if you're brave enough to admit it, yourself.
- Embargo End Date: 2026-05-18
Date: 2023-01-01
Creator: Holden D. Hadfield
Access: Embargoed
- Restriction End Date: 2028-06-01
Date: 2023-01-01
Creator: Jada Scotland
Access: Access restricted to the Bowdoin Community
Date: 2023-01-01
Creator: Rowland Luo
Access: Open access
- The study of neuronal development could provide foundational information on neurogenesis and neuroplasticity. The small size and relatively simple nervous system of Orthoptera make them ideal models for neurodevelopmental studies. The peripheral nervous system development is an intricate and precise process that each sensory neurons are able to reach their central nervous system partners in a relatively short amount of time. Although the peripheral nervous system in limb buds and their genetic regulations are well understood in grasshopper embryos, few studies have explored the developing nervous system in a cricket model. Therefore, the first goal of the current experiment is to characterize the normal peripheral nervous system development in cricket embryos. Previous studies in Drosophila have suggested Toll6 and Toll7 receptors could serve as important targets for the neurotrophic-like factors Spaetzle2 and 5. Malfunctioning neurotrophic pathways could lead to abnormal nervous system development. Therefore, the second goal of the current study is to explore the roles of Toll7 in the development of the cricket peripheral nervous system. Immunohistochemical staining using anti-horseradish peroxidase (Anti-HRP) was used to illustrate crickets' embryonic developing peripheral nervous system in the limb buds from developmental stage 7.0 to 11.0. Cricket eggs were injected with Toll7 double stranded RNA (dsRNA) and rhodamine dye to suppress the Toll7 mRNA level. The control eggs were injected with GFP dsRNA and rhodamine dye. The peripheral nervous system development in cricket embryos is largely homologous to that observed in grasshopper embryos. All later-emerged sensory neurons followed the pathway established by the first pioneer neuron Ti1. Ti1 made stereotypical turns following the steering signals on epithelial and guidepost cell surfaces and eventually fasciculate with lateral motor axons from the central nervous system. When examining the peripheral nervous system development with Toll7 knockdown, a decrease in limb bud volume was observed at stage 7.7 and stage 8.0, suggesting Toll7’s potential roles in aiding cell-cell intercalation processes in Orthoptera embryos. Furthermore, a delay in Ti1 pioneer neuron development was observed with Toll7 knockdown at early developmental stages, providing evidence for Toll-Spaetzle pathway’s neurotrophic-like functions. The results of the current experiment provide the first description of the peripheral nervous system development in the cricket limb buds and further evidence of Toll-Spaetzle pathway’s neurotrophic properties.
- Embargo End Date: 2026-05-18
Date: 2023-01-01
Creator: Bjorn Ludwig
Access: Embargoed
Date: 2023-01-01
Creator: Colby Silva Santana
Access: Open access
- Of Russia's cultural and religious icons, the holy fool (iurodivy) is quite possibly the most significant one of contemporary times. The holy fool – a historical and cultural character that feigns insanity to produce moral and spiritual reflections and hide the purity of their souls – has left its traces over a significant portion of Russia's literary history, postmodern tradition, and socio-political thought. In its uniquely positioned role as a powerful form of institutional critique, today taking shape in modern-day political protest performance culture, the holy fool has often been utilized to interrogate the intertwined relationship of the Russian state and the Orthodox Church. This analysis reviews the scholarship on holy foolery and how it has manifested in various fields of study. Although scholarship on this subject is significant, there exists a lack of research into representation of the holy fool in contemporary Russian cinema. Cinema is uniquely positioned to portray holy foolery, thanks to the unique form of spectatorship the film camera allows. This thesis analyzes several case studies of 21st-century Russian cinema that feature characters representing qualities of iurodstvo and its related models. In doing so, this work traces the history and development of iurodstvo through the lens of cinema and suggests new ways of understanding holy foolery's manifestation as a political tool.
Date: 2023-01-01
Creator: Hafsa Hossain
Access: Open access
- In 1985, Mohd. Ahmad Khan v. Shah Bano Begum, known commonly as the Shah Bano Case, became a flashpoint for Indian democracy. The Shah Bano case revolved around the maintenance of a divorced woman, not the first of its kind by any means. A case that sparked major social and political upheaval during a broader period of political turmoil, the Shah Bano case has long been interpreted as an expression of the crisis and contradictions between the democratic rights of women as citizens and the democratic rights of Muslims as a religious minority in the Indian nation-state. In the immediate aftermath of the case, critical feminist and post-colonial scholarship grappled with the dilemmas it involved, but to some extent remained caught up in those dilemmas. This thesis builds upon the important work of these and later scholars, but it also draws new attention to the specific role of the English-language public sphere in shaping the terms of debate that surrounded the case in the 1980s. This paper argues against the binary understanding of the landmark Shah Bano Case as either a failure or success of Indian secularism. I argue that the case and its aftermath demonstrate the continual nature of Indian secularism and democratic practice, especially laden in the post-Emergency era.
- Restriction End Date: 2029-06-01
Date: 2024-01-01
Creator: Olivia Sewon Choi
Access: Access restricted to the Bowdoin Community
Date: 2024-01-01
Creator: Marcus Gadsden
Access: Open access
- This dissertation examines the existence of racial bias within capital punishment. Since colonial times discriminatory death sentencing has impacted racial minorities, and despite living in a post-colonial epoch, the United States Justice system continues to produce alarming racial disparities. Consequently, both law reviews and social science journals indicate that race remains a significant factor in criminal trials. So, to what extent does racial bias influence capital punishment trials? Given that it does exist, how can it be alleviated? Through a statistical/qualitative analysis of psychological studies, Supreme Court cases, and jury instructions, this dissertation suggests that implicit cognitive bias continues to produce daunting realities in contemporary criminal punishment processes. Notably among juries, traditional judicial procedures have ostensibly triggered implicit bias and psychological intimidation, i.e. jury instructions. Moreover, do long and complicated jury instructions heighten instances of partial judgment? In Racial Bias within Capital Punishment: Instructional Comprehension, I argue that inaccessible jury instructions provide a space where jurors adhere to subtle racial preferences. Consequently, the swaying capacity of juries in capital punishment trials proceeds to arbitrarily produce discrepancies in sentencing rates.
- Embargo End Date: 2028-05-17
Date: 2023-01-01
Creator: Lyn Stephanie Miranda Portillo
Access: Embargoed
Date: 2023-01-01
Creator: Isabella de la Luz Quintana
Access: Access restricted to the Bowdoin Community
- Embargo End Date: 2026-05-18
Date: 2023-01-01
Creator: Andrew YH Chang
Access: Embargoed
- Embargo End Date: 2028-05-18
Date: 2023-01-01
Creator: Annika Moore
Access: Embargoed
Date: 2023-01-01
Creator: Arav Agarwal
Access: Open access
- We begin with the classical study of the Riemann zeta function and Dirichlet L-functions. This includes a full exposition on one of the most useful ways of exploiting their connection with primes, namely, explicit formulae. We then proceed to introduce statistics of low-lying zeros of Dirichlet L-functions, discussing prior results of Fiorilli and Miller (2015) on the 1-level density of Dirichlet L-functions and their achievement in surpassing the prediction of the powerful Ratios Conjecture. Finally, we present our original work partially generalizing these results to the case of Hecke L-functions over imaginary quadratic fields.
Date: 2008-04-21
Creator: Michael 'Mike' M Hastings
Access: Open access
Biographial Note
Michael M. Hastings, a native of Morrill, Maine, graduated from Tilton School (NH) in 1968 and Bowdoin College in 1972. Following a year of graduate study in Public & International Affairs at George Washington University, he worked for seven years as a foreign and defense policy aide to Senator William S. Cohen (1973-1980) and for four years for Senator George J. Mitchell (1980-1984). In October 1984, he joined the international staff of Catholic Relief Services (CRS) and moved to Africa. Over a span of eight years, he worked as a CRS development administrator in Kenya, Tanzania, Togo and The Gambia. During the same period, he assisted in the provision of emergency food for people displaced by civil wars in the Southern Sudan and Liberia. In 1992, he returned to Maine to direct a “center for excellence,” focusing on aquaculture and economic development. Since 2004, he has worked for the University of Maine as its director of Research and Sponsored Programs. Between 1992 and 2008, he also served on several civic boards and institutions including the Maine Fishermen’s Forum, the Maine Oil Spill Advisory Committee, the Maine Indian Tribal State Commission, the Down East Institute, and the Maine Sea Grant Policy Advisory Committee. Between 1996 and 2001, he was elected three times to be a member of the Town Council of Hampden, Maine, where he resides with his wife, a middle school teacher.
Summary
The interview includes discussion of: the culture of Belfast, Maine during the ‘50s and ‘60s; family history; University of Maine campus atmosphere during the ‘60s; influential teachers; Bowdoin College atmosphere and cultural changes during the late ‘60s and early ‘70s; Ten-College Exchange; the draft and its effect on Bowdoin College students; influential Bowdoin College professors; Athern Daggett; Chris Potholm and connection to Bill Cohen; War Powers Act; working for the Cohen congressional campaign; political identity of Androscoggin and Oxford counties; the Cohen walk; differences between Maine’s Republican and Democratic parties; job responsibilities under Bill Cohen; description of Bill Cohen; appointment of George Mitchell to fill Edmund Muskie’s Senate seat; and moving from Senator Cohen to Senator Mitchell’s staff.
Date: 2008-12-11
Creator: W. 'Steve' Stephen Hart
Access: Open access
Biographial Note
Walter Stephen Hart was born January 17, 1955, in Washington, DC, to Peter William Hart and Mary Jane Strauss Hart; his parents were librarians. He attended Arizona State University, where he earned a degree in mass communications. He worked at a radio station in New Hampshire and covered the 1980 presidential primaries. He returned to school at Ball State, graduating with a degree in journalism and a minor in public relations, after which he moved to Maine, where his wife was working. He worked for Maine congressional candidate Phil Merrill in the 1982 primary, and after Merrill lost to John Kerry, Hart worked as Kerry’s press secretary. Hart was hired as a legislative assistant to Senator Mitchell in March of 1983. He was primarily responsible for Agriculture, Veterans’ Affairs, Governmental Affairs and Energy and Natural Resources issues. He remained on Mitchell’s staff until the senator’s retirement in January, 1995. At the time of this interview Hart was deputy director of legislative affairs for the USDA Forest Service.
Summary
Interview includes discussions of: 1982 congressional election in Maine; his role in Mitchell’s office; how Senate members and staff cooperate to get the best information; how Mitchell’s role changed when he became majority leader and how that impacted the staff; parochial interests; earmarks and the purpose they serve; Maine Blueberry Commission earmark; the Bicentennial Lighthouse Fund; the Coast Guard facility at Cape Elizabeth; maple syrup regulation on the Nurses Training Bill; the appropriations process; Mitchell staff salaries and his idea of “psychic remuneration”; the importance Mitchell placed on meeting with and responding to constituents; lobbyists’ role in providing information; the appropriations bill after hurricane Hugo; the senator’s division of time between the work of the Senate and being the public face of the Democratic Party; comparing Robert Byrd and Senator Mitchell as majority leaders; the reasoning behind retiring from the Senate when he did; anecdote about Hart and the chief of staff of Agriculture; Togus hearing on PTSD; the White Mountain National Forest nuclear waste disposal hearing; and the Northern Forest Study proposal hearings in Bangor.
Date: 2009-05-07
Creator: Patrick J Griffin
Access: Open access
Biographial Note
Patrick J. Griffin was born June 22, 1949, in New York to Daniel and Edith Griffin. He attended St. Peter’s College in New Jersey, then the University of Wisconsin-Milwaukee for graduate studies in urban policy. He worked as a Health, Education and Welfare fellow for a year, then spent a year on the Senate Budget Committee staff before becoming a member of Senator Byrd’s leadership staff, the Democratic Policy Committee staff, and later a Senate Floor staffer, where he met Senator Mitchell. He held the position of secretary of the Democratic Caucus, an elected position. He later started a lobbying firm with David Johnson, returning to politics to join the Clinton administration.
Summary
Interview includes discussion of: family, educational, and career background; responsibilities of Senate floor staff; majority leader race an Inouye; Iran-Contra; Acid Rain and Senator Byrd; Crime Bill; Byrd’s decision to move to the Appropriations Committee; Griffin’s relationship with Senator Byrd; experiences in the Clinton White House; health care debate; Mitchell-Clinton relationship; background on the Northern Ireland appointment and Clinton conversation; comparison of several majority leaders; and Tip O’Neill.
Date: 2010-02-05
Creator: Deborah 'Debbie' B Ward
Access: Open access
Biographical Note
Deborah “Debbie” (Bedard) Ward was born in Saco, Maine, on March 22, 1951. She was graduated from Thornton Academy in 1969 and then attended Westbrook College. Subsequently, she worked as a secretary for the Westbrook College Department of Nursing. In 1972, she became involved in reviving the Saco Young Democrats, and in 1973 George Mitchell hired her as the first staff person for his gubernatorial campaign. After Mitchell lost the election to Jim Longley, Ward returned to Westbrook College to work as a house mother. She took the position of calendar clerk for the Maine state legislature, then was elected assistant clerk and held that position for eighteen years.
Summary
Interview includes discussion of: growing up in Saco in the 1950s and 1960s; splitting time between Virginia and Maine; reviving the Saco Young Democrats with Mike Aube and Barry Hobbins when Bill Hathaway ran against Margaret Chase Smith; campaigning as a part of the Young Democrats; being hired by Mitchell; Mitchell’s gubernatorial campaign volunteer base; working with Tony Buxton and Mike Aube; Mitchell’s running against and beating Joe Brennan in the primary; the state party structure; surprise at Longley winning the campaign; working as calendar clerk and assistant clerk for the state legislature; observing Mitchell’s progress to senator; and Joe Angelone.
Date: 2009-06-19
Creator: James L Ladd
Access: Open access
Biographial Note
James Loring Ladd was born February 18, 1933, in Milo, Maine, to Marianne Louise McKechnie and Vaughn Loring Ladd. He grew up in Milo and attended Foxcroft Academy. He was graduated from Bowdoin College in 1954 with a major in psychology; he and George Mitchell were classmates. Prior to the beginning of his senior year, he became married to Shirley Ladd; they have four children. He spent a year teaching, then was drafted into the Army and served in Korea for two years. He made a career in the real estate business in Milo, Maine, and is now retired.
Summary
Interview includes discussion of: growing up in Milo, Maine; traveling to Boston as a child; attending Foxcroft Academy; watching baseball and playing sports; attending Bowdoin College; George Mitchell at Bowdoin; the fraternities at Bowdoin; train service in Maine; participating in ROTC at Bowdoin and serving in Korea; teaching eighth grade at Mattawamkeag and coaching basketball and baseball at Newport High School; the Milo, Maine area; seeing George Mitchell when he would visit the local high school; Ladd’s children; and the increasing cost of a Bowdoin education.
Date: 2009-10-07
Creator: Scott F Hutchinson
Access: Open access
Biographial Note
Scott Frederick Hutchinson was born in Gardiner, Maine, on April 16, 1929, to Helen Frances and Scott Arthur Hutchinson. His mother was a homemaker, and his father was employed by New England Telephone Company, rising in the ranks from line worker to vice president. Scott’s childhood was spent living in various communities throughout New England. He attended Northeastern University, and after college served in the Army during the Korean War. Coming back to Maine, he began a career in banking. During Ken Curtis’ campaign for governor, he served as treasurer. He then served as treasurer for Ed Muskie’s senatorial campaigns, vice presidential campaign, and as treasurer for Muskie's presidential primary race. He served as George Mitchell’s campaign treasurer.
Summary
Interview includes discussion of: working on Muskie’s staff with Mitchell in 1976; Maine gubernatorial campaign (1974); why Mitchell lost to Longley; Joe Angelone; Mitchell's running for Senate majority leader; Mitchell’s 1982 reelection campaign; David Emery; Mitchell’s relationship with Bill Cohen; the role of Independents in Mitchell’s campaigns; campaign changes for Mitchell between 1974 and 1982; and Hutchinson’s reaction to Mitchell’s announcement of retirement.
Date: 2019-05-31
Creator: James Pierce
Access: Open access
- James A. “Jim” Pierce (Class of 1969) recounts his sight-unseen arrival to Bowdoin in 1965. He speaks about the fraternity system’s dominance over everything from food and lodging to social life. He describes the fraternities’ drinking culture and hazing rituals, as well as the “eccentric” nature of his own fraternity, Alpha Rho Upsilon. Pierce comments on the milieu of “rugged Christianity” he felt at Bowdoin, especially through mandatory chapel attendance. Additionally, he talks about his experiences with the Glee and Drama Clubs, Bowdoin’s academic rigor, and the prank group the Green Hornet Construction Company. Pierce also reflects on feeling the presence and impacts of the Vietnam War on campus.
Date: 2019-06-01
Creator: Christopher Lierle
Access: Open access
- Christopher “Chris” Lierle (Class of 1989) discusses adjusting to Bowdoin life from the West Coast and making close friendships despite the culture shock. He speaks about the importance of extracurricular activities during his time at Bowdoin and reminisces on his experiences with the football team and winning the Best Actor award in the One Act play competition. Lierle also reflects on not completing his Bowdoin education and the events in his life that led him to reconnect with the Bowdoin community twenty-five years later. He discusses the cherished relationships he forged during his time on campus and how they defined his time at college.
Date: 2019-06-01
Creator: Cathy Scheiner
Access: Open access
- Cathy Scheiner (Class of 1979) describes the culture-shock she felt when transitioning to Bowdoin from public high school. She speaks about meeting many different types of people in Hyde Hall and joining various extracurricular activities like the Outing Club, the Sailing team, and the Cross-Country Ski team. She talks about being independent from the Greek system while navigating the fraternity-dominated social landscape. Scheiner reminisces on her classes and professors, adventures around Maine with friends, and being a Biochemistry major. Also, she reflects on the discussions of the time surrounding efforts to not be just a Bowdoin student, but a member of the broader Maine community as well.
Date: 2019-08-16
Creator: Richard Burns
Access: Open access
- Richard “Dick” Burns (Class of 1958) describes being “very impressed” by Bowdoin when he first visited and the busyness of his first few weeks at the College. He talks about how the social life of the school revolved around fraternities and his own experience joining Chi Psi, despite ambivalence about the Greek system. Burns reminisces about various mentors and memorable professors, including his long-standing friendship with former athletic trainer Mike Linkovich. He talks about his job washing dishes in his fraternity, Ivies Weekend, and the drinking culture of the time. Finally, he comments on his multi-generational view of Bowdoin, Brunswick, and New England, and remarks on some of the most notable ways that the College has changed.
Date: 2017-05-01
Creator: Abby Elizabeth Motycka
Access: Open access
- What was the impact of Brown v. Board of Education on the United States and how did pro-segregationists in the South respond? In order to answer this question, I argue three key arguments over the course of three chronological chapters. In chapter one, I argue that segregationists from southern states responded to Brown by fighting to preserve segregation in order to protect a racial hierarchy they believed was essential. This racial hierarchy is magnified in the southern capital of Little Rock, Arkansas, which I argue in chapter two exposed segregationists’ political defiance and poor organization around racial integration of public schools. After a year of integration, analyzed in chapter three, I conclude my chapters by arguing the first year slowed down the segregationist organizations, but did not persuade them that racial integration would improve the “southern way of life.”
Date: 2017-05-01
Creator: Savannah Blake Horton
Access: Open access
- This is What You Want: Stories is a collection of nine stories exploring the role of humor in dark situations. It is a work of fiction.
Date: 2024-01-01
Creator: Jared Lynch
Access: Open access
- The mitochondrial genome has historically been relegated to a neutral genetic marker, but new evidence suggests mitochondrial DNA to be a target for adaptation to environmental stress. The invasive European green crab (Carcinus maenas) exemplifies this in the Gulf of Maine’s hybrid zone, where interbreeding populations exhibit thermal tolerances influenced by mitochondrial genotype. To better understand the mechanism behind this phenomenon, the effect of mitochondrial genotype on mitochondrial activity was tested by measuring mtDNA copy number (mtCN) and the activity of complex I, II, and IV of the electron transport system via high-resolution respirometry. Mitochondria isolated from frozen heart tissue were measured at three temperature points—5°C, 25°C, and 37°C—to represent thermal stresses and a control. It was predicted that cold-adapted haplogroups would exhibit both higher mtCN and increased activity for each complex, either across all temperatures or exclusively at 5°C compared to a warm-adapted haplogroup. Initial comparisons of mitochondria from fresh and frozen tissue at 25°C found lower activity for complex II and IV in frozen extracts, but they continued to be used for convenience. No differences were observed across haplogroups for mtCN or high-resolution respirometry, suggesting that mitochondrial activity does not underlie differences in thermal tolerance. However, temperature greatly influenced activity measurements with complex II and IV exhibiting the highest rates at 37°C while complex I exhibited optimal activity at 25°C. This study represents the first of its kind for C. maenas, providing a foundation for future experiments to continue exploring mitochondria in the context of adaptive evolution.
- Embargo End Date: 2029-05-16
Date: 2024-01-01
Creator: Juliana Keyes Vandermark
Access: Embargoed
- Restriction End Date: 2027-06-01
Date: 2024-01-01
Creator: Oliver Wang
Access: Access restricted to the Bowdoin Community
Date: 2020-12-01
Creator: Andrew E. Christie, Cindy D. Rivera, Catherine M. Call, Patsy S. Dickinson, Elizabeth A., Stemmler, J. Joe Hull
Access: Open access
- Over the past decade, in silico genome and transcriptome mining has led to the identification of many new crustacean peptide families, including the agatoxin-like peptides (ALPs), a group named for their structural similarity to agatoxin, a spider venom component. Here, analysis of publicly accessible transcriptomes was used to expand our understanding of crustacean ALPs. Specifically, transcriptome mining was used to investigate the phylogenetic/structural conservation, tissue localization, and putative functions of ALPs in decapod species. Transcripts encoding putative ALP precursors were identified from one or more members of the Penaeoidea (penaeid shrimp), Sergestoidea (sergestid shrimps), Caridea (caridean shrimp), Astacidea (clawed lobsters and freshwater crayfish), Achelata (spiny/slipper lobsters), and Brachyura (true crabs), suggesting a broad, and perhaps ubiquitous, conservation of ALPs in decapods. Comparison of the predicted mature structures of decapod ALPs revealed high levels of amino acid conservation, including eight identically conserved cysteine residues that presumably allow for the formation of four identically positioned disulfide bridges. All decapod ALPs are predicted to have amidated carboxyl-terminals. Two isoforms of ALP appear to be present in most decapod species, one 44 amino acids long and the other 42 amino acids in length, both likely generated by alternative splicing of a single gene. In carideans, a gene or terminal exon duplication appears to have occurred, with alternative splicing producing four ALPs, two 44 and two 42 amino acid isoforms. The identification of ALP precursor-encoding transcripts in nervous system-specific transcriptomes (e.g., Homarus americanus brain, eyestalk ganglia, and cardiac ganglion assemblies, finding confirmed using RT-PCR) suggests that members of this peptide family may serve as locally-released and/or hormonally-delivered neuromodulators in decapods. Their detection in testis- and hepatopancreas-specific transcriptomes suggests that members of the ALP family may also play roles in male reproduction and innate immunity/detoxification.
- Embargo End Date: 2025-05-16
Date: 2024-01-01
Creator: Leopold Felix Spieler
Access: Embargoed
Date: 2019-10-01
Creator: Patsy S. Dickinson, Heidi M. Samuel, Elizabeth A. Stemmler, Andrew E. Christie
Access: Open access
- The SIFamides are a broadly conserved arthropod peptide family characterized by the C-terminal motif –SIFamide. In decapod crustaceans, two isoforms of SIFamide are known, GYRKPPFNGSIFamide (Gly1-SIFamide), which is nearly ubiquitously conserved in the order, and VYRKPPFNGSIFamide (Val1-SIFamide), known only from members of the astacidean genus Homarus. While much work has focused on the identification of SIFamide isoforms in decapods, there are few direct demonstrations of physiological function for members of the peptide family in this taxon. Here, we assessed the effects of Gly1- and Val1-SIFamide on the cardiac neuromuscular system of two closely related species of Cancer crab, Cancer borealis and Cancer irroratus. In each species, both peptides were cardioactive, with identical, dose-dependent effects elicited by both isoforms in a given species. Threshold concentrations for bioactivity are in the range typically associated with hormonal delivery, i.e., 10−9 to 10−8 M. Interestingly, and quite surprisingly, while the predicted effects of SIFamide on cardiac output are similar in both C. borealis and C. irroratus, frequency effects predominate in C. borealis, while amplitude effects predominate in C. irroratus. These findings suggest that, while SIFamide is likely to increase cardiac output in both crabs, the mechanism through which this is achieved is different in the two species. Immunohistochemical/mass spectrometric data suggest that SIFamide is delivered to the heart hormonally rather than locally, with the source of hormonal release being midgut epithelial endocrine cells in both Cancer species. If so, midgut-derived SIFamide may function as a regulator of cardiac output during the process of digestion.
Date: 2007-05-15
Creator: Elizabeth A. Stemmler, Emily A. Bruns, Noah P. Gardner, Patsy S. Dickinson, Andrew E., Christie
Access: Open access
- In invertebrates, peptides possessing the carboxy (C)-terminal motif -RXRFamide have been proposed as the homologs of vertebrate neuropeptide Y (NPY). Using matrix assisted laser desorption/ionization mass spectrometry, in combination with sustained off-resonance irradiation collision-induced dissociation and chemical and enzymatic reactions, we have identified the peptide pEGFYSQRYamide from the neuroendocrine pericardial organ (PO) of the crab Pugettia producta. This peptide is likely the same as that previously reported, but misidentified, as PAFYSQRYamide in several earlier reports (e.g. [Li, L., Kelley, W.P., Billimoria, C.P., Christie, A.E., Pulver, S.R., Sweedler, J.V., Marder, E. 2003. Mass spectrometric investigation of the neuropeptide complement and release in the pericardial organs of the crab, Cancer borealis. J. Neurochem. 87, 642-656; Fu, Q., Kutz, K.K., Schmidt, J.J., Hsu, Y.W., Messinger, D.I., Cain, S.D., de la Iglesia, H.O., Christie, A.E., Li, L. 2005. Hormone complement of the Cancer productus sinus gland and pericardial organ: an anatomical and mass spectrometric investigation. J. Comp. Neurol. 493, 607-626.]). The -QRYamide motif contained in pEGFYSQRYamide is identical to that present in many vertebrate members of the NPY superfamily. Mass spectrometric analysis conducted on the POs of several other decapods showed that pEGFYSQRYamide is present in three other brachyurans (Cancer borealis, Cancer irroratus and Cancer productus) as well as in one species from another decapod infraorder (Lithodes maja, an anomuran). Thus, our findings show that at least some invertebrates possess NPY-like peptides in addition to those exhibiting an -RXRFamide C-terminus, and raise the question as to whether the invertebrate -QRYamides are functionally and/or evolutionarily related to the NPY superfamily. © 2007 Elsevier Inc. All rights reserved.
Date: 1994-09-30
Access: Open access
- There are two volumes numbered 125. This is the original.
Date: 1994-10-07
Access: Open access
- There are two volumes numbered 125. This is the original.
Date: 1995-02-03
Access: Open access
- There are two volumes numbered 125. This is the original.
Date: 1995-03-03
Access: Open access
- There are two volumes numbered 125. This is the original.
Date: 1995-09-15
Access: Open access
- There are two volumes numbered 126. This is the original.
Date: 1995-11-17
Access: Open access
- There are two volumes numbered 126. This is the original.
Date: 1995-10-27
Access: Open access
- There are two volumes numbered 126. This is the original.
Date: 1995-12-01
Access: Open access
- There are two volumes numbered 126. This is the original.