Showing 2031 - 2040 of 2040 Items
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.
Demography of a Collapsing Aerial Insectivore Population
Date: 2017-05-01
Creator: Liam Taylor
Access: Open access
- Aerial insectivores have been declining across northeastern North America since the end of the 20th century. The mechanisms and demographic patterns of this decline are unclear. On Kent Island, New Brunswick, Canada, an isolated population of Tree Swallows (Tachycineta bicolor) collapsed between 1987 and 2010. To explore how demographic rates (i.e., survival, reproduction, and immigration) drove the population dynamics of these northeastern aerial insectivores, we combined productivity, population survey, and capture-recapture data in an integrated population model analysis. Neither consistently low juvenile survival rates, adult survival rates, nor clutch size were correlated with population growth rate across years. Alternatively, male and female immigration, hatching success, and fledging success rates were correlated with population growth rate. Because local hatching and fledging success rates cannot influence a population without local recruitment, we argue that the demography of these Tree Swallows is mainly structured by immigration. Parameter-substitution simulations revealed that overall decline was likely even if the population had avoided the worst years of demographic collapse. Breeding Bird Survey comparisons demonstrated how the Kent Island population represents both a demographic and geographical extreme at the edge of a declining region. These demographic patterns highlight the sensitivity, even to the point of local extinction, of some isolated populations to region-scale patterns in the production of potential immigrants.
In situ HCR in non-traditional arthropods
Date: 2024-01-25
Creator: Heather Bruce
Hadley Wilson Horch
Access: Open access
- Visualizing the expression of genes is a fundamental tool in molecular biology. Traditional colorimetric in situ hybridization using long RNA probes has been a staple for visualizing gene expression but has many drawbacks. In situ HCR v3.0, developed by Choi et. al. 2018, offers improvements over traditional in situs in nearly every aspect: probes can simply be ordered rather than painstakingly cloned and transcribed, which also makes them cost-effective; an HCR takes just three days to complete rather than five or more days; HCR is robust and works well for first-time users; and HCR probes can be multiplexed, allowing four to eight genes to be visualized in a single sample. HCR has been used successfully in many arthropods, including insects (Drosophila, Tribolium), crustaceans (Parhyale, Daphnia, Artemia), and chelicerates (Limulus horseshoe crab, Acanthoscurria tarantula). In this demo, you will learn how to design and order HCR probes as well as best practices for experimental design.
Interview with Ken Carpenter (Class of 1958), Deborah Jenson (Class of 1983), and Jim Jenson (Class of 1982) by Ben Bousquet
Date: 2018-06-02
Creator: Ken Carpenter
Deborah Jenson
Jim Jenson
Access: Open access
- In this oral history, Ken Carpenter (Class of 1958), Deborah Carpenter Jenson (Class of 1983), and Jim Jenson (Class of 1982) reflect on their respective experiences at Bowdoin. Ken speaks of his background as an “orphan” (his father had died and his mother could not afford to raise him) attending Girard College for Boys, his transition to Bowdoin life as a first-generation student, and his involvement with the Delta Sigma fraternity. He also explores how the research skills that he gained at Bowdoin influenced his career as a cataloger, librarian, and author. Ken and his daughter, Deborah, go on to explain that, during his time at Bowdoin, Ken met his future wife, Mary Carpenter, at a boarding house in Brunswick run by Mary’s mother, Elizabeth Wilson. They later explain that Mary Carpenter had also lost her father and that Mary’s subsequent career in academia influenced Deborah’s career path. Deborah also recounts the factors that affected her decision to attend Bowdoin, as well as a hazing story from her early days at Delta Kappa Epsilon. Jim tells of his decision to enroll at the College, his transition from California to Maine, and his experience in the Theta Delta Chi fraternity. The three also discuss their thoughts on Bowdoin’s decision to eliminate fraternities.
Interview with Jean Brountas (Class of 1983) by Ben Bousquet
Date: 2018-06-01
Creator: Jean Brountas
Access: Open access
- Jean “Jeannie” Brountas (Class of 1983) describes growing up in a Greek Orthodox family and the role that played in her transition to Bowdoin. She also discusses how she has applied her Bowdoin education to her career in business. She describes some of her jobs and other activities, including working for Residential Life and the Library and volunteering at a local middle school. She lists some of her favorite professors, including Professors William Watterson and William Whiteside. She recalls a prank by her freshman proctor that led to Brountas becoming more sociable, and tells of her later experience in the Chi Psi fraternity as a nondrinker.
Interview with Melissa Hudson Howard (Class of 2005) and John Howard (Class of 2009) by Meagan Doyle
Date: 2019-06-01
Creator: Melissa Hudson Howard
John Howard
Access: Open access
- Melissa Hudson Howard (Class of 2005) and John Howard (Class of 2009) describe what brought them each to Bowdoin. The first few weeks of Hudson Howard’s first year were marked by the September 11 Terrorist Attacks and Howard’s by Hurricane Katrina, and both speak about the atmosphere of campus during those times. The pair reminisce about their engagement in Theater and Dance, the Bowdoin Outing Club, Obvious hip hop group, African American Society, and Residential Life. Both Hudson Howard and Howard studied abroad, in London and Paris, respectively, and they reflect on the lasting impacts of those experiences. They comment on student activism on campus and mention the Iraq War and the 2008 Presidential Election in particular.
Interview with Todd Caulfield (Class of 1989) by Emma Kellogg
Date: 2019-05-31
Creator: Todd Caulfield
Access: Open access
- Todd Caulfield (Class of 1989) talks about the insecurities he felt coming to Bowdoin, in terms of both his academic preparedness and the College’s lack of socio-economic diversity. He describes how he found his social footing through the fraternity system, the sailing team, and the theater department. Reflecting further on fraternities, Caulfield remembers a tension between the independent and initiated members of campus and discusses his own choice to remain independent rather than initiate fully into Zeta Psi. Additionally, he speaks about how he spent his time and how he came to major in Biochemistry. Finally, Caulfield speaks about the ethics and implicit lessons he feels he absorbed through his time at Bowdoin and their lasting impact on his life.
Interview with Joan Britt (Class of 1979) by Emma Kellogg
Date: 2019-05-31
Creator: Joan Britt
Access: Open access
- Joan Britt (Class of 1979) talks about falling in love with Bowdoin while visiting her older brother when he was a student. After matriculating, she joined Chi Psi fraternity as a social member, was a student representative for the Economics department, and spent time as a volunteer Sunday school teacher. She speaks about her studies as an Economics major and the relationships she built with her professors and mentors. Britt also reflects on being a member of one of the early coeducated classes and the slight feeling of “second class citizenship” she sensed on campus, especially in the fraternities. Additionally, she talks about her year abroad in Vienna and reintegrating back into the Bowdoin community afterward.
Interview with Nessa Reifsnyder (Class of 1986) by Emma Kellogg
Date: 2019-07-26
Creator: Nessa Reifsnyder
Access: Open access
- Nessa Reifsnyder (Class of 1986) describes feeling “a little out of step” while transitioning from urban life in New York City to Brunswick, despite the summers she had spent in Northern Maine. She talks about finding a strong support system in the fraternity Alpha Delta Phi, whose culture felt “evolved” compared to the rest of campus. She discusses feeling “disaffected” from the College’s academic life. She reminisces about the important life lessons she learned during her time in the fraternity, especially about interpersonal skills and feminism. Reifsnyder speaks about finding a grounding comfort in the “working class element” of Brunswick. Finally, she discusses her role in the negotiations between Bowdoin and ADP when the College decided to phase out fraternities.
Interview with Eric Luft (Class of 1974) by Emma Kellogg
Date: 2019-05-31
Creator: Eric Luft
Access: Open access
- Eric Luft (Class of 1974) recounts a feeling of liberation upon arriving at Bowdoin. Luft describes becoming a double major in Philosophy and Religion, and building relationships with professors both in and outside the classroom. Luft mentions participating in Masque and Gown and the rifle team and also reflects on Bowdoin’s social environment as it related to fraternities and the College's transition to coeducation. Additionally, Luft speaks about student activism and protesting the Vietnam War off-campus. Finally, Luft reminisces about finding community at Bowdoin and emphasizes that while the academics were difficult there was a palpable sense of support.