Showing 2031 - 2040 of 2040 Items
RPCH modulation of a multi-oscillator network: Effects on the pyloric network of the spiny lobster
Date: 2001-01-01
Creator: Patsy S. Dickinson
Jane Hauptman
John Hetling
Anand Mahadevan
Access: Open access
- The neuropeptide red pigment concentrating hormone (RPCH), which we have previously shown to activate the cardiac sac motor pattern and lead to a conjoint gastric mill-cardiac sac pattern in the spiny lobster Panulirus, also activates and modulates the pyloric pattern. Like the activity of gastric mill neurons in RPCH, the pattern of activity in the pyloric neurons is considerably more complex than that seen in control saline. This reflects the influence of the cardiac sac motor pattern, and particularly the upstream inferior ventricular (IV) neurons, on many of the pyloric neurons. RPCH intensifies this interaction by increasing the strength of the synaptic connections between the IV neurons and their targets in the stomatogastric ganglion. At the same time, RPCH enhances postinhibitory rebound in the lateral pyloric (LP) neuron. Taken together, these factors largely explain the complex pyloric pattern recorded in RPCH in Panulirus.
Analytical tendex and vortex fields for perturbative black hole initial data
Date: 2012-10-26
Creator: Kenneth A. Dennison
Thomas W. Baumgarte
Access: Open access
- Tendex and vortex fields, defined by the eigenvectors and eigenvalues of the electric and magnetic parts of the Weyl curvature tensor, form the basis of a recently developed approach to visualizing spacetime curvature. In particular, this method has been proposed as a tool for interpreting results from numerical binary black hole simulations, providing a deeper insight into the physical processes governing the merger of black holes and the emission of gravitational radiation. Here we apply this approach to approximate but analytical initial data for both single boosted and binary black holes. These perturbative data become exact in the limit of small boost or large binary separation. We hope that these calculations will provide additional insight into the properties of tendex and vortex fields and will form a useful test for future numerical calculations. © 2012 American Physical Society.
Injecting gryllus bimaculatus eggs
Date: 2019-08-01
Creator: Samantha K. Barry
Taro Nakamura
Yuji Matsuoka
Christoph Straub
Hadley W., Horch
Cassandra G. Extavour
Access: Open access
- Altering gene function in a developing organism is central to different kinds of experiments. While tremendously powerful genetic tools have been developed in traditional model systems, it is difficult to manipulate genes or messenger RNA (mRNA) in most other organisms. At the same time, evolutionary and comparative approaches rely on an exploration of gene function in many different species, necessitating the development and adaptation of techniques for manipulating expression outside currently genetically tractable species. This protocol describes a method for injecting reagents into cricket eggs to assay the effects of a given manipulation on embryonic or larval development. Instructions for how to collect and inject eggs with beveled needles are described. This relatively straightforward technique is flexible and potentially adaptable to other insects. One can gather and inject dozens of eggs in a single experiment, and survival rates for buffer-only injections improve with practice and can be as high as 80%. This technique will support several types of experimental approaches including injection of pharmacological agents, in vitro capped mRNA to express genes of interest, double-stranded RNA (dsRNA) to achieve RNA interference, use of clustered regularly interspaced short palindromic repeats (CRISPR) in concert with CRISPR-associated protein 9 (Cas9) reagents for genomic modification, and transposable elements to generate transient or stable transgenic lines.
De novo assembly of a transcriptome for the cricket Gryllus bimaculatus prothoracic ganglion: An invertebrate model for investigating adult central nervous system compensatory plasticity
Date: 2018-07-01
Creator: Harrison P. Fisher
Micah G. Pascual
Sylvia I. Jimenez
David A. Michaelson
Colby T., Joncas
Eleanor D. Quenzer
Andrew E. Christie
Hadley W. Horch
Access: Open access
- The auditory system of the cricket, Gryllus bimaculatus, demonstrates an unusual amount of anatomical plasticity in response to injury, even in adults. Unilateral removal of the ear causes deafferented auditory neurons in the prothoracic ganglion to sprout dendrites across the midline, a boundary they typically respect, and become synaptically connected to the auditory afferents of the contralateral ear. The molecular basis of this sprouting and novel synaptogenesis in the adult is not understood. We hypothesize that well-conserved developmental guidance cues may recapitulate their guidance functions in the adult in order to facilitate this compensatory growth. As a first step in testing this hypothesis, we have generated a de novo assembly of a prothoracic ganglion transcriptome derived from control and deafferented adult individuals. We have mined this transcriptome for orthologues of guidance molecules from four well-conserved signaling families: Slit, Netrin, Ephrin, and Semaphorin. Here we report that transcripts encoding putative orthologues of most of the candidate developmental ligands and receptors from these signaling families were present in the assembly, indicating expression in the adult G. bimaculatus prothoracic ganglion.
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 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 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 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.