Showing 1 - 10 of 19 Items
Neural compensation in response to salinity perturbation in the cardiac ganglion of the American lobster, Homarus americanus
Date: 2024-01-01
Creator: Josephine P. Tidmore
Access: Open access
- Central pattern generator (CPG) networks produce the rhythmic motor patterns that underlie critical behaviors such as breathing, walking, and heartbeat. The fidelity of these neural circuits in response to fluctuations in environmental conditions is essential for organismal survival. The specific ion channel profile of a neuron dictates its electrophysiological phenotype and is under homeostatic control, as channel proteins are constantly turning over in the membrane in response to internal and external stimuli. Neuronal function depends on ion channels and biophysical processes that are sensitive to external variables such as temperature, pH, and salinity. Nonetheless, the nervous system of the American lobster (Homarus americanus) is robust to global perturbations in these variables. The cardiac ganglion (CG), the CPG that controls the rhythmic activation of the heart in the lobster, has been shown to maintain function across a relatively wide, ecologically-relevant range of saline concentrations in the short-term. This study investigates whether individual neurons of the CG sense and compensate for long-term changes in extracellular ion concentration by controlling their ion channel mRNA abundances. To do this, I bathed the isolated CG in either 0.75x, 1.5x, or 1x (physiological) saline concentrations for 24 h. I then dissected out individual CG motor neurons, the pacemaker neurons, and sections of axonal projections and used single-cell RT-qPCR to measure relative mRNA abundances of several species of ion channels in these cells. I found that the CG maintained stable output with 24 h exposure to altered saline concentrations (0.75x and 1.5x), and that this stability may indeed be enabled by changes in mRNA abundances and correlated channel relationships.
Determining the influence of proximal Zeste binding sites and promoters on rates of transvection This record is embargoed.
- Embargo End Date: 2026-05-17
Date: 2023-01-01
Creator: Molly Henderson
Access: Embargoed
Peripheral modulation of cardiac contractions in the American lobster, Homarus americanus, by the peptide myosuppressin is mediated by effects on the cardiac muscle itself
Date: 2023-01-01
Creator: Isabel Stella Petropoulos
Access: Open access
- A substantial factor for behavioral flexibility is modulation — largely via neuropeptides — which occurs at multiple sites including neurons, muscles, and the neuromuscular junction (NMJ). Complex modulation distributed across multiple sites provides an interesting question: does modulation at multiple locations lead to greater dynamics than one receptor site alone? The cardiac neuromuscular system of the American lobster (Homarus americanus), driven by a central pattern generator called the cardiac ganglion (CG), is a model system for peptide modulation. The peptide myosuppressin (pQDLDHVFLRFamide) has been shown in the whole heart to decrease contraction frequency, largely due to its effects on the CG, as well as increase contraction amplitude by acting on periphery of the neuromuscular system, either at the cardiac muscle, the NMJ, or both. This set of experiments addresses the location(s) at which myosuppressin exerts its effects at the periphery. To elucidate myosuppressin’s effects on the cardiac muscle, the CG was removed, and muscle contractions were stimulated with L-glutamate while superfusing myosuppressin. Myosuppressin increased glutamate-evoked contraction amplitude in the isolated muscle, suggesting that myosuppressin exerts its peripheral effects directly on the cardiac muscle. To examine effects on the NMJ, excitatory junction potentials were evoked by stimulating of the motor nerve and intracellularly recording a single muscle fiber both in control saline and in the presence of myosuppressin. Myosuppressin did not modulate the amplitude of EJPs suggesting myosuppressin acts at the muscle and not at the NMJ, to cause an increase in contraction amplitude.
Characterization of Retinoic Acid Signaling During Tooth Morphogenesis and Evolution in Danio rerio This record is embargoed.
- Embargo End Date: 2028-05-17
Date: 2023-01-01
Creator: Lyn Stephanie Miranda Portillo
Access: Embargoed
The ELMO Family of Pectin Biosynthesis Scaffold Proteins Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2023-01-01
Creator: Margaret Elizabeth Weinstock
Access: Access restricted to the Bowdoin Community
An Investigation on Data Gaps in Scope 3 Emissions Accounting and Disclosure using 2010-2021 Carbon Disclosure Project (CDP) Questionnaire Responses This record is embargoed.
- Embargo End Date: 2027-05-17
Date: 2022-01-01
Creator: Samara Nassor
Access: Embargoed
The Role of ELMO5 in Arabidopsis thaliana Cell Adhesion
Date: 2022-01-01
Creator: Isabel Kristina Ball
Access: Open access
- Plant cell growth and development relies on proper cellular adhesion. As the extracellular matrix serves as the area of connection between two cells, its synthesis and maintenance are essential for cellular adhesion. The middle lamella region, the layer of the extracellular matrix between two adjacent cell walls, is diffuse with the polysaccharide pectin due to its delivery by Golgi vesicles early during cell division. A Ruthenium Red screen for cellular adhesion mutants identified the family of 5 ELMO proteins that are critical for proper cellular adhesion. To further our understanding of plant cellular adhesion and pathways of pectin synthesis and modification, this work investigates ELMO5. Plants homozygous for a T-DNA insertion in ELMO5 and a new deletion mutant allele generated using CRSPR do not have a cellular adhesion phenotype, suggesting it is either not critical for cellular adhesion or is redundant with another gene. Redundancy within the ELMO family is identified through the analysis of double mutants of elmo5 and each of the other four elmo genes. Both elmo1-/- elmo5-/-and elmo4-/- elmo5-/-mutants have a visibly worse cellular adhesion defect phenotype, suggesting partial redundancy through the ELMO family. The mutants are also rescued by growth on agar, pointing to the importance of turgor pressure and osmotic potential in modulating cellular adhesion. Both ELMO4 and ELMO5 were found to localize to the Golgi using a GFP fusion, consistent with a role for ELMOs as scaffold for pectin biosynthesis.
High Resolution Molecular Analysis of the Hedgehog Pathway in Tooth Development This record is embargoed.
- Embargo End Date: 2026-05-20
Date: 2021-01-01
Creator: Claire Christine Havig
Access: Embargoed
Chromatin-conformation differences in natural populations of D. melanogaster Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2026-06-01
Date: 2021-01-01
Creator: Nicholas J. Purchase
Access: Access restricted to the Bowdoin Community
Semaphorin-Induced Plasticity in the Nervous System of the Cricket, Gryllus bimaculatus
Date: 2021-01-01
Creator: Alicia G. Edwards
Access: Open access
- The adult auditory system of the cricket, Gryllus bimaculatus, exhibits a rare example of neuronal plasticity. Upon deafferentation, we observe medial dendrites that normally respect the midline of the PTG in the central nervous system sprouting across the boundary and forming synaptic connections with the contralateral auditory afferents. The Horch Lab has investigated key molecular factors that might play a causal role in this paradigm. Specifically, the protein Sema1a.2 comes from a guidance molecule family and has a role in developmental neuronal plasticity in other organisms. In this study, I explored the role of Sema1a.2 in the neuronal plasticity of the adult auditory system of the cricket by conducting a series of dsRNA knockdown experiments targeting Sema1a.2 followed by backfill procedures in which we iontophoresed dye into the Ascending Neurons (ANs) to visualize the anatomical effects of the knockdown experiments using confocal microscopy. We found that there were no significant differences between animals injected with dsRNA against GFP and Sema1a.2 volume, with respect to qualitative and quantitative data. However, we believe with an increase in cohort size, the trends observed, particularly the effect of Sema1a.2 knockdowns on CWM and CBM volumes, will become more pronounced and significant. Potential future pathways could include conducting double knockdowns of Sema1a.2 and Sema2a to observe if these two proteins are working together to create a more obvious effect on midline crossing and branching. Other options also include looking into other protein families that might be the causing factor in this rare phenomenon (toll-like receptors).