Showing 1 - 10 of 21 Items
Mechanisms underlying variable responses to isoforms of the neuropeptide C-type allatostatin (AST-C) in the cardiac neuromuscular system of the American lobster, Homarus americanus
Date: 2019-01-01
Creator: Evalyn Mackenzie
Access: Open access
- Central Pattern Generators (CPGs) are neural networks that produce steady, rhythmic patterned outputs that activate particular muscles and consequently create recurrent rhythmic movements. The cardiac ganglion (CG) of the American lobster (Homarus americanus) is a useful model system for the study of CPGs. Neuropeptides modulate cardiac contractions driven by the CG in H. americanus and accordingly elicit a range of effects. Post-translational modifications such as amidation can impact function of a peptide neuromodulator. C-type allatostatins (AST-Cs) are a group of neuropeptides that modulate the cardiac neuromuscular system of H. americanus. The objective of this study was to determine what structural aspects of the peptides were responsible for the similarity in responses elicited by AST-C I and AST-C III and the difference in responses evoked by AST-C II in comparison. AST-C I and AST-C III are not C-terminally amidated, whereas AST-C II is C-terminally amidated. We first hypothesized that amidated AST-C peptides would evoke similar responses to one another in contraction amplitude and frequency. Our second hypothesis was that exchanging the amino acids alanine and tyrosine at a specific location in AST-C II and AST-C III would affect the conformation of the peptide, and consequently impact peptide binding and elicit different effects. In contrast to our predictions, we did not see similar responses evoked by all amidated or all non-amidated peptides among lobsters. In support of our second hypothesis, there was a significant difference in percent change in contraction amplitude elicited among AST-C II Y, AST-C II and AST-C III.
Role of the Dopamine Subtype 1 Receptor (D1R) Modulation of the Ih Current in Rhythmic Spinal Mammalian Motor Networks Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2025-06-01
Date: 2022-01-01
Creator: Grace Soeun Lee
Access: Access restricted to the Bowdoin Community
The Current Hunt for Nitric Oxide's Effects on the Homarus americanus Cardiac Ganglion
Date: 2022-01-01
Creator: Joanna Lin
Access: Open access
- The crustacean heartbeat is produced and modulated by the cardiac ganglion (CG), a central pattern generator. In the American lobster, Homarus americanus, the CG consists of 4 small premotor cells (SCs) that electrically and chemically synapse onto 5 large motor cells (LCs). Rhythmic driver potentials in the SCs generate bursting in the LCs, which elicit downstream cardiac muscle contractions that are essential for physiological functions. Endogenous neuromodulators mediate changes in the CG to meet homeostatic demands caused by environmental stressors. Nitric oxide (NO), a gaseous neuromodulator, inhibits the lobster CG. Heart contractions release NO, which directly decreases the CG burst frequency and indirectly decreases the heartbeat amplitude, to mediate negative feedback. I investigated NO’s inhibitory effects on the CG to further understand the mechanisms underlying intrinsic feedback. Using extracellular recordings, I examined NO modulation of the SCs and LCs when coupled in the intact circuit and when firing independently in the ligatured preparation. Using two-electrode voltage clamp, I additionally analyzed the modulation of channel kinetics. Based on previous studies, I hypothesized that NO decreases the burst frequency of the LCs and SCs by modulating conductance properties of the voltage-gated A-type potassium current (IA). My data showed that NO decreased the burst frequency in the LCs and the burst duration in the SCs in a state-dependent manner. Furthermore, NO increased the IA inactivation time constant to decrease the LCs’ burst frequency. Thus, NO mediated inhibitory effects on cardiac output by differentially targeting both cell types and altering the IA current kinetics.
Identifying crustacean neuropeptides and precursor-related peptides by LC/MS: An investigation of strategies for extraction and orthogonal separations Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2028-06-01
Date: 2023-01-01
Creator: Emily Grace Herndon
Access: Access restricted to the Bowdoin Community
Efficacy of Curcumin as a Neuroprotectant Against Dibutyl Phthalate (DBP) - Induced Effects on the Mammalian Spinal Cord Locomotor Neural Network This record is embargoed.
- Embargo End Date: 2027-05-15
Date: 2024-01-01
Creator: Eliza Schotten
Access: Embargoed
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).
Non-genomic effects of steroids on teleost fish olfaction: behavioral and anatomical approaches Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2020-01-01
Creator: Leah B Kratochvil
Access: Access restricted to the Bowdoin Community
Exploring sex-specific and developmental outcomes of early life adversity on DNA methylation in parvalbumin-containing interneurons Access to this record is restricted to members of the Bowdoin community. Log in here to view.
Date: 2023-01-01
Creator: Emma Straw Noel
Access: Access restricted to the Bowdoin Community
The sex specific effects of acute ketamine treatment on parvalbumin and anxiety and depression following early life adversity Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2025-06-01
Date: 2022-01-01
Creator: Seneca N. Ellis
Access: Access restricted to the Bowdoin Community
Characterizing Toll Receptors in the Mediterranean Cricket Access to this record is restricted to members of the Bowdoin community. Log in here to view.
- Restriction End Date: 2025-06-01
Date: 2022-01-01
Creator: Warsameh Bulhan
Access: Access restricted to the Bowdoin Community