Showing 21 - 30 of 116 Items

Miniature of Investigating the role of calcium-activated potassium channels in the stabilization of mammalian spinal locomotor activity
Investigating the role of calcium-activated potassium channels in the stabilization of mammalian spinal locomotor activity
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      Date: 2025-01-01

      Creator: Aeri Ko

      Access: Access restricted to the Bowdoin Community



        Microevolution of Candida albicans in Macrophages Restores Filamentation in a Nonfilamentous Mutant

        Date: 2014-12-01

        Creator: Anja Wartenberg, Jörg Linde, Ronny Martin, Maria Schreiner, Fabian, Horn, Ilse D. Jacobsen, Sabrina Jenull, Thomas Wolf, Karl Kuchler, Reinhard Guthke, Oliver Kurzai, Anja Forche, Christophe d'Enfert, Sascha Brunke, Bernhard Hube

        Access: Open access

        Following antifungal treatment, Candida albicans, and other human pathogenic fungi can undergo microevolution, which leads to the emergence of drug resistance. However, the capacity for microevolutionary adaptation of fungi goes beyond the development of resistance against antifungals. Here we used an experimental microevolution approach to show that one of the central pathogenicity mechanisms of C. albicans, the yeast-to-hyphae transition, can be subject to experimental evolution. The C. albicans cph1Δ/efg1Δ mutant is nonfilamentous, as central signaling pathways linking environmental cues to hyphal formation are disrupted. We subjected this mutant to constant selection pressure in the hostile environment of the macrophage phagosome. In a comparatively short time-frame, the mutant evolved the ability to escape macrophages by filamentation. In addition, the evolved mutant exhibited hyper-virulence in a murine infection model and an altered cell wall composition compared to the cph1Δ/efg1Δ strain. Moreover, the transcriptional regulation of hyphae-associated, and other pathogenicity-related genes became re-responsive to environmental cues in the evolved strain. We went on to identify the causative missense mutation via whole genome- and transcriptome-sequencing: a single nucleotide exchange took place within SSN3 that encodes a component of the Cdk8 module of the Mediator complex, which links transcription factors with the general transcription machinery. This mutation was responsible for the reconnection of the hyphal growth program with environmental signals in the evolved strain and was sufficient to bypass Efg1/Cph1-dependent filamentation. These data demonstrate that even central transcriptional networks can be remodeled very quickly under appropriate selection pressure.


        Miniature of Directed interactions during episodic memory
        Directed interactions during episodic memory
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        • Restriction End Date: 2025-06-01

          Date: 2020-01-01

          Creator: Rhianna J Patel

          Access: Access restricted to the Bowdoin Community



            Modulation of the stretch feedback pathway in the cardiac neuromuscular system of the American lobster, Homarus americanus

            Date: 2024-01-01

            Creator: Karin van Hassel

            Access: Open access

            The cardiac ganglion (CG) is a central pattern generator, a neural network that, when activated, produces patterned motor outputs such as breathing and walking. The CG induces the heart contractions of the American lobster, Homarus americanus, making the lobster heart neurogenic. In the American lobster, the CG is made up of nine neurons: four premotor pacemaker neurons that send signals to five motor neurons, causing bursts of action potentials from the motor neurons. These bursts cause cardiac muscle contractions that vary in strength based on the burst duration, frequency, and pattern. The activity of the CG is modulated by feedback pathways and neuromodulators, allowing for flexibility in the CG’s motor output and appropriate responses to changes in the animal’s environment. Two feedback pathways modulate the CG motor output, the excitatory cardiac muscle stretch and inhibitory nitric oxide feedback pathways. Despite our knowledge of the modulation of the CG by feedback pathways and neuromodulators separately, little is known about how neuromodulators influence the sensory feedback response to cardiac muscle stretch. I found one neuromodulator to modulate each phase of the stretch response differently, one neuromodulator to generally not affect the stretch response, and three neuromodulators to suppress the stretch response. These results suggest neuromodulators can act to produce flexibility in a CPG’s motor output, allowing the system to respond appropriately to changes in an organism’s environment, and allow for variation in CPG responses to different stimuli.


            The role of modulation on the pyloric neurons and the neuromuscular junction in a pattern generator-effector system

            Date: 2023-01-01

            Creator: Jackie Seddon

            Access: Open access

            Neuromodulation, the process of altering the electrical outputs of a neuron or neural circuit, allows an organism to control its physiological processes to meet the needs of both its internal and external environments. Previous work shows that the pyloric pattern of the kelp crab (Pugettia producta) stomatogastric nervous system (STNS) neurons responded to fewer neuromodulators than the Jonah crab (Cancer borealis). Since the kelp crab diet primarily eats kelp, it is possible that the movements of the foregut that control digestion may require less flexibility in functional output compared to an opportunistic feeder. To determine whether a reduced flexibility is correlated with diet, this study compared the modulatory responses in Pugettia to two other species of majoid crabs: Chionoecetes opilio and Libinia emarginata, which are both opportunistic feeders. Pooled data for this study found that Libinia and Chionoecetes responded to all twelve modulators tested. When considering the effect of modulators on stomatogastric ganglion (STG) motor outputs, we must consider whether these modulators also alter the excitatory junction potentials (EJPs) at the neuromuscular junction (NMJ), and whether there are differences in responses across species. To test this, the dorsal gastric nerve (dgn) was stimulated while recording intracellularly from the muscle fibers of the associated gm4 muscles. The NMJ of the gm4 in Cancer borealis did not appear to be broadly modulated, as only RPCH and CabTRP showed increases in amplitude, and RPCH decreased facilitation at 5 Hz.


            Miniature of The impact of plastic contaminants and neuroprotectants on spinal neural circuits controlling vertebrate locomotion
            The impact of plastic contaminants and neuroprotectants on spinal neural circuits controlling vertebrate locomotion
            This record is embargoed.
              • Embargo End Date: 2026-05-18

              Date: 2023-01-01

              Creator: Violet Louise Rizzieri

              Access: Embargoed



                Miniature of The role of pubertal hormones on female rats' sensitivity to acute ketamine treatment in an early-life-adversity model
                The role of pubertal hormones on female rats' sensitivity to acute ketamine treatment in an early-life-adversity model
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                    Date: 2024-01-01

                    Creator: Nuanxi (Sissi) Feng

                    Access: Access restricted to the Bowdoin Community



                      Miniature of Characterization and distribution of allatostatin type-C (AST-C) neuropeptides and receptors in crustaceans
                      Characterization and distribution of allatostatin type-C (AST-C) neuropeptides and receptors in crustaceans
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                          Date: 2016-05-01

                          Creator: Tess Lameyer

                          Access: Access restricted to the Bowdoin Community



                            Miniature of Exploring the functional role of theta oscillations in top-down control of episodic memory retrieval
                            Exploring the functional role of theta oscillations in top-down control of episodic memory retrieval
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                                Date: 2025-01-01

                                Creator: Emma F.B. Gibbens

                                Access: Access restricted to the Bowdoin Community



                                  Genomic plasticity of the human fungal pathogen Candida albicans

                                  Date: 2010-07-01

                                  Creator: Anna Selmecki, Anja Forche, Judith Berman

                                  Access: Open access

                                  The genomic plasticity of Candida albicans, a commensal and common opportunistic fungal pathogen, continues to reveal unexpected surprises. Once thought to be asexual, we now know that the organism can generate genetic diversity through several mechanisms, including mating between cells of the opposite or of the same mating type and by a parasexual reduction in chromosome number that can be accompanied by recombination events (2, 12, 14, 53, 77, 115). In addition, dramatic genome changes can appear quite rapidly in mitotic cells propagated in vitro as well as in vivo. The detection of aneuploidy in other fungal pathogens isolated directly from patients (145) and from environmental samples (71) suggests that variations in chromosome organization and copy number are a common mechanism used by pathogenic fungi to rapidly generate diversity in response to stressful growth conditions, including, but not limited to, antifungal drug exposure. Since cancer cells often become polyploid and/or aneuploid, some of the lessons learned from studies of genome plasticity in C. albicans may provide important insights into how these processes occur in higher-eukaryotic cells exposed to stresses such as anticancer drugs. © 2010, American Society for Microbiology.