Showing 3541 - 3550 of 5831 Items
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- Restriction End Date: 2026-06-01
Date: 2021-01-01
Creator: Aida Muratoglu
Access: Access restricted to the Bowdoin Community
Pheromones enhance somatosensory processing in newt brains through a vasotocin-dependent mechanism
Date: 2008-07-22
Creator: R. R. Thompson, P. S. Dickinson, J. D. Rose, K. A. Dakin, G. M., Civiello, A. Segerdahl, R. Bartlett
Access: Open access
- We tested whether the sex pheromones that stimulate courtship clasping in male roughskin newts do so, at least in part, by amplifying the somatosensory signals that directly trigger the motor pattern associated with clasping and, if so, whether that amplification is dependent on endogenous vasotocin (VT). Female olfactory stimuli increased the number of action potentials recorded in the medulla of males in response to tactile stimulation of the cloaca, which triggers the clasp motor reflex, as well as to tactile stimulation of the snout and hindlimb. That enhancement was blocked by exposing the medulla to a V1a receptor antagonist before pheromone exposure. However, the antagonist did not affect medullary responses to tactile stimuli in the absence of pheromone exposure, suggesting that pheromones amplify somatosensory signals by inducing endogenous VT release. The ability of VT to couple sensory systems together in response to social stimulation could allow this peptide to induce variable behavioural outcomes, depending on the immediate context of the social interaction and thus on the nature of the associated stimuli that are amplified. If widespread in vertebrates, this mechanism could account for some of the behavioural variability associated with this and related peptides both within and across species. © 2008 The Royal Society.
Long-term maintenance of channel distribution in a central pattern generator neuron by neuromodulatory inputs revealed by decentralization in organ culture
Date: 2001-09-15
Creator: Adi Mizrahi, Patsy S. Dickinson, Peter Kloppenburg, Valerie Fénelon, Deborah J., Baro, Ronald M. Harris-Warrick, Pierre Meyrand, John Simmers
Access: Open access
- Organotypic cultures of the lobster (Homarus gammarus) stomatogastric nervous system (STNS) were used to assess changes in membrane properties of neurons of the pyloric motor pattern-generating network in the long-term absence of neuromodulatory inputs to the stomatogastric ganglion (STG). Specifically, we investigated decentralization-induced changes in the distribution and density of the transient outward current, IA, which is encoded within the STG by the shal gene and plays an important role in shaping rhythmic bursting of pyloric neurons. Using an antibody against lobster shal K+ channels, we found shal immunoreactivity in the membranes of neuritic processes, but not somata, of STG neurons in 5 d cultured STNS with intact modulatory inputs. However, in 5 d decentralized STG, shal immunoreactivity was still seen in primary neurites but was likewise present in a subset of STG somata. Among the neurons displaying this altered shal localization was the pyloric dilator (PD) neuron, which remained rhythmically active in 5 d decentralized STG. Two-electrode voltage clamp was used to compare IA in synaptically isolated PD neurons in long-term decentralized STG and nondecentralized controls. Although the voltage dependence and kinetics of IA changed little with decentralization, the maximal conductance of IA in PD neurons increased by 43.4%. This increase was consistent with the decentralization-induced increase in shal protein expression, indicating an alteration in the density and distribution of functional A-channels. Our results suggest that, in addition to the short-term regulation of network function, modulatory inputs may also play a role, either directly or indirectly, in controlling channel number and distribution, thereby maintaining the biophysical character of neuronal targets on a long-term basis.
Quantification of dendritic and axonal growth after injury to the auditory system of the adult cricket gryllus bimaculatus
Date: 2013-09-27
Creator: Alexandra Pfister, Amy Johnson, Olaf Ellers, Hadley W. Horch
Access: Open access
- Dendrite and axon growth and branching during development are regulated by a complex set of intracellular and external signals. However, the cues that maintain or influence adult neuronal morphology are less well understood. Injury and deafferentation tend to have negative effects on adult nervous systems. An interesting example of injury-induced compensatory growth is seen in the cricket, Gryllus bimaculatus. After unilateral loss of an ear in the adult cricket, auditory neurons within the central nervous system (CNS) sprout to compensate for the injury. Specifically, after being deafferented, ascending neurons (AN-1 and AN-2) send dendrites across the midline of the prothoracic ganglion where they receive input from auditory afferents that project through the contralateral auditory nerve (N5). Deafferentation also triggers contralateral N5 axonal growth. In this study, we quantified AN dendritic and N5 axonal growth at 30 h, as well as at 3, 5, 7, 14, and 20 days after deafferentation in adult crickets. Significant differences in the rates of dendritic growth between males and females were noted. In females, dendritic growth rates were non-linear; a rapid burst of dendritic extension in the first few days was followed by a plateau reached at 3 days after deafferentation. In males, however, dendritic growth rates were linear, with dendrites growing steadily over time and reaching lengths, on average, twice as long as in females. On the other hand, rates of N5 axonal growth showed no significant sexual dimorphism and were linear. Within each animal, the growth rates of dendrites and axons were not correlated, indicating that independent factors likely influence dendritic and axonal growth in response to injury in this system. Our findings provide a basis for future study of the cellular features that allow differing dendrite and axon growth patterns as well as sexually dimorphic dendritic growth in response to deafferentation. © 2013 Pfister, Johnson, Ellers and Horch.
Entanglement sharing among quantum particles with more than two orthogonal states
Date: 2002-01-01
Creator: Kenneth A. Dennison, William K. Wootters
Access: Open access
- The entanglement sharing among quantum particles was discussed in a system consisting of n d-dimensional quantum particles. The entanglement between each pair was attempted to get optimized. A three particles system was also considered and results showed that the particles shared a greater fraction of their entanglement capacity as the dimension d increased.
Economic Costs of Elevated Public Debt Levels During Banking-Crisis Recessions
Date: 2021-01-01
Creator: Gavin T Shilling
Access: Open access
- The Great Recession of 2007 and 2008 exposed the risks of excessive borrowing. We learned the essential economic principle that greater leverage harbors greater risk. Although this global economic contraction was driven primarily by booming private credit expansion, economically inefficient incentives in the public sector, such as short-term reelection concerns, may lead politicians to engage in rash deficit- financed, fiscal spending. The primary purpose of this research is to assess the economic costs of heightened, preexisting government leverage on real economic outcomes during recessionary periods, focusing on both banking and non-banking crisis recessions. In both advanced economies and emerging economies, this study confirms that banking recessions are associated with more severe economic contractions and more persistent output declines than normal recessions. In advanced economies, GDP recovers quickly and strongly with expansionary and supportive fiscal policy during low debt recessions, even with depressed private investment. While GDP recovers slowly and weakly with less expansionary fiscal policy during high debt recessions, even with strong private investment. Thus, the social marginal benefit of public sector investment exceeds the social marginal benefit of private sector investment in advanced economies. In emerging economies, GDP recovers quickly and strongly with strong private investment during high debt recessions, even with weak fiscal spending. While GDP recovers slowly and weakly with depressed private investment during low debt recessions, even with expansionary and supportive fiscal policy. Thus, the social marginal benefit of private sector investment exceeds the social marginal benefit of public sector investment in emerging economies.
Acoustic measurements of the stripe and the bubble quantum Hall phase
Date: 2015-04-01
Creator: M. E. Msall, W. Dietsche
Access: Open access
- We launch surface acousticwaves (SAW) along both the and the directions of aHall bar and measure the anisotropic conductivity in a high purity GaAs two-dimensional electron system in the quantum Hall regime of the stripe and the bubble phases. In the anisotropic stripe phase,SAW propagating along the 'easy' direction sense a compressible behavior (finite resistance)which is seen in standard transportmeasurement only if current flows along the 'hard' direction. In the isotropic bubble phase, the SAW data show compressible behavior in both directions, in marked contrast to the incompressible quantum Hall behavior seen in transport measurements. These results challenge models that assume that both the stripe and the bubble phase consist of incompressible domains and raise important questions about the role of domain boundaries in SAW propagation.