Showing 1491 - 1500 of 2039 Items
Inter-animal variability in the effects of C-type allatostatin on the cardiac neuromuscular system in the lobster Homarus americanus
Date: 2012-07-01
Creator: Teerawat Wiwatpanit
Brian Powers
Patsy S. Dickinson
Access: Open access
- Although the global effects of many modulators on pattern generators are relatively consistent among preparations, modulators can induce different alterations in different preparations. We examined the mechanisms that underlie such variability in the modulatory effects of the peptide C-type allatostatin (C-AST; pQIRYHQCYFNPISCF) on the cardiac neuromuscular system of the lobster Homarus americanus. Perfusion of C-AST through the semi-intact heart consistently decreased the frequency of ongoing contractions. However, the effect of C-AST on contraction amplitude varied between preparations, decreasing in some preparations and increasing in others. To investigate this variable effect, we examined the effects of C-AST both peripherally and centrally. When contractions of the myocardium were elicited by controlled stimuli, C-AST did not alter heart contraction at the periphery (myocardium or neuromuscular junction) in any hearts. However, when applied either to the semi-intact heart or to the cardiac ganglion (CG) isolated from hearts that responded to C-AST with increased contraction force, C-AST increased both motor neuron burst duration and the number of spikes per burst by about 25%. In contrast, CG output was increased only marginally in hearts that responded to C-AST with a decrease in contraction amplitude, suggesting that the decrease in amplitude in those preparations resulted from decreased peripheral facilitation. Our data suggest that the differential effects of a single peptide on the cardiac neuromuscular system are due solely to differential effects of the peptide on the pattern generator; the extent to which the peptide induces increased burst duration is crucial in determining its overall effect on the system. © 2012. Published by The Company of Biologists Ltd.
One-armed spiral instability in differentially rotating stars
Date: 2003-01-01
Creator: M. Saijo
T.W. Baumgarte
S.L. Shapiro
Access: Open access
The contributions of motor neuronal and muscle modulation to behavioral flexibility in the stomatogastric system
Date: 1995-12-01
Creator: Patsy S. Dickinson
Access: Open access
- The stomatogastric nervous system of crustaceans, which controls the four parts ofthe foregut, is subject to modulation at all levels, sensory, central and motor. Modulation of the central pattern generators, which are themselves made up largely of motor neurons, providesfor increased behavioral flexibility in a variety of ways. First, each of the pattern generators can be reconfigured to give multiple outputs. Second, the "boundaries" of the different pattern generators are in fact somewhat fluid, so that the neuronal composition of the pattern generators can be altered. For example, neurons can switch from one pattern generator toanother, or two or more pattern generators can fuse to generate an entirely new pattern and thereby produce a new behavior. The mechanisms responsible for many of these modulations include alterations of both intrinsic properties and synaptic interactions between neurons. In addition, the alteration of membrane properties contributes more directly to the behavioral output by changing action potential frequency. Finally, the muscles of the stomatogastric system can themselves be modulated, with the cpvl muscle, for example, becoming an endogenous oscillator in the presence of either dopamine or the peptide FMRFamide. © 1995 by the American Society of Zoologists.
Trumpet slices of the Schwarzschild-Tangherlini spacetime
Date: 2010-12-01
Creator: Kenneth A. Dennison
John P. Wendell
Thomas W. Baumgarte
J. David Brown
Access: Open access
- We study families of time-independent maximal and 1+log foliations of the Schwarzschild-Tangherlini spacetime, the spherically symmetric vacuum black hole solution in D spacetime dimensions, for D≥4. We identify special members of these families for which the spatial slices display a trumpet geometry. Using a generalization of the 1+log slicing condition that is parameterized by a constant n we recover the results of Nakao, Abe, Yoshino, and Shibata in the limit of maximal slicing. We also construct a numerical code that evolves the Baumgarte-Shapiro-Shibata-Nakamura equations for D=5 in spherical symmetry using moving-puncture coordinates and demonstrate that these simulations settle down to the trumpet solutions. © 2010 The American Physical Society.
Inelastic channels in the electroweak symmetry-breaking sector
Date: 1992-10-29
Creator: S. G. Naculich
C. P. Yuan
Access: Open access
- It has been argued that if light Higgs bosons do not exist then the self-interactions of W's become strong in the TeV region and can be observed in longitudinal WW scattering. We present a model with many inelastic channels in the WW scattering process, corresponding to the creation of heavy fermion pairs. The presence of these heavy fermions affects the elastic scattering of W's by propagating in loops, greatly reducing the amplitudes in some charge channels. Consequently, the symmetry-breaking sector cannot be fully explored by using, for example, the W+W+ mode alone; all WW→WW scattering modes must be measured. © 1992.
Risks of multimodal signaling: Bat predators attend to dynamic motion in frog sexual displays
Date: 2014-09-01
Creator: Wouter Halfwerk
Marjorie M. Dixon
Kristina J. Ottens
Ryan C. Taylor
Michael J., Ryan
Rachel A. Page
Patricia L. Jones
Access: Open access
- Many sexual displays contain multiple components that are received through a variety of sensory modalities. Primary and secondary signal components can interact to induce novel receiver responses and become targets of sexual selection as complex signals. However, predators can also use these complex signals for prey assessment, which may limit the evolution of elaborate sexual signals. We tested whether a multimodal sexual display of the male túngara frog (Physalaemus pustulosus) increases predation risk from the fringe-lipped bat (Trachops cirrhosus) when compared with a unimodal display. We gave bats a choice to attack one of two frog models: a model with a vocal sac moving in synchrony with a mating call (multisensory cue), or a control model with the call but no vocal sac movement (unimodal cue). Bats preferred to attack the model associated with the multimodal display. Furthermore, we determined that bats perceive the vocal sac using echolocation rather than visual cues. Our data illustrate the costs associated with multimodal signaling and that sexual and natural selection pressures on the same trait are not always mediated through the same sensory modalities. These data are important when considering the role of environmental fluctuations on signal evolution as different sensory modalities will be differentially affected.
Bounding the number of cycles of O.D.E.S in Rn
Date: 2001-01-01
Creator: M. Farkas
P. Van Den Driessche
M. L. Zeeman
Access: Open access
- Criteria are given under which the boundary of an oriented surface does not consist entirely of trajectories of the C1 differential equation ẋ = f(x) in Rn. The special case of an annulus is further considered, and the criteria are used to deduce sufficient conditions for the differential equation to have at most one cycle. A bound on the number of cycles on surfaces of higher connectivity is given by similar conditions. ©2000 American Mathematical Society.
Origami-based impact mitigation via rarefaction solitary wave creation
Date: 2019-01-01
Creator: Hiromi Yasuda
Yasuhiro Miyazawa
Efstathios G. Charalampidis
Christopher Chong
Panayotis G., Kevrekidis
Jinkyu Yang
Access: Open access
- The principles underlying the art of origami paper folding can be applied to design sophisticated metamaterials with unique mechanical properties. By exploiting the flat crease patterns that determine the dynamic folding and unfolding motion of origami, we are able to design an origami-based metamaterial that can form rarefaction solitary waves. Our analytical, numerical, and experimental results demonstrate that this rarefaction solitary wave overtakes initial compressive strain waves, thereby causing the latter part of the origami structure to feel tension first instead of compression under impact. This counterintuitive dynamic mechanism can be used to create a highly efficient-yet reusable-impact mitigating system without relying on material damping, plasticity, or fracture.
A simple polymerase chain reaction-based method for the construction of recombinase-mediated cassette exchange donor vectors
Date: 2008-11-01
Creator: Jack R. Bateman
C. Ting Wu
Access: Open access
- Here we describe a simple method for generating donor vectors suitable for targeted transgenesis via recombinase-mediated cassette exchange (RMCE) using the ΦC31 integrase. This PCR-based strategy employs small attB "tails" on the primers used to amplify a sequence of interest, permitting the rapid creation of transgenes for in vivo analysis. Copyright © 2008 by the Genetics Society of America.
Inbreeding shapes the evolution of marine invertebrates
Date: 2020-05-01
Creator: Kevin C. Olsen
Will H. Ryan
Alice A. Winn
Ellen T. Kosman
Jose A., Moscoso
Stacy A. Krueger-Hadfield
Scott C. Burgess
David B. Carlon
Richard K. Grosberg
Susan Kalisz
Don R. Levitan
Access: Open access
- Inbreeding is a potent evolutionary force shaping the distribution of genetic variation within and among populations of plants and animals. Yet, our understanding of the forces shaping the expression and evolution of nonrandom mating in general, and inbreeding in particular, remains remarkably incomplete. Most research on plant mating systems focuses on self-fertilization and its consequences for automatic selection, inbreeding depression, purging, and reproductive assurance, whereas studies of animal mating systems have often assumed that inbreeding is rare, and that natural selection favors traits that promote outbreeding. Given that many sessile and sedentary marine invertebrates and marine macroalgae share key life history features with seed plants (e.g., low mobility, modular construction, and the release of gametes into the environment), their mating systems may be similar. Here, we show that published estimates of inbreeding coefficients (FIS) for sessile and sedentary marine organisms are similar and at least as high as noted in terrestrial seed plants. We also found that variation in FIS within invertebrates is related to the potential to self-fertilize, disperse, and choose mates. The similarity of FIS for these organismal groups suggests that inbreeding could play a larger role in the evolution of sessile and sedentary marine organisms than is currently recognized. Specifically, associations between traits of marine invertebrates and FIS suggest that inbreeding could drive evolutionary transitions between hermaphroditism and separate sexes, direct development and multiphasic life cycles, and external and internal fertilization.