Michael N. Levy

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In the heart and in the blood vessel walls, complex adrenergic-cholinergic interactions occur both prejunctionally, at the level of the autonomic nerve terminals, and postjunctionally, at the level of the responding cells themselves. The principal prejunctional interaction appears to be an inhibition of the release of norepinephrine from adrenergic nerve(More)
Vagus nerve activity can change heart rate substantially within one cardiac cycle, and the chronotropic effects decay almost completely within one cardiac cycle after cessation of vagal activity. The ability of the vagus nerves to regulate heart rate beat by beat can be explained in large part by the speed at which the neural signal is transduced to a(More)
We developed a mathematical model of the underlying cellular mechanisms responsible for the changes in sinus cycle length (SCL) elicited by vagal stimulation in intact animals. The model incorporated a stimulation-mediated depletion of the releasable pool of acetylcholine (ACh) in the nerve endings, the in vitro reaction kinetics of acetylcholinesterase,(More)
An efficient and scalable discontinuous Galerkin shallow water model on the cubed sphere is developed by extending the transport scheme of Nair et al. (2005). The continuous flux form nonlinear shallow water equations in curvilinear coordinates are developed. Spatial discretization is a nodal basis set of Legendre polynomials. Fluxes along internal element(More)
ATP transiently increases the intracellular Ca2+ concentration in cardiac myocyte suspensions. Pretreatment with norepinephrine (NE) greatly potentiates the ATP response. We performed experiments on adult rat myocyte suspensions loaded with fura-2 to investigate the mechanism of NE potentiation. We found that forskolin (an activator of adenylate cyclase),(More)
Activation of protein kinase C (PKC) modulates the mobilization of intracellular Ca2+ induced by extracellular ATP in rat ventricular myocytes. Pretreatment of myocytes with PKC activators attenuated both the ATP-induced Ca2+ transient and the noradrenergic potentiation of the Ca2+ response. Various PKC activators decreased both the basal cAMP level and the(More)
High-resolution climate simulations require tremendous computing resources and can generate massive datasets. At present, preserving the data from these simulations consumes vast storage resources at institutions such as the National Center for Atmospheric Research (NCAR). The historical data generation trends are economically unsustainable, and storage(More)
In the isolated, blood-perfused, canine right atrium, stimulation of the intramural autonomic nerves evoked negative chronotropic and inotropic responses. The responses were not maintained at a constant level during tonic neural stimulation, but they tended to drift back toward their control levels. These time-dependent changes in the cardiac responses were(More)