599 research outputs found
R-PEP-27, a Potent Renin Inhibitor, Decreases Plasma Angiotensin II and Blood Pressure in Normal Volunteers
The hemodynamic and humoral effects of the specific human renin inhibitor R-PEP-27 were studied in six normal human subjects on low and high sodium intake diets. An intravenous infusion of R-PEP-27 (0.5 to 16 μg/min/kg body wt) reduced blood pressure in a dose-dependent fashion; the mean arterial blood pressure at the end of the infusion fell from 128 ± 4/83 ± 4 to 119 ± 3/71 ± 3 mm Hg (mean ± SEM) (P < .01) during the low sodium intake diet. R-PEP-27 had no effect on blood pressure during the high sodium intake diet. R-PEP-27 significantly reduced plasma angiotensin II and aldosterone concentrations. The temporal response to R-PEP-27 suggests that it is a shortlived although highly potent competitive inhibitor of renin; this peptide is a valuable and specific physiologic probe of the renin-angiotensin system. Am J Hypertens 1994;7:295-30
R-PEP-27, a potent renin inhibitor, decreases plasma angiotensin II and blood pressure in normal volunteers
The hemodynamic and humoral effects of the specific human renin inhibitor R-PEP-27 were studied in six normal human subjects on low and high sodium intake diets. An intravenous infusion of R-PEP-27 (0.5 to 16 micrograms/min/kg body wt) reduced blood pressure in a dose-dependent fashion; the mean arterial blood pressure at the end of the infusion fell from 128 +/- 4/83 +/- 4 to 119 +/- 3/71 +/- 3 mm Hg (mean +/- SEM) (P < .01) during the low sodium intake diet. R-PEP-27 had no effect on blood pressure during the high sodium intake diet. R-PEP-27 significantly reduced plasma angiotensin II and aldosterone concentrations. The temporal response to R-PEP-27 suggests that it is a short-lived although highly potent competitive inhibitor of renin; this peptide is a valuable and specific physiologic probe of the renin-angiotensin system
Localized states in strong magnetic field: resonant scattering and the Dicke effect
We study the energy spectrum of a system of localized states coupled to a 2D
electron gas in strong magnetic field. If the energy levels of localized states
are close to the electron energy in the plane, the system exhibits a kind of
collective behavior analogous to the Dicke effect in optics. The latter
manifests itself in ``trapping'' of electronic states by localized states. At
the same time, the electronic density of states develops a gap near the
resonance. The gap and the trapping of states appear to be complementary and
reflect an intimate relation between the resonant scattering and the Dicke
effect. We reveal this relation by presenting the exact solution of the problem
for the lowest Landau level. In particular, we show that in the absence of
disorder the system undergoes a phase transition at some critical concentration
of localized states.Comment: 28 pages + 9 fig
Active Brownian Particles. From Individual to Collective Stochastic Dynamics
We review theoretical models of individual motility as well as collective
dynamics and pattern formation of active particles. We focus on simple models
of active dynamics with a particular emphasis on nonlinear and stochastic
dynamics of such self-propelled entities in the framework of statistical
mechanics. Examples of such active units in complex physico-chemical and
biological systems are chemically powered nano-rods, localized patterns in
reaction-diffusion system, motile cells or macroscopic animals. Based on the
description of individual motion of point-like active particles by stochastic
differential equations, we discuss different velocity-dependent friction
functions, the impact of various types of fluctuations and calculate
characteristic observables such as stationary velocity distributions or
diffusion coefficients. Finally, we consider not only the free and confined
individual active dynamics but also different types of interaction between
active particles. The resulting collective dynamical behavior of large
assemblies and aggregates of active units is discussed and an overview over
some recent results on spatiotemporal pattern formation in such systems is
given.Comment: 161 pages, Review, Eur Phys J Special-Topics, accepte
Fundamental Limits on Wavelength, Efficiency and Yield of the Charge Separation Triad
In an attempt to optimize a high yield, high efficiency artificial photosynthetic protein we have discovered unique energy and spatial architecture limits which apply to all light-activated photosynthetic systems. We have generated an analytical solution for the time behavior of the core three cofactor charge separation element in photosynthesis, the photosynthetic cofactor triad, and explored the functional consequences of its makeup including its architecture, the reduction potentials of its components, and the absorption energy of the light absorbing primary-donor cofactor. Our primary findings are two: First, that a high efficiency, high yield triad will have an absorption frequency more than twice the reorganization energy of the first electron transfer, and second, that the relative distance of the acceptor and the donor from the primary-donor plays an important role in determining the yields, with the highest efficiency, highest yield architecture having the light absorbing cofactor closest to the acceptor. Surprisingly, despite the increased complexity found in natural solar energy conversion proteins, we find that the construction of this central triad in natural systems matches these predictions. Our analysis thus not only suggests explanations for some aspects of the makeup of natural photosynthetic systems, it also provides specific design criteria necessary to create high efficiency, high yield artificial protein-based triads
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