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N H Holstein-rathlou - One of the best experts on this subject based on the ideXlab platform.
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Modeling of Kidney Hemodynamics: Probability-Based Topology of an Arterial Network.
Public Library of Science (PLoS), 2016Co-Authors: N H Holstein-rathlou, Donald J. Marsh, Dmitry E. Postnov, Thomas H Braunstein, Erik A Martens, Olga SosnovtsevaAbstract:Through regulation of the extracellular fluid volume, the kidneys provide important long-term regulation of blood pressure. At the level of the individual functional unit (the nephron), pressure and flow control involves two different mechanisms that both produce oscillations. The Nephrons are arranged in a complex branching structure that delivers blood to each nephron and, at the same time, provides a basis for an interaction between adjacent Nephrons. The functional consequences of this interaction are not understood, and at present it is not possible to address this question experimentally. We provide experimental data and a new modeling approach to clarify this problem. To resolve details of microvascular structure, we collected 3D data from more than 150 afferent arterioles in an optically cleared rat kidney. Using these results together with published micro-computed tomography (μCT) data we develop an algorithm for generating the renal arterial network. We then introduce a mathematical model describing blood flow dynamics and nephron to nephron interaction in the network. The model includes an implementation of electrical signal propagation along a vascular wall. Simulation results show that the renal arterial architecture plays an important role in maintaining adequate pressure levels and the self-sustained dynamics of Nephrons
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Electrotonic vascular signal conduction and nephron synchronization.
American Journal of Physiology-renal Physiology, 2008Co-Authors: Donald J. Marsh, Ildiko Toma, Olga Sosnovtseva, Janos Peti-peterdi, N H Holstein-rathlouAbstract:Tubuloglomerular feedback (TGF) and the myogenic mechanism control afferent arteriolar diameter in each nephron and regulate blood flow. Both mechanisms generate self-sustained oscillations, the oscillations interact, TGF modulates the frequency and amplitude of the myogenic oscillation, and the oscillations synchronize; a 5:1 frequency ratio is the most frequent. TGF oscillations synchronize in nephron pairs supplied from a common cortical radial artery, as do myogenic oscillations. We propose that electrotonic vascular signal propagation from one juxtaglomerular apparatus interacts with similar signals from other Nephrons to produce synchronization. We tested this idea in tubular-vascular preparations from mice. Vascular smooth muscle cells were loaded with a fluorescent voltage-sensitive dye; fluorescence intensity was measured with confocal microscopy. Perfusion of the thick ascending limb activated TGF and depolarized afferent arteriolar smooth muscle cells. The depolarization spread to the cortical radial artery and other afferent arterioles and declined with distance from the perfused juxtaglomerular apparatus, consistent with electrotonic vascular signal propagation. With a mathematical model of two coupled Nephrons, we estimated the conductance of nephron coupling by fitting simulated vessel diameters to experimental data. With this value, we simulated nephron pairs to test for synchronization. In single-nephron simulations, the frequency of the TGF oscillation varied with nephron length. Coupling Nephrons of different lengths forced TGF frequencies of both pair members to converge to a common value. The myogenic oscillations also synchronized, and the synchronization between the TGF and the myogenic oscillations showed an increased stability against parameter perturbations. Electronic vascular signal propagation is a plausible mechanism for nephron synchronization. Coupling increased the stability of the various oscillations.
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Vascular coupling induces synchronization, quasiperiodicity, and chaos in a nephron tree.
Chaos, 2007Co-Authors: Donald J. Marsh, Olga Sosnovtseva, Erik Mosekilde, N H Holstein-rathlouAbstract:The paper presents a study of synchronization phenomena in a system of 22 Nephrons supplied with blood from a common cortical radial artery. The Nephrons are assumed to interact via hemodynamic and vascularly propagated coupling, both mediated by vascular connections. Using anatomic and physiological criteria, the Nephrons are divided into groups: cortical Nephrons and medullary Nephrons with short, intermediate and long Henle loops. Within each of these groups the delay parameters of the internal feedback regulation are given a random component to represent the internephron variability. For parameters that generate simple limit cycle dynamics in the pressure and flow regulation of single Nephrons, the ensemble of coupled Nephrons showed steady state, quasiperiodic or chaotic dynamics, depending on the interaction strengths and the arterial blood pressure. When the solutions were either quasiperiodic or chaotic, cortical Nephrons synchronized to a single frequency, but the longer medullary Nephrons formed two clusters with different frequencies. Under no physiologically realistic combination of parameters did all Nephrons assume a common frequency. Our results suggest a greater variability in the nephron dynamics than is apparent from measurements performed on cortical Nephrons only. This variability may explain the development of chaotic dynamics in tubular pressure records from hypertensive rats.
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Bimodal dynamics in nephron autoregulation
2003 IEEE International Workshop on Workload Characterization (IEEE Cat. No.03EX775), 2003Co-Authors: Olga Sosnovtseva, Erik Mosekilde, Alexey N. Pavlov, N H Holstein-rathlouAbstract:The individual functional unit of the kidney (the nephron) displays oscillations in its pressure and flow regulation at two different time scales: fast oscillations associated with a myogenic dynamics of the afferent arteriole, and slower oscillations arising from a delay in the tubuloglomerular feedback. We investigate the intra- and inter-nephron entrainment of the two time-scales. Besides full synchronization, both wavelet analyses of experimental data and numerical simulations reveal a partial entrainment in which neighboring Nephrons attain a state of chaotic synchronization with respect to their slow dynamics, but the fast dynamics remain desynchronized.
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Nonlinear Phenomena in Nephron-Nephron Interaction
Synchronization: Theory and Application, 2003Co-Authors: Erik Mosekilde, Olga Sosnovtseva, N H Holstein-rathlouAbstract:By controling the excretion of water and salts, the kidneys play an important role in regulating the blood pressure and maintaining a proper environment for the cells of the body. This control depends to a large extent on mechanisms that are associated with the individual functional unit, the nephron. However, a variety of cooperative phenomena arising through interactions among the Nephrons may also be important. The purpose of this chapter is to present experimental evidence for a coupling between Nephrons that are connected via a common piece of afferent arteriole, to develop a mathematical model that can account for the observed synchronization phenomena, and to discuss the possible physiological significance of these phenomena. We are particularly interested in synchronization effects that can occur among neighboring Nephrons that individually display irregular (or chaotic) dynamics in their pressure and flow regulation.
Donald J. Marsh - One of the best experts on this subject based on the ideXlab platform.
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Modeling of Kidney Hemodynamics: Probability-Based Topology of an Arterial Network.
Public Library of Science (PLoS), 2016Co-Authors: N H Holstein-rathlou, Donald J. Marsh, Dmitry E. Postnov, Thomas H Braunstein, Erik A Martens, Olga SosnovtsevaAbstract:Through regulation of the extracellular fluid volume, the kidneys provide important long-term regulation of blood pressure. At the level of the individual functional unit (the nephron), pressure and flow control involves two different mechanisms that both produce oscillations. The Nephrons are arranged in a complex branching structure that delivers blood to each nephron and, at the same time, provides a basis for an interaction between adjacent Nephrons. The functional consequences of this interaction are not understood, and at present it is not possible to address this question experimentally. We provide experimental data and a new modeling approach to clarify this problem. To resolve details of microvascular structure, we collected 3D data from more than 150 afferent arterioles in an optically cleared rat kidney. Using these results together with published micro-computed tomography (μCT) data we develop an algorithm for generating the renal arterial network. We then introduce a mathematical model describing blood flow dynamics and nephron to nephron interaction in the network. The model includes an implementation of electrical signal propagation along a vascular wall. Simulation results show that the renal arterial architecture plays an important role in maintaining adequate pressure levels and the self-sustained dynamics of Nephrons
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Electrotonic vascular signal conduction and nephron synchronization.
American Journal of Physiology-renal Physiology, 2008Co-Authors: Donald J. Marsh, Ildiko Toma, Olga Sosnovtseva, Janos Peti-peterdi, N H Holstein-rathlouAbstract:Tubuloglomerular feedback (TGF) and the myogenic mechanism control afferent arteriolar diameter in each nephron and regulate blood flow. Both mechanisms generate self-sustained oscillations, the oscillations interact, TGF modulates the frequency and amplitude of the myogenic oscillation, and the oscillations synchronize; a 5:1 frequency ratio is the most frequent. TGF oscillations synchronize in nephron pairs supplied from a common cortical radial artery, as do myogenic oscillations. We propose that electrotonic vascular signal propagation from one juxtaglomerular apparatus interacts with similar signals from other Nephrons to produce synchronization. We tested this idea in tubular-vascular preparations from mice. Vascular smooth muscle cells were loaded with a fluorescent voltage-sensitive dye; fluorescence intensity was measured with confocal microscopy. Perfusion of the thick ascending limb activated TGF and depolarized afferent arteriolar smooth muscle cells. The depolarization spread to the cortical radial artery and other afferent arterioles and declined with distance from the perfused juxtaglomerular apparatus, consistent with electrotonic vascular signal propagation. With a mathematical model of two coupled Nephrons, we estimated the conductance of nephron coupling by fitting simulated vessel diameters to experimental data. With this value, we simulated nephron pairs to test for synchronization. In single-nephron simulations, the frequency of the TGF oscillation varied with nephron length. Coupling Nephrons of different lengths forced TGF frequencies of both pair members to converge to a common value. The myogenic oscillations also synchronized, and the synchronization between the TGF and the myogenic oscillations showed an increased stability against parameter perturbations. Electronic vascular signal propagation is a plausible mechanism for nephron synchronization. Coupling increased the stability of the various oscillations.
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Vascular coupling induces synchronization, quasiperiodicity, and chaos in a nephron tree.
Chaos, 2007Co-Authors: Donald J. Marsh, Olga Sosnovtseva, Erik Mosekilde, N H Holstein-rathlouAbstract:The paper presents a study of synchronization phenomena in a system of 22 Nephrons supplied with blood from a common cortical radial artery. The Nephrons are assumed to interact via hemodynamic and vascularly propagated coupling, both mediated by vascular connections. Using anatomic and physiological criteria, the Nephrons are divided into groups: cortical Nephrons and medullary Nephrons with short, intermediate and long Henle loops. Within each of these groups the delay parameters of the internal feedback regulation are given a random component to represent the internephron variability. For parameters that generate simple limit cycle dynamics in the pressure and flow regulation of single Nephrons, the ensemble of coupled Nephrons showed steady state, quasiperiodic or chaotic dynamics, depending on the interaction strengths and the arterial blood pressure. When the solutions were either quasiperiodic or chaotic, cortical Nephrons synchronized to a single frequency, but the longer medullary Nephrons formed two clusters with different frequencies. Under no physiologically realistic combination of parameters did all Nephrons assume a common frequency. Our results suggest a greater variability in the nephron dynamics than is apparent from measurements performed on cortical Nephrons only. This variability may explain the development of chaotic dynamics in tubular pressure records from hypertensive rats.
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Magnitude of TGF-initiated nephron-nephron interactions is increased in SHR
American Journal of Physiology-renal Physiology, 1995Co-Authors: Yu-ming Chen, Kay-pong Yip, Donald J. Marsh, N H Holstein-rathlouAbstract:We compared the tubuloglomerular feedback (TGF)-initiated nephron-nephron interaction in spontaneously hypertensive rats (SHR) and normotensive Sprague-Dawley (SD) rats. Interaction strength was assessed by measuring stop-flow pressure (delta SFP) responses in pairs of Nephrons, where only one nephron of the pair was microperfused. The vascular connection was determined from casts of the Nephrons and vessels; length of arteriolar separation between the two glomeruli was measured on the casts. When microperfusion rate was increased from 5 to 50 nl/min, delta SFP in perfused Nephrons was 10.6 +/- 0.6 and 10.2 +/- 0.7 mmHg [not significant (NS)] in SD and SHR, respectively. In the matched unperfused Nephrons from the same cortical radial artery, delta SFP was 1.3 +/- 0.2 and 2.9 +/- 0.7 mmHg (P < 0.05) in SD and SHR. When the perfused and unperfused nephron originated from different cortical radial arteries, delta SFP in the unperfused Nephrons was -0.1 +/- 0.2 and 0.0 +/- 0.3 mmHg (NS) in SD and SHR, respec...
Olga Sosnovtseva - One of the best experts on this subject based on the ideXlab platform.
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Modeling of Kidney Hemodynamics: Probability-Based Topology of an Arterial Network.
Public Library of Science (PLoS), 2016Co-Authors: N H Holstein-rathlou, Donald J. Marsh, Dmitry E. Postnov, Thomas H Braunstein, Erik A Martens, Olga SosnovtsevaAbstract:Through regulation of the extracellular fluid volume, the kidneys provide important long-term regulation of blood pressure. At the level of the individual functional unit (the nephron), pressure and flow control involves two different mechanisms that both produce oscillations. The Nephrons are arranged in a complex branching structure that delivers blood to each nephron and, at the same time, provides a basis for an interaction between adjacent Nephrons. The functional consequences of this interaction are not understood, and at present it is not possible to address this question experimentally. We provide experimental data and a new modeling approach to clarify this problem. To resolve details of microvascular structure, we collected 3D data from more than 150 afferent arterioles in an optically cleared rat kidney. Using these results together with published micro-computed tomography (μCT) data we develop an algorithm for generating the renal arterial network. We then introduce a mathematical model describing blood flow dynamics and nephron to nephron interaction in the network. The model includes an implementation of electrical signal propagation along a vascular wall. Simulation results show that the renal arterial architecture plays an important role in maintaining adequate pressure levels and the self-sustained dynamics of Nephrons
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Electrotonic vascular signal conduction and nephron synchronization.
American Journal of Physiology-renal Physiology, 2008Co-Authors: Donald J. Marsh, Ildiko Toma, Olga Sosnovtseva, Janos Peti-peterdi, N H Holstein-rathlouAbstract:Tubuloglomerular feedback (TGF) and the myogenic mechanism control afferent arteriolar diameter in each nephron and regulate blood flow. Both mechanisms generate self-sustained oscillations, the oscillations interact, TGF modulates the frequency and amplitude of the myogenic oscillation, and the oscillations synchronize; a 5:1 frequency ratio is the most frequent. TGF oscillations synchronize in nephron pairs supplied from a common cortical radial artery, as do myogenic oscillations. We propose that electrotonic vascular signal propagation from one juxtaglomerular apparatus interacts with similar signals from other Nephrons to produce synchronization. We tested this idea in tubular-vascular preparations from mice. Vascular smooth muscle cells were loaded with a fluorescent voltage-sensitive dye; fluorescence intensity was measured with confocal microscopy. Perfusion of the thick ascending limb activated TGF and depolarized afferent arteriolar smooth muscle cells. The depolarization spread to the cortical radial artery and other afferent arterioles and declined with distance from the perfused juxtaglomerular apparatus, consistent with electrotonic vascular signal propagation. With a mathematical model of two coupled Nephrons, we estimated the conductance of nephron coupling by fitting simulated vessel diameters to experimental data. With this value, we simulated nephron pairs to test for synchronization. In single-nephron simulations, the frequency of the TGF oscillation varied with nephron length. Coupling Nephrons of different lengths forced TGF frequencies of both pair members to converge to a common value. The myogenic oscillations also synchronized, and the synchronization between the TGF and the myogenic oscillations showed an increased stability against parameter perturbations. Electronic vascular signal propagation is a plausible mechanism for nephron synchronization. Coupling increased the stability of the various oscillations.
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Vascular coupling induces synchronization, quasiperiodicity, and chaos in a nephron tree.
Chaos, 2007Co-Authors: Donald J. Marsh, Olga Sosnovtseva, Erik Mosekilde, N H Holstein-rathlouAbstract:The paper presents a study of synchronization phenomena in a system of 22 Nephrons supplied with blood from a common cortical radial artery. The Nephrons are assumed to interact via hemodynamic and vascularly propagated coupling, both mediated by vascular connections. Using anatomic and physiological criteria, the Nephrons are divided into groups: cortical Nephrons and medullary Nephrons with short, intermediate and long Henle loops. Within each of these groups the delay parameters of the internal feedback regulation are given a random component to represent the internephron variability. For parameters that generate simple limit cycle dynamics in the pressure and flow regulation of single Nephrons, the ensemble of coupled Nephrons showed steady state, quasiperiodic or chaotic dynamics, depending on the interaction strengths and the arterial blood pressure. When the solutions were either quasiperiodic or chaotic, cortical Nephrons synchronized to a single frequency, but the longer medullary Nephrons formed two clusters with different frequencies. Under no physiologically realistic combination of parameters did all Nephrons assume a common frequency. Our results suggest a greater variability in the nephron dynamics than is apparent from measurements performed on cortical Nephrons only. This variability may explain the development of chaotic dynamics in tubular pressure records from hypertensive rats.
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Bimodal dynamics in nephron autoregulation
2003 IEEE International Workshop on Workload Characterization (IEEE Cat. No.03EX775), 2003Co-Authors: Olga Sosnovtseva, Erik Mosekilde, Alexey N. Pavlov, N H Holstein-rathlouAbstract:The individual functional unit of the kidney (the nephron) displays oscillations in its pressure and flow regulation at two different time scales: fast oscillations associated with a myogenic dynamics of the afferent arteriole, and slower oscillations arising from a delay in the tubuloglomerular feedback. We investigate the intra- and inter-nephron entrainment of the two time-scales. Besides full synchronization, both wavelet analyses of experimental data and numerical simulations reveal a partial entrainment in which neighboring Nephrons attain a state of chaotic synchronization with respect to their slow dynamics, but the fast dynamics remain desynchronized.
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Nonlinear Phenomena in Nephron-Nephron Interaction
Synchronization: Theory and Application, 2003Co-Authors: Erik Mosekilde, Olga Sosnovtseva, N H Holstein-rathlouAbstract:By controling the excretion of water and salts, the kidneys play an important role in regulating the blood pressure and maintaining a proper environment for the cells of the body. This control depends to a large extent on mechanisms that are associated with the individual functional unit, the nephron. However, a variety of cooperative phenomena arising through interactions among the Nephrons may also be important. The purpose of this chapter is to present experimental evidence for a coupling between Nephrons that are connected via a common piece of afferent arteriole, to develop a mathematical model that can account for the observed synchronization phenomena, and to discuss the possible physiological significance of these phenomena. We are particularly interested in synchronization effects that can occur among neighboring Nephrons that individually display irregular (or chaotic) dynamics in their pressure and flow regulation.
Saziye Bayram - One of the best experts on this subject based on the ideXlab platform.
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modeling tgf mediated flow dynamics in a system of three coupled Nephrons
International Journal for Numerical Methods in Biomedical Engineering, 2012Co-Authors: Saziye BayramAbstract:SUMMARY This paper focuses on a mathematical model of a system of three closely coupled Nephrons and accompanying analytical and computational analysis. In our previous modeling efforts, we have shown how coupling magnifies the tendency of many coupled identical Nephrons to oscillate owing to tubuloglomerular feedback (TGF) mechanism. However, in this study, our focus is on the coupled nonidentical Nephrons and their dynamics due to the TGF system. Our detailed analytical and computational results suggest that systems of three nonidentical Nephrons coupled to their nearest neighbors are prone to be found in an oscillatory state, relative to a single-nephron case with the same properties; however, their steady-state regions are not necessarily as small as it was predicted from the system of many coupled identical Nephrons cases. Copyright © 2012 John Wiley & Sons, Ltd.
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TGF-mediated dynamics in a system of many coupled Nephrons.
Bulletin of Mathematical Biology, 2009Co-Authors: Saziye Bayram, Tracy L. Stepien, E. Bruce PitmanAbstract:This paper presents a mathematical model of a system of many coupled Nephrons branching from a common cortical radial artery, and accompanying analysis of that system. This modeling effort is a first step in understanding how coupling magnifies the tendency of Nephrons to oscillate owing to tubuloglomerular feedback. Central to the present work is the single nephron integral model (as in Pitman et al., The IMA Volumes in Mathematics and Its Applications, vol. 129, pp. 345-364, 2002 and in Zaritski, Ph.D. Dissertation, 1999) which is a simplification of the single nephron PDE model of Layton et al. (Am. J. Physiol. 261, F904-F919, 1991). A second principal idea used in the present model is a coupling of model Nephrons, generalizing the work of Pitman et al. (Bull. Math. Biol. 66, 1463-1492, 2004) who proposed a model of two coupled Nephrons. In this study, we couple Nephrons through a nearest neighbor interaction.Speaking generally, our results suggest that a series of similar Nephrons coupled to their nearest neighbors are more prone to be found in an oscillatory mode, relative to a single nephron with the same properties. More specifically, we show analytically that, for N coupled identical Nephrons, the region supporting oscillatory solutions in the time delay-gain parameter plane increases with N. Numerical simulations suggest that, if N Nephrons have gains and time delays that do not differ by much, the system is, again, more prone to oscillate, relative to a single nephron, and the oscillations tend to be approximately synchronous and in-phase. We examine the effect of parameters on bifurcation. We also examine alternative models of coupling; this analysis allows us to conclude that the increased propensity of coupled Nephrons to oscillate is a robust finding, true for several models of nephron interaction.
Erik Mosekilde - One of the best experts on this subject based on the ideXlab platform.
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oscillator suppression in the blood flow regulation of interacting non identical Nephrons
Journal of Hypertension, 2013Co-Authors: Yulia P Emelianova, Erik Mosekilde, A P Kuznetsov, Jakob Lund Laugesen, Nielshenrik HolsteinrathlouAbstract:Background: Regulation of the blood flow to the individual functional unit (nephron) of the kidney involves a feedback mechanism that produces large-amplitude oscillations in the blood flow itself as well as in the intra-nephron pressures and flows. Neighboring Nephrons adjust their blood flow variations relative to one another via signals that propagate along the interconnecting blood vessels. Purpose and method: Using a detailed physiological-based model of a pair of vascular coupled, non-identical Nephrons, the paper examines the effect that their relative oscillatory strength has on the behavior of the coupled system. This is of direct interest in connection with ongoing work attempting to study the synchronization behavior for larger groups of superficial Nephrons by means of laser speckle contrast imaging. Results: Our analysis demonstrates that a region of so-called “broadband Synchronization” may develop between those coupling strengths at which the stronger oscillating nephron starts to suppress the autonomous oscillations of the weaker nephron and those coupling strengths at which the two Nephrons mutually inhibit each other’s oscillations. We suggest that the transition be-tween synchronized and suppressed dynamics may have a physiological significance comparable to the transition from ergodic to synchronized periodic dynamics.
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synchronization of period doubling oscillations in vascular coupled Nephrons
Chaos, 2011Co-Authors: Jakob Lund Laugesen, Erik Mosekilde, N H HolsteinrathlouAbstract:The mechanisms by which the individual functional unit (nephron) of the kidney regulates the incoming blood flow give rise to a number of nonlinear dynamic phenomena, including period-doubling bifurcations and intra-nephron synchronization between two different oscillatory modes. Interaction between the Nephrons produces complicated and time-dependent inter-nephron synchronization patterns. In order to understand the processes by which a pair of vascular coupled Nephrons synchronize, the paper presents a detailed analysis of the bifurcations that occur at the threshold of synchronization. We show that, besides infinite cascades of saddle-node bifurcations, these transitions involve mutually connected cascades of torus and homoclinic bifurcations. To illustrate the broader range of occurrence of this bifurcation structure for coupled period-doubling systems, we show that a similar structure arises in a system of two coupled, non-identical Rossler oscillators.
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Vascular coupling induces synchronization, quasiperiodicity, and chaos in a nephron tree.
Chaos, 2007Co-Authors: Donald J. Marsh, Olga Sosnovtseva, Erik Mosekilde, N H Holstein-rathlouAbstract:The paper presents a study of synchronization phenomena in a system of 22 Nephrons supplied with blood from a common cortical radial artery. The Nephrons are assumed to interact via hemodynamic and vascularly propagated coupling, both mediated by vascular connections. Using anatomic and physiological criteria, the Nephrons are divided into groups: cortical Nephrons and medullary Nephrons with short, intermediate and long Henle loops. Within each of these groups the delay parameters of the internal feedback regulation are given a random component to represent the internephron variability. For parameters that generate simple limit cycle dynamics in the pressure and flow regulation of single Nephrons, the ensemble of coupled Nephrons showed steady state, quasiperiodic or chaotic dynamics, depending on the interaction strengths and the arterial blood pressure. When the solutions were either quasiperiodic or chaotic, cortical Nephrons synchronized to a single frequency, but the longer medullary Nephrons formed two clusters with different frequencies. Under no physiologically realistic combination of parameters did all Nephrons assume a common frequency. Our results suggest a greater variability in the nephron dynamics than is apparent from measurements performed on cortical Nephrons only. This variability may explain the development of chaotic dynamics in tubular pressure records from hypertensive rats.
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Synchronization Phenomena in Nephron Autoregulation
2007Co-Authors: Erik MosekildeAbstract:The purpose of this presentation is to discuss the special forms of multimode dynamics that one can observe in resource-coupled systems, i.e., in systems of selfsustained oscillators in which the coupling takes place via the very flow of primary resources that maintains the oscillatory state of the individual unit. The interaction of two different oscillatory modes in the autoregulation of its blood flow causes the individual nephron to exhibit complicated temporal variations in its fluid flows and pressures. The Nephrons interact with one-another both via a hemodynamic coupling by which blood is displaced from one nephron to its neighbours and via a vascular propagated coupling that tends to produce in-phase synchronization over larger distances. We have updated the model of the individual nephron to provide a more accurate account of the arteriolar oscillations and we have analyzed the possible synchronization phenomena that can take place between superficial and deep Nephrons. Wavelet spectra for normol- and hypertensive rats show clear evidence of periodic-doubling bifurcations, and experimental results for neighboring Nephrons show in-phase as well as anti-phase synchronization.
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Bimodal dynamics in nephron autoregulation
2003 IEEE International Workshop on Workload Characterization (IEEE Cat. No.03EX775), 2003Co-Authors: Olga Sosnovtseva, Erik Mosekilde, Alexey N. Pavlov, N H Holstein-rathlouAbstract:The individual functional unit of the kidney (the nephron) displays oscillations in its pressure and flow regulation at two different time scales: fast oscillations associated with a myogenic dynamics of the afferent arteriole, and slower oscillations arising from a delay in the tubuloglomerular feedback. We investigate the intra- and inter-nephron entrainment of the two time-scales. Besides full synchronization, both wavelet analyses of experimental data and numerical simulations reveal a partial entrainment in which neighboring Nephrons attain a state of chaotic synchronization with respect to their slow dynamics, but the fast dynamics remain desynchronized.