Chaos and non-linear phenomena in renal vascular control

Yip, Kay‐Pong; Holstein‐Rathlou, Niels‐Henrik

doi:10.1016/s0008-6363(95)00083-6

Cited by 24 publications

(6 citation statements)

References 51 publications

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“…4 and 5 and, as previously discussed, it is likely that they can be ascribed to a chaotic dynamics. 19,13,20,25 In spite of this irregularity, however, one can visually observe a certain degree of synchronization between the interacting nephrons. Figure 7 reproduces the results of a frequency analysis of the two pressure signals in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…3 is also similar to the attractors that one can obtain through reconstruction ͑in terms of delay variables͒ of experimental results for the proximal tubular pressure in hypertensive rats. 13 The chaotic nature of the pressure variations is supported by a series of studies 19,13,20,25 applying a variety of different techniques, most recently by a work 26 in which the experimental time series have been fitted to a nonlinear autoregressive model, and the presence of deterministic dynamics with a positive Lyapunov exponent has been demonstrated.…”

Section: Nephron-nephron Interactionmentioning

confidence: 99%

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Synchronization phenomena in nephron–nephron interaction

Holstein‐Rathlou

Yip

Sosnovtseva

et al. 2001

Chaos: An Interdisciplinary Journal of Nonlinear Science

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Experimental data for tubular pressure oscillations in rat kidneys are analyzed in order to examine the different types of synchronization that can arise between neighboring functional units. For rats with normal blood pressure, the individual unit ͑the nephron͒ typically exhibits regular oscillations in its tubular pressure and flow variations. For such rats, both in-phase and antiphase synchronization can be demonstrated in the experimental data. For spontaneously hypertensive rats, where the pressure variations in the individual nephrons are highly irregular, signs of chaotic phase and frequency synchronization can be observed. Accounting for a hemodynamic as well as for a vascular coupling between nephrons that share a common interlobular artery, we develop a mathematical model of the pressure and flow regulation in a pair of adjacent nephrons. We show that this model, for appropriate values of the parameters, can reproduce the different types of experimentally observed synchronization. © 2001 American Institute of Physics. ͓DOI: 10.1063/1.1376398͔The kidneys play an essential 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 associated with the individual functional unit, the nephron. However, a variety of cooperative phenomena that arise from interactions among the nephrons may also be important. In-phase synchronization, for instance, where the nephrons simultaneously perform the same regulatory adjustments of the incoming blood flow is likely to produce fast and strong effects in the overall response to changes in the external conditions. Out-ofphase synchronization, on the other hand, will lead to a slower and less pronounced response of the system in the aggregate. The purpose of the present paper is to demonstrate how different forms of synchronization can be observed in the pressure and flow variations for neighboring nephrons. Particularly interesting is the observation of chaotic phase synchronization in rats with high blood pressure. Based on a description of the physiological mechanisms involved in the various regulations, we develop a mathematical model that can account for the experimentally observed synchronization phenomena.

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Section: Resultsmentioning

confidence: 99%

Section: Nephron-nephron Interactionmentioning

confidence: 99%

Synchronization phenomena in nephron–nephron interaction

Holstein‐Rathlou

Yip

Sosnovtseva

et al. 2001

Chaos: An Interdisciplinary Journal of Nonlinear Science

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“…myogenic response; paramagnetic bead; cell traction force microscopy; calcium signaling MYOGENIC VASOCONSTRICTION is an autoregulatory mechanism for adjusting local vascular resistance to the increase in arterial pressure, which fluctuates over a wide range under different physiological and pathophysiological conditions (27,43). In the renal circulation, pressure-induced myogenic constriction in the afferent arteriole is an important protective mechanism to prevent the transmission of elevated systemic pressure to the glomerular capillaries, a critical determinant in the progression of glomerulosclerosis in diabetes, hypertension, and end-stage renal disease.…”

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confidence: 99%

Remanent cell traction force in renal vascular smooth muscle cells induced by integrin-mediated mechanotransduction

Balasubramanian

Sham

et al. 2013

American Journal of Physiology-Cell Physiology

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It was previously demonstrated in isolated renal vascular smooth muscle cells (VSMCs) that integrin-mediated mechanotransduction triggers intracellular Ca(2+) mobilization, which is the hallmark of myogenic response in VSMCs. To test directly whether integrin-mediated mechanotransduction results in the myogenic response-like behavior in renal VSMCs, cell traction force microscopy was used to monitor cell traction force when the cells were pulled with fibronectin-coated or low density lipoprotein (LDL)-coated paramagnetic beads. LDL-coated beads were used as a control for nonintegrin-mediated mechanotransduction. Pulling with LDL-coated beads increased the cell traction force by 61 ± 12% (9 cells), which returned to the prepull level after the pulling process was terminated. Pulling with noncoated beads had a minimal increase in the cell traction force (12 ± 9%, 8 cells). Pulling with fibronectin-coated beads increased the cell traction force by 56 ± 20% (7 cells). However, the cell traction force was still elevated by 23 ± 14% after the pulling process was terminated. This behavior is analogous to the changes of vascular resistance in pressure-induced myogenic response, in which vascular resistance remains elevated after myogenic constriction. Fibronectin is a native ligand for α(5)β(1)-integrins in VSMCs. Similar remanent cell traction force was found when cells were pulled with beads coated with β(1)-integrin antibody (Ha2/5). Activation of β(1)-integrin with soluble antibody also triggered variations of cell traction force and Ca(2+) mobilization, which were abolished by the Src inhibitor. In conclusion, mechanical force transduced by α(5)β(1)-integrins triggered a myogenic response-like behavior in isolated renal VSMCs.

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“…Using recently-developed TVTF and TVCF approaches (31, 32), we were able to critically examine the stationarity of the TGF and myogenic autoregulatory mechanisms, to assess the extent that nonstationarities contributes to autoregulatory effectiveness and dynamic complexity. Based on information from studies of nonlinear dynamics (4,6,7,21,24,28,30) and from time-frequency mapping (11,33), we predicted greater time-varying content in SHR than in SDR rats. The main findings of this study are that autoregulatory dynamics in both strains show significant variation over time, in the form of intermittent peaks and slow oscillations in transfer function gain.…”

Section: Discussionmentioning

confidence: 99%

Analysis of nonstationarity in renal autoregulation mechanisms using time-varying transfer and coherence functions

Chon¹,

Zhong²,

Moore³

et al. 2008

American Journal of Physiology-Regulatory, Integrative and Comp

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Chon KH, Zhong Y, Moore LC, Holstein-Rathlou NH, Cupples WA. Analysis of nonstationarity in renal autoregulation mechanisms using time-varying transfer and coherence functions. Am J Physiol Regul Integr Comp Physiol 295: R821-R828, 2008. First published May 21, 2008 doi:10.1152/ajpregu.00582.2007.-The extent to which renal blood flow dynamics vary in time and whether such variation contributes substantively to dynamic complexity have emerged as important questions. Data from Sprague-Dawley rats (SDR) and spontaneously hypertensive rats (SHR) were analyzed by time-varying transfer functions (TVTF) and time-varying coherence functions (TVCF). Both TVTF and TVCF allow quantification of nonstationarity in the frequency ranges associated with the autoregulatory mechanisms. TVTF analysis shows that autoregulatory gain in SDR and SHR varies in time and that SHR exhibit significantly more nonstationarity than SDR. TVTF gain in the frequency range associated with the myogenic mechanism was significantly higher in SDR than in SHR, but no statistical difference was found with tubuloglomerular (TGF) gain. Furthermore, TVCF analysis revealed that the coherence in both strains is significantly nonstationary and that low-frequency coherence was negatively correlated with autoregulatory gain. TVCF in the frequency range from 0.1 to 0.3 Hz was significantly higher in SDR (7 out of 7, Ͼ0.5) than in SHR (5 out of 6, Ͻ0.5), and consistent for all time points. For TGF frequency range (0.03-0.05 Hz), coherence exhibited substantial nonstationarity in both strains. Five of six SHR had mean coherence (Ͻ0.5), while four of seven SDR exhibited coherence (Ͻ0.5). Together, these results demonstrate substantial nonstationarity in autoregulatory dynamics in both SHR and SDR. Furthermore, they indicate that the nonstationarity accounts for most of the dynamic complexity in SDR, but that it accounts for only a part of the dynamic complexity in SHR.hemodynamics; myogenic; tubuloglomerular feedback; hypertension AUTOREGULATION OF RENAL BLOOD flow is mediated by the myogenic responses of the preglomerular vasculature (MYO) and the TGF feedback system. These two mechanisms exhibit characteristic resonant frequencies (MYO, 0.1-0.3 Hz; TGF, 0.02-0.05 Hz in rats). The marked difference in characteristic frequencies (and, hence, in time constants) between the TGF and MYO mechanisms permit separation and quantification of contributions of the two mechanisms by transfer function (1, 4, 29) and coherence analyses (2,12).A transfer function is the input-output relationship between an independent variable (blood pressure) and a dependent variable [renal blood flow (RBF)]. Its output is given in terms of gain, which reports fluctuation of the output with respect to the input and phase that contains the temporal relationship between the two signals. Thus, normalized gain Ͻ0 dB indicates that RBF is stabilized with respect to blood pressure and hence that autoregulation is effective. The coherence function assesses the degree to which the data are related ...

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Chaos and non-linear phenomena in renal vascular control

Cited by 24 publications

References 51 publications

Synchronization phenomena in nephron–nephron interaction

Synchronization phenomena in nephron–nephron interaction

Remanent cell traction force in renal vascular smooth muscle cells induced by integrin-mediated mechanotransduction

Analysis of nonstationarity in renal autoregulation mechanisms using time-varying transfer and coherence functions

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