An analysis of feedback-mediated oscillations in two coupled nephrons (Kevin Kesseler, Duke University)

Abstract: Previously, we analyzed effects of inter-nephron coupling by means of mathematical models of the tubulogomerular feedback (TGF) system in two short-looped nephrons. That study analyzed the transitions from time-independent steady states to regular, sustained oscillations in nephron flow (i.e., limit cycle oscillations, or LCO). LCO arise for sufficiently large TGF loop gains and sufficiently long time delays at the juxtaglomerular apparatus. In the present study we investigated how the inherent frequencies predicted by the model depend on these key parameters, and we conducted numerical experiments to determine how the model behaviors vary as a function of these parameters. We found that when the gains are equal and the delays are sufficiently close, LCO in the separate model nephrons have identical frequencies and oscillate in phase. However, when the delays are sufficiently different, the oscillations in the two model nephrons have differing frequencies and exhibit complex behaviors that can be understood by means of power spectra. Analysis of this model's behavior may help us understand power spectra obtained in physiological experiments.

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This is an abstract of a talk to be presented at the 2004 SEAMS Workshop in Charleston, SC. For more information, visit the workshop's homepage at math.cofc.edu/SEAMS.