Daniel James Marsh

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In order to assess the linearity of the mechanisms subserving renal blood flow autoregulation, broad-band arterial pressure fluctuations at three different power levels were induced experimentally and the resulting renal blood flow responses were recorded. Linear system analysis methods were applied in both the time and frequency domain. In the frequency(More)
The potential role of integrins in the myogenic mechanism was studied in the rat afferent arteriole (AA) by fluorescence immunolocalization and microperfusion of isolated AA. Confocal fluorescence images were acquired from frozen sections of rat kidney after indirect immunostaining for various integrin beta- and alpha-subunits. The beta 1-, beta 3-, alpha(More)
Two models of ypertonic urine formation in the inner medulla were tested. The active model asserts that thin ascending limbs of Henle's loop (ALH) reasorb NaCl hypertonically by active transport; the passive model suggests the reabsorption is by diffusion down a concentration gradient. Using (Na+) in ascending vasa recta (AVR) as a measure of interstitial(More)
This article presents results of the use of a novel methodology employing principal dynamic modes (PDM) for modeling the nonlinear dynamics of renal autoregulation in rats. The analyzed experimental data are broadband (0-0.5 Hz) blood pressure-flow data generated by pseudorandom forcing and collected in normotensive and hypertensive rats for two levels of(More)
SUMMARY Oscillations in mean arterial blood pressure (MABP) with periods near 1.5 hours were observed in conscious male dogs with pressure transducers implanted in their aortas. Cardiac output (CO) was measured with an electromagnetic flow probe implanted about the ascending aorta, and total peripheral resistance (TPR) was calculated as the ratio of MABP to(More)
Hydrostatic pressures were measured in cortical tubules, long loops of Henle, terminal collecting ducts, and in vasa recta in hamsters. In hydropenia, the loops of Henle and terminal collecting ducts provided the major fluid flow resistances, as judged by the location of hydrostatic pressure drops. In mannitol or saline diuresis, hydrostatic pressures in(More)
Mean arterial blood pressure was measured for 2 days in conscious dogs to estimate the frequency of ultradian fluctuations and to compare the magnitudes of the ultra- and circadian fluctuations. The ultradian fluctuation had an average frequency of 0.38 +/- 0.04 cycle/h and 60% more power than the circadian rhythm. The ultradian fluctuation was consistently(More)
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