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Consistency of nephron filtration measurements by collection of tubular total fluid from different proximal sites
No full textEur J Appl Physiol Occup Physiol. 1997;76(5):389-93.
Consistency of nephron filtration measurements by collection of total tubular fluid from different proximal sites.
Romano G, Damato R, Favret G, Bartoli E.
SourceDepartment of Internal Medicine, DPMSC, University of Udine, Medical School, Italy.
Abstract
The stability of single nephron glomerular filtration rate (SNGFR) is assured by specific mechanisms such as the tubulo-glomerular feedback system and autoregulation. Studies on renal physiology rely heavily on the measurements of SNGFR, which are feasible only in animals. The measurement of SNGFR by collection of total tubular fluid may be influenced by the fall in intratubular hydrostatic pressure that may reflect the negative pressure applied to the sampling pipette. This effect may become more important with shortening of the distance between the sampling site and the Bowman space. We analysed this putative effect by performing collections of total tubular fluid from the late proximal (LP), and then from the early proximal (EP) segment of the same nephrons. In 128 paired collections LP-SNGFR averaged 35 (SEM 2) nl x min(-1), and was no different from the paired mean EP-SNGFR of 37 (SEM 2) nl x min(-1), P > 0.179. Then EP- and LP- SNGFR were significantly correlated (r = 0.77, P < 0.001). As expected, the respective paired means of absolute and percentage reabsorptions, and those of collection rates were significantly different. The average SNGFR computed from each LP and EP paired measurement was significantly correlated with the simultaneously measured kidney glomerular filtration rate, GFR (r = 0.60, P < 0.0001). The ratio of GFR to SNGFR indicated the expected number of glomeruli. These data would indicate that the sampling site does not influence the measurement of SNGFR in the proximal tubule when the total fluid collection technique is correctly performed. They also exclude a time-dependent activation of the macula densa capable of upregulating SNGFR within the interval elapsing between the beginning of LP and the completion of EP collections, which in our study averaged 4.4 (SEM 0.1) min
Effetti della microiniezione endotubulare di soluzioni a differente osmolarità sul filtrato di singoli nefroni
No full textDevelopment of a Flight Management System Within the UAV - SCAUT Project
No full textThe Department of Aerospace Engineering of the University of Pisa is developing a research project, referred to as SCAUT Project, regarding the possibilities of employing UAVs of the MALE category for civil applications. After a brief introduction of the principal guidelines of the project, in this paper we describe the activities developed so far and introduce those currently in progress. The latter essentially concern the study of the problems related to the debugging phase of a Flight Management System (FMS) able to manage the UAV flight. The main functions required by the FMS are introduced and a discussion is made concerning the results obtained for the debugging functions of autopilot, navigation, and mission planning. The FMS software is implemented on a PC 104 computer. This software will be experimented in flight on a model in scale 1⁄2 of the UAV-SCAUT
Single nephron filtration rate during tubular microinjection of solutions of different tonicity
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