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  • 1
    Electronic Resource
    Electronic Resource
    Flow through brushborders and similar protuberant wall structures (1980)
    Springer
    The journal of membrane biology 56 (1980), S. 183-190 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Longitudinal flow through channels with protuberant wall structures such as brushborders were studied both experimentally and theoretically. The experiments were performed using tubes with synthetic internal brushborders, scaled to resemble the geometry and flow in proximal tubules of the kidney. Fractional flow rates in the brushborder were deduced from transit times of dye traces through the central core and total flow rate. The measured ratios of brushborder to core flowQ B /Q C were found to be independent of Reynolds number over the rangeRe=0.01–0.2. They agreed reasonably well with theoretical predictions based on the Kozeny-Carman equation for flow through arrays of parallel cylinders. The predictions can be extended to arbitrary geometries and turbulent flow conditions by appropriate modifications. Extrapolation of the results to the proximal tubule of the kidney indicate that brushborder flowrates there vary from 0.003 to 0.09% of total flow. Any axial transport in these structures would be predominantly diffusive in nature, and would be highly unlikely to affect radial brushborder gradients and transmural flux.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869475
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  • 2
    Electronic Resource
    Electronic Resource
    Functional heterogeneity of nephrons (1969)
    Springer
    Pflügers Archiv 308 (1969), S. 244-259 
    Details
    ISSN: 1432-2013
    Keywords: Flow Velocity in Single Nephron ; Ferrocyanide Clearance ; Ferrocyanide Located in Microdissected Nephrons ; Non-Uniformity of Nephron Function ; Nephron Dimensions ; Lineare Strömungsgeschwindigkeit im Einzelnephron ; Ferrocyanid Clearance ; Lokalisation von Ferrocyanid im mikrosezierten Nephron ; Ungleichheit der Nephronfunktion ; Nephrondimensionen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Intraluminal flow velocities and tubular dimensions were estimated for superficial and deep proximal tubules of non-diuretic kidneys with a technique developed byHanssen. Kidneys of anesthetized rats were frozen in vivo 4–20 sec after an i.v. injection of 0.05 ml 10–20% Na ferrocyanide. Ferrocyanide was located as prussian blue in microdissected tubules after freeze-substitution and maceration of the kidneys. Its position was used to indicate the movement of glomerular filtrate along the tubule. Ferrocyanide clearance was slightly less than that of inulin at low plasma ferrocyanide levels. They were equal at higher plasma levels. The two clearances were sufficiently alike, however, to justify using ferrocyanide as an indicator of glomerular filtrate in these experiments. Transient small decreases in systemic blood pressure and increases in renal blood flow followed i.v. injections of 0.05 ml ferrocyanide and 0.05 ml 5% lissamine green. There was no evidence of continuing intraluminal flow when the kidney was rendered ischemic by ligating the renal pedicle. The mean distance between glomerulus and prussian blue front in kidneys frozen at different intervals after a ferrocyanide injection increased curvilinearly with time in a manner compatible with its indicating mean flow velocity. The distance between glomerulus and dye front in tubules from any one kidney was proportional to tubular length. Flow velocities were similar when measured with lissamine green in vivo or with ferrocyanide in microdissected tubules. Velocities decreased whenC inulin was reduced by partial compression of the renal artery. The reduction was greater in superficial than in deep tubules suggesting that flow velocities vary non-uniformly as gfr changes. Luminal diameters measured in microdissected tubules were similar to other estimates of in vivo tubular dimensions. There was no apparent difference between the length or luminal diameter of proximal tubules from the surface and deeper portions of the cortex in these rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00586557
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  • 3
    Electronic Resource
    Electronic Resource
    Functional heterogeneity of nephrons (1969)
    Springer
    Pflügers Archiv 308 (1969), S. 260-276 
    Details
    ISSN: 1432-2013
    Keywords: Kidney Tubules ; Single Nephron Filtration Rates ; Heterogeneity of Nephron Function ; Structure and Function ; Nierentubuli ; Einzelnephronfiltrationsrate ; Unterschiede der Nephronfunktion ; Struktur und Funktion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Non-diuretic rats and saline diuretic psammomys received 0.05 ml14C Na ferrocyanide i.v. Their kidneys were frozen in vivo 8–10 sec later. The quantity of14C ferrocyanide precipitated as prussian blue (Hanssen) in the lumen of a microdissected proximal tubule was proportional to its glomerular filtration rate (gfr). Distance between dye front and glomerulus was proportional to mean flow velocity (v). Fractional water reabsorption at the dye front was calculated using gfr, v and luminal radius. There were large differences in gfr, v and fractional water reabsorption between superficial and deep nephrons. Published micropuncture data agrees quantitatively with our results. Glomerular volume, tubular length and luminal radius increased from superficial to juxtamedullary proximal tubules in both species. Filtration rate varied directly with glomerular volume suggesting an influence of capillary surface area on filtration. Tubular length and luminal radius correlated with gfr. Proximal water reabsorption rate correlated with luminal radius in psammomys but not in rat tubules. Water reabsorption by the entire proximal tubule decreased with length in rat tubules but increased in psammomys. The discrepancy may be due to differences in blood flow distribution which alter gfr and/or water reabsorption in superficial relative to deep nephrons.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00586558
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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