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  • 1
    ISSN: 0300-9629
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0020-711X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1440
    Keywords: Proteinuria ; Tubular disease ; Microgradientgel electrophoresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to estimate the degree of tubular lesions and to detect a possible glomerular involvement, proteinuria was studied in tubular and/or interstitial nephropathies by determination of total protein and beta-2 microglobulin and by micro-gradientgel electrophoresis. The excretion of albumin, low molecular weight proteins (LMW) and high molecular weight (HMW) proteins was measured in addition. Other proximal tubulus functions such as glucose and phosphate reabsorption were also measured. The clinical entities studied were: chronic postinfectious nephritis, patients with nephropathy following analgesic abuse, tubular glucosuria in pregnancy and cis-platinum treated patients suffering from testicular tumor. The results were interpreted basing on the “selectivity” or urinary protein patterns, which means the relation between LMW and HMW proteins. Micro-gradientgel electrophoresis proved to be a fast and sensitive tool for quantitative as well as qualitative analysis of albumin, LMW and HMW proteins. All patients with advanced tubulo-interstitial disease excreted increased amounts of LMW proteins. The excretion of beta-2 microglobulin was also high and correlated with the LMW protein excretion. The albumin and HMW protein excretion showed no relation to LMW proteins. The disproportionate increase of LMW protein excretion on the one hand and albumin and HMW protein excretion on the other suggests different reabsorption mechanisms. The tubular patterns originate from a more easily disturbed reabsorption of LMW proteins and/or from a normally more active reabsorption of LMW proteins. Except in renal glucosuria phosphate and glucose excretion were not increased. This means that the capacity for the reabsorption of glucose and phosphate copes with a normal filtered load even in patients with highly increased proteinuria of a tubular type.
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  • 5
    ISSN: 1432-1440
    Keywords: Proteinurie ; Glomeruläre Funktion ; Niere ; Proteinausscheidung der Niere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2013
    Keywords: Tubular Fluid Reabsorption ; Water Permeability ; Adrenalectomy ; Adrenal Cortical Hormones ; Glucocorticoids ; Tubuläre Flüssigkeitsresorption ; Wasserpermeabilität ; Adrenalektomie ; Nebennierenrindenhormone ; Glucocorticoide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to analyse the mechanism of inhibition of water diuresis in adrenal insufficiency renal surface tubulus of male albino rats (group I: controls, group II: 8 days or more after bilateral adrenalectomy) have been perfused using the free flow microperfusion technique. From the percent osmotic equilibration of a hypotonic perfusate as measured cryoscopically osmotic water permeability (L p) has been calculated. Furthermore, percent osmotic equilibration has been estimated from transtubular net water flux measured with 14C-inulin. With both methods which constitute a maximum estimate (cryoscopic data) and a minimum estimate (inulin data) osmotic water permeability was found to be increased after adrenalectomy in distal convolutions. Hormone substitution with either cortisone (2.5 mg/100 g b.w. 24 hours i.m.) or dexamethasone (0.05 mg/100 g b.w. 24 hours i.m.) reestablished towards normal water permeability after 3 days of treatment. The data are compatible with the concept of a direct effect of glucocorticosteroids on water permeability of distal tubule membranes. In the proximal convolution osmotic water permeability was unaffected by bilateral adrenalectomy.
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  • 7
    ISSN: 1432-2013
    Keywords: Perfusion of Peritubular Capillaries ; Water Reabsorption ; Sodium Transport ; Proximal Convolution ; Collecting Duct ; peritubuläre Capillarperfusion ; Wasserresorption ; Natriumtransport ; proximales Konvolut ; Sammelrohre
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung An Ratten wurden Mikropunktionsuntersuchungen am proximalen Tubulus und am Sammelrohr bei Durchblutung der peritubulären Capillaren bzw. Vasa recta sowie bei künstlicher Perfusion dieser Blutgefäße durchgeführt. In Abhängigkeit von der Höhe der interstitiellen Natriumkonzentration wurden der Nettonatriumtransport (ΆNa iso) bei gleicher Natriumkonzentration zu beiden Seiten der Tubuluswand und die Gleichgewichtskonzentrationsdifferenz (Δc Na) bei fehlendem Nettovolumen- und Nettosubstanzfluß gemessen. Bei Variation der Natriumkonzentration im Gewebe durch Perfusion der peritubulären Capillaren mit 155 bzw. 300 mÄq/l Na änderten sich weder ΆNa iso noch Δc Na für den proximalen Tubulus (ΆNa iso 8,4 bzw. 7,9·10−5 μÄq · mm−2 · sec−1; Δc Na 24 bzw. 24 mÄq/l). Veränderung der Natriumkonzentration im Blut durch Infusion hypertoner NaCl Lösung oder Peritonealdialyse mit isotoner Mannitlösung führten zu prinzipiell gleichen Ergebnissen. Bei Perfusion der Vasa recta mit Lösungen, die 145 und 300 mÄq/l Natrium entheilten, blieben ΆNa iso wie Δc Na über die Sammelrohrwand ebenfalls konstant (ΆNa iso 4,1 bzw. 4,1·10−5 μÄq · mm−2 · sec−1; Δc Na 98 bzw. 104 mÄq/l). Proximale Tubuli und Sammelrohre verhalten sich demnach bei Variation der interstitiellen Natriumkonzentration gleich. Da die Wasserresorption aus den Sammelrohren von dem durch Gegenstrommultiplikation erzeugten Natriumkonzentrationsanstieg im Markinterstitium abhängt, die Natriumresorption aus den Sammelrohren aber wie die vorliegenden Befunde zeigen von eben dieser Natriumkonzentration unabhängig ist, ist dem Warmblüterorganismus die Möglichkeit gegeben, Natrium- und Wasserresorption unabhängig voneinander zu variieren. Die Natrium- und Wasserresorption aus den Sammelrohren werden jedoch beide durch den Gehalt der Sammelrohrflüssigkeit an permeablen Nichtelektrolyten, wie z. B. Harnstoff, beeinflußt.
    Notes: Summary Micropuncture experiments were performed on proximal tubules and collecting ducts of rat kidneys with and without artificial perfusion of surrounding capillaries or vasa recta respectively. Net sodium flux (ΆNa iso) was estimated under conditions of varying but equal sodium concentrations on both sides of the tubular wall. The transtubular wall equilibrium concentration difference of sodium (Δc Na) was also measured in these nephron segments under conditions of zero volume and solute fluxes. In the proximal tubule ΆNa iso of 8.4 and 7.9×10−5 μeq × mm−2 × sec−1 at sodium concentrations of 155 and 300 meq/l in the perfusion fluid and Δc Na of 24 and 24 meq/l respectively did not vary significantly. Variations of sodium concentrations in blood produced by hypertonic saline infusion or peritoneal dialysis with mannitol resulted in essentially similar values of ΆNa iso and Δc Na. In the collecting ducts also ΆNa iso and Δc Na remained uninfluenced by induced variations in sodium concentrations of the perfusion fluid. ΆNa iso at sodium concentration of 145 and 300 meq/l in the perfusion fluid of vasa recta was 4.1 and 4.1×10−5 μeq × mm−2 × sec−1 respectively and Δc Na was 98 and 104 meq/l respectively. Water reabsorption in the collecting ducts depends on the increase of sodium concentration produced in the medulla by the countercurrent multiplier system. The results represented here indicate that, in mammals sodium reabsorption is independent from the sodium concentration of the interstitial fluid. Therefore the sodium reabsorption and the water reabsorption can be varied independently from each other. Both, sodium and water reabsorption in the collecting ducts are however dependent upon the concentrations of permeable nonelectrolytes such as urea in the collecting duct fluid.
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  • 8
    ISSN: 1432-2013
    Keywords: D-Glucose Transport ; Microperfusion Study ; Proximal Tubule ; Fluid Reabsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Hexose reabsorption in the kidney was investigated by microperfusion of proximal cortical rat nephrons with Ringer's solution containingD-glucose (2.5, 5.0 and 18.0 mM/l), 3-O-methylD-glucose (4.5 mM/l) orD-fructose (18.0 mM/l) at perfusion rates of 20 or 40×10−6 ml/min. Inulin was used as a reference for fluid reabsorption. 1. The fraction of fluid reabsorbed was independent of the glucose concentration but it decreased when the perfusion rate increased from 20–40×10−6 ml/min. 2. At 18.0 mM/l the % glucose reabsorption was equal to the % fluid reabsorption. This equality was independent of the perfusion rate, (20 or 40×10−6 ml/min), indicating 1:1 coupling with net isotonic fluid reabsorption. 3. At 2.5 mM/l the % glucose reabsorption was greater than the % fluid reabsorption, indicating predominance of an active component to theD-glucose transport. 4. 3-O-methylD-glucose was reabsorbed at one third the rate ofD-glucose. There was no reabsorption ofD-fructose at the concentration used. Since neither of the latter two sugars showed an increment in reabsorption proportional to changes in net fluid movement, we postulate that specificity for glucose reabsorption occurs prior to the site of coupling with fluid flow.
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  • 9
    ISSN: 1432-2013
    Keywords: D-Glucose Transport ; T mG ; Proximal Tubule ; Glomerular ; Tubular Balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary From earlier microperfusion studies ofD-glucose and water reabsorption in the proximal surface nephron of the rat,D-glucose was found to be removed by a saturable carrier and by an apparent coupling with net fluid reabsorption. Equations appropriate to describe this system were developed. They incorporated carrier-mediatedD-glucose transport, net water transport, and water-coupled solute transport. Water reabsorption was assumed to be constant either per unit surface area, or per unit volume of the nephron, and the rate of carrier-transportedD-glucose was assumed constant per unit length, per unit surface area, or per unit volume of the tubule. The possibility thatD-glucose could be reabsorbed via two carrier systems was also explored analytically. It was observed from this treatment that the fraction ofD-glucose reabsorbed would change if the perfusion rate was changed. With an increase in perfusion rate, a decrease in reabsorbed fraction was seen which indicates that if net fluid reabsorption is proportional to volume, carrier-mediated sugar transport is proportional to surface area or length of the tubule. From these relationshipsJ max, the maximal rate of carrier-transported sugar, was calculated to be 3.3×10−10M/cm2 sec, a value comparable to that reported from other laboratories. The results of this analysis are compatible with the data obtained both by micropuncture experiments during free flow and by glucose clearance studies until theT mG is reached. The possibility that theT mG obtained in clearance studies is due to a decrease in the fraction of fluid reabsorbed in the proximal tubule or to a second saturable carrier is discussed. It is observed that, in either case, if load is increased by increasing the glomerular filtration rate, noT mG would be reached, or stated another way, one would predict from the analysis thatT mG would be proportional to glomerular filtration rate.
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  • 10
    ISSN: 1432-2013
    Keywords: Sex dependent proteinuria ; Micro-disc electrophoresis ; Micropuncture technique ; Isolated perfused rat kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The separation of sex dependent urinary proteins of the rat (SDP) by micro-disc electrophoresis results in at least eight well defined protein bands with differing molecular weights. The hepatic origin of a sex dependent urinary protein, named α2u-globulin, has been demonstrated before by other authors applying immunological methods. In the present study, it could been shown that SDP circulate in the plasma at a concentration of 23.8 mg/l. The origin of those protein bands which appear typically upon electrophoresis was still under dispute because they could not been demonstrated in proximal tubular fluid. The present study confirms the extrarenal source of SDP and suggests identity with α2u-globulin. The attempt to track down SDP from plasma to excreted urine demonstrated that, in contrast to proximal fluid, samples from nephron parts distal to the loop of Henle contain large amounts of SDP. An isolated kidney model was used to determine the sieving coefficient and tubular reabsorption of SDP, obtained from male rat urine. We have found a correlation between the sieving coefficient and the molecular weight of SDP. The sieving coefficient ranged from 0.375 to 0.834. The tubular reabsorption which has been determined with an isolated kidney perfused with albumin and erythrocytes also showed variation with regard to molecular weight and was 61.7%, on average.
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