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  • 1
    ISSN: 1432-2013
    Keywords: Nephron Filtration Rate ; Antidiuretic Hormone ; Diabetes Insipidus Rats ; Ferrocyanide Method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of antidiuretic hormone on the distribution of nephron filtration rates was studied in rats with hereditary diabetes insipidus using the Hanssen method for determination of nephron filtration rates as modified by de Rouffignacet al. [18]. Conversion of water diuresis to antidiuresis by infusion of ADH resulted in a moderate, but highly significant increase in the filtration rate of the juxtamedullary nephrons, while the nephrons of all other cortex regions filtered at an unaltered rate. A mechanism based on the action of ADH on distal nephron water permeability is proposed as an explanation: water inflow into the medulla very likely decreases when water diuresis is converted to antidiuresis. This occasions a rise in medullary osmolality which then causes an increase in the apparent viscosity of the blood flowing through the vasa recta. This is responsible for a rise in juxtamedullary postglomerular resistance which results in an increase in the effective filtration pressure and thus in the juxtamedullary nephron filtration rate. The results suggest that an increased juxtamedullary filtration rate participates in the establishment and maintenance of the inner medullary solute gradients, possibly as a consequence of an increased solute delivery to the ascending limbs of the long loops of Henle.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 344 (1973), S. 69-74 
    ISSN: 1432-2013
    Keywords: Nephron Filtration Rate ; Ferrocyanide Method ; Redistribution of GFR ; Urine Osmolarity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Experiments were performed to clarify the cause of the dependency of juxtamedullary nephron filtration rate (JN-GFR) on the diuretic state of the animal. Using the ferrocyanide technique of de Rouffignacet. al. [5] the distribution of nephron filtration rates was determined during selective modification of final urine osmolarity by papillary superfusion with concentrated or isotonic solutions. Papillary superfusion with a 2000 mosmolar solution led to a mean urine osmolarity of 1848±78 mOsm/l. JN-GFR displayed a mean increase of 66.6% over the superficial nephron filtration rate (SN-GFR). When the superfusion fluid was isotonic urine osmolarity averaged 754±53 mOsm/l and JN-GFR increased by a mean of only 26.3% over the SN-GFR. Using the micropuncture technique it was shown that SN-GFR in a given animal was not altered when the superfusion fluid was interchanged. We conclude therefore that the change in the percentage increase in GFR from superficial to juxtamedullary nephrons is caused by a change of juxtamedullary nephron filtration rate. Since plasma ADH concentration was not altered this effect appears to be elicited by the changed medullary solute concentration rather than by a vasomotor action of the antidiuretic hormone.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2013
    Keywords: Dog Kidney ; Saline Infusion ; Nephron Filtration Rate ; Filtrate Distribution ; Ferrocyanide Method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The intrarenal distribution of nephron filtration rate (N-GFR) was assessed using the Hanssen ferrocyanide technique in dogs which were chronically salt loaded with or without an additional acute sodium load and in sodium depleted dogs. In 4 dogs fed 7–10 days on a high sodium diet, superficial nephron filtration rate (SN-GFR) was 56.7±13.1 nl/min, middle nephron filtration rate (MN-GFR) was 65.2±14.3 nl/min, and the juxtamedullary nephron filtration rate (JN-GFR) was 82.4±17.1 nl/min, a value 52.3% higher than the SN-GFR. Creatinine clearance in these animals averaged 22.0±3.9 ml/min. In 4 animals which received an additional infusion of 0.9% NaCl at 4.0–4.5 ml/min for 2.5 h, the mean creatinine clearance rose from 16.6±2.0 ml/min to 20.3±0.7 ml/min and the distribution of N-GFR was: SN-GFR 70.5±21.2 nl/min, MN-GFR 83.6±23.8 nl/min and JN-GFR 91.2±24.3 nl/min. In this case, the JN-GFR was 29.3% higher than the SN-GFR. In one sodium depleted dog, (creatinine clearance 15.7 ml/min) the distribution of N-GFR was: SN-GFR 41.1±10.5 nl/min, MN-GFR 48.0±16.5 nl/min, and JN-GFR 58.0±19.0 nl/min, a value exceeding SN-GFR by 41.1%. These results imply that acute saline infusion in dogs induces a proportionately greater change in GFR of superficial than of juxtamedullary nephrons.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-2072
    Keywords: Slow wave sleep ; 5-HT2/1c receptor ; Ritanserin ; ICI 169,369 ; Home sleep recordings
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of the selective 5-HT2 receptor antagonists, ritanserin (1, 5 and 10 mg) and ICI 169,369 (50 and 100 mg), were studied on the sleep EEG of healthy volunteers using home-based Medilog 9000 cassette monitoring. Ritanserin (5 and 10 mg) produced a significant increase in slow wave sleep (SWS) while ICI 169,369 also increased SWS but only at a dose of 100 mg. These findings are consistent with the proposal that selective 5-HT2 receptor blockade increases SWS in humans; however, the data cannot exclude involvement of the closely related 5-HT1c receptor in this effect.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2072
    Keywords: Anxiety ; Slow wave sleep ; Ritanserin ; 5-HT2 receptor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Eight patients with generalised anxiety disorder (GAD) and eight matched healthy controls had their polysomnogram measured on two occasions separated by 1 week. On one occasion they received the 5-HT2 receptor antagonist, ritanserin (5 mg orally) and on the other matching placebo. The increase in slow wave sleep produced by ritanserin was the same in GAD patients as in healthy controls. These findings do not support the hypothesis that GAD is associated with a generalised hypersensitivity of brain 5-HT2 receptors; however, the present data cannot exclude the presence of a regionally specific change in this receptor subtype in anxiety disorders.
    Type of Medium: Electronic Resource
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