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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: 1439-6327
    Keywords: Key words Carbohydrate supplementation ; Blood glucose ; Cortisol ; Growth hormone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This randomized, double-blind, placebo-controlled study was designed to determine the influence of exercise mode, and 6% carbohydrate (C) versus placebo (P) beverage ingestion, on ratings of perceived exertion (RPE) and hormonal regulation to 2.5 h of high-intensity running and cycling (≈75% maximum oxygen uptake) by ten triathletes who acted as their own controls. Statistical significance was set at P ≤ 0.05. The pattern of change in RPE over time was significantly different between C and P ingestion (P 〈 0.001) and between running and cycling modes (P = 0.001). The lowest RPE values were seen in the C-cycling sessions and the highest in the P-running sessions. The pattern of change in the respiratory exchange ratio and fat and carbohydrate oxidation rates were significantly different between the C and P conditions but not between the running and cycling modes. C relative to P ingestion (but not exercise mode) was associated with higher plasma levels of glucose and insulin and lower plasma cortisol and growth hormone levels. The pattern of change in plasma levels of catecholamines and lactate did not differ between the C and P conditions. These data indicate that a lower RPE was associated with a higher level of carbohydrate oxidation, higher plasma glucose and insulin levels, and lower plasma cortisol and growth hormone levels during cycle exercise following C supplementation as compared to P feeding. These findings support a physiological link between RPE and carbohydrate substrate availability as well as selected hormonal regulation during cycle exercise.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    European journal of applied physiology 81 (2000), S. 222-228 
    ISSN: 1439-6327
    Keywords: Key words Rowing ; Infection ; Cortisol ; Catecholamines ; Carbohydrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Saliva immunoglobulins (sIgA, sIgG, and sIgM) and upper respiratory tract infection (URTI) rates were evaluated in 20 elite female rowers and 19 nonathletes. Also, the influence of carbohydrate versus placebo beverage consumption on saliva immunoglobulin responses to rowing training sessions was measured in 15 rowers and in 5 non-exercising rowers. Saliva samples were collected 1 day before, and 5–10 min and 1.5 h after rowing or rest. Pre-exercise sIgA (but not sIgG or sIgM) concentration was 77% higher in the rowers compared to nonathletes (P 〈 0.001). Health records kept over 2 months revealed mean 5.2 (SEM 1.2) and 3.3 (SEM 1.1) days with URTI symptoms for the rowers and controls, respectively. For all 39 subjects, and for the 20 rowers separately, no significant correlation was found between URTI symptoms or insulin, cortisol, and growth hormone concentrations and pre-exercise or exercise-related changes in saliva immunoglobulin concentrations or secretion rates. The patterns of change in saliva immunoglobulin concentration and secretion rate did not differ between the carbohydrate and placebo rowing trials, or between exercised and rested athletes. These data indicated an increased sIgA concentration in the female elite rowers compared to the nonathletes, no association between saliva immunoglobulins and URTI, and no effect of a normal 2-hour training session or carbohydrate ingestion on saliva immunoglobulin concentrations or secretion rates.
    Type of Medium: Electronic Resource
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