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  • Chemical Engineering  (6)
  • Cortisol  (2)
  • Intratubular Pressure  (2)
  • Micropuncture  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Micropuncture method for the determination of nephron filtration rate (1972)
    Springer
    Pflügers Archiv 333 (1972), S. 271-280 
    Details
    ISSN: 1432-2013
    Keywords: Nephron Filtration Rate ; Tubulo-Glomerular Feedback ; Intratubular Pressure ; Polyfructosan
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Two possible artifacts may explain the phenomenon that nephron GFR (N-GFR) measured by distal tubular puncture is smaller than that measured by proximal tubular puncture: a loss of the inulin-like substance used in this laboratory (polyfructosan) from the tubular lumen or unreliable distal punctures. To test these possibilities (a) known amounts of polyfructosan were injected into the proximal tubule and the percentage recovery from the distal tubule measured, (b) N-GFR was measured by distal puncture, subsequently by recollection from the same site and finally by a proximal puncture. On the average, 98.5±7.5% of the proximally injected polyfructosan was recovered from the distal tubule. This is not significantly different from 100% (p〉0.1) and demonstrates that proximal tubule and loop of Henle are impermeable to polyfructosan. The ratio between the N-GFR measured by a distal puncture and that measured by subsequent recollection was 1.016±0.096 and not significantly different from 1.000 (p〈0.20), demonstrating the reliability of distal tubular puncture. The mean distal N-GFR of 27.9±5.3 nl/min was significantly smaller (p〈0.001) than the proximal N-GFR of 35.1±8.0 nl/min. The existence of the proximal-distal N-GFR difference thus is confirmed and two possible artifacts eliminated. The best explanation remains the operation of a tubulo-glomerular feedback mechanism. A current point of dispute is the effect of alterations in intratubular pressure (ITP) on N-GFR. Collection of tubular fluid at ITPs below the previously measured free flow pressure (FFP) resulted in a change of N-GFR of 0.45 nl/min· cm H2O. In contrast, fluid collection at ITPs greater than the FFP resulted in a change of N-GFR of 1.48 nl/min· cm H2O. We conclude that although N-GFR is sensitive to ITP changes in both directions, pressure decreases are of little practical importance for the determination of N-GFR whereas intratubular pressure increases are to be avoided.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00592688
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  • 2
    Electronic Resource
    Electronic Resource
    Technical problems in the micropuncture determination of nephron filtration rate and their functional implications (1971)
    Springer
    Pflügers Archiv 329 (1971), S. 307-320 
    Details
    ISSN: 1432-2013
    Keywords: Nephron Filtration Rate ; Saline Diuresis ; Intratubular Pressure ; Retrograde Contamination ; Sampling Pipettes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The theory of a functional coupling between distal tubular fluid composition and glomerular filtration rate implies that the blockade of flow at a proximal site should lead to a marked increase of GFR. This potential alteration of steady state GFR was studied by comparing the influence of sampling from distal or proximal sites on the filtration rate of identical nephrons. During antidiuresis an average GFR of 25.2 nl/min±7.5 S.D. was found in distal collections, while proximally collected samples gave an average GFR of 34.5 nl/min±8.4 S.D. This difference of 9.3 nl/min is highly significant (p〈0.001). During saline diuresis a mean nephron GFR of 41.6 nl/min±5.0 was found by distal sampling and of 45.3 nl/min±5.4 by proximal sampling (p〉0.05). The proximal-distal difference in nephron GFR is interpreted to indicate the operation of a tubulo-glomerular feedback control system. Thus, a true steady-state GFR probably cannot be obtained by proximal fluid collection. Even in the presence of high intratubular pressures and unusually short oil blocks no evidence of sample contamination by retrograde fluid flow past an injected oil block was obtained. The application of a counter-pressure to the sampling pipette which has been recommended by Gertzet al. [5] as a means to standardize fluid collections, was found to lead to abnormally high intratubular pressures. The reason for this finding appears to be an unexpectedly high and inconstant tip resistance to flow during fluid flow into the pipette.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00588002
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  • 3
    Electronic Resource
    Electronic Resource
    Renal and single-nephron function is comparable in thiobutabarbitone- and thiopentone-anaesthetised rats (1993)
    Springer
    Pflügers Archiv 424 (1993), S. 224-230 
    Details
    ISSN: 1432-2013
    Keywords: Rat ; Renal function ; Micropuncture ; Blood gases ; Anaesthesia ; Thiopentone ; Thiobutabarbitone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The thiobutabarbitone(TB, Inactin)-anaesthetised rat is an extremely widely used preparation for the study of renal function at the whole-organ and nephron levels. The recent withdrawal of TB from the market has made it essential to find an anaesthetic producing experimental conditions as similar as possible to TB to allow comparison of past and future data. Blood gas analysis, clearance and micropuncture studies were therefore performed in rats anaesthetised with TB or the related thiobarbiturate thiopentone (TP) (both 100 mg/ kg body weight) to establish whether the latter meets this requirement. Both barbiturates caused similar transient respiratory depression and acidosis. Mean values (TP versus TB) over the total 8-h observation period for glomerular filtration rate (0.94 versus 1.05 ml/min), urine flow (3.8 versus 4.4 μl/min) and K+ excretion (0.98 versus 1.18 μmol/min) were slightly lower (P〈0.05) in TP rats, whereas renal blood flow (6.26 versus 6.24 ml/min), filtration fraction (0.31 versus 0.34) and Na+ excretion (0.11 versus 0.098 μmol/min) did not differ. The single-nephron filtration rate (SNGFR) (42.1 versus 41.1 nl/min) and fractional reabsorption (42% versus 47%), both measured in the proximal tubule, did not differ, although in the TP group SNGFR rose with time (4.4%/h) whereas the fractional reabsorption did not change significantly; in the TB group SNGFR was constant but fractional reabsorption declined with time (1.5%/h). Fractional reabsorption up to the distal convoluted tubule declined with time, this was more pronounced in the TP group. SNGFR measured at this site did not differ between TP and TB (30.3 versus 30.1 nl/min) but increased with time with TP (2.7%/h). Although renal function under TP is somewhat less stable than under TB, the differences are minor and, given that the latter is also characterised by non-steady-state conditions, it is concluded that TP is a reasonable replacement for TB.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00384346
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  • 4
    Electronic Resource
    Electronic Resource
    Micropuncture studies on the renal handling of 2,4-diamino-6,7-dimethylpteridine (1979)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 306 (1979), S. 287-293 
    Details
    ISSN: 1432-1912
    Keywords: 2.4-diamino-6.7-dialkylpteridine ; Diuretics ; Micropuncture ; Tubular transport ; Rat kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The excretion of the diuretic substance DADMP (2.4-diamino-6.7-dimethylpteridine) and of DMP (6.7-dimethylpterin) was studied on single nephrons of the rat kidney using microperfusion and microinjection techniques. In the proximal tubule only DADMP was reabsorbed to a significant degree. Fractional reabsorption rate was independent of the load applied and the permeability constant was found to be 2.2·10−4 cm·s−1. Similar results were obtained in nephrons in which the substances, with inulin, were injected from middle proximal tubular puncture sites and recovered in the urine. DMP appeared in the urine quantitatively and simultaneously with the injected inulin. DADMP recovery, however, was only 20–30% of the injected load during the injection period and after 2 h some 70% was recovered from the urine of both kidneys. The reabsorbed fractions were independent of the loads applied, which varied between 2·10−13 mol·min−1 and 10−9 mol·min−1. A comparison of the microperfusion and the microinfusion data suggests that the reabsorption of DADMP occurs predominantly in the proximal convolution, and it appears that the differences between the renal handling of DMP and DADMP are explicable by their different lipid solubilities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00507116
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of carbohydrate ingestion and hormonal responses on ratings of perceived exertion during prolonged cycling and running (1999)
    Springer
    European journal of applied physiology 80 (1999), S. 92-99 
    Details
    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
    URL: http://dx.doi.org/10.1007/s004210050563
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  • 6
    Electronic Resource
    Electronic Resource
    Saliva immunoglobulins in elite women rowers (2000)
    Springer
    European journal of applied physiology 81 (2000), S. 222-228 
    Details
    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
    URL: http://dx.doi.org/10.1007/s004210050034
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  • 7
    Electronic Resource
    Electronic Resource
    Gross error detection when variance-covariance matrices are unknown (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 1335-1341 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Equations introduced here identify measurement biases and process leaks, when gross errors exist in measured process variables and the variance-covariance matrix of the measurements, Σ, is unknown. Σ is estimated by the sample variance, S, using process data.For an unknown Σ, the global test statistic is the well-known Hotelling T2 statistic. Its power function has a noncentral F-distribution. For component tests used for specific identification of measurement biases and nodal leaks, two tests are presented with Σ unknown. The first test is independent of the number of component tests, k, and is given by a statistic with an F-distribution. The second test depends on k and has a student t-distribution. The power functions for both component tests are provided. Process examples and a Monte Carlo simulation study presented demonstrate the use and performance of these statistical equations in identifying biases and process leaks.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390810
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  • 8
    Electronic Resource
    Electronic Resource
    Unbiased estimation of gross errors in process measurements (1992)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 38 (1992), S. 563-572 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new approach to gross error detection provides unbiased estimates and 100(1-α)% simultaneous confidence intervals of process variables when biased process measurements and process leaks exist. Presented in this article are estimation equations for process variables, as well as equations that help identify biased measurements and process leaks. These equations include the power function for a global test, and two types of α-level component tests and their power functions. Important strengths and weaknesses of this approach are compared to those of the serial compensation strategy, in particular, by varying the significance level (α), the variance-covariance matrix (Σ), the size of measurement bias (δ), the number of biased variables, and the sample size (N). Accuracy of δ estimation and performance in detecting the presence of process leaks (γ) are also evaluated and compared. The proposed approach has unique features that can provide a basis for improving the reconciliation of variables in process operations.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690380410
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  • 9
    Electronic Resource
    Electronic Resource
    Fractionating condensation and evaporation in plate-fin devices (1986)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 32 (1986), S. 1116-1124 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model that describes fractionation with condensation and evaporation in a plate-fin device has been formulated. It is capable of evaluating profiles of composition, temperature, and flow rate for both liquid and vapor streams in an extended surface device. The device may be adiabatic or nonadiabatic and the surface may be incompletely wetted. Compared to experimental measurements, the model predictions showed ± 1 number of transfer unit deviation along the length of the device. The predictions of the top and bottom flow rate ratio showed a 5-10% deviation for adiabatic and condensation runs and a 25% deviation for evaporation runs.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690320708
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  • 10
    Electronic Resource
    Electronic Resource
    Solid-liquid-vapor phase behavior of the methane-carbon dioxide system (1962)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 8 (1962), S. 537-539 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The phase behavior of the methane-carbon dioxide system has been determined experimentally along the solid-liquid-vapor locus. Pressure-temperature measurements were made along this locus from the triple point of carbon dioxide to -284°F. Compositions of the vapor phase along the solid-liquid-vapor locus were determined with sampling techniques over a composition range of 0.1 to 12% carbon dioxide. Liquid-phase compositions were obtained from crystal-point determinations on eleven methane-carbon dioxide mixtures ranging from 0.16 to 20% carbon dioxide.With the pressure-temperature for the solid-liquid-vapor locus as the termination locus of the dew and bubble data of Donnelly and Katz (2), consistent liquid- and vapor-phase compositions were obtained over the remaining concentration range.Changes in the pressure-temperature relationship of the solid-liquid-vapor locus caused by using a methane stock containing 0.56 mole % nitrogen are also reported.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690080423
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