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  • 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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    Paper (German National Licenses)
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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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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Dose-related effects of selective 5-HT2 receptor antagonists on slow wave sleep in humans (1990)
    Springer
    Psychopharmacology 101 (1990), S. 568-569 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02244239
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Slow wave sleep and 5-HT2 receptor sensitivity in generalised anxiety disorder: a pilot study with ritanserin (1992)
    Springer
    Psychopharmacology 108 (1992), S. 387-389 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF02245128
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    Paper (German National Licenses)
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