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  • Key words Amiloride  (2)
  • Porosity  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Effective porosity and specific yield of a sedimentary rock determined by a field tracing test using tritium as a tracer (1996)
    Springer
    Environmental geology 27 (1996), S. 170-177 
    Details
    ISSN: 1432-0495
    Keywords: Effective porosity ; Specific yield ; Migration ; Tracer test ; Porosity ; Tritium ; Finite element method ; Longitudinal dispersivity ; Sedimentary rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Effective porosity value was analyzed from the tritium concentration of sampled groundwater using a three-dimensional groundwater-flow and advection-dispersion code based on the finite element method. The effective porosity value was about 10%. Porosity values measured from core samples were 7–15%. The groundwater flow velocity estimated from the tritium concentrations was about 1 × 10−5 cm s−1. Therefore, during the low groundwater flow velocity condition, effective porosity and porosity values were the same. At the same test site, a 0.48% effective porosity value, determined by another tracer test injecting Br− solution into the aquifer during groundwater level change, was smaller than the porosity value when the flow velocity was 1.8×10−2 cm s−1. Thus the effective porosity value is concluded to be due to groundwater flow velocity. The specific yield value was calculated to be 0.6% by the total volume of tunnel seepage water and the total volume of the rock unsaturated during tunnel construction. However, as pore water continued to be drained after the groundwater level change was completed, the specific yield value became larger than 0.6%. Thus specific yield value is concluded to be due to drainage time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00770429
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Effective porosity and specific yield of a sedimentary rock determined by a field tracing test using tritium as a tracer (1996)
    Springer
    Environmental geology 27 (1996), S. 170-177 
    Details
    ISSN: 1432-0495
    Keywords: Key words Effective porosity ; Specific yield ; Migration ; Tracer test ; Porosity ; Tritium ; Finite element method ; Longitudinal dispersivity ; Sedimentary rock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Effective porosity value was analyzed from the tritium concentration of sampled groundwater using a three-dimensional groundwater-flow and advection-dispersion code based on the finite element method. The effective porosity value was about 10%. Porosity values measured from core samples were 7–15%. The groundwater flow velocity estimated from the tritium concentrations was about 1 × 10–5 cm s–1. Therefore, during the low groundwater flow velocity condition, effective porosity and porosity values were the same. At the same test site, a 0.48% effective porosity value, determined by another tracer test injecting Br– solution into the aquifer during groundwater level change, was smaller than the porosity value when the flow velocity was 1.8 × 10–2 cm s–1. Thus the effective porosity value is concluded to be due to groundwater flow velocity. The specific yield value was calculated to be 0.6% by the total volume of tunnel seepage water and the total volume of the rock unsaturated during tunnel construction. However, as pore water continued to be drained after the groundwater level change was completed, the specific yield value became larger than 0.6%. Thus specific yield value is concluded to be due to drainage time.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002540050048
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Low-amiloride-affinity Na+ channel in the epithelial cells isolated from the endolymphatic sac of guinea-pigs (1996)
    Springer
    Pflügers Archiv 433 (1996), S. 58-64 
    Details
    ISSN: 1432-2013
    Keywords: Key words Amiloride ; Endolymphatic sac ; Na+ conductance ; Whole-cell patch-clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  By using the whole-cell patch-clamp technique, an amiloride-sensitive Na+-selective conductance was found in epithelial cells from the endolymphatic sac (ES) epithelia of guinea-pigs. In the current-clamp configuration, the average resting membrane potential was –41.7±8.4 mV (n = 22). Application of amiloride at a concentration of 20 μM elicited a decrease in cation conductance that was responsible for a membrane hyperpolarization by 17.9±6.0 mV (n = 22). Substitution of N-methyl d-glucamine chloride (NMDG-Cl) for external NaCl led to a more significant membrane hyperpolarization by 28.4±8.3 mV (n = 22). At holding potential of –70 mV, amiloride and ethylisopropylamiloride (EIPA) blocked the inward current in a concentration-dependent manner over the range of concentrations of between 0.1 μM and 50 μM, with an inhibitory constant (K i) of 1.3±0.4 μM (n = 7) and 1.5±0.3 μM (n = 5), respectively. In the voltage-clamp configuration, substitution of NMDG-Cl for external NaCl significantly reduced the inward current (n = 9), indicating that the whole-cell conductance has a high permeability for Na+. Superfusion with 20 μM amiloride induced a significant reduction of the inward current, shifted the reversal potential from –39.4±8.8 mV to –60.4±10.5 mV (n = 12), and decreased the inward conductance from 5.0±1.3 nS to 3.7±1.5 nS (n = 12). The permeability ratio of Na+ over K+, calculated from the difference in reversal potential between the currents before and after application of amiloride, was approximately 5:1. Additionally, the conductance was not activated by application of forskolin, 3-isobutyl-1-methylxanthine (IBMX) and 8-bromo-cAMP (8-Br-cAMP). These findings suggest that a low-amiloride-affinity Na+ channel localized in the ES epithelial cells may be involved in uptake of Na+ in the ES.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050248
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  • 4
    Electronic Resource
    Electronic Resource
    Evidence for the presence of a Na+-H+ exchanger in the endolymphatic sac epithelium of guinea-pigs (1998)
    Springer
    Pflügers Archiv 436 (1998), S. 182-188 
    Details
    ISSN: 1432-2013
    Keywords: Key words Amiloride ; BCECF ; Ethylisopropylamiloride (EIPA) ; H+-efflux rate ; Intracellular pH
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The intracellular pH (pHi) of epithelial cells from the endolymphatic sac (ES) of the guinea-pig was measured microfluorometrically with the pH-sensitive fluorescent dye, 2′,7′-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF) to examine the presence of a Na+-H+ exchanger (NHE) in the ES epithelial cells. pHi recovery from acid loading with an NH4 +-prepulse in a nominally HCO3-free solution was dependent on extracellular Na+ ([Na+]o) and was inhibited by amiloride and its analogue ethylisopropylamiloride (EIPA), suggesting that a decreased pHi induced by an acute acid load may be equilibrated by a NHE. In the steady-state, amiloride had no effect on pHi, indicating that the NHE activity is low at the resting pHi. However, the intracellular acidification induced by the removal of [Na+]o was inhibited by the simultaneous application of amiloride. H+-efflux rate (J H, mean activity of NHE), which was calculated as the product of the recovery rate (dpHi/dt) from the acid loading and the intrinsic buffering capacity (βi) at the corresponding pHi, was decreased as pHi was increased. The concentration/response curve for the inhibition of initial J H by EIPA revealed an apparent 50% inhibitory constant (K i ) of 0.85 µM. Kinetic analysis of initial J H as a function of [Na+]o revealed a Michaelis-Menten constant (K m) of 24.14 mM for Na+-dependent H+ efflux. The results indicate that NHE in the ES epithelium belongs to an amiloride-sensitive subtype.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050621
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    Paper (German National Licenses)
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