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  • Electronic Resource  (4)
  • 1995-1999  (4)
  • Amiloride  (2)
  • Inorganic Chemistry  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Cystic fibrosis and non-cystic-fibrosis human nasal epithelium show analogous Na+ absorption and reversible block by phenamil (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 19-24 
    Details
    ISSN: 1432-2013
    Keywords: Key words Cystic fibrosis ; Human nasal epithelium ; Primary culture ; Epithelial Na+ channel ; Amiloride ; Phenamil
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Transepithelial short-circuit current (I SC), potential (V T) and resistance (R T) of confluent monolayers of human nasal epithelium cultured from patients with and without cystic fibrosis (CF) were measured. In our Ussing chamber experiments with monolayers derived from non-CF and CF patients neither I SC (non-CF: 14.1 ± 1.0 μA/cm2, n = 77; CF: 16.7 ± 1.5 μA/cm2, n = 42), nor R T (non-CF: 288 ± 15 Ω· cm2; CF: 325 ± 20 Ω· cm2) showed any significant differences, only V T showed moderate but significant different values (non-CF: –3.6 ± 0.4 mV; CF: –5.6 ± 0.7 mV, respectively). Total I SC in CF cells was nearly completely inhibited by amiloride (92 ± 9.6%), while in non-CF tissue amiloride-insensitive conductances mediated a considerable amount of the I SC (36.3 ± 6.1%), indicating a lower activity of amiloride-sensitive Na+ conductances in non-CF cells. In both tissues the amiloride-sensitive I SC could also be blocked by the amiloride analogues benzamil, phenamil and 5-(N-ethyl-N-isopropyl)2’,4’-amiloride (EIPA) with different affinities. However, amiloride had a significant lower affinity in CF tissue (half-maximal blocker concentration, K 1/2 = 586 ± 59 nM) compared with non-CF tissue (K 1/2 = 294 ± 22 nM). Astonishingly, phenamil, a blocker which irreversibly blocks all epithelial Na+ channels hitherto described, inhibited the Na+ conductances of human nasal epithelium in a completely reversible way, but nevertheless with high affinity (non-CF: K 1/2 = 12.5 ± 1.2 nM; CF: K 1/2 = 17.1 ± 1.1 nM). Even in high doses none of these blockers had any effect on intracellular Ca2+ concentration as measured with Fura-2. From these findings, we conclude that the epithelial Na+ conductances of human CF nasal epithelium show modified regulation or are functionally different from those of other tissues.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050358
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  • 2
    Electronic Resource
    Electronic Resource
    cAMP-activation of amiloride-sensitive Na+ channels from guinea-pig colon expressed in Xenopus oocytes (1996)
    Springer
    Pflügers Archiv 431 (1996), S. 913-922 
    Details
    ISSN: 1432-2013
    Keywords: Key wordsXenopus oocytes ; Guinea-pig colon ; Na+ channel ; Single-channel analysis ; Amiloride ; Benzamil ; cAMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Guinea-pig distal colonic mRNA injection into Xenopus laevis oocytes resulted in expression of functional active epithelial Na+ channels in the oocyte plasma membrane. Poly(A)+ RNA was extracted from distal colonic mucosa of animals fed either a high-salt (HS) or a low-salt (LS) diet. The electrophysiological properties of the expressed amiloride-sensitive Na+ conductances were investigated by conventional two-electrode voltage-clamp and patch-clamp measurements. Injection of poly(A)+ RNA from HS-fed animals [from hereon referred to as HS-poly(A)+ RNA] into oocytes induced the expression of amiloride-sensitive Na+ conductances. On the other hand, oocytes injected with poly(A)+ RNA from LS-fed animals [LS-poly(A)+ RNA] expressed a markedly larger amount of amiloride-blockable Na+ conductances. LS-poly(A)+ RNA-induced conductances were completely inhibitable by amiloride with a K i of 77 nM, and were also blocked by benzamil with a K i of 1.8 nM. 5-(N-Ethyl-N-isopropyl)-amiloride (EIPA), even in high doses (25 μM), had no detectable effect on the Na+ conductances. Expressed amiloride-sensitive Na+ channels could be further activated by cAMP leading to nearly doubled clamp currents. When Na+ was replaced by K+, amiloride (1 μM) showed no effect on the clamp current. Single-channel analysis revealed slow gating behaviour, open probabilities (P o) between 0.4 and 0.9, and slope conductances of 3.8 pS for Na+ and 5.6 pS for Li+. The expressed channels showed to be highly selective for Na+ over K+ with a permeability ratio P Na/P K 〉 20. Amiloride (500 nM) reduced channel P o to values 〈 0.05. All these features make the guinea-pig distal colon of LS-fed animals an interesting mRNA source for the expression of highly amiloride-sensitive Na+ channels in Xenopus oocytes, which could provide new insights in the regulatory mechanism of these channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050085
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  • 3
    Electronic Resource
    Electronic Resource
    Die Ammonolyse von (NH4)2GeF6. Darstellung und Struktur von NH4[Ge(NH3)F5] (1997)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1529-1534 
    Details
    ISSN: 0044-2313
    Keywords: Formation of NH4[Ge(NH3)F5] ; structure ; ammonolysis ; ir spectrum ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ammonolysis Reaction of (NH4)2GeF6. Synthesis and Structure of NH4[Ge(NH3)F5](NH4)2GeF6 reacts with ammonia to yield NH4[Ge(NH3)F5] at 280°C. The reaction path was elucidated by in situ time and temperature resolved X-ray powder diffraction. NH4[Ge(NH3)F5] crystallizes isostructurally to NH4[Si(NH3)F5] in the tetragonal space group P4/n (No. 85) with lattice constants a = 619.41(1) pm and c = 724.70(1) pm. The germanium atom is coordinated by five fluorine atoms and the nitrogen atom of the ammonia molecule. The ammonium cation is located on the Wyckoff position (2 a) in P4/n. The crystal structure is stabilized by extensive hydrogen bonding.
    Notes: (NH4)2GeF6 reagiert mit Ammoniak bei 280°C zu NH4[Ge(NH3)F5]. Der Reaktionsverlauf wurde in situ mit Hilfe der zeit- und temperaturaufgelösten Röntgenpulverdiffraktometrie verfolgt. Das so dargestellte NH4[Ge(NH3)F5] kristallisiert isostrukturell mit NH4[Si(NH3)F5] in der tetragonalen Raumgruppe P4/n (Nr. 85) mit den Gitterkonstanten a = 619,41(1) pm und c = 724,70(1) pm. Dabei ist das Germaniumatom verzerrt oktaedrisch von fünf Fluoratomen und dem Stickstoffatom des Ammoniakmoleküls koordiniert. Das Ammoniumion liegt auf der Tetraederpunktlage (2 a) in P4/n. Die Verbindung wird durch Wasserstoffbrückenbindungen stabilisiert.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19976231010
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  • 4
    Electronic Resource
    Electronic Resource
    Zeit- und temperaturaufgelöste Röntgenpulverdiffraktometrie: Die Reaktion von (NH4)2SnF6 mit Ammoniak (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 621 (1995), S. 617-623 
    Details
    ISSN: 0044-2313
    Keywords: Formation of Sn(NH3)2F4 ; ammonolysis ; thermal decomposition of (NH4)2SnF6 ; time and temperature resolved x-ray diffractometry ; in situ x-ray diffractometry ; solid state reactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Time and Temperature Resolved in situ X-Ray Powder Diffractometry. The Reaction of (NH4)2SnF6 with AmmoniaThe thermal decomposition of (NH4)2SnF6 under an atmosphere of ammonia is reported. The complicated reaction paths were illucidated by time and temperature resolved in situ x-ray powder diffractometry. It is shown that this technique is a powerful tool to observe structural changes during reaction. It offers also a valuable access to thermodynamic and kinetic data for solid state and gas phase reactions. (NH4)2SnF6 decomposes under ammonia below room temperature to NH4F and amorphous SnF4 · x NH3. At a temperature of 80°C an intermediate product, (NH4)4SnF8, is formed, which decomposes at 140°C into (NH4)2SnF6 and NH4F. At 250°C (NH4)[Sn(NH3)F5] and Sn(NH3)2F4 are formed. The latter crystallises C-centered monoclinic with lattice constants a = 844.1(5) pm, b = 630.5(3) pm, c = 520.2(3) pm and b̃ = 114.02(7)°. At 330°C a further decomposition yields SnF2(NH2)2 with a C-centered monoclinic cell and lattice constants a = 1 069(7), b = 325.3(2), c = 504.8(3) pm and b̃ = 105.83(7)°. Finally above 500°C tin metal is formed.
    Notes: Der komplizierte Verlauf der Reaktion von NH3 mit (NH4)2SnF6 wird mit der zeit- und temperaturaufgelösten Röntgendiffraktometrie verfolgt. Dabei erweist sich diese Methode als ideale Technik, um Veränderungen in der Struktur während der Reaktion aufzuzeichnen und ebenfalls thermodynamische und kinetische Daten zu gewinnen. (NH4)2SnF6 zersetzt sich schon bei 25°C unter trockenem NH3-Gas zu NH4F und einem röntgenamorphen Ammoniakat SnF4 · x NH3. Ab 80°C bildet sich (NH4)4SnF8 als Zwischenprodukt, das sich ab 140°C wieder in (NH4)2SnF6 und NH4F zersetzt. Bei 250°C entstehen NH4[Sn(NH3)F5] und Sn(NH3)2F4. Letzteres kristallisiert monoklin C-zentriert mit den Gitterkonstanten a = 844,1(5) pm, b = 630,5(3) pm, c = 520,2(3) pm und b̃ = 114,02(7)°. Ab 330°C erhält man SnF2(NH2)2. Aus dem Pulverdiffraktogramm ergibt sich eine C-zentrierte monokline Elementarzelle mit a = 1 069(7), b = 325,3(2), c = 504,8(3) pm und b̃ = 105,83(7)°. Bei noch höheren Temperaturen erfolgt die Zersetzung zu Zinn.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19956210419
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