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  • Electronic Resource  (12)
  • Inorganic Chemistry  (8)
  • Amiloride  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochimica et Biophysica Acta (BBA)/Biomembranes 1111 (1992), S. 159-164 
    ISSN: 0005-2736
    Keywords: (Colon) ; (Coprodeum) ; (Hen intestine) ; Amiloride ; Current-voltage relationship ; Expression ; Oocyte ; Sodium ion channel
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine , Physics
    Type of Medium: Electronic Resource
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  • 2
    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
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  • 3
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 163 (1993), S. 153-159 
    ISSN: 1432-136X
    Keywords: Na+ channels ; Amiloride ; Benzamil ; Noise analysis ; Leech, Hirudo medicinalis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The dorsal skin of the leech Hirudo medicinalis was used for electrophysiological measurements performed in Ussing chambers. The leech skin is a tight epithelium (transepithelial resistance = 10.5±0.5 kΩ· cm-2) with an initial short-circuit current of 29.0±2.9 μA·cm-2. Removal of Na+ from the apical bath medium reduced short-circuit current about 55%. Ouabain (50μmol·l-1) added to the basolateral solution, depressed the short-circuit current completely. The Na+ current saturated at a concentration of 90 mmol Na+·l-1 in the apical solution (K M=11.2±1.8 mmol·l-1). Amiloride (100 μmol·l-1) on the apical side inhibited ca. 40% of the Na+ current and indicated the presence of Na+ channels. The dependence of Na+ current on the amiloride concentration followed Michaclis-Menten kinetics (K i=2.9±0.4 μmol·l-1). The amiloride analogue benzamil had a higher affinity to the Na+ channel (K i=0.7±0.2 μmol·l-1). Thus, Na+ channels in leech integument are less sensitive to amiloride than channels known from vertebrate epithelia. With 20 mmol Na+·l-1 in the mucosal solution the tissue showed an optimum amiloride-inhibitable current, and the amiloride-sensitive current under this condition was 86.8±2.3% of total short-circuit current. Higher Na+ concentrations lead to a decrease in amiloride-blockade short-circuit current. Sitmulation of the tissue with cyclic adenosine monophosphate (100 μmol·l-1) and isobutylmethylxanthine (1 mmol·l-1) nearly doubled short-circuit current and increased amiloride-sensitive Na+ currents by 50%. By current fluctuation analysis we estimated single Na+ channel current (2.7±0.9 pA) and Na+ channel density (3.6±0.6 channels·μm-2) under control conditions. After cyclic adenosine monophosphate stimulation Na+ channel density increased to 5.4±1.1 channels·μm-2, whereas single Na+ channel current showed no significant change (1.9±0.2 pA). These data present a detailed investigation of an invertebrate epithelial Na+ channel, and show the similarities and differences to vertebrate Na+ channels. Whereas the channel properties are different from the classical vertebrate Na+ channel, the regulation by cyclic adenosine monophosphate seems similar. Stimulation of Na+ uptake by cyclic adenosine monophosphate is mediated by an increasing number of Na+ channels.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 74 (1912), S. 297-309 
    ISSN: 0863-1778
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 201 (1931), S. 41-74 
    ISSN: 0863-1786
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 623 (1997), S. 1529-1534 
    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
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 367 (1969), S. 40-43 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The course of interactions betweens some aliphatic nitriles and PCI5 has been investigated by means of 31P—NMR spectroscopy. Phosphazo compounds are formed, and chlorination occurs. Three examples of cis-trans isomeric phosphazo compounds were found.
    Notes: Der Ablauf von Reaktionen einiger aliphatischer Nitrile mit PCI5 wurde mit Hilfe der 31P—KMR-Spektroskopie untersucht. In allen Fällen entstehen Phosphazoverbindungen; außerdem tritt Chlorierung ein. Drei Beispiele von cis-trans-isomeren Phosphazoverbindungen wurden gefunden.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 473 (1981), S. 153-165 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Bor-Stickstoff-Verbindungen. 92. Spektroskopische untersuchungen an bis(dimethylamino)boranenDie schwingungsspektren von bis(dimethylamino)boranen [(CH3)2N]2BX mit X = H, D, CH3 und CD3 wurden aufgenommen; die Zuordnungen zu den Grundschwingungen stehen im Einklang mit den Ergebnissen einer Normalkoordinatenanalyse. Des weiteren werden einige kernmagnetische Resonanzdaten von Bis(dimethylamino)boranen diskutiert.
    Notes: The vibrational spectra of bis(dimethylamino)boranes, [(CH3)2N]2BX with X = H, D, CH3 or CD3 have been examined and assignments to the fundamental vibrations are supported by the results of a normal coordinate analysis. In addition, some nuclear magnetic resonance data on bis(dimethylamino)boranes are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 483 (1981), S. 51-62 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Bor-Stickstoff-Verbindungen. 94. Reaktionen von Dimethylaminoboranen mit PyrazolIn Abhängigkeit von den Reaktionsbedingungen führt die Umsetzung von Tris(dimethylamino)boran mit Pyrazol (Hpz) zu (CH3)2HNBpz3 (III) oder den Pyrazabolen B2pz4[N(CH3)2]2 (IV, cis- und trans-Isomeres), B2pz5N(CH3)2 (Va) oder B2pz6. Die Reaktion scheint über das äußerst kurzlebige [(CH3)2N]2Bpz und  -  insbesondere  -  monomeres (CH3)2NBpz2 zu verlaufen; letztere Verbindung kann massenspektroskopisch identifiziert werden. Im System Bis(dimethylamino)phenylboran-Pyrazol wurden (CH3)2HNB(C6H5)pz2 und das Pyrazabol B2pz3(C6H5)2N(CH3)2 (VII, cis- und trans-Isomeres) erhalten. Außerdem wurden einige Daten des Pyrazabols B2pz2(C6H5)2[N(CH3)2]2 erhalten, obwohl die Verbindung nicht im Reinzustand isoliert werden konnte. Die Existenz von monomerem (CH3)2NB(C6H5)pz konnte nachgewiesen werden.
    Notes: Depending on the reaction conditions, the interaction of tris(dimethylamino)borane with pyrazole (Hpz) yields (CH3)2HNBpz3 (III) or the pyrazaboles B2pz4[N(CH3)2]2 (IV, cis and trans isomer), B2pz5N(CH3)2 (Va), or B2pz6. There is evidence that the reactions proceed via the extremely short-lived [(CH3)2N]2 Bpz and, in particular, monomeric (CH3)2NBpz2; the latter species can be identified in the mass spectrometer. In the system bis(dimethylamino)phenylborane/pyrazole the species (CH3)2HNB(C6H5)pz2 and the pyrazabole B2pz3(C6H5)2N(CH3)2 (VII, cis and trans isomer) were obtained. Also, some data on the pyrazabole B2pz2(C6H5)2[N(CH3)2]2 were collected although the compound could not be isolated in the pure state. The existence of the monomer (CH3)2NB(C6H5)pz could be established.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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