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  • Electronic Resource  (6)
  • Polymer and Materials Science  (4)
  • Benzamil  (2)
  • 1
    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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  • 2
    Electronic Resource
    Electronic Resource
    Ion transport across leech integument (1993)
    Springer
    Journal of comparative physiology 163 (1993), S. 153-159 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF00263601
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  • 3
    Electronic Resource
    Electronic Resource
    Herstellung makroporöser Pellets aus Aluminiumoxid (1977)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 49 (1977), S. 42-42 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330490110
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  • 4
    Electronic Resource
    Electronic Resource
    Fabric Forming Systems. Von P. SCHWARTZ, T. RHODES und M. MOHAMED. Park Ridge, New Jersey, USA: Noyes Publications 1982. 175 S., 117 Abb., $ 24.00 (1983)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 34 (1983), S. 764-764 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1983.010341130
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  • 5
    Electronic Resource
    Electronic Resource
    Synthese einiger cyclodiurethane (1961)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 43 (1961), S. 98-105 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Several cyclic diurethanes were synthesized by two different methods applying RUGGLIZIEGLER'S principle of dilution. Only by preparation from diamines and diol-bis-chlorocarbonate good yields could be obtained. Using diols and diisocyanates as starting materials linear polyurethans were the main products.
    Notes: Mehrere Cyclodiurethane wurden unter Anwendung des RUGGLI-ZIEGLERschen Verdünnungsprinzips nach zwei verschiedenen Verfahren synthetisiert. Bei der Darstellung aus Diaminen und Diol-bis-chlorkohlensäureestern konnten die Verbindungen in guten Ausbeuten gewonnen werden. Dagegen werden bei Anwendung von Diolen und Diisocyanaten als Ausgangsmaterialien im wesentlichen lineare Polyurethane erhalten.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1961.020430109
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  • 6
    Electronic Resource
    Electronic Resource
    Synthese von Cyclo-urethanenHerrn Prof. Dr., Dr. h.c., Dr. e.h., Dr. h.c. OTTO BAYER zum 60. Geburtstag gewidmet (1962)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 57 (1962), S. 241-254 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The bis-chlorocarbonates of some oligo-ethylene glycols HO - (CH2CH2O)nH (n = 1-6) were reacted with hexamethylene diamine, m-toluylene diamine, p-phenylene diamine respectively to form the corresponding cyclic diurethanes. The dependency of the yield regarding the ringsize shows a maximum with 17 members in the ring. Also the catalyzed reaction of diisocyanates with diols was used for the preparation of cyclic urethanes.In the presence of di-n-butyltin-dilaurate exchange reactions were observed between hydroxyl-endgroups and urethane-groups as well as between urethane-groups.
    Notes: Die Bis-chlorkohlensäureester einiger Oligoäthylenglykole HO - (CH2CH2O)nH (n = 1-6) wurden mit Hexamethylendiamin, m-Toluylendiamin bzw. p-Phenylendiamin zu den entsprechenden Cyclodi-urethanen umgesetzt. Die Ausbeute in Abhängigkeit von der Ringgröße ergibt ein Maximum bei einer Ringgliederzahl von etwa 17. Ebenso wird die katalysierte Reaktion von Diisocyanaten mit Diolen zur Darstellung von Cyclo-urethanen benutzt.In Gegenwart von Di-n-butylzinndilaurat werden Austauschreaktionen sowohl zwischen Hydroxylendgruppen und Urethangruppen als auch zwischen Urethangruppen beobachtet.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1962.020570114
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