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  • 1
    ISSN: 1432-1912
    Keywords: Clemizole ; Arrhythmia ; Antihistaminics ; Cell Membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The antihistaminic clemizole was studied as an antiarrhythmic in a preparation in which two arrhythmias of different nature and mechanism were produced in the right atrium of anesthetized dogs. One of the arrhythmias was a circus movement flutter induced by the method of Rosenblueth and García Ramos; the other, an ectopic focus induced by local application of aconitine in the auricular appendage, electrically isolated from the rest of the atrium. Clemizole selectively converted the flutter to sinus rhythm with little action on the coexistent aconitine dysrhythmia. It did not modify arterial pressure. In effective doses the wave length of the impulse was increased by prolongation of the refractory period without significant reduction in conduction velocity. Similarly, in subendocardial cells of isolated rat atria, clemizole in appropriate concentrations retards repolarization with little effect on the rate of depolarization. These results afford pharmacological evidence for the existence of atrial circus movement arrhythmias which can respond to prolongation of the refractory period unaccompanied by effects on other properties of the tissue. Other arrhythmias, self-sustained by the discharge of an ectopic focus, such as the tachysystole produced by aconitine, are not suppressed by similar increase in the refractory period.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Bradyrhizobium japonicum ; Nitrate ; Membrane-bound nitrate reductase ; Nitrate reductase mutants ; Microaerobiosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Native PAGE of Triton x-100-solubilized membranes from Bradyrhizobium japonicum strain PJ17 grown microaerobically (2% O2, v/v) in defined nitrate-containing medium resolved two catalytically active nitrate reductase (NR) species with apparent molecular masses of 160 kDa (NRI) and 200 kDa (NRII). NRI and NRII were also found in membranes from cells of strain PJ17 that were first grown in defined medium with glutamate and further incubated microaerobically in the presence of 5 mmol/l KNO3. However, only NRI was detected in cell membranes of strain PJ17 when nitrate was omitted from the microaerobic incubation medium. Four mutants unable to grow at low O2 tension in the presence of nitrate were isolated after transposon Tn5 mutagenesis. Membranes from mutants GRF110 and GRF116 showed mainly NRI, while the other two mutants, GRF3 and GRF4, expressed mostly NRII. These results indicate that the ability of B. japonicum PJ17 to grow under microaerobic conditions depends upon the presence of two membrane-bound NR enzymes whose synthesis seem to be independently induced by microaerobiosis (NRI) or by both microaerobiosis and nitrate (NRII).
    Type of Medium: Electronic Resource
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