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  • 1
    Electronic Resource
    Electronic Resource
    Sequential histamine inhalations cause increased bronchial histamine reactivity in guinea pigs: Role of platelets, thromboxanes and prostacyclin (1984)
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 327 (1984), S. 148-155 
    Details
    ISSN: 1432-1912
    Keywords: Acetylsalicylic acid ; Bronchial obstruction ; Guinea pigs ; Histamine aerosol ; Histamine receptor antagonists ; Prostacyclin aerosol ; Platelets ; Thromboxane synthetase inhibitors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Groups of 6–15 guinea pigs sensitized to ovalbumin were challenged by repeated inhalations of a constant histamine dose at time 0, 10, 20, 60 and 70 min. Bronchial obstruction was measured by whole body plethysmography. The degree of bronchial obstruction increased from one challenge to the other reaching maximal values after 70 min. This increase of bronchial responsiveness to histamine after repeated histamine challenges was reduced by pretreatment with clemastine (histamine H1-receptor antagonist, 0.12 mg/kg i.p., n=7, P〈0.05) and more effectively by combined clemastine/cimetidine pretreatment (combined H1-H2-receptor antagonists, 0.12 resp. 10 mg/kg, n=7, P〈0.001); pretreatment with acetylsalicyclic acid (10 mg/kg orally) accelerated the increase of bronchial responsiveness to histamine (n=9, P〈0.01 at the second challenge), inhalation of prostacyclin (1 μg) prior to each histamine inhalation prevented the increase of bronchial histamine sensitivity totally (n=10, P〈0.001), whereas inhibition of thromboxane biosynthesis (imidazol, 10 mg/kg i.p., n=6; 4-[2-(1H-imidazol-1-yl)ethoxy]benzoic acid, 10 mg/kg i.p., n=9; imidazo(1,5-a)pyridine-5-hexanoic acid, 1 mg/kg i.p., n=8) as well as immunologic platelet depletion were ineffective in our test system. We conclude that prostacyclin inhibits the increase of bronchial responsiveness to histamine after sequential histamine inhalation challenges by a platelet independent mechanism. 1-(3-phenyl-2-propenyl)-1H-imidazol, the fourth type of thromboxane synthetase inhibitor tested (10 mg/kg i.p., n=15) showed specific effects which may be attributed to antihistamine functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00500910
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  • 2
    Electronic Resource
    Electronic Resource
    Interaction of high-affinity nucleotide binding sites in mitochondrial ATP synthesis and hydrolysis (1982)
    Springer
    Journal of bioenergetics and biomembranes 14 (1982), S. 479-498 
    Details
    ISSN: 1573-6881
    Keywords: Oxidative phosphorylation ; F1-ATPase ; nucleotide binding sites ; cooperativity ; nucleotide analogs ; fluorescence ; mechanism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Physics
    Notes: Abstract The present study contributes to the problem of the dynamic structure of mitochondrial F1-ATPase and the functional interrelation of so-called tight nucleotide binding sites. Nucleotide analogs are used as a tool to differentiate two distinct functional states of the membrane-bound enzyme, proposed to reflect corresponding conformational states; they reveal F1-ATPase as a “dual-state” enzyme: ATP-synthetase, and ATP-hydrolase. The analogs used are 3′-naphthoyl esters of AD(T)P, and 2′(3′)-O-trinitrophenyl ethers of AD(T)P. Both types of analogs act inversely to each other with respect to their relative effects on oxidative phosphorylation and on ATPase in submitochondrial vesicles. The respective ratios ofK i versus both processes are 250/1 compared to 1/170. It is also shown that in the presence of the inhibitory 3′-esters oxidative phosphorylation deviates from linear kinetics and that these inhibitors induce a lag time of oxidative phosphorylation depending on the initial pattern of nucleotides available to energized submitochondrial vesicles. The duration of the lag time coincides with the time course of displacement of the analog from a tight binding site. The conclusions of the study are: (a) the catalytic sites of F1-ATP-synthetase are not operating independently from each other; they rather interact in a cooperative manner; (b) F1-ATPase as a “dual-state” enzyme exhibits highly selective responses to tight binding of nucleotides or analogs in its “energized” (membrane-bound) state versus its “nonenergized” state, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00743073
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    Paper (German National Licenses)
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