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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Naunyn-Schmiedeberg's archives of pharmacology 357 (1997), S. 25-31 
    ISSN: 1432-1912
    Keywords: Key wordsγ-Mangostin ; 5-Hydroxytryptamine ; 5-Hydroxytryptamine 2A receptor antagonist ; Rabbit aorta ; Rat coronary ; Rabbit platelet
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract γ-Mangostin, purified from the fruit hull of the medicinal plant Garcinia mangostana caused a parallel rightwards shift of the concentration/response curve for the contraction elicited by 5-hydroxytryptamine (5-HT) in the rabbit aorta (pA2 = 8.2) without affecting the contractile responses to KCl, phenylephrine (α1) or histamine (H1). The perfusion pressure response of rat coronary artery to 5-HT (5-HT2A) was reduced concentration dependently by γ-mangostin (IC50 = 0.32 μM). 5-HT amplified, ADP-induced aggregation of rabbit platelets (5-HT2A) was inhibited by γ-mangostin (IC50 = 0.29 μM), whereas that induced by thrombin was not affected, nor did γ-mangostin affect 5-HT-induced contraction of the guinea-pig ileum (5-HT3)in the presence of 5-HT1, 5-HT2 and 5-HT4 receptor antagonists. Furthermore, 5-HT-induced contraction of the rat fundus (5-HT2B) and 5-HT-induced relaxation of the rabbit aorta in the presence of ketanserin (5-HT1) and carbachol-induced contraction of the guinea-pig ileum (muscarinic M3) were not affected by γ-mangostin (5 μM). γ-Mangostin inhibited [3H]spiperone binding to cultured rat aortic myocytes (IC50 = 3.5 nM). The K d for [3H]spiperone binding was increased by γ-mangostin (3 nM) from 11.7 to 27.4 nM without affecting B max. These results suggest that γ-mangostin is a novel competitive antagonist, free from a nitrogen atom, for the 5-HT2A receptors in vascular smooth muscles and platelets.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0630
    Keywords: 61.70 ; 78.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract By component analyses of positron lifetime spectra in quenched gold, it was found that positrons are strongly trapped by stacking fault tetrahedra (SFT) at which the lifetime is about 160 ps remarkably smaller than that for monovacancies (∼200 ps) or divacancies (∼220 ps). Positron lifetimes at small vacancy clusters were also estimated in relation to the nucleation process of SFT, with the aid of computer simulation of kinetics of vacancy clustering during quenching and on subsequent isochronal annealing. The results show that large atomic relaxation occurs in small vacancy clusters among which pentavacancies have the largest open-space, thereby having the lifetime of about 230 ps larger than that of trior tetra-vacancies (∼160ps). It is also suggested that tetra- and penta-vacancies act as prenuclei for stable nuclei of SFT consisting of six or more vacancies.
    Type of Medium: Electronic Resource
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