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  • 1
    ISSN: 1432-1041
    Keywords: aspirin ; salicylic acid ; low-dose aspirin pharmacokinetics ; platelet function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of low-dose aspirin and the resulting salicylic acid were studied in 6 healthy volunteers. Each received a single 50-mg dose of (1) oral modified release capsules, (2) oral solution and (3) intravenous solution. The volunteers also received 50 mg modified release capsules daily for 6 days to determine the effect on collagen, ADP and arachidonate induced platelet aggregation and thromboxane production, and to compare the pharmacokinetics after repeated dosing with the parameters obtained after the single dose. The formulation and route of administration profoundly influenced several pharmacokinetic parameters for aspirin: the maximum concentration (Cmax, ng·ml−1) was 221 and 191 after modified release for single and chronic dosing respectively, 1323 after the oral solution and 6000 after intravenous injection; the time to achieve this maximum concentration (tmax, h) was 3.42 and 3.02 after modified release for single and chronic dosing respectively, and 0.29 after the oral solution; the area under the plasma drug concentration versus time curve (AUC, µg·h·ml−1) was 0.38 and 0.27 after modified release single and chronic dosing respectively, 0.68 after the oral solution and 1.57 after intravenous injection. The elimination of aspirin after the two solutions was at least biphasic. The terminal phase rate constant ranged from 1.52 h−1 after intravenous injection to 1.88 h−1 after the oral modified release form. The absorption of the oral forms of aspirin was complete as reflected by the total recovery of the doses as salicylic acid in urine. The pharmacokinetic parameters for salicylic acid showed similar tmax and Cmax for the oral solution and intravenous injection but, as for aspirin, Cmax was least and tmax greatest when the modified release form was used. After 7 days of modified release aspirin platelet aggregation and thromboxane formation in response to collagen and arachidonate were markedly inhibited. There was no inhibition of ADP-induced aggregation, but thromboxane production in response to ADP was abolished.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1420-908X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We have investigated some aspects of the regulation of production of rat platelet activating factor (PAF)in vitro. Suspensions of unseparated (PLC1), mast cell-depleted (PLC2), or mast cell (MC)-enriched rat peritoneal lavage cells (PLC) were analyzed for PAF content by extraction at alkaline pH. PAF activity extracted from PLC1 varied inversely with viable cell concentration: at 1×106 cells/ml, 32±9.3 PAF units, decreasing to 11.2±9.5 units at 10×106 cells/ml, and no activity at higher concentrations. Incubation of PLC1 in Tyrode's buffer or acetylsalicylic acid (ASA), but not salicylate, resulted in a time-dependent loss of PAf activity. Mean PAF activity of PLC2 was similar to that in PLC1, while no PAF activity was extractable from MC. Co-incubation with MC extracts inhibited PAF activity of PLC1 extracts in a dose-dependent fashion. Ultracentrifugation of PAF-containing samples led to a loss of all PAF activity in PLC1 extracts, suggesting the association of PAF activity with subcellular components. PAF appears to be derived from a non-MC population of rat PLC, is not extractable from rat PLC in the presence of ASA and is inhibited by MC extracts. These studies suggest that ASA regulates PAF availability unrelated to its effect on cylcooxygenase and that MC membrane products directly inhibit PAF activity from rat PLC.
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1752-7325
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 284 (1980), S. 151-153 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A thin section of the Estherville meteorite containing a large area of continuous anisotropic taenite (240 ´500 mm) was obtained from the Museum of Natural History, Smithsonian Institution, Washington, DC. The thin section also contains other areas that show optically anisotropic taenite in ...
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 652-657 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nature of the atomic structure and the characteristics of both line and planar defects in decagonal quasicrystals of as-cast Al62Cu20Co15Si3 were studied by means of conventional diffraction contrast and high-resolution electron microscopy. Two types of dislocations were observed. The magnitude and direction of the Burgers' vector of type A dislocations and the Burgers' vector direction of type B dislocations were determined. The direction of the displacement vector of the planar faults was defined.
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  • 6
    ISSN: 0741-0581
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 75 (1999), S. 3793-3795 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of nanometer-scale Cu metal particles in an amorphous SiO2 film was observed under a finely focused, intense electron beam in a dedicated scanning transmission electron microscope. Annular dark-field images show that the particle illuminated by the beam grows at the expense of surrounding Cu particles. Electron energy-loss spectroscopy was used for identifying the oxidation states of particles containing Cu atoms. An electric-field induced diffusion model explains the growth of metal particles in a dielectric medium. © 1999 American Institute of Physics.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 2795-2797 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spatial distribution of Mg solute in polycrystalline, single-phase Al2O3 has been obtained, using a secondary ion imaging technique. Segregation of Mg to the Al2O3 grain boundaries is clearly observed—strong evidence that the principal role of MgO is to reduce the grain boundary mobility via a solute-drag mechanism. In addition, Mg (dopant) and Ca (impurity) are shown to cosegregate, shedding further light on magnesium's ability to stabilize microstructural evolution in Al2O3. © 1995 American Institute of Physics.
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