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  • LUNAR AND PLANETARY EXPLORATION  (3)
  • Nitrendipine  (2)
  • 1
    ISSN: 1432-1041
    Keywords: Felodipine ; Nitrendipine ; Nifedipine ; pharmacokinetics ; stereoselectivity ; enantiomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of racemic (rac) felodipine, rac-nitrendipine and nifedipine (all given as an oral dose of 20 mg in solution) have been investigated in a randomised cross-over study in 12 healthy male subjects using stereoselective assays. Both felodipine and nitrendipine exhibited stereoselective pharmacokinetics. On average, the AUCs of the active (S)-enantiomers of felodipine and nitrendipine were 139% and 104% higher than those of their optical antipodes, but the elimination half-lives of the enantiomers of each racemate were not different. The AUCs of nifedipine, rac-felodipine, rac-nitrendipine and of their enantiomers were highly correlated (all r〉0.83), suggesting closely related rate limiting steps in the in vivo first-pass metabolism of these high-clearance drugs. Stereoselectivity was only a minor contributor to inter-individual variability in the oral pharmacokinetics of these compounds in healthy subjects.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: Felodipine ; Nitrendipine ; Nifedipine ; enantiomers ; blood pressure ; heart rate ; concentration-effect relationship ; healthy volunteers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effects of racemic (rac) felodipine, rac-nitrendipine and nifedipine (all 20 mg solution p.o.) on non-invasively measured blood pressure and heart rate were investigated in a randomised, double-blind, cross-over study in 12 normotensive, young, healthy males. Compared to baseline values, heart rate increased more after rac-felodipine treatment (+47% at maximum) than rac-nitrendipine (+40%) and nifedipine (+38%); only small and variable changes in blood pressure were observed with any of the drugs. The baseline-corrected area under the heart rate-time curve up to 4 h after the administration of rac-felodipine was 197% and 180% larger than after nifedipine and rac-nitrendipine treatment, respectively. The effects on heart rate could be fitted individually to a sigmoidal Emax-model without hysteresis for all drugs under investigation. The relative potencies of the unbound drugs for their indirect effects on heart rate were 1:7:43 for nifedipine, rac-nitrendipine and rac-felodipine, respectively. The active (S)-enantiomers of felodipine and nitrendipine appeared to be 9-and 60-times as potent as nifedipine in this respect, assuming no (inter)activity of the (R)-enantiomers. Individual and mean changes in blood pressure were small, they were not related to plasma concentrations, and did not differ between treatments.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2019-07-13
    Description: The spectral reflectances of seventeen group H chondrites have been measured in the vacuum ultraviolet region, from 5 to 14 eV photon energy (250 to 90 nm, wavelength), as part of a survey of all meteorite types. Olivines, ortho-, and clino- pyroxenes are the three most important silicate minerals in these meteorites, and the spectrum of each mineral contains a distinct peak caused by a transition believed to be excitonic in nature and involving the valence-conduction bandgap. The energy at which this peak occurs varies as a function of mineral composition, and this variation has been determined from the spectra of a number of mineral standards. The observed positions of the olivine and pyroxene peaks in the meteorite spectra are compared to predicted positions based on the standard minerals.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 19, 1979 - Mar 23, 1979; Houston, TX
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  • 4
    Publication Date: 2019-07-13
    Description: The reflectance spectra of individual meteorites of all classes are being measured in the vacuum ultraviolet (VUV) spectral wavelength region from 89 to 248 nm to evaluate the potential of VUV spectroscopy as a remote sensing method for planetary studies. In the present investigation, specimens of 15 group L chondrites, 13 group LL chondrites, 7 group E chondrites, and 18 achondrites were studied. Spectra were measured of both polished thin sections and powders of the meteorites, where both were available. Attention is given to measurements of mineral standards, shock effects, and meteorite data. It is concluded that the VUV spectra of meteorites should provide a useful basis for comparisons with spectra of asteroids and comet nuclei taken from spacecraft. VUV spectroscopy should make it possible to identify the major minerals present in a meteorite or asteroid.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 17, 1980 - Mar 21, 1980; Houston, TX
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  • 5
    Publication Date: 2019-07-13
    Description: The spectral reflectances of materials have been measured in the vacuum ultraviolet region of the spectrum for possible planetary compositional remote-sensing applications. These materials, which include lunar and terrestrial silicate rocks and minerals, have one or more characteristic absorption peaks between about 8 and 13 eV. The peaks are visible in the spectra of powders and rough surfaces as well as polished surfaces. In lunar samples the most prominent peaks are at 10.25 eV, due to augite, and at 9.0 eV, due to anorthite. Spectra of lunar soils have minima between 6 eV (0.20 micron) and 8 eV (0.16 micron) depending on composition. Soils that have high reflectances in the visible have low reflectances in the VUV. The pyroxene content of the soils results in reflectance maxima at about 10 eV (0.12 micron). Peaks due to olivine and augite can be identified in the spectra of meteorites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 13, 1978 - Mar 17, 1978; Houston, TX
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