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  • 1
    ISSN: 1432-1017
    Keywords: Key wordsAcholeplasma laidlawii ; Phase equilibria ; Intact membranes ; Total lipid extracts ; Hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract Acholeplasma laidlawii strain A-EF22 was grown in a medium supplemented with 75 µm α-deuterated palmitic acid (16:0-d 2) and 75 µm α-deuterated oleic acid (18:1c-d 2), or with 150 µm 18:1c-d 2. The fatty acids were incorporated into the membrane lipids and 2H NMR spectra were recorded from intact membranes, total lipid extracts, and the combined glucolipid and neutral lipid fractions of a total lipid extract. The lipids in intact membranes form a bilayer structure up to at least 70 °C. The same result was obtained with membranes digested with pronase, which removes a large fraction of the membrane proteins. A reversed hexagonal liquid crystalline (HII) phase was formed below 70 °C by the total lipid extracts hydrated with 20 and 30% (w/w) water; in the presence of 40% (w/w) water only one of the extracts formed an HII phase below 70 °C. The HII phase was formed at higher temperatures with an increasing water content. However, only a lamellar liquid crystalline (L α ) phase was formed up to 70 °C by the total lipid extracts when the water concentrations were 50% (w/w) or higher. The temperature (T LH) for the L α to HII phase transition in the combined glucolipid and neutral lipid fractions was only 2–3 °C lower than for the total lipids, and the phospholipids thus have a very modest influence on the T LH value. Physiologically relevant concentrations of Ca2+ and Mg2+ ions did not affect the phase equilibria of total lipid extracts significantly. It is concluded from comparison with published data that the membrane lipids of the cell wall-less bacterium A. laidlawii have a smaller tendency to form reversed nonlamellar phases than the membrane lipids of three bacterial species surrounded by a cell wall.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1041
    Keywords: Key words Fluticasone propionatei ; HPA-axis; bud esonide ; asthma ; children ; corticosteroids ; systemic effects ; plasma cortisol suppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Abstract Objective: To compare the systemic potency of inhaled fluticasone propionate delivered via Diskhaler® (FP-DH), and inhaled budesonide delivered via Turbuhaler® (BUD-TBH) over the clinically recommended dose range using plasma cortisol suppression as a marker for systemic activity. Methods: The systemic potency was examined in a dose-response study in 81 healthy male volunteers. The study was of an open, randomized, parallel-group (four groups) design, where two treatments were given in crossover fashion within each group. FP-DH and BUD-TBH were given b.i.d. for 7 days (14 doses): 100 and 100 μg (group 1); 200 and 200 μg (group 2); 500 and 400 μg (group 3); 1000 and 800 μg (group 4). There was a washout period of 7 days within each treatment group. All doses were administered at 08:00 and 20:00 hours. Multiple plasma cortisol samples were taken every 2 h over 24-h periods prior to randomization (baseline) and during steady state (i.e., the last two dosing intervals). Cortisol suppression was determined by comparing average plasma concentrations of cortisol before and during treatment. Dose-response curves for cortisol suppression were analyzed using multivariate non-linear regression (Hill modeling). Results: Multiple dosing for 7 days with FP-DH and BUD-TBH resulted in dose-dependent cortisol suppression by both drugs, most pronounced at the two highest dose levels. FP-DH-induced suppression was 41% at 500 μg and 86% at 1000 μg b.i.d., while that induced by BUD-TBH was 19% at 400 μg and 47% at 800 μg b.i.d. Statistically significant differences were found when comparing the two steroids at these two dose levels. Doses producing 50% of maximum suppression (ED50) were estimated at 833 μg b.i.d. for BUD-TBH and 479 μg b.i.d. for FP-DH. This gave an estimated relative cortisol suppression over the dose range of 1.74:1 (FP-DH:BUD-TBH). ED50 values, estimated from cortisol concentrations at 08:00 hours (12 h after the last dose), were 1212 μg b.i.d. for BUD-TBH and 527 μg b.i.d. for FP-DH giving a relative cortisol suppression of 2.30:1 (FP-DH:BUD-TBH). Fourteen subjects on the highest FP-DH dose and 3 at the next highest dose had morning plasma cortisol levels below the lower reference limit. No subject taking budesonide, however, had morning plasma cortisol levels below the reference limit. Analysis of the time for return to pretreatment baseline levels showed that cortisol suppression, 12–24 h after the last dose, was statistically significant compared with the baseline for the highest dose of FP-DH but not for any of the BUD-TBH doses. Conclusions: The results of the present study show that FP-DH suppresses plasma cortisol more than BUD-TBH on a equivalent basis with regard to both magnitude and duration.
    Type of Medium: Electronic Resource
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