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  • pharmacokinetics  (25)
  • Glutamate synthase  (5)
  • Springer  (30)
  • American Association for the Advancement of Science
  • Oxford University Press
  • PANGAEA
  • 2020-2023
  • 2000-2004
  • 1980-1984  (30)
  • 1970-1974
  • 2001
  • 1983  (30)
Collection
Publisher
  • Springer  (30)
  • American Association for the Advancement of Science
  • Oxford University Press
  • PANGAEA
Years
  • 2020-2023
  • 2000-2004
  • 1980-1984  (30)
  • 1970-1974
Year
  • 1
    ISSN: 1432-1041
    Keywords: cimetidine ; intravenous infusion ; pharmacokinetics ; peptic ulcer ; duration of infusion ; acute dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The use of cimetidine administered by bolus intravenous injection to critically ill patients has been associated with serious cardiac arrhythmias, due presumably to high initial plasma concentrations. The aim of this study was to determine the range of infusion times of a single 200 mg dose of cimetidine which would avoid high initial drug concentrations while maintaining a duration of effective concentrations no less than that resulting from bolus injection. Computer simulations of both maximum plasma cimetidine concentrations and duration of effective plasma cimetidine concentrations versus duration of infusion were based on mean pharmacokinetic date from 6 peptic ulcer patients who had received cimetidine 200 mg i.v. over 5 min. The simulations indicated that to reduce maximum plasma cimetidine concentrations by at least 50%, while maintaining the duration of effective plasma concentrations, the infusion time should be at least 30 min and no longer than 4.5 h. The validity of the simulations was subsequently tested in 4 of the patients, who received cimetidine 200 mg i.v. over 30 min. The mean maximum plasma concentration for the 30 min infusion (4.57±0.53 µg/ml) was, as predicted, approximately half that corresponding to bolus administration in these patients (8.97±1.96 µg/ml). Moreover, the duration of effective concentrations for the infusion (1.43±0.28 h) was significantly greater than that for the 5 min infusion (1.21±0.31 h). We suggest that where an acute intravenous dose of cimetidine (200 mg) is indicated, it should be administered over at least 30 min rather than as a bolus.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 25 (1983), S. 567-568 
    ISSN: 1432-1041
    Keywords: astemizole ; ethanol ; antihistamine ; pharmacodynamics ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The effects of astemizole (10 mg daily for 7 days) on the kinetics and CNS depressant activity of ethanol have been examined in a double-blind cross-over study agonist placebo in 7 volunteers. There was no significant change in the elimination rate or AUC of the plasma ethanol concentration-time curve after astemizole. Central nervous system effects of ethanol as monitored by visual analogues of sedation, visual discrimination, pursuit rotor and reaction time were also unaffected by astemizole pretreatment.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 24 (1983), S. 349-352 
    ISSN: 1432-1041
    Keywords: diltiazem ; pharmacokinetics ; intravenous dose ; oral dose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The kinetic profile of diltiazem, a novel calcium antagonist, was studied in 12 volunteers following oral (60 mg) and intravenous (15 mg) administration. After i.v. administration biphasic elimination was observed, with a distribution half-life of 0.3±0.2 h and an elimination half-life of 3.1±1.0 h; the apparent volume of distribution was 5.3±1.71/kg and the total clearance was 1.28±0.48 l/kg/h. After the oral dose the elimination phase had a half-life of 3.2±1.3 h. The absolute bioavailability of diltiazem ranged from 24 to 74% (mean 42±18%). The interindividual variation may be explained by a variable first pass effect.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 134 (1983), S. 98-103 
    ISSN: 1432-072X
    Keywords: Ammonia assimilation ; Chlorobium vibrioforme f. thiosulfatophilum ; Photosynthetic bacteria ; Glutamine synthetase ; Glutamate synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phototrophic green sulphur bacterium Chlorobium vibrioforme f. thiosulfatophilum assimilated ammonia via glutamine synthetase and glutamate synthase when grown with ammonia up to 30 mM, but above this level glutamate dehydrogenase was the key enzyme. Glutamine synthetase purified 42-fold was found to be adenylylated. The γ-glutamyltransferase activity of the enzyme was markedly inhibited by alanine, glycine, serine and lysine, and these amino acids in various combinations showed cumulative inhibition. Adenine nucleotides also inhibited enzyme activity, especially ATP. Glutamate synthase purified 222-fold had a maximum absorption at 440 nm which was reduced by sodium dithionite, and the enzyme was inhibited by atebrin indicating the presence of a flavin component. The enzyme had specific requirements for NADH, α-ketoglutarate and l-glutamine, the K m values for these were 13.5, 270 and 769 μM respectively. Glutamate synthase was sensitive to feedback inhibition by amino acids, adenine nucleotides and other metabolites and the combined effects of these inhibitors was cumulative.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 11 (1983), S. 183-187 
    ISSN: 1573-8744
    Keywords: nonlinear regression ; parameter estimation ; invariance ; transformation ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract It is shown that when one nonlinear regression model is a reparametrization of a second model, the parameter estimates, and their standard errors, for one model can be obtained directly from those obtained from fitting the other model.
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  • 6
    ISSN: 1573-8744
    Keywords: naltrexone ; controlled release ; pharmacokinetics ; gas chromatography ; biodegradable copolymer delivery system ; release rate quantitationin vivo ; Loo-Riegelman method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Naltrexone release rates from a controlled release delivery system have been quantitated over a time period greater than one month in the monkey. The method requires calibration of the pharmacokinetic parameters of each monkey utilizing an intravenous bolus dose and assay of unchanged naltrexone levels in plasma as a function of time after dosing. Also required are periodic plasma levels of unchanged naltrexone obtained subsequent to administration of the delivery system. Release rates are then calculated as well as the total amount released. Application of the methodology to a biodegradable copolymer naltrexone delivery system in three monkeys showed an initial release rate of 3– 8% of the dose per day over the first 3– 5 days followed by a slow, rather constant release rate of 1– 3% per day from day 5 to the time of the last measurable plasma sample (36– 43 days). Comparison of alternative calculation methods using both experimental and simulated plasma naltrexone data verified the accuracy of the release rate calculations. The sum of the calculated total amount of naltrexone released plus the assayed amount remaining in the delivery system after removal from the animal accounted for 91– 94% of the administered dose in the two monkeys in which complete data were obtained.
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  • 7
    ISSN: 1432-2048
    Keywords: Chloroplast (O2 evolution) ; Glutamate synthase ; Glutamine metabolism ; 2-Oxoglutarate metabolism ; Oxygen evolution (chloroplast) ; Spinacia (glutamate synthase)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Intact chloroplasts prepared from summer-grown spinach plants supported (aspartate plus 2-oxoglutarate)-dependent O2 evolution but not (glutamine plus 2-oxoglutarate)-dependent O2 evolution. The former activity, which was sensitive to amino oxyacetate, was attributed to transaminase activity and reduction of the resulting oxalo-acetate to malate using H2O as eventual electron donor. A reconstituted chloroplast system which included chloroplast stroma, thylakoid membranes, ferredoxin and NADP(H) supported O2 evolution in the presence ofl-glutamine and 2-oxoglutarate at rates of 15–22 μmol mg-1 chlorophyll h-1 although lower rates were obtained with material from winter-grown plants. Activity was not observed in the absence of ferredoxin and omission of NADP(H) decreased activity by 40%. The reaction was associated with the production of 0.49 mol O2 mol-1 2-oxoglutarate consumed and up to 0.46 mol O2 mol-1 glutamine supplied. The reaction, which was inhibited by azaserine but not by methionine sulphoximine or amino oxyacetate, was attributed to light-coupled glutamate synthase (EC 1.4.1.13) with H2O serving as eventual electron donor. Activity was not affected significantly byl-malate. The reconstituted system also supported O2 evolution in the presence of nitrite, oxaloacetate, (aspartate plus 2-oxoglutarate) and oxidised glutathione.
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  • 8
    ISSN: 1432-2048
    Keywords: Ammonia assimilation ; Chloroplast ; Glutamate synthase ; Glutamine synthesis ; Glutamine synthetase ; Spinacia (ammonia assimilation)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract (Ammonia plus 2-oxoglutarate)-dependent O2 evolution by intact chloroplasts was enhanced three- to five fold by 2 mM L- and D-malate, attaining rates of 9–15 μmol mg-1 Chl h-1. Succinate and fumarate also promoted activity but D-aspartate and, in the presence of aminooxyacetate, L-aspartate inhibited the malate-promoted rate. A reconstituted chloroplast system supported (ammonia plus 2-oxoglutarate)-dependent O2 evolution at rates of 6-11 μmol mg-1 Chl h-1 in the presence of MgCl2, NADP(H), ADP plus Pi (or ATP), ferredoxin and L-glutamate. The concentrations of L-glutamate and ATP required to support 0.5 V max were 5 mM and 0.25 mM, respectively. When the reaction was initiated with NH4Cl, O2 evolution was preceded by a lag phase before attaining a constant rate. The lag phase was shortened by addition of low concentrations of L-glutamine or by preincubating in the dark in the presence of glutamate, ATP and NH4Cl. Oxygen evolution was inhibited by 2 mM azaserine and, provided it was added initially, 2 mM methionine sulphoximine. The (ammonia plus 2-oxoglutarate)-dependent O2 evolution was attributed to the synthesis of glutamine from NH4Cl and glutamate which reacted with 2-oxoglutarate in a reaction catalysed by ferredoxin-specific glutamate synthase using H2O as the ultimate electron donor. The lag phase was attributed to the establishment of a steady-state pool of glutamine. L-Malate did not affect the activity of the reconstituted system.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 24 (1983), S. 521-524 
    ISSN: 1432-1041
    Keywords: sotalol ; beta-adrenoceptor antagonist ; pregnancy ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary Sotalol, a beta-adrenoceptor blocking drug, was administered to 6 healthy pregnant volunteers between 32–36 weeks gestation and when at least 6 weeks post-partum. On both occasions, each volunteer was given sotalol 100 mg intravenously and 400 mg orally in randomised order with at least a 1 week washout period between. Plasma samples were analysed for sotalol using a fluorometric method and the pharmacokinetic profiles investigated. The systemic clearance of sotalol was significantly greater in the antenatal period (2.4±0.3 ml/min/kg) than in the post-natal phase (1.5±0.1 ml/min/kg). The apparent volume of distribution was similar in the two periods: the elimination half-life was 6.6±0.6h ante-natally and 9.3±0.7h post-natally after intravenous drug but the trend for faster elimination was not significant. The elimination half-life after oral administration (about 10h) and bioavailability (about 90%) were not altered significantly by pregnancy. It is suggested that the more rapid clearance of sotalol in pregnancy may be due to increases in renal plasma flow and glomerular filtration rate.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 24 (1983), S. 549-556 
    ISSN: 1432-1041
    Keywords: dibromosulfophthalein ; pharmacokinetics ; plasma levels ; urinary excretion ; biliary excretion ; biliary fistula ; enterohepatic circulation ; hepatic transport test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of dibromosulfophthalein (DBSP), the 3,6-dibromo analogue of BSP, was studied in 7 patients with a biliary fistula, 52 h after cholecystectomy, and in 6 gynaecological patients with an indwelling urethral catheter, following extirpation of the uterus i.e. with an intact enterohepatic circulation. Plasma protein binding determined by ultrafiltration was 98–99% up to a concentration of 700 µg/ml. After an intravenous bolus injection of DBSP 5 mg/kg, a biexponential plasma decay was found in both groups, with a rapid initial t1/2 of 2–6 min and a slow secondary phase of 33–109 min (mean 66 min) in the cholecystectomy patients, and 10–30 min (mean 19 min) in the gynaecological patients. The biliary excretion rate varied considerably between the patients and was highly correlated with bile flow. Biliary output amounted to a maximum of 86% of the dose in 24 h. The excretion rate curves showed ascending and descending phases, the mean terminal t1/2 being 65 min. Urinary excretion was 3–11% of the dose in 8 h in the gynaecological patients (mean 6%) and 6–31% in the cholecystectomy group (mean 16%). Renal clearance of unbound DBSP was about ten-times greater than the glomerular filtration rate, which indicates tubular secretion. A two compartment model with elimination from the peripheral and central compartments was selected because of these data. Analysis of the plasma-disappearance curves indicated an initial plasma clearance of 500–600 ml/min, which suggests that hepatic uptake will be very dependent on flow. Steady state (biliary) clearance was about 400 ml/min in the gynaecological group and approximately half that in the cholecystectomy patients; V1 tended to be higher and V2 to be lower in the latter group. It is concluded that biliary excretion rate of DBSP in patients with a biliary fistula is probably depressed by the postoperative bile drainage and the lack of enterohepatic cycling of bile salts.
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