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  • pharmacokinetics  (96)
  • photosynthesis  (46)
  • Springer  (142)
  • National Academy of Sciences
  • 2020-2024
  • 1990-1994  (142)
  • 2021
  • 1992  (142)
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  • 2020-2024
  • 1990-1994  (142)
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  • 1
    Digitale Medien
    Digitale Medien
    Effect of folding and feeding by Cnaphalocrocis medinalis on photosynthesis and transpiration of rice leaves (1992)
    Springer
    Entomologia experimentalis et applicata 63 (1992), S. 101-102 
    Details
    ISSN: 1570-7458
    Schlagwort(e): Cnaphalocrosis medinalis ; rice leaffolder ; Oryza sativa ; rice ; photosynthesis ; transpiration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00350352
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  • 2
    Digitale Medien
    Digitale Medien
    Assessment of Hg2+ toxicity to a N2-fixing cyanobacterium in long- and short-term experiments (1992)
    Springer
    BioMetals 5 (1992), S. 149-156 
    Details
    ISSN: 1572-8773
    Schlagwort(e): Hg2+ toxicity ; cyanobacterium ; Nostoc calcicola ; growth ; photopigments ; nucleic acids ; photosynthesis ; membrane integrity ; nutrient uptake ; enzymes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Toxicological responses of the filamentous N2-fixing cyanobacteriumNostoc calcicola Bréb. towards Hg2+ were studied to enumerate the decisive lethal events. In low-dose, long-term experiments (0.05–0.25 μm Hg2+, 10 days), photoautotrophic growth was severely inhibited with concurrent loss of photosynthetic pigments (phycocyanin〉chlorophyll α〉carotenoids) and nucleic acids. The termination of growth after a day 4 exposure to 0.25 μm Hg2+ has been attributed to the complete inhibition ofin vivo photosynthetic activity in the cyanobacterium (O2 evolution〉14CO2 incorporation). The elevated Hg2+ concentrations irreversibly damaged the cell membrance as observed under light microscopy, and as indicated by the leakage of intracellular electrolytes and phycocyanin. In high-dose, short-term experiments (0.5–20.0 μm Hg2+, up to 6 h), thein vivo activities of selected enzymes (glutamine synthetase 〉 nitrate reductase 〉 nitrogenase) were less inhibited by Hg2+ than the uptake of nutrient ions (NH 4 + 〉NO 3 − 〉PO 4 3− ).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01061321
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  • 3
    Digitale Medien
    Digitale Medien
    Role of pigments on algal communities and photosynthesis (1992)
    Springer
    Aquatic sciences 54 (1992), S. 321-330 
    Details
    ISSN: 1420-9055
    Schlagwort(e): Algal pigments ; algal communities ; photosynthesis ; Lake Lugano (Lago di Lugano)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A one-year study of phytoplankton, primary production and related physical and chemical factors was made in a Swiss basin of Lake Lugano (Lago di Lugano). The chlorophylls and 12 carotenoids were analyzed with a TLC technique. The carotenoid monitoring was considered to be particularly interesting, because the role of these pigments in freshwater algae is still very poorly documented by field studies. The dependence of photosynthesis on several factors was statistically evaluated. Evidence was found of light-adaptation phenomena. The variations of photosynthetic activity and efficiency largely depended on the light regime in the few days before the field observations and on the cellular content of chlorophylls and single carotenoids, whose concentrations in their turn were closely linked with light, temperature, average cell size, and with the actual species assemblage.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00878144
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  • 4
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of rufloxacin in healthy volunteers (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 101-105 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Rufloxacin ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The plasma and urine kinetics of rufloxacin were assessed in healthy volunteers after single (100, 200, 400 and 800 mg) and multiple (300 mg followed by 150 mg daily, Group 1, and 400 mg followed by 200 mg daily, Group 2) oral doses. The kinetics of a single oral dose of 800 mg was assessed in fasting and non-fasting subjects to assess the influence of food intake on drug absorption. The AUCs were 134, 266 and 375 μg · h · ml−1 after 100, 200 and 400 mg, respectively. The AUC after 800 mg p. o. was 715 μg · h · ml −1 in fasting subjects and 614 μg · h · ml−1 in non-fasting subjects. The parameters of the model and the mean renal clearance values indicated some departure from linearity in rufloxacin kinetics. After multiple doses the plasma drug levels during the 6th treatment day were similar to those after the first dose in Group 1 and were about 30–40% higher after the first dose in Group 2. The half-lives after the last dose were much shorter than those estimated in the single dose studies (33–36 h and 50–80 h, respectively).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314928
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  • 5
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of meropenem in subjects with renal insufficiency (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 535-538 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Meropenem ; Carbapenem ; pharmacokinetics ; uraemia ; haemodialysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of IV meropenem (500 mg over 30 min) has been studied in 6 healthy volunteers and 26 patients with various degrees of renal impairment. Blood samples were taken at different times over 24 h in healthy subjects and 36 to 48 h in uraemic patients, and four or five urine samples were collected over 24 or 48 h. Meropenem concentrations in plasma and urine were measured by a microbiological assay. The mean peak plasma concentration of meropenem ranged from 28 to 40 μg·ml−1 and was not affected by the degree of renal impairment. The terminal half-life of meropenem was approximately 1 h in subjects with normal kidney function and it was proportionately increased as renal function decreased. A significant linear relationship between total body clearance and creatinine clearance as well as between renal clearance and creatinine clearance was observed. The mean apparent volume of distribution at steady state was not significantly altered in uraemic patients. The mean cumulative urinary recovery of meropenem in healthy volunteers was 77% of the administered dose and it was significantly decreased in patients with renal impairment. Haemodialysis shortened the elimination half-life, from 9.7 h during the predialysis period to 1.4 h during the dialysis period. The dose of meropenem should be reduced in relation to the decrease in creatinine clearance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314864
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  • 6
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of mefloquine in the presence of primaquine (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 559-560 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Mefloquine ; Thai subjects ; pharmacokinetics ; Primaquine ; drug interaction ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314870
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  • 7
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of diphemanil methylsulphate in healthy subjects (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 689-691 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Diphemanil methylsulphate ; pharmacokinetics ; healthy subjects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetic parameters of oral diphemanil methylsulphate have been evaluated in six healthy male volunteers. Absorption of the drug was slow (tmax=2 to 4 h), the mean half-life was 8.35 h, and the amount of the drug recovered in urine within 48 h ranged from 0.6 to 7.4% of the administered dose. The results suggest low bioavailability, assuming that the drug is poorly metabolized.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265939
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  • 8
    Digitale Medien
    Digitale Medien
    Dose proportionality study of loperamide following oral administration of loperamide oxide (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 693-694 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Loperamide ; loperamide oxide ; diarrhoea ; pharmacokinetics ; dose-proportionality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of loperamide, after oral administration of increasing doses (1 to 16 mg) of loperamide oxide, has been investigated in 10 healthy male volunteers, using a randomised cross-over design. Comparison of the maximum plasma loperamide concentration and AUC demonstrated that the bioavailability of loperamide was proportional to the dose of loperamide oxide administered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265940
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  • 9
    Digitale Medien
    Digitale Medien
    Evaluation of the accuracy of a pharmacokinetically-based patient-controlled analgesia system (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 67-75 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Morphine ; Patient-controlled analgesia ; opioids ; pharmacokinetics ; bolus-elimination-transfer ; computer-assisted continuous infusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Bone marrow transplant patients having severe, prolonged oral mucositis pain (expected to last for one to three weeks) used a computer-controlled infusion system to self-administer morphine for pain control. Individual patient pharmacokinetic information, derived from a pretreatment bolus morphine dose, was used in a new bolus-elimination transfer algorithm to produce rapid adjustments of steady plasma morphine concentrations when the patient requested more or less drug. We evaluated the performance characteristics (bias and precision) of this pharmacokinetically based patient-controlled analgesic infusion system (PKPCA) in a group of 15 cancer patients over six to 14 days. Although we found a three- to fivefold pharmaco-kinetic variability in the tailoring morphine dose data, the PKPCA system was free of systematic bias (insignificant overall prediction error) during the patient-controlled infusions in this study population. The absolute prediction error was 19.9% for the group on the first study day and 25.6% over the entire study period (aggregate results; 6–14 days of continuous use). Two-thirds of the patients exhibited no bias throughout the study period, and individual bias in the others was symmetrically distributed (three patients with underpredictions and two overpredicted). Magnitude of prediction error during the patient-controlled morphine infusions was not related to the magnitude of pharmacokinetic deviation of individual subjects from group parameters. Our results indicate that this PKPCA system provides accurate control of plasma morphine concentration when used by patients to self-administer opioid for prolonged pain relief continuously over 1 to 2 weeks. Use of individual pharmacokinetic information, instead of population parameters, may account for superior performance characteristic of this computer-assisted continuous drug infusion system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02280757
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  • 10
    Digitale Medien
    Digitale Medien
    Steady state pharmacokinetic profile of indomethacin in elderly patients and young volunteers (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 77-80 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Indomethacin ; steady-state ; pharmacokinetics ; elderly
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The steady-state pharmacokinetic profile of indomethacin was examined in twelve healthy volunteers (4 m, 8 f; 20–34 y) and in 12 elderly subjects (7 m, 5 f; 70–88 y). Two formulations of indomethacin were examined, providing duplicate data for each subject group. The subjects received each formulation of indomethacin (25 mg tid) for 6 days in a single blind crossover fashion. On day 7, after an overnight fast, a final 25 mg dose of indomethacin was given and plasma concentrations measured over the following 12 h. Kinetic parameters Cpmin, tmx and AUC (0–12 h) were determined. There were no differences in the pharmacokinetic parameters between young and elderly subjects or between data for the two formulations of indomethacin. AUC values (μg · ml−1 · h), for example, for the two formulations in the young subjects were 5.85 and 6.85 while the values for the elderly subjects were 6.55 and 6.50 respectively. When each treatment period was considered independently there was a significant difference between young and elderly subjects with regard to compliance. The rates of non compliance (over and under compliance) using a capsule count technique were, however, low with a mean maximum value of 5.8% being recorded for the elderly subjects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02280758
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  • 11
    Digitale Medien
    Digitale Medien
    Pharmacokinetics and dialysability of isradipine in chronic haemodialysis patients (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 231-233 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Isradipine ; Haemodialysis ; pharmacokinetics ; dialysability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of isradipine, a calcium-channel blocker, have been studied in eight patients on chronic haemodialysis. A single oral dose of 5 mg was administered on both a non-haemodialysis and a haemodialysis day and the plasma concentrations of isradipine were analyzed. The mean cmax, tmax, AUC, and t1/2 in plasma on the non-haemodialysis day were 5.2 ng·ml−1, 1.4 h, 23.8 ng·h·ml−1, and 3.1 h, respectively. The dialysis clearance of isradipine was negligible (5.0 ml·min−1). The t1/2 values during haemodialysis were not significantly different from those observed during the same period post dose on the non-haemodialysis day. The study demonstrates that supplemental doses of isradipine are not necessary in these patients since isradipine is not significantly removed by haemodialysis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278492
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  • 12
    Digitale Medien
    Digitale Medien
    Disposition of quinine in plasma, red blood cells and saliva after oral and intravenous administration to healthy adult Africans (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 171-174 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Quinine ; Malaria ; pharmacokinetics ; red blood cells ; plasma ; saliva ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of quinine has been studied in ten healthy adult Africans after intravenous infusion and oral ingestion of a 500 mg dose. Blood and saliva samples were collected over 48 h and quinine in plasma, red cells and saliva was determined by HPLC. Quinine was rapidly and almost completely absorbed after an oral dose, with absorption half-life of 0.53 h, a tmax of 1–3 h and a bioavailability of 88%. Analysis of the i. v. data gave an apparent volume of distribution of 3.6 1·kg−1 and a plasma clearance of 0.19 l·kg−1·h−1. The concentration-time curves for plasma, red cells and saliva had declining phases were approximately parallel, giving a similar half-life that in all three media. The half-lives after the i. v. infusion also did not different from those after oral administration. The dose was well tolerated by both methods of administration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278479
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  • 13
    Digitale Medien
    Digitale Medien
    Binding of a metabolite of triflusal (2-hydroxy-4-trifluoromethylbenzoic acid) to serum proteins in rat and man (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 175-179 
    Details
    ISSN: 1432-1041
    Schlagwort(e): 2-hydroxy-4-trifluoromethylbenzoic acid (HTB) ; Triflusal ; triflusal metabolite (HTB) ; pharmacokinetics ; protein binding ; ultrafiltration ; binding constant
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary 2-hydroxy-4-trifluoromethylbenzoic acid (HTB) is the main active metabolite of the platelet anti-aggregant drug triflusal. Its binding to plasma proteins of rats and healthy volunteers in vitro and in vivo has been studied. Rats were given a single oral dose of 50 mg·kg−1 triflusal and the healthy volunteers received 300 mg as a single oral dose or a multiple dose regimen of 600 mg every 24 h and 300 mg every 8 h, both for 13 days. Protein-free HTB was obtained by ultrafiltration. Unbound and total HTB concentrations were determined by HPLC. HTB was primarily bound to albumin in plasma. The Scatchard plots suggested two types of binding sites for HTB on the albumin molecule. In rats, the binding constants (K=intrinsic affinity constant, n=number of binding sites) were K1=1.4×105 l·mol−1, n1=1.23, and K2=4.1×103 l·mol−1 and n2=3.77. The mean plasma concentration in rats after oral administration was 185 (37) μg·ml−1 (protein-free HTB: 2.44 (0.77)%). The binding constants in human plasma were K1=4.7×105 l·mol−1, n1=1.93, K2=4.3 l·mol−1 and n2=4.28. The plasma HTB concentration in man (n=8) was 35 μg·ml−1 (Cmax) after a single oral dose of triflusal 300 mg, 172.96 μg·ml−1 (Cmax·ss) during the multiple dosage regimen of 300 mg every 8 h, and 131 μg·ml−1 (Cmax·ss) during the multiple oral dose regimen of 600 mg every 24 h. Unbound HTB ranged from 0.27 to 0.43%, depending on dose. HTB had high affinity for plasma albumin, which was not saturable after therapeutic doses. It showed linear elimination.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278480
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  • 14
    Digitale Medien
    Digitale Medien
    Temporary reversal of serum to cerebrospinal fluid glycerol concentration gradient after intravenous infusion of glycerol (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 181-185 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Glycerol ; brain oedema ; serum ; cerebrospinal fluid ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Glycerol 50 g infused i. v. over 2 to 6 h is widely used to treat cerebral oedema in patients with acute stroke. Its transit through the blood-cerebrospinal fluid barrier in subjects with uninflamed meninges has now been examined. In 7 patients with an external ventriculostomy for occlusive hydrocephalus, each of whom was given 500 ml of a 10% solution IV over 4 h, serum and CSF were repeatedly sampled during and after the infusion and glycerol was measured enzymatically. The highest serum glycerol level of 191–923 mg/l was observed at the end of the infusion. The maximum CSF glycerol of 18.7–110.8 mg/l was attained 0–1 h after the end of the infusion. Elimination both from serum and CSF approximated a single-exponential decay; the elimination half-life from serum was 0.29–0.56 h compared to 1.03–3.68 h from CSF. In six of the seven cases there was a temporary reversal of the serum/CSF concentration gradient during glycerol elimination. The ratios of the AUCs of CSF and serum, which describe the overall penetration of glycerol into CSF, ranged from 0.09–0.31. In conclusion, the serum level of glycerol produced by giving 50 g IV glycerol over 4 h may not be sufficiently high reliably dehydrate to brain tissue in many patients, and the slow elimination of glycerol from the CSF may be related to the so-called rebound phenomenon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278481
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  • 15
    Digitale Medien
    Digitale Medien
    Formation and excretion of dipyrone metabolites in man (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 187-191 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Dipyrone ; Acetylation phenotype ; metabolism ; pharmacokinetics ; urinary excretion ; metabolite clearance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The formation and urinary excretion of the dipyrone metabolites, methylaminoantipyrine (MAA), aminoantipyrine (AA), formylaminoantipyrine (FAA) and acetylaminoantipyrine (AAA) were determined following administration of a single oral 1.0 g dose of dipyrone to 12 healthy volunteers. The AAA/AA plasma ratio showed that 3 subjects were slow and 9 were rapid acetylators. Pharmacokinetic parameters were determined separately for each group. A good correlation was found between the plasma and urine AAA/AA ratios. The renal clearance of the four metabolites was similar for both phenotypes. A significant difference in the rate of formation of dipyrone metabolites was found for AA, 0.25 (slow) vs 0.1 ml·min−1·kg−1 (rapid), and for AAA 0.75 (slow) vs 7.53 ml·min−1·kg−1 (rapid). There were comparable differences between slow and rapid acetylators in the AUC and the urinary excretion extrapolated to infinity for AA and AAA. The present results show that the kinetics of dipyrone metabolites in plasma and urine can provide a useful measure of the activity of the enzymes involved in their production.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278482
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  • 16
    Digitale Medien
    Digitale Medien
    Effect of salbutamol on digoxin pharmacokinetics (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 197-201 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Digoxin ; Salbutamol ; serum ; skeletal muscle digoxin ; pharmacokinetics ; drug interaction ; serum potassium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A single dose of the β2-adrenoceptor agonist salbutamol has previously been shown to decrease serum digoxin concentration in healthy volunteers. A possible explanation of the phenomenon is a β2-adrenoceptor-mediated increase in the specific binding of digoxin to skeletal muscle. The present study was undertaken to further elucidate the effect of salbutamol on the pharmacokinetics of digoxin in man. Nine volunteers were studied on two occasions during salbutamol or placebo treatment. On test days salbutamol, 4 μg·kg−1·h−1 or saline was infused for 10 h, preceded and followed by four and three days, respectively, of oral administration. A single i. v. injection of digoxin 15 μg·kg−1, was given 20 min after starting the infusion. At the end of the infusion a muscle biopsy was taken from the vastus lateralis. Blood samples for the analysis of serum digoxin and potassium were repeatedly taken over 72 h. Urine was collected over a period of 24 h for determination of the renal excretion of digoxin and potassium. The serum digoxin concentration, expressed as the AUC 0–6 h was 15% lower during salbutamol infusion than during saline infusion. Salbutamol caused significantly faster elimination of digoxin from the central volume of distribution to deeper compartments. Salbutamol had no effect on the renal clearance of digoxin. The skeletal muscle digoxin concentration tended to be higher (48%) during salbutamol compared to placebo treatment. The serum potassium concentration was significantly lower after salbutamol compared to placebo, as was the rate of renal excretion of potassium. The results support the hypothesis that the salbutamol-induced decrease in serum digoxin is caused by increased distribution of digoxin to skeletal muscle (and possibly other tissues), and that this may be secondary to a β2-adrenoceptor-mediated increase in Na-K-ATPase activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278484
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  • 17
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of nicorandil in patients with normal and impaired renal function (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 203-207 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Nicorandil ; pharmacokinetics ; angina pectoris ; uraemia ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of oral nicorandil 20 mg 12 hourly for 9 doses was evaluated in 21 hospitalized patients with angina pectoris due to coronary heart disease and with normal and impaired renal function. Patients were divided into 3 groups based on creatinine clearance (CLCr): GROUP I (n=6) 〉 80 ml/min, GROUP II (n=8) 20–80 ml/min, and GROUP III (n=7) 〈 20 ml/min. After the first dose, the total clearance of nicorandil (CL) value did not change with increasing renal failure and so was not dependent on creatinine clearance. After the last dose CL was 51 l·h−1 in Group I, 44 l·h−1 in Group II and 56 l·h−1 in Group III, and it was not related to creatinine clearance. The percentage of the dose excreted in the urine was 0.4%. No significant difference was noted in any of the other pharmacokinetic parameters examined in the three groups, not even on comparing values obtained on the first and last days of treatment. The findings suggest that there is no need to change the dose of nicorandil in subjects with different degrees of renal failure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278485
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  • 18
    Digitale Medien
    Digitale Medien
    The pharmacokinetics and pharmacodynamics of sublingual and oral alprazolam in the post-prandial state (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 439-443 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Alprazolam ; benzodiazepines ; pharmacokinetics ; pharmacodynamics ; sublingual dosage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We gave 12 healthy male volunteers 1 mg of alprazolam or placebo on three occasions after a standard breakfast in a double-blind, randomized, single-dose, three-way crossover study. The three trials were: (a) oral alprazolam and sublingual placebo; (b) oral placebo and sublingual alprazolam; (c) placebo by both routes. Plasma alprazolam concentrations during 24 h after each dose were measured by electron-capture gas-liquid chromatography. Peak plasma concentrations were reached later after sublingual than oral dosage (2.8 vs 1.8 h, P〈0.01). Other kinetic variables were not significantly different: peak plasma concentration, 11.3 vs 12.0 ng·ml−1; elimination half-life, 12.5 vs 11.7 h; and total area under the plasma concentration versus time curve, 197 vs 186 h·ng·ml−1. Pharmacodynamic measures showed that sublingual and oral alprazolam both produced sedation, fatigue, impaired digit symbol substitution, slowing of reaction time, and impairment of the acquisition and recall of information. These changes were initially observed at 0.5 h after dosage and lasted up to 8 h. In general the two routes were significantly different from placebo but not from each other.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280132
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  • 19
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of ethanol in plasma and whole blood: estimation of total body water by the dilution principle (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 445-448 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Ethanol ; whole blood ; plasma ; total body water ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of ethanol in plasma and whole blood have been investigated and the results used to estimate the volume of total body water (TBW) by means of the dilution principle. Fifteen men (mean age 62 y) were given 0.6 g ethanol/kg body weight as an intravenous infusion over 1 h. The peak concentration of ethanol in plasma was 120 mg·dl−1 compared to 108 mg·dl−1 for whole blood. The disappearance rate of ethanol from plasma was 18.6 mg·dl−1·h−1 compared to 17.0 mg·dl−1·h−1 for the whole blood concentration-time data. The apparent volume of distribution of ethanol (Vz) was 0.54 l·kg−1 according to plasma kinetics compared to 0.59 l·kg−1 for the kinetics derived from whole blood. The mean area under the curve (AUC) was 294 mg·dl−1×h for plasma kinetics compared to 266 mg·dl−1×h for whole blood. The TBW was 40.9 l or 50.9% of body weight for the plasma concentration-time data. This agreed well with the 40.3 l or 50.1% of body weight obtained using whole blood.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280133
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  • 20
    Digitale Medien
    Digitale Medien
    High dose oral methylprednisolone in patients with rheumatoid arthritis: pharmacokinetics and clinical response (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 85-88 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Methylprednisolone ; Rheumatoid arthritis ; bioavailability ; pharmacokinetics ; clinical response ; pulse steroid therapy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A commercially available 1.0 g intravenous (i.v.) dosage formulation of methylprednisolone, as the sodium hemisuccinate salt (Solu MedrolR, Upjohn) was administered both parenterally and orally (pulse steroid therapy) on separate occasions, to eight elderly (mean 65 y) patients with active rheumatoid arthritis. The relative oral bioavailability of the sterol was 69.2%. Elimination of methylprednisolone was prolonged when given orally; the mean residence times were 7.23 h and 3.94 h for oral and i.v. administrations, respectively. Clinical response to pulse steroid therapy was no different with respect to route of administration. There were no significant differences in standard clinical and laboratory assessments of disease activity when the two therapies were compared. Oral administration of methylprednisolone in patients requiring high-dose pulse steroid therapy is convenient and avoids the discomfort and inconvenience associated with i.v. administration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314925
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  • 21
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of IV and oral acetyl-L-carnitine in a multiple dose regimen in patients with senile dementia of Alzheimer type (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 89-93 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Acetyl-L-carnitine ; Senile Dementia of Alzheimer Type ; pharmacokinetics ; plasma concentration ; cerebrospinal fluid concentration ; carnitine metabolism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Acetyl-L-carnitine (ALC), a physiological component of the L-carnitine family, has been proposed for treating Alzheimer's disease in pharmacological doses. As this condition requires prolonged therapy, its kinetics has been examined after a multiple dose regimen, involving different routes of administration, in 11 patients suffering from Senile Dementia of Alzheimer Type. The study design comprised a 3-day basal observation period, sham treatment with repeated blood sampling; treatment with 30 mg·kg−1 i.v. given twice for 10 days (plasma kinetics was studied on the 7th day), and 50 days of 2.0 g/day p.o. given in three daily doses. Total acid soluble L-carnitine, L-carnitine and acetyl-L-carnitine in plasma and CSF were evaluated using an enantioselective radioenzyme assay. Short chain L-carnitine esters were calculated as the difference between total and free-L-carnitine. The plasma concentrations of individual components of the L-carnitine family did not change during the three days of the basal period, nor were they affected during the sham therapy period. Following the i.v. bolus injections, the plasma concentrations showed a biphasic curve, with average t1/2 of 0.073 h and 1.73 h, respectively. At the end of oral treatment, plasma acetyl-L-carnitine and L-carnitine short chain esters were significantly higher than during the run-in phase. The CSF concentrations paralleled those in plasma, suggesting that ALC easily crosses the blood-brain barrier. It is concluded that i.v. and oral administration of multiple doses of ALC can increase its plasma and CSF concentration in patients suffering from Alzheimer's disease.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314926
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  • 22
    Digitale Medien
    Digitale Medien
    Multiple dose kinetics of ofloxacin and ofloxacin metabolites in haemodialysis patients (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 95-99 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Ofloxacin ; Haemodialysis ; ofloxacin metabolites ; pharmacokinetics ; multiple doses ; dosage selection ; renal failure ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary 7 patients with end-stage renal disease on regular haemodialysis were treated orally with a loading dose of 200 mg ofloxacin and multiple maintenance doses of 100 mg per 24 h for 10 days. The pharmacokinetics of ofloxacin and its metabolites were studied at the end of the treatment period. Plasma and dialysate concentrations of ofloxacin and ofloxacin metabolites were measured by HPLC. Peak (3.1 mg·1−1) and trough levels (1.6 mg·1−1) and the AUC of ofloxacin were comparable to the values in healthy volunteers given 300 to 400 mg ofloxacin p.o. The mean half-life, determined in the dialysis-free interval (t1/2β) and during the haemodialysis session (t1/2HD), was 38.5 h and 9.9 h, respectively. Extrarenal clearance (32.7 ml·min−1) was unchanged as compared to that reported in healthy volunteers after a single dose of ofloxacin. The fractional removal by haemodialysis amounted to 21.5%. Two metabolites, ofloxacin-N-oxide and demethyl-ofloxacin, were detected in plasma. Despite prolonged t1/2β of both metabolites (66.1 and 50.9 h) and multiple doses of ofloxacin the peak concentrations of the metabolites reached only 14% and 5% of that of the parent drug, respectively. It is concluded that in patients on regular haemodialysis treatment the dosage adjustment employed resulted in safe and therapeutically favourable plasma concentrations. The observed accumulation of ofloxacin metabolites does not appear to have any toxic or therapeutic significance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314927
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  • 23
    Digitale Medien
    Digitale Medien
    The effects of a salicylate, ibuprofen, and naproxen on the disposition of methotrexate in patients with rheumatoid arthritis (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 121-125 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Methotrexate ; non-steroidal anti-inflammatory drugs (NSAIDs) ; interaction ; disposition ; adverse effects ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the pharmacokinetics of methotrexate in patients with rheumatoid arthritis concurrently treated with choline magnesium trisalicylate, ibuprofen, naproxen, or a non-NSAID analgesic (control treatment). The apparent systemic clearance of methotrexate was significantly reduced by all three treatments. Trisalicylate and ibuprofen both significantly reduced methotrexate renal clearance, but only the trisalicylate significantly displaced methotrexate from protein, increasing the fraction unbound by 28%. These data show that NSAIDs can affect the disposition of methotrexate, possibly increasing the potential for toxicity and necessitating dosage adjustments. However, large inter-subject variability precludes specific dosage recommendations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278469
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  • 24
    Digitale Medien
    Digitale Medien
    Effect of tetracycline on mefloquine pharmacokinetics in Thai males (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 567-569 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Mefloquine ; Tetracycline ; Thai subjects ; Thai subjects ; drug interaction ; pharmacokinetics ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The kinetics of a single oral dose of mefloquine given either alone or with tetracycline has been studied in 20 healthy Thai male volunteers. There was a significantly higher maximum whole blood mefloquine concentration after coadministration with tetracycline (1600 vs 1160 ng · ml−1), as well as a significantly reduced terminal half-life (14.4 vs 19.3 days), mean residence time (11.9 vs 16.0 days) and volume of distribution at steady state (13.3 vs 19.91 · kg−1). Although there was no significant change in the AUC from zero time to infinity, the AUC from zero time to 7 days was significantly increased by tetracycline (6.18 vs 4.76 μg · ml−1 · day). The changes in mefloquine disposition after tetracycline treatment are probably due to a reduction in enterohepatic recycling. The initial increase in mefloquine AUC without an apparent increase in side-effects suggests that this combination may have a place in the treatment of multi-drug resistant falciparum malaria.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02285105
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  • 25
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of cyclosporine in hyperlipidaemic long-term survivors of heart transplantation (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 161-165 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Cyclosporine ; Hyperlipidaemia ; heart transplantation ; fenofibrate ; fenofibric acid ; pharmacokinetics ; drug interaction ; nephrotoxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Cyclosporine (Cy) binds to lipoproteins in plasma. In order to test if its pharmacokinetics would be modified when efficient lipid-lowering treatment is introduced, a study has been done of Cy pharmacokinetics and any interaction with the lipid-lowering agent fenofibrate in hyperlipidaemic long-term, survivors of heart transplantation. Fenofibrate 200 mg once daily significantly reduced blood lipids (cholesterol 6.5 vs 7.7 mmol/l; apoprotein B 1.2 vs 1.6 g/l) but did not modify mean whole blood Cy trough levels (113 before fenofibrate vs 103 ng·ml−1), Cmax (812 ng·ml−1 by RIA and 757 ng·ml−1 by HPLC before fenofibrate versus 865 and 741 respectively, during fenofibrate); tmax (1.6 and 1.7 h before fenofibrate versus 1.4 and 1.4 h respectively), and t1/2 (13.9 and 11.1 h versus 9.5 and 10.7 h). The only adverse effect was an increase in creatinine (157 vs 145 mmol/l). Further studies are needed to investigate the mechanism of Cy-fenofibrate nephrotoxicity and to evaluate the long-term efficiency and safety of fenofibrate after heart transplantation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01740664
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  • 26
    Digitale Medien
    Digitale Medien
    Plasma thiamine concentrations after intramuscular and oral multiple dosage regimens in healthy men (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 219-222 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Thiamine ; pharmacokinetics ; analytical method ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A novel liquid chromatographic method for the determination of thiamine in plasma has been developed and has been used to study plasma thiamine concentrations after multiple dosage regimens for 11 days. The method involves purification, concentration and analytical separation of thiochrome on-line, using a switching column system. Ten healthy men were given 500 mg thiamine i.m. once a day (Group 1) and ten were given 250 mg p.o. every 12 h (Group 2). The times to reach steady state (7 and 5.6 days for Groups 1 and 2, respectively) were not different (P〉0.05). The mean elimination half-life was 1.8 days. The mean minimum steady-state concentration after the oral regimen (23 μg·l−1) was 78% of that after the intramuscular regime (29 μg·l−1).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278489
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  • 27
    Digitale Medien
    Digitale Medien
    Investigation of a possible pharmacokinetic interaction between ibopamine and isosorbide-5-mononitrate (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 549-552 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Ibopamine ; Isosorbide-5-mononitrate ; pharmacokinetics ; drug interaction ; healthy volunteers ; pharmacodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The possibility of a pharmacokinetic interaction between isosorbide-5-mononitrate (5-ISMN) and epinine, the active metabolite of ibopamine, has been investigated in 8 healthy male subjects given single doses of 200 mg ibopamine and 20 mg 5-ISMN, separately and together. The plasma 5-ISMN concentration-time profile was the same whether 5-ISMN was administered concomitantly with ibopamine or alone [AUC(o-t): 2.24 μg·ml−1·h after 5-ISMN alone, 2.16 μg·ml−1·h after 5-ISMN + ibopamine]. The plasma concentrations of total and free epinine and the urinary recovery of total epinine, homovanillic acid and dihydroxyphenylacetic acid, too, were not different when ibopamine was administered alone or concomitantly with 5-ISMN. The intake of ibopamine did not change the blood pressure and heart rate. The decrease in diastolic blood pressure induced by 5-ISMN was not influenced by concomitant intake of ibopamine. The observations suggest that in healthy volunteers there is no pharmacokinetic interaction between 5-ISMN and ibopamine.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314867
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  • 28
    Digitale Medien
    Digitale Medien
    Metamizole-furosemide interaction study in healthy volunteers (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 593-598 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Metamizole ; Furosemide ; prostaglandins ; drug interaction ; adverse effects ; pharmacokinetics ; pharmacodynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetic and pharmacodynamic interactions between metamizole (dipyrone) and furosemide were investigated in 9 of 12 healthy female subjects able to complete the study. They received oral metamizole 3×1 g for 3 days or placebo (cross-over) and on the last day of both study periods furosemide 20 mg IV. On the last two days a balanced sodium diet (120 mEq) and on Day 3 an oral water load (600 ml) were given. Metamizole significantly inhibited basal urine flow, whereas the fractional excretion of sodium and chloride and the 12 h-GFR remained unchanged. Metamizole significantly reduced furosemide clearance (175 vs 141 ml · min−1), furosemide-stimulated plasma renin activity (1.42 vs 0.79 ng AI · ml−1 · h−1) and the urinary excretion of prostacyclin metabolites and of prostaglandin F2α (by 70–81%). The renal clearance and terminal half-life of furosemide, peak renal chloride and volume excretion were unchanged. Thus, metamizole did not interact with the renal excretion and the diuretic effect of furosemide, although prostaglandin synthesis was significantly reduced.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265921
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  • 29
    Digitale Medien
    Digitale Medien
    Rectal bioavailability of 6-mercaptopurine in children with acute lymphoblastic leukaemia: partial avoidance of “first-pass” metabolism (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 619-622 
    Details
    ISSN: 1432-1041
    Schlagwort(e): 6-Mercaptopurine ; suppository ; bioavailability ; acute lymphoblastic leukaemia ; children ; interindividual variability ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Plasma levels and the area under the plasma concentration-time curve (AUC) values of 6-mercaptopurine (6-MP) were determined in a balanced crossover study of oral (powder) and rectal (macrogol suppository) administration to 5 children with acute lymphoblastic leukaemia (ALL). The AUC (538.6 ng · h · ml−1) after the rectal dose of 30 mg/m2 was approximately 1.5-times of that (365.5 ng · h · ml−1) after the oral dose of 87.5 mg/m2. The coefficients of variation of interindividual variability of the AUCs were 21.5% and 32.3%, respectively. The relative bioavailability of the macrogol suppository compared to the powder was approximately 4.39. These findings indicate that rectal administration of 6-MP could avoid the first-pass effect of this drug in the alimentary canal and/or liver, resulting in a large AUC of 6-MP, and so could reduce interindividual variability in plasma 6-MP concentrations. Rectal administration of 6-MP may be more effective than empirical oral dosing for the treatment of children with ALL, especially for patients with nausea and/or vomiting.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265925
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  • 30
    Digitale Medien
    Digitale Medien
    Rebound of plasma vancomycin levels after haemodialysis with highly permeable membranes (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 635-639 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Vancomycin ; Haemodialysis ; highflux membranes ; pharmacokinetics ; renal failure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Vancomycin is usually given only once a week to haemodialysis (HD) patients. If highly permeable dialysis membranes are used, however, high clearance values have been reported, so the aim of the study was to determine whether high clearance of vancomycin resulted in sufficient drug elimination to induce subtherapeutic plasma levels after one week. In 18 chronic HD patients, treated with polysulfone dialyzers (1.2 m2), the pharmacokinetics of vancomycin were studied after administration of 1 g. Concentrations were determined by fluorescence polarisation immunoassay. At a blood flow of 219 ml·min−1, HD clearance of vancomycin was 62.3 ml·min−1. Immediately after dialysis plasma concentrations were 38% lower than predialysis levels. However, marked rebound in the vancomycin level was observed 5 h later, resulting in plasma levels only 16% lower than prior to dialysis. 3 HD treatments in 1 week removed about one third of the initial dose. After one week 15 of 18 patients still had a therapeutic plasma level (〉5 μg·ml−1). In conclusion, polysulfone membranes show high clearance of vancomycin. However, transfer of drug from blood to dialysate appears to be faster than from tissues to blood. Because of a marked rebound in plasma level after treatment, therapeutic drug concentrations will still be present in most patients after one week.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265928
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  • 31
    Digitale Medien
    Digitale Medien
    Effect of treatment at night with S-1452, a thromboxane A2 receptor antagonist, on the morning rise in platelet aggregation (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 501-505 
    Details
    ISSN: 1432-1041
    Schlagwort(e): S-1452 ; thromboxane A2 receptor antagonist ; nocturnal dosage ; platelet aggregation ; circadian rhythm ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary It is well known that platelet aggregation shows a morning rise, which may contribute to the increase in the onset of ischaemic heart diseases during the morning period. The present study was undertaken to determine whether nocturnal dosage with S-1452, a thromboxane AZ receptor antagonist, would blunt the morning rise in platelet aggregability. S-1452 50 mg or placebo were given orally to 8 healthy subjects at 10.00 h (day trial) or 22.00 h (night trial) according to a cross-over design. Plasma concentrations of S-1452 and its metabolites, bisnor-( + )-S-145 and tetranor-(+ )-S-145, and platelet aggregation were determined during the 12-hour period following the dose. Mean plasma concentrations of S-1452, bisnor-( + )-S-145 and tetranor-(+ )-S-145 during the absorption phase were lower after the nocturnal dose than after the morning dose. The maximum plasma concentration and area under the plasma concentration-time curve of the compounds were also lower and the time to the maximum concentration were delayed after the treatment at night. A morning rise in platelet aggregation was observed following placebo treatment. The inhibitory effect of S-1452 on platelet aggregation was observed at 3 hours and persisted for up to 9 h in both trials. The results suggest that S-1452 is absorbed more slowly after the nocturnal dose than after the morning dose. However nocturnal treatment with 50 mg S-1452 may blunt the morning rise in platelet aggregability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02285091
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  • 32
    Digitale Medien
    Digitale Medien
    Intracolonic bioavailability of human calcitonin in man (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 527-531 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Calcitonin ; Colonic administration ; Bioavailability ; pharmacokinetics ; pharmacodynamics ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Human calcitonin (hCT) injected into the lumen of the descending colon of normal human subjects was absorbed within minutes and could be recognized intact in plasma as shown by RIA in combination with reverse-phase HPLC. The absorption was low and variable, with bioavailabilities ranging from 0.01% to 2.7% relative to intravenously administered hCT (area under the concentrationtime curve). With intravenous hCT serum calcium was lowered and the fractional urinary excretion of calcium, phosphorus, sodium and chloride was significantly stimulated. With the intracolonic hCT, the fractional urinary excretions of calcium, sodium and chloride were also marginally stimulated relative to intracolonic vehicle (placebo). In conclusion, hCT is absorbed intact from the colon, but the bioavailability is low and highly variable.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02285096
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  • 33
    Digitale Medien
    Digitale Medien
    Pharmacokinetic and blood pressure effects of carvedilol in patients with chronic renal failure (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 85-88 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Hypertension ; Carvedilol ; chronic renal failure ; pharmacokinetics ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetic and acute systemic haemodynamic effects of a single oral dose of 50 mg carvedilol has been studied in 24 hypertensive patients with chronic renal failure. The patients were stratified into 3 groups according to the creatinine clearance: I 51–90 ml · min−1; II 26–50 ml · min−1; III 4–25 ml · min−1. The area under plasma level time curve AUC, the elimination half-life t/12, the maximum plasma concentration Cmax, the time to peak concentration tmax were not significantly different between groups, whereas the amount of unchanged drug or metabolite excreted in urine Ae and the renal clearance CLR of carvedilol and its metabolites M2, M4, M5 were significantly decreased in Group III. Blood pressure and heart rate decreased in all 3 groups of patients after acute administration of 50 mg carvedilol. Mild adverse effects were reported in 6 patients. Despite a decrease in the renal clearance of carvedilol and of its metabolites with decreasing kidney function, its main pharmacokinetic parameters remained unchanged. The present results suggest that the dose of carvedilol need not be reduced in hypertensive patients with chronic renal failure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02280760
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  • 34
    Digitale Medien
    Digitale Medien
    The pharmacokinetics of tiopronin and its principal metabolite (2-mercaptopropionic acid) after oral administration to healthy volunteers (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 93-95 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Tiopronin ; 2-mercaptopropionic acid ; pharmacokinetics ; healthy volunteers
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the pharmacokinetics of tiopronin and its principal metabolite, 2-mercaptopropionic acid (2-MPA) in healthy volunteers after the oral administration of 500 mg (2 Acadione® tablets), followed by simultaneous assay of the two compounds in plasma over a period of 48 h using a new method (emission of fluorescence after HPLC and post-column derivatization by pyrene-maleimide). The absorption of tiopronin was slow (tmax between 4 and 6 h) and the plasma concentrations subsequently fell biexponentially. The principal metabolite 2-MPA appeared later in the plasma (tmax between 10 and 12 h after a lag-time of 3 h) then disappeared monoexponentially. About 15% of the tiopronin was metabolized to 2-MPA.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02280762
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  • 35
    Digitale Medien
    Digitale Medien
    Lack of effect of omeprazole, cimetidine, and ranitidine on the pharmacokinetics of ethanol in fasting male volunteers (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 209-212 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Ethanol ; gastric acid inhibition ; pharmacokinetics ; antisecretory drugs ; omeprazole ; ranitidine ; cimetidine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effects of three gastric antisecretory drugs on the pharmacokinetics of ethanol have been studied in a randomized crossover experiment. Male medical students (n=12) took ethanol 0.8 g/kg body weight at 08.00 h after an overnight fast. On seven successive days before drinking ethanol they were given omeprazole 20 mg, cimetidine 800 mg, ranitidine 300 mg, or no drug, with a period of at least 7 days between treatments. The peak blood ethanol concentration of 21.9 to 22.8 mmol·l−1 occurred at 64 to 70 min after the end of drinking. The rate of disappearance of ethanol from the blood ranged from 3.0 to 3.3 mmol·l−1·h−1 and the rate of removal from the whole body ranged from 8.0 to 8.5 g·h−1. The apparent volume of distribution of ethanol was almost the same for all four treatments: mean 0.68 l·kg−1, corresponding to a mean total body water of 441 (59% body weight). Mean areas under the concentration-time profiles of ethanol ranged from 83 to 87 mmol·l−1·h for the four treatments. It is concluded that omeprazole, cimetidine and ranitidine do not alter the kinetics of a moderate dose of ethanol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278486
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  • 36
    Digitale Medien
    Digitale Medien
    Absence of interaction between tenoxicam and warfarin (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 227-229 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Tenoxicam ; Warfarin ; drug interaction ; pharmacokinetics ; anticoagulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The influence of tenoxicam on plasma warfarin concentrations and on its anticoagulant effect has been studied in healthy volunteers. Tenoxicam did not alter the plasma warfarin concentration versus time profile. Treatment with it for 14 days had no effect on the average dose of warfarin required to maintain the prothrombin time within a specified range. The coumarin dose index, an indicator of warfarin sensitivity, remained unchanged during tenoxicam administration. The results demonstrate the lack of a clinically relevant effect of tenoxicam on warfarin-induced anticoagulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00278491
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  • 37
    Digitale Medien
    Digitale Medien
    The influence of hydrochlorothiazide on the pharmacokinetics of enalapril in elderly patients (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 173-177 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Enalapril ; Hydrochlorothiazide ; pharmacokinetics ; renal impairment ; old patients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary In a randomized, cross-over, single-dose study of 19 elderly hypertensive patients (aged 62–84 y, SBP 〉 160 mm Hg, DBP 〉 100 mm Hg, creatinine clearance 11–93 ml·min−1) we have studied the pharmacokinetics of the angiotensin converting enzyme (ACE) inhibitor enalapril after a single oral dose of either 10 mg enalapril or 10 mg enalapril + 25 mg hydrochlorothiazide. The pharmacokinetics of enalapril were unaffected by hydrochlorothiazide, but there was a significant reduction in renal clearance and a significant increase in AUC(0–24 h) of enalaprilat after hydrochlorothiazide, resulting in higher serum concentrations of the active drug. This was independent of the individual degree of renal impairment and might be due either to an initial reduction of GFR by hydrochlorothiazide or to interference with the tubular secretion of enalaprilat. The relationships between serum enalaprilat and serum ACE activity were similar after both treatments, both consistent with a value for Ki of enalaprilat of about 0.1 nmol·l−1. Thus, serum ACE activity was not affected by hydrochlorothiazide but completely reflected the pharmacokinetics of enalaprilat in both treatments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01740666
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  • 38
    Digitale Medien
    Digitale Medien
    Lack of pharmacodynamic and pharmacokinetic interactions of the antihistamine ebastine with ethanol in healthy subjects (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 179-184 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Ebastine ; Ethanol interaction ; carebastine ; psychomotor performance ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have given 12 healthy subjects the H1-antihistamine ebastine (20 mg) or placebo in a double-blind, crossover study for one week each. The subjects were tested for drug effects on Day 6 of each period, and for interactions of ebastine with ethanol (0.8 g·kg−1) on Day 7. On both days, the testing runs were done at baseline and at 2, 4, and 6 h after the drug. Performance was evaluated both objectively (digit symbol substitution, flicker fusion, Maddox wing, nystagmus, simulated driving, body balance) and subjectively (visual analogue scales) and with questionnaires. Venous blood samples were taken daily during maintenance and during each test run for assay of plasma carebastine. Blood ethanol concentrations were assayed with an Alcolmeter in the breath and directly in the blood. Plasma carebastine concentration reached a steady-state from Day 3 on; the mean concentrations in the morning were 92 µg·l−1 on Day 6 and 104 µg·l−1 on Day 7. The rise in plasma carebastine after an extra 20 mg of ebastine was accelerated but not increased by ethanol. Ebastine did not impair performance objectively or subjectively. It slightly improved body balance and reduced errors during simple tracking at 4 h. Blood ethanol concentrations peaked (mean 0.76 g·l−1) at 1.5 h after ethanol intake. Ethanol impaired performance in most objective tests and produced clumsiness, muzziness, and mental slowness, but little drowsiness. Ebastine neither modified the blood ethanol concentrations nor increased the effects of ethanol. We conclude that treatment with 20 mg ebastine once daily for one week provides steady concentrations of carebastine in plasma without impairment of skilled performance or important interactions with alcohol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01740667
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  • 39
    Digitale Medien
    Digitale Medien
    Lack of interaction ofβ-methyldigoxin with ranitidine in patients with chronic congestive heart failure (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 205-206 
    Details
    ISSN: 1432-1041
    Schlagwort(e): β-Methyldigoxin ; Ranitidine ; pharmacokinetics ; drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01740673
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  • 40
    Digitale Medien
    Digitale Medien
    The effect of haemodialysis on the pharmacokinetics of tenoxicam in patients with end-stage renal disease (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 197-199 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Tenoxicam ; pharmacokinetics ; haemodialysis ; end-stage renal disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the pharmacokinetics of tenoxicam after single and multiple oral doses of 20 mg in five patients (2 men and 3 women) with end-stage renal disease undergoing haemodialysis. After a single dose, tenoxicam had a half-life (t1/2) of 33 h, an apparent clearance (CL·f−1) of 4.3 ml·min−1, and an apparent volume of distribution (Vz·f−1) of 11.8 l. The maximum tenoxicam concentration (Cmax) was 4.3 mg·l−1 at a median tmax of 1.7 h. There were no significant differences between the values calculated from the pre- or post-dialyser port plasma samples. Tenoxicam plasma concentrations measured during once daily dosing before and after haemodialysis showed that tenoxicam does not accumulate. Our findings suggest that dosage adjustment may not be required in patients with end-stage renal disease on haemodialysis taking tenoxicam.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01740671
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  • 41
    Digitale Medien
    Digitale Medien
    Relationship between arterial and peripheral venous catecholamine plasma catecholamine concentrations during infusion of noradrenaline and adrenaline in healthy volunteers (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 245-249 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Noradrenaline ; Adrenaline ; catecholamines ; pharmacokinetics ; healthy volunteers ; IV infusion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Noradrenaline and adrenaline were infused IV at 5 different rates (0.01–0.2 μg · kg · min− for 30 min to volunteers. The plasma catecholamine concentrations were determined by HPLC and electro-chemical detection. At the highest infusion rate, the arterial and venous plasma concentrations of noradrenaline increased from 1.18 to 44.1 nmol · l−1and from 1.14 to 31.9 nmol · l−1, respectively, and of adrenaline from 0.29 to 23.9 nmol · l−1 and from 0.28 to 19.3 nmol · l−1 respectively. The peripheral venous plasma concentration of noradrenaline averaged 76% of the arterial concentration, and of adrenaline it was 73%. There was a linear relationship between the peripheral venous and arterial plasma noradrenaline and adrenaline concentrations at therapeutic doses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02333017
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  • 42
    Digitale Medien
    Digitale Medien
    Pharmacokinetic profile of a novel slow release preparation of molsidomine (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 273-276 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Molsidomine ; slow release ; pharmacokinetics ; in vitro/in vivo correlation ; pharmacokinetics ; healthy volunteers ; dissolution profile
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary A novel slow release preparation containing 24 mg molsidomine has been investigated in 6 healthy subjects. Individual concentration/time-profiles after the tablet showed two separate concentration peaks at 2.2 h and 15.0 h. The relative bioavailability of the slow release preparation in comparison to an aqueous solution of molsidomine was 0.67. The in vivo dissolution profile revealed either a progressive decrease in dissolution velocity caused by altered physico-chemical conditions in the ileum and the colon or a progressive reduction in the absorption constant. In all subjects deconvolution revealed a punctual increase in absorption about 15 h post-dose, coinciding with the second peak of the concentration/time-profile. Therapeutic plasma levels of molsidomine (〉 5 ng · ml−1 were not maintained over 24 h by this slow release formulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02333022
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  • 43
    Digitale Medien
    Digitale Medien
    Captopril does not interact with the pharmacodynamics and pharmacokinetics of digitoxin in healthy man (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 445-447 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Captopril ; Digitoxin ; impedance cardiography ; drug interaction ; healthy volunteers ; pharmacodynamics ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The chronic oral administration of 0.07 mg digitoxin o. d. for up to 58 days to 12 healthy volunteers caused a small drop in mean heart rate HR (95 % CI: −7.9 to −1.6 beats · min−1), in mean diastolic blood pressure (95 % CI: −8.3 to −0.4 mm Hg), shortening of the QTc-interval (95 % CI: −42 to −19 ms), shortening of the HR-corrected pre-ejection period PEPc (95 % CI: −16 to −1 ms) and electromechanical systole QS2c (95 % CI: −25 to −1 ms), and an increase in the impedance cardiographic Heather index (dZ/dtmax/RZ, 95 % CI: 0.3 to 4.3) relative to the baseline measurements before digitalisation. The concomitant administration of 25 mg oral captopril b. d. did not significantly alter these responses relative to the concomitant double-blind administration of placebo, nor did it alter the pharmacokinetic characteristics of plasma digitoxin at steady state. Thus, no relevant change in the pharmacokinetic and pharmacodynamic characteristics of chronically administered digitoxin were induced by concomitant treatment with captopril.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02220626
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  • 44
    Digitale Medien
    Digitale Medien
    Enantioselective pharmacodynamics and pharmacokinetics of chiral non-steroidal anti-inflammatory drugs (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 237-256 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Non-steroidal anti-inflammatory drugs ; Enantioselective ; Enantiomers ; pharmacodynamics ; pharmacokinetics ; stereoselective
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00266343
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  • 45
    Digitale Medien
    Digitale Medien
    Acute effects of drinking grapefruit juice on the pharmacokinetics and dynamics on felodipine — and its potential clinical relevance (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 313-317 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Dihydropyridine ; Felodipine ; availability ; flavonoids ; dietary interaction ; pharmacokinetics ; pharmacodynamics ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effect of drinking grapefruit juice on the acute pharmacokinetic and haemodynamic actions of the dihydropyridine calcium antagonist felodipine given as a 5 mg plain tablet has been studied in nine, healthy, middle-aged males. Compared to water, grapefruit juice caused an increase in Cmax from mean 6 to 16 nmol · l−1, and in the AUC from 23 to 65 nmol · h · l−1. The change in AUC corresponded to an increase in the systemic availability of felodipine from 15 to 45%, assuming no change in its clearance. This change was probably caused by inhibition of the oxidation of felodipine to the inactive dehydrofelodipine by flavonoids in grapefruit juice. The interaction with grapefruit juice is believed to be a class effect for the dihydropyridines, as oxidation of the dihydropyridine ring to the corresponding pyridine derivative is a major metabolic route for all these drugs. The higher plasma concentrations of felodipine taken with grapefruit juice resulted in a greater change in blood pressure measured in the morning 3 h after dosing (−9%) than did water (0%).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00266354
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  • 46
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of midazolam during continuous infusion in critically ill neonates (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 329-332 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Midazolam ; Fentanyl ; Neonates ; pharmacokinetics ; sedation drug interaction ; hypotension
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Midazolam is a water soluble benzodiazepine, with a short elimination half-life in adults and children. An IV bolus (0.2 mg·kg−1) immediately followed by continuous infusion of 0.06 mg·kg−1·h−1 was administered to 15 critically ill neonates at a gestational age of 32.8 weeks, who required sedation for mechanical ventilation. Heart rate and blood pressure were closely monitored. Hypotension occurred in 4 patients after the bolus dose or during the continuous infusion. Three of them had also been given fentanyl. Individual pharmacokinetic parameters were calculated: plasma clearance was 3.9 ml·min−1, elimination half-life was 12.0 h. Because of its short half-life compared to diazepam, midazolam may be used during the neonatal period to achieve rapid, brief sedation. However, it should be administered cautiously to neonates, particularly in premature infants, or if fentanyl is also given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00266357
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  • 47
    Digitale Medien
    Digitale Medien
    Theophylline steady state pharmacokinetics is not altered by omeprazole (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 343-345 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Omeprazole ; Theophylline ; pharmacokinetics ; drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The effect of omeprazole treatment on theophylline pharmacokinetics was studied in eight, non-smoking healthy male volunteers during repeated administration of a slow release formulation of theophylline. In a randomized double-blind cross-over study, the subjects received theophylline 5 mg·kg−1 per day with omeprazole 20 mg per day or identical placebo during two periods, each of 7 days, separated by a washout period of 7 days. The oral clearance of theophylline remained unchanged whether it was administered alone or with omeprazole (54.2 ml·min−1). The average urinary excretion of theophylline and its metabolites, 1,3 dimethyluric acid (1,3-DMU), 3-methylxanthine (3-MX), 1-methyluric acid (1-MU) amounted to 9%, 32%, 12% and 22% of the administered dose, respectively, and no significant change occured during concomitant treatment with omeprazole. Thus, the formation and clearance of the metabolites was not altered by omeprazole. Consequently, omeprazole in the recommended dose of 20 mg daily can safely be administered to patients on theophylline therapy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00266361
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  • 48
    Digitale Medien
    Digitale Medien
    Disposition kinetics and concentration-effect relationship of metipranolol in patients with cirrhosis and healthy subjects (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 337-340 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Metipranolol ; Liver cirrhosis ; pharmacokinetics ; pharmacodynamics ; beta-adrenoreceptor blockade
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The disposition kinetics and heart rate reducing effect of deacetylmetipranolol (DMP), the active form of the β-adrenoreceptor blocking agent metipranolol (MP), administered as a single 40 mg oral dose have been compared in 6 patients with cirrhosis and 6 healthy volunteers. The mean maximal DMP concentration was significantly higher and the time to reach the peak level shorter in the patients compared to the healthy subjects. There was also a significantly higher AUC of DMP, a shorter half-life of the rapid phase of the decline in DMP concentrations, a smaller central compartment and lower apparent DMP clearance in patients. A correlation with the albumin level was observed in cirrhotics for individual values of apparent DMP clearance (r=0.92) and AUC (r=-0.89). The maximal reduction in heart rate was recorded in patients at plasma DMP levels which were already significantly lower than the peak levels. Median inhibitory concentrations (IC50) and maximum possible heart rate reductions (Δ HRmax), obtained by fitting individual plots of the plasma DMP concentration-effect relationship to the inhibitory Emax model in the postdistributional phase of DMP disposition were significantly higher in cirrhotics than in healthy subjects. It is conjectured that down-regulation of adrenoreceptors due to chronic sympathetic activation in hepatic cirrhosis contributes to decreased sensitivity to the reduction in heart rate following a single dose of the beta-blocker.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00266359
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  • 49
    Digitale Medien
    Digitale Medien
    Influence of food on serum ambenonium concentration in patients with myasthenia gravis (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 371-374 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Ambenonium chloride ; Myasthenia gravis ; dietary effect ; serum concentration ; adverse effects ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Influence of food on the serum concentration and kinetics ambenonium chloride (AMBC) has been examined in thirteen patients with myasthenia gravis (MG). Mean serum concentrations and Cmax during fasting were higher than those in the non-fasting state. The AUC (0–3 h) was also about four-times larger. The drug effects versus the serum concentration were observed to be anti-clockwise or clockwise. The effective range of the Cmax varied between patients. The unexpected increase in Cmax led to adverse muscarinic actions of AMBC, when the condition was changed from the non-fasting to the fasting state. It is recommended that the dose be changed during non-fasting treatment when adjusting the optimum regimen for patients myasthenia gravis. Patients must be advised to keep to the dosing and dietary schedule in order to avoid unexpected adverse actions to AMBC.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280120
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  • 50
    Digitale Medien
    Digitale Medien
    Stereoselective pharmacokinetics of oral nitrendipine in elderly hypertensive patients with normal and impaired renal function (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 423-427 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Nitrendipine ; enantiomers ; stereoselectivity ; Renal failure ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of the enantiomers of nitrendipine has been studied in seven elderly patients with chronic renal failure (CRF) and in six control subjects (mean creatinine clearance 30 and 97 ml·min−1 respectively). Racemic nitrendipine 20 mg was given once daily for seven days and the pharmacokinetics of the enantiomers over the last dosage interval were determined using a stereospecific assay. In both groups nitrendipine exhibited stereoselective pharmacokinetics (AUC, Cmax), but the half-lives of the enantiomers did not differ in individual subjects. As an index of stereoselectivity, the mean S/R ratio of AUCs in control subjects (2.07) was not significantly different from the ratio in patients with CRF (2.68). The mean AUCs of (S)- and (R)-nitrendipine during the last dosage interval were increased in CRF by 132% and 85%, respectively. The observed doubling of the half-lives and the increases in Cmax did not reach significance because of the large variability in each group. Thus, the pharmacokinetics of oral nitrendipine is altered in CRF, but there was no change in the stereoselectivity of its pharmacokinetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280129
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  • 51
    Digitale Medien
    Digitale Medien
    Chloroquine levels in blood during chronic treatment of patients with rheumatoid arthritis (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 429-433 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Chloroquine ; Rheumatoid arthritis ; desethylchloroquine ; bisdesethylchloroquine ; blood levels ; toxicity ; therapeutic activity ; dose-effect relationship ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Blood levels of racemic chloroquine and its main metabolites desethylchloroquine and bisdesethylchloroquine were measured in 29 patients treated chronically for rheumatoid arthritis. In six patients, the concentrations were followed during a one day dosage interval. There was considerable intersubject variability in the steady state blood concentrations of chloroquine (range 36.6 to 3895 ng·ml−1) and its two main biotransformation products; the latter represented, respectively, 47.7% and 12.9% of the concentration of chloroquine. This finding shows the need for further studies in view of the known toxic effects of chloroquine and the inevitable accumulation due to the exceptionally long residence time of the compound and its metabolites. The main requirement, which has not yet been met, for adding chloroquine to the list of drugs for which therapeutic drug monitoring is useful, is the lack of information about its mechanism of action, and consequently the dose-effect relationships of its therapeutic and toxic actions. Regular ophthalmic examination, in particular, is strongly recommended. The relatively high concentrations of desethylchloroquine and bisdesethylchloroquine found during chronic treatment show the need for more information about the therapeutic value and adverse effects of the metabolites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00280130
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  • 52
    Digitale Medien
    Digitale Medien
    Elevated plasma nilvadipine concentration after single and chronic oral administration to patients with chronic liver disease (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 475-479 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Calcium channel blocker ; Nilvadipine ; blood pressure ; liver disease ; pharmacokinetics ; pharmacodynamics ; cirrhosis ; hepatitis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Fourteen normotensive patients with liver disease (6 with cirrhosis and 8 with chronic hepatitis) and 7 healthy volunteers were given a single oral dose of nilvadipine 2 mg. In addition, nilvadipine 4 mg was administered orally twice daily for several months to 6 hypertensive patients with mild liver dysfunction and 18 hypertensives with normal liver function. A significant increase in plasma nilvadipine was found in the patients with cirrhosis as compared both to the normal and chronic hepatitis subjects; the time to peak concentration was similar among the three groups. The peak plasma nilvadipine concentration was closely correlated both with the serum albumin level and the retention of indocyanine green. Changes in blood pressure, pulse rate and various vasoactive hormones following a single oral dose of nilvadipine did not differ between the groups. Thus, an increase in plasma nilvadipine relative to the level in normal subjects was demonstrated in patients with cirrhosis following a single oral dose, as well as in patients with slight liver dysfunction following long-term oral administration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314853
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  • 53
    Digitale Medien
    Digitale Medien
    Digoxin-interactions in man: Spironolactone reduces renal but not biliary digoxin clearance (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 481-485 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Digoxin ; Spironolactone ; drug interaction ; biliary clearance ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The possibility of an inhibitory effect of spironolactone on the biliary clearance of digoxin has been investigated in 6 healthy subjects. Plasma clearance and the renal and biliary clearance of digoxin were determined twice at steady state (digoxin 0.5 to 1 mg·d−1 p.o. for 6 days), alone or in combination with spironolactone 200 mg daily, after an intravenous dose of digoxin (0.7 × oral dose) on Day 7. Plasma and urine were collected for 48 h. Biliary clearance of digoxin was determined on Day 8 by a duodenal perfusion technique. During spironolactone treatment plasma digoxin clearance tended to be lower (255 vs 224 ml/min; P=0.057) and renal clearance significantly lower (166 vs 144 ml/min), while the biliary clearance of digoxin remained unchanged (106 vs 103 ml/min). Thus, spironolactone reduced the renal clearance of digoxin by an average of 13%, without affecting its biliary clearance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314854
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  • 54
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of vinorelbine in man (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 545-547 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Vinorelbine ; anti-neoplastic agents ; vinca alkaloids ; pharmacokinetics ; lung neoplasms ; HPLC ; assay method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of vinorelbine has been investigated by a new HPLC method in 8 cancer patients receiving 8 weekly doses (30 mg·m−2) administered by brief infusion (15 min). The plasma concentration-time curves showed a tri-exponential decay with a long terminal half-life (44.7 h) and a high volume of distribution (Vz=75.61·kg−1). The concentrations after the 8th infusion were significantly lower than after the 1st infusion, but without significant modification of CL (1.28 l·h−1·kg−1) or AUC (0.80 mg·l−1·h). The pharmacokinetic parameters exhibited wide inter-individual variations. The results are consistent with those of previous RIA studies, although the HPLC method appears to be more specific and more precise.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00314866
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  • 55
    Digitale Medien
    Digitale Medien
    The postoperative pharmacokinetics of codeine (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 663-666 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Morphine ; Codeine ; drug metabolism ; pharmacokinetics ; systemic availability ; individual variability ; post-operative state
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The metabolism and systemic availability of codeine have been studied in 12 patients after cholecystectomy. They were given 20 mg codeine as an IV bolus dose on the first day after surgery and 50 mg codeine as a single oral on the fourth day after surgery. Codeine had a medium to high extraction ratio and a total plasma clearance of 10.8 (4.3) ml·min−1·kg−1. The clearance varied fourfold between subjects. All the patients were extensive metabolizers with regard to the debrisoquine/sparteine polymorphism, as tested using dextromethorphan as the probe drug. Nevertheless, the formation of morphine from codeine was very small and plasma morphine concentrations were below the detection limit of 3.3 nmol·1−1 (1 ng·ml−1). As a corollary, the morphine/codeine ratio in the the concentration-time curves was less than 3% in all the patients. The systemic availability of codeine varied extensively between subjects (range 12–84%). This might partly explain differences in the dose of codeine required as an analgesic.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265933
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  • 56
    Digitale Medien
    Digitale Medien
    The pharmacokinetics of nifurtimox in chronic renal failure (1992)
    Springer
    European journal of clinical pharmacology 42 (1992), S. 671-673 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Nifurtimox ; Changas' disease ; renal failure ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of nifurtimox, a drug used in the treatment of Trypanosoma cruzi infections, has been studied in seven patients with chronic renal failure undergoing haemodialysis, and in seven healthy subjects. Each subject took nifurtimox 15 mg·kg−1 orally and blood samples were obtained for 10 h after administration. Nifurtimox in serum was analyzed by HPLC. The patients with chronic renal failure had a higher Cmax than the control subjects due to a change in systemic availability. An alternative explanation would be that both the distribution volume and the clearance had changed. The mean half-life in the patients with chronic renal failure was similar to that in the healthy subjects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00265935
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  • 57
    Digitale Medien
    Digitale Medien
    Lack of pharmacokinetic interaction between moxonidine and hydrochlorothiazide (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 209-210 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Moxonidine ; Hydrochlorothiazide ; pharmacokinetics ; drug interaction ; steady-state ; healthy volunteers ; adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01740675
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  • 58
    Digitale Medien
    Digitale Medien
    Altered pharmacokinetics of lignocaine after epidural injection in Type II diabetics (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 269-271 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Lignocaine ; diabetes mellitus ; pharmacokinetics ; epidural anaesthesia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The pharmacokinetics of lignocaine has been compared after epidural anaesthesia in diabetics and nondiabetic patients. Epidural lignocaine 8 mg · kg−1 was given to 8 well controlled Type II diabetic and 8 nondiabetic patients and the plasma drug concentration in serial blood samples were measured by HPLC. The plasma level of lignocaine was lower in diabetics compared to non-diabetics. The peak level was attained at 20 min in both groups. The clearance of the drug was significantly higher, (39,9 vs 16,7 ml · min− · kg−) associated with a decreased elimination half-life and mean residence time. The study suggests that the rate of absorption of lignocaine is not altered after epidural administration and that its hepatic metabolism is increased in diabetics compared to non-diabetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02333021
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  • 59
    Digitale Medien
    Digitale Medien
    Pharmacokinetic estimations from microdialysis data (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 289-294 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Microdialysis ; Drug concentration ; parameter estimation ; pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary Microdialysis has recently been adapted for sampling the extracellular fluid of various organs in order to measure drug concentrations, and the first clinical application has been published. My aim here is to provide simple rules about how to analyse pharmacokinetic data from such studies. The plotting of data on a time scale and the estimation of C (0) and slopes is not a trivial problem when multicompartmental models are assumed or sampling intervals are unequal. I have developed formulae and algorithms to solve the problem. A simple rule of thumb is given, suggesting when these formulae need to be applied. It is shown that the calculations of half-life and slopes is similar to standard methods for equal sample intervals and that calculation of AUC and clearance may be even more accurate for microdialysis data than for ordinary blood sampling, because of the time-integral character of the dialysis method. I have dealt with both zero-order and first-order kinetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02333025
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  • 60
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of pirmenol in young and elderly subjects (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 437-439 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Pirmenol ; pharmacokinetics ; elderly subjects ; age effect ; adverse effect
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary The steady state pharmacokinetics of pirmenol was compared in twelve healthy young (aged 18 to 45 y) and 11 elderly subjects (over 65 y) subjects given pirmenol HCl 100 mg every 12 h for a total of 14 doses. In addition, the single-dose pharmacokinetics of pirmenol was determined following a 100 mg oral dose in the young subject group for comparison with the results of repeated administration. In the young subjects, the mean single-dose and steady-state CLR of pirmenol were similar; however, Ae was 29 % higher and CL/f was 22 % lower at steady state than after the single dose. Steady-state (fourteenth dose) Cmin, Cmax, tmax, λz, Ae, CL/f, CLR and V values were similar in the young and elderly subjects. Based on pharmacokinetic considerations, the dosage of pirmenol is unlikely to differ in young and elderly subjects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02220624
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  • 61
    Digitale Medien
    Digitale Medien
    The effect of a low dose of quinidine on the disposition of flecainide in healthy volunteers (1992)
    Springer
    European journal of clinical pharmacology 43 (1992), S. 441-443 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Flecainide ; quinidine ; pharmacokinetics ; metabolism inhibition ; drug interaction ; renal transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary We have studied the effects of quinidine on ECG intervals and on the pharmacokinetics of flecainide and its two metabolites in 6 healthy men in an open randomized crossover study. Flecainide acetate (150 mg) was given as a constant rate i. v. infusion over 30 min. Quinidine (50 mg orally), given the previous evening, did not change the volume of distribution of flecainide (7.9 vs 7.41·kg−1), but significantly increased its half-life (8.8 vs 10.7 h). This was attributable to a reduction in total clearance (10.6 vs 8.1 ml·min−1·kg−1), most of it being accounted for by a reduction in non-renal clearance (7.2 vs 5.2 ml·min−1·kg−1). The excretion of the metabolites of flecainide over 48 h was significantly reduced. These findings suggest that quinidine inhibits the first step of flecainide metabolism, although it may also reduce its renal clearance, but to a lesser extent (3.5 vs 2.9 ml·min−1·kg−1). The effects of flecainide on ECG intervals were not altered by quinidine. Thus, quinidine tends to shift extensive metabolizer status for flecainide towards poor metabolizer status and may also alter its renal excretion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02220625
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  • 62
    Digitale Medien
    Digitale Medien
    High SO2 resistance ofClethra barbinervis established in a smoke-polluted area of Ashio, Tochigi Prefecture, Japan (1992)
    Springer
    Ecological research 7 (1992), S. 363-370 
    Details
    ISSN: 1440-1703
    Schlagwort(e): Clethra barbinervis ; interspecific difference ; intraspecific variation ; photosynthesis ; SO2 resistance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of SO2 on the photosynthesis ofClethra barbinervis collected from a smoke-polluted area near the Ashio copper smelter in Tochigi Prefecture was compared withC. barbinervis collected from a nonpolluted district in Tsukuba, Ibaraki Prefecture andQuercus mongolica var.grosseserrata grown in a nonpolluted field in Nagano Prefecture. The plants were exposed to 0.5–1.5 p.p.m. SO2 for 90 min (short-term) and to 0.3 p.p.m. SO2 for 31–39 days (long-term). TheClethra plants from both sites had a lower intrinsic stomatal conductance and photosynthetic rate thanQuercus plants. Short-and long-term fumigation caused stomatal closure inQuercus plants, but had little effect on the stomatal conductance ofClethra plants. Under short-term fumigation, nonstomatal photosynthetic inhibition per unit of absorbed SO2 was smallest inClethra plants from Ashio. Long-term fumigation caused photosynthetic decline and visible foliar injury toQuercus plants, but had no effect onClethra plants from Ashio. Consequently,Clethra plants from Ashio had a higher photosynthetic rate thanQuercus plants after long-term fumigation. These results suggest thatC. barbinervis populations in the smoke-polluted area of Ashio had evolved high SO2 resistance connected with SO2 detoxification ability in mesophyll cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02347103
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  • 63
    Digitale Medien
    Digitale Medien
    Sequence of the fourth and fifth Photosystem II Type I chlorophyll a/b-binding protein genes of Arabidopsis thaliana and evidence for the presence of a full complement of the extended CAB gene family (1992)
    Springer
    Plant molecular biology 19 (1992), S. 725-733 
    Details
    ISSN: 1573-5028
    Schlagwort(e): gene duplication ; photosynthesis ; RFLP ; Southern blots
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A second locus (Lhb1B) encoding Photosystem II Type I chlorophyll a/b-binding (CAB) polypeptides was identified in Arabidopsis thaliana. This locus carries two genes in an inverted orientation. The predicted sequences of the polypeptides encoded by these two genes show substantial divergence in their amino termini relative to each other and to the proteins encoded by the three Lhb1 CAB genes previously characterized [10], but little divergence within the predicted primary structure of the mature protein. DNA probes derived from seven additional types of tomato CAB genes, encoding chlorophyll a/b-binding polypeptides of several antenna systems of the photosynthetic apparatus, were tested against A. thaliana. Each of these hybridized in Southern blots to unique DNA fragment(s), demonstrating the existence of each of these different types of CAB genes in the genome of A. thaliana. The number of genes encoding each CAB type in A. thaliana was estimated to be similar to that of tomato.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00027069
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  • 64
    Digitale Medien
    Digitale Medien
    Cloning and sequencing of the petBD operon from the cyanobacterium Synechococcus sp. PCC 7002 (1992)
    Springer
    Plant molecular biology 20 (1992), S. 481-491 
    Details
    ISSN: 1573-5028
    Schlagwort(e): photosynthesis ; cytochrome b 6 ; gene regulation ; genome mapping
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The genes encoding the photosynthetic cytochrome b 6 (petB) and subunit 4 (petD) have been cloned and sequenced from the unicellular, photoheterotrophic, transformable cyanobacterium Synechococcus sp. PCC 7002, formerly designated Agmenellum quadruplicatum. The gene arrangement was found to be similar to that reported in the cyanobacterium Nostoc PCC 7906. The DNA and derived protein sequences were compared to chloroplast and the other cyanobacterial sequences. By pulsed-field electrophoresis, the petBD operon and the petCA operon, encoding the Rieske iron-sulfur protein and cytochrome f, were found to be located on separate, unlinked,Not I-digested DNA fragments. ThepetBD operon was found on the third largest Not I fragment (NC-325) while the petCA operon was found on the second largest Not I fragment (NB-370). These results suggest the two operons are not in proximity. The 1.35 kb transcript was shown to be light-regulated. Transcripts from cells grown under constant illumination showed a decrease in petB transcript levels to undetectable levels within 2 h after the cells were placed in the dark. Upon reillumination, transcript levels rose to three-fold over that seen initially under constant illumination.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00040607
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  • 65
    Digitale Medien
    Digitale Medien
    Chlorophyll a/b-binding protein genes are differentially expressed during soybean development (1992)
    Springer
    Plant molecular biology 19 (1992), S. 217-230 
    Details
    ISSN: 1573-5028
    Schlagwort(e): chlorophyll a/b-binding protein genes ; Glycine ; LHCP II ; photosynthesis ; soybean ; ribulose-1,5-bisphosphate carboxylase genes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The levels of chlorophyll a/b-binding protein (Cab) gene polysomal poly(A)+ mRNA were quantitated throughout the development of Glycine max L. Cab mRNAs were abundant in young expanding leaves, representing 6.1% of the leaf mRNA population. Lower Cab mRNA levels were present in embryos, stems, and cotyledons of developing seedlings; the lowest levels were found in roots where they accounted for 0.04% of the polysomal poly(A)+ mRNA of this organ. To determine the contribution of different members of the Cab gene family to the Cab mRNA populations, a quantitative S1 nuclease reconstruction assay was developed. Cab3, Cab4, and Cab5 mRNAs were detected in all stages examined during soybean development but their levels underwent differential changes. Cab3 encodes the most abundant Cab mRNA in young leaves, developing embryos, and in Stage VII cotyledons from the developing soybean seedling. The levels of Cab mRNAs were compared to the levels of ribulose-1,5-bisphosphate carboxylase small subunit gene mRNA and differences in their patterns of accumulation were noted. Collectively these data indicate that during soybean embryogenesis developmental control mechanisms supersede light-regulatory signals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00027343
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  • 66
    Digitale Medien
    Digitale Medien
    Dimerization constant and single-channel conductance of Gramicidin in thylakoid membranes (1992)
    Springer
    The journal of membrane biology 126 (1992), S. 265-275 
    Details
    ISSN: 1432-1424
    Schlagwort(e): photosynthesis ; thylakoids ; electrochromism ; gramicidin ; conductance ; dimerization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Summary The effect of the pore-forming antibiotic gramicidin on pure lipid membranes is well characterized. We studied its action in protein-rich thylakoid membranes that contain less than 25% (wt/wt) acyl lipids. A transmembrane voltage was induced by flashing light, and its decay was measured and interpreted to yield the distribution of gramicidin over thylakoids, its dimerization constant and its single-channel conductance in this membrane. The distribution of gramicidin over the ensemble of thylakoids was immediately homogeneous when the antibiotic was added under stirring, while it became homogeneous only after 20 min in a stirred suspension that was initially heterogeneous. The dimerization constant, 5×1014 cm2/mol, was about 10 times larger than in pure lipid membranes. This was attributed to the upconcentration of gramicidin in the small fractional area of protein free lipid bilayer and further by a preference of gramicidin for stacked portions of the membrane. The latter bears important consequences with regard to bioenergetic studies with this ionophore. As gramicidin was largely dimerized from a concentration of 1 nm (in the suspension) on, the membrane's conductance then increased linearly as a function of added gramicidin. When the negative surface potential at the thylakoid membrane was screened, the conductance of a single gramicidin dimer agreed well with figures reported for bilayers from neutral lipid (about 0.5 pS at 10 mm NaCl). The modulation of the conductance by the surface potential in spinach versus pea thylakoids and between different preparations is discussed in detail.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00232323
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  • 67
    Digitale Medien
    Digitale Medien
    Effects of drought on chlorophyll fluorescence in potato (Solanum tuberosum L.). II. Relations between plant growth and measurements of fluorescence (1992)
    Springer
    Potato research 35 (1992), S. 35-40 
    Details
    ISSN: 1871-4528
    Schlagwort(e): water-stress ; photosynthesis ; yield
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Relations between measurements of the slow kinetics of chlorophyll fluorescence and growth and yield were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Drought reduced total dry matter production and yields and increased tuber dry matter concentration. Drought increased harvest index in cv. Spunta, but decreased it in cv. Pentland Crown. Total dry matter production was correlated with each of constant fluorescence, variable fluorescence and the half life of the decay in variable fluorescence. These correlations were determined largely by the effect of treatment, and did not discriminate effectively between genotypes within a treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02357720
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  • 68
    Digitale Medien
    Digitale Medien
    Effects of drought on chlorophyll fluorescence in potato (Solanum tuberosum L.). I. Plant water status and the kinetics of chlorophyll fluorescence (1992)
    Springer
    Potato research 35 (1992), S. 25-34 
    Details
    ISSN: 1871-4528
    Schlagwort(e): water-stress ; photosynthesis ; leaf water potential
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary The slow kinetics of chlorophyll fluorescence were examined in seven potato genotypes grown either fully irrigated or droughted from the time of plant emergence. Constant and variable fluorescence (F o andF v respectively) declined with time in plants from both irrigated and droughted treatments, but the decline was greater in droughted than irrigated plants. However, the yield of variable fluorescence (F v/(F o+F v)) was unaffected by the drought treatment. The main effect of drought was upon the quenching of variable fluorescence. Both the half life of the decay of variable fluorescence (q1/2) and the secondary maximum (M) were significantly greater in the droughted plants than in those from the irrigated treatment. Significant differences between genotypes were found forF v/(F o+F v),M andq 1/2. Genotype-by-treatment interactions were non-significant for all the variables examined. Changes in chlorophyll fluorescence transients were not closely related to changes in leaf water potential.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02357719
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  • 69
    Digitale Medien
    Digitale Medien
    Photosynthetic characteristics of Dunaliella salina (Chlorophyceae, Dunaliellales) in relation to β-carotene content (1992)
    Springer
    Journal of applied phycology 4 (1992), S. 11-15 
    Details
    ISSN: 1573-5176
    Schlagwort(e): adaptation ; β-carotene ; Dunaliella salina ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic characteristics of Dunaliella salina with high (red form) and low β-carotene (green form) concentrations were studied. D. salina growing in brine saltworks exhibited a high level of β-carotene (15 pg cell−1). The rate of oxygen evolution as a function of irradiance was higher in the red than in the green form (on chlorophyll basis). Photosynthetic inhibition of the green form was observed above 500 µmol m−2 s−1. The red form appeared more resistant to high irradiance and no inhibition in O2 evolution was observed up 2000 µmol m−2 s−1. However, when these results are expressed on a cell number basis the rate of oxygen evolution was significantly higher in the green form. Carbonic anhydrase (CA) activity (total, soluble, membrane bound) was found in red and green forms. CA was higher in the red form on a chlorophyll basis, but lower if expressed on a protein basis. The light dependent rate of oxygen evolution and photoinhibition depends on the concentration of β-carotene in D. salina cells.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00003955
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  • 70
    Digitale Medien
    Digitale Medien
    Performance of a flat plate, air-lift reactor for the growth of high biomass algal cultures (1992)
    Springer
    Journal of applied phycology 4 (1992), S. 1-9 
    Details
    ISSN: 1573-5176
    Schlagwort(e): photobioreactor ; flat plate air-lift reactor ; Chlorella ; Synechococcus ; hydraulic characteristics ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A flat plate, multi-pass air lift reactor (FPALR) for the culture of photosynthetic organisms was constructed from twin wall acrylic sheet and its performance characterised. When operated at an air input of 2.01 min−1 the multi-pass system had a Reynolds number of 5200 indicating fully turbulent flow. Chlorella vulgaris 211/11c was found to have a stationary phase biomass of 1.48 g 1−1 when grown in the flat plate air lift reactor (FPALR) at 100 µmol m−2s−1 compared to 1.11 g 1−1 when cultured in the continually stirred tank reactor (CSTR) at the same PFD (photon flux density). The same organism cultured at 200 µmol m−2s−1 achieved a stationary phase biomass of 1.71 g 1−1 in the FPALR. In contrast, Scenedesmus sp. produced a stationary phase biomass of 2.27 g1−1 and 1.27 g1−1, when cultured at 100 µmol m−2s−1 in the FPALR and the CSTR respectively. The growth rates of both organisms were also higher in the PFALR.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00003954
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  • 71
    Digitale Medien
    Digitale Medien
    Pharmacokinetics and cytotoxicity of B.3839, a molecular combination of 5-fluorouracil and N-(2-chloroethyl)-N-nitrosourea, in a mouse model (1992)
    Springer
    Investigational new drugs 10 (1992), S. 149-158 
    Details
    ISSN: 1573-0646
    Schlagwort(e): pharmacokinetics ; cytotoxicity ; molecular combination ; fluorouracil ; nitrosourea
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Summary B.3839 is the prototype compound in a series of novel molecular combinations of chloroethylnitrosoureas and 5-fluorouracil(5-FU) and has been tested against MAC tumours in mice. Previous studies have shown it is moderately active against MAC15A and highly active against MAC13 though this activity is dependent on route of administration. The aim of this study was to determine whether bioavailability could explain this difference in anti-tumour activity. Plasma levels of B.3839 and 5-FU after i.p. and oral administration were measured using HPLC. Non tumour-bearing and MAC26 bearing mice gave almost identical plasma profiles after i.p. administration with the Cmax being 29.8 and 30.4μ gml−1 and t1/2 16 and 15 min. The AUCs were 15.3 and 13.9μg h ml−1 suggesting tumour load had no influence over plasma levels. Oral administration gave a much lower Cmax of 8.0μg ml−1 but an AUC of 15.2μg h ml−1 due to a longer terminal t1/2 (94 min) giving 99% bioavailability. Levels of 5-FU release from B.3839 by either route were considered too small to influence anti-tumour activity. Cytotoxicity assaysin vitro against the MAC lines gave IC70 values of 5.3, 13.8 and 8.6μg ml−1 for MAC 26,13 and 15A respectively after a one hour exposure. Bone marrow toxicity was shown to be less severe than that of TCNU which is currently in clinical trials. The results show bioavailability alone is not enough to explain tumour response. There appears to be a need for a threshold concentration (C) to be maintained for a period of time (t).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00877239
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  • 72
    Digitale Medien
    Digitale Medien
    Physiological pharmacokinetic parameters for cis-dichlorodiammineplatinum(II) (DDP) in the mouse (1992)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 20 (1992), S. 95-99 
    Details
    ISSN: 1573-8744
    Schlagwort(e): pharmacokinetics ; physiological model ; cisplatin ; DDP ; cis-dichlorodiammineplatinum(II)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01143187
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  • 73
    Digitale Medien
    Digitale Medien
    Evaluation of dose-related pharmacokinetics and pharmacodynamics of prednisolone in man (1992)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 20 (1992), S. 567-589 
    Details
    ISSN: 1573-8744
    Schlagwort(e): prednisolone ; pharmacokinetics ; pharmacodynamics ; corticosteroids ; protein binding
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The pharmacokinetics and pharmacodynamics of prednisolone were evaluated in normal male volunteers. Seven subjects completed 3 phases: 16.4−and 49.2−mg iv prednisolone, and a phase with no drug to assess baseline responses. Plasma concentrations of prednisolone and urine concentrations of prednisolone and 5 metabolites were assayed by HPLC. Protein binding of prednisolone was measured by ultrafiltration. The polyexponential disposition of free and total plasma prednisolone were evaluated and apparent parameters were compared between doses. Suppression of plasma cortisol and alterations in blood basophil and helper-T cell trafficking were used as pharmacodynamic indices. Pharmacodynamic models were used to relate total or free plasma prednisolone concentrations to each of these effects generating response parameters and IC50 (50% inhibitory) concentrations common to both doses. The pharmacokinetics of total drug were comparable to previous findings with CLand Vss increasing with dose. Free prednisolone exhibited slight capacitylimited elimination and distribution as CLand Vss decreased with the larger dose. Pharmacodynamic models jointly fitting all three phases characterized the suppression/trafficking phenomena equally well with use of total or free drug concentrations. In each case the models provided realistic values of parameters relating to steroid sensitivity-in particular IC50-and to the underlying physiology of the affected systems. This study comprehensively elucidates the complexities of prednisolone pharmacokinetics and demonstrates how plasma concentration-time profiles of total or free prednisolone can be utilized for evaluation of prednisolone pharmacodynamics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01064420
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  • 74
    Digitale Medien
    Digitale Medien
    Algorithms to rapidly achieve and maintain stable drug concentrations at the site of drug effect with a computer-controlled infusion pump (1992)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 20 (1992), S. 147-169 
    Details
    ISSN: 1573-8744
    Schlagwort(e): computers ; pharmacokinetics ; pharmacodynamics ; infusions ; drug delivery ; computer driven ; effect site
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Computer-controlled infusion pumps incorporating an internal model of drug pharmacokinetics can rapidly achieve and maintain constant drug concentrations in the plasma. Although these pumps offer more accurate titration of intravenous drugs than is possible with simple boluses or constant rate infusions, the choice of the plasma as the target site is arbitrary. The plasma is not the site of drug effect for most drugs. This manuscript describes two algorithms for calculation of the infusion rates necessary for a computer-controlled infusion pump to rapidly achieve, and then maintain, the desired target concentration at the site of drug effect rather than in the plasma.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01070999
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  • 75
    Digitale Medien
    Digitale Medien
    Application of semilinear canonical correlation to the measurement of opioid drug effect (1992)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 20 (1992), S. 611-635 
    Details
    ISSN: 1573-8744
    Schlagwort(e): pharmacokinetics ; pharmacodynamics ; plasma concentration-effect relation-ship ; anesthesia ; analgesic ; narcotic ; opioids ; alfentanil ; brain ; electroencephalograph ; spectral edge ; semilinear canonical correlation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract To examine the relationship between the electroencephalograph (EEG) and plasma opioid concentration, one would like to collapse the high-dimensional EEG signal into a univariate quantity. Such a simplification of the EEG is desirable because a univariate quantity can be modeled using standard nonlinear regression techniques, and because most of the information in the EEG is redundant or unrelated to drug concentration. In previous studies of the EEG response to opioids, the manner in which a univariate component was extracted from the EEG was ad hoc.In this paper, this extraction was performed optimally using a new statistical technique, semilinear canonical correlation. Data from 15 patients who received an intravenous infusion of the semisynthetic opioid alfentanil were analyzed. The components of the EEG that were nearly maximally correlated with plasma drug concentration were found, based on a standard pharmacokinetic-pharmacodynamic model. Two new EEG components were produced from the powers in the frequency spectrum of the EEG: a weighted sum of the logarithms of the powers, and a weighted sum of the powers expressed as percentages of the total power. These components both had a median R2 of 0.84, compared to median R2sranging from 0.37 to 0.83 for five commonly used ad hocEEG components. The new components also had less variability in R2 between subjects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01064422
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  • 76
    Digitale Medien
    Digitale Medien
    Building population pharmacokineticpharmacodynamic models. I. Models for covariate effects (1992)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 20 (1992), S. 511-528 
    Details
    ISSN: 1573-8744
    Schlagwort(e): pharmacokinetics ; population analysis ; model building ; generalized additive models ; NONMEM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract One major task in clinical pharmacology is to determine the pharmacokinetic-pharmacodynamic (PK-PD) parameters of a drug in a patient population. NONMEM is a program commonly used to build population PK-PD models, that is, models that characterize the relationship between a patient's PK-PD parameters and other patient specific covariates such as the patient's (patho)physiological condition, concomitant drug therapy, etc. This paper extends a previously described approach to efficiently find the relationships between the PK-PD parameters and covariates. In a first step, individual estimates of the PK-PD parameters are obtained as empirical Bayes estimates, based on a prior NONMEM fit using no covariates. In a second step, the individual PK-PD parameter estimates are regressed on the covariates using a generalized additive model. In a third and final step, NONMEM is used to optimize and finalize the population model. Four real-data examples are used to demonstrate the effectiveness of the approach. The examples show that the generalized additive model for the individual parameter estimates is a good initial guess for the NONMEM population model. In all four examples, the approach successfully selects the most important covariates and their functional representation. The great advantage of this approach is speed. The time required to derive a population model is markedly reduced because the number of necessary NONMEM runs is reduced. Furthermore, the approach provides a nice graphical representation of the relationships between the PK-PD parameters and covariates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01061469
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  • 77
    Digitale Medien
    Digitale Medien
    A physiologically based pharmacokinetic model for nicotine and cotinine in man (1992)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 20 (1992), S. 591-609 
    Details
    ISSN: 1573-8744
    Schlagwort(e): nicotine ; cotinine ; pharmacokinetics ; physiologically-based pharmacokinetic model ; interindividual variability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Physiologically based pharmacokinetic (PBPK) models have been developed describing the disposition kinetics of nicotine and its major metabolite, cotinine, in man. Separate 9-compartment, flow-limited PBPK models were initially created for nicotine and cotinine. The physiological basis for compartment designation and parameter selection has been provided;chemical-specific tissue-to-blood partition coefficients and elimination rates were derived from published human and animal data. The individual models were tested through simulations of published studies of nicotine and cotinine infusions in man using similar dosing protocols to those reported. Each model adequately predicted the time course of nicotine or cotinine concentrations in the blood and urine following the administration of nicotine or cotinine. These individual models were then linked through the liver compartments to form a nicotine-cotinine model capable of predicting the metabolic production and disposition of cotinine from administered nicotine. The potential for integrating this functional PBPK model with an appropriate pharmacodynamic model for the characterization of nicotine's physiological effects is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01064421
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  • 78
    Digitale Medien
    Digitale Medien
    Neural networks in pharmacodynamic modeling. Is current modeling practice of complex kinetic systems at a dead end? (1992)
    Springer
    Journal of pharmacokinetics and pharmacodynamics 20 (1992), S. 397-412 
    Details
    ISSN: 1573-8744
    Schlagwort(e): neural networks ; pharmacodynamics ; pharmacokinetics ; modeling ; drug effect prediction ; alfentanil ; model testing ; system analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Neural networks (NN) are computational systems implemented in software or hardware that attempt to simulate the neurological processing abilities of biological systems, in particular the brain. Computational NN are classified as parallel distributed processing systems that for many tasks are recognized to have superior processing capability to the classical sequential Von Neuman computer model. NN are recognized mainly in terms of their adaptive learning and selforganization features and their nonlinear processing capability and are considered most suitable to deal with complex multivariate systems that are poorly understood and difficult to model by classical inductive,logically structured modeling techniques. A NN is applied to demonstrate one of the potentially many applications of NN for modeling complex kinetic systems. The NN was used to predict the effect of alfentanil on the heart rate resulting from a complex infusion scheme applied to six rabbits. Drug input-drug effect data resulting from a repeated, triple infusion rate scheme lasting from 30 to 180 min was used to train the NN to recognize and emulate the input-effect behavior of the system. With the NN memory fixed from the 30- to 180-min learning phase the NN was then tested for its ability to predict the effect resulting from a multiple infusion rate scheme applied in the subsequent 180 to 300 min of the experiment. The NN's ability to emulate the system (30–180 min) was excellent and its predictive extrapolation capability (180–300 min) was very good (mean relative prediction accuracy of 78%). The NN was best in predicting the higher intensity effect and was able to identify and predict an overshoot phenomenon likely caused by a withdrawal effect from acute tolerance. Current modeling philosophy and practice is discussed on the basis of the alternative offered by NN in the modeling of complex kinetic systems. In modeling such systems it is questioned whether traditional modeling practice that insists on structure relevance and conceptually pleasing structures has any practical advantages over the empirical NN approach that largely ignores structure relevance but concentrates on the emulation of the behaviorof the kinetic system. The traditional searching for appropriate models of complex kinetic systems is a painstakingly slow process. In contrast, the search for empirical models using NN will continue to improve, limited only by technological advances supporting the very promising NN developments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01062465
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  • 79
    Digitale Medien
    Digitale Medien
    pH dependent chlorophyll fluorescence quenching in spinach thylakoids from light treated or dark adapted leaves (1992)
    Springer
    Photosynthesis research 31 (1992), S. 11-19 
    Details
    ISSN: 1573-5079
    Schlagwort(e): carotenoid ; chlorophyll fluorescence ; non-photochemical quenching ; pH ; photosynthesis ; zeaxanthin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The pH dependence of maximum chlorophyll fluorescence yield (Fm) was examined in spinach thylakoids in the presence of nigericin to dissipate the transthylakoid pH gradient. 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea (DCMU) was present to eliminate photochemical quenching. Thylakoids were prepared from dark adapted leaves (‘dark’ thylakoids) or preilluminated leaves (‘light’ thylakoids). In the latter there had been approximately 50% conversion of the xanthophyll violaxanthin to zeaxanthin, while no conversion had occurred in the former. In the presence of a reductant such as ascorbate, antimycin A sensitive quenching was observed (half maximal quenching at 5 μM), whose pH dependence differed between the two types of thylakoid. Preillumination of leaves resulted in more quenching at pH values where very little quenching was observed in ‘dark’ thylakoids (pH 5–7.6). This was similar to activation of high-energy-state quenching (qE) observed previously (Rees D, Young A, Noctor G, Britton G and Horton P (1989) FEBS Lett 256: 85–90). Thylakoids isolated from preilluminated DTT treated leaves, that contained no zeaxanthin, behaved like dark thylakoids. A second form of quenching was observed in the presence of ferricyanide, that could be reversed by the addition of ascorbate. This was not antimycin A sensitive and showed the same pH dependence in both types of thylakoid. The former type of quenching, but not the latter, showed similar low temperature fluorescence emission spectra to qE, and was considered to occur by the same mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00049532
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  • 80
    Digitale Medien
    Digitale Medien
    Light, iron, Sam Granick and the origin of life (1992)
    Springer
    Photosynthesis research 33 (1992), S. 163-170 
    Details
    ISSN: 1573-5079
    Schlagwort(e): biosynthetic pathway ; evolution ; free energy ; photochemistry ; photosynthesis ; porphyrin
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Living matter is an organized system which requires a continual flux of energy for its survival. As a working assumption, the flux of energy required for the origin of a self-duplicating cell is taken as the power required for the maintenance of a modern cell: 10 mW per g of carbon or some 105 times the output per gram of the sun. Solar photochemistry supplies the energy for the continuing evolution of life and, by continuity, for its origin. The iron oxide-sulfide photosynthetic unit proposed by S. Granick 35 years ago was meant to supply this energy. The evolution of complex organic photosensitizers is rationalized by the Granick hypothesis that biosynthetic pathways recapitulate their evolution. These concepts are discussed in the context of the evolution of photosynthetic systems and the known properties of these pigments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00039178
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  • 81
    Digitale Medien
    Digitale Medien
    Cultivar differences in leaf photosynthesis of rice bred in Japan (1992)
    Springer
    Photosynthesis research 32 (1992), S. 139-146 
    Details
    ISSN: 1573-5079
    Schlagwort(e): leaf senescence ; mesophyll conductance ; Oryza sativa L. ; photosynthesis ; specific leaf weight ; stomatal conductance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The grain yield of rice (Oryza sativa L.), as well as of other cereal crops, is limited to a large extent, by the supply of photosynthates produced during grain filling period. In this study, flag leaf photosynthesis (LPS) after heading was compared among 32 cultivars bred during the past century in Japan, to determine if the improvement of LPS has occurred with the breeding advance of high yielding cultivars. Measurement of LPS was made for 5 consecutive years in the paddy field, on the flag leaf of the main stem, at heading (LPS-0), and 2 weeks (LPS-2) and 4 weeks (LPS-4) after heading. LPS decreased with advance of leaf senescence from LPS-0 to LPS-2, and then to LPS-4. However, if nitrogen was top-dressed at the heading time, high LPS-2 was maintained, particularly in the newer cultivars. A significant positive correlation between LPS and the released year of cultivar was found at LPS-2, especially in the nitrogen top-dressed plot, but not at LPS-0 or LPS-4. Cultivar difference in LPS of the senescing leaves were not stable through the different years, whereas LPS-0 was stable over years, suggesting that the LPS in the senescent leaf is susceptible to the environmental variation due to the effects on leaf senescence. Cultivar difference in LPS at any stage was closely associated with mesophyll conductance to CO2, and stomatal conductance was also associated with cultivar difference in such a high LPS as LPS-0 and nitrogen top-dressed LPS-2. Significant correlation between LPS and specific leaf weight was not observed at any stage of the flag leaf.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00035948
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  • 82
    Digitale Medien
    Digitale Medien
    Mechanisms for controlling balance between light input and utilisation in the salt tolerant alga Dunaliella C9AA (1992)
    Springer
    Photosynthesis research 32 (1992), S. 181-191 
    Details
    ISSN: 1573-5079
    Schlagwort(e): chlorophyll fluorescence ; Dunaliella ; photosynthesis ; quantum efficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The yield of photosynthetic O2 evolution was measured in cultures of Dunaliella C9AA over a range of light intensities, and a range of low temperatures at constant light intensity. Changes in the rate of charge separation at Photosystem I (PS I) and Photosystem II (PS II) were estimated by the parameters ΦPS I and ΦPS II . ΦPS I is calculated on the basis of the proportion of centres in the correct redox state for charge separation to occur, as measured spectrophotometrically. ΦPS II is calculated using chlorophyll fluorescence to estimate the proportion of centres in the correct redox state, and also to estimate limitations in excitation delivery to reaction centres. With both increasing light intensity and decreasing temperature it was found that O2 evolution decreased more than predicted by either ΦPS I or ΦPS II. The results are interpreted as evidence of non-assimilatory electron flow; either linear whole chain, or cyclic around each photosystem.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00034794
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  • 83
    Digitale Medien
    Digitale Medien
    Conjectures and reveries (1992)
    Springer
    Photosynthesis research 33 (1992), S. 171-176 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; origin of life ; clays
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The origin of photosynthesis is speculated to have involved carbon dioxide and self-replicating iron-rich clays. The later evolution of photosynthesis is considered to have undergone four distinct phases: (1) The photoreduction of carbon dioxide by ferrous ion to form oxalate and formate. (2) The entry of sulfur into the evolving clay system which led to the formation of acetyl thioesters. The polymerization of the acetyl thioeters led to the formation of quinones. The formation of Fe2S2 and Fe4S4 cores appeared in this phase. (3) The ability to fix nitrogen characterized the third phase. This led to the formation of pyrrole, flavin, nicotinamide, phycobilins, porphyrins and chlorophyll. (4) Finally, phosphate entered the evolving system. The chromophores evolved from ferrous ion through the quinones, carotenoids, phycobilins to chlorophyll. This evolution of chromophores implies that photosynthesis began in the UV and evolved through the blue, yellow, orange into the red. The electron transport chain evolved from ferrous ion through the Fe2S2 and Fe4S4 cores to the hemes.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00039179
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  • 84
    Digitale Medien
    Digitale Medien
    Changes in Photosystem II fluorescence in Chlamydomonas reinhardtii exposed to increasing levels of irradiance in relationship to the photosynthetic response to light (1992)
    Springer
    Photosynthesis research 31 (1992), S. 31-40 
    Details
    ISSN: 1573-5079
    Schlagwort(e): Chlamydomonas ; convexity ; chlorophyll a fluorescence ; Photosystem II heterogeneity ; photoinhibition ; photosynthesis ; PS II repair cycle
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effects of a 60 min exposure to photosynthetic photon flux densities ranging from 300 to 2200 μmol m−2s−1 on the photosynthetic light response curve and on PS II heterogeneity as reflected in chlorophyll a fluorescence were investigated using the unicellular green alga Chlamydomonas reinhardtii. It was established that exposure to high light acts at three different regulatory or inhibitory levels; 1) regulation occurs from 300 to 780 μmol m−2s−1 where total amount of PS II centers and the shape of the light response curve is not significantly changed, 2) a first photoinhibitory range above 780 up to 1600 μmol m−2s−1 where a progressive inhibition of the quantum yield and the rate of bending (convexity) of the light response curve can be related to the loss of QB-reducing centers and 3) a second photoinhibitory range above 1600 μmol m−2s−1 where the rate of light saturated photosynthesis also decreases and convexity reaches zero. This was related to a particularly large decrease in PS IIα centers and a large increase in spill-over in energy to PS I.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00049534
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  • 85
    Digitale Medien
    Digitale Medien
    Species-related differences in the electrophoretic behavior of CP 29 and CP 26: An immunochemical analysis (1992)
    Springer
    Photosynthesis research 34 (1992), S. 249-262 
    Details
    ISSN: 1573-5079
    Schlagwort(e): photosynthesis ; light-harvesting chlorophyll-protein complex ; spinach ; maize
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The monomeric chlorophyll-protein complexes, CP 29 and CP 26 seen in the Camm and Green (1980) and Dunahay and Staehelin (1986) green gels do not always migrate in the order of the apparent molecular weight of their apoproteins as determined by denaturing gel electrophoresis. In barley and corn they do, but in spinach they do not. In addition, in some higher plant species these chlorophyll-protein complexes comigrate on green gels causing confusion in the literature. To remedy this situation and circumvent future confusion, we propose that the CP 29 and CP 26 complexes be named according to the relative molecular weight of their apoproteins on denaturing gels. Our proposal is supported by the results obtained from four antibodies used on Western blot samples of whole thylakoids, grana membranes, and PS II preparations from different plants. The higher molecular weight proteins (proposed CP 29's) react strongly to one set of antibodies, and the lower molecular weight proteins (proposed CP 26's) react strongly to a different set. In spinach, CP 26 antibodies react also with CP 29, but the extent of the cross-reactivity depends critically on the gel electrophoresis system used. Accordingly, a lack of antibody reactivity under certain conditions may not indicate two proteins are unrelated, just simply that a particular epitope is no longer accessible following gel electrophoresis with a particular buffer system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00033442
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  • 86
    Digitale Medien
    Digitale Medien
    Concerning oscillations (1992)
    Springer
    Photosynthesis research 34 (1992), S. 387-395 
    Details
    ISSN: 1573-5079
    Schlagwort(e): oscillations ; photosynthesis ; regulation ; phosphate ; down-stream
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029813
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  • 87
    Digitale Medien
    Digitale Medien
    Chloroplast energization and oxidation of P700/plastocyanin in illuminated leaves at reduced levels of CO2 or oxygen (1992)
    Springer
    Photosynthesis research 34 (1992), S. 433-447 
    Details
    ISSN: 1573-5079
    Schlagwort(e): chlorophyll fluorescence ; cyclic electron transport ; photorespiration ; photosynthesis ; Photosystem II ; proton gradient
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Chlorophyll fluorescence, light scattering, the electrochromic shift P515 and levels of some photosynthetic intermediates were measured in illuminated leaves. Oxygen and CO2 concentrations in the gas phase were varied in order to obtain information on control of Photosystem II activity under conditions such as produced by water stress, when stomatal closure restricts access of CO2 to the photosynthetic apparatus. Light scattering and energy-dependent fluorescence quenching indicated a high level of chloroplast energization under high intensity illumination even when linear electron transport was curtailed in CO2-free air or in 1% oxygen with 35 μll-1 CO2. Calculations of the phosphorylation potential based on measurements of phosphoglycerate, dihydroxyacetone phosphate and NADP revealed ratios of intrathylakoid to extrathylakoid proton concentrations, which were only somewhat higher in air containing 35 μl l-1 CO2 than in CO2-free air or 1% oxygen/35 μl l-1 CO2. Anaerobic conditions prevented appreciable chloroplast energization. Acceptor-limitation of electron flow resulted in a high reduction level of the electron transport chain, which is characterized by decreased oxidation of P700, not only under anaerobic conditions, but also in air, when CO2 was absent, and in 1% oxygen, when the CO2 concentration was reduced to 35 μll-1. Efficient control of electron transport was indicated by the photoaccumulation of P700 + at or close to the CO2 compensation point in air. It is proposed to require the interplay between photorespiratory and photosynthetic electron flows, electron flow to oxygen and cyclic electron flow. The field-indicating electrochromic shift (P515) measured as a rapid absorption decrease on switching the light off followed closely the extent of photoaccumulation of P700 + in the light.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00029817
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  • 88
    Digitale Medien
    Digitale Medien
    Dynamic versus static models for photosynthesis (1992)
    Springer
    Hydrobiologia 238 (1992), S. 189-196 
    Details
    ISSN: 1573-5117
    Schlagwort(e): photosynthesis ; phytoplankton ; time scales ; environmental variability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Static P(I) curves relating photosynthesis to the instantaneous light might not be adequate to describe the activity of algal cells in lakes or oceans where mixing can cause a complex pattern of light variation. In recent years experimental results have provided evidence that, subsequent to changes in light, the rate of photosynthesis may be delayed or exhibit complex temporal dynamics. The model DYPHORA (DYnamic model for the PHOtosynthetic Rate of Algae) takes these dynamics into account by introducing two characteristic response times for the biological processes: (1) the effect of light inhibition having a time scale of minutes to a few hours and (2) the time lag of the rate of photosynthesis for increasing light intensities having a time scale of seconds to minutes. The importance of the dynamic relative to the static description of photosynthesis depends on the time scales of the changes in the environment and the biological response, becoming significant when the time scales are comparable.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00048788
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  • 89
    Digitale Medien
    Digitale Medien
    Effects of clay discharges on streams (1992)
    Springer
    Hydrobiologia 248 (1992), S. 215-234 
    Details
    ISSN: 1573-5117
    Schlagwort(e): suspended solids ; turbidity ; algae ; photosynthesis ; light ; mining
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Placer gold-mining on the West Coast of the South Island of New Zealand provided a field test-bed for investigating the impacts of fine inorganic suspensoids (clays) on streams not subjected to other abuses. The suspensions of clays (40% between 0.55 and 1 µm in diameter) seeping into the streams from gold mines were colloidally stable. The clay particles attenuated light in the streamwater with near maximum efficiency leading to severe degradation of stream optical quality. Turbidity increased from a median of 2.4 NTU upstream often to 〉 100 NTU (median 15 NTU) downstream. The stream waters, which were strongly-coloured by humic substances, were changed from a dark organge colour to a bright ‘muddy’ appearance downstream of mining, and visual clarity was reduced from a few metres to as low as 0.03 m (median 0.33 m). The clay discharges decreased light penetration into the stream water such that irradiance averaged over a 12 hr photoperiod at the bed (typically about 0.3 m depth in runs at baseflow) fell from about 340 µE m−2 s−1 upstream to as low as 80 µE m−2 s−1 (median 190 µE m−2 s−1) at matched downstream sites. This reduction in light proportionally reduced benthic primary productivity downstream of the mining activity. In turn this reduced benthic algal biomass and lowered the phototrophic content of the epilithon. In spite of their extremely low settling velocities (〈 1 µm s−1) some clay particles were deposited on the stream bed owing to entrapment in the epilithon matrix. This decreased the organic content of the epilithon (from an average of 19% upstream to 8.5% downstream) so reducing its quality as food for invertebrate animals.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00006149
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  • 90
    Digitale Medien
    Digitale Medien
    Photosynthetic performance of deep-water macroalgae (Phaeophyta, Dictyotales) off Bermuda (1992)
    Springer
    Hydrobiologia 231 (1992), S. 93-98 
    Details
    ISSN: 1573-5117
    Schlagwort(e): photosynthesis ; macroalgae ; deep-water ; Bermuda ; Dictyotales
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic performance and dark respiration rates were determined in situ for abundant macroalgae occurring between 27–49 m depths off Bermuda. Brown algae, particularly members of the order Dictyotales, predominated at all deep-water sites, and Stypopodium zonale was the most abundant species. Species showed net photosynthesis at very low ambient irradiances (〈0.01 maximum Io). Lobophora variegata, a species with a highly decumbent growth form, had low productivity across all irradiances. In contrast, Dictyota spp. (D. bartayresii, D. dichotoma, D. divaricata) and S. zonale had high photosynthetic capacity (ca. 400 µmol O2 gdw−1 h−1), and light saturation was not evidenced at the highest ambient irradiance level (300 µE m−1 s−1) for species with thin, flat thalli. Light-harvesting pigment concentrations reflected tissue-nitrogen levels. C:N atom ratios, except for L. variegata and D. divaricata, were within the ratio for balanced growth. The repeated occurrence and photosynthetic efficiency of these Dictyotalean species in subtropical and tropical deep-water habitats emphasize their successful adaptation to low-light, nutrient-poor environments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00006501
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  • 91
    Digitale Medien
    Digitale Medien
    Diel periodicity in phytoplankton productivity (1992)
    Springer
    Hydrobiologia 238 (1992), S. 1-35 
    Details
    ISSN: 1573-5117
    Schlagwort(e): periodicity ; diel ; circadian ; clocks ; photosynthesis ; phytoplankton
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Daily variation in phytoplankton productivity influences the dynamics and linkages between several large scale processes in aquatic ecosystems. As part of an opening address to the 5th International workshop for the Group for Aquatic Productivity (GAP), the daily patterns of variability in photosynthesis for different algal classes was introduced and accompanied by a discussion of the sources of environmental and endogenous regulation of repeating biological oscillations that occur in phytoplankton on timescales of one day. It is suggested that one way to develop a database that serves to sort and predict phytoplankton variability over the day may be to encourage the creation of a ‘temporal library’. Such a library would be comprised of temporally fixed maps of circadian clock-controlled rhythms for individual species, as well as temporally variable maps of diel periodicities that only can be defined for a selected set of environmental conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00048771
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  • 92
    Digitale Medien
    Digitale Medien
    High biomass and production of picoplankton in a Chinese integrated fish culture pond (1992)
    Springer
    Hydrobiologia 237 (1992), S. 15-23 
    Details
    ISSN: 1573-5117
    Schlagwort(e): picoplankton ; photosynthesis ; primary production ; cyprinids ; fish farm pond
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The phytoplankton dynamics of a Chinese integrated fish culture pond in the suburbs of Shanghai were studied in September and October 1989. The chlorophyll a concentration was high with a range of 62.5–127.3 µg l−1; however, daily net production of phytoplankton was relatively low, with a range of 0.53–1.94 gC m −2 d−1. Of the total phytoplankton biomass, 70–87% was composed of nanoplankton (〈10 µm) and picoplankton, probably because of the selective feeding by phytoplanktivorous carp. In particular, the chlorophyll a concentration of picoplankton was 2.1 – 14.1 mg m −3, and its contribution to total phytoplankton production rate was high (18–68%).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00008423
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  • 93
    Digitale Medien
    Digitale Medien
    Photosynthetic activity of phytoplankton in a high altitude lake (Emerald Lake, Sierra Nevada, California) (1992)
    Springer
    Hydrobiologia 230 (1992), S. 37-48 
    Details
    ISSN: 1573-5117
    Schlagwort(e): photosynthesis ; alpine lake ; phytoplankton
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthetic activity by phytoplankton was measured during the ice-free seasons of 1984, 1985 and 1987 using the 14C radioassay in high altitude Emerald Lake (California). Relative quantum yield (αB) and light-saturated chlorophyll-specific carbon uptake (Pm B) were calculated from the relationship of light and photosynthesis fitted to a hyperbolic tangent function. Temporal changes in Pm B showed no regular pattern. Seasonal patterns of αB generally had peaks in the summer and autumn. Phytoplankton biomass (as measured by chlorophyll a) and light-saturated carbon uptake (Pm) had peaks in the summer and autumn which were associated with vertical mixing. Estimates of mean daily carbon production were similar among the three years: 57 mg C m−2 2 d−1 in 1984, 70 mg C m−2 2 d−1 in 1985 and 60 mg C m−2 d−1 in 1987. Primary productivity in Emerald Lake is low compared to other montane lakes of California and similar to high-altitude or high-latitude lakes in other regions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00015113
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  • 94
    Digitale Medien
    Digitale Medien
    Influence of medium frequency light/dark cycles of equal duration on the photosynthesis and respiration of Chlorella pyrenoidosa (1992)
    Springer
    Hydrobiologia 238 (1992), S. 53-62 
    Details
    ISSN: 1573-5117
    Schlagwort(e): light/dark cycles ; photosynthesis ; Chlorella ; diurnal variations ; respiration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Chlorella pyrenoidosa was grown in three continuous cultures each receiving a different light regime during the light period of a diurnal cycle. Hourly samples taken during the light period were subjected to medium frequency light/dark oscillations of equal duration, ranging from 3 to 240 seconds. The oxygen consumption and production of each sample were measured with an oxygen electrode in a small oxygen chamber. Although the light/dark cycles had little overall influence on photosynthetic activity, the microalgae appeared to adapt to the light regime to which they were subjected. Large differences were found between the maximum chlorophyll-specific production rates (P infmax supB ), the chlorophyll-specific production rates (PB) and the respiration rates between the cultures and treated subsamples. Respiration rates increased during the light period, whilst PB either increased, or had a mid light period minimum or maximum. The culture which received an hourly light oscillation during the light period had the highest P infmax supB and lowest respiration rates, and it is suggested that these algae react as in nature, whereas either a sinusoidal or a block light pattern is ‘unnatural’. The latter light regime is commonly used in laboratory studies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00048773
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  • 95
    Digitale Medien
    Digitale Medien
    The effect of dynamic light regimes on Chlorella II. Minimum quantum requirement and photosynthesis-irradiance parameters (1992)
    Springer
    Hydrobiologia 238 (1992), S. 79-88 
    Details
    ISSN: 1573-5117
    Schlagwort(e): dynamic light regime ; photosynthesis ; respiration ; quantum requirement
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Comparisons were made of photosynthesis in three light limited cyclostat cultures (LD = 8:16, dilution rate 0.7 d−1) of Chlorella pyrenoidosa, differing only in the dynamics of irradiance supply: as a constant rate, i.e. a block culture; as a sine function of the light period, i.e. a sinusoidal culture; as an 8 h sine function superimposed by an 1 h sine function, i.e. an oscillating culture. The sinusoidal culture had a constant minimum quantum requirement for oxygen evolution (QR) of 10.8 over the photoperiod. The OR of the oscillating culture increased from 24 to 37 during the photoperiod. From changes in α and P max we suggest that: (1) photosynthetic units (PSU) of the block and sinusoidal sulture increased in number; (2) increasingly fewer chlorophyll molecules participated in oxygenic photosynthesis with a decreasing turnover time of the PSU's during an oscillating photoperiod. Values of I k decreased slightly in the block culture, increased slightly in the sinusoidal culture and showed a twofold increase in the oscillating culture. From the ratio of in situ oxygen production (qO2) and P max we infer a balanced equilibrium between photosystem activity and electron transport capacity for the block and sinusoidal culture. We hypothesize that the qO2 values of the oscillating culture underestimated true oxygen production rates due to a nonlinear response at peak light intensities. The results show that a dynamical photoperiod provoked significantly different photosynthetic responses, even though the overall growth rate was unaffected.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00048776
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  • 96
    Digitale Medien
    Digitale Medien
    Epilithic chlorophyll a, photosynthesis, and respiration in control and fertilized reaches of a tundra stream (1992)
    Springer
    Hydrobiologia 240 (1992), S. 121-131 
    Details
    ISSN: 1573-5117
    Schlagwort(e): streams ; arctic ; tundra ; epilithon ; photosynthesis ; respiration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Photosynthesis and respiration by the epilithic community on cobble in an arctic tundra stream, were estimated from oxygen production and consumption in short-term (4–12 h), light and dark, chamber incubations. Chlorophyll a was estimated at the end of each incubation by quantitatively removing the epilithon from the cobble. Fertilization of the river with phosphate alone moderately increased epilithic chlorophyll a, photosynthesis, and respiration. Fertilization with ammonium sulfate and phosphate, together, greatly increased each of these variables. Generally, under both control and fertilized conditions, epilithic chlorophyll a concentrations (mg m−2), photosynthesis, and respiration (mg O2 m−2, h−1) were higher in pools than in riffles. Under all conditions, the P/R ratio was consistent at ∼ 1.8 to 2.0. The vigor of epilithic algae in riffles, estimated from assimilation coefficients (mg O2 [mg Chl a]−1 h−1) was greater than the vigor of epilithic algae in pools. However, due to the greater accumulation of epilithic chlorophyll a in pools, total production (and respiration) in pools exceeded that in riffles. The epilithic community removed both ammonium and nitrate from water in chambers. Epilithic material, scoured by high discharge in response to storm events and suspended in the water column, removed ammonium and may have increased nitrate concentrations in bulk river water. However, these changes were small compared to the changes exerted by attached epilithon.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00013457
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  • 97
    Digitale Medien
    Digitale Medien
    Carbon isotope ratio and photosynthetic activity of phytoplankton in the eutrophic Mikawa Bay, Japan (1992)
    Springer
    Ecological research 7 (1992), S. 355-361 
    Details
    ISSN: 1440-1703
    Schlagwort(e): carbon isotope ratio ; photosynthesis ; phytoplankton
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Primary production by phytoplankton in the eutrophic Mikawa Bay, Japan, was studied by simultaneous measurements of natural carbon isotope ratio (δ 13C) and short-term carbon uptake rates (13C tracer study) of size-fractionated nannoplankton (〈10 μm) and net plankton (〉10 μm) samples. Short-term photosynthetic rates, which represent the physiological state of algae, were variable regardless of standing stock sizes. Theδ 13C values of particulate organic carbon (POC) in June and July displayed horizontal variations for both the net plankton fraction (−19.8 to −12.7‰) and the nannoplankton fraction (−22.0 to −12.8‰). For both fractions, low concentrations of POC had more negativeδ 13C values (−22 to −18‰). Highδ 13C values for the net plankton were found when POC concentrations were much higher, due to red tide. This suggests that the increase in algal standing crop for the net plankton fraction resulted from accelerated photosynthetic activity. However the nannoplankton fractions with higher POC values have relatively lowδ 13C values.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02347102
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  • 98
    Digitale Medien
    Digitale Medien
    Influence of the mixing regime on algal photosynthetic performance in laboratory scale enclosures (1992)
    Springer
    Hydrobiologia 238 (1992), S. 111-118 
    Details
    ISSN: 1573-5117
    Schlagwort(e): mixing regime ; Laboratory Scale Enclosures ; phytoplankton ; photosynthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The photosynthesis of plankton sampled from the eutrophic Lake Loosdrecht was studied in Laboratory Scale Enclosures (LSEs) with regard to the rate of mixing. First, two LSEs were operated at different mixing rates. No significant differences in photosynthetic performance were found, with the exception of a depressed photosynthesis in the afternoon in the LSE which had a low mixing rate. Secondly, when mixing was stopped, the phytoplankton which stayed in the dark due to the steep light gradient in the LSE responded by changing its maximal photosynthetic capacity. The results show that the filamentous cyanobacteria in the lake can respond rapidly to changes in the depth of the mixed layer by altering their photosynthetic performance.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00048779
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  • 99
    Digitale Medien
    Digitale Medien
    The physiological basis for genetic improvement of oil palm in Malaysia (1992)
    Springer
    Euphytica 60 (1992), S. 179-184 
    Details
    ISSN: 1573-5060
    Schlagwort(e): breeding ; Elaeis guineensis ; harvest index ; oil palm ; photosynthesis ; selection progress
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Yield of Deli dura oil palms after four generations of selection was 60% greater than that of the unselected base population. Total above-ground dry matter production was increased by selection, apparently through better utilisation of solar radiation. The dry matter requirement for vegetative growth was unchanged, so a greater surplus remained for fruit production in the selected palms. Crossing the dura and pisifera to give the thin-shelled tenera fruit type improved partitioning of dry matter within the fruit, giving a 30% increase in oil yield at the expense of shell, without changing total dry matter production.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00039396
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  • 100
    Digitale Medien
    Digitale Medien
    A differential effect of 3-(3′4′ dichlorophenyl)-1,1 dimethyl urea and atrazine on fluorescence kinetics in chloroplasts (1992)
    Springer
    Photosynthesis research 31 (1992), S. 139-148 
    Details
    ISSN: 1573-5079
    Schlagwort(e): Fe ; photosynthesis ; Photosystem II ; variable fluorescence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract It was found that DCMU had a differential effect at two concentration ranges on variable fluorescence kinetics in isolated chloroplasts. The increase in fluorescence rate at low concentrations of DCMU was abolished by preincubation of chloroplasts with ferricyanide or formate, treatments which were shown to convert Fe in the PS II reaction center (i.e., the FeQA complex) into a non-oxidizable form, but it was not affected by Tris treatment. Increase in fluorescence kinetics (at the initial linear rate) at high concentrations of DCMU was found to be abolished by Tris treatment but it was only marginally affected by ferricyanide or formate treatments. The effect of Tris could be abolished by addition of hydroquinone-ascorbate, which restored electron flow to the pool of secondary acceptors. Contrary to the effect of DCMU, no such differential concentration dependence of the variable fluorescence kinetics was found for atrazine. The increase in fluorescence kinetics (at the initial linear rate) at a low concentration rate of DCMU is presumably restricted to units which contain an oxidizable Fe in the FeQA complex. Increase in fluorescence kinetics (at the initial linear rate) at high DCMU concentration is probably related to the effect of DCMU at the QB site.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00028790
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