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  • pharmacokinetics  (24)
  • Gibberellin
  • Pinus ponderosa
  • Springer  (35)
  • Annual Reviews
  • National Academy of Sciences
  • Springer Science + Business Media
  • 1980-1984  (35)
  • 1981  (21)
  • 1980  (14)
Collection
Keywords
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  • Springer  (35)
  • Annual Reviews
  • National Academy of Sciences
  • Springer Science + Business Media
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  • 1980-1984  (35)
Year
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 17 (1980), S. 111-116 
    ISSN: 1432-1041
    Keywords: zimelidine ; norzimelidine ; antidepressants ; pharmacokinetics ; bioavailability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The systemic availability of a new antidepressant, zimelidine, and of its pharmacologically active metabolite, norzimelidine, was studied in six healthy male volunteers. Three single doses of zimelidine (25 mg and 100 mg orally and 25 mg i.v.) and two single doses of norzimelidine (25 mg orally and i. v.) were given to each volunteer allowing at least seven days between administrations. Plasma concentrations of zimelidine and norzimelidine were determined in serial blood samples by HPLC. Following oral zimelidine peak plasma concentrations of the metabolite were attained about 3 h after dosing. Oral administration of norzimelidine itself resulted in a plasma concentration profile for this compound that was similar to that observed after oral zimelidine. Utilising the plasma concentration data following intravenous infusion of each compound, the elimination half-lives for zimelidine and norzimelidine were calculated to be 5.1 h (range 4.3–6.0) and 15.5 h (range 10.6–22.9) respectively. The total body clearances of the 2 compounds were similar at 0.52 l · min−1 (range 0.26–0.70) for zimelidine and 0.56 l · min−1 (range 0.28–0.83) for norzimelidine. The substantially longer elimination half-life of norzimelidine was apparently the result of a larger volume of distribution (9.4 l · kg−1; range 7.8–11.4) for this metabolite, as compared to zimelidine (3.21 · kg−1; range 1.6–4.9). The calculated bioavailability of zimelidine was 26% (range 9.1–39) after the 25 mg oral dose, and 29% (range 14–46) after the 100 mg dose. The bioavailability of norzimelidine was 66% (range 36–91). However, oral administration of zimelidine resulted in as much or more norzimelidine reaching the systemic circulation, as the oral administration of norzimelidine itself. This is important as a large part of the activity of the drug may be due to the metabolite.
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 19 (1981), S. 279-285 
    ISSN: 1432-1041
    Keywords: chlordiazepoxide ; alcoholic liver disease ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The clearance of chlordiazepoxide from the systemic circulation was studied in 20 subjects which included 15 patients with alcoholic hepatitis and 5 normal volunteers. The half-life for the appearance of the drug in the systemic circulation was found to increase exponentially with age (r=0.73, P〈0.0005) and was independent of the presence of alcoholic hepatitis. The metabolic clearance of chlordiazepoxide was significantly lower in the patients than in the normal subjects (7.6 compared to 13.8 ml/kg-h, P〈0.005). Linear regression analysis revealed a significant correlation between clearance and albumin (r=0.77, P〈0.00005). However, the predictive value of this relationship was shown to be minimal. Multiple regression analysis produced only a slight improvement in the correlation when both albumin and lactate dehydrogenase were used as variables (r=0.83, P〈0.00005). In six of the patients, a second clearance study was conducted three weeks following their initial one. All repeat subjects showed improvement both clinically and as reflected by their laboratory tests for liver injury, but there was not a significant change in their clearance of chlordiazepoxide. Multiple regression analysis of the clearance data on the initial and repeat subjects showed a significant correlation between clearance and the variables age, albumin, and lactate dehydrogenase (r=0.91, P〈0.0025). This relationship suggests that over a short period of time (where age can be considered constant) changes in albumin and lactate dehydrogenase could be potentially useful in predicting clearance changes in a single individual.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 19 (1981), S. 119-125 
    ISSN: 1432-1041
    Keywords: tolmesoxide ; metabolite ; volunteers ; pharmacokinetics ; intravenous ; oral ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary A high pressure liquid chromatographic assay was developed for simultaneous measurement of the plasma levels of tolmesoxide and its principal metabolite, RX71112. The assay was used to study the disposition of intravenous and oral tolmesoxide in ten normotensive subjects. Two exponential terms were required to describe the disposition of the drug following intravenous administration, whilst a single exponential term sufficied to account for the decay in the plasma concentration after oral administration. The bioavailability of oral tolmesoxide from capsules averaged 84.5% and was independent of dose. The mean half-life after i. v. dosing was 2.6 h (±0.3 SEM) compared to values of 1.9 h (±0.1 SEM) and 2.7 h (±0.5 SEM) following 200 and 400 mg oral doses respectively. In all subjects RX71112 appeared in plasma shortly after tolmesoxide following both routes of administration. The terminal half-life of the metabolite was significantly longer than tolmesoxide with a mean value of 4.9 h (±0.9 SEM) following the 200 mg oral dose of tolmesoxide. The binding of tolmesoxide and RX71112 at therapeutic plasma concentration was 36.8% (±0.5 SEM) and 58.5% (±0.3 SEM) and this remained unchanged at higher concentrations.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 20 (1981), S. 293-298 
    ISSN: 1432-1041
    Keywords: neuromuscular relaxants ; fazadinium ; pharmacokinetics ; renal failure ; neuromuscular transmission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetic behaviour and neuromuscular blockade produced by the administration of fazadinium bromide at a dose of 1 mg/kg have been studied in seven patients with end-stage renal failure. No significant differences were found in the pharmacokinetic or pharmacodynamic properties when compared with patients with normal renal function. It is suggested that fazadinium may be superior to either d-tubocurarine or pancuronium in providing muscle relaxation for patients with renal failure.
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  • 5
    ISSN: 1432-2048
    Keywords: Gibberellin ; Growth temperature ; Lactuca ; Temperature (gibberellin)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between elongation growth and the incorporation of [3H]gibberellin A1 ([3H]GA1) into a 2,000g pelletable (2KP) fraction from lettuce (Lactuca sativa L., cv. Arctic) hypocotyl sections has been examined. Sections were loaded with incremental amounts of GA1 under conditions where growth was arrested (5° C) or permitted (30° C) and, after 16 h, all were transferred to a GA-free medium at 30° C. Growth and 2KP radioactivity were measured at this point and after a further 24 h in the chase medium. Uptake was reduced by 80% at 5° C, as compared to 30° C, but 2KP labelling and protein synthesis were only reduced by half. The growth rate of the 5° C pretreated sections during the chase period was comparable to that observed during the pulse in the 30° C material but the dose/response relationship was flatter. Low temperature sections incorporated a much higher percentage of GA1 uptake into the 2KP fraction (27% at maximum) but the absolute levels of labelling at this temperature were lower than those measured at 30° C. The data are interpreted as showing that 2KP labelling is not a consequence of growth. It must either precede response or be an unconnected concurrent process.
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  • 6
    ISSN: 1432-2048
    Keywords: Agrostemma ; Gibberellin ; Growth retardant ; Photoperiodism ; Stem elongation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Agrostemma githago is a long-day rosette plant in which transfer from short days (SD) to long days (LD) results in rapid stem elongation, following a lag phase of 7–8 d. Application of gibberellin A20 (GA20) stimulated stem elongation in plants under SD, while 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine-carboxylate methyl chloride (AMO-1618, an inhibitor of GA biosynthesis) inhibited stem elongation in plants exposed to LD. This inhibition of stem elongation by AMO-1618 was overcome by simultaneous application of GA20, indicating that GAs play a role in the photoperiodic control of stem elongation in this species. Endogenous GA-like substances were analyzed using reverse-phase high-performance liquid chromatography and the d-5 corn (Zea mays L.) assay. Three zones with GA-like activity were detected and designated, in order of decreasing polarity, as A, B, and C. A transient, 10-fold increase in the activity of zone B occurred after 8–10 LD, coincident with the transition from lag phase to the phase of rapid stem elongation. After 16 LD the activity in this zone had returned to a level similar to that under SD, even though the plants were elongating rapidly by this time. However, when AMO-1618 was applied to plants after 11 LD, there was a rapid reduction in the rate of stem elongation, indicating that continued GA biosynthesis was necessary following the transient increase in activity of zone B, if stem elongation was to continue under LD. It was concluded that control of stem elongation in A. githago involves more than a simple qualitative or quantitative change in the levels of endogenous GAs, and that photoperiodic induction alters both the sensitivity to GAs and the rate of turnover of endogenous GAs.
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  • 7
    ISSN: 1432-2048
    Keywords: Agrostemma ; Gibberellin ; Photoperiodism ; Stem elongation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The following seven gibberellins (GAs) have been identified by gas chromatography-mass spectrometry in shoots and leaves of the long-day plant Agrostemma githago: GA53, GA44, GA19, GA17, GA20, GA1, and 3-epi-GA1. The levels of these compounds were measured, using selected ion monitoring, during photoperiodic induction. The levels of GA44, GA19, GA17, and GA20 all increased to a peak at eight long days (LD), followed by a decline, while the levels of GA1 and 3-epi-GA1 did not reach a peak until 12 LD. The level of GA53 remained steady over the first 10–12 LD. Later in the LD treatment the levels of GA53, GA44, GA19, and GA17 increased again. The rate of metabolism of all GAs except GA53 was higher after 12–16 LD than under short days. These data thus provide indirect evidence for an effect of photoperiodic induction on GA turnover in A. githago.
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  • 8
    ISSN: 1432-2048
    Keywords: Auxin ; Branch angle ; Conifers ; Cupressus ; Ethylene ; Gibberellin ; Hyponasty
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Decapitation, gibberellin A3, high light, their combination, and certain levels of indole-3-acetic acid increase ethylene evolution and also induce branch hyponasty (upturning) in seedlings of Cupressus arizonica Greene, the increase in ethylene preceding obvious hyponasty. Exogenous ethylene also causes branch hyponasty and branches of seedlings maintained in an atmosphere scavenged of ethylene by mercuric perchlorate grow downwards. It is concluded that ethylene may play a role in the apical control of branch angle in some conifers. The positive effect of ethylene in increasing branch hyponasty may be direct, or reflect changes in levels of endogenous auxin and/or gibberellin.
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  • 9
    ISSN: 1432-2048
    Keywords: Gibberellin ; Growth temperature ; Lactuca ; Temperature (gibberellin)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The relationship between elongation growth and the incorporation of [3H]gibberellin A1 ([3H]GA1) into a 2,000g pelletable (2KP) fraction from lettuce (Lactuca sativa L., cv. Arctic) hypocotyl sections has been examined. Sections were loaded with incremental amounts of GA1 under conditions where growth was arrested (5° C) or permitted (30° C) and, after 16 h, all were transferred to a GA-free medium at 30° C. Growth and 2KP radioactivity were measured at this point and after a further 24 h in the chase medium. Uptake was reduced by 80% at 5° C, as compared to 30° C, but 2KP labelling and protein synthesis were only reduced by half. The growth rate of the 5° C pretreated sections during the chase period was comparable to that observed during the pulse in the 30° C material but the dose/response relationship was flatter. Low temperature sections incorporated a much higher percentage of GA1 uptake into the 2KP fraction (27% at maximum) but the absolute levels of labelling at this temperature were lower than those measured at 30° C. The data are interpreted as showing that 2KP labelling is not a consequence of growth. It must either precede response or be an unconnected concurrent process.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    European journal of clinical pharmacology 18 (1980), S. 269-273 
    ISSN: 1432-1041
    Keywords: paracetamol ; thyrotoxicosis ; hypothyroidism ; drug disposition ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The absorption, distribution and elimination of oral paracetamol have been studied in patients before and after treatment of thyrotoxicosis (n=7) and hypothyroidism (n=4). Absorption was faster in patients with untreated thyrotoxicosis than when subsequently euthyroid. The peak paracetamol concentration, however, was lower in thyrotoxic patients due to an apparent increase in the total body clearance and a shorter plasma half-life. Both absorption and elimination rates were reduced in hypothyroid patients, but were not significantly different from the euthyroid results. When estimated using a two compartment model the total volume of distribution and the hybrid distribution rate constants were unrelated to thyroid status, but the apparent volume of the central compartment was significantly greater in the thyrotoxic group. These changes in drug disposition may contribute to differences in drug response seen in thyroid disease.
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