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  • calcium  (2)
  • etintidine  (2)
  • Springer  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Calcified tissue international 33 (1981), S. 545-548 
    ISSN: 1432-0827
    Keywords: calmodulin ; calcium ; mineralisation ; tooth germ
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Summary Calmodulin, a calcium binding protein, has been implicated in the regulation of many calcium-dependent biological processes. Since calcium has an important role in hard tissue genesis, both at intra- and extracellular levels, we anticipate that calcium binding proteins may modulate this process. The present study investigated a mineralising tissue, the rat molar tooth germ, to determine the presence of calmodulin-like activity. A heat-treated cell-free extract of tooth germs provided enhancement of Ca2+-dependent Mg2+-ATPase and 3′:5′-nucleotide phosphodiesterase activity. No enhancement occurred in the absence of calcium or in the presence of trifluoperazine. SDS-polyacrylamide gel electrophoresis of this extract revealed a protein band of approximately 18,000 mol. wt. These findings indicate the presence of calmodulin-like activity in rat molar tooth germs and support the proposal that calcium and calcium binding proteins, in particular calmodulin, have a major regulatory role in the biology of mineralising tissues.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-904X
    Keywords: etintidine ; high-performance liquid chromatography (HPLC) ; solid extraction ; determination of etintidine in plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper describes a new, rapid solid extraction method for the determination of etintidine in plasma. The method employs a semiautomatic sample preparation system. Plasma samples and the internal standard (cimetidine) were applied onto octyl-bonded silica extraction columns. The extraction columns were then subjected to Tris buffer and water wash and were subsequently loaded onto an automatic sample injection system. The contents of the extraction columns were eluted on-line with a mobile phase of acetonitrile:methanol:0.1% ammonium hydroxide (85:10:5, by volume) onto a silica analytical column and detected by UV absorption at 229 nm. The chromatographic condition separates etintidine from some of its metabolites and other endogenous components in plasma. The detection limit for etintidine was 0.02–0.05 µg/ml when 0.2 ml of plasma was used. This method has been used for the determination of plasma etintidine levels in humans and mice after oral administration of etintidine and was found to be suitable for pharmacokinetic/bioavailability studies of etintidine in humans and animals. The method can also be used for the quantitative determination of cimetidine and certain metabolites of etintidine.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5036
    Keywords: calcium ; plasma membrane ; root elongation ; salinity ; sodium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract To gain a better understanding of the relations between root elongation and the amount of Ca2+ bound to the plasma membrane (PM), melon plants were grown in aerated solutions containing different concentrations of CaCl2 with various concentrations of NaCl or mannitol. With increasing external concentrations of NaCl or mannitol, root elongation was suppressed. Addition of CaCl2 to the external medium alleviated the inhibition of root elongation by high concentrations of Na+, but not of mannitol. Root elongation in media containing high concentrations of NaCl was correlated with the computed amount of Ca2+ bound to the PM. A model describing relative root elongation (RRL) under salt stress was developed. This model takes into account the osmotic potential in the growing solution (based on the mannitol experiments) and the computed amount of Ca2+ bound to the PM. Calcium binding was calculated by applying a Gouy-Chapman-Stern sorption model using the same parameters deduced from studies on PM vesicles. This model combines electrostatic theory with competitive binding at the PM surface. The model for RRL allowed the computation of a critical value for the fraction of negative sites binding Ca2+ on the PM needed for nearly optimal (95%) root elongation. Any decrease below this critical value decreased the RRL. Root elongation of Honey Dew (salt-resistant cv.) was greater than that of Eshkolit Ha'Amaqim (salt-sensitive cv.) under NaCl stress. Nearly optimal root growth for Honey Dew and Eshkolit Ha'Amaqim occurred when 40% and 51% of total membrane charged sites were bound by Ca2+, respectively. The effect of osmotic potential on the suppression of root elongation was the same for the two cultivars. To our knowledge, this report provides the first fully quantitative estimates of PM-bound Ca2+ relative to salt toxicity.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of pharmacokinetics and pharmacodynamics 15 (1987), S. 557-568 
    ISSN: 1573-8744
    Keywords: etintidine ; propranolol ; 4-hydroxypropranolol ; interaction ; pharmacokinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Etintidine HCl is a potent H2 -blocker. The effect of clinical doses of etintidine on the disposition of a single oral dose of propranolol was investigated in 12 normal subjects. This was a double-blind, two-way crossover study. Each subject received etintidine (400 mg) or placebo twice a day with meals for 4 days on two occasions (separated by 4 days). On each occasion, the subjects were fasted overnight on Day 3 and were given an oral dose of Inderal® (40 mg propranolol hydrochloride) 30 min following the administration of the morning dose of etintidine or placebo on Day 4. Blood samples were collected prior to and up to 24 hr following the administration of propranolol. The plasma samples were analyzed for propranolol and 4-hydroxypropranolol by HPLC. Comparison of the pharmacokinetic parameters of propranolol between etintidine and the placebo groups indicates that etintidine significantly increased the AUC0−∞,values (573.5 vs. 146.4 ng·hr/ml, p=0.0001)and prolonged the elimination half-life (4.61 vs. 2.33 hr) of propranolol. Statistical evaluation of the pharmacokinetic parameters of 4-hydroxypropanolol indicates that etintidine also increased the AUC0−24 values (43.8 vs. 16.4 ng·hr/ml, p=0.0028) and prolonged the elimination half-life (4.87 vs. 1.97 hr) of 4-hydroxypropranolol. The data suggest that etintidine, like cimetidine, impaired the elimination of propranolol. Etintidine also protracted the elimination of 4-hydroxypropranolol, an active metabolite of propranolol.
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