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  • 1
    Digitale Medien
    Digitale Medien
    Identification of Insulin in Chick Embryo Retina During Development and Its Inhibitory Effect on DNA Synthesis (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 58 (1992), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: Incubation of chick embryo retinal explants with insulin resulted in a pronounced inhibition of thymidine uptake and incorporation into trichloroacetic acid-insoluble fraction. The inhibitory effect was highest with explants from embryos at day 7 and day 8, and thereafter it declined markedly with the age of embryos until day 11. A time-course study of the effect revealed that the inhibition occurred after a lag time; both thymidine uptake and incorporation were not altered significantly after 2–6 h of incubation with insulin, but began to decrease thereafter, reaching the maximum after 16 h. The effect was also dose dependent. After 16 h of incubation, the maximal inhibition (65%) was found with 10–8M insulin. Insulin caused similar effects also on thymidine kinase activity. All these effects were obtained by using minimal essential medium without glutamine. The addition of glutamine to the medium reduced the inhibitory effect of insulin. Retinas of chick embryos contain immunoreactive insulin. Retinal immunoreactive insulin was at the highest level (1.12 ng/mg of protein) in the youngest retinas studied (day 6), then it declined with age, reaching the lowest value (0.58 ng/mg of protein) at day 14. This value did not vary significantly during the third week of development. A potential biological role of insulin in retinal development is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1992.tb11349.x
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  • 2
    Digitale Medien
    Digitale Medien
    Biochemical Aspects of Chick Embryo Retina Development: The Effects of Glucocorticoids (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 52 (1989), S. 0 
    Details
    ISSN: 1471-4159
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Medizin
    Notizen: Abstract: In chick embryo retina during development, DNA synthesis and the activities of DNA polymerase, thymidine kinase, thymidylate synthetase, and ornithine decarboxylase (ODC) declined in parallel from day 7 to 12. The administration in ovo of hydrocortisone reduced significantly, particularly at 8–10 days of incubation, both DNA synthesis and the four enzyme activities tested. The effect was dose dependent, reaching the maximum with 50–100 nmol of hydrocortisone, 8–16 h after treatment. The highest inhibition was found for ODC activity (70%), followed by thymidine kinase activity (62%) and DNA synthesis (45%), whereas activities of DNA polymerase and thymidylate synthetase were reduced only by 30%. The inhibitory effect was exerted by all the glucocorticoids tested, with dexamethasone and hydrocortisone being the most efficacious. The results support the view that glucocorticoids reduce the proliferative events in chick embryo retina, particularly at 8–10 days of embryonic life.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb09198.x
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  • 3
    Digitale Medien
    Digitale Medien
    Nickel(II) chelation kinetics involving dialkylmalonate ligands (1976)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 80 (1976), S. 239-243 
    Details
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie , Physik
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1021/j100544a005
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  • 4
    Digitale Medien
    Digitale Medien
    A factor derived from chick embryo retina which inhibits DNA synthesis of retina itself (1992)
    Springer
    Neurochemical research 17 (1992), S. 1041-1048 
    Details
    ISSN: 1573-6903
    Schlagwort(e): Chick embryo retina ; development ; inhibitory factors ; retinal explants ; DNA synthesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Chick embryo retinas contain a peptide factor that inhibits DNA synthesis in explants of chick embryo retina. The inhibitory factor, obtained by acid/ethanol extraction from 15-day-old chick embryo retinas, was partially purified by affinity chromatography on heparin-sepharose CL-6B and gel filtration on Sephadex G-100. The inhibitor reduced DNA synthesis with maximal effects observed in retinal explants from 7 to 8-day-old chick embryos. The inhibitory effect became apparent after 10 h of incubation and reached the maximum levels after 16 h. DNA-inhibiting activity was heat and acid-stable and was destroyed by trypsin and alkaline treatments. The inhibitory effect was observed in retinal explants incubated in a medium free froml-glutamine, and the addition of this compound to the medium reduced the inhibitory effect in a concentration-dependent manner.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00966834
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  • 5
    Digitale Medien
    Digitale Medien
    Insulin synthesis in chick embryo retinas during development (1994)
    Springer
    Neurochemical research 19 (1994), S. 821-825 
    Details
    ISSN: 1573-6903
    Schlagwort(e): Insulin ; chick embryo ; retina ; development ; HPLC analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Retinas of chick embryos contain insulin (1) and further, are capable of synthesizing it, as demonstrated by incubating retinas at different ages (7th–18th day) with [3H]leucine. The synthesized radioactive insulin was isolated and assayed by means of a HPLC procedure. The synthesis of insulin was found to be highest in the youngest retinas studied (day 7), afterwards it declined with age except for an increment found at 14–15 day. Explants of chick embryo retinas, cultured in vitro, rapidly degraded insulin. Nevertheless, the content of immunoreactive insulin in retinal explants diminished slowly with the age of culture, so that, after 8 days of incubation, it was about 60% of the content found in the retinas at the beginning of incubation. This was proof that cultured explants are capable of efficiently synthesizing insulin. The synthesized [3H]insulin was released from explants into the medium. This was evident also after 6–8 days in culture.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00967450
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  • 6
    Digitale Medien
    Digitale Medien
    Complex rate law for the cerium(IV) oxidation of glycolic acid in the medium HClO4-Na2SO4-NaClO4 (1983)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 15 (1983), S. 417-432 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the cerium(IV) oxidation of glycolic acid have been studied in the medium HClO4—Na2SO4—NaClO4 at varying organic substrate (HL), hydrogen, and bisulfate ion concentrations at 25.0°C and ionic strength 2.0M. Under the experimental conditions used (0.03 ≤ [H+] ≤ 0.5M; 0.02 ≤ [HSO4-] ≤ 0.1M; 0.01 ≤ [HL] ≤ 0.1M) the observed pseudo-first-order rate constant kobs has been found to follow the complex expression where the values of the various constants have been estimated by a nonlinear least-squares method. According to this expression the oxidation process occurs significantly through three simultaneous pathways. Moreover three equilibria involving cerium(IV) and HSO4- (or SO42-) ions are important from a kinetic point of view, whereas only two equilibria involving the corresponding complexes with the organic substrate are predominant.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550150503
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  • 7
    Digitale Medien
    Digitale Medien
    Substituent effects on the kinetics of the cerium(IV) oxidation of mandelic acids in sulfate media. Anomalous kinetic behavior of the methoxy derivative (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 13 (1981), S. 1029-1040 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the cerium(IV) oxidation of p-nitro and p-methoxymandelic acids have been investigated in H2SO4-MHSO4 (M+ = Li+, Na+, K+) and H2SO4-MClO4 (M+ = H+, Na+) mixtures at a constant total electrolyte concentration of 2.00 mol/dm3. The oxidation of p+nitromandelic acid proceeds through two [H+]-independent paths, as was also observed for some substituted mandelic acids studied previously. The kinetic behavior of the p-methoxy derivative differs from that of the other mandelic acids in that (1) the oxidation occurs via two [H+]-dependent paths, (2) the reaction rate is anomalously high, (3) the activation enthalpy and entropy of the overall process are markedly lower. It provides strong support to the suggestion that a different mechanism is operative. The substituent effects and the reaction mechanism are discussed.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550131004
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  • 8
    Digitale Medien
    Digitale Medien
    Kinetics of cerium (IV) oxidation of mandelic acid. Ionic strength and specific cation effects (1979)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 11 (1979), S. 415-425 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the redox reaction between mandelic acid (MA) and ceric sulfate have been studied in aqueous sulfuric acid solutions and in H2SO4—MClO4 (M+ = H+, Li+, Na+) and H2SO4—MHSO4 (M+ = Li+, Na+, K+) mixtures under various experimental conditions of total electrolyte concentration (that is, ionic strength) and temperature. The oxidation reaction has been found to occur via two paths according to the following rate law: rate = k[MA] [Ce(IV)], where k = k1 + k2/(1 + a)2[HSO4-]2 = k1 + k2/(1 + 1/a)2[SO42-]2, a being a constant. The cations considered exhibit negative specific effects upon the overall oxidation rate following the order H+ ≤ Li+ 〈 Na+ 〈 K+. The observed negative cation effects on the rate constant k1 are in the order Na+ 〈 Li+ 〈 H+, whereas the order is in reverse for k2, namely, H+ ≤ Li+ 〈 Na+. Lithium and hydrogen ions exhibit similar medium effects only when relatively small amounts of electrolytes are replaced. The type of the cation used does not affect significantly the activation parameters.
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550110407
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  • 9
    Digitale Medien
    Digitale Medien
    Cerium (IV) oxidation rate of p-chloromandelic acid in perchlorate and sulfate media (1981)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 13 (1981), S. 135-148 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The rate of the cerium (IV) oxidation of p-chloromandelic acid has been studied in perchlorate media at an ionic strength of 1.50 mol/dm3 by the stopped-flow technique and in H2SO4—MHSO4 (M+ = Li+, Na+, K+) and H2SO4—MClO4 (M+ = H+, Li+, Na+) mixtures at constant total electrolyte concentrations of 1.00 and 2.00 mol/dm3 using the conventional spectrophotometric method. In perchlorate media the kinetic data indicate the formation of two intermediate complexes between cerium (IV) and the organic substrate, but only one is significantly involved in the intramolecular electron-transfer process. The oxidation rate is markedly lower in sulfate media, where two reaction paths have been found to contribute to the overall redox reaction. The univalent cations examined exhibit negative specific effects upon the overall oxidation rate increasing in the order H+ 〈 Li+ 〈 Na+ 〈 K+. Activation parameters have been also estimated.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550130205
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  • 10
    Digitale Medien
    Digitale Medien
    Kinetics of the redox reactions between ceric sulfate and lactic and atrolactic acids in the medium HClO4-Na2SO4-NaClO4 (1984)
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 16 (1984), S. 1201-1211 
    Details
    ISSN: 0538-8066
    Schlagwort(e): Chemistry ; Physical Chemistry
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The kinetics of the oxidation of lactic and atrolactic acids by ceric sulfate have been studied in the medium HClO4-Na2SO4-NaClO4 at 25.0°C and ionic strength 2.0 mol dm-3 over a wide range of organic substrate (HL), hydrogen and bisulfate ion concentrations. The redox reactions proceed significantly through three simultaneous paths involving intermediate complexes between the reactive cerium(IV) species and the organic substrate according to the following expression \documentclass{article}\pagestyle{empty}\begin{document}$$k_{{\rm obs}} = \frac{{(b[{\rm HSO}_4^ -] + c[{\rm HSO}_4^ -]^2 + [{\rm H}^ +]){\rm [HL]}}}{{\{ f_1 [{\rm HSO}_4^ -]^3 + d_1 [{\rm HSO}_4^ -] + e_1 [{\rm HSO}_4^ -]^2){\rm }[{\rm H}^ +]\} + A'[{\rm HL}]}}$$\end{document} where kobs indicates the observed pseudo-first-order rate constant, b and c are rate constants relative to that for the path associated with the term [H+] in the numerator, and A' is a quantity depending on the [H+] and [HSO4-] concentrations. Moreover, three equilibria involving cerium(IV) and HSO4- (or SO42-) ions are important from a kinetic point of view, the cumulative equilibrium constants being in the ratios β1: β2: β3 = d1: e1: f1. The present data are compared with those obtained previously for the cerium(IV) oxidation of glycolic acid and the substituent effects discussed.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/kin.550161004
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