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  • 1
    Electronic Resource
    Electronic Resource
    Release of norepinephrine from brain vesicular preparations: Effects of an adenylate cyclase activator, forskolin, and a phosphodiesterase inhibitor (1982)
    Springer
    Cellular and molecular neurobiology 2 (1982), S. 179-192 
    Details
    ISSN: 1573-6830
    Keywords: adenylate cyclase ; catecholamines ; adrenergic receptors ; cyclic AMP ; phosphodiesterase ; neurotransmission ; calcium ; brain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The calcium-dependent K+-evoked release of [3H]norepinephrine from guinea pig cerebral cortical vesicular preparations is inhibited by norepinephrine, clonidine, and epinephrine. Isoproterenol has no effect and phentolamine prevents the inhibition by norepinephrine. The results indicate that anα-adrenergic receptor mediates an inhibitory input to the calcium-dependent release process. The inhibition by norepinephrine is prevented by high concentrations (3.0 mM) of calcium ions. 2. A cyclic AMP phosphodiesterase inhibitor, ZK 62771, slightly elevates [3H]cyclic AMP levels in the guinea pig cerebral cortical preparation and potentiates the marked elevation of [3H]cyclic AMP elicited by the adenylate cyclase activator, forskolin. 3. Neither ZK 62771 nor forskolin alone has significant effects on K+-evoked release of [3H]norepinephrine from the cerebral cortical vesicular preparation; however, a combination of ZK 62771 and forskolin inhibits K+-evoked release by as much as 60%. The inhibition is reversed by high concentrations (2.0 mM) of calcium ions. The results suggest that a marked accumulation of cyclic AMP elicited via both activation of adenylate cyclase and inhibition of phosphodiesterase can be inhibitory to neurotransmitter release from central synaptic terminals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711146
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  • 2
    Electronic Resource
    Electronic Resource
    Release of norepinephrine and dopamine from brain vesicular preparations: Effects of adenosine analogues (1982)
    Springer
    Cellular and molecular neurobiology 2 (1982), S. 193-204 
    Details
    ISSN: 1573-6830
    Keywords: adenosine ; catecholamines ; neurotransmission ; calcium ; brain ; striatum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. Adenosine analogues inhibit calcium-dependent K+-evoked release of [3H]norepinephrine from guinea pig cerebral cortical and hippocampal vesicular preparations. Inhibition requires high concentrations (100µM) of the adenosine analogues and is abolished in the presence of high concentrations (2 mM) of calcium ions. The inhibitory effect of 2-chloroadenosine is blocked by theophylline. The structure activity profile (N 6-d-phenylisopropyladenosine ≥N 6-l-phenylisopropyladenosine ≥ 2-chloroadenosine 〉N 6-cyclohexyladenosine, adenosine 5′-cyclopropylcar-boxamide) is not that expected of either A1 (high-affinity) or A2 (low-affinity) adenosine receptors. 2. Calcium-dependent K+-evoked release of [3H]dopamine from guinea pig striatal vesicular preparations is inhibited by apomorphine. However, only 2-chloroadenoine causes an inhibition of K+-evoked release of [3H]dopamine. Other adenosine analogues such asd- andl-phenylisopropyladenosine and adenosine 5′-cyclopropylcar-boxamide cause a facilitation of K+-evoked release. The facilitation is abolished or reduced in the presence of high concentrations (2 mM) of calcium ions. The sites of action of adenosine analogues do not appear to have structural requirements identical to those expected of A1 (high-affinity) or A2 (low-affinity) adenosine receptors. 3. The results indicate that adenosine analogues can have either inhibitory or facilitory effects on K+-evoked release of catecholamines from central synaptic terminals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711147
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  • 3
    Electronic Resource
    Electronic Resource
    Release of norepinephrine and dopamine from brain vesicular preparations: Effects of calcium antagonists (1982)
    Springer
    Cellular and molecular neurobiology 2 (1982), S. 205-213 
    Details
    ISSN: 1573-6830
    Keywords: calcium ; catecholamines ; neurotransmission ; brain ; striatum ; calcium antagonists
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The calcium antagonists D-600 (1–10µM) and diltiazem (10–25µM) inhibit K+-evoked release of [3H]norepinephrine from guinea pig cerebral cortical vesicular preparations. The inhibition of release is partially reversed by increasing concentrations of calcium to 2 mM. Diltiazem at 100µM has no effect on K+-evoked release of [3H]norepinephrine at 0.15 mM calcium but does inhibit release at 2.0 mM calcium. 2. The calcium antagonist nifedipine and dantrolene, an agent purported to antagonize release of calcium from intracellular storage sites, have no effect on K+-evoked release of [3H]norepinephrine. 3. The calcium antagonists D-600 (1µM) and diltiazem (10µM) inhibit K+-evoked release of [3H]dopamine from guinea pig striatal vesicular preparations. Higher concentrations of drug, namely, 10µM for D-600 and 100µM for diltiazem, cause a potentiation rather than an inhibition of K+-evoked release. The potentiation is reduced in magnitude upon raising the extracellular calcium to 2.0 mM. Indeed, 10µM D-600 then inhibits K+-evoked release of [3H]dopamine. 4. The results indicate that putative calcium antagonists can have both inhibitory and facilitory effects on calcium-dependent K+-evoked release of catecholamines from central synaptic endings. Furthermore, certain peripheral calcium antagonists such as nifedipine and dantrolene may prove ineffective in central systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00711148
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  • 4
    Electronic Resource
    Electronic Resource
    Some effects of cocatalyst structure on the anionic polymerization of ε-caprolactam (1964)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 1363-1369 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: N-Acetyl, N-butyryl, N-stearyl, N-benzoyl, N-4-methoxybenzoyl, and N-4-nitrobenzoyl caprolactams were prepared and used as cocatalysts for the anionic polymerization of caprolactam. The results of these studies indicate that all of the cocatalysts used, except N-acetylcaprolactam, exert a steric effect which lowers both the rate and degree of polymerization. The N-benzoyl derivative appeared to be a slightly better cocatalyst than the N-4-methoxybenzoyl derivative. This may be due to the fact that the N-benzoyl group is the more electron-attracting group. N-4-Nitrobenzoylcaprolactam was unstable under the reaction conditions employed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1964.070080326
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  • 5
    Electronic Resource
    Electronic Resource
    Some effects of cocatalyst structure on the anionic polymerization of ∊-caprolactam. II.From the theses of R. P. Scelia and S. E. Schonfeld which were submitted in partial fulfillment of the requirements for the degree of Master of Science. (1967)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 11 (1967), S. 1299-1313 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A study of the effect of catalyst (base) concentration and N-acylcaprolactam cocatalyst size and substitution on the fast anionic polymerization of caprolactam indicated that a steric effect due to cocatalyst size exists, and perhaps an electronic effect due to cocatalyst substitution was noted. The rate of polymerization, degree of polymerization, and yield of polymer are related to these effects. It was also noted that at high base concentrations, the rate and degree of polymerization along with the product yields all decrease. These latter observations suggest that reinterpretation of some of the reaction mechanism data may be important if polymer degradation is not an appreciable factor during the reaction.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1967.070110726
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  • 6
    Electronic Resource
    Electronic Resource
    Transport of liquids in structurally modified polyethylene (1964)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 8 (1964), S. 897-933 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Cast linear polyethylene films subjected to dry and solvent annealing display markedly different sorption and difusion barrier properties than do untreated films. The subsequent sorption of liquid o- and p-xylene and cis- and trans-acetylene dichloride per unit volume of amorphous polymer increases as the annealing temperature and/or treating solvent concentration increases. Integral diffusivities calculated from sorption and steady-state permeation rates show a monotonic increase with sorption per unit volume of amorphous polymer. The concentration dependence, however, is less marked than observed in similar systems at low permeant activity. Apparently the above treatment reduces the effective crosslinking imposed by the crystallites on the amorphous polymer chains through disentangling and incorporating some of these chains into crystallites. Thus the polymer is capable of a greater degree of swelling when brought into contact with a compatible liquid in a spite of a higher degree of crystallinity. The low concentration dependence of the diffusivities is probably due to heterogeneous distribution of excess permeant in a treated film. If the excess permeant were preferentially sorbed in regions of low polymer concentration then the above observations could be explained. Long-duration, osmotic stress-induced swelling and recrystallization have been cited to account for time-dependent permeation rates in treated and untreated films.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1964.070080229
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  • 7
    Electronic Resource
    Electronic Resource
    Craze growth and healing in polystyrene (1987)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 25 (1987), S. 2541-2560 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of craze growth and craze healing were studied by dark-field optical microscopy in monodisperse molecular weight polystyrene (PS) that varied in molecular weight from 88,000 to 1,334,000. The following observations were made. (1) G1 the virgin growth rate, decreased rapidly with increasing molecular weight until Mn ∼ 200,000 and then remained constant. (2) G1 decreased with increasing craze density. (3) The growth rates of approaching craze tips decreased when the craze tips overlapped, and the effect was less for crazes whose parallel growth paths were greater than 40 μm apart. (4) Complete craze healing was observed by comparison of the nucleation times, τ2, and growth rates, G2, of healed individual crazes with the craze kinetics of the virgin sample. (5) The extent of healing was characterized using four cases in which τ and G were measured as a function of healing time, temperature, constant stress, and molecular weight. (6) Craze healing times were found to increase with molecular weight and were analyzed in terms of the modified molecular weight of the craze zone. (7) Significant bond rupture was determined to occur during crazing by comparison of healing times with stress relaxation and diffusion data. (8) Craze healing studies provide insight into both crack healing and fracture of glassy polymers.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1987.090251209
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  • 8
    Electronic Resource
    Electronic Resource
    Preconcentration and determination of lead(II) at crown ether and cryptand containing chemically modified electrodes (1989)
    Weinheim : Wiley-Blackwell
    Electroanalysis 1 (1989), S. 13-21 
    Details
    ISSN: 1040-0397
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemically modified electrodes (CMEs) containing incorporated crown ether and cryptand ligands as modifiers were evaluated for their ability to preconcentrate metal cations prior to quantitation by conventional voltammetric methods. Stable CMEs were formed for 18-crown-6, dibenzo-18-crown-6, poly(dibenzo-18-crown-6), dibenzo-24-crown-8, and 2.2.2-cryptand by mixing the desired amount of the ligand into carbon paste. The resulting electrodes exhibited complexing capabilities that were similar to those of the free ligands. In particular, the CMEs were very reactive toward Pb2+ and Hg2+. Pb2+ uptake was sufficiently strong that a detection limit of 1 μM was obtained following a 20-sec exposure to the sample and transfer to a blank electrolysis solution for differential pulse voltammetric analysis. Accurate quantitation of micromolar levels of Pb in water and urine reference standards was achieved at the CMEs by means of a simple procedure requiring minimal sample preparation. Finally, the analytical characteristics of CME preconcentration were directly compared to those of the electrodeposition approach ordinarily employed in stripping voltammetry.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140010104
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  • 9
    Electronic Resource
    Electronic Resource
    Electrochemical characterization of aminated PVC-based ion-selective membranesDedicated to the memory of Prof. Wilhelm Simon. (1993)
    Weinheim : Wiley-Blackwell
    Electroanalysis 5 (1993), S. 725-730 
    Details
    ISSN: 1040-0397
    Keywords: Ion selective electrodes ; pH sensors ; aminated PVC ; impedance measurements ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The potentiometric and impedance characteristics of a large number of pH sensitive, piperazine-based aminated PVC membranes are summarized. The main goal of the work was to predict the differences between “good” and “bad” responsive potentiometric pH membranes with very similar overall nitrogen contents. The only conclusion gained previously from other methods was that the N content should be between 0.5 and 0.8% for Nernstian response. The detailed analysis of the data show that a given N content of the basic material is a necessary but not a sufficient requirement with respect of the quality of potentiometric response. Conditions for appropriate pH response of the membrane are formulated in terms of surface and bulk impedance characteristics. The ideal pH response of an optimized aminated PVC membrane, which corresponds to a minimum surface impedance, is presented. The primary importance of surface amines relative to bulk amines (the conformation and distribution of active sites) is proven in a simple experiment.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140050904
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of copper-based electrodes for the analysis of aminoglycoside antibiotics by CE-EC (1997)
    Weinheim : Wiley-Blackwell
    Electroanalysis 9 (1997), S. 1145-1151 
    Details
    ISSN: 1040-0397
    Keywords: Copper electrode ; Antibiotics ; Capillary electrophoresis ; Aminoglycosides ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aminoglycoside antibiotics including gentamicin, bekanamycin, tobramycin, lincomycin, neomycin, kanamycin, and ribostamycin have been determined by CE-EC with copper clectrodes. Both copper wall-jet electrodes (WJEs) and copper on-capillary electrodes (OCEs) were evaluated. The OCEs provided μM detection limits, superior stability and reproducibility (2-3% relative standard deviation in oxidation current), and a simple instrumental set-up without the need for capillary/electrode alignment. The analytical capabilities of the Cu-OCE were examined, following the optimization of CE conditions, for the seven aminoglycosides above; and the practical utility of this approach was demonstrated through the determination of aminoglycoside antibiotics in three pharmaceutical preparations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elan.1140091502
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