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  • Polymer and Materials Science  (40)
  • Excitation-contraction coupling  (4)
  • 1
    ISSN: 1432-136X
    Keywords: Aequorin ; Calcium ; Sarcoplasmic reticulum ; Contraction ; Excitation-contraction coupling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Steps involved in excitation-contraction coupling in mammalian myocardium have been derived using a relatively limited number of animal species. However, the use of animal models for investigations into excitation-contraction coupling in normal and disease states has encompassed a wide range of animal species. We addressed the question as to whether excitation-contraction coupling as currently understood applies to intracellular calcium handling in myocardium from multiple mammalian species, amphibian, and avian myocardium. The bioluminescent calcium indicator aequorin was used to record intracellular calcium transients in both ventricular and atrial tissue. We report that in all mammalian and avian species studied the calcium transient recorded in both ventricular and atrial myocardium is monophasic and reflects calcium release and re-uptake by the sarcoplasmic reticulum. In contrast, the Ca2+ transient recorded from salamander myocardium is prolonged relative to mammalian and avian myocardium, and appears to reflect in part trans-sarcolemmal calcium entry. Only in diseased myocardium derived from human and swine myocardium was a second component detected in the calcium transient. These data indicate that sarcoplasmic reticulum calcium handling is pivotal in excitation-contraction coupling for multiple species with differing physiologies. Also, in disease states, intracellular calcium handling is often affected with resultant alterations in the time-course and/or configuration of the calcium transient.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0935-9648
    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
    Additional Material: 6 Ill.
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  • 3
    ISSN: 0935-9648
    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
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1042-7147
    Keywords: emulsion ; copolymerization ; tribromophenyl maleimide ; styrene ; 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
    Notes: Emulsion copolymerization of Tribromophenyl Maleimide (TBPMI) and styrene was conducted by semi-batch and batch processes. The effects of monomer composition and copolymerization method on copolymerization rate, molecular weight and molecular weight distribution, latex particle size and size distribution, glass transition temperature (Tg), thermal stability and mechanical properties were investigated. A kinetic study has shown that the rate of copolymerization in the batch process increased with increasing TBPMI content in the monomer feed. For the semi-batch polymerized samples, molecular weight decreased and molecular weight distribution increased with increasing TBPMI content in the monomer feed. For the batch polymerized samples, molecular weight also decreased but no obvious tendency was observed for the molecular weight distribution when TBPMI content increased. Compared with the batch copolymers, the semi-batch copolymers have a higher molecular weight at the same initial monomer mixture composition. Latex particle size decreased, while particle size distribution slightly increased with increasing TBPMI content in both semi-batch and batch latices. The semi-batch samples exhibit only a single Tg, the value of which increses linearly with increasing TBPMI content. For the batch copolymers, two Tgs were found, reflecting a mixture of styrene-rich and TBPMI-rich copolymer chains. TGA results indicate that the thermal stability of the semi-batch copolymers increased with increasing TBPMI concentration. Young's and flexural moduli increased, while tensile and flexural strengths decreased by increasing the TBPMI content for both the semi-batch and batch specimens. The semi-batch specimens have higher tensile and flexural strenghts than the batch ones.
    Additional Material: 6 Ill.
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  • 5
    ISSN: 0721-3115
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A threshold particle velocity criteria derived by E.R. Fitzgerald for the beginning of crystal lattice breakup and disintegration has been applied to shocked explosives and an inert material. In shocked explosives, reactions leading to detonation occur above a certain “threshold” magnitude. The computed crystal lattice breakup shock pressures compare rather well with observed experimental “threshold” shock pressures for six high explosives. The six explosives are: Comp-B3, Comp-B, TNT, PBX-9404, Tetryl, and H-6.In addition, the crystal lattice breakup criteria provides an explanation for the observed lowering of the detonation “threshold” shock pressure as the explosives are made more porous or less dense.Finally, the shock pressures, at which output from thermocouples embedded in shocked materials (PBX-9404 and Plexiglass) increases dramatically, compare favorably with predictions based on crystal lattice disintegration criteria.Consequently, it is tentatively concluded that crystal lattice breakup, or self-sustained phonon fission as Fitzgerald calls it, is responsible for the initiation of detonation in shocked explosives and enhanced thermocouple output in shocked materials. It is also postulated that the lattice breakup phenomena is also responsible for phase changes, increased chemical reactivity, and anomalous electrical activity which are observed in certain inert materials under relatively low level shock loading.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 395 (1982), S. 75-77 
    ISSN: 1432-2013
    Keywords: Excitation-contraction coupling ; Cell calcium ; Vascular smooth muscle ; Reversibly hyperpermeable cells ; Calcium indicators ; Aequorin ; Phenylephrine ; Angiotensin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The bioluminescent calcium indicator aequor in was successfully loaded into vascular smooth muscle cells ofAmphiuma tridactylum by either microinjection or a new method which makes the cells reversibly hyperpermeable. Both gave similar results; however, the latter method produced larger signals. Vasoconstrictors produced a sustained contraction and a light (calcium) response consisting of two component: a large transient followed by a smaller, sustained response. Electrical stimulation produced a light transient that was much briefer than the contraction. These results suggest that tension can be maintained in smooth muscle in the presence of lower calcium levels than those present during force development.
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  • 7
    ISSN: 1432-2013
    Keywords: Excitation-contraction coupling ; Cell calcium ; Mammalian cardiac muscles ; Reversibly hyperpermeable cells ; Calcium indicators ; Aequorin ; Isoproterenol ; Caffeine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The bioluminescent calcium indicator aequorin was successfully loaded into mammalian working myocardium of ferrets by a chemical procedure which makes the cells reversibly hyperpermeable through exposure to Ethylenebis-(oxyethylenenitrilo) tetraacetic acid (EGTA). After undergoing the loading procedure, developed tension at Lmax was 103±26% of the control, which indicates that the muscles regained normal function. The configurations of the aequorin signals (i.e., calcium transients) and their responses to drugs were the same as reported after microinjection of aequorin. The peak of the Ca++ transient determined by the method of fractional luminescence at 3s intervals of stimulation, 2.5mM [Ca++]o, 22.5°C was 1.1μM; this value is similar to that reported for microinjection. These results indicate that the chemical loading procedure is a useful alternative to microinjection for loading aequorin into mammalian working myocardium.
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  • 8
    ISSN: 1432-2013
    Keywords: Excitation-contraction coupling ; Cell calcium ; Cardiac muscle ; Thyroid hormone ; Aequorin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The purpose of this study was to determine the influence of thyroid hormone on tension development and the intracellular calcium transient in mammalian ventricular muscle. A hyperthyroid (H) state was induced in ferrets by subcutaneous injection ofl-thyroxine, 0.3 mg/kg daily, for 2–3 weeks. One-half of the age matched control group (C) were injected with vehicle. Aequorin was loaded into the cells of ferret papillary muscles by a chemical procedure. The muscles were stimulated at 0.33 Hz and isometric tension and the calcium transient were simultaneously recorded at 30°C. Peak isometric tension in mN/mm2 (±SD) was 15.4±7.2 and 16.2±7.9 for C (n=8) and H (n=9) respectively. The time to peak tension and time to 80% relaxation from peak of tension were reduced by 22% and 28% respectively in H compared to C. After stimulation, the calcium transient reached a maximum in 56±6 ms in C and in 47±5 ms in H. The time to 80% decay of the peak calcium transient was 95±8 ms and 68±5 ms for C and H respectively. The ratio of the aequorin luminescence at the peak of the calcium transient over the calculated maximum luminescence,L max, were compared and they were not different. At 22°C Log (L/L max) was −3.3±0.1 in C (n=4) and −3.4±0.3 in H (n=3). These results indicate that the thyroid state influences the time course of the calcium transient and are consistent with the abbreviation in the duration of contraction that is observed in the hyperthyroid state.
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  • 9
    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: poly(N-substituted maleimide-co-styrene) copolymer films were electropolymerized onto copper substrates as possible candidates for electronic applications. The N-substituted moieties that were investigated include phenyi, 3-carboxyphenyl, and 4-carboxyphenyl. Uniform coatings of 25 μm or more thickness were successfully applied using each of the three N-substituted maleimides. The thickness was controlled by manipulating the monomer concentration, current density, and reaction time. Not only did the 3- and 4-carboxyphenylmaleimide (CMI)/styrene copolymers have high glass transition temperatures (220°C) and fairly good thermal stability (≈ 430°C), but they also have rather low dielectric constants (2.55 for 4-CMI/styrene), comparable to those of polyimides. Polymerization of the coatings was observed by in-situ Fourier transform infrared spectroscopy (FTIRS), using a special cell that made the observation of the polymer structure development possible. It was found by FTIRS that all three monomers, when used with styrene, produced alternating copolymers. © 1993 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 10
    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: 2- or 4-carboxyphenyl methacrylamide (2- or 4-CPM) was successfully electrocopolymerized with either methylmethacrylate (MMA) or N-phenylmaleimide (NPMI) to form a thick thermoplastic matrix with high glass-transition temperature (200-300°C), on Hercules AS-4 graphite fibers. The dependence of the diffusion of active species through the coating upon the solvent/water ratio in the cell was estimated from the electrochemical diffusion behavior of hexacyanoferrate (III) ions. A higher solvent/water ratio helped to increase polymer weight gain by increasing the solvent swelling and increasing the diffusion coefficient of active species. A highly solvent-swollen polymer layer promoted the rate of polymer weight gain. The copolymer composition of 4-CPM/MMA and 4-CPM/NPMI polymers was random, and the effects of variables were consistent with free-radical polymerization kinetics. The electropolymerization rates of 4-CPM/MMA and 4-CPM/NPMI were increased by increasing current density and monomer concentration. For a slight temperature increase (from 28-45°), electropolymerization rate and polymer weight gain increased dramatically for the 4-CPM/NPMI system. © 1993 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
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