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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 83 (1961), S. 997-998 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 3 (1964), S. 1213-1220 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 405 (1985), S. 354-359 
    ISSN: 1432-2013
    Keywords: Silver ion ; Membrane depolarization ; Mechanical activation ; Mercury ion ; Sulfhydryl group
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Silver ions elicit dose-dependently a transient contracture in single fibres of bull-frog toe muscle placed in 0-Ca2+, Cl−-free MOPS solution containing 3 mM Mg2+ and NO 3 − . To elucidate the mechanisms involved, changes in membrane potential and in tension development were continuously measured following exposure to Ag+. The effect of Ag+ on contraction in fibres in which the membrane had been depolarized by elevating the external K+ concentration was also examined. The major findings of this investigation are as follows. (1) The mechanical threshold was shifted towards more negative potentials by 5 mV (−51 to −56 mV), when Ca2+ and Cl− in the Ringer's solution were replaced with Mg2+ and NO 3 − , respectively. (2) On the exposure of the fibres to 5 μM Ag+, the membrane potential decreased by 1.6 mV from −87.8 mV and tension was developed. (3) In fibres soaked in a solution containing 10 mM K+ (corresponding to a membrane potential of −69.5 mV), 5 μM Ag+ produced a large contracture similar to that seen in the control solution. (4) The Ag+-induced contracture was inactivated when more than 20 mM K+ was used. (5) The membrane depolarization evoked by either 20 or 50 μM Hg2+ did not produce contraction. (6) Muscle fibres which had been exposed to 20 μM Hg2+ for 5 min responded to 5 μM Ag+ by a transient tension development. These findings strongly suggest that Ag+-induced tension development is not associated with depolarization of the surface membrane but rather is caused by specific actions of Ag+ on membrane proteins in the T-tubules.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-2013
    Keywords: Diffraction intensity ; Ca2+ ; Tension monitoring
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The relationship between the diffraction intensity change of the first order line and tension development was examined in mechanically skinned single fibers from the dorsal head of the semitendinosus of frogs. Passive stretch of the fibers resulted in an increase in intensity over the range of sarcomere lengths from 2.5 to 3.6 μm, indicating that the intensity is a function of sarcomere length. Activation of skinned fibers caused a decrease in the intensity, at all sarcomere lengths, where the thick and thin filaments overlapped. The magnitude of the intensity decrease and that of the tension development depended on the Ca2+ concentration in the medium. The drop of intensity-pCa and the tension-pCa curves showed a similarly steep S-shape within a range of 0.5 pCa unit, although the intensity-pCa curve shifted to the left; the pCa for 50% decrease in light signal was 6.48 and that for 50% tension development was 6.40. Caffeine (25 mM) added to the medium produced a decrease in the intensity of skinned fibers with the simultaneous development of tension, thereby indicating that caffeine induces a release of Ca2+ from the sarcoplasmic reticulum and disorder in the filaments ensues. Changes in diffraction intensity with electrical stimulation to the intact single fiber were similar, although a more striking summation was observed in the optical response, as compared to the tension development. These results suggest that tension development upon stimulation can be monitored by assessing the magnitude of diffraction intensity decrease in the first order line, except for some shift in the short fiber.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 384 (1980), S. 1-7 
    ISSN: 1432-2013
    Keywords: Frequency analysis ; Master's two step exercise ; Instantaneous heart rate ; Autonomic blockade ; Cardiac control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Effects of pharmacological denervation with propranolol (0.2 mg· kg−1) and/or atropine (0.04 mg· kg−1) on the control system of heart rate during exercise were studied using a frequency domain analysis, to evaluate the cardiac control function of autonomic nervous systems in man. Propranolol decreased the gain of the system in low frequency range and increased the gain slightly in middle and high frequency ranges. The phase angle of the system was advanced over the whole frequency range observed. Atropine decreased and delayed the gain and phase angle, respectively, especially in high frequency range. The combined administration of blockades significantly decreased the gain and delayed the phase angle in the whole and high frequency ranges, respectively. These findings suggest that sympathetic and parasympathetic nervous systems act nearly independently in controlling heart rate during exercise; that they act in different manners; and that the characteristics of the systems can feasibly be used to estimate clinically the cardiac control function of autonomic nerves in man.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 37 (1959), S. 323-336 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The physical feature of the G-F transformation of action caused by a small amount of magnesium ions was investigated by measuring flow birefringence, light scattering, viscosity, and sedimentation of action solutions at various concentrations of actin and magnesium ions. All experimental results indicate that the G-F transformation of actin can be regarded as a reversible fibrous condensation. When the concentration of actin is increased at a constant concentration of magnesium ions, fibrous aggregates of actin molecules, F-actins, can be formed only above a critical actin concentration which is determined by the condition of medium and decreases rapidly with increasing concentration of magnesium ions. Above the critical concentration, all of the excess active actin molecules are transformed into F-actins. These F-actins are coexisting with active (G-)actin molecules, the concentration of which is independent of the concentration of F-actin and equal to the concentration of active actin at the critical point. The state of apparent units of F-actins in solution is also determined by the condition of medium and independent of the concentration. With increasing concentration of magnesium ions, the apparent units of F-actin become longer and longer and their thickness increases. Small globular aggregates are always observed below the critical point of formation of long fibrous aggregates. These experimental results show qualitative agreement with theoretical results obtained by one of the authors on fibrous and globular aggregations of charged macromolecules.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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