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  • 1
    Electronic Resource
    Electronic Resource
    Development of force-velocity relation and rise of isometric tetanic tension measure the time course of different processes (1984)
    Springer
    Pflügers Archiv 401 (1984), S. 396-401 
    Details
    ISSN: 1432-2013
    Keywords: Muscle mechanics ; Muscle activation ; Force-velocity relation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The time course of the contractile process was investigated in the presence of AR-L 115BS, a twitch potentiator which is thought to increase the rate of the Ca2+ binding by troponin and to improve the Ca2+ mobilization from the sarcoplasmic reticulum. AR-L 115BS increased markedly the rate of development of the force-velocity (T-V) relation and of the isometric tetanic tension. The effect on the rate of development of theT-V relation was however substantially more intense than that on the speed of rise of tetanic tension, thus reducing considerably the isometric tension level at which theT-V relation attained its final characteristics. The velocity of shortening under zero load and the degree of curvature of theT-V relation were not affected by AR-L 115BS. These findings support the view that the development of theT-V relation and the rise of the isometric tetanic tension measure the time course of two different processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584342
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Sodium nitroprusside, a NO donor, modifies Ca2+ transport and mechanical properties in frog skeletal muscle (1998)
    Springer
    Journal of muscle research and cell motility 19 (1998), S. 865-876 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Recently it has been hypothesized that, in skeletal muscle, NO produced directly by high-frequency stimulation could produce contraction through reactions with thiol groups on the sarcoplasmic reticulum (SR). However, a possible cGMP-mediated relaxing effect, similar to that seen in smooth muscle, has also been demonstrated. We used purified SR preparations and single fibres from frog fast muscles incubated with different concentrations of sodium nitroprusside (SNP) in this study. The results obtained from a long low-frequency stimulation, together with those from a study on Ca2+ transport regulation, showed that the presence of NO precursor induced: an acceleration of the onset of fatigue in single fibres; a decreased vesicular Ca2+ content due to increased Ca2+ release; a shift to open status in SR Ca2+ channels; an increase in SR Ca2+ pump activity. The data presented in this paper seem to indicate that the increased NO in the muscle fibres can influence muscle activity in different ways, perhaps depending on the metabolic status of the muscle and target (filaments, sarcolemma, SR) with which the NO (or its derivatives) acts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005499606155
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    S-100ab increases Ca2+ release in purified sarcoplasmic reticulum vesicles of frog skeletal muscle (1992)
    Springer
    Journal of muscle research and cell motility 13 (1992), S. 511-515 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The S-100ab protein, a mixed isoform member of the S-100 family, stimulates Ca2+-induced Ca2+-release from sarcoplasmic reticulum vesicles purified from frog skeletal muscle cells. The effects of S-100ab appear to be specific and result from its peculiar characteristics rather than the fact that it is a calcium-binding protein. Moreover, the addition of S-100ab to the solution completely abolished the inhibition provoked when Ruthenium Red was added alone. Experiments that added labelled Ryanodine with and without S-100 indicated that the protein diminished the affinity of the alkaloid at its receptor site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01737993
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  • 4
    Electronic Resource
    Electronic Resource
    The maximum velocity of shortening during the early phases of the contraction in frog single muscle fibres (1984)
    Springer
    Journal of muscle research and cell motility 5 (1984), S. 503-513 
    Details
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The maximum velocity of shortening (V max) was determined at preset times during the development and the plateau of isometric tetani in single fibres isolated from the tibialis anterior muscle of the frog. Experiments were performed at low temperature (3.6–6° C) and at about 2.25 µm sarcomere length. The controlled velocity release method was used.V max was measured by determining the lowest velocity of release required to keep the tension at zero. Extreme care was taken in dissection and mounting of the fibres in order to make the passive series compliance very small. The value ofV max at the end of the latent period for the development of isometric tension (at 4.5° C about 10 ms after the beginning of the stimulus volley) was already the same as later during either the tension rise or at the plateau of isometric tetani. These results show that the value ofV max of intact fibres is independent of time and activation subsequent to the latent period, and suggest that the cycling rate of the crossbridges may thus attain its steady-state value just at the end of the isometric latent period.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00713257
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  • 5
    Electronic Resource
    Electronic Resource
    Cyclic nucleotides and haemoglobin concentration in rabbit bone marrow cell suspensions stimulated by purified erythropoietin (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Cell Biochemistry and Function 2 (1984), S. 119-124 
    Details
    ISSN: 0263-6484
    Keywords: Bones ; bone marrow ; cAMP ; cGMP ; erythropoietin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: This study was conducted to determine the possible correlations between cyclic nucleotides cyclic adenosine monophosphate (cAMP) and cyclic guanine monophosphate (cGMP), and haemoglobin (Hb) concentration in nucleated cell suspensions of rabbit bone marrow incubated with erythropoietin (Ep). The levels of cAMP and cGMP were measured following the addition of different Ep concentrations to the suspensions. The Hb concentration was also measured in suspensions treated with Ep, dibutyryl cAMP (db-cAMP) or dibutyryl cGMP (db-cGMP), respectively. The following results were obtained: (1) upon the addition of 1 IU ml-1 Ep, an increase of cAMP levels was related to an increase in Hb concentration; while a decrease of Hb concentration was related to an increase of cGMP levels obtained when 0.1 IU ml-1 Ep was present in the incubation mixture. (2) A mimetic effect on Hb concentration was obtained upon the addition of db-cAMP or db-cGMP to the suspensions. (3) A quantitative correlation was found between the cAMP/cGMP ratio and Hb levels in cellular suspensions. This rapport was reviewed with respect to the controls as a decrease in Hb concentration when the ratio is less than one and an increase in Hb concentration when the ratio is greater than one.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cbf.290020213
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    Paper (German National Licenses)
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