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  • 1
    Electronic Resource
    Electronic Resource
    A myosin phosphatase modulates contractility in skinned smooth muscle (1987)
    Springer
    Pflügers Archiv 410 (1987), S. 304-312 
    Details
    ISSN: 1432-2013
    Keywords: Myosin phosphatase ; Smooth muscle ; Skinned fibers ; Ca2+ and contractility ; Myosin light chain phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The influence of a purified holoenzyme form of polycation-modulable (PCM-) myosin phosphatase on Ca2+-dependent actin-myosin interactions was studied in detergent-skinned smooth muscle fibers from chicken gizzard. The concentration of Ca2+ required for half maximal isometric contraction (A0.5; 0.26 μM) of fibers incubated in the absence of phosphatase was increased 2-fold when PCM-phosphatase (13 U/ml) was included in the medium. Removal of the phosphatase restored A0.5 to control level showing that the enzyme-mediated decrease in Ca2+-sensitivity was reversible. Two-dimensional electrophoresis of fiber homogenates revealed that PCM-phosphatase decreased Ca2+-sensitivity for phosphorylation of the regulatory myosin light chains in parallel fashion. Ca2+-dependent increases in isometric force were directly correlated to increases in the extent of light chain phosphorylation up to about 0.35 mol PO4/mol light chain; further increases in phosphorylation were not associated with further increases in force. Addition of PCM-phosphatase to fibers which had been contracted with a suboptimal concentration of Ca2+ (0.35 μM) resulted in rapid relaxation. Unloaded shortening velocity, reflecting cross-bridge cycling rate, was reduced by 92% in the presence of PCM-phosphatase and light chain phosphorylation was decreased by 50%. These data show that both tension and unloaded shortening velocity may be related to Ca2+-dependent phosphorylation of the light chains. The results indicate that the level of phosphorylation attained in the fiber preparations studied probably reflects the ratio of myosin kinase to phosphatase activities. Since protein phosphatases are regulated enzymes the results also suggest that modulation of phosphatase activity may participate in control of smooth muscle contractility.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00580281
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  • 2
    Electronic Resource
    Electronic Resource
    cGMP and cAMP inhibit tension development in skinned coronary arteries (1984)
    Springer
    Pflügers Archiv 401 (1984), S. 277-280 
    Details
    ISSN: 1432-2013
    Keywords: cGMP ; cAMP ; Skinned coronary arteries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of physiological concentrations of cGMP and cAMP on tension development in skinned coronary arteries (Triton X-100) were studied. cGMP inhibited tension elicited at intermediate Ca2+ concentrations at pH 7.0 but not at more acidic or alkaline pH values. cAMP, on the other hand, decreased submaximal tension development independent of pH (from pH 6.5 to pH 7.2). Neither nucleotide affected tension development at maximally activating Ca2+ concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582596
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  • 3
    Electronic Resource
    Electronic Resource
    Two-dimensional electrophoretic analysis of myosin light chain phosphorylation in heart (1983)
    Weinheim : Wiley-Blackwell
    Electrophoresis 4 (1983), S. 138-142 
    Details
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The phosphorylatable light chain of myosin (P-light chain) from hearts of the turtle, rat, frog, dog, cat, adult chicken and 1 week old chick was compared by two dimensional gel electrophoresis. The technique separates the phospho and dephospho forms of P-light chain and allows quantitation of its percentage distribution. The P-light chain was found to exist in multiple forms. The turtle heart possessed the highest percentage, 75%, of the phospho form of P-light chain, whereas 25% of P-light chain was in the dephospho form. In rat heart, 35% of the P-light chain was phosphorylated and 65% dephosphorylated. In frog heart, the P-light chain exhibited three forms: two phosphorylated and one dephosphorylated. The P-light chain of dog, cat and adult chicken hearts displayed four spots on two-dimensional gel electrophoresis: two phospho and two dephospho forms. In these species the percentage of total P-light chain being in the phospho forms was in the range of 10-25%. Comparison of adult chicken and 1 week old chick preparations suggests that during maturation from the chick to the chicken the percentage phospho form of the total P-light chain decreases. The myosin light chain kinase and phosphatase activities in whole homogenates of the above heart preparations were assayed. The data, with the exception of those from frog heart, suggest that the extent of light chain phosphorylation is correlated with the ratio of light chain kinase to phosphatase activity.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/elps.1150040207
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  • 4
    Electronic Resource
    Electronic Resource
    Interaction during fibril formation of soluble collagen with cartilage proteinpolysaccharide (1966)
    New York : Wiley-Blackwell
    Biopolymers 4 (1966), S. 247-258 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Precipitation of soluble forms of collagen from solutions containing the soluble protein-polysaccharide (PP-L) of bovine nasal cartilage, followed by centrifugation at 100,000 g, resulted in the formation of coherent elastic pellets whose wet weights increased with the concentration of PP-L in the initial solution. Dry weights and uronic acid contents of these pellets showed that the amount of water held in the wet pellet was nearly constant for any one kind and concentration of collagen, and ranged from 20 to 100 mg./mg. PP-L in the pellet. Soluble collagens from four different sources and PP-L from three kinds of cartilage showed similar effects. Precipitation of soluble collagen in the presence of hyaluronate or dextran yielded pellets of much smaller size than those formed in the presence of PP-L. The presence of chondroitin sulfate had only a slight effect on wet pellet weights. Wet weights of pellets formed in the presence of PP-L decreased with increasing ionic strength. A model involving entanglement between insoluble collagen fibrils and the relatively stiff chondroitin sulfate chains of branched PP-L seems qualitatively capable of accounting for these results.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1966.360040302
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    Paper (German National Licenses)
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