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rdf:type |
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lifeskim:mentions |
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pubmed:dateCreated |
1982-2-12
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pubmed:abstractText |
1. The amplitude and time course of K contractures (Cl- constant) of single twitch muscle fibres of the frog have been analysed in three external Ca2+ concentrations. 2. The resting potential, effective resistance, threshold for the Na current and K-induced depolarizations were not modified by replacing 1.8 mM-Ca2+ by 3 mM-Mg2+ in absence (low-Ca saline: 3-6 micro M-Ca2+) or in the presence of 5 mM-EGTA (Ca-free saline: less than or equal to 10(-9) M-Ca2+). 3. The tension development during the initial phase of K contractures was independent of external Ca2+ while the amplitude, the duration and the time constant of spontaneous relaxation decreased progressively as Ca2+ concentration was diminished. 4. When the concentration of Mg2+ was increased to 5 mM in Ca-free saline K contractures were slower and smaller than those in 3 mM-Mg2+. 5. In Ca-free saline the activation curve (peak tension vs. logarithm of external K+ concentration) shifted by 3-5 mV towards more positive potentials while the inactivation curve (peak tension of the test contracture vs. logarithm of external K+ concentration during the conditioning period) shifted by 16-18 mV towards more negative potentials. Both curves became steeper in Ca-free saline. 6. The effects of external Ca2+ reduction were not modified by replacing all chloride for methanesulphonate. 7. Direct effects of external Ca2+ on excitation-contraction coupling during K contractures could involve the inward Ca current and/or specific interactions between external Ca2+ ions and the coupling mechanism.
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-1082500,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-1082507,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-1082509,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-11476,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-13441,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-13714849,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-14067951,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-14402240,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-14946715,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-201723,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-20641,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-238230,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-301266,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-306438,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-306440,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-309941,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-313438,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-316821,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-356157,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-38332,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-4537984,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-4540479,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-4577,
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http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-769656,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-809063,
http://linkedlifedata.com/resource/pubmed/commentcorrection/6975818-978518
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pubmed:language |
eng
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pubmed:journal |
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pubmed:citationSubset |
IM
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pubmed:chemical |
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pubmed:status |
MEDLINE
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pubmed:month |
Aug
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pubmed:issn |
0022-3751
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pubmed:author |
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pubmed:issnType |
Print
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pubmed:volume |
317
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
303-16
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pubmed:dateRevised |
2009-11-18
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pubmed:meshHeading |
pubmed-meshheading:6975818-Animals,
pubmed-meshheading:6975818-Calcium,
pubmed-meshheading:6975818-Kinetics,
pubmed-meshheading:6975818-Magnesium,
pubmed-meshheading:6975818-Membrane Potentials,
pubmed-meshheading:6975818-Muscle Contraction,
pubmed-meshheading:6975818-Muscles,
pubmed-meshheading:6975818-Potassium,
pubmed-meshheading:6975818-Rana pipiens,
pubmed-meshheading:6975818-Rana temporaria,
pubmed-meshheading:6975818-Time Factors
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pubmed:year |
1981
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pubmed:articleTitle |
Effects of external calcium reduction on the kinetics of potassium contractures in frog twitch muscle fibres.
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pubmed:publicationType |
Journal Article,
In Vitro,
Research Support, Non-U.S. Gov't
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