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rdf:type |
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lifeskim:mentions |
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pubmed:dateCreated |
1987-2-17
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pubmed:abstractText |
The effect of Ca2+ upon maximum shortening velocity (Vmax) has been investigated in skinned single fibres from rabbit psoas muscles. Vmax was obtained at 15 degrees C by measuring the amounts of time (delta t) required to take up various amounts of slack (delta l) imposed at one end of the fibre. During maximal activation with Ca2+, plots of delta l vs. delta t were well fitted by a single straight line. Calculation of Vmax from the slopes of the fitted lines yielded a Vmax of 4.44 +/- 0.15 (S.E. of mean) muscle lengths per second (m.l./s). However, at lower levels of Ca2+ activation, plots of delta l vs. delta t were biphasic, containing an initial phase of steady high-velocity shortening and a subsequent phase of steady low-velocity shortening. The transition between these two phases occurred following active shortening equivalent to 60-80 nm/half-sarcomere. Vmax during the high-velocity phase was relatively insensitive to Ca2+ concentration between pCas (i.e. -log [Ca2+]) of 4.5 and 6.0; however, Vmax fell to 3.58 +/- 0.40 m.l./s at pCa 6.1 and further to 1.02 +/- 0.30 m.l./s at pCa 6.2. Vmax during the low-velocity phase decreased as Ca2+ was lowered within the entire range of pCas studied to a minimum value of 0.35 +/- 0.09 m.l./s at pCa 6.2. The degree of thin-filament activation at a particular pCa was varied by partial extraction of troponin-C, which resulted in a permanent though reversible inactivation of parts of the thin filaments. Partial extraction of troponin-C altered the plots of delta l vs. delta t obtained at pCa 4.5 to a biphasic form. In addition, Vmax during the high- and low-velocity phases of shortening was reduced at each pCa greater than 4.5. Vmax values obtained in control fibres at low Ca2+ concentrations and extracted fibres were in good agreement when generated isometric tensions were equivalent. This was the case for both the high- and low-velocity phases of shortening. Fibres were also activated in the absence of Ca2+ by partial removal of total troponin complexes. These fibres developed steady tensions less than 30% of maximum and underwent biphasic shortening, indicating that this phenomenon cannot be the result of shortening-induced dissociation of Ca2+ from troponin-C.(ABSTRACT TRUNCATED AT 400 WORDS)
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pubmed:grant |
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pubmed:commentsCorrections |
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-1079534,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-13485191,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-149254,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-302333,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-314510,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-314975,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-315465,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-4022127,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-4056736,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-4255750,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-4261616,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-4544880,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-5316143,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-533865,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-5500992,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6189421,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6215428,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6272746,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6383715,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6403557,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6460759,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6603470,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6807974,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6820231,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6823567,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6973624,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-6981684,
http://linkedlifedata.com/resource/pubmed/commentcorrection/3795099-7264969
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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 |
377
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pubmed:owner |
NLM
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pubmed:authorsComplete |
Y
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pubmed:pagination |
487-505
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pubmed:dateRevised |
2011-11-17
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pubmed:meshHeading |
pubmed-meshheading:3795099-Actin Cytoskeleton,
pubmed-meshheading:3795099-Animals,
pubmed-meshheading:3795099-Calcium,
pubmed-meshheading:3795099-Male,
pubmed-meshheading:3795099-Muscle Contraction,
pubmed-meshheading:3795099-Muscles,
pubmed-meshheading:3795099-Rabbits,
pubmed-meshheading:3795099-Sarcomeres,
pubmed-meshheading:3795099-Time Factors,
pubmed-meshheading:3795099-Troponin,
pubmed-meshheading:3795099-Troponin C
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pubmed:year |
1986
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pubmed:articleTitle |
Effects on shortening velocity of rabbit skeletal muscle due to variations in the level of thin-filament activation.
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pubmed:publicationType |
Journal Article,
In Vitro,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't
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