| Myosin Head Orientation: A structural determinant for the Frank-Starling Relationship. | |
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MedLine Citation:
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PMID: 21460195 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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The cellular mechanism underlying the Frank-Starling law of the heart is myofilament length dependent activation. The mechanism(s) whereby sarcomeres detect changes in length and translate this into increased sensitivity to activating calcium has been elusive. Small angle X-ray diffraction studies have revealed that the intact myofilament lattice undergoes numerous structural changes upon an increase in sarcomere length (SL): lattice spacing (LS) decreases while the I(11)/I(10) intensity ratio and m3 meridional intensity (Im3) increases, concomitant with increases in diastolic and systolic force. Using a short (~10 ms) X-ray exposure just prior to electrical stimulation we were able to obtain detailed structural information regarding the effects of external osmotic compression (w/Mannitol), and SL on thin intact electrically stimulated isolated rat right ventricular trabeculae. We show that over the same incremental increases in SL the relative changes in systolic force track more closely to the relative changes in myosin head orientation (I(m3) ) than to the relative changes in lattice spacing. We conclude that myosin head orientation before activation determines myocardial sarcomere activation levels and that this may be the dominant mechanism for length dependent activation. |
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Authors:
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Gerrie P Farman; David Gore; Edward J Allen; Kelly Q Schoenfelt; Thomas C Irving; Pieter P de Tombe |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2011-4-1 |
Journal Detail:
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Title: American journal of physiology. Heart and circulatory physiology Volume: - ISSN: 1522-1539 ISO Abbreviation: - Publication Date: 2011 Apr |
Date Detail:
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Created Date: 2011-4-4 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 100901228 Medline TA: Am J Physiol Heart Circ Physiol Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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1University of Toronto. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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