| Effects of different activity and inactivity paradigms on myosin heavy chain gene expression in striated muscle. | |
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MedLine Citation:
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PMID: 11133928 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The goal of this mini-review is to summarize findings concerning the role that different models of muscular activity and inactivity play in altering gene expression of the myosin heavy chain (MHC) family of motor proteins in mammalian cardiac and skeletal muscle. This was done in the context of examining parallel findings concerning the role that thyroid hormone (T(3), 3,5,3'-triiodothyronine) plays in MHC expression. Findings show that both cardiac and skeletal muscles of experimental animals are initially undifferentiated at birth and then undergo a marked level of growth and differentiation in attaining the adult MHC phenotype in a T(3)/activity level-dependent fashion. Cardiac MHC expression in small mammals is highly sensitive to thyroid deficiency, diabetes, energy deprivation, and hypertension; each of these interventions induces upregulation of the beta-MHC isoform, which functions to economize circulatory function in the face of altered energy demand. In skeletal muscle, hyperthyroidism, as well as interventions that unload or reduce the weight-bearing activity of the muscle, causes slow to fast MHC conversions. Fast to slow conversions, however, are seen under hypothyroidism or when the muscles either become chronically overloaded or subjected to intermittent loading as occurs during resistance training and endurance exercise. The regulation of MHC gene expression by T(3) or mechanical stimuli appears to be strongly regulated by transcriptional events, based on recent findings on transgenic models and animals transfected with promoter-reporter constructs. However, the mechanisms by which T(3) and mechanical stimuli exert their control on transcriptional processes appear to be different. Additional findings show that individual skeletal muscle fibers have the genetic machinery to express simultaneously all of the adult MHCs, e.g., slow type I and fast IIa, IIx, and IIb, in unique combinations under certain experimental conditions. This degree of heterogeneity among the individual fibers would ensure a large functional diversity in performing complex movement patterns. Future studies must now focus on 1) the signaling pathways and the underlying mechanisms governing the transcriptional/translational machinery that control this marked degree of plasticity and 2) the morphological organization and functional implications of the muscle fiber's capacity to express such a diversity of motor proteins. |
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Authors:
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K M Baldwin; F Haddad |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.; Review |
Journal Detail:
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Title: Journal of applied physiology (Bethesda, Md. : 1985) Volume: 90 ISSN: 8750-7587 ISO Abbreviation: J. Appl. Physiol. Publication Date: 2001 Jan |
Date Detail:
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Created Date: 2001-01-16 Completed Date: 2001-03-29 Revised Date: 2007-11-14 |
Medline Journal Info:
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Nlm Unique ID: 8502536 Medline TA: J Appl Physiol Country: UNITED STATES |
Other Details:
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Languages: eng Pagination: 345-57 Citation Subset: IM; S |
Affiliation:
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Department of Physiology and Biophysics, University of California, Irvine, California 92697, USA. kmbaldwi@uci.edu |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Gene Expression Humans Muscle, Skeletal / physiology* Muscle, Smooth / physiology* Myosin Heavy Chains / genetics* Papillary Muscles / physiology* Thyroid Gland / physiology Weight Lifting / physiology |
| Grant Support | |
ID/Acronym/Agency:
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AR-30346/AR/NIAMS NIH HHS; HL-38819/HL/NHLBI NIH HHS |
| Chemical | |
Reg. No./Substance:
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0/Myosin Heavy Chains |
| Investigator | |
Investigator/Affiliation:
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K M Baldwin / U CA, Irvine |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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