Linked Life Data

16169953

Source:http://linkedlifedata.com/resource/pubmed/id/16169953

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
Pt 19
pubmed:dateCreated
2005-9-19
pubmed:abstractText
The activation level of a muscle is presumed to be a major determinant of many mechanical and phenotypic properties of its muscle fibers. However, the relationship between the daily activation levels of a muscle and these properties has not been well defined, largely because of the lack of accurate and sustained assessments of the spontaneous activity levels of the muscle. Therefore, we determined the daily activity levels of selected rat hindlimb muscles using intramuscular EMG recordings. To allow comparisons across muscles having varying activity levels and/or muscle fiber type compositions, we recorded EMG activity in a predominantly slow plantarflexor (soleus), a predominantly fast plantarflexor (medial gastrocnemius, MG), a predominantly fast ankle dorsiflexor (tibialis anterior, TA) and a predominantly fast knee extensor (vastus lateralis, VL) in six unanesthetized rats for periods of 24 h. EMG activity levels were correlated with the light:dark cycle, with peak activity levels occurring during the dark period. The soleus was the most active and the TA the least active muscle in all rats. Daily EMG durations were highest for soleus (11-15 h), intermediate for MG (5-9 h) and VL (3-14 h) and lowest for TA (2-3 h). Daily mean EMG amplitudes and integrated EMG levels in the soleus were two- to threefold higher than in the MG and VL and seven- to eightfold higher than in the TA. Despite the three- to fourfold difference in activation levels of the MG and VL vs the TA, all three predominantly fast muscles have been reported to have a similar, very low percentage of slow fibers. Comparing these relative EMG levels to the published fiber type profiles of these muscles yields a very poor relationship between daily activity level and fiber type composition in the same muscles across several species. Although it is clear that changing the levels of activity can modulate the expression of the myosin phenotype, these results indicate that factors other than activation must play critical roles in determining and maintaining normal phenotypic properties of skeletal muscle fibers.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:status
MEDLINE
pubmed:month
Oct
pubmed:issn
0022-0949
pubmed:author
pubmed:issnType
Print
pubmed:volume
208
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
3761-70
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed:year
2005
pubmed:articleTitle
Does daily activity level determine muscle phenotype?
pubmed:affiliation
Brain Research Institute, University of California Los Angeles, 90095-1761, USA.
pubmed:publicationType
Journal Article, Comparative Study, Research Support, U.S. Gov't, P.H.S., Research Support, N.I.H., Extramural