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Quantitative histology and MGF gene expression in rats following SSC exercise in vivo.

Baker BA; Rao KMK; Mercer RR; Geronilla KB; Kashon ML; Miller GR; Cutlip RG
Med Sci Sports Exerc 2006 Mar; 38(3):463-471
We investigated the effects of muscle length during stretch-shortening cycles (SSC) in vivo on changes in MGF gene expression and quantitative morphometry in rat skeletal muscle. Dorsiflexor muscles of male Sprague-Dawley rats were exposed to seven sets of 10 SSC at 500 degrees .s(-1). Animals were randomly assigned to a long muscle length injury group (L-inj), short muscle length injury group (S-inj), or isometric group (Iso), with recoveries examined at 6 or 48 h post-injury for each group. Following exposure, animals were euthanized, and the tissue was prepared for either histology (quantitative morphometry) or RNA isolation, followed by quantitative real-time reverse transcriptase polymerase chain reaction. mRNA levels were measured for mechano-growth factor (MGF), while 18S ribosomal RNA served as the internal reference sample. Stereological measures indicative of edema and myofiber degeneration were significantly increased in the L-inj SSC group at 48 h when compared with the S-inj or Iso group. MGF mRNA was increased transiently at 6 h in the isometric group. In contrast, MGF mRNA was increased at 48 h in the S-inj, but was not increased at either time point in the L-inj group. These data strongly indicate that exposure to SSC at longer muscle lengths result in greater morphometric indices of inflammation and degeneration than SSC conducted at a shorter muscle lengths or isometric contractions, at the same time that the adaptation to SSC was prolonged and, apparently, not resolved in the L-inj group that was manifested by the lack of up-regulation in MGF mRNA.
Histology; Laboratory-animals; Animals; Animal-studies; In-vivo-studies; Muscles; Skeletal-system; Exposure-levels; Exposure-assessment; Muscle-tissue
Publication Date
Document Type
Journal Article
Fiscal Year
Issue of Publication
NIOSH Division
Priority Area
Disease and Injury: Musculoskeletal Disorders of the Upper Extremities
Source Name
Medicine and Science in Sports and Exercise
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