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Effect of altered thyroid state on the in situ mechanical properties of adult cat soleusTo determine the responsiveness of cat hindlimb muscles to thyroid manipulation, adult female cats were made hypothyroid (thyroidectomy plus tapazole treatment), hyperthyroid (synthroid pellets), or maintained euthyroid. After 4 months, the hypothyroid soleus had slower time-to-peak (TPT, 80%) and half-relaxation (HRT) times, whereas the hyperthyroid soleus had faster TPT (20%) and HRT than euthyroid cats. The tension at low stimulation frequencies (5-15 Hz) was higher in hypothyroid and lower in hyperthyroid cats compared to euthyroid cats. Muscle weight, maximum twitch and tetanic (Po) tensions, and maximum rates of shortening (Vmax) were similar across groups. The soleus of hypothyroid cats was more fatigable than normal. The myosin heavy chain (MHC) composition, based on gel electrophoresis, was unaffected by thyroid hormone manipulation. Based on the reaction of monoclonal antibodies for specific MHCs, some fast fibers in the hypothyroid cats coexpressed developmental MHC. These data indicate that 4 months of an altered thyroid state result in changes in the isometric twitch speed properties of the cat soleus, but not the tension-related or isotonic properties. Further, a chronic decrease in thyroid hormone had a greater impact than a chronic increase in thyroid hormone on the mechanical properties of the adult cat soleus. Copyright 2003 S. Karger AG, Basel.
Document ID
20040087761
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Roy, R. R.
(Brain Research Institute, University of California Los Angeles Los Angeles, California 90095-1761, United States)
Zhong, H.
Hodgson, J. A.
Grossman, E. J.
Edgerton, V. R.
Date Acquired
August 21, 2013
Publication Date
January 1, 2003
Publication Information
Publication: Cells, tissues, organs
Volume: 173
Issue: 3
ISSN: 1422-6405
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NS16333
Distribution Limits
Public
Copyright
Other
Keywords
Non-NASA Center
NASA Discipline Musculoskeletal

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