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The capacity of mdx mouse diaphragm muscle to do oscillatory work
Author(s) -
Stevens E. Don,
Faulkner J. A.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.t01-3-00457.x
Subject(s) - mdx mouse , isometric exercise , duchenne muscular dystrophy , diaphragm (acoustics) , diaphragm muscle , dystrophin , anatomy , muscle contraction , muscular dystrophy , chemistry , medicine , biology , physics , weakness , acoustics , loudspeaker
Mdx mice were used as a model for Duchenne muscular dystrophy; both lack dystrophin. It was hypothesized that the mdx condition would have a marked effect on the ability of diaphragm muscle from mdx mice to do active net work and generate power. This hypothesis was tested using the work‐loop technique. Specific twitch force, specific tetanic force and maximum power were all significantly less in diaphragm strips from mdx mice than those from control mice. In all preparations muscle length at which maximum power was achieved ( L w ) was about 8% less than that at which maximum tetanic force was achieved ( L 0 ), both in mdx and control muscle. The isometric force‐length curve for mdx muscle was steeper on both sides of the plateau. Similarly, the curve relating net work per cycle to muscle length was steeper for mdx muscle on both sides of the plateau. Maximum power of mdx muscle was achieved at a lower strain than for control muscle; maximum power occurred at a strain of 10.2% for mdx and 14.7% for control. Further increases in strain caused a marked decrease of power production in mdx muscle, whereas they caused a smaller decrease in control muscle. In summary, at muscle lengths longer than L w and at high strains, performance of mdx muscle was compromised relative to that of control muscle. Work and power were compromised more than isometric force.