Severe muscle dysfunction precedes collagen tissue proliferation in mdx mouse diaphragm.
After extensive necrosis, progressive diaphragm muscle weakness in the mdx mouse is thought to reflect progressive replacement of contractile tissue by fibrosis. However, little has been documented on diaphragm muscle performance at the stage at which necrosis and fibrosis are limited. Diaphragm morphometric characteristics, muscle performance, and cross-bridge (CB) properties were investigated in 6-wk-old control (C) and mdx mice. Compared with C, maximum tetanic tension and shortening velocity were 37 and 32% lower, respectively, in mdx mice (each P < 0.05). The total number of active CB per millimeter squared (13.0 +/- 1.2 vs. 18.4 +/- 1.7 x 10(9)/mm(2), P < 0.05) and the CB elementary force (8.0 +/- 0.2 vs. 9.0 +/- 0.1 pN, P < 0.01) were lower in mdx than in C. The time cycle duration was lower in mdx than in C (127 +/- 18 vs. 267 +/- 61 ms, P < 0.05). Percentages of fiber necrosis represented 2.8 +/- 0.6% of the total muscle fibers, and collagen surface area occupied 3.6 +/- 0.7% in mdx diaphragm. Our results pointed to severe muscular dysfunction in mdx mouse diaphragm, despite limited necrotic and fibrotic lesions.
Coirault
Catherine
C
Institut National de la Santé et de la Recherche Médicale, Lab d'Optique Appliquée, Ecole Nationale Supérieure de Techniques Avancées, 91761 Palaiseau, France. coirault@enstay.ensta.fr
Pignol
Bernadette
B
Cooper
Racquel N
RN
Butler-Browne
Gillian
G
Chabrier
Pierre-Etienne
PE
Lecarpentier
Yves
Y
D000465:Algorithms; D000818:Animals; D003094:Collagen / Q000378:metabolism*; D003238:Connective Tissue / Q000378:metabolism* / Q000473:pathology*; D003964:Diaphragm / Q000378:metabolism* / Q000473:pathology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007537:Isometric Contraction; D008297:Male; D051379:Mice; D018101:Mice, Inbred mdx; D009119:Muscle Contraction / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000473:pathology; D018908:Muscle Weakness / Q000235:genetics / Q000473:pathology; D009135:Muscular Diseases / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D009336:Necrosis
D003094:Collagen