title: Changes in expiratory muscle function following spinal cord section.
abstract: Following spinal cord injury, muscles below the level of injury develop variable degrees of disuse atrophy. The present study assessed the physiological changes of the expiratory muscles in a cat model of spinal cord injury. Muscle fiber typing, cross-sectional area, muscle weight, and changes in pressure-generating capacity were assessed in five cats spinalized at the T(6) level. Airway pressure (P)-generating capacity was monitored during lower thoracic spinal cord stimulation before and 6 mo after spinalization. These parameters were also assessed in five acute animals, which served as controls. In spinalized animals, P fell from 41 +/- l to 28 +/- 3 cm H2O (means +/- SE; P < 0.001). Muscle weight of the external oblique, internal oblique, transversus abdominis, and internal intercostal muscles decreased significantly (P < 0.05 for each). Muscle weight of the external oblique, internal oblique, transversus abdominis, and internal intercostal, but not rectus abdominis (RA), correlated linearly with P (r > 0.7 for each; P < 0.05 for each). Mean muscle fiber cross-sectional area of these muscles was significantly smaller (P < 0.05 for each; except RA) and also correlated linearly with P (r > 0.55 for each; P < 0.05 for each, except RA). In spinalized animals, the expiratory muscles demonstrated a significant increase in the population of fast muscle fibers. These results indicate that, following spinalization, 1) the expiratory muscles undergo significant atrophy and fiber-type transformation and 2) the P-generating capacity of the expiratory muscles falls significantly secondary to reductions in muscle mass.
authors.affiliation: Dept. of Physiology and Biophysics, Case Western Reserve Univ., MetroHealth Medical Center, Rammelkamp Center for Education & Research, 2500 MetroHealth Dr., Cleveland, OH 44109-1998. afd3@cwru.edu).
authors.forename: Krzysztof E
authors.initials: KE
authors.lastname: Kowalski
authors.forename: Jaroslaw R
authors.initials: JR
authors.lastname: Romaniuk
authors.forename: Anthony F
authors.initials: AF
authors.lastname: DiMarco
mesh_terms: D000009:Abdominal Muscles / Q000294:innervation* / Q000503:physiopathology*; D000222:Adaptation, Physiological; D000818:Animals; D002415:Cats; D003964:Diaphragm; D045853:Exhalation; D007366:Intercostal Muscles / Q000294:innervation* / Q000503:physiopathology*; D009119:Muscle Contraction; D013119:Spinal Cord Injuries / Q000503:physiopathology*