alpha-Actin: disposition, quantities, and estimated effects on lung recoil and compliance.

We have investigated the basis and implications of pneumoconstriction by measuring disposition and quantities of alpha-smooth muscle actin in rat and guinea pig lungs and modeling its effects on lung recoil and compliance. A robust marker of contractility, alpha-smooth muscle actin appears in smooth muscle or myofibroblast-like cells in pleura, airways, blood vessels, and alveolar ductal tissues. In each site, we measured its transected area by immunofluorescent staining and frequency-modulated scanning confocal microscopy.

Maximal inspiratory pressures and dimensions of the diaphragm.

We postulated that the variation of maximal voluntary inspiratory pressures (PI,max and Pdi,max) among individuals largely reflects the variation of the structural attributes of the inspiratory muscles, in particular the muscular cross-sectional area of the diaphragm (CSAdi) and its axially projected area (A(thor)). To test this postulate, we measured PI,max in 36 healthy subjects, including 3 children and 15 weight-lifters, and Pdi,max in 11 subjects. Structural measurements by ultrasonography and anthropometric calipers were available as reported in the companion manuscript.