Figure 4.

Effect of ventilation or mechanical stretch on Ca²⁺- and Sr²⁺-activation profiles of diaphragm fibers at 127 days gestation. (A) Representative data where fibers were obtained either immediately after delivery of the fetus (127 dGA), or after 2.5 h of mechanical ventilation (see Methods for details). Ventilation induces a small change in the lower part of force–pSr curve. (B) Representative data for Ca²⁺- and Sr²⁺-activation profiles in a fiber from a 127-day gestation fetus where the fiber was studied before (sarcomere length = 2.27 μm) and after (sarcomere length = 2.75 μm) mechanical stretch, in vitro. Stretch induces a modest change in the lower portion of the force–pSr curve.