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. 2013 Jul 1;110(29):11881–11886. doi: 10.1073/pnas.1310571110

Fig. 5.

Fig. 5.

Muscle contraction and calcium transients. (A) Contraction of E18.5 diaphragm was elicited by electrical field stimulation (50 Hz, 1-ms pulses) and measured with a force transducer. Stimulation yielded robust tetanic contraction in normal diaphragms, but barely detectable contraction in KOs. (B) Force measurements of diaphragm with application of 120 mM KCl and 1 mM 4-CMC. Het and KO responded comparably to 4-CMC when normalized for differences in weight, but the KO tissue was unresponsive to membrane depolarization by KCl. The amplitudes of the traces in A and B were normalized to the specimen weight. (C) Cultured myotubes loaded with the fluorescent calcium indicator fluo-4-AM. The cells were perfused continuously and the calcium transients were recorded with an inverted microscope. Het cells responded synchronously to KCl application and to 4-CMC. KO myotubes were unresponsive to KCl, but responded comparably with Het with application of 4-CMC. Each fluo-4-AM trace is the mean of ∼10 myotubes within the field.