Figure 2.

Tension as a function of time after a step increase of 1% in length of right ventricular papillary muscles from 3- to 4-month-old mice. The average of tension transients from muscles of three normal mice (normal), three transgenic mice expressing the normal human ELC (human control), and four transgenic mice expressing the mutant human ELC (human mutant) are as noted in the key. Three- to four-month-old mice were used to avoid hypertrophy in the human mutant mice. The corresponding vertical arrows in each case mark the peak of the “second rise in tension.” Just below the time axis are shown the corresponding time delays (t_ds) with time origin at 0 s from the initiation of stretch. The three traces show that the t_d for the muscles from the human mutant mice is ≈1/3 that for the normal and human control mice.