Model 300b lr

The functional properties of skeletal muscles of control, Speg-KO, and Speg-rescue mice were directly assessed using the ex vivo methods described in our earlier work with this model (7 (link)). EDL muscles were dissected and attached via their tendons to the lever arm of a dual-mode muscle lever system (Aurora Scientific, model 300B-LR) and a stationary post. The muscles were submerged in a temperature-controlled (35°C) bicarbonate buffer continuously equilibrated with 95% O₂, 5% CO₂.
Contractions were induced via output from a biphasic muscle stimulator delivered to platinum electrodes flanking the preparation. Data were collected at the muscle length (optimal length) that maximized tetanic force (300 Hz). Muscles were stimulated with trains of square wave pulses of increasing frequency (from 10 up to 400 Hz). The force-frequency data were fit by a sigmoidal curve as described previously (7 (link)), yielding parameters specifying the minimal force (equivalent to twitch force), maximum force (equivalent to peak tetanic force), inflection point of the curve, and curve’s slope. Physiological CSA area, used to normalize tetanic force, was calculated as mass/(fiber length × muscle density). Fiber length was calculated as muscle optimal length × 0.44, where 0.44 is the fiber length–to–muscle length ratio of the EDL (55 (link)). Muscle density was taken as 1.06 mg/mm³ (56 ).

The nine model parameters which characterize the biomechanical properties of human male vocal fold tissues were taken from previously published work [1] (link). To briefly summarize that study, tensile mechanical properties of tissue were measured using a sinusoidal stretch-release deformation of vocal fold tissue. Parameters of vocal fold cover and vocal fold ligament model from that study were chosen for two subjects to represent two distinctly different cases in which the viscous response is significant (33 y/o male) and suppressed (65 y/o male). In so doing, the two subjects represent a general trend in viscous response with age [16] (link). As presented in the previous work [1] (link), tissue specimens were dissected from human larynges excised within 24 hours postmortem. Specimen preparation was done with instruments for phonomicrosugery. Each specimen was maintained at 37 C in Kregs-Ringer solution at pH 7.4 while mounted vertically to the lever arm (sutured) of a dual-mode server-control lever system (Aurora Scientific Model 300BLR, Aurora, ON).