305c muscle lever system

Maximal force production of the plantar flexor muscle group was measured in vivo with a 305C muscle lever system (Aurora Scientific Inc., Aurora, Canada), as previously described (Khairallah et al, 2012 (link); Call & Lowe, 2016 (link)). Animals were anesthetized via inhalation (~2% isoflurane, SomnoSuite, Kent Scientific), placed on a thermostatically controlled table with anesthesia maintained via nose‐cone (~2% isoflurane), the knee fixed with a pin pressed against the tibial head, and the foot firmly fixed to a footplate on the motor shaft. Contractions were elicited by percutaneous electrical stimulation of the tibial nerve (0.2 ms pulse, 500 ms train duration) at increasing frequencies. Following assessment of isometric torque, susceptibility to injury was assayed with 25 eccentric contractions as previously described (Khairallah et al, 2012 (link); Call & Lowe, 2016 (link)) at maximal isometric torque (150 mS duration, 0.2‐mS pulse train at 150 Hz). Eccentric contractions were achieved by translating the footplate 38° backward at a velocity of 800°/S after the first 100 mS of the isometric contraction. The decrease in the peak isometric force before the eccentric phase was taken as an indication of muscle damage.

REGN1033 or control antibody (10 mg/kg) was administered to C57BL/6 male mice (n = 6/group) twice a week for 3 weeks via s.c. injection. At the end of 3 weeks of treatment, ex vivo force measurements of the TA muscle were obtained. Briefly, mice were anesthetized under isoflurane (4.5 %), and the right TA muscle was excised by cutting the femur just proximal to the femoral head above the knee and the tibia and fibula proximal to the ankle. The muscle was then placed in an oxygenated bath containing Krebs solution with 10 mM glucose at 27 °C. The femoral head was secured to a stanchion while the distal tendon was tied to the arm of a 305C Muscle Lever System (Aurora Scientific, Aurora, ON, Canada). Optimal length was achieved by increasing the length of the muscle by small increments followed by a single 1-Hz stimulation until a maximum twitch force was achieved. Maximal isometric tetanic force was then determined by stimulating each muscle at 10-Hz intervals (from 40 to 100 Hz) with 90-s rest periods prior to each stimulation.

Muscle performance was measured in vivo with a 305°C muscle lever system (Aurora Scientific Inc., Aurora, CAN). Animals were anesthetized via inhalation (~5% isoflurane), and placed in a thermostatically controlled table with anesthesia maintained via nose-cone (~2% isoflurane). For assessment of plantarflexor function, the knee was first isolated using a pin through the tibial head and the foot firmly fixed to a footplate on the motor shaft. Contractions were elicited by percutaneous electrical stimulation of the sciatic nerve, and optimal isometric twitch torque determined by increasing the current with a minimum of 30 s between each contraction to avoid fatigue. A series of stimulations were performed at increasing frequency of stimulation (0.2 ms pulse, 500 ms train duration): 1, 10, 20, 40, 60, 80, 100 and 150 Hz, followed by a final stimulation at 1 Hz. Data were analyzed using Aurora Scientific 615 A Dynamic Muscle Analysis Software Suite in high-throughput mode. Each data file was manually inspected to ensure that cursors and fits were assigned properly.