MECHANICAL CHARACTERISITICS OF RIB CAGE ELEVATOR MUSCLE OF REPTILE UROMASTIX hardwickii

Abstract

Background: Skeletal muscles are diverse in their contractile properties, with significant differences existing among and within various animal species. Uromastix is one of the desert adapted reptile that possesses unique mechanical characteristics for its skeletal muscles. Additionally, in the absence of diaphragm, this reptile involves one of its chest muscle named recently1 as Rib Cage Elevator (RCE) muscle that lift the rib cage during active respiration. Objecti ve: The purpose of this study was to test that increased frequency of stimulation alters the mechanical activity in RCE muscles as well or not and is there any difference in various strips of the RCE muscle of this animal in terms of endurance to high frequency of stimulation, fatigue and which of this strip is mainly responsible for lifting of rib cage during active respiration in this reptile in the absence of diaphragm. Method: For this purpose isolated strips of rib cage elevator muscle of Uromastix, (superior, middle and inferior) were used for isometric recordings to compare their mechanical activity. The isometric twitch (Strength 50V, duration 0.5ms and frequency 1Hz) and tetanus (Strength 50V, duration 0.5ms and frequencies, 16, 24, 40, 80, 160 and 240Hz) were recorded with 2 min rest in between each record. The twitch contraction (CT)
and twitch and tetanus half relaxation time (1/2RT), were also calculated together with the maximum rate of rise in twitch & tetanic tensions at above frequencies. Results: :