Teizo Tsuchiya

Mechanical activity in the lantern retractor muscle of a sea-urchin Anthocidaris crassispina

Abstract 1. 1. The meehanical response of the lantern retractor muscle of a sea-urchin Anthocidaris crassispina to electrical stimulation and drugs was studied. 2. 2. The reduction of [Ca] 0 to 1 mM reduced the magnitude of mechanical response to electrical stimulation and high [K] 0 , but not the response to ACh. 3. 3. Procaine (2 mM) reduced the ACh-contracture tension, but not the response to electrical stimulation and high [K] 0 . 4. 4. The hypertonic solution produced tension even in the absence of [Ca] 0 . 5. 5. It is suggested that the response to electrical stimulation and high [K] 0 is mainly associated with calcium-influx, while that to ACh is largely due to the release of intracellularly stored calcium.

Time course of tension decay after stretch and unloaded shortening velocity in molluscan catch muscle at various physiological states

Abstract 1. 1. The anterior byssus retractor muscle of Mytilus was stimulated to contract with ACh, and the time courses of tension decay after an applied stretch (6% of l0), as well as the unloaded shortening velocity, were examined at various states, i.e. (1) at the peak of initial tension development, (2) during the prolonged application of ACh, (3) after washout of ACh, (4) in the sucrose-hypertonic solution and (5) in the NaCl-hypertonic solution. 2. 2. The tension decay after stretch was resolved into three exponential components. 3. 3. The relationship between the amplitudes of three exponential components and the unloaded shortening velocity was examined in the above five states. It was shown that the intermediate component and the slow one were related to active and tonic contractions, respectively.

Muscle Stiffness Changes during Isometric Contraction in Frog Skeletal Muscle as Studied by the Use of Ultrasonic Waves

In order to measure muscle stiffness changes with a high time resolution and with minimal disturbance to the contractile mechanism per se, we constructed an apparatus with which the propagation velocity of ultrasonic waves (MHz region) in the longitudinal or transverse direction was measured to serve as a measure of muscle stiffness. The longitudinal muscle stiffness started to increase on stimulation before the onset of isometric force, and reached a maximum before the peak twitch force. Analysis of experimental data indicated that, during an isometric tetanus, the increment of muscle longitudinal stiffness was about 6 X 10(7)N/m2, a value similar to those obtained by Truong (1974) and Ford et al. (1981) with sinusoidal vibrations (3 kHz) and length steps respectively. This suggests that the increment of muscle longitudinal stiffness during the activation of the contractile system results from the recruitment of an almost non-dispersive elastic component. In the case of transverse muscle stiffness, on the other hand, it started to decrease on stimulation before the onset of isometric force, and reached a minimum before the peak twitch force. Possible causes of this unexpected result is discussed in relation to the molecular mechanism of muscle contraction.

Effects of temperature and metabolic inhibitors on contraction of anterior byssus retractor muscle of Mytilus

Abstract 1. 1. Anterior byssus retractor muscle of Mytilus (ABRM) was stimulated to contract by ACh (acetylcholine) and effects of temperature (5–30°C), FDNB (1-fluoro 2,4 dinitro-benzene) and IAA (iodoacetic acid) on tension response were examined. 2. 2. Isometric tension was highest at the temperature range of 10–20°C and decreased at higher and lower temperature than that range. 3. 3. The rate of tension decay after washing of ACh was accelerated by the increase of temperature. 4. 4. Tension redevelopment after release of 1 % during contraction was much smaller at 5°C than at 20°C. 5. 5. Tension development by ACh and the rate of tension decay after washing of ACh were remarkably decreased by the treatment of FDNB or IAA. 6. 6. The above results were discussed from the viewpoint that energy metabolism might be related to catch.

Regulation of smooth muscle contraction by the myosin light chain phosphorylation-dependent and -independent mechanisms.

Smooth muscle contraction is suggested to be due to increments in cytosolic Ca++ level ([Ca++]i), myosin light chain (MLC) phosphorylation and Ca++ sensitivity of MLC phosphorylation, and also to a mechanism which is highly sensitive to Ca++ but not dependent on MLC phosphorylation.

Changes in Mechanical Properties in Osmotically Compressed Skinned Muscle Fibers of Frog

The mechanical properties of frog skinned muscle fibers were examined in PVP solution. In a high concentration of PVP, the velocity of isotonic shortening and lengthening decreased remarkably and the stiffness increased not only in the activation solution but also in the relaxing solution.