| Budget Amount *help |
¥2,200,000 (Direct Cost: ¥2,200,000)
Fiscal Year 1989: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1988: ¥1,900,000 (Direct Cost: ¥1,900,000)
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| Research Abstract |
To evaluate the dynanic mechanical-properties of contractile system and the ATPase activity in jaw muscles, we analyzed the tension transients in response to small ( 1% of muscle length ) step and sinusoidal length perturbations, and the Ca^<2+> sensitivity of isometric tension development, ATPase activity and maximum shortening velocity (Vmax) in guinea pig glycerinated masseter, temporal and digastric muscles, using a newly developed length servocontrol system. The transient tension responses could be approximated by three exponential functions, each of which has a time constant, T_1, T_2, T_3 in the order of large to small, as has been observed in other skeletal muscles. T_2 and T_3, which are believed to reflect the rate of cross-bridge cycling, were different among the three muscles (in the digastric in the temporalis in the masseter) when the preparations were activated maximally. These results indicate higher cross-bridge cycling rate in the masseter and lower rate in the digastric muscle. The isometric tension increased in a sigmoid fashion with an increase in Ca^<2+> concentration from about pCa 6.6 to pCa 5.8 in all of the three muscles. The ATPase activity also increased sigmoidally with an increase in Ca^<2+> concentration from slightly above pCa 6.6 to slightly below pCa 5.8. The tension cost (ATPase activity / isometric tension) estimated from above results was lower in the digastrib than in the temporalis or masseter, indicating more economical ATP consumption in the digastric. Vmax increased, with an increase in Ca^<2+> concentration (i.ei., with an increase in isometric tension), and greater in the masseter than in the other two muscles when compared at the same developed tension level. These results seem to be consistent with the results obtained from the transient tension response analysis.
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