Torao Nagai
Sapporo University
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Featured researches published by Torao Nagai.
Comparative Biochemistry and Physiology Part A: Physiology | 1981
Takao Hasumi; Isao Kosaka; Torao Nagai
Abstract 1. 1. The potassium contracture in the anterior byssus retractor muscle of Mytilus edulis relaxed spontaneously, and the relaxation was accelerated by 5-HT (10 −6 M), but the contractile activation and inactivation was not affected significantly. 2. 2. By reducing [Ca] 0 , the “activation curve” was shifted downward at higher [K] 0 , and the “inactivation curve” was shifted toward lower [K] 0 and the rate of inactivation was increased. 3. 3. The steady-state inactivation was maintained for at least 2 hr without complete inactivation. 4. 4. The half-inactivation time was dependent on [K] 0 , while the half-relaxation time in the contracture induced by conditioning K solutions was not.
Archives of Biochemistry and Biophysics | 1970
Torao Nagai; Masa Takauji; Mamoru Jou; Tetsuzo Yamamoto
Abstract The effects of various concentrations of Mg2+ on the ATPase activities of native tropomyosin-free synthetic actomyosin, myosin B, and synthetic actomyosin to which native tropomyosin was added, and on the superprecipitation of myosin B, were investigated in the presence of 6.2 × 10−8 m Ca2+ and 1.7 × 10−5 m Ca2+. At 6.2 × 10−8 m Ca2+, ATPase activity of synthetic actomyosin was enhanced by 5 × 10−6 to 1 × 10−4 m Mg2+. Even with supramaximal amounts of Mg2+, the ATPase activity was not inhibited below the original level attained without added Mg2+. At 1.7 × 10−5 m Ca2+, the ATPase was markedly activated by Mg2+ in concentrations lower than 10−5 m . Further addition of Mg2+ decreased the ATPase activity toward, but not below, the original level. Unlike synthetic actomyosin, Mg2+-activated ATPase activity of myosin B and of synthetic actomyosin to which native tropomyosin was added falls below the original level at high Mg2+ concentrations if Ca2+ level is very low. This inhibitory effect of Mg2+ is abolished by high concentrations of Ca2+. On the basis of these and related findings, we suggest mechanisms for the inhibitory action of native tropomyosin and for the dual effect of Mg2+.
Japanese Journal of Physiology | 1975
Masa Takauji; Nobuaki Takahashi; Torao Nagai
Japanese Journal of Physiology | 1972
Isao Oota; Masa Takauji; Torao Nagai
Japanese Journal of Physiology | 1975
Masa Takauji; Nobuaki Takahashi; Torao Nagai
Japanese Journal of Physiology | 1977
Isao Oota; Torao Nagai
Japanese Journal of Physiology | 1970
Motoya Taniguchi; Torao Nagai
Japanese Journal of Physiology | 1962
Toshio Yamaguchi; Tatsuaki Matsushima; Masahiro Fujino; Torao Nagai
Japanese Journal of Physiology | 1983
Hideaki Kanaya; Masa Takauji; Torao Nagai
Japanese Journal of Physiology | 1976
Isao Oota; Isao Kosaka; Torao Nagai