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Katayama T.,Gunma University | Watanabe M.,Tokyo Medical University | Tanaka H.,Gunma University | Hino M.,Gunma University | And 12 more authors.
American Journal of Physiology - Heart and Circulatory Physiology | Year: 2010

We have been searching for a mechanism to induce smooth muscle contraction that is not associated with phosphorylation of the regulatory light chain (RLC) of smooth muscle myosin (Nakamura A, Xie C, Zhang Y, Gao Y, Wang HH, Ye LH, Kishi H, Okagaki T, Yoshiyama S, Hayakawa K, Ishikawa R, Kohama K. Biochem Biophys Res Commun 369: 135-143, 2008). In this article, we report that arachidonic acid (AA) stimulates ATPase activity of unphosphorylated smooth muscle myosin with maximal stimulation (R max) of 6.84 ± 0.51 relative to stimulation by the vehicle and with a half-maximal effective concentration (EC 50) of 50.3 ± 4.2 μM. In the presence of actin, R max was 1.72 ± 0.08 and EC 50 was 26.3 ± 2.3 μM. Our experiments with eicosanoids consisting of the AA cascade suggested that they neither stimulated nor inhibited the activity. Under conditions that did not allow RLC to be phosphorylated, AA stimulated contraction of smooth muscle tissue with an R max of 1.45 ± 0.07 and an EC 50 of 27.0 ± 4.4 μM. In addition to the ATPase activities of the myosin, AA stimulated those of heavy meromyosin, subfragment 1 (S1), S1 from which the RLC was removed, and a recombinant heavy chain consisting of the myosin head. The stimulatory effects of AA on these preparations were about twofold. The site of AA action was indicated to be the step-releasing inorganic phosphate (P i) from the reaction intermediate of the myosin-ADP-P i complex. The enhancement of Pi release by AA was supported by computer simulation indicating that AA docked in the actin-binding cleft of the myosin motor domain. The stimulatory effect of AA was detectable with both unphosphorylated myosin and the myosin in which RLC was fully phosphorylated. The AA effect on both myosin forms was suggested to cause excess contraction such as vasospasm. Copyright © 2010 the American Physiological Society. Source

Arai K.,Osaka Prefecture University | Akita Y.,Osaka Prefecture University | Yagi I.,Osaka Prefecture University | Yotsuya T.,Osaka Prefecture University | And 9 more authors.
Physica C: Superconductivity and its Applications | Year: 2010

The MgB2 detector consists of a 200-nm-thick MgB2 thin-film meander line, a 300-nm-thick SiO protective layer, and 150-nm-thick Nb electrodes. We prepared a straight MgB2 stripline of width 3 μm and length 100 μm. To understand the position-dependent sensitivity of the MgB2 detector, a scanning pulsed laser spot can be achieved by the combination of the XYZ piezo-drive stages and an optical fiber with an aspheric focusing lens. The observed scanning XY image indicates that the improvement in sensor homogeneity is very important to improve the sensitivity of the MgB 2 sensor as a neutron detector. © 2009 Elsevier B.V. All rights reserved. Source

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