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Study of ionospheric disturbances during solar flare events using the SuperDARN Hokkaido radar

Advances in Polar Science 2013年第1期24卷 12-18页

作者： daiki watanabe Nozomu Nishitani Solar-Terrestrial Environment Laboratory Nagoya University

It is well known that many types of ionospheric disturbances occur during solar flare events. The sudden increase in total electron content （SITEC） has been studied for several decades, but total electron content （TEC） data do not provide information on the altitudinal distribution of electron density changes. Previous studies used HF Doppler system data to investigate the contributions of the D-region and F-region ionospheric electron density changes by examining the HF radio wave frequency dependence on the Doppler shift values. In this study we examined the dependence of the elevation angle of the Doppler shift of ground scatter echoes using the SuperDARN Hokkaido radar. We analyzed solar flare events from Dec 2006 to Mar 2012. A sudden fade-out of echoes was observed in almost all the events we analyzed, which was the result of the radio absorption associated with a significant increase in electron density within the D-region ionosphere. In addition, we discovered positive Doppler shifts just before the sudden fade-out of echoes. The Doppler shift is negatively correlated with the elevation angle of received radar waves. It indicates that variation of electron density in the D-region ionosphere is dominant during solar flare events. This result is consistent with a previous study. We also compared the irradiation by X-ray and extreme ultra violet rays observed by the GOES-14 and GOES-15 satellites, which generated Doppler shifts. A positive Doppler shift is consistent with a change of X-ray

关键词： solar flare SuperDARN Hokkaido radar Doppler shift D-region F-region GOES satellite

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The Efficacy of Microcurrent Therapy on Eccentric Contraction-Induced Muscle Damage in Rat Fast-Twitch Skeletal Muscle

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Open Journal of Applied Sciences 2018年第3期8卷 89-102页

作者： Yosuke Hiroshige daiki watanabe Chihiro Aibara Keita Kanzaki Satoshi Matsunaga Masanobu Wada Department of Physical Education Faculty of Physical Education International Pacific University Okayama-shi Japan Graduate School of Integrated Arts and Sciences Hiroshima University Higashihiroshima-shi Japan Research Fellow of Japan Society for the Promotion of Science Department of Clinical Nutrition Faculty of Health Science and Technology Kawasaki University of Medical Welfare Kurashiki-shi Japan Faculty of Education University of Miyazaki Miyazaki-shi Japan

Microcurrent (MC) therapy, in which a very small electric current is applied to the body, has widely been used to promote tissue healing and relieve symptoms. The aim of this study was to examine the effect of MC treatment on eccentric contraction (ECC)-induced muscle damage in rat fast-twitch skeletal muscles. Tibialis anterior muscles underwent 200 repeated ECCs in situ and were then stimulated (25 μA, 0.3 Hz) for 20 min (MC treatment). MC treatment was performed immediately after ECC and during a recovery period of 3 days (a total of 4 times). Three days after ECC, the muscles were excised and used for measure of force output and for biochemical analyses. In MC-treated muscles, tetanic forces at 20 Hz and 100 Hz were partially and fully restored, respectively, whereas in non-treated muscles, both forces remained depressed. Biochemical analyses revealed that MC treatment partially or completely inhibited ECC-induced reductions: in 1) the Ca2+-release function of sarcoplasmic reticulum (SR), 2) proteolysis of ryanodine receptor, a Ca2+ release channel of SR, and 3) myosin ATPase activity. On the other hand, MC treatment was unable to lessen increases in the activity of calpain, a cytosolic, Ca2+-activated neutral protease. These results indicate that MC treatment results in beneficial effects, such as restoration of muscle performance following ECC, although the precise mechanisms are still unknown at this time.

关键词： Ryanodine Receptor Sarcoplasmic Reticulum SERCA Myosin ATPase

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Effect of Dietary Nitrate on Force Production and Sarcoplasmic Reticulum Ca<sup>2+</sup>Handling in Rat Fast-Twitch Muscles Following Eccentric Contraction

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Open Journal of Applied Sciences 2018年第12期8卷 607-618页

作者： Satoshi Matsunaga Chihiro Aibara daiki watanabe Keita Kanzaki Yurie Morizaki Sumiko Matsunaga-Futatsuki Masanobu Wada Faculty of Education University of Miyazaki Miyazaki Japan Graduate School of Integrated Arts and Sciences Hiroshima University Higashi-Hiroshima Japan Department of Engineering Science University of Electro-Communications Chofu Japan Faculty of Health Science and Technology Kawasaki University of Medical Welfare Kurashiki Japan Department of Communication and Liberal Arts Minami Kyushu Junior College Miyazaki Japan

Impaired excitation-contraction coupling occurs in eccentric contraction (ECC)-induced damaged muscles. It has been suggested that sarcoplasmic reticulum (SR) is susceptible to damage in the overstretched regions possibly marking the basis of excitation-contraction coupling damage. Recent studies have shown that dietary nitrate supplementation enhances SR function in fast-twitch muscles. In this study, we aimed to investigate whether dietary nitrate supplementation can alleviate a decline in muscle contractile properties and SR function following ECC. To this end, force production, Ca2+ uptake, Ca2+ release, and Ca2+-ATPase activity of the SR were examined in rat fast-twitch muscles immediately following ECC for 200 repetitions. In comparison with contralateral resting muscles, nitrate supplementation for up to 3 days resulted in an obvious decline in force production. However, there were no differences in terms of force production between 6-day nitrate-treated and contralateral muscles. Similar to the observations regarding force production, the SR Ca2+ release rate changed from an obvious decrease following the 0- and 3-day dietary nitrate supplementation to no difference following the 6-day nitrate supplementation. In contrast, ECC decreased the Ca2+-ATPase activity and Ca2+ uptake rate, irrespective of the period of dietary nitrate supplementation. Overall, these results indicate that dietary nitrate supplementation can alleviate ECC-related decreases in force production mediated through inhibited reductions in the SR Ca2+ release function.

关键词： Supplementation Ca2+-ATPase Activity Ca2+ Uptake Ca2+ Release

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