Masaki Shitara

Tokyo University of Science, Edo, Tōkyō, Japan

Are you Masaki Shitara?

Claim your profile

Publications (4)8.91 Total impact

  • [Show abstract] [Hide abstract] ABSTRACT: This study used an electrochemical O2. sensor to investigate the effects of hyperoxia on generation of the superoxide radical (O2.) in the jugular vein during forebrain I/R in rats. Twenty-eight male Wistar rats were allocated to a sham group (n = 7; sham-treated rats with inspired oxygen fraction [FiO2] of 0.4), a hemorrhagic shock and reperfusion (HS/R) group (n = 7; HS without carotid artery occlusion and reperfusion with FiO2 of 0.4), a normoxia group (n = 7; forebrain ischemia produced by bilateral carotid arteries occlusion with HS and reperfusion with FiO2 of 0.4), and a hyperoxia group (n = 7; forebrain ischemia with FiO2 of 0.4 and reperfusion with FiO2 of 1.0). The jugular venous O2. current was measured for 10 min during forebrain ischemia and for 120 min after reperfusion. The O2. current increased gradually during forebrain ischemia in the three groups other than the sham group. Immediately after reperfusion, the current showed a marked increase in the normoxia group and a pronounced decrease in the hyperoxia group. Levels of brain and plasma malondialdehyde, high-mobility group box 1 protein, and intercellular adhesion molecule 1 were significantly attenuated in the hyperoxia group relative to those in the normoxia group. In conclusion, hyperoxia suppressed jugular venous O2. generation and malondialdehyde, high-mobility group box 1, and intercellular adhesion molecule 1 in the brain and plasma in the acute phase of cerebral I/R. Thus, the administration of 100% oxygen immediately after reperfusion suppresses oxidative stress and early inflammation in cerebral I/R.
    No preview · Article · Dec 2009 · Shock (Augusta, Ga.)
  • [Show abstract] [Hide abstract] ABSTRACT: The aim of this study was to assess the effect of moderate hypothermia (MH) on generation of jugular venous superoxide radical (O2-.), oxidative stress, early inflammation, and endothelial injury in forebrain ischemia/reperfusion (FBI/R) rats. Twenty-one Wistar rats were allocated to a control group (n=7, 37 degrees C), a pre-MH group (n=7, 32 degrees C before ischemia), and a post-MH group (n=7, 32 degrees C after reperfusion). MH was induced before induction of ischemia in the pre-MH group and just after reperfusion in the post-MH group. Forebrain ischemia was induced by occlusion of bilateral common carotid arteries with hemorrhagic hypotension for 10 min, followed by reperfusion. O(2)(-)(.) in the jugular vein was measured from the produced current using a novel O2-. sensor. The O2-. current showed a gradual increase during forebrain ischemia in the control and post-MH groups but was attenuated in the pre-MH group. Following reperfusion, the current showed a marked increase in the control group but was strongly attenuated in the pre- and post-MH groups. Concentrations of malondialdehyde, high-mobility group box 1 (HMGB1) protein, and intercellular adhesion molecule-1 (ICAM-1) in the brain and plasma 120 min after reperfusion in the pre- and post-MH groups were significantly lower than those in the control group, except for plasma HMGB1 in the post-MH group. In conclusion, MH suppressed O2-. measured in the jugular vein, oxidative stress, early inflammation, and endothelial injury in FBI/R rats.
    No preview · Article · Nov 2009 · Brain research
  • [Show abstract] [Hide abstract] ABSTRACT: The aim of this study was to confirm the effect of acute hyperglycemia on the superoxide anion radical (O(2)(-)) generation, using a novel electrochemical O(2)(-) sensor in forebrain ischemia/reperfusion rats. Fourteen male Wistar rats were allocated to a normoglycemia group (n= 7) and a hyperglycemia group (n=7). Hyperglycemia was induced by intravenous infusion of glucose solution. Forebrain ischemia was induced by bilateral common carotid arteries occlusion with hemorrhagic hypotension for 10 min and then was reperfused. The generated O(2)(-) was measured as the current produced, which was integrated as a quantified partial value of electricity (Q), in the jugular vein using the O(2)(-) sensor. The reacted O(2)(-) current and the Q began to increase gradually during the forebrain ischemia in both groups. These values increased remarkably just after reperfusion in the normoglycemia group and were further increased significantly in the hyperglycemia group after the reperfusion. Concentrations of malondialdehyde (MDA) and high-mobility group box 1 (HMGB1) in the brain and plasma, and soluble intercellular adhesion molecule-1 (ICAM-1) in the plasma in the hyperglycemia group were significantly higher than those in the normoglycemia group. Brain and plasma MDA, HMGB1, and ICAM-1 were correlated with a sum of Q during ischemia and after reperfusion. In conclusion, acute transient hyperglycemia enhanced the O(2)(-) generation in blood and exacerbated oxidative stress, early inflammation, and endothelial injury after the forebrain ischemia/reperfusion in the rats.
    No preview · Article · Nov 2009 · Brain research
  • [Show abstract] [Hide abstract] ABSTRACT: Reactive oxygen species (ROS) such as the superoxide anion radical (O2-•) play an essential role on normal cellular growth and homeostasis. However, excess ROS generated by perturbing O2-• homeostasis under various conditions of oxidative stress induce high radical toxicity, resulting in many diseases such as a cancer, brain and mitocondrial infarction, and inflammation. Therefore, quantitative measurement of O21• in vivo is important for clarifying their relationship under various conditions. However, in most cases, the biological significance and mechanism of the O21• generation are not well understood yet. We have developed a O21• sensor composed of a thin film of N-methylimidazole-coordinated iron meso-tetra (3-thienyl) porphyrin ((Im)2FeT3ThP) for the electrochemical detection of O2-•. The microsensor displayed high selectivity and activity for the oxidation of O2-• and showed a linear relationship between electric current and O2-• concentration. In this study, we have designed and synthesized a novel hexa-coordinated iron (III) porphyrin compound, which is more stable than the meso-tetra (3-thienyl) porphyrin coordinating imidazoles. This compound was electropolymerized onto the electrode and used as a O2-• sensor. The redox potential of the electrode suggests that the molecular structure in the electropolymerized film is maintained. This novel modified electrode displayed a high activity for the oxidation of O2-• even in the presence of H2O2 and showed a linear relationship between the electric current and O2-• concentration.
    No preview · Article · May 2008 · KOBUNSHI RONBUNSHU