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Articles by M Inagaki
Total Records ( 2 ) for M Inagaki
  K Seo , M Inagaki , S Nishimura , I Hidaka , M Sugimachi , T Hisada and S. Sugiura

Rationale: Mechanical stress is known to alter the electrophysiological properties of the myocardium and may trigger fatal arrhythmias when an abnormal load is applied to the heart.

Objective: We tested the hypothesis that the structural heterogeneity of the ventricular wall modulates globally applied stretches to create heterogeneous strain distributions that lead to the initiation of arrhythmias.

Methods and Results: We applied global stretches to arterially perfused rabbit right ventricular tissue preparations. The distribution of strain (determined by marker tracking) and the transmembrane potential (measured by optical mapping) were simultaneously recorded while accounting for motion artifacts. The 3D structure of the preparations was also examined using a laser displacement meter. To examine whether such observations can be translated to the physiological condition, we performed similar measurements in whole heart preparations while applying volume pulses to the right ventricle. At the tissue level, larger stretches (≥20%) caused synchronous excitation of the entire preparation, whereas medium stretches (10% and 15%) induced focal excitation. We found a significant correlation between the local strain and the local thickness, and the probability for focal excitation was highest for medium stretches. In the whole heart preparations, we observed that such focal excitations developed into reentrant arrhythmias.

Conclusions: Global stretches of intermediate strength, rather than intense stretches, created heterogeneous strain (excitation) distributions in the ventricular wall, which can trigger fatal arrhythmias.

  X Xu , Y Horibata , M Inagaki , Y Hama , K Sakaguchi , H. M Goda and M. Ito

Endoglycoceramidase (EGCase; EC is a glycohydrolase that hydrolyzes the glycosidic linkage between the oligosaccharide and ceramide of various glycosphingolipids. We previously reported that hydra produced EGCase to digest glycosphingolipids of brine shrimp (Artemia salina), a type of aquatic crustacean used as a diet for the culture of hydra (Horibata Y, Sakaguchi K, Okino N, Iida H, Inagaki M, Fujisawa T, Hama Y, Ito M. 2004. J Biol Chem. 279:33379-33389). We report here that a major glycosphingolipid of brine shrimp is unique in structure and highly sensitive to EGCase. The glycosphingolipid was extracted from freshly hatched brine shrimp by Folch's partition, followed by mild alkaline hydrolysis and purification with a Sep-Pak plus silica cartridge. The structure of brine shrimp glycosphingolipid was determined by gas chromatography, gas chromatography-mass spectrometry, fast-atom bombardment mass spectrometry, and 1H-NMR spectrometry to be GlcNAc1-2Fuc1-3Manβ1-4Glcβ1-1'Cer. Two major molecular species of the glycosphingolipid were identified; the sugar and sphingoid base of each were the same but the major fatty acid was C22:0 and 2-hydroxy C22:0, respectively. This is the first report describing the glycosphingolipid that has an internal fucosyl residue substituted with 1-2 N-acetylglucosaminyl residue. This study also suggests the biological relevance of the glycosphingolipid as a dietary source of hydra which possesses EGCase as a digestion enzyme.

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