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Agladze, K.

Horning, M.

Isomura, A.

Yoshikawa, K.

Kyoto University Research Information Repository

TitleControlling Excitable Waves in Cultured CardioMyocyte(Poster session 1, New Frontiers in Colloidal Physics :A Bridge between Micro- and Macroscopic Concepts in SoftMatter)Author(s)Horning, M.; Isomura, A.; Agladze, K.; Yoshikawa, K.Citation物性研究 (2007), 89(1): 69-70Issue Date2007-10-20URL http://hdl.handle.net/2433/110941RightType Departmental Bulletin PaperTextversionpublisherKyoto UniversityiNew Frontiers in Colloidal PhysicsJ Controlling Excitable Waves in Cultured Cardio Myocyte M. Horningα1， A. IsomuraO'， K. Agladzes， and K. YoshikawaO' αDeptartment of Physics， Kyoto Univ.， Kyoto 606-8502， JAPAN βGeorge Washington University， Washington DC， USA Motivation Rotating waves are believed to be responsible for many dangerous cardiac tachyarrhythmias， which are precursors of ventricular fibrillation， causing sudden death. Thus， the conもrollingof excitable waves in cardiomyocyte culture is an auspicious wayもounderstand七hephysics of rotating waves in cardiac tissue. In real hear七tissuefree spiral waves rarely occur because they easily become bound to natural inhomogeneities such as blood vessels. Here we report mutual transformations of free and bound spiral waves (their pinning and unpinning) as well加 induceddrift of free rotating waves in cardiac tissue. Methods Cardiac cells were dissociated from ventricles of 1-day-old rats by l凶ngcollagenase[l] ， and plated on 22mm in diameter sized cover-slips. After 3 days of incubation in cu1ture medium the cells grow to a ful developed network and excitation waves are observable by monitoring calcium transient. The excitation waves were visualized with the aid of calcium sensitive fiuorescent dye (fiuo-4) by use of a 臥町escentmicroscope and an EM-CCD camera. Spontaneous activity in the cardiomyocyte tissue leads to wave speeds up to 10cms-1• In order to decre回ethe speed to a suitable degree we applied heptanol. Application of heptanol also leads to spontaneous origination of free rotating waves with the frequencies of rotation in the order of 1Hz. These rotating waves have slightly different periods each other， sothaももheones with lower period force 七heones wi七hhigher period七odrift away. Far-field and point electrode s七imulationswith applied 1.8V / cm and 6V， respectively， were used for wave initiation. Point stimulation produced waves in the immedia七evicinity of the electrode七ip;far field stimulation resulted in wave origination at the extended sites usually located near the edge of the coverslip. Results and Discussion Figure 1 exemplified the drif七ofthe spiral tip caused by far field stimulation. When paced wave collides with七he七ip，local re仕actorinessprevents the spiral from curling into the same area causing a displacement of the wavebreak. Subsequent paced waves continue to displace the tip， 1 E-mail: marcel@chem.scphys.kyot仁川l.ac.jp-69一研究会報告Figure 1: Spiral drift induced by far-field stimulation. Field of view: 2x2 mm thus causing it to drift[2]. This generic mechanism is also observable in Belousov-Zhabotinsky reactions [3]. Pinning of free rotational waves to obstacles was performed by removing cardiac tissue in the area at the tip of the spiral. Through this method we produced pinned spirals with differen七rotating仕equenciescaused by the different obstacle radii. We successfully un-pinned spiral waves from obstacles via mono-polar point electrode and far field s七imulation.One example of unpinning by stimulation from point electrode is shown in Figure 2. The far field stimulation leads to origination of excited sites as a 'Secondary Source'[4] adjacent to the ob-stacle， which unpins rotating spiral. Unpinning via point electrode is caused by 'direct' pacing nearby the obstacle. These results indicate that such methods are useful for the elimination of pinned rotating waves. F¥rrther studies will give auspicious results， and will lead to deeper understanding of termination of rotating waves in heart tissue. Figure 2: Unpinning of a rotating wave from an obs七aclevia point s七imulation.The first pacing wave creates one more free spiral besides the obstacle via colliding with the rotating wave. The annihilation of pacing wave， free spiral and rotating wave leads to unpinning (t回1.38).The pacing waves can propagate仕切 fromthe obstacle free. Field of view: 4x4 mm References 1) S. Matoba et al.， Circulation 99 (1999)，817. 2) K. Agladze et al.， Physiol Heart Circ Physiol， inpress， PMID: 17384124 (2007) 3) V. Krinski and K. Agladze， Physica D: Nonlinear Phenomena， 8， (1983)， 50 4) V.O. Fast et al.， Circulation Research 82 (1998)， 375. ????

Controlling Excitable Waves in Cultured Cardio Myocyte(Poster session 1, New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)

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Controlling Excitable Waves in Cultured Cardio Myocyte(Poster session 1, New Frontiers in Colloidal Physics : A Bridge between Micro- and Macroscopic Concepts in Soft Matter)

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