title: High-frequency sarcomeric auto-oscillations induced by heating in living neonatal cardiomyocytes of the rat.
abstract: In the present study, we investigated the effects of infra-red laser irradiation on sarcomere dynamics in living neonatal cardiomyocytes of the rat. A rapid increase in temperature to >~38 °C induced [Ca(2+)]i-independent high-frequency (~5-10 Hz) sarcomeric auto-oscillations (Hyperthermal Sarcomeric Oscillations; HSOs). In myocytes with the intact sarcoplasmic reticular functions, HSOs coexisted with [Ca(2+)]i-dependent spontaneous beating in the same sarcomeres, with markedly varying frequencies (~10 and ~1 Hz for the former and latter, respectively). HSOs likewise occurred following blockade of the sarcoplasmic reticular functions, with the amplitude becoming larger and the frequency lower in a time-dependent manner. The present findings suggest that in the mammalian heart, sarcomeres spontaneously oscillate at higher frequencies than the sinus rhythm at temperatures slightly above the physiologically relevant levels.
authors.affiliation: Department of Pure and Applied Physics, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan.
authors.forename: Seine A
authors.initials: SA
authors.lastname: Shintani
authors.affiliation: Department of Pure and Applied Physics, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Oyama
authors.affiliation: Department of Cell Physiology, The Jikei University School of Medicine, Tokyo, Japan. Electronic address: noriof@jikei.ac.jp.
authors.forename: Norio
authors.initials: N
authors.lastname: Fukuda
authors.affiliation: Department of Pure and Applied Physics, School of Advanced Science and Engineering, Waseda University, Tokyo, Japan; WASEDA Bioscience Research Institute in Singapore (WABIOS), Singapore. Electronic address: ishiwata@waseda.jp.
authors.forename: Shin'ichi
authors.initials: S
authors.lastname: Ishiwata
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002470:Cell Survival; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006361:Heating; D032383:Myocytes, Cardiac / Q000166:cytology* / Q000502:physiology*; D051381:Rats; D012518:Sarcomeres / Q000502:physiology*; D013696:Temperature
keywords: Cardiac muscle; Contractility; Imaging; Sarcomere dynamics