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Cell Biology International (2010) 34, 35–40 (Printed in Great Britain)

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Calcium wave for cytoplasmic streaming of Physarum polycephalum

Shinji Yoshiyama*†, Mitsuo Ishigami*, Akio Nakamura† and Kazuhiro Kohama*¹

*Department of Biology, Faculty of Education, Shiga University, Otsu, Shiga 520-0862, Japan, and †Department of Molecular and Cellular Pharmacology, Gunma University Graduate School of Medicine, Gunma 371-8511, Japan

The plasmodium Physarum polycepharum exhibits periodic cycles of cytoplasmic streaming in association with those of contraction and relaxation movement. In the present study, we injected Calcium Green dextran as a fluorescent Ca²⁺ indicator into the thin-spread living plasmodium. We found changes in the [Ca²⁺]i (intracellular concentration of Ca²⁺), which propagated in a wave-like form in its cytoplasm. The Ca²⁺ waves were also detected when we used Fura dextran which detected [Ca²⁺]i by the ratio of two wavelengths. We prepared the plasmodial fragment from the thin-spread and found that the cycles of the contraction–relaxation movement was so synchronized that the measurement of its area provided an indication of the movement. We observed that [Ca²⁺]i also synchronized in the entire fragment and that the relaxation ensued upon the reduction in [Ca²⁺]i. We suggest that the Ca²⁺ wave generated periodically is one of the major factors playing a crucial role in the relaxation of P. polycepharum.

Key words: actin, calcium, contraction, myosin, Physarum plasmodia, relaxation

Abbreviations: [Ca²⁺]i, intracellular Ca²⁺ concentration, CCD, charge-coupled device

¹To whom correspondence should be addressed (email kohamak@med.gunma-u.ac.jp).

Received 4 November 2008/17 June 2009; accepted 10 September 2009

Published as Cell Biology International Immediate Publication 10 September 2009, doi:10.1042/CBI20090158

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