Protoplasmic Streaming of a Slime Mold, Physarum Polycephalum* Ii . Theoretical Treatment 01~ the Electric Potential Rhythm by Uichiro Kishimoto

The electric potential difference (1 to 15 Inv.) between two loci of the slime mold connected with a strand of protoplasm changes rhythmically with the same period (60 to 180 seconds) as that of back and forth protoplasmic streaming along the strand. When atmospheric pressure at a part of the plasmodium is increased (about 10 cm. H~O), the dectric potential at this part becomes positive (0 to 20 Inv.) to another part with a time constant of 2 to 15 minutes. If the atmospheric pressure at a part of the plasmodium is changed (about 10 cm. H~O) periodically, the electric potential rhythm also changes with the same period as that of the applied pressure change, and the amplitude of the former grows to a new level (i.e., forced oscillation). The electric potential rhythm, in this case, is generally delayed about 90 ° in phase angle from the external pressure change. The period of the electric potential rhythm which coincided with that of the pressure change is maintained for a while after stopping the application of the pressure change, if the period is not much different from the native flow rhythm. Such a pressure effect is brought about by the forced transport of protoplasm and is reversible as a rule. In the statistical analysis made by Kishimoto (1958) and in the theological treatment made in the report, the rhythmic deformation of the contractile protein networks is supposed to be the cause of the protoplasmic flow along the strand and of the electric potential rhythm. The role of such submicroscopic networks in the protoplasm in various kinds of protoplasmic movement is emphasized. The cells, in which we can study the protoplasmic movement, all show sollike inner protoplasm (plasmasol) and a gel-like outer protoplasmic layer (plasmagel). Microscopic granules are in lively movement (i.e., Brownian movement or flow) in the endoplasm where the viscosity is considered to be comparatively low, while in the outer protoplasmic layer they are motionless. According to Goldacre (1952) and Goldacre and Lorch (1950), the protein molecules are in a folded state in the endoplasm, and in an unfolded state in the ectoplasm. However, a "folding and unfolding" mechanism alone is per* Supported by a Grant for Fundamental Scientific Research from the Ministry of Education.