Fig. 1. Representative traces of the electrical potential of the contractile vacuole (CV) fluid with reference to the cytosol in Paramecium multimicronucleatum (CV membrane potential) and the input resistance of the CV (A; filled circles). (A) A non-compressed (normal) cell. (B) A mechanically compressed cell. F, R and D above segments of potential traces correspond to the fluid-filling, rounding and fluid-discharging phases of exocytotic cycles of the CV, respectively. Double slashes on the potential trace in B indicate interruptions to the CV membrane potential recording when the electrode tip was no longer in an intact CV during the fluid-discharging phase. See the text for further details. Exocytic cycles are numbered.

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