No abstract

No abstract

No abstract

backward swimming of paramecia. The Triton-extracted paramecia, where the membrane was disrupted and the externally applied chemicals are freely accessible to the ciliary apparatus, showed forward 2+ (0.1 mM) did not change the relationship between the swimming directions and free Ca 2+ concentrations. Effects of various surfactants including PFOS and PFOA on the swimming direction of paramecia were compared with the hemolysis of mouse erythrocytes as an indicator of surfactant activities. The hemolysis did not correlate with their swimming behavior. PFOS caused triphasic membrane potential changes both in the wild-type paramecia and caudatum non-reversal (CNR) mutants, the latter is defective in voltagegated Ca 2+ channels. An action potential of the wild-type specimen was induced at lower current intensity when PFOS was present in the medium. Voltage-clamp study indicated that PFOS had no effect on the depolarization-induced Ca 2+ obtained were similar to those obtained by the application of some bitter substances such as quinine that activate chemoreceptors of paramecia. Since the CNR specimens did not exhibit PFOS-induced backward 2+ into the cilia through voltage-gated Ca 2+ channels. The Ca 2+ channels are most probably activated by the depolarizing receptor potentials resulted from the PFOS-induced activation of chemoreceptors.