Specific effects of both in vivo activation and in vitro activation by cAMP-dependent phosphorylation on bending wave parameters of demembranated, reactivated, tunicate (Ciona intestinalis) and sea urchin (Lytechinus pictus) sperm flagella can be reversed by exposure to protein phosphatase. The effects of protein phosphatase incubation can be imitated by inclusion of LiCl in the reactivation solutions. The primary effect of cAMP-dependent phosphorylation appears to be activation of a regulatory mechanism controlling flagellar oscillation, rather than activation of the active sliding mechanism. Lithium appears to act on the same regulatory mechanism.

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