Fluctuations in cyclic adenosine 3':5'-monophosphate and cyclic guanosine 3':5'-monophosphate during the mitotic cycle of the acellular slime mould Physarum polycephalum.

Cyclic adenosine 3′:5′-monophosphate (cyclic AMP) and cyclic guanosine 3′:5′-monophosphate (cyclic GMP) have been determined at half-hourly intervals throughout the mitotic cycle of Physarum polycephalum. Cyclic AMP was constant at 1pmole/mg protein throughout except for a transient peak of 17pmoles/mg protein in the last quarter of G2. Cyclic GMP was more variable (2–4pmole/mg protein) rising to 9.5pmole/mg protein during the 3 hour S period and to 7pmole/mg protein during the last hour of G2. The significance of these changes is discussed.