Fig. 5. Actin polymerisation in sensitised amoebae. (A) F-actin levels in sensitised amoebae after addition of cAMP – known as the ‘cringe’ reaction (Hall et al., 1988). (B,C) ts2 amoebae held at 22°C (B) or 28°C (C), fixed with formaldehyde and stained with Alexa 488-phalloidin to reveal the intracellular distribution of F-actin. The levels of F-actin at 28°C, based on phalloidin binding (as in A) and normalised to that at 22°C, were measured as Ax2, 0.68; ts1, 0.57; ts2, 0.68.