Fig. 7. (A) The cytoplasmic pool of Smad2 is big enough to supply the Smad2 flow for several hours. Dissociated animal cap cells, pretreated or not with cycloheximide for 1 hour, were then treated with a concentration of 4 ng/ml of activin for 15 minutes at stage 9, washed to remove the unbound activin, cultured for 3 hours and the total amount of Smad2 was determined by western blot, using an anti-Smad2 antibody. (B) Quantitation of the total amount of Smad2 from the experiment shown in A, using the public-domain NIH Image program.