Fig. 3. Effect of actinomycin D upon BrUTP incorporation. Densities (gold particles/µm²) on the FC, DFC, GC and resin (R) were calculated in untreated and actinomycin-D-treated nucleoli incubated with BrUTP for 10 minutes. The results represent mean values±s.e.m. 13 and 8 random micrographs were analyzed and 211 and 47 gold particles were counted, respectively. Student's t-test for nucleolar components versus resin (+ P<0.05, ++ P<0.01) for each nucleolar component in untreated versus treated nucleoli (^* P<0.05, ^** P<0.01) and for FC versus DFC in untreated or treated nucleoli (^ P<0.05, ^^ P<0.01) was used.