Fig. 3. TSC colonies and cell death from dissociated whole ExE and ChE throughout post-implantation development. (A) TSC colonies derived from dissociated whole ExE/ChEs throughout stages in post-implantation development. The mean frequency of TSC colonies was determined as the number of TSC colonies/number of tissues dissociated. The range of TSC colonies obtained from individual tissues is indicated in square brackets. (B) The mean percentage of instantaneous cell death in ExE/ChEs after dissociation, as determined by the Trypan Blue exclusion test. The percentage of Trypan Blue-positive cells was calculated as a function of total cells. A significant increase in cell death was observed between late-streak ChEs and 4 s.p. ChEs at P<0.05. However, there was no significant difference between early-streak ExEs and late-streak ChEs at P>0.05. Error bars indicate s.e.m.