FIG. 3:. Bcl-2 protein expression in rat blastocysts. A: Immunocytochemistry was performed on a blastocyst after culture for 24 h in 6 mmol/l D-glucose. A primary rabbit antibody against human Bcl-2 and a secondary goat antibody raised against rabbit IgG and coupled to FITC were used. This confocal section shows one strongly Bcl-2+ cell (→) surrounded by less intensively stained cells. Nuclear exclusion of the fluorescent signal is observed in most of the cells. This embryo is representative of a total of 20 blastocysts that were analyzed for Bcl-2 protein expression by immunocytochemistry after culture. B: Confocal section of a cultured blastocyst that was processed through the same immunocytochemical procedure except that nonimmune rabbit IgG was used instead of anti-Bcl-2 antibody (negative control). C: Z-axis projection of the complete series of sections recorded throughout the blastocyst shown in A with the strongly Bcl-2+ cell still prominent (→). D: Z-axis projection of the complete series of sections acquired throughout the blastocyst shown in B. Additional negative immunocytochemical reactions after the omission of the primary antibody (E, Z-axis projection) or omission of both primary and secondary antibodies (F, Z-axis projection) show the low fluorescence signals produced by nonspecific antibody binding and autofluorescence, respectively. The scale bar represents 20 μm in A and B and 45 μm in C, D, E, and F.