Figure 3

Intensity of staining to IGF2 and IGF2R antibodies in the yolk sac trophoblast during the final third of gestation (A). The intensity of staining was measured subjectively as described in the experimental procedures. The bilaminar (BYS) (shaded bars) and trilaminar yolk sac (TYS) (open bars) of matched samples were assessed independently. Samples were grouped into days 19–21 (n = 4), 22–24 (n = 5), and 25–26 (n = 4). Staining intensity to the IGF2 antibody was consistently stronger in the TYS, especially at days 25–26. Staining by the IGF2 antibody was notably lighter at days 19–21 than later stages (days 22 to 26). Staining by the IGF2R antibody did not differ notably between the bilaminar and trilaminar yolk sac, nor were there marked differences corresponding to developmental stage. Intensity of staining by IGF2 and IGF2R antibodies in yolk sac cells (B). Staining intensity was noticeably higher in the trophoblast (Tr) (stippled bars) than in the yolk sac endoderm (En) (striped bars) of the bilaminar (BYS) and trilaminar (TYS) for IGF2, but not IGF2R. The staining intensity represents the average for fetal stages between days 19 and 26 (n = 13). Light background staining with the IgG antibody negative control in the yolk sac endoderm was taken into account when judging the staining intensity of the yolk sac endoderm for IGF2 and IGF2R antibodies.