Fig. 6. Type IV collagen accumulates in dilated ERs in epithelial cells of Hsp47^–/– embryos at 9.5 dpc. (A,B) Sections of epithelial cells of wild-type (A) or Hsp47^–/– (B) embryos were analysed by immunoelectron microscopy using an antibody against type IV collagen. Arrows indicate ERs that contain type IV collagen. Bar, 0.1 µm. (C,D) Large magnification view of the dilated ER in Hsp47^–/– embryos. Arrowheads indicate ribosomes associated with the dilated ER membranes. Note that the ERs of the Hsp47^–/– cells are highly dilated and exhibit large accumulations of type IV collagen. Bar, 10 nm.