Immunohistochemical analysis of CBS expression in normal dogs of different ages. Retinal cryosections from (A-C) five weeks, (D-F) twelve weeks, (G-I) thirty-one weeks and (J-L) three and a half year old dogs were labeled with antibody against CBS. CBS (red fluorescence) was detected in photoreceptor cells (Inner segment), OPL and GCL/NFL. DAPI was used to stain nuclei (A, D, G and J). C, F, I and L are merged images. (Scale bar: 20 µm; OPL: outer plexiform layer; GCL: ganglion cell layer; NFL: nerve fiber layer; IS: Inner segment layer of photoreceptor cells).