In situ hybridization of BMP-6 mRNA in ovaries of adult cycling rats. Brightfield (A, C, D, E, G, I, K) and Darkfield (B, F, H, J, L). A, B: Sections from DI 1100 h ovary (4X); positive GC in GF; preantral follicles with positive oocytes and GC (arrow heads); positive CL-I and positive OSE. C: Artery in mesovarium at P 1000 h (40X); positive endothelium. D: Early secondary follicle at E 0200 h (40X) with weakly positive oocyte; germinal vesicle (GV). E, F: Early secondary follicle at E 1000 h (20X); positive oocyte; positive peripheral membrana GC (arrow heads); negative corona radiata; G, H: Ovulating follicle at E 1000 h (4X) showing positive oocyte and negative MGC, CC, and PA cells. I, J: Atretic follicle (AF) at E 1000 h (10X) with positive oocyte (O) and GC. K, L: New CL-I at DI 1100 h (20X) showing positive TE and OSE.