Fig. 4. Exogenous prostaglandin D₂ masculinises female urogenital ridges in culture. Female urogenital ridges were cultured with or without exogenous prostaglandin D₂ in the culture medium, fixed in Bouin’s solution and sections stained with Haematoxylin and Eosin. (A-D) Sections are oriented with the mesonephros (m) on the left and the genital ridge (g) on the right. (A) Control female urogenital ridge cultured without prostaglandin D₂. (B-D) Female urogenital ridges cultured with prostaglandin D₂. (B) Disorganised cord-like structures in the masculinised region of the genital ridge (), and the ovarian region () of the genital ridge. (C) Eosinophilic cells bulging from the genital ridge into the mesonephros (arrow). (D) The mass of gonadal eosinophilic cells is located along the boundary with the mesonephros (arrow). (E-G) Higher magnification of female urogenital ridges cultured with prostaglandin D₂. Thick arrows labelled PSG indicate prospermatogonia, peritubular myoid-like cells are indicated with small arrows and Sertoli-like cells are indicated with arrowheads. (E) A disorganised cord in the masculinised region of the urogenital ridge shown in B. (F,G) Sections located at the edge of the bulge of eosinophilic cells spilling into the mesonephros, from the urogenital ridge shown in C. Scale bars: 50 µm in A-D; 10 µm in E-G.