Fig. 7. Fxna mRNA is expressed in granulosa cells of the developing rat ovary. The mRNA was detected by in situ hybridization using ³⁵S-UTP-labeled Fxna cRNA probe B. (A) Low magnification dark-field image of a PN-48-hour ovary. Cell nuclei were stained with thionin (blue-purple); the hybridization signal in newly formed follicles is seen as white grains. (B) Higher magnification, bright-field image showing the presence of Fxna mRNA (black grains) in granulosa cells, but not oocytes (arrows) of a PN-48-hour ovary. (C) Low magnification, dark-field image of a 21-day-old ovary showing the presence of Fxna mRNA in granulosa cells of both preantral and antral follicles. Arrows point to atretic follicles devoid of hybridization signal. The inset is a higher magnification, bright-field image of the boxed area, showing that the apparent localization of Fxna mRNA to the oocyte is most likely due to an abundance of hybridization signal in granulosa cells of the cumulus oophorus. (D) Bright-field image of C. (E) High magnification, dark-field image of a 21-day-old ovary reiterating the presence of Fxna mRNA in granulosa cells of antral and preantral follicles, and the absence of hybridization (arrows) in oocytes. (F) Bright-field image of E. Scale bars: A, 100 µm; B,E,F, 20 µm; C,D, 400 µm; inset, 50 µm.