Viral particles of ZAM are restricted to the apical end of the follicle cells in a homozygous fs(2)A17 environment. A, The follicle cell/oocyte interface of a U-line stage 9 ovarian follicle is reminded : Viral particles revealed by anti-gag antibodies are detected along the apical end of the follicle cell cytoplasm, on the vitelline membrane and, to a minor extent, in the cortical oocyte. Yolk granules are clearly detected as dark grey circles within the ooplasm. An enlargement of the area defined by the black rectangle is presented below Fig. A. B, In a homozygous mutant fs(2)A17, viral particles accumulate in the follicular epithelium, while the vitelline membrane and the oocyte have no viral particles. No yolk granules are visualized within the ooplasm of this mutant line (Scale Bar, 330 nm). An enlargement of the area defined by the black rectangle is presented below Fig. B. C, A region of the follicle cell cytoplasm containing the Golgi apparatus as tested with anti-Gag antibodies (Scale Bar, 100 nm). D, Histogram expressing the distribution of gold anti-gag tagged grains detected in a U-line bearing or not the fs(2)A17 mutation. Gold grains were counted in the follicle cells and the oocyte comprised within a 0.8 × 1.6 μm reptangular frame bridging the perivitelline space. Data were elaborated using an image analyzer. Standard deviations are reported as bars. fc: follicle cell; G: Golgi apparatus; oo: oocyte; Vm: vitelline membrane.