Figure 4. Degradation of either RB or POS by Sertoli cells. In (A), electron microscopy analysis showing intact RB, entered Sertoli cell cytoplasm along with partly degraded RB inside degradative vacuoles at different stages of their maturation, filled with electron-dense degradative remnants (arrowheads). Large portions of intact and partly degraded (B–K) Rhodopsin-positive POS membranes (B–E) are detected within Sertoli cell cytoplasm. Intact POS, entered the cytoplasm, are wrapped by double membranes (F and G) and may be directly conveyed into degradative vacuoles (I) (arrowhead), which further mature into late degradative vacuoles delimited by single membrane (B–I) (arrow). The arrow in (F) indicates partly degraded POS fragments, devoid of plasma membrane, wrapped by a phagophore. The arrow in (G) indicates triple membrane; in newly ingested POS, consisting of POS plasma membrane wrapped by a phagophore. Apart from single-membrane limited degradative vacuoles, disintegrated POS are found inside double-membrane limited vacuoles (H). Double-membrane vacuoles are surrounded by small lamellar vacuoles (H) (asterisk). Electron microscopy images from RB and POS-treated Sertoli cells show no sign of cell damage in the nuclei or in the cytoplasm. (J) Represents a higher magnificence image of (G) showing double-membrane wrapped plasma-membrane delimited fragments of undegraded POS (arrows). (K) Represents a higher magnification of (H) showing double-membrane wrapped degraded fragments of POS. Abbreviations: ly, lysosome; m, mitochondrion; n, nucleus. Scale bars: (A, B, F, G, H) 1 μm; (C, D, E, I and J) 5 μm.