Fig. 7.

Decrease in number of synaptic vesicles and accumulation of large endosome-like structures in nerve terminals of dap160 ΔAB rescued larvae. (A,B) Electron micrographs of control (A) and ΔAB (B) nerve terminals show that at rest the density of synaptic vesicles is decreased in the distal pool of ΔAB nerve terminals (quantified in K). (C,D) Following high K⁺ stimulation at elevated temperature, the number of synaptic vesicles is decreased in both proximal and distal zones in ΔAB nerve terminals (quantified in L). Endosome-like profiles are also observed (arrow in D indicates one endosome-like profile). (E–H) Higher magnification images show that endosome-like profiles are often connected to each other (arrowheads in E and G) and to the plasma membrane (arrows in F and H). (I) Image showing example of large endosome-like structure (arrow). (J) The number of large endosome-like profiles (>150 nm) is increased in ΔAB following stimulation. (K,L) Quantification of synaptic vesicles in the proximal and distal zone at rest (K) and following stimulation (L). (M) The number of docked vesicles and endocytic pits were not significantly different in control and ΔAB. T, T-bar; m, mitochondrion; sv, synaptic vesicle; el, endosome-like profile; ax, axoplasm. Bar graphs indicate mean + s.e.m. **P<0.01; ***P<0.001 using Student's t-test. Scale bars: 0.5 µm (A–D); 0.1 µm (E,G,H); 25 nm (F); 250 nm (I).