Fine structure of wobbler and WT motor neurons. (A) Terminal stage of WR motor neuron. Note extensive vacuolisation but normal shape of cell bodies and non-necrotic and non-apoptotic nucleus (N). (B) Intact WR motor neuron from contralateral side of same section as in (a) with Nissl-Golgi areas (darker blue areas) within the cell body. (C) Terminal stage of motor neuron death in WR is characterized by extensive vacuolisation but otherwise intact organelle structure, frequency and distribution. (D) Motor neuron from age-matched WT, lysosomes discernible (as in C) as deep-black organelles. (E, F) Camera lucida sketch of wr terminal stage (E) and of intact motor neuron from wildtype (F); vacuoles highlighted in red, lysosomes in blue. (G, H) Earliest changes are observed by clear enlarged vesicles / vacuoles (arrowhead) derived from Golgi apparatus. (I) Later stage of motor neuron death is characterized by massive vacuolisation of Golgi apparatus (arrowheads) and additionally by vacuolisation/dilatation of ER with grey electron dense content (cytoplasm; arrows). (J) Final stage of motor neuron death with numerous and large vacuoles but mainly intact mitochondria. N = nucleus; c = capillary; ah = axon hillock, m = mitochondrion. Scale in B (for A &B), 10 μm; in D (for C & D), in F (for E & F), and J (G-J), 1 μm, respectively.