Vacuolization and chromatin condensation of cultured sympathetic neurons from dt/dt mice. In semithin sections, the morphological patterns of cultured neurons were normal from wild-type mice (A). However, certain membrane-bounded vesicles in the perikaryon (B) and chromatin condensation (arrowhead, C) could be found in cultured neurons of dt/dt mutants. Aside from sympathetic neurons, a Schwann cell could be also found in this primary culture (arrow, C). At the ultrastructural level, images of cultured neurons reveal autophagic structures and prominent vacuolization from dt/dt mice (D and E). Furthermore, the apoptosis-like characteristic of chromatin condensation with intact nuclear envelope and cell membrane could be observed from dt/dt embryos (D). Multi-membraned autophagosomes could be found in the cytoplasm of dt/dt mutants (E). Scale bars = 20 μm in A-C; 1 μm in D and E.