Fig. 3. Apoptosis of striated muscle, notochord, epidermis and tunic cells 26 hours post-fertilization. (A) Superposition of TUNEL and wheat-germ agglutinin (WGA) labeling (apoptotic nuclei appear in green, tadpole in red). Double arrowed line indicates the level of the semi-thin section shown in B. (B) Transverse section performed in the tail observed using Nomarski differential-interference optics. One of the six muscle cells was clearly replaced by apoptotic body (ab) (T, tunic; TC, tunic cell; SM, striated muscle cells; NC, notochord). (C) Higher magnification of the apoptotic body shown in the rectangle in B (EP, epidermis). (D,E) Extracellular muscle apoptotic bodies, one with large vacuoles (lv) and a nuclear fragment (nf) containing condensed chromatin (cc). (E) At later stage of apoptosis, nuclear membrane disappears around the condensed chromatin. (F) Striated muscle cell at earlier stage of apoptosis. Note the presence of large vacuoles (lv) around the nucleus, the chromatin condensation (arrow) and the well preserved mitochondria (m). (G) NC showing chromatin condensation (arrow). (H) Highly vacuolated TC with condensed nucleus (arrow). Note the importance of the endoplasmic reticulum (er) in cytoplasm of epidermal cells (EP). (I) Typical feature of apoptotis in epidermal cell. Nuclear fragments (nf) containing condensed chromatin (cc) are wrapped by multiple membranes (mm). The membranes seem to be derived from endoplasmic reticulum as suggested by the presence of ribosome-like particle (rp, arrowhead). Some vacant spaces (v) appear to grow between the wrapped fragment resulting in their separation. Scale bars: 180 µm in A; 10 µm in B; 4 µm in C; 1.7 µm in D; 1.6 µm in E; 2.7 µm in F; 3 µm in G,H; 1.2 µm in I.