FIGURE 5.

PPO in hindgut is not from hemolymph contamination. A, lysozyme was used as a probe to detect whether there is a physical connection between the hemolymph and hindgut. V-3 silkworm larvae were injected with dead E. coli. The hindguts and its contents were sampled after 12 h and treated as in Fig. 3. Lysozyme was found in plasma but not in the hindguts or its contents by Western blot assay. B, small cells inside HG2 were not labeled by the injected fluorescent beads. The phagocytosed fluorescent beads by hemocytes were used as probes to monitor hemocytes movement (17). After injection of fluorescent beads as previously described (17), circulating hemocytes were observed to have the phagocytosed beads (inset). However, no signal was detected inside the small cells of HG2. The arrow indicates a small cell inside HG2. Some cells became auto-melanized (arrowhead) during the preparation because of PPO activation. The images were merged from those taken using red filter and DIC optics. P: plasma; HG, hindgut; M: muscle; E: large epidemical cells. Bar: 20 μm.