Fig. 2. Localization of chitin synthase in the epiproct of Periplaneta americana. (A) Cryosections of 10µm were stained with a polyclonal antiserum raised against a conserved region of the Manduca sexta chitin synthase as described previously (Zimoch and Merzendorfer, 2002). Visualization of primary antibodies was conducted with anti-rabbit antibodies (whole molecules) conjugated to alkaline phosphatase. Detection with 5-bromo-4-chloroindolylphosphate and nitroblue tetrazolium was carried out in the presence of 2 mmol l^-1 levamisole to block endogenous alkaline phosphatase activity. (B) Control reaction performed in the absence of primary antibodies. Arrows in A and B mark the apical region of epidermal cells, which are in part detached from the endocuticle as a result of the sectioning procedure (asterisks). Scale bar, 50µm.