The specimens were immediately placed in Tyrode's
solution and moderately inflated with the solution. They were then immersed in a freshly prepared ZIO mixture made of 0.4% OsO 4 and 2.4% ZnI 2 for 4-6 h at room temperature [23]. After rinsing in several changes of distilled water, the muscle layers were carefully peeled off under a dissecting microscope to make whole-mount preparations of the circular and longitudinal muscle layers attached to the myenteric plexus. Then the specimens were photographed in a Nikon photomicroscope, and they were subsequently cut into small pieces (approx. 2-3 mm) and processed for transmission electron microscope examination [30]. The specimens were block-stained with a 3%
aqueous uranyl acetate solution, dehydrated in a graded series of ethyl alcohols and embedded in Epoxy resin. Thin sections were cut and double-stained with 3% uranyl acetate followed by lead tartrate, and were examined through
a JEOL 100C electron microscope.