Abstract
In general, it is known that the insect egg is very difficult to prepare for transmission electron microscope (TEM). Especially, the one of the most difficult specimen is the mature eggs of silkworm, Bombyx mori. It is important that the chorion was removed gently by the needles before fixation, and the processes of dehydration and substitution were spent thoroughly by the conventional method. These samples could be easy to obtain the ultrathin sections, but there were no structures in the yolk cell cytoplasm which are thought to be an artifact by preparation process. The high-pressure freezing in combination with the freeze substitution methods were examined to observe the ultrastructure of B.mori egg without losing yolk components. Many lipid droplets and glycogen granules were well preserved in the yolk cell cytoplasm. However the ultrastructure of yolk cell cytoplasm in the prefixed egg with chemical fixative before freezing tended to be damaged, compared with that of the non-fixed egg. The ultrastructure of yolk cell cytoplasm may be influenced by chemical fixation. It is demonstrated that the high-pressure freezing in combination with the freeze substitution methods are suitable for the difficult specimens to prepare by the conventional preparation methods for TEM.
