Insect tissue is often difficult to prepare for electron microscopy because of the impenetrable barrier surrounding the body tissues. Drosophila salivary glands have been used for numerous studies because of the large size of the cells and their large polytene chromosomes. Early TEM studies of salivary glands used a protocol that took several days. We were able to achieve excellent preservation and good ultrastructure in Drosophila salivary glands and imaginal discs from Stage L3 larvae using microwave processing in a protocol requiring less than 2 hours.
We used a Pelco Laboratory microwave (model #3451) equipped with a Cold Spot, Steadytemp chiller/recirculator run at 15° C, and vacuum chamber (Ted Pella, Mountain Lakes, CA). The heads and attached salivary glands were removed from the animals and placed in PBS. The tissue was transferred to Pelco prep-eze specimen holders (#36157) for ease of handling. Our goal was to use the microwave effect, not the heating effect, to prepare the tissue.