Ultrastructural details as revealed by stereo transmission electron microscopy of high resolution, pre-shadowed surface snd freeze-etch replicas: sample— the drosophila eye
Whereas SEM is useful for studying the surface of objects such as an insect eye at relatively low magnifications, TEM of pre-shadowed replicas has advantages for visualization of the ultrastructural details of surfaces, and freeze-fractured, or freeze-etched specimens.For surface replica studies, fruit flies (Drosophila melanogaster) were glued with glycerol onto a solid copper cap which was then placed on the stage of the Denton freezeetch module. Specimens were frozen by flowing liquid nitrogen into the specimen tube. When specimen temperature reached -105°C, the chamber was evacuated and the shroud cooled to -196°C. With a vacuum of 5 x 10-6 mm Hg, the specimen was warmed to -95°C for 3 to 5 minutes to allow sublimation of any ice which might have condensed on its surface. Specimen temperature was then lowered to -150°C and specimen was shadowed with Pt and coated with carbon.