High-Voltage Electron Microscopy for Insect Neuroanatomy

Abstract

In 1962 Dupouy and Perrier described a transmission electron microscope with an accelerating voltage of one million volts (one megavolt = 1 MV). That achievement possibly set a standard for HVEM and today “high voltage” is regarded as that in the megavolt range. Voltages in the 100 to 1000 kV range have been used for neurobiological material (e.g. Shelton et al. 1971) with some success and a 500 kV scope was built in the U.K. as early as 1952 (Hirsch 1974). The world leader in megavoltage appears to be the 3 MV instrument in Toulouse, France although Meek (1976) mentions that the range extends to 10 MV. Nine other countries (six of them European) have megavolt microscopes. Present commercial models have been made possible by advances in electron optics and generators and accelerators largely provided by laboratories in France, the U.K. and Japan. Currently 55 such microscopes are in service, 14 of which are located in the U.S.A. (King et al. 1980).