ABSTRACT
Since the first appliestions of electric pulses from a Volta pile by Johann Wilhelm Ritter (1776–1810) on tissues of his own body (1), many studies with nerves and muscles have been done. The first evidence for protoplast fusion by electric-field pulses was presented in 1979 and involved plant protoplasts of Rauwolfia and Hordeum (2), and diauxo trophic yeast mutants (3). In the first case, needle electrodes in glass capillaries con trolled by a micromanipula tor were used (Technique A), whereas for the second case a macrochamber with disk electrodes, an exponential pulse, and agglutinating polyethyleneglycol (PEG) was utilized for fusion and subsequent formation of prototrophic colonies (Technique B). Later, a valuable technique was introduced consisting of a microchamber with parallel wire electrodes; it used dielectrophoresis for cell collection and rectangular pulses for electrofusion under microscopic control (Technique C)(6, 7). In all three cases, close contact between the cells to diminish adsorbed water layers and the repulsion of surface charges is the most important prerequisite for successful electrofusion. The initial applications of the three pulse techniques are shown in Table 1 (Figure 1).
