Imaging of electrically induced fast motion by video microscopy and triggered flash illumination

A simple and inexpensive method is described for imaging with video microscopy fast transient events that can be triggered electrically. An electronic system was developed that triggered stroboscopic illumination and generated an electrical step function. The essential feature was precise control of a sub-millisecond time delay between electrical stimulus and the following short pulse of light. With this technique (15 microseconds time resolution, 50 frames/s) different phases of the exocytosis and discharge of nematocysts from Hydra vulgaris can be visualized. It was shown that not only stenoteles, but also desmonemes, can discharge in less than 0.5 ms.