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A method for quick-freezing live muscles at known instants during contraction with simultaneous recording of
1Laboratorio de Biofísica del Músculo, Instituto Venezolano de Investigaciones Cientificas, Caracas, Venezuela.
Abstract:
We have developed a quick-freezing method, using a copper block cooled with liquid helium or nitrogen, which permits us to freeze muscles without any cryoprotectant at predetermined, precisely measured points in the recorded tension time-course of a single twitch or tetanus. Our aim is to arrest structural intermediates of the cross-bridge cycle for observation in the electron microscope. Chemically stimulated, demembranated muscles as well as electrically stimulated, live muscles can be frozen on the same apparatus. Good freezing of relaxed and contracting muscles has been obtained to a depth of 10-20 microns, with excellent structural preservation after freeze-substitution.