Measurements were made of the rigor stiffness of impaled bull sperm flagella. Vanadate-free ATP was found to have a stronger plasticizing action than vanadate-contaminated ATP. Trace amounts of Mg2+ were found to be necessary to relieve the rigor condition by ATP. During the injection of negative electric current into the sperm head, the flagella stiffened, presumably by depletion of Mg2+ from the flagellar interior.

This content is only available via PDF.