The dependence of nuclear metabolism on the function of the nuclear membrane is not well understood. Whether or not the function of the nuclear membrane is partial or totally responsible of the repressed template activity of human sperm nucleus has not at present been elucidated. One of the membrane-bound enzymatic activities which is concerned with the mechanisms whereby substances are thought to cross cell membranes is adenosintriphosphatase (ATPase). This prompted its characterization and distribution by high resolution photogrammetry on isolated human sperm nuclei. Isolated human spermatozoa nuclei were obtained as previously described. ATPase activity was demonstrated by the method of Wachstein and Meisel modified by Marchesi and Palade. ATPase activity was identified as dense and irregularly distributed granules confined to the internal leaflet of the nuclear membrane. Within the nucleus the appearance of the reaction product occurs as homogenous and dense precipitates in the interchromatin space.
