Ratio increases in [Ca2+]i from head and flagellum regions (measured in discrete regions of interest as indicated). Images acquired at 40 frames per second with 25-ms individual frame exposure time. (A) Typical spontaneous fluctuations in [Ca2+]i observed in resting sperm. Images above graphs are intensity images; images below graphs are ratio images against the frame immediately before the spontaneous increase occurred. (B) Typical response of an individual sperm to addition of speract to a final concentration of 125 nM. Images above graphs are intensity images; images below are ratio images against the frame immediately before speract addition. Note the markedly higher intensity of the head compared with the tail and that the fold increases in head and tail are comparable.
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