Time-gated fluorescence imaging of Blepharisma red and blue cells

Time-gated fluorescence images of intact motile red and blue cells of the photoresponsive protozoan Blepharisma japonicum have been acquired, digitized and analyzed by means of a new dedicated micro-video system The spatial and spectral maps of the intracellular distribution of the endogenous fluorophores reveal that red, as well as blue cells fluoresce mainly in the blue-green with a longer lifetime, whereas the vacuoles emit in the red with a shorter decay time Upon breaking the cell membrane, the extruded pigments show a bright short-lived fluorescence in the red, attributed to blepharismin and oxyblepharismin in red and blue cells, respectively The results on fluorescence time-behavior, apparent quantum yields and fluorescence spectral distribution are discussed with respect to the photosignalling function of blepharismin and oxyblepharismin.