Fig. 4.

Both round and circus neurectoderm cells demonstrate vitality with responses to caffeine. Cells were loaded with Fluo-3AM, a fluorescent Ca²⁺ indicator, and superfused with medium containing caffeine for 60 sec at the indicated times. Elevations of fluorescence indicate elevations of [Ca²⁺]_i. A, Cells respond to caffeine at 4 hr in culture, demonstrating the presence of loaded Ca²⁺ stores and active intracellular buffering mechanisms. B, There is no significant difference between round and circus cells in baseline fluorescence (arbitrary units) and percentage of cells responsive to 50 mm caffeine. Amplitudes of responses to 50 mm caffeine are significantly different but are not different at 100 mm caffeine (Mann–WhitneyU tests for all comparisons). Values are from four cultures at 4–6 hr.