Fig. 7. _m changes in cells undergoing spontaneous, repetitive [Ca²⁺]_c oscillations. (A) During spontaneous, repetitive [Ca²⁺]_c oscillations (Fluo-4 fluorescence normalized to baseline values, F/F₀, i and iii), individual mitochondria (visualized as punctate TMRE fluorescence, shown in close-up still frames at the time points indicated during [Ca²⁺]_c oscillations, ii and iv) depolarized. Localized fluorescence decreases (depolarizations) are indicated by blue arrows and localized fluorescence increases (repolarizations) are shown by white arrows (images pseudocolored to indicate fluorescence intensity, v). (B) TMRE-fluorescence changes in three individual mitochondria (lower panels) from three separate cells were of varying magnitude and duration, and did not correspond directly to changes in [Ca²⁺]_c (upper panels, Fluo-4 fluorescence, F/F₀). Scale bars, 5 µm.