Fig. 2. Variations of the mitochondrial concentration of NADH ([NADH]_mito) in ascidian eggs (Phallusia). (A) Images of NADH of an egg before fertilization (left, t=0 minutes) and at the end of meiosis (right, t=21 minutes 40 seconds). The gray lines are artefacts caused by the CCD camera. In the `time-image' (center), time (minutes) is measured on the x-axis and the y-axis corresponds to the extracted lines of the mitochondria-rich domain (a-b,a'-b'; see Materials and Methods). The varying length of each extracted line of mitochondrial NADH is due to actomyosin driven cortical contractions traversing the egg during the activity of both Ca²⁺ wave pacemakers (Roegiers et al., 1999). The periods of activity of the two pacemakers are indicated by arrowheads; the scale goes from black for low [NADH] values to white for high [NADH] values. (B) Typical [NADH]_mito variations observed after fertilization of an egg measured in the middle of the mitochondria-rich domain [between the two white horizontal lines in A (center)]. [NADH]_mito increases during the period of activity of each Ca²⁺ wave pacemaker (PM1 and PM2) (n=8). (C) Variations of [NADH]_mito after perfusion of an unfertilized egg with the mitochondrial inhibitors CN^- (2 mM) and FCCP (1 µm).