Living and dead cell fractions. A and D: two-dimensional profiles of the PC12 cells stained with calcein AM and PI. Calcein-PI (A) and SSarea-FSarea (D, left), FSarea-FSheight (D, middle) and SSarea-SSheight (D, right). Cells without dye (B) and cells permeabilized by 0.1 % saponin with dye added (C) were used to define the dead cells. Calcein-positive and PI-negative cells (living cells) are represented by blue dots and calcein-negative or PI-positive cells (dead cells) are represented by red dots.