Fig 5. Schematic geometry of nuclei inclinations and intersections.

The blue cylinders represent the lateral view of nuclei of cardiomyocytes with distinct inclination angles. The in-plane intersections of the nuclei (top view) are depicted in red. The long axis of a nucleus is denoted by e, the short axis is denoted by d. The in-plane intersection leads to a long axis denoted by e* and an unchanged short axis d. (A) Parallel (in-plane) nucleus α = 0°. (B) Inclined nucleus. The inclination angle α can be calculated by using a triangle. If α is so small that the cutting plane reaches the end faces of the cylinder, the analytical relation of α, e, e* and d (B) is no longer valid. If a ratio of 4:1 is assumed for the length e and width d for a nucleus, the limit for an accurate calculation of α is about 14°. Calculated angle values below that limit would not be valid. (C) Perpendicular nucleus α = 90°.