Figure 5.

Effect of sectioning plane on apparent collagen orientation 3 weeks after coronary ligation in the rat. A Schematic showing location and orientation of sections. LV was divided into 4 transverse rings, and the apical ring sectioned perpendicular to the epicardium, starting from the basal side; dotted rectangle indicates approximate region shown in panel B. The adjacent ring was sectioned parallel to the epicardial surface, to provide another view of the same region of the infarct. B Collagen is arranged in planes parallel to the epicardial surface; in short-axis sections of the heart, it therefore appears highly aligned in the circumferential direction. C Sections parallel to the epicardial surface show the orientation of the collagen in the circumferential-longitudinal plane; following coronary ligation, collagen fibers are oriented randomly in this plane. Sections stained with picrosirius red and imaged through a 10x objective under circularly polarized light.