Histological characteristics and analysis of the myocardium in the diabetic and control rats after 20 weeks. Top panel (A), Masson's trichrome staining showed no evidence of myocardial fibrosis in both groups. Cardiomyocytes were smaller in the diabetic animals (upper right). Lower panel (B), the histological photographs (A) were subsequently converted to 8-bit grey scale images (not shown) and an appropriate threshold was chosen in order to visualize the capillaries only (black and white images, B). The percentage capillary area and capillary diameters were lower in the diabetic rats compared to controls (lower right). Magnification at 400× (A and B), scale bar is 100 μm, *P < 0.05.