Demonstration of uniform capillary basal lamina thickness by computer technology.

Blood capillaries are assumed to be circular cylinders composed of an inner layer of endothelial cells surrounded by an acellular uniformly thick basal lamina. The capillary basal lamina is the structural and functional interface between the capillary endothelial cells and the adjacent extracellular matrix, important in growth and control mechanisms of the endothelial cell. Capillaries examined in electron micrographs are cut randomly and a projected image of a capillary other than perpendicular to its long axis will produce artifactual thickening of the assumed uniformly thick basal lamina. We have developed an interactive computer program to determine the thickness of the capillary basal lamina that corrects the thickness resulting from the sectioning artifact. We have applied this methodology to demonstrate that the basal lamina of the pancreatic capillaries of the rat are uniformly thick.