Fig. 2

Histological features of AVA-like vessels in the regressed CL of cows. The regressed CL of cows is filled with AVA-like vessels. Large vessels with an external diameter of more than 200 μm are found in the periphery of the CL (arrows in a) and vessels of various sizes are distributed throughout the CL parenchyma (a). Vessels with a diameter of 100–200 μm resemble typical AVA possessing several layer of epithelioid cells in the walls and narrow lumens (asterisks in a, b). Ultrastructural observations under a TEM show how the epithelioid shape of cells in wall of an AVA-like vessel, each possessing a basement membrane similar to smooth muscle cells (asterisks in c). The lumen of small-sized vessels is narrow, showing its contractive condition (d, e). e: endothelial cells