Accumulation of oocytes and their remnants in some medullary vessels. Some medullary vessels showed an embolus-like accumulation of ZP+ (HSPZ, blue color) material, either at the structures showing vascular regression, e.g., corpus albicans (CAlb, panels A-C), or without apparent vascular regression (panel D). In some instances, a higher magnification revealed the presence of multiple unstained oocyte nuclei (arrowheads, panels E and F). No hematoxylin counterstain except control staining in panel (C). vl, adjacent vascular lumen. Further details in text.