Observation of the Primo Vessel Approaching the Axillary Lymph Node with the Fluorescent Dye, DiI.

The primo vascular system (PVS) floating in lymph fluid has mostly been observed in large caliber ducts around the caudal vena cava and the thoracic duct of rabbits, rats, and mice. But the PVS has not been traced up to the lymph nodes. It has not been established whether the PVS leaves the lymph vessel through the lymph vessel wall or it enters the lymph nodes. Therefore, observing the PVS entering a lymph node, for example, the axillary node, is desirable. In the current work, we traced the PVS approaching up to the surface of axillary node of a rat. The method used for this study was based upon a method that was recently developed to detect the PVS in the lymph duct from the inguinal to the axillary nodes in the skin of a rat by injecting Alcian blue into the inguinal node. However, the Alcian blue blurred near the lymph nodes and tracing the PVS up to the lymph nodes has not been possible. The current method clearly showed the PVS approaching the axillary node.