Primo-vessels and Primo-nodes in Rat Brain, Spine and Sciatic Nerve

Visualization of primo-nodes and primo-vessels in the rat brain. (A) Primo-nodes (thick arrow) and primo-vessels (two thin arrows) were visualized in the arachnoid mater. Capillaries below these primo structures were notably not stained. (B) A primo-node was visualized in the fourth ventricle. (C) Networks of primo-vessels (arrow) on the surface of the cerebellum. (D) One of the networks (dotted rectangle) is magnified and reveals that primo-vessels form fine networks (arrows).

Visualization of primo-nodes and primo-vessels in the rat spinal cord. (A) A small primo-node (black arrow) with primo-vessels (white arrows) was visualized around the perineurium of the spinal cord. (B) A large primo-node (thick arrow) with a primo-vessel (thin arrow) was also found around the perineurium of the spinal cord.

Visualization of primo-vessels in the perineurium, endoneurium and epineurium of a rat sciatic nerve. (A) primo-vessels (four arrows) were visualized in the perineurium. (B) A primo-vessel (two arrows) was visualized; however, a blood capillary (two triangles) inside the perineurium was not stained by Trypan blue. (C) A primo-vessel (two arrows) was visualized around the endoneurium of the sciatic nerve. (D) Primo-vessels (four arrows) were visualized in the rat epineurium. Blood capillaries were not stained by Trypan blue.

Distribution of F-actin and nuclei of primo-vessels in rat sciatic nerve. (A) Fluorescence microscopic image of 4′,6-diamidino-2-phenylindole, or DAPI-stained nuclei of the sciatic nerve (triangles) and a primo-vessel (between dotted lines). The inset shows a primo-vessel (between dotted lines) containing F-actin (green fluorescence) stained by phalloidin; however, the sciatic nerve (triangles) has no clear F-actin signal. (B) Confocal laser microscopy clearly demonstrates a fine primo-vessel consisting of a bundle of F-actin (arrow, green fluorescence) with DAPI-stained nuclei (blue fluorescence) in the sciatic nerve of a rat. Nerve fibers scattered around the primo-vessel emit a weak signal due to F-actin on its boundary.