Characteristic Features of a Nerve Primo-vessel Suspended in Rabbit Brain Ventricle and Central Canal

Representative pictures of a nerve primo-vessel (NPV; Bonghan duct) in the brain ventricle and central canal of the spinal cord in rabbit. (A) The NPV, indicated by four arrows, lies in the mesencephalic aqueduct and fourth ventricle of rabbit brain, suspended by an acupuncture needle indicated by a dotted arrow. Scale bar, 2 mm. (B) Opened central canal of rabbit spinal cord before staining. There is no structure visualized inside the opened central canal. Scale bar, 50 μm. (C) After hematoxylin staining, NPV (arrows) emerges in the central canal of the rabbit spinal cord. Scale bar, 100 μm.

(A) 1,1′-dioctadecyl-3,3,3′,3′-tetramethylindocarbocyanine perchlorate (DiI) stained nerve primo-vessel (NPV; Bonghan duct). DiI staining in NPV appears as aligned parallel dots. Several DiI stained dots are shown using rectangles. Scale bar, 10 μm. (B) Transmission electron microscopic image of NPV corresponding to a rectangle seen in (A). Dots stained by DiI are microparticles. Scale bar, 500 nm. (C) Magnified image of dotted rectangle in (B) shows empty vesicles and material-containing vesicles. Scale bar, 200 nm.

Confocal laser scanning microscopic image of a nerve primo-vessel (Bonghan duct) stained by acridine orange, which binds DNA. DNA stained primo-vessel was optically sectioned from (A) to (D). Bright green signal indicates DNA which varies according to size and distribution. (B,C,D) Triangles indicate a cluster of DNA similar to that in the nucleus. Arrows indicate DNA particles in parallel. One tiny DNA green signal in (C) is intentionally marked by a dotted square for comparison with a high electron density structure taken using high voltage electron microscopy, as in Figure 4. All scale bars, 10 μm.

High voltage electron microscopic image of a high electron density structure in a nerve primo-vessel (Bonghan duct). This round structure consists of a double outermost membrane which envelops the high electron density materials.

Confocal laser scanning microscopic images of nucleus (red), stained by propidium iodide, enveloped by helix-shaped actin (green), stained by phalloidin. Clear images of helix-shaped actin are indicated by arrows. The primo-vessel sample was optically sectioned using 2.4 μm steps. Scale bar, 10 μm.