Study of novel threadlike structures on the intestinal fascia of dogs.

The primo-vascular system was visualized in the mesentery surrounding the small intestine of a dog using Trypan blue. This structure, which was first observed in a rat, formed a network as primo-vessel branches were joined to primo-nodes. Other characteristic features of the primo-vascular system, such as bundles of tubes with fibrous extracellular matrix in a primo-vessel and a broken-line alignment of rod-shaped nuclei along the primo-vessel, were observed. Blood vessels, lymph vessels, and primo-vessels were present in the same mesentery, and they could clearly be distinguished by histological differences.

Fluorescent nanoparticles for observing primo vascular system along sciatic nerve.

The primo vascular system was found in the epineurium along the rat sciatic nerve following subcutaneous injection of fluorescent nanoparticles at the Zusanli acupoint (ST-36). Nanoparticles were injected into the primo-vessel near ST-36 and flowed along the sciatic nerve. Fluorescence revealed a structure in the epineurium that was hardly detectable. Images of the isolated sample stained with 4',6-diamidino-2-phenylindole were captured using confocal microscopy. These images showed the distinctive nuclei distribution and multi-lumen structure of primo-vessels that differentiate them from lymphatic vessels, blood capillaries and nerves. This study demonstrates a new use for nanoparticles in fluorescence reflectance imaging techniques during in vivo imaging of primo-vessels.