Discovery of a novel fibrous tissue in the spinal pia mater by polarized light microscopy.

Abstract It is very well known that spinal meninges are composed of three layers, dura, arachnoid and pia mater, and that the main components of pia mater are collagen and reticular fibers. However, the distribution of those fibers has not been extensively investigated but just described as a mesh of fibers. In this study, we detected novel structures, which are composed of unidirectionally arranged fibers, in a rat spinal pia mater by using a polarized light microscope. They were seen as three parallel lines, one of which ran along a posterior spinal vein and the rest two of which ran along a pair of posterior spinal arteries. Histological analysis including Masson's trichrome, picrosirius-red staining, Gordon & Sweet's staining and immunohistochemistry with anti-collagen type 1 and 3 antibodies uncovered that they are mainly composed of collagen fibers and some reticular fibers. In addition, a putative primo vessel was detected in the novel fibrous tissue, which was proven out to be different from a blood vessel. In conclusion, we report a newly detected fibrous structure in the spinal pia mater, which may contribute to provide tensile force to the spinal meninges and to harbor the primo vascular system inside.

Observation of a Flowing Duct in the Abdominal Wall by Using Nanoparticles.

The primo vascular system (PVS) is being established as a circulatory system that corresponds to acupuncture meridians. There have been two critical questions in making the PVS accepted as a novel liquid flowing system. The first one was directly to show the flow of liquid in PVS and the second one was to explain why it was not observed in the conventional histological study of animal tissues. Flow in the PVS in the abdominal cavity was previously verified by injecting Alcian blue into a primo node. However, the tracing of the dye to other subsystems of the PVS has not been done. In the current work we injected fluorescent nanoparticles (FNPs) into a primo node and traced them along a primo vessel which was inside a fat tissue in the abdominal wall. Linea alba is a white middle line in the abdominal skin of a mammal and a band of fat tissue is located in parallel to the linea alba in the parietal side of the abdominal wall of a rat. In this fat band a primo vessel runs parallel to the prominent blood vessels in the fat band and is located just inside the parietal peritoneum. About the second question on the reason why the PVS was not in conventional histological study the current work provided the answer. Histological analysis with hematoxyline and eosine, Masson's trichrome, and Toluidine blue could not discriminate the primo vessel even when we knew the location of the PVS by the trace of the FNPs. This clearly explains why the PVS is hard to observe in conventional histology: it is not a matter of resolution but the contrast. The PVS has very similar structure to the connective tissues that surround the PVS. In the current work we propose a method to find the PVS: Observation of mast cell distribution with toluidine blue staining and the PN has a high density of mast cells, while the lymph node has low density.