ELECTRON MICROSCOPIC STUDIES ON THE AUTONOMIC INNERVATION OF THE HUMAN VAS DEFERENS

Abstract

The intercellular relationships between smooth muscle cells and the arrangements and neuromuscular relationships of autonomic nerves in the submucosa, smooth muscle layers and adventitia of the human vas deferens have been studied light-microscopically, by the histochemical cholinesterase reaction, and electron-microscopically. On the other hand, the spatial relationship between axons and Schwann cells have been examined electron-microscopically by means of PAM (periodic acid-methenamine silver) staining and tannic acid-glutaraldehyde fixation. Materials were taken at 2-3cm distance from the distal portion of the gars epididymica of the human vas deferens. The results were as follows:
1) Many cholinesterase-positive nerves were identified in the submucosa, and formed a plexus along the epithelial lining of the human vas deferens. Many axon profiles containing numerous small agranular and occasional large granular vesicles were confirmed by electron microscopy. These nerves in the submucosa were considered sensory in function.
2) Large cholinesterase-positive and negative nerves ran in the adventitia. Some large unmyelinated axons bundled up by a Schwann cell and by numerous endoneural collagen fibrils electron-microscopically ran within a complete envelope of the perineural sheath. Some myelinated axons which were considered visceral afferent fibres were rarely intermingled with many unmyelinated axons.
3) The distribution of the cholinesterase-positive nerves amongst the muscle layers was sparse. The directions of running of these nerves were generally parallel with each muscle layer.
4) Electron microscopy confirmed that the musculature of the human vas deferens had a rich autonomic innervation. The ramose naked axon not only had the narrowest neuromuscular cleft measuring about 200Å, but also intruded deeply into the smooth muscle cells. The latter axon profile was very rare in the human vas deferens. According to the classification of the synaptic vesicles, a cholinergic axon and a noradrenergic axon were ensheathed with the same Schwann cell rarely.
5) The interrelations between adjacent muscle cells in the human vas deferens were various in type. The adjacent muscle cells issued interdigitated cytoplasmic processes each other, and the bulbous process of one smooth muscle cell intruded into the groove of the other muscle cell. Sometimes, bulbous protrusions (bulbous exfoldings) which were considered to be a mechanism for the transfer of material between muscle cells were observed. Nexus-like junctions were rare, but by the use of glutaraldehyde and osmium tetroxide in this study, the adjacent muscle cell membranes appeared only a single dense line. It is necessary to further study the human vas deferens with regard to “nexus”, using potassium permanganate fixation.
6) The deposits of silver grains, consisting of partially unclear clefts between axolemma and the plasma membrane of Schwann cell, were observed by means of PAM staining. This finding appeared to suggest the existence of glycoprotein in this portion.
7) The gap junction lattice between axolemma and the plasma membrane of Schwann cell was observed by means of tannic acid-glutaraldehyde fixation. This finding was considered to suggest the possibility of electrotonic coupling in this portion.