The Intimate Association of Nerve Terminals with the Lacteal Endothelium in the Canine Duodenal Villi Observed by Transmission Electron Microscopy of Serial Sections

Abstract

A hitherto undescribed intimate association of the nerve fibers with the central lacteal endothelium in the canine duodenum was demonstrated by transmission electron microscopy of ultrathin serial sections. Around the proximal half of the entire extent of the central lacteal, there exist three to ten unmyelinated nerve fibers 0.1-0.15μm in diameter. Some of these exhibit bulbar swellings (0.7-1.0μm in diameter) which contain small clear vesicles (30-35nm in diameter) and/or rather large vesicles (60-90nm) with electron-dense cores (40-60nm). Most of the bulbar structures of the nerve fibers are in contact with or surrounded by the central lacteal endothelial cells. These results suggest the existence of a neuronal control over the activity of the lacteal endothelial cells.