Ultrastructure of the Area Postrema of the Bat / 대한해부학회지

This study was undertaken to investigate the ultrastructure of the neurons, neuroglial cells and capillaries in the area postrema[AP] of the Oriental discolured bat, Vespertilio superans. The AP of the bat was a single midline structure at the most caudal portion of the fourth ventricle. Most neurons in the AP were small cells, but their ultrastructure were similar to the typical neurons located elsewhere in the central nervous system. Astroglial cells and oligodendrocytes were also observed and showed their typical ultrastructure. Ultrastructural features of neurons, astroglial cells and oligodendrocytes were not changed during hibernating cycles. However, microglial cells were only found in the hibernating AP ; these cells were located in the parenchyma and near the blood vessels of the AP. Since the microglial cytoplasm was filled with phagocytotic inclusions, the nuclei of the these cells were eccentrically located. Phagocytotic cytoplasmic inclusions were shown to be composed of a dense irregular peripheral region and the pale round central region. A Large vacant space was often found in the electron lucent central region. Continuous and fenestrated capillaries surrounded by pericytes were found in the bat`s AP. Especially, Phagocytotic inclusions were found in the pericyte cytoplasm of the hibernating AP, and this result supports suggestion that pericytes might be phagocytotic cells. On the basis of the distributions of phagocytotic tells[pericytes and microglial cell], ultrastructure of these cells, morphology of their cytoplasmic inclusions, and the appearance of phagocytotic activity of the pericytes during the hibernating stage when microglial cells were observed, it can be concluded that pericytes may also participates in the formation of rrlicroglial cells. Tanycytes were also found in the bat AP.

Changes in the Serotonin Immunoreactivities of Mucosal Mast Cells Following Vagus Nerve Stimulation in the Rat Gastrointestinal Tract / 대한해부학회지

Changes in the number, the immunoreactivities and the ultrastructures of sero- tonin immunoreactive mucosal mast cells[MMCs] in rat gastrointestinal tracts after vagus nerve stimulation were investigated by using light and electron microscopic immunocytochemical methods. The vagus nerves were electrically stimulated with a square wave pulse generator for a duration of 5 minutes each, a total of 8 times at 2 minute intervals. Serotonin immunoreactive cells of the connective tissues of the gastrointestinal tract were mainly located in the lamina propria, and a small number of the cells were also scattered in the submucosa. By using electron microscopic immunocytochemistry and Wright stain, the serotonin immunoreactive cells of the lamina propria and the submucosa were identified to be MMCs. A few large-sized serotonin immunoreactive connective tissue mast cells [CTMCs], showing strong metachromasia with the Wright stain, were located together with the MMCs in the submucosa of the stomach. In most of the gut regions of the control group, the majority of the MMCs did not show any serotonin immunoreactivities and only a few MMCs showed weak serotonin immunoreactivities. After stimulation of the vagus nerves, the number and the immnu- noreactivities of the serotonin immunoreactive MMCs dramatically increased in all gut regions observed, especially in the small intestines. In the samples treated with the electron microscopic immnunocytochemical methods, hardly any serotonin immunoreactivities were detected in the MMCs of the control group. However, the serotonin imrnunoreactivities of the MMCs were significantly increased after vagus nerve stimulation. The serotonin immnunoreactive products were localized, following vagal stimulation, both in the peripheral matrix of the granules and in the cytoplasm. Also, it was confirmed ultrastructurally that the Golgi complexes were expanded in the MMCs of the vagal stimulation group. The above results suggest that vagus nerve stimulation may activate serotonin biosynthesis in MMCs.