Studies on fluorescent granular perithelium (F.G.P.) of rat cerebral cortex - especially referring to morphological changes in aging.

In this paper, the granule laden cells localizing around fine vessels in cerebral cortex were investigated with fluorescent, light and electron microscopes using Wistar rats. These cells were designated as fluorescent granular perithelial cells (F.G.P.). The findings obtained in this study were summarized as follows; 1. The F.G.P. were one of essential components of cerebral vessels and separated clearly from nervous tissue by a basal lamina. They were often observed at bifurcating regions of fine vessels. 2. The F.G.P. seemed to differentiate morphologically around birth, and the specific granules to them began to emit yellow fluorescence at second week and attained to a definite level of fluorescence intensity at eighth week. Microfluorometrically, the peak of emission stood at 530 micrometer. Accompanying with a growth of animals, eosinophilia of granules became strong. Sudanophilic areas in the F.G.P. were limited to a periphery of granules. Anisogranularity was evident in old rats age second and third year. 3. Electronmicroscopically, the specific cytoplasmic organelles in the F.G.P. were round electron opaque bodies and vesico-tubular system or sac shaped smooth surfaced endoplasmic reticula. The electron opaque bodies appeared clearly at second week after birth, and changed their profiles and contents with aging of rats. In old rats, they looked porous and honeycomb like structure, and sometimes, whole cytoplasm of the F.G.P. was occupied with these structures. Some sac shaped endoplasmic reticula contained less intense material in one side and seemed to be associated with a formation of electron opaque bodies. Further, it was very interesting that the extensions of some F.G.P. encircled completely the entire circumferences of cerebral vessels. It looked as if fine vessels would penetrate into the F.G.P. 4. After administration of major tranquilizers and prednisolone, fluorescence and eosinophilia of intracellular granules decreased moderately, and the other drugs, - vitamins E and B - enhanced the both. 5HT and 5HTP enhanced the fluorescence, but suppressed the eosinophilia. From the findings mentioned above, the F.G.P. were expected to play an important role in a transport of nourish substance from fine vessels to neurons, and in a removal of some products in the extracellular spaces of central nervous system.