Further electron-microscope studies on the human hepatic sinusoidal wall with special reference to the fat-storing...

In biopsy specimens from two normal human livers, fat-storing cells and Kupffer cells were observed by electron microscopy with the following results: 1) In the human Ito cells numerous micropinocytotic caveolae and vesicles occurred either scattered beneath the plasma membrane or fused into short tubules. In the cytoplasm abutting on these structures, minute clusters of glycogen beta-particles were revealed which presumably had been synthesized in the local cytoplasm from carbohydrate (glucose) ingested by pinocytosis. 2) Lipid droplets (vacuoles) were formed within the accumulations of the glycogen beta-particles. These findings support the view that the glycogen synthesized in the Ito cells may represent a transitional compound in the process of lipid synthesis from carbohydrate. 3) Among lipid vacuoles, electron-dense droplets equally large were found, often containing electron-lucent areas in their center. On the surface of these dense droplets, compact clusters of glycogen particles adhered as if they might have permeated into the droplets. These droplets may possibly be immature lipid droplets retaining chemical properties of the glycogen in their superficial part; they remained insoluble during the preparation procedures for ultrathin sections. 4) The occurrence of the worm-like structure has for the first time been revealed in the human Kupffer cells. Besides its short tubular profiles, a more complex structure was demonstrated.