Three of resident cells of the hepatic sinusoidal wall and in connection with these, the hepatic parenchyma were electron microscopically observed in four species of birds. Avian hepatocytes were characterized by densely packed, abundant large mito-Hepatic Parenchyma and Sinusoidal Cells in Avian Livers 327

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Summary.Hepatic sinusoidal cells in the guinea pig were examined by transmission electron microscopy (TEM). A meandering Canalicular system was detected in the sinusoidal endothelial cell both in thicker portions of cytoplasmic extensions and in small areas of the perikaryon.It consisted of meandering canaliculi with vacuolar expansions and constrictions, which penetrated the endothelial cytoplasm, forming as a whole a network.The canaliculi possessed more than two openings which usually communicated with the sinusoid, but occasionally poured themselves into the Disse's space.This network of canaliculi seems to permit infiltration of blood plasma. The "pored domes" recorded by FUJITA and his collaborators on the glomerular endothelium of the rat and rabbit kidney were also revealed on the perikaryonal cytoplasm of the sinusoidal endothelium of guinea pig liver. Osmium-blackened lipid droplets were found in the sinusoidal endothelium, which suggested the release of lipid into the sinusoid. Short-term administrations of excessive vitamin A exerted no influence on the endothelial lipid droplets. The guinea pig is a rodent species which stores a very small amount of lipid droplets in its fat-storing cells and the so-called empty fat-storing cells were frequently detected. A single cilium was often found in the fat-storing cells in the guinea pig as in other species.The majority of recent electron microscope studies on the hepatic sinusoidal cells (nonparenchymal cells) have been carried out in rat or mouse livers. Among rodents, however, hepatic sinusoidal cells have been known to vary ultrastructurally from species to species as recently shown by LEEUW et al. (1982b) in their comparative morphological, peroxidase-cytochemical and experimental (latex-bead endocytosis) studies on the Kupff er and endothelial cells in the rat and mouse.Thus, they strongly precautioned against the careless application of rat liver data to other species. The results in vivo obtained by LEEUW et al. (1982b) have further been confirmed by MONTECINO-RODRIGUEZ et al. (1982) in their peroxidase cytochemical study of isolated and cultured Kupffer and endothelial cells from rat and mouse liver. Also the fatstoring cell of Ito is known to show considerable species differences.The light microscopic studies by ITo and his collaborators have revealed that the fat-storing cell in 359