Electron microscopic study on the hepatic sinusoidal wall and the fat-storing cells in the normal human liver

Ultrastructure of the hepatic perisinusoidal cells in man and other mammalian species

Perisinusoidal (P.S.) cells occurring in the spaces of Disse in the livers of normal cats, dogs, miniature pigs, albino rats, human adults and children were examined by electron microscopy. The ultrastructural details of the P.S. cells and their topographic relationships with hepatocytes, sinusoidal lining cells and reticulum fibers are described. Species differences between P.S. cells were primarily a dissimilarity in lipid content: the main ultrastructural features were the same in all species studied. The P.S. cells of the rat liver displayed only low endocytotic activity, and no phagosome formation following intravenous administration of horseradish peroxidase. The close topographic relationship of the P.S. cells with the intralobular reticulum fibers was reminiscent of the intimate connection between fibroblasts and collagen fibers, or, in cat liver, of the reticulum cell--reticulum fiber association seen in lymphoid organs. Fibroblasts were not found inside the hepatic lobules. These findings support the conclusion that the reticulum fibers of hepatic lobules are produced by perisinusoidal cells which, however, display also other functions.

An ultrastructural study on a new type of hepatic perisinusoidal cell in fish

A new type of perisinusoidal cell containing numerous microfilaments is described for the first time. It is found in abundance in the livers of both marine and freshwater fish. These perisinusoidal cells are situated within the space of Disse and adhere firmly through desmosomes both to sinusoidal endothelial cells and to hepatocytes. The cytoplasmic microfilaments are striking and make these cells readily distinguishable from the perisinusoidal fat-storing cells of Ito. Although the function of these cells is not known, the observations presented here suggest that they may provide a supportive framework within the liver.

Ultrastructure of normal monkey liver

The normal ultrastructure of the liver of rhesus and cynomolgus monkeys is described. A classification of type A and B periportal hepatocytes is introduced together with a discussion of the high incidence of mitochondrial abnormalities. It is suggested that the rhesus monkey is more suitable as an experimental model than the cynomolgus since its liver ultrastructure is less variable.

Fat-storing cells in the liver of rats kept on a low-magnesium diet

While studying the effect of low-magnesium diet on the rat liver considerable proliferation and enlargement of cells, identified as the Ito cells, has been observed. These events were accompanied by the accumulation of lipid substances in the cells. It is the authors' opinion that the lipid accumulation in the Ito cells is due to the deficiency in the lipid metabolising and transporting enzymes. Disturbances in the production of enzymatic proteins may result from the considerable and longlasting magnesium deficiency. The contribution of the fat-storing cells to the collagen biosynthesis is also discussed.

Distribution of organelles and membranes between hepatocytes and nonhepatocytes in the rat liver parenchyma. A stereological study

When biochemical studies on the liver are interpreted, the cells of the sinusoidal area frequently receive little attention because, compared to hepatocytes, their contribution to subcellular fractions is assumed insignificant. A systematic stereological analysis of liver parenchyma was therefore performed in order to determine the distribution of organelles and membranes between hepatocytic and nonhepatocytic cells, namely endothelial, Kupffer, and fat-storing cells. The livers were fixed by vascular perfusion and the data were corrected for systematic errors dur to section thickness and compression. The extracellular space compartment includes the lumina of sinusoids (10.6%), the space of Disse (4.9%), and the bile canaliculi (0.4%). Hepatocytes constitute 78% of parenchymal volume; the nonhepatocytes account for 6.3% and consist of 2.8% endothelial cells, 2.1% Kupffer cells, and 1.4% fat-storing cells. The nonhepatocytes contribute 55% of the volume of lipid droplets in the liver, 43% of the lysosomes, and 1.2% of the mitochondria. Although the nonhepatocytes account for only 8% of the total surface area of parenchymal membranes, they contain 26.5% of all the plasma membranes, 32.4% of the lysosomal membranes, 15.1% of the Golgi apparatus 6.4% of the endoplasmic reticulum, and 2.4% of the mitochondrial membranes. The data demonstrate the extent to which nonhepatocytic organelles can potentially contaminate subcellular fractions used for biochemical studies. Particularly important for the interpretation of studies on lysosomes, plasma membrane, and Golgi apparatus is the finding that an appreciable part of these organelles may be derived from cell types other than hepatocytes.

Enzyme histochemical study on fat-storing cells (so-called Ito's cell) of liver

Inorder to gain a foothold in clarifying the functional significance of fatstoring cells, an enzyme histochemical study on these cells was carried out. Fat-storing cells showed no alkaline phosphatase, acid phosphatase or esterase activity but demonstrated a marked gamma-glutamyl transpeptidase activity suggesting the possibility of its participation in the synthesis of fiber protein. This possibility was further heightened by its remarkable activity noted at the site of progressive fibrosis. Fat-storing cells under a normal condition partake in the formation of fibers supporting the sinusoidal wall, and under an abnormal condition gradually change their shape with loss of fat droplets and then transform into fibroblast-like cells closely related to the progress of fibrosis.

Extravascular cells within the perisinusoidal space of the avian liver

Ultrastructural studies of the perisinusoidal space in the avian liver have demonstrated the presence of 2 extravascular cell types--a fat-storing cell and a free mesenchyme cell or histiocyte. This latter cell type is capable of participating in the formation of a bile canaliculus with the hepatic parenchymal cell. The possibility of the fat-storing cell differentiating from the histiocyte is suggested.

Vinblastine-induced ultrastructural changes in perisinusoidal cells of the rat liver

Vinblastine, given intravenously to rats, leads to disappearance of microtubules, formation of paracrystalline inclusions and accumulation of fat droplets in the cytoplasm of the perisinusoidal cells of the liver suggesting that microtubules of the perisinusoidal cells play a role in lipid metabolism.

Histological effects of lipids on the liver and spleen of mice

Lipids administered by the intravenous route produced ultrastructural changes in the liver and spleen of mice. Treatment with tricaprin resulted in prominent and enlarged Kupffer cells possibly with increase numbers of dense bodies. Cholesterol oleate was found within Kupffer cells and splenic macrophages. The Kupffer cells were distended by lipid and obtruded on the sinusoidal lumen; similar changes were seen in the macrophages of the red pulp and marginal zone of the spleen. Cholesterol oleate delayed but did not prevent eventual phagocytosis or colloidal carbon; the spleen contained much more carbon than usual after treatment with this substance. Treatment with ethyl palmitate resulted in diminished retention of carbon in both liver and spleen; this lipid, unlike tricaprin or cholesterol oleate, was cytotoxic to both macrophages and lymphocytes.

Types of 'reticulin' antibodies detected in human sera by immunofluorescence

Reticulin antibodies have been classified by immunofluorescence into five types reacting with distinct antigens of intra- and extracellular components in mesenchyme. Two types of fibrillar antigens can be distinguished on the basis of the staining patterns, anatomical distribution, and species specificity. A third antibody reacts with either small fibres, amorphous proteins, or mucopolysaccharides lining the hepatic sinusoids (ground substance antigens). In addition, at least two kinds of intrasinusoidal cells show cytoplasmic fluorescence, ie, Kupffer cells and glass-adherent, blood-borne cells antigenically related to peritoneal macrophages. Some sera may contain antibodies reacting with sinusoidal endothelial cells though this has not yet been proven. It has been confirmed that all these distinct antibodies related to reticulin antigens are most frequent in dermatitis herpetiformis and coeliac disease, but they are also found with increased frequency in chronic heroin addicts and in rheumatoid and Sjögren's syndromes. About 5% of normal individuals had such antibodies and no significant increase could be demonstrated in autoimmune disorders or in liver cirrhosis. The antibodies appear to be stimulated by bacterial or nutritional antigens and are likely to represent anamnestic responses rather than direct cross reactions with a multiplicity of foreign antigens.

Mononuclear phagocytes (Kupffer cells) and endothelial cells. Identification of two functional cell types in rat liver sinusoids by endogenous peroxidase activity

The fine structural characteristics and phagocytic properties of peroxidase-positive and peroxidase-negative cells in rat hepatic sinusoids were investigated. Cells with a positive peroxidase reaction in the endoplasmic reticulum and the nuclear envelope make up approximately 40% of cells in rat hepatic sinusoids and have abundant cytoplasm containing numerous granules and vacuoles, and occasional tubular, vermiform invaginations. After intravenous injection of colloidal carbon, the luminal plasma membrane of these cells shows continuous sticking of carbon, and there is evidence of avid phagocytosis of colloidal carbon particles. Peroxidase-positive cells are the only cells in hepatic sinusoids which phagocytize large (0.8 micro in diameter) latex particles. In contrast, the peroxidase-negative endothelial cells, which make up 48% of cells, have scanty perinuclear cytoplasm and organelles, and their long cytoplasmic extensions that form the lining of the hepatic sinusoids have fenestrations; these cells ingest small amounts of colloidal carbon, principally by micropinocytosis, exhibit no sticking of carbon particles to their plasma membranes, and do not ingest the larger (latex) particles. The so-called fat-storing cells are peroxidase negative and totally nonphagocytic. The peroxidase reaction thus distinguishes the typical mononuclear phagocytes or Kupffer cells of rat liver from the endothelial-lining cells.