Lysosomes Of Parenchymal Cells Research Articles

Localization of cathepsin D in rat liver. Immunocytochemical study using post-embedding immunoenzyme and protein A-gold techniques.

Light and electron microscopic localization of cathepsin D in rat liver was investigated by post-embedding immunoenzyme and protein A-gold techniques. By light microscopy, cytoplasmic granules of parenchymal cells and Kupffer cells were stained for cathepsin D. Weak staining was also noted in sinusoidal endothelial cells. In the parenchymal cells many of positive granules located around bile canaliculi. In the Kupffer cells and the endothelial cells, diffuse staining was noted in the cytoplasm in addition to granular staining. By electron microscopy, gold particles representing the antigenic sites for cathepsin D were seen in typical secondary lysosomes and some multivesicular bodies of the parenchymal cells and Kupffer cells. The lysosomes of the endothelial cells and fat-storing cells were weakly labeled. Quantitative analysis of the labeling density in the lysosomes of these three types of cells demonstrated that the lysosomes of parenchymal cells and Kupffer cells are main containers of cathepsin D in rat liver. The results suggest that cathepsin D functions in the intracellular digestive system of parenchymal cells and Kupffer cells but not so much in that of the endothelial cells.

Reinvestigation of the pathogenesis of familial xanthomatosis through conjoint cytochemical, ultrastructural, and biochemical studies

Autopsy tissues of a patient with Wolman's disease were examined biochemically, cytochemically, and with an electron microscope. In all tissues except brain, lysosomes of the cells of the reticuloendothelial system were filled with droplets of triglycerides and with cholesterol ester crystals. The parenchymal cells of adrenals and liver contained these compounds within large vacuoles which did not appear to be lysosomal in origin but which derived from, or were part of, the smooth and the rough endoplasmic reticulum cisternae. Most lysosomes of parenchymal cells were morphologically normal. Their acid β-glycerophosphatase activity was normal in liver hepatocytes and enhanced in parenchymal cells of the adrenals. These data suggest that an excessive synthesis of lipids rather than a deficiency of lysosomal “acid lipase” is responsible for the disease. However, a partial deficiency in acid lipase was found biochemically in the tissues examined. The apparent contradiction between biochemical and morphological data is discussed by the authors.

The demonstration of acid hydrolase, thermostable reduced diphosphopyridine nucleotide tetrazolium reductase and peroxidase activities in human lipofuscin pigment granules.

The characterization of human lipofuscin pigment granules as lysosomes is strengthened by the cytochemical demonstration of β-glucuronidase and glucosaminidase activities in hepatocyte pigment granules which also have acid phosphatase activity. Lysosomes of parenchymal cells and macrophages are seen to differ in their content of cytochemically demonstrable hydrolase activities. Reduced diphosphopyridine nucleotide tetrazolium reductase and peroxidase activities that are remarkably resistant to heat (90°C for 15 min) and prolonged fixation are also visualized in lipofuscin granules. It is suggested that these oxidative activities reflect the presence of heme compounds that accumulate during the degradation of cytoplasmic constituents in autophagic vacuoles or dense bodies. The presence of metabolites with peroxidase activity within lysosomes may be responsible for the oxidation of melanin precursors to melanin and unsaturated fat to the alcohol-insoluble lipid of lipofuscin pigment. Cytoplasmic iron (hemosiderin) that is stained by Perls' ferrocyanide or Quinke's sulfide procedures is also visualized by incubating sections for peroxidase activity in Karnovsky's 3,3'-diaminobenzidine medium. This activity disappears following the extraction of stainable iron in Lillie's dithionite medium. However, the heme-associated peroxidase activity is unaffected.