Cytoplasm Of Liver Parenchymal Cells Research Articles

NADPH-dependent lipid peroxidation capacity in unfixed tissue sections: characterization of the pro-oxidizing conditions and optimization of the histochemical detection

Factors which influence the iron-stimulated lipid peroxidation in rat liver have been studied by incubating unfixed cryostat sections with a pro-oxidant system and using an optimized histochemical detection method for lipid peroxidation products with 3-hydroxy-2-naphthoic acid hydrazide and Fast Blue B. We used a method that was slightly different from the one described previously. The final reaction product was exclusively localized in the cytoplasm of liver parenchymal cells with a homogeneous distribution within the liver lobule. The absorbance maximum, as measured cytophotometrically, was found to be 550 nm. Maximum lipid peroxidation was observed when the pro-oxidant system contained 0.2 mM NADPH, 1 mM ADP and 15 microM FeCl2. Some reaction product was found when NADPH was omitted. Iron concentrations higher than 180 microM prevented the formation of lipid peroxidation products in certain areas of the sections, whereas ADP concentrations higher than 1 mM inhibited the reaction in the whole section. A pH dependency was also observed, with the highest lipid peroxidation at pH 7.2. Optimum lipid peroxidation was induced by incubating for 30 min at 37 degrees C with the pro-oxidant system. A linear relationship was found between the thickness of the sections (up to 20 microns) and the amount of lipid peroxidation products. The addition of scavengers of O2-. (superoxide dismutase), hydrogen peroxide (catalase) and OH. (mannitol) to the first step medium did not affect the amount of final reaction product. These findings appear to confirm the hypothesis proposed for events occurring in isolated microsomes, leading to the formation of hydroperoxides and ultimately lipid peroxidation-derived carbonyls.(ABSTRACT TRUNCATED AT 250 WORDS)

Peroxisomes in guinea pig liver: their peculiar morphological features may reflect certain aspects of lipoprotein metabolism in this species

We have studied the ultrastructural characteristics and the distribution of peroxisomes in guinea pig liver using electron-microscopic cytochemistry for catalase and morphometry. By light microscopy, peroxisomes appear as dark 0.2-0.5 microns granules in the cytoplasm of liver parenchymal cells, often forming large clusters that measure up to 5 microns across. Rows of single peroxisomes or their aggregates line the sinusoidal surface of hepatocytes. Electron microscopy reveals that clusters of up to 25 individual peroxisomes are usually located in the subsinusoidal region of parenchymal cells. The mean diameter and the volume density of peroxisomes are larger in pericentral than in periportal regions of the liver lobule. Whereas large amounts of lipoprotein particles with a mean diameter of 160 nm (chylomicrons) are present in the Disse space, the cytoplasm of parenchymal cells contains multivesicular bodies and abundant lipid droplets. In addition, the Golgi complexes show distended lipoprotein-filled vesicles suggesting active biosynthesis of lipoproteins. We propose that the unique features of peroxisomes in guinea pig liver, such as cluster formation and alignment along the sinusoidal surface, may be related to the high levels of lipoproteins in the portal circulation and their hepatic catabolism in this species.

Changes in acid phosphatase activity in rat liver after ischemia.

The effect of ischemia on the stability, i.e. the permeability of the lysosomal membrane of rat liver has been studied using quantitative histochemical analysis of acid phosphatase activity. Ischemia in vitro was performed for 0-240 min at 37 degrees C and ischemia in vivo for 60 min was followed by 1, 5, 24 and 48 h of reperfusion. Acid phosphatase activity was demonstrated in cryostat sections using naphthol AS-BI phosphoric acid as substrate and polyvinyl alcohol was added to the incubation medium to counteract diffusion phenomena. Ischemia in vitro up to 240 min did not affect the localization nor the total activity of acid phosphatase activity. After 60-min ischemia in vivo followed by 1-h reperfusion distinct areas showed decreased acid phosphatase activity. A further decrease in activity was observed after 5 h reperfusion. Final reaction product generated by acid phosphatase activity was rather diffusely distributed in border zones between normal and damaged tissue after 24 and 48 h of reperfusion following 60 min ischemia in vivo. It is concluded that not ischemia itself but rather reperfusion affects the stability of the lysosomal membrane due to the occurrence of oxygen-derived free radicals and/or imbalanced Ca2+ concentration. Restoration of the blood flow causes leakage of acid phosphatase from the lysosomes into the cytoplasm of liver parenchymal cells and from there to the blood.

Analysis of the antigenic composition of liver specific lipoprotein using murine monoclonal antibodies.

Eight monoclonal antibodies have been raised to antigenic determinants within the liver specific lipoprotein complex. Five of these determinants were species and the others non-species specific. No liver specific determinants were identified. Liver specific lipoprotein antigens recognised by the eight monoclonal antibodies were located either on the hepatocyte membrane and/or along the sinusoidal lining wall or in the cytoplasm of liver parenchymal cells. All antibodies but one reacted with the cell membrane of viable human hepatocytes. The molecular weights of four liver specific lipoprotein-determinants were determined by immunoprecipitation. These ranged from 22 000 to 164 000 daltons.

Hepatic ultrastructure in fucosidosis.

The hepatic wedge biopsy of a 3 1/2-year-old boy with fucosidosis was studied by electron microscopy. The cytoplasm of liver parenchymal cells is filled with various forms of membrane-invested storage elements measuring up to 3 μm in diameter. In these storage elements large central deposits of reticulogranular material are surrounded by a narrow peripheral ring of electron-dense material. Others contain numerous lamellar structures with parallel and/or concentric orientation, opaque globules and vesicular structures. Typical peribiliary dense bodies (lysosomes) are generally absent. The storage elements appear to be produced by deposition of storage material in lysosomes. The absence of the lysosomal enzyme α-L-fucosidase is in favor of this concept. Kupffer cells, epithelial cells of the bile canalicular system, vascular endothelial cells of portal tracts and histiocytes are rich in storage elements which are also found in the majority of fibrocytes and fibroblasts. They are uncommon in pericytes and cannot be demonstrated in smooth muscle and fat-storing cells. Ultrastructural features and cellular distribution of storage elements are compared with previous descriptions of related storage disorders.

The effect of monocrotaline, a pyrrolizidine alkaloid, on HeLa cells and primary cultured cells from rat liver and lung.

Monocrotaline, a pyrrolizidine alkaloid, produced marked cytoplasmic vacuolization, cellular and nuclear enlargement, and mitotic abnormalities on HeLa cells and primary cultured cells from rat liver and lung. Fat droplets were specifically found in the cytoplasm of liver parenchymal cells. Chromosome preparation of the treated cultures from rat lung revealed marked breaks and fusions. The mechanism of vacuole formation could be ascribed to the basicity of the alkaloid. Severe disorders of chromosomes might correlate to the carcinogenic activity of the compound.

The use of sodium chloride-containing fixatives in minimizing cellular distortion in histological and cytochemical preparations.

The principal objective of this study was to determine the relative effect of the concentration of small, mobile ions in fixing solutions on cellular shrinkage and distortion occurring during fixation or in the subsequent processing of tissues by the paraffin method. Samples of rat liver tissue were fixed in neutral 20% formalin, neutral 20% formalin/0.7% sodium chloride, Bouin's fluid, and Bouin's fluid/0.7% sodium chloride. By a comparison of nuclear and cytoplasmic volumes, it was noted that in the case of formalin fixation, the addition of 0.7% sodium chloride reduced nuclear and cytoplasmic shrinkage by 18-26%. In Bouin fixation the addition of 0.7% sodium chloride reduced nuclear shrinkage by 7-10% and cytoplasmic shrinkage by approximately 21%. It was also shown that when the sodium chloride is omitted, neutral 20% formalin is significantly less effective than Boumin's fluid in stabilizing the cytoplasm of liver parenchymal cells against shrinkage. In those instances in which tissue shrinkage was minimized by the addition of sodium chloride to the fixing medium, the final preparations revealed less tissue distortion and a more adequate preservation of fine detail. Some mention is also made of differences incurred in staining reactions of liver tissue following the use of sodium chloride containing fixatives.