Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.9 (glucose-6-phosphatase)
3,081 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The theoretical advantages of electron microscopic cytochemistry were utilized to look for evidence of possible connections between peroxisomes and the endoplasmic reticulum in rat liver. Established cytochemical procedures for catalase (peroxisomes) and glucose-6-phosphatase (endoplasmic reticulum) were carried out, and evidence was sought of diffusion of reaction products between the organelles. No such diffusion was observed: lead phosphate was found in the endoplasmic reticulum and in the nuclear envelope but not in peroxisomes; oxidized diaminobenzidine (DAB) was seen only in peroxisomes. In addition, both types of cytochemistry were carried out on the same tissue. The two kinds of reaction product could be distinguished by virtue of their different electron opacities. No mixing of the two reaction products was observed. These results do not support the hypothesis that peroxisomes and endoplasmic reticulum may be connected; rather, they support the idea that the two organelles exist as separate cellular compartments.
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PMID:Relationship between peroxisomes and endoplasmic reticulum investigated by combined catalase and glucose-6-phosphatase cytochemistry. 627 50

The correlation between the cytochemistry (glycoprotein, glycogen, glucose-6-phosphatase, catalase, alkaline phosphatase) and the growth rate of the fast-growing Morris hepatoma 3924A and the slow-growing Morris hepatoma 9618A was studied by utracytochemical techniques. By the chromic acid-phosphotungstic acid technique, acid glycoprotein is stained in glycocalyx, Golgi saccules and vesicles, and secretory granules of the tumor cells of both hepatomas. However, the hepatoma 3924A cells contain thicker glycocalyx and more numerous glycoprotein-rich granules than hepatoma 9618A cells. Abundant alpha and beta glycogen particles are found in hepatoma 3924A. Moderate glucose-6-phosphatase activity is observed in the cisternae of endoplasmic reticulum and nuclear envelope of hepatoma 9618A, but it is totally absent in hepatoma 3924A. High catalase activity is present in numerous peroxisomes of hepatoma 9618A. Hepatoma 3924A contains only a few catalase-positive microperoxisomes. Weak to moderate alkaline phosphatase is present in the plasma membrane and nuclear envelope of hepatoma 9618A cells, while hepatoma 3924A shows no activity of the enzyme. All the cytochemical parameters except glycoprotein show an inverse relationship with the growth rate of the hepatomas. The higher intracellular glycoprotein content of hepatoma 3924A may be related to differences in cell coat secretion (composition and activity) from the slower-growing hepatoma 9618A
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PMID:Correlation between growth rate and cytochemistry in Morris hepatomas. 627 86

Histochemical and cytochemical studies were done to further characterize the preneoplastic hepatocytes with extraperoxisomal catalase (EPC-cells) that were found in the livers of rats fed 3'-methyl-4-dimethylaminoazobenzene. Catalase activity was demonstrated cytochemically to be localized in nuclear matrices, hyaloplasm, and peroxisomal matrices of EPC-cells. It is suggested that an impairment of peroxisome formation is involved in the altered intracellular distribution of catalase. Administration of clofibrate increased the catalase activity in EPC-cells. To examine the preneoplastic nature of EPC-cells, activities of glucose-6-phosphatase (G6Pase) and gamma-glutamyl transpeptidase (GGT) were examined, since changes in the activities of these enzymes have been used as markers of putative preneoplastic cells. In the present study, neither weak G6Pase activity nor positive GGT activity was considered to be a consistent feature of EPC-cells. However, available evidence suggests that EPC-cells are one of the carcinogen-induced cell populations with altered phenotypes.
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PMID:Hepatocytes with extraperoxisomal catalase in rats fed 3'-methyl-4-dimethylaminoazobenzene. 711 45

1. Analytical differential centrifugation of rat heart homogenates revealed a single population of mitochondria and microperoxisomes. Using cytochrome c oxidase, malate dehydrogenase and amine oxidase as mitochondrial marker enzymes, the s-value of mitochondria was estimated to s = 10326 +/- 406 S (average for the three marker enzymes). The s-value of microperoxisomes was found to be s = 1381 +/- 40 S using catalase as the marker enzyme. The s-value for the two organelles did not change significantly when the isoosmotic sucrose medium was substituted by an isoosmotic mannitol medium. 2. Analytical differential centrifugation revealed a polydispercity of the microsomal fraction using glucose-6-phosphatase and NADPH-cytochrome c reductase as the marker enzymes. The s-values were found to be sH1 = 1569 +/- 412 S (NADPH-cytochrome c reductase), sH2 = 1195 +/- 400 S (glucose-6-phosphatase) and sL = 153 +/- 28 S (NADPH-cytochrome c reductase and glucose-6-phosphatase). The recovery of marker enzymes in the isolated subcellular fractions was in the range of 84-94%. 3. When the mitochondrial and microperoxisomal fractions were subjected to isopycnic gradient centrifugation, using a self-generating gradient of polyvinylpyrrolidone-coated colloidal silica particles (Percoll) in 0.25 M sucrose medium, buoyant densities of 1.10 g/cm3 (main fraction of mitochondria) and 1.06 g/cm3 (main fraction of microperoxisomes) were obtained. The density gradient centrifugation separated microperoxisomes from contaminating lysosomes of high specific activity in acid phosphatase. A value 1.04 g/cm3 was found for the density of the microsomal fraction. 4. Based on the estimated s-values, an optimal procedure is described for the isolation of mitochondrial and microperoxisomal fractions from rat heart muscle.
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PMID:Hydrodynamic parameters and isolation of mitochondria, microperoxisomes and microsomes of rat heart. 715 Jun 62

Proximal tubules were isolated in highly pure form from rabbit cortices by a mechanical procedure that is known to preserve the structural and metabolic aspects of the tubular cells. Postnuclear supernates prepared from the isolated tubules were subjects to isopycnic centrifugation in linear sucrose gradients. The enzyme activities associated with the plasma membrane (gamma-glutamyl transpeptidase, amino-peptidase M, alkaline phosphatase, Na-K-ATPase, and phosphodiesterase I) exhibited sharp unimodal frequency-density profiles with a median density near 1.16 g/ml, which shifted to a heavier density when treated with digitonin. The lysosomal enzymes, N-acetyl-beta-glucosaminidase, alpha-mannosidase, and cathepsin B, and the peroxisomal enzyme catalase exhibited particle-associated activity near a density of 1.22 g/ml. Disruption of these particles by freezing and thawing resulted in these activities appearing in the rho = 1.10 g/ml region of the gradient where the soluble cytosolic enzyme, phosphoglucomutase, exhibited activity. Cytochrome oxidase activity typical of mitochondria gave a sharp unimodal profile at rho = 1.18 g/ml. Microsomal glucose-6-phosphatase and NADPH: cytochrome c reductase activities gave median densities near 1.16 g/ml, which did not change after incubation with digitonin. Galactosyl transferase activity gave a skewed profile at rho = 1.16 g/ml and showed a slight shift to heavier density after digitonin. This study of the enzymatic activities and density gradient distribution of the components of the proximal tubule cells provides the methodology for the further study of the cellular processing of endogenous and exogenous substances by this vital cell type.
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PMID:Analytical cell fractionation of isolated rabbit renal proximal tubules. 730 Jan 16

An electron microscopic, immunocytochemical, and enzyme cytochemical analysis of the previously established oval cell lines OC/CDE 6 and OC/CDE 22 was performed to characterize the phenotype and differentiation patterns of long-term cultures of oval cells. It was found that alpha-fetoprotein, albumin, and cytokeratin 19 are present in all cultured cells. This indicates that oval cells constitute a population of immature cells expressing features of the antigenic phenotype of both the hepatocyte and bile ductular cell lineages. An electron microscopic examination revealed a gradual alteration in the ultrastructure of oval cells toward hepatocyte-like cells. The majority of the oval cells were positive for glucose-6-phosphatase activity. A particularly striking observation was that oval cells were heterogeneous in terms of peroxisome content. Only about 50% of the oval cells had peroxisomes in the cytoplasm, these cells probably being part of the hepatocyte lineage. The other cultured cells did not reveal catalase activity and probably represented cells committed to the bile ductular cell lineage. An addition of clofibrate to the culture medium resulted in a marked peroxisome proliferation in all oval cells, indicating that oval cells might be able to change their differentiation pathway depending on environmental influence toward the hepatocyte lineage. It is most intriguing that in oval cells with abundant cytoplasm peroxisome proliferation was accompanied by proliferation of the smooth endoplasmic reticulum (this is a morphological marker of mature hepatocytes). Taken together, our findings suggest that within the oval cell lines OC/CDE 6 and OC/CDE 22 cells undergoing a morphological and functional differentiation along the hepatocyte and bile ductular cell lineages are present.
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PMID:Phenotype and differentiation patterns of the oval cell lines OC/CDE 6 and OC/CDE 22 derived from the livers of carcinogen-treated rats. 753 42

The formation of autophagosomes in rat hepatocytes was investigated during degradation of excess peroxisomes. Rat liver peroxisomes were markedly proliferated by administration of dioctyl phthalate (DEHP) for 2 weeks. When the animals were fed on normal diet for a week further, the number and size of the peroxisomes recovered to normal. The recovery process was confirmed by the assay and immunoblot analysis of acyl-CoA oxidase and catalase. During the recovery process, only a few autophagosomes were noted. However, when leupeptin (2 mg/100 g body weight) was injected into these animals, there was a marked accumulation of autophagosomes in the hepatocytes. Using this as an experimental model, the early stage of the autophagosome formation was analyzed by electron microscopy. Twenty minutes after the injection, isolation membranes surrounding the target organelles appeared. They were characterized by double layers with a narrow cisternal space and were sometimes continuous with the rough endoplasmic reticulum. Between the inner membrane of the isolation membranes and the enclosed organelles, electron-dense bridges were noted. Forty minutes after leupeptin injection, the lumen of the isolation membranes were enlarged and the inner membrane attached to the entrapped material. Enzyme cytochemical staining showed that the isolation membranes were negative for acid phosphatase and thiamine pyrophosphatase, but were strongly positive for glucose-6-phosphatase (G6Pase). The enlarged cisternae of the isolation membranes of the early autophagic vacuoles were in part positive for this enzyme, but gradually became negative with time. Similarly, the G6Pase activity was lost when the inner membrane was degraded. The results suggest 1) that the process of degradation of excess peroxisomes is rapid and carried out by the autophagic system in hepatocytes and 2) that the isolation membranes enclosing the target organelles are derived from the endoplasmic reticulum.
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PMID:Formation of autophagosomes during degradation of excess peroxisomes induced by administration of dioctyl phthalate. 822 9

Freeze-substituted rat liver embedded in glycol methacrylate (GMA) has been used to demonstrate the activities of several enzymes. The following enzymes could be detected in GMA-sections by the indicated histochemical procedure(s): 5'-nucleotidase (lead salt, cerium-diaminobenzidine), alkaline phosphatase (indoxyl-tetrazolium salt), catalase (diaminobenzidine), acid phosphatase (diazonium salt), lactate dehydrogenase (tetrazolium salt) and glutamate dehydrogenase (tetrazolium salt). The activities of all these enzymes were dramatically decreased compared with the activities demonstrated in unfixed cryostat sections, with the exception of catalase. The activities of the following enzymes could not be detected in GMA-sections: glucose-6-phosphate dehydrogenase (tetrazolium salt), xanthine oxidoreductase (tetrazolium salt), D-amino acid oxidase (cerium-diaminobenzidine-cobalt-hydrogen peroxide) and glucose-6-phosphatase (cerium-diaminobenzidine). The possible role of restricted penetration of reagents into the resin was studied by measuring cytophotometrically the enzyme activities in GMA-sections of 3 and 6 microns in thickness. For all the enzymes that could be detected, the 6 microns:3 microns ratio varied from 1.4 to 2.7. An eventual retarded penetration of reagents into the resin was investigated by measuring cytophotometrically the amount of final reaction product during incubation for acid phosphatase and glutamate dehydrogenase activities. In both cases linear relationships without a lag phase were found for the specific enzyme activities with incubation time. Chemical denaturation of proteins or masking of active sites in proteins due to embedding in the resin monomer may be considered to be the main cause of decreased enzyme activities.
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PMID:Quantitative aspects of enzyme histochemistry on sections of freeze-substituted glycol methacrylate-embedded rat liver. 827 44

The effect of storage of unfixed cryostat sections from rat liver for 4 h, 24 h, 3 days and 7 days at -25 degrees C was studied on the activities of lactate dehydrogenase, glucose-6-phosphate dehydrogenase, xanthine oxidoreductase, glutamate dehydrogenase, succinate dehydrogenase (all demonstrated with tetrazolium salt procedures), glucose-6-phosphatase (cerium-diaminobenzidine method), 5'-nucleotidase (lead salt method), dipeptidyl peptidase II, acid phosphatase (both simultaneous azo coupling methods), D-amino acid oxidase (cerium-diaminobenzidine-cobalt-hydrogen peroxide procedure) and catalase (diaminobenzidine method). The effect of drying of the cryostat sections at room temperature for 5 and 60 min was investigated as well. The enzyme activities were quantified by cytophotometric measurements of test and control reactions. The test minus control reaction was taken as a measure for specific enzyme activity. It was found that the activities of all the enzymes investigated, with one exception, were affected neither by storage of the cryostat sections at -25 degrees C for up to 7 days, nor by drying of the sections at room temperature for up to 60 min. The exception was xanthine oxidoreductase, whose activity was reduced by 20% after 5 min drying of sections or after 4 h storage. Therefore, only incubations for xanthine oxidoreductase activity have to be performed immediately after cutting cryostat sections, whereas for the other enzymes a considerable margin appears to exist.
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PMID:The effects of storage on the retention of enzyme activity in cryostat sections. A quantitative histochemical study on rat liver. 846 85

The anti-cancer efficacy of dietary beta-carotene (BC, 120 mg/kg diet, daily) was evaluated during diethylnitrosamine (DEN, 200 mg/kg body weight)-induced hepatocarcinogenesis in male Sprague-Dawley rats. BC treatment was carried out throughout the study, before initiation or selection/promotion phase of hepatocarcinogenesis in a defined experimental protocol. In red blood cells (RBC) and microsomal fractions from hepatic nodular and non-nodular surrounding parenchyma, the enzymatic lipid peroxidation increased significantly by more than 3-fold, 9- to 10-fold and 4- to 7-fold respectively 18 weeks following initiation by DEN as compared to normal control animals. RBC membrane protein damage was estimated by alanine release and was found to increase more than 5-fold in the same time period in DEN control rats. A decrease in hepatic cytosolic and microsomal glucose-6-phosphatase activities was observed, whereas the activities of the oxygen-derived free-radical scavenger enzymes, like cytosolic catalase and superoxide dismutase, were shown to increase significantly at the same time point. However, BC exposure in the different phases to hepatocarcinogenesis substantially changed all the above parameters in limiting the action of DEN. Results showed that the most significant beneficial effect of BC during hepatocarcinogenesis was exerted mainly in long term continuous and/or the initiation phase of carcinogenicity, rather than in the selection/promotion phase. Moreover, the volumetric and numerical densities of the preneoplastic lesions were all appreciably reduced by exposure to BC. We conclude that long term intake of BC could reduce cancer risk by preventing hepatic lipid peroxidation and RBC membrane protein damage due to its antioxidant actions.
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PMID:Beta-carotene prevents lipid peroxidation and red blood cell membrane protein damage in experimental hepatocarcinogenesis. 859 Apr 36


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