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 synaptic complexes of the rat pinealocytes are neither cholinergic nor adrenergic. In the synaptic vesicles, a neurotransmitter carrier substance of lipid nature reacting with OsO4-Zn I2 mixture (similar to that present in both cholinergic and adrenergic vesicles) was not found. In addition, there were no indications of glucose-6-phosphatase or thiamine-pyrophosphatase activity in the synaptic vesicles. Thus, it appears that the synaptic vesicles do not originate from the rough or smooth endoplasmic reticulum. The synaptic ribbons do not contain carbohydrates, are of protein nature and possess some chemical resemblance to microtubules and microtubular bouquets. Appropriate ultracytochemical reactions have not shown detectable quantities of sodium and calcium ions in pinealocyte synaptic complexes.
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PMID:Ultracytochemistry of the synaptic ribbons in the rat pineal organ. 0 83

alpha-glucosidases are cellular enzymes, able to split the polysaccharides into glucose. In subcellular fractions from rat and trout hepatocytes, the distribution patterns of neutral alpha-glucosidase and of glucose-6-phosphatase appear to be very similar, i.e., closely linked to the endoplasmic reticulum, and are somewhat related to the particular glycogen. The data suggest a probable role of neutral alpha-glucosidase in cell physiology and in carbohydrates metabolism.
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PMID:[Similar distribution of the activities of neutral alpha-glucosidase (gamma-amylase) and glucose-6-phosphatase in subcellular fractions from rat and trout livers]. 3 99

2-Deoxy-D-galactose, in a dose of 3 mmol/kg, was administered intraperitoneally twice daily to young rats for periods up to 12 weeks. This dosage schedule resulted in recurrent phosphate trapping predominantly in liver. UTP deficiency was excluded by simultaneous uridine injections. Phosphate trapping was caused by the rapid accumulation of 2-deoxy-D-galactose 1-phosphate and was most pronounced in liver but also demonstrated in small intestine, brain, spleen, and thymus. The marked, although transient, drop in the hepatic content of inorganic phosphate triggered the catabolism of adenine nucleotides and a loss of ATP. Other metabolic pathways affected by phosphate deficiency include glycogenolysis and glycolysis. Increasing with time, repeated doses of the galactose analog led to retardation and arrest of growth, hepatomegaly, and splenomegaly. The average relative liver and spleen weights were elevated 2.5- and 4.5-fold, respectively, after 12 weeks of treatment. Liver damage was indicated by hyperbilirubinaemia and a progressive rise in the activity in plasma of sorbitol dehydrogenase, alkaline phosphatase, and gamma-glutamyltransferase. Examination by light and electron microscopy showed increasing numbers of vacuoles, surrounded by a single membrane, in hepatocytes, sinusoidal endothelial cells, and Kupffer cells. Focal cytoplasmic degeneration in hepatocytes was occasionally indicated by formation of autophagic vacuoles and finger print lysosomes. Hepatocytes of 2-deoxy-D-galactose-treated rats showed a dissociation and fragmentation of the rough endoplasmic reticulum. Sinusoidal endothelial cells and Kupffer cells were markedly enlarged, the latter contained a PAS-positive but amylase resistant substance. Extrahepatic changes included an increased occurrence of vacuolated cells in thymus. Phosphate trapping and its metabolic consequences are common phenomena in the experimental injury induced b 2-deoxy-D-galactose and in some hereditary diseases such as uridylyltransferase deficiency galactosaemia, fructose intolerance and glucose-6-phosphatase deficiency.
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PMID:Consequences of recurrent phosphate trapping induced by repeated injections of 2-deoxy-D-galactose. Biochemical and morphological studies in rats. 4 10

The acute effects of the PCB (polychlorinated biphenyls) mixture (Aroclor 1254) on microsomal enzymes and on synthesis and turnover of microsomal and cytoplasmic lipids of rat liver were investigated. Six daily i.p. injections of 25 and 50 mg PCB/kg body weight resulted in increased liver weight and liver to body weight ratios. When compared to controls PCB treatment resulted in a six-fold increase in amount of cytochrome P-450. Activities of NADPH-cytochrome c reductase, ethylmorphine demethylase and inosine diphosphatase were increased whereas glucose-6-phosphatase values were decreased by PCB exposure. Analysis of liver homogenate and microsomal fraction revealed an increase in lipid in PCB-exposed animals. Phospholipids, cholesterol and triglyceride were significantly increased after PCB exposure; however, the greatest percentage increase was seen in the triglyceride pool. The finding of an increase in microsomal triglyceride to phospholipid ratios with exposure to PCB is suggestive of an increase in membrane-enclosed lipid (liposomes). Studies with labelled glycerol indicated that the PCB-induced fatty liver resulted from increased half life but not increased synthesis of liver lipid moieties. The rate of incorporation of leucine into microsomal membrane and albumin was somewhat enhanced in rats exposed to PCB indicative of increased protein synthesis. Morphological studies showed increased occurrence of lipid material, both in cytoplasmic droplets and within rough and smooth-surfaced endoplasmic reticulum. Proliferation of smooth endoplasmic reticulum and flattened Golgi cisternae with no secretion granules containing lipoprotein particles characterized the liver from animals exposed for 6 days. The increase in lipid within membranes of the endoplasmic reticulum together with the flattened Golgi lacking typical secretory vesicles indicates a defect in transport of lipoproteins from the endoplasmic reticulum to the Golgi apparatus and may be the cause of the PCB-induced fatty liver.
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PMID:Studies on the cellular toxicity of polychlorinated biphenyls (PCBs). I. Effect of PCBs on microsomal enzymes and on synthesis and turnover of microsomal and cytoplasmic lipids of rat liver- a morphological and biochemical study. 9 1

Differential centrifugation was applied to adult and foetal liver of monkey. Obtained fractions were: F1 (800 X g); F2 (12 500 X g); F3 (200 000 X g); and cell sap. Analysis of chemical compounds of these fractions shows that: (1) adult and foetal nucleic acids levels are similar; (2) there are more proteins in adult than in foetal hepatocytes; (3) most of the glycogen is located in F3; the foetal level is twenty times higher than the adult level. Plasma membrane enzymes (5'-nucleotidase, adenylate cyclase) show a nucleomicrosomic distribution. The distribution of alkaline phosphatase is not significant. Mitochondrial enzymes (monoamine oxydase, succinate cytochrome c reductase, cytochrome oxydase) are enriched in F2 without any sedimentation in F3. There is more malate dehydrogenase liberated in cell sap during foetal liver fractionation. This indicates the foetal mitochondria are more sensitive to the homogenisation method. Lysosomal enzymes (acid phosphatase, N-acetylglucosaminidase) are enriched in F2. The same observation for N-acetylglucosaminidase as for malate dehydrogenase leads to the same conclusion for foetal lysosomes. Endoplasmic reticulum and Golgi enzymes (glucose-6-phosphatase and related phosphotransferase activity, NADPH-cytochrome c reductase and sialytransferase) are much enriched in F3. Thus this fraction F3 is pure enough to allow the observation of the modification produced on endoplasmic reticulum and Golgi apparatus during foetal and neonatal development.
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PMID:[Comparative study of microsomal enzymic activities in adult and foetal monkey hepatocytes (author's transl)]. 11 30

An alternative to previous methods (tissue chopper, frozen sections) for the ultrastructural demonstration of phosphatases is described. The present approach is based on a short vascular perfusion of rat liver with glutaraldehyde through the inferior caval vein, followed by vascular perfusion incubation with a medium containing the enzyme substrates. The effect of glutaraldehyde on three different types of phosphatases was investigated, namely a lysosomal enzyme (acid phosphatase) a tightly bound microsomal enzyme (G6Pase) and a loosely bound microsomal enzyme (IDPase). It is demonstrated that by perfusion with glutaraldehyde for three minutes good cellular morphology is obtained and that 50-60% of the initial activity of glucose-6-phosphatase, inosine-diphosphatase and acid phosphatase remains. The localization and deposition of G6Pase activity were distinct and observed throughout the endoplasmic reticulum and the nuclear envelope. For acid phosphatase, the reaction product was confined to various types of lysosomes including presumed autophagic vacuoles. No signs of enzyme diffusion were noted. The present approach seems to offer some advantages: it is simple and requires no extra equipment, penetration of the fixative and incubation enzyme medium is good, and finally freeze artifacts are avoided.
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PMID:Ultrastructural demonstration of phosphatases by perfusion fixation followed by perfusion incubation of rat liver. 16 67

The recirculating perfusion of adult rat liver with a Ca-++-free Hanks' solution produces a release of the adhesiveness of cells and a cleaving of the desmosomes. The addition of collagenase and hyaluronidase to the perfusion medium leads to complete dissociation of the liver tissue into a mixture of isolated cells and cell cords in which the hepatocytes remain connected with specific junctional differentiations, namely the gap and tight junctions. Individual cells are released by submitting the suspension of cell trabeculae to a gentle rolling. The gap junctions are ruptured at least in one of the two adjacent cells and remain generally attached to the other cell taking with them a small portion of cytoplasm. This technique of isolation of hepatocytes yields about 60-65% of the parenchymal cells contained in a liver; endothelial cells and other cells of the connective tissue are not recovered. The ultrastructural preservation of the isolated hepatocytes is excellent and the glucose-6-phosphatase activity, confined to the endoplasmic reticulum, appears unaltered in most cells. Protein, DNA and RNA recovery in the preparations of isolated hepatocytes is satisfactory, amounting to 70% of that found in liver homogenate; glycogen, the most labile component examined, is partly lost or degraded during the manipulations. Cell diameters measured by different methods confirm the preservation of the original volume of the in situ hepatocytes and the presence of more than one type of parenchymal cell. By submitting this heterogeneous cell population to an isopycnic density gradient centrifugation, two types of hepatocytes can be distinguished: the light hepatocytes, with a mean diameter of 20.5 mum and a mean density of 1.10, are characterized by an extended smooth-walled endoplasmic reticulum entrapping dispersed alpha-glycogen particles; the heavy hepatocytes, with a mean diameter of 19.0 mum and a mean density of 1.14, present a relatively reduced compartment of smooth endoplasmic reticulum, but large accumulations of glycogen. It is suggested that the cell fraction of low density is enriched in centrolobular cells and the high density fraction in perilobular hepatocytes.
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PMID:Isolation and subfractionation on ficoll gradients of adult rat hepatocytes. Size, morphology, and biochemical characteristics of cell fractions. 16 28

Daily phenobarbital (PB) injections, on 3-7 consecutive days, induce an intense proliferation of smooth endoplasmic reticulum (ER) associated with a decrease of the glucose-6-phosphatase activity. This situation first affects the centrolobular hepatocytes, enhancing the degree of liver lobule heterogeneity. This experimental model was used for isolation and further subfractionation of hepatocytes on Ficoll density gradients, as described in the preceding paper. Profiles of protein, DNA, RNA, glycogen, phosphorylase, and glucose-6-phosphatase were determined all along the gradient. Two liver cell populations were distinguished: (a) light hepatocytes (mean density 1.10) present the same morphological characteristics as centrolobular cells, i.e., an abundant smooth ER composed of tubular elements, numerous small mitochondria, and few glycogen particles; (b) heavy hepatocytes (mean density 1.14) are characterized by large and compact glycogen areas and prominent rough endoplasmic cisternae, as are the perilobular cells. After incubation in the Wachstein-Meisel medium, Centrolobular hepatocytes exhibit dispersed reaction sites of glucose-6-phosphatase activity, whereas perilobular cells present a continuous and intense reaction. Morphometric determinations were carried out for both cell populations. Centrolobular PB hepatocytes are considerably enlarged (mean diameter: 23.7 mum); perilobular hepatocytes have a significantly smaller mean diameter of 19.2 mum, which is close to the values of control liver cells.
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PMID:Isolation of centrolobular and perilobular hepatocytes after phenobarbital treatment. 16 29

The activities of liver microsomal enzymes were studied in preparations from unanesthetized rats and rats anesthetized for one hour with nitrous oxide, diethyl ether, halothane or chloroform. Most of the enzymes studied were cytochrome P-450-dependent oxygenases that hydroxylate endogenous substrates. The other microsomal enzymes, assayed for comparison, included the cytochrome P-450-dependent aminopyrine demethylase, glucose-6-phosphatase, a dehydrogenase, and NADPH-cytochrome P-450 reductase. No anesthetic was associated with a significant change in activity of any enzyme studied. In rats pretreated with phenobarbital no anesthetic except chloroform changed enzymic activity. All hydroxylations were inhibited markedly by chloroform, as were a microsomal dehydrogenation, hydrolysis of glucose-6-phosphate, and NADPH-cytochrome P-450 reductase activity. Administration of alpha-tocopherol did not prevent the inhibition associated with chloroform in phenobarbital-induced animals. It is concluded that cytochrome P-450-dependent hydroxylations involved in metabolic processes normally proceeding in the endoplasmic reticulum of the liver are not permanently affected by the anesthetics used in this study. The inhibitory effect of chloroform after pretreatment with phenobarbital is unspecific and affects a large number of different microsomal enzymes. Evidence that mechanisms other than lipid peroxidation may be responsible for the toxic effects of chloroform in the liver is presented.
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PMID:Inhalation anesthetics and cytochrome P-450-dependent reactions in rat liver microsomes. 16 17

The present investigation was undertaken to discover whether repeated doses of dimethylnitrosamine (DMNA) could produce a cumulative toxic effect on the rat liver. For this purpose doses were selected at a level just too low to produce cytopathological changes, as indicated by depression of glucose-6-phosphatase and induction of autophagic vacuoles (AV) in hepatocytes, when given once only. Single subcutaneous injections of 10 or 3 mg/kg induced these cytopathological changes in the centrilobular (CLB) hepatic cells but when the dose was reduced to 1 mg/kg no such changes were seen. After daily administration of 1 mg/kg for 4 or 8 weeks we observed both glucose-6-phosphatase depression and autophagy, and in addition there was marked hypertrophy of the rough endoplasmic reticulum, nucleolar microsegregation and the appearance of distorted, often ring-shaped mitochondria with shortened cristae. Kupffer cells exhibited a marked increase in lysosomal activity. With the exception of mitochondrial changes and Kupffer cell activity this same picture was observed, although in milder form, when the dose administered was 0.3 or 0.1 mg/kg daily for the same period. When treatment was continued for 12 weeks, however, the only differences from control rats were the presence of hypertrophied rough endoplasmic reticulum (RER) at all three dose levels, nucleolar microsegregation at the upper two dose levels, and pronounced Kupffer cell activity at the top dose. These findings indicate that cumulative cytopathologic effects occur only up to 8 weeks at the dose levels studied but hypertrophy of RER and increased Kupffer cell activity persist up to 12 weeks.
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PMID:Reversibility of lysosomal and glucose 6-phosphatase changes produced in the rat liver by dimethylnitrosamine. 16 89


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