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)

Oval cells are liver epithelial cells that proliferate during hepatocarcinogenesis and chemically induced severe liver injury. It has been suggested that these cells represent hepatic stem cells which might play an important role in the histogenesis of cholangiocellular as well as hepatocellular carcinomas. In order to test this hypothesis highly purified oval cell preparations and propagable oval cell lines are needed. In the present study the isolation, biochemical characterization, and long-term culture of oval cells from rats fed a choline-deficient/DL-ethionine-supplemented diet for 6, 14, or 22 weeks are described. The freshly isolated oval cells were gamma-glutamyltranspeptidase-positive, cytokeratin 7-, 8-, 18-, and 19-positive, albumin-positive, peroxidase-negative, and alpha-fetoprotein-negative and expressed lactate dehydrogenase isoenzymes 1-5. In addition, low but clearly measurable glucose-6-phosphatase and high gamma-glutamyltranspeptidase and alkaline phosphatase activities (when compared to activities in untreated liver parenchymal cells) were measured in oval cells. Three oval cell lines, OC/CDE 6, OC/CDE 14, and OC/CDE 22, were established. They contained small and large epithelial cells replicating to form uniform monolayers with a cobblestone appearance; furthermore, a very low number of mononucleated giant cells were also present in the three cell lines. OC/CDE 6, OC/CDE 14, and OC/CDE 22 cells were gamma-glutamyltranspeptidase-negative, were transiently albumin-positive, maintained the glucose-6-phosphatase activity levels measured in freshly isolated oval cells, and expressed lactate dehydrogenase isoenzymes 2-5. After exposure of the cultured oval cells to dimethyl sulfoxide or sodium butyrate, 35-40% of the cells reexpressed albumin, and glucose-6-phosphatase activity was enhanced; in addition, sodium butyrate strongly increased gamma-glutamyltranspeptidase and alkaline phosphatase activities. In conclusion, oval cells express phenotypic markers of liver parenchymal as well as bile duct epithelial cells and possess a certain intrinsic plasticity. In order to test if the oval cells indeed represent an intermediate step in the differentiation of certain cells within the bile duct and ductular epithelial cell compartment to parenchymal cells, the three cell lines described herein will be transformed in vitro and their potential to give rise to cholangiocellular and/or hepatocellular carcinomas will be verified in vivo.
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PMID:Isolation, biochemical characterization, long-term culture, and phenotype modulation of oval cells from carcinogen-fed rats. 767 95

The localization of some membrane-associated enzymes such as alkaline phosphatase, 5'-nucleotidase, glucose-6-phosphatase, Na+,K(+)-adenosine triphosphatase, adenylate cyclase and guanylate cyclase in the Merkel cell-axon complexes, trigeminal ganglia and the principal trigeminal sensory nucleus of the cat was determined at light and electron microscopic level using cytochemical techniques. In the sinus hair follicles (vibrissae), the reaction end product marking alkaline phosphatase and adenosine triphosphatase activities was visualized on the axons running through external follicle epithelium and the 5'-nucleotidase, adenylate- and guanylate cyclase positive reaction was seen to stain the plasma membranes of Merkel cells. In the trigeminal ganglia, the strongest alkaline phosphatase and adenosine triphosphatase activities showed the corresponding areas between the ganglion and satellite cells. 5'-nucleotidase activity was more intense on the neurilemmas and the surrounding glial plasma membranes. In the principle sensory trigeminal nucleus, the central neurons exhibited an intense alkaline phosphatase, 5'-nucleotidase and adenosine triphosphatase activities and much smaller amount of reaction product for adenylate cyclase and guanylate cyclase was observed. In conclusion, membrane-bound enzymes could be histo- and cytochemically demonstrated in all components of primary trigeminal afferent units. Our results have confirmed that the receptor function and the nerve impulses conductance need an intensive molecular and cation exchange, and energy supply.
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PMID:Primary trigeminal afferent neuron of the cat: I. Studies on membrane-bound enzyme histochemistry. 798 69

Glycoprotein processing in Dictyostelium discoideum is characterized by enzyme catalyzed steps not reported in other organisms. One of these is the formation of a beta 1 --> 4 linkage between GlcNAc and the mannose linked to the core mannose in the alpha 1 --> 6 position of N-glycosides. A simple and sensitive assay for this GlcNAc transferase activity, using a tri-mannose acceptor and a low concentration of UDP-GlcNAc, was developed. Homogenates of the organism were subjected to sub-cellular fractionation by centrifugation in discontinuous sucrose gradients. The specific activity was enriched 4-5-fold in a crude membrane fraction. The transferase was purified 10-12-fold in a membrane fraction that bands on top of 1.1 M sucrose. This fraction was also enriched in nucleotidyldiphosphatase. The enriched fraction was deficient in glucose-6-phosphatase, an endoplasmic reticulum marker. Approx. 80% of the transferase activity was latent, and unavailable to protease. Purified membranes were either subjected to phase separation in Triton X-114, or sodium carbonate extraction or sonication. In each case, the transferase behaved as an intrinsic membrane protein. Several secreted and lysosomal proteins are modified by the enzyme. These data support the idea that the GlcNAc transferase is present as an integral Golgi membrane protein and that at least the catalytic center of the transferase is on the lumenal side of the vesicles.
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PMID:Subcellular distribution of "intersecting' beta-N-acetylglucosaminyltransferase in Dictyostelium discoideum. A likely marker for the Golgi apparatus. 865 99

A line of hepatic endoderm cells, hepatoblast cell line 3 (HBC-3), was derived from the liver diverticulum of the mouse on day 9.5 of gestation by culture on a mitomycin C treated STON+ feeder layer in a hepatoblast culture medium consisting of Dulbecco's modified Eagle's medium, nonessential amino acids, fetal calf serum, and beta-mercaptoethanol. This line, HBC-3, stains positively for alpha-fetoprotein, albumin, and cytokeratin 14 (CK-14), protein markers expressed by the embryonic liver diverticulum, indicating that HBC-3 cells retain an undifferentiated hepatoblast phenotype. HBC-3 cells acquire hepatocyte-like ultrastructural characteristics, including bile canaliculi, peroxisomes, and glycogen granules, when maintained in culture for 3 weeks without passage. Treatment with dimethylsulfoxide or sodium butyrate induces a rapid hepatocytic differentiation. The cells cease to express alpha-fetoprotein and CK-14, maintain albumin expression, and become positive for glucose-6-phosphatase activity (a profile consistent with differentiation along the hepatocyte lineage). On Matrigel, HBC-3 cells form elaborate ductular structures, which are positive for gamma-glutamyl transpeptidase and CK-14 and CK-19 and do not express detectable amounts of albumin, a phenotypic change consistent with differentiation along the bile ductular lineage. Thus, HBC-3 cells behave in culture as bipotential hepatoblasts and provide a model system to identify factors that regulate bipotential differentiation in the liver.
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PMID:Selective bipotential differentiation of mouse embryonic hepatoblasts in vitro. 903 73

The influence of amphotericin B on various cytochrome P450-dependent mixed-function oxidases, antipyrine clearance and glucose-6-phosphatase was investigated in rats treated daily with deoxycholate amphotericin B (3 mg/kg body weight, intravenously) either for 1 or 4 days. Enzyme activity was measured ex vivo in hepatic microsomes. Following amphotericin B plus deoxycholate application for day 1, ethoxycoumarin-O-deethylase activity decrease significantly whereas microsomal cytochrome P450 concentration, cytochrome c reductase activity, antipyrine clearance and glucose-6-phosphatase activity did not change significantly. In contrast, following application of amphotericin B plus deoxycholate for 4 days the cytochrome P450 concentration was reduced by 50% (p < 0.05) as well as ethoxycoumarin-O-deethylase activity, antipyrine clearance and glucose-6-phosphatase activity: ethoxycoumarin-O-deethylase 232 +/- 68 pmol/mg/min, control 442 +/- 99 pmol/mg/min (p < 0.01); antipyrine clearance 0.56 +/- 0.21 ml/min, control 0.96 +/- 0.18 ml/min (p < 0.01), and glucose-6-phosphatase 193 +/- 28 mU/mg, control 351 +/- 95 mU/mg (p < 0.05). Cytochrome c reductase activity did not decrease significantly. Besides an increase in cytochrome c reductase activity, sodium deoxycholate (a vehicle of amphotericin B) alone induced no significant changes. Microsomal protein related to liver wet weight was significantly reduced by 50% (p < 0.01) only in animals treated for 4 days with amphotericin B plus deoxycholate. The results show that a 1-day treatment of rats with amphotericin B decreases ethoxycoumarin-O-deethylase activity, whereas the hepatic microsomal cytochrome P450 content, cytochrome c reductase and glucose-6-phosphatase activity did not change. Amphotericin B given for 4 days significantly decreases hepatic microsomal enzyme function. The inhibitory effect of amphotericin B on hepatic cytochrome P450 may be due to inhibition of hepatic protein synthesis.
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PMID:Influence of amphotericin B treatment duration of hepatic microsomal enzyme function in rats. 932 8

Synaptic plasma membrane (SPM) vesicles represent a membrane fraction very useful in studying non-vesicular neurotransmitter release. The procedure described here to isolate SPM vesicles from a crude synaptosomal fraction of sheep brain cortex is quick, simple (ultracentrifugation in a discontinuous density gradient of dextran T110), and combines a high yield (130 micrograms/g brain) with a satisfactory grade of purification. The preparation of SPM vesicles consists of vesicles (approximately 0.54 +/- 0.8 micron diameter) delimited by a single membrane with the native orientation. We are able to ascertain these characteristics on the basis of morphology studies (electron microscopy observations), enzyme activities (Na+/K(+)-ATPase, Ca2+/Mg(2+)-ATPase, acetylcholinesterase and glucose-6-phosphatase), biochemical composition (lipid and protein analysis) and the tetrodotoxin sensitivity of the veratridine-induced gamma-aminobutyric acid (GABA) release. Isolating the SPM vesicles by the proposed procedure permits manipulating the ionic gradients across the membrane by changing the ion concentrations on either side or by utilizing specific ionophores. The vesicles retain their various activities, including their capacity for neurotransmitter uptake and release assays for at least 3 months, when preserved at -70 degrees C. Furthermore, the vesicles permit depicting the electrochemical gradients across the membranes into chemical and electrical components. We describe the use of the tetraphenylphosphonium cation (TPP+) to dissipate the membrane potential (delta psi) of the vesicles, while preserving ionic gradients. The characteristics of the lipid-soluble cation TPP+ allows a massive inflow of this cation into vesicular compartments and a consequent depolarization.
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PMID:Membrane potential manipulation in synaptic plasma membrane vesicles for studying neurotransmitter uptake and release. 938 41

Methods have been developed for producing functional, transporting monolayers of avian proximal tubule (PT) cells. A highly homogenous fraction of PT fragments was prepared by enzymatic digestion (collagenase + Dispase) of chick (3- to 5-day-old) kidneys, followed by Percoll gradient centrifugation. The PT fraction was enriched in glucose-6-phosphatase, a proximal enzyme marker, and reduced in specific activity of hexokinase, a distal marker. PT fragments were grown to confluence in serum-free media on collagen-coated permeable filter supports. Electron microscopy of confluent monolayers revealed numerous microvilli and mitochondria, central cilia, and tight junctions, all characteristic of PT cells. gamma-Glutamyltranspeptidase, a proximal brush-border enzyme, showed threefold higher activity on apical than on basolateral sides of the monolayer. The electrophysiological characteristics of monolayers were investigated by voltage-clamp techniques. Monolayers displayed low transepithelial resistances (40-60 Omega . cm2), lumen-negative potentials, and baseline currents of 6-12 microA/cm2 (with or without 5 mM glucose). Both alpha-methyl-D-glucose (2 mM), a nonmetabolizable hexose, and phenylalanine (2 mM) significantly stimulated short-circuit current when added to the mucosal side of glucose-free monolayers. Phloridzin, a specific inhibitor of Na+-coupled glucose transport, significantly inhibited short-circuit current, as did 10(-5) M amiloride. Monolayers also expressed net secretory transport of urate. This cell culture preparation may provide a useful working model for the study of avian PT transport.
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PMID:Characterization of a primary cell culture model of the avian renal proximal tubule. 968 82

Little is known about the development of the central nervous system (CNS) in humans. Ethical considerations preclude experimental studies in this field, and as a result most available data on human ontogenesis are descriptive. Comparative anatomic and embryologic studies have demonstrated that the main developmental milestones are conserved across species, and their results can be used to suggest a likely scenario for human development. The development of the ventricles, meninges, and choroid plexuses are discussed in this article. The central cavity of the neural tube is formed during neurulation, which occurs during the fourth gestational week. The first milestone is occlusion of the spinal neurocele (the central canal in the neural tube) shortly after neurulation. This prevents free communication between the ventricular system and the amniotic cavity. The second milestone is development of the meninges, which separate the central nervous system from the rest of the body. The embryonic origin of the meninges varies across species. In birds (and probably in mammals), the spinal meninges are derived from the somitic mesoderm, the brainstem meninges from the cephalic mesoderm, and the telencephalic meninges from the neural crest. Differentiation of the meninges, which involves formation of the subarachnoid space, occurs early, before the cerebrospinal fluid (CSF) begins to flow around the CNS. During ontogenesis, the meninges play a key role in regulating the growth of underlying nervous structures. They induce the formation of the superficial glial limiting layer and stimulate the growth of precursors located in the superficial blastemas of the cerebellum and hippocampus. The choroid plexuses are complex specialized structures that produce most of the CSF. Their epithelium derives from the neural tube epithelium and their mesenchyma from the meninges. Of the many enzymes produced in the choroid plexuses, some reflect the pivotal metabolic role of these structures (alkaline and acid phosphatases, magnesium-dependent ATPase, glucose-6-phosphatase, thiamine pyrophosphatase, adenylate cyclase, oxidoreductase, esterases, hydrolases, cathepsin D, and glutathion S-transferase). The two enzymes that are crucial to the production of CSF are Na+/K+ ATPase and carbonic anhydrase. Inactivation of catecholamines is mediated by catechol-O-methyltransferase and by the monoamine oxidases A and B. The morphology and synthesis profile of the choroid plexuses changes during development, although little is known about these changes in humans.
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PMID:Embryonic and fetal development of structures associated with the cerebro-spinal fluid in man and other species. Part I: The ventricular system, meninges and choroid plexuses. 975 71

This study was designed to investigate the possible oxidative changes associated with alterations in cytochrome P450 levels in rat liver. Accordingly, extent of peroxidative processes, cytochrome and antioxidant content, capacity to face an oxidative stress were determined in liver microsomes, mitochondria, and homogenates from normal and phenobarbital (PB)-treated rats. Liver content of microsomal and mitochondrial proteins was also determined by the values of the activities of marker enzymes (glucose-6-phosphatase and cytochrome oxidase, respectively) in liver homogenate and in two cellular fractions. The increase in the liver content of microsomal and mitochondrial proteins indicated that PB caused proliferation of both smooth endoplasmic reticulum and mitochondrial population. Treatment with PB also gave rise to a general increase in peroxidative reactions (evaluated measuring malondialdehyde and hydroperoxides (HPs)), in the different cell compartments, even though HPs were not found significantly increased in mitochondrial fraction. The increase in peroxidative processes was associated with significant decreases in antioxidant concentration (expressed in terms of equivalent concentration of an antioxidant, such as the desferrioxamine), in all preparations from PB-treated rats. The response to oxidative stress in vitro (evaluated determining the parameters characterizing light emission from preparations stressed with sodium perborate) showed a substantial PB-induced increase in the susceptibility to oxidative challenge only in liver homogenate. The lack of changes in the mitochondrial preparations is likely due to decrease in concentration of both free radical producing species and antioxidants. The lack of changes in microsomal fraction is apparently in contrast with its lower oxidant capacity and higher content of cytochromes which are able to determine sensitivity to pro-oxidants. However, it could be due to the ability of cytochrome P450 to interact with the active oxygen species formed at its active center.
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PMID:Effect of phenobarbital treatment on characteristics determining susceptibility to oxidants of homogenates, mitochondria and microsomes from rat liver. 994 58

We sought a rapid and non-ultracentrifugal method of recovering large amounts of highly pure rough endoplasmic reticulum (RER) membranes from livers. By substantially modifying a 20-year-old calcium precipitation technique, we obtained a RER fraction from rat liver and established its high degree of purity by quantitating classic membrane markers for different subcellular organelles. This RER fraction is highly enriched in four known proteins (or enzyme activities) required for lipoprotein assembly: apolipoprotein B, microsomal triglyceride transfer protein, acyl CoA:diacylglycerol acyltransferase, and acyl CoA:cholesterol acyltransferase, when compared to two classical RER markers, RNA and glucose-6-phosphatase. From one 10-12 g rat liver, we recover ten to twelve RER pellets of 1.5-1.6 cm in diameter containing approximately 110-125 mg of total protein, about half of which is sodium carbonate-releasable. By electron microscopy, these large RER pellets from rat livers are homogeneously comprised largely of non-vesiculated short strips of ribosome-rich membranes. This novel technique for isolating RER membranes from liver may provide a useful tool for future studies on the assembly of apolipoprotein B-containing lipoproteins as well as for research focused on mechanisms of secretory and membrane protein translation, translocation, and folding.
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PMID:A rapid calcium precipitation method of recovering large amounts of highly pure hepatocyte rough endoplasmic reticulum. 1035 46


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