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)

A procedure is described for the preparation of a membrane fraction enriched in basal-lateral plasma membranes from gastric mucosa. Gastric glands isolated from rabbit were employed as starting material, greatly reducing contamination from non-glandular cell types. The distribution of cellular components during the fractionation procedure was monitored with specific marker enzymes. (Na+ + K+)-ATPase, ouabain-sensitive K+-stimulated p-nitrophenyl-phosphatase and histamine-stimulated adenylate cyclase were used as markers for basal-lateral membranes. These three markers were similarly distributed during both differential and equilibrium density gradient centrifugation. The enriched membrane fraction contained more than 30% of the total initial activities of the three basal-lateral membrane markers which were purified better than 11-fold with respect to protein. (Na+ + K+)-ATPase activity was resolved from the activities of acid phosphatase, pepsin, Mg2+-ATPase, cytochrome c oxidase, NADPH-cytochrome c reductase, glucose-6-phosphatase, (K+ + H+)-ATPase, DNA and RNA.
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PMID:An enriched preparation of basal-lateral plasma membranes from gastric glandular cells. 626 84

The binding characteristics of hGH to Golgi and liver plasma membranes isolated from normal adult female rats have been compared to assess the biological differences between the Golgi and plasma membrane receptor. The effect of cations and the time course of binding were qualitatively similar for both Golgi and plasma membranes. The Golgi membranes from normal rats exhibited maximum binding at pH 6-7 compared to 5-6 for other membrane fractions. The highest apparent affinities (approx. 1 x 10(9) M-1) for hGH were observed in the light Golgi membranes from normal rats and the light and intermediate Golgi membranes from ethanol treated rats. The lowest apparent affinities (0.026 -0.1 x 10(9)M-1 if determined by competitive binding curves or 0.07 - 0.32 x 10(9)M-1 by Scatchard plots) for hGH were observed in plasma membranes isolated by either Neville's or Ray's method or a combination of both methods. The hGH receptors were determined to be lactogenic by competitive binding curves. The affinities of Golgi membranes were not affected by alterations in isolation procedures. Ethanol treatment of the rats prior to sacrifice and membrane isolation resulted in linear Scatchard plots for hGH binding to Golgi membranes compared to curved Scatchard plots for the Golgi membranes of normal rats. The marker enzyme activities of glucose-6-phosphatase and adenylate cyclase were lower in Golgi from ethanol treated rats while the galactosyl transferase activity increased in lighter golgi fractions from ethanol treated rats.
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PMID:Comparison of human growth hormone binding to rat liver plasma and Golgi membranes. 627 78

Although there is some evidence that extrachoroidal sites for the production of cerebrospinal fluid (CSF) are important, the choroid plexuses in the ventricles contribute the major part of CSF formation. The exact mechanism for CSF production is not fully understood. In order to study this mechanism from the enzyme histochemical standpoint, the previously reported studies are reviewed, in addition to the authors' own electron microscopic enzyme histochemical observations on this tissue. The ultrastructure and enzyme biochemistry of choroid plexus epithelial cells are considered, together with the histochemistry of the following enzymes: alkaline and acid phosphatase, Mg2+-ATPase, Na+, K+-ATPase, glucose-6-phosphatase, thiamine pyrophosphatase, adenylate cyclase, carbonic anhydrase, oxidoreductase, esterase, several hydrolases, and other enzymes. Finally, CSF formation and active transport in the choroid plexus epithelial cells are discussed, mainly in terms of the results of our enzyme cytochemical observations on Na+, K+-ATPase and carbonic anhydrase in this tissue.
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PMID:The enzyme histochemistry of the choroid plexus. 683 Nov 99

Hepatocytes, endothelial and Kupffer cells were isolated from young adult (3 month) and old (24 month) rat livers and the activities of some plasma membrane, endoplasmic reticulum, mitochondrial, lysosomal and soluble enzymes compared using biochemical and electron microscope cytochemical techniques. Age-associated changes included: a decrease in glucose-6-phosphatase activity both in hepatocytes and sinus lining cells; and increase in alkaline phosphatase in endothelial cells but a decrease in hepatocytes; reduced basal and glucagon-induced adenyl cyclase in hepatocytes and endothelial cells and an increase in the number of hepatocytes with gamma-glutamyl transferase reaction. Cytochemistry showed that heterogeneity may also be characteristic of senescence particularly with regard to hepatocyte glucose-6-phosphatase which was absent in some cells, low in many cells but high in some and gamma-glutamyl transferase which was normally lacking from hepatocytes but localised as large deposits of reaction product on the plasma membranes of occasional cells isolated from old donors.
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PMID:Effects of age on rat liver enzymes. A study using isolated hepatocytes, endothelial and Kupffer cells. 706 Sep 52

Hepatocarcinogenesis in hepatitis B virus transgenic mice was studied by means of a correlative cytomorphological and cytochemical approach at different time points in animals from 1 to 34 mo old. HBsAg-positive ground-glass hepatocytes emerged throughout the liver parenchyma in nearly all transgenic mice during the first 4 mo after birth. The panlobular expression of HBsAg persisted until foci of altered hepatocytes appeared (6 to 9 mo of age). Three different types of foci of altered hepatocytes-namely, glycogen-storage foci, mixed cell foci and glycogen-poor foci-developed. Hepatocellular adenomas and carcinomas appeared after 11 mo. Orcein staining revealed frequent transitions between ground-glass hepatocytes extensively expressing HBsAg and glycogen-storage (predominantly clear-cell) foci containing HBsAg-positive cytoplasmic components. Similar transitions between ground-glass hepatocytes and glycogenotic (clear) cells were often found in diffuse parenchymal glycogenosis at 11 or 12 mo. Remnants of HBsAg-positive material were also detected in mixed cell foci, glycogen-poor diffusely basophilic cell foci, hepatic adenoma and hepatocellular carcinoma. These findings suggest that ground-glass hepatocytes are the direct precursor of foci of altered hepatocytes and their neoplastic descendants. The extensive expression of HBsAg is gradually down-regulated during neoplastic transformation, just as the morphological the biochemical phenotypes of foci of altered hepatocytes, hepatic adenoma and hepatocellular carcinoma in transgenic mice resemble those described in chemical hepatocarcinogenesis. The predominant sequence of cellular changes leading from glycogen-storage (predominantly clear cell) foci to mixed cell foci, hepatic adenoma and hepatocellular carcinoma is characterized by a gradual decrease in the activities of glycogen synthase, phosphorylase, glucose-6-phosphatase and adenylate cyclase, whereas glucose-6-phosphate dehydrogenase and pyruvate kinase activities increase. These alterations indicate a shift from the glycogenotic state toward an increase in the pentose phosphate pathway and glycolysis.
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PMID:Hepatic preneoplasia in hepatitis B virus transgenic mice. 792 48

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

An immortalized cell line, called P9, was derived from hepatocytes by transfection with SV40 DNA. These cells expressed enzyme activities characteristic of hepatocytes, namely glucose-6-phosphatase, glycogen phosphorylase, bilirubin glucuronyltransferase and both glucagon- and prostaglandin E1 (PGE1)-stimulated adenylate cyclase activities, albeit at decreased levels compared with native hepatocytes. Levels of the G-protein subunits alpha-Gi-2, alpha-Gi-3, G beta and the 'long' form of alpha-G2 (45 kDa) were approximately 4-fold higher relative to native hepatocytes, whereas those of the 'short' form of alpha-G2 (42 kDa) were lower by approximately 40%. Associated with this were marked alterations in the guanine nucleotide regulation of adenylate cyclase. Receptor-mediated stimulation, achieved by either PGE1 or glucagon, was apparent in P9 cells, although the latter was only evident upon amplification with forskolin. Glucagon-stimulated cyclic AMP accumulation in P9 cells did not exhibit desensitization, as in hepatocytes, nor was the phosphorylation of alpha-Gi-2 evident. Culture of P9 cells with insulin led to a dose-dependent decrease (EC50 0.2 +/- 0.1 nM) in the ability of PGE1 to stimulate adenylate cyclase activity, with the maximum effect attained after approximately 6 h. A comparable attenuation of stimulation was seen for glucagon- and guanine-nucleotide-stimulated adenylate cyclase activities. In cells cultured with insulin, lower levels of GTP were required to stimulate adenylate cyclase, ADP-ribosylation of the 45 kDa form of alpha-Gs with cholera toxin was attenuated, and the expression of both alpha Gi-2 and alpha-Gi-3 was increased. It is suggested that the expression of alpha-Gi-2 and alpha-Gi-3 may be directly regulated by the action of insulin in hepatocytes and P9 cells.
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PMID:Analysis of the adenylate cyclase signalling system, and alterations induced by culture with insulin, in a novel SV40-DNA-immortalized hepatocyte cell line (P9 cells). 801 Sep 67

The crude membrane fraction of cardiomyocytes, which had been used as the antigen for the study of autoantibodies against beta-adrenergic receptors, was characterized using cytochemical methods: in a reaction for adenylate cyclase as an enzyme marker of the beta-receptors of plasma membrane and in a reaction for glucose-6-phosphatase as an enzyme marker of the sarcoplasmic reticulum. The specific precipitates of both enzyme reactions were localized on the membrane vesicles. In case of AC reaction the precipitate was observed on approximately 80% and in case of G-6-Pase on approximately 25% of the whole amount of the vesicles observed, indicating prevalence of vesicles of plasmalemmal origin. These results reveal that the used membrane fraction is appropriate for the study of autoantibodies against beta-receptors, but it can also contain other proteins (antigens) which can cross-react with autoantibodies against beta-adrenergic receptors.
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PMID:Characterization of the crude membrane fraction of cardiomyocytes using enzyme cytochemical markers. 826 66

As demonstrated previously, liver acini draining the blood from intraportally transplanted pancreatic islets in streptozotocin-diabetic rats are altered in various respects. The hepatocytes in these acini store glycogen and/or fat, and they show an increase in proliferation as well as in apoptotic activity. Thus, they are phenotypically similar to carcinogen-induced preneoplastic liver foci (glycogen-storing foci and sometimes also mixed cell foci). By means of catalytic enzyme histochemistry or immunohistochemistry, we investigated the activity of key enzymes of alternative pathways of carbohydrate metabolism and some additional marker enzymes (well known from studies on preneoplastic hepatic foci) in the altered liver acini surrounding the islet isografts. In addition, the expression of glucose transporter proteins 1 and 2 (GLUT-1 and GLUT-2) were investigated immunohistochemically. The activities of hexokinase, pyruvate kinase, glyceraldehyde-3-phosphate dehydrogenase, and glucose-6-phosphate dehydrogenase were increased, whereas the activities of glycogen phosphorylase, adenylate cyclase, glucose-6-phosphatase, and membrane-bound adenosine triphosphatase were decreased in the altered liver acini. The expression of GLUT-2 was also decreased. GLUT-1 and glutathione S-transferase placental form were not expressed, and the activities of glycogen synthase and gamma-glutamyl-transferase remained unchanged. All changes of the enzyme activities were in line with the well known effects of insulin and resembled alterations characteristic of preneoplastic liver foci observed in different models of hepatocarcinogenesis. It remains to be clarified in long-term experiments whether or not these foci represent preneoplastic lesions and may proceed to neoplasia.
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PMID:Altered liver acini induced in diabetic rats by portal vein islet isografts resemble preneoplastic hepatic foci in their enzymic pattern. 864 65

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


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