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)

Studies on the properties and isoenzymic content of glucose-6-phosphatase (E. C. 3.1.3.9.) of normal and tumor cells microsomes allowed the following conclusion to be made: the localization of the enzyme in the membranes of endoplasmatic reticulum of both types of cells is identical. The tumor microsomes are characterized (irrespective of the blastomogenic factor inducing them) by a decreased activity of the enzyme at pH 6.75, a relatively increased activity of the latter at pH 7.5. Solubilization of the enzyme was performed by a new technic i. e. the acetone treatment of microsomes. Rechromatography of most active fractions on Sephadex G-200 has revealed less number of the enzyme isoforms of tumor cell microsomes.
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PMID:[Properties and isoenzyme contents of glucose-6-phosphatase of normal and tumor cell microsomes]. 22 95

Evidence is presented that the antitumor agent helenalin, a sesquiterpene lactone, suppresses anaerobic glycolytic enzymes of tumor cells at a number of sites and not exclusively at glycogen synthetase and phosphofructokinase, previously proposed sites for inhibition by alpha-methylene-gamma-lactones. Of the enzymes tested, the sulfhydryl-containing enzyme hexokinase was inhibited the maximum, i.e., 83%, by helenalin treatment, whereas phosphofructokinase and glycogen synthetase were suppressed approximately 45%. Another sulfhydryl-bearing enzyme, aldolase, was decreased approximately 43%. Phosphorylase a was inhibited 65%, glucose-6-phosphatase was inhibited 46%, and succinic dehydrogenase was inhibited 59% by helenalin treatment. Mitochondrial oxidative phosphorylation processes were also significantly depressed in the presence of helenalin in vitro with either succinate or alpha-ketoglutarate as substrates. Thus, a number of enzymes of anaerobic and aerobic carbohydrate metabolism of Ehrlich ascites cells appear to be inhibited by helenalin, which supposedly can alkylate functional groups, e.g., sulfhydryl groups of these enzymes, by a rapid Michael-type addition.
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PMID:Antitumor agents XXVII: Effects of helenalin on anaerobic and aerobic metabolism of Ehrlich ascites cells. 64 68

The modifying action of chronic liver injury on the process of hepatocarcinogenesis was investigated. To induce cirrhosis or fibrosis F344 rats received CCl4 alone or in combination with phenobarbital, either before (model 1) or after (model 2) the application of initiator, diethylnitrosamine (DENA). In these models, morphology, tumor incidence as well as polysubstrate monooxygenase system, gamma-glutamyltransferase (GGT) and glucose-6-phosphatase (G-6-Pase) were studied. The data presented show that in model 1 the tumor incidence was much lower than in rats treated with DENA alone. This reduction appeared to be associated with the decrease in cytochrome P450 content occurring in model 1 after DENA administration. Promotion of the hepatocarcinogenic process was observed when CCl4 injury followed the application of DENA (model 2). Comparison of marker enzymes in cirrhotic livers and in tumors either with or without cirrhosis indicated that changes in cytochrome P450 and G-6-Pase were rather the results of parenchymal damage, while GGT was elevated only in tumorous livers. In tumorous livers none of the xenobiotic metabolizing activities decreased as much as the cytochrome P450 content of the same samples. Thus conceivably the cytochrome P450 operates more rapidly in tumors than in normal livers.
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PMID:Modification of DENA-induced hepatocarcinogenesis by CCl4 cirrhosis. Comparison of the marker enzyme patterns. 135 Feb 34

Positron emission tomography (PET) fluorodeoxyglucose (FDG) studies are useful for identifying foci of increased FDG uptake in liver metastases, because of the high glycolytic rate of malignancies, as well as for monitoring changes in tumor glucose metabolism during treatment. We performed 15 kinetic PET FDG studies in four patients with metastatic liver disease. We produced parametric images of glucose metabolism in terms of the rate constant K (ml/min/g) for net phosphorylation of FDG. Tumor K values, estimated with nonlinear regression, correlated well with K values estimated with Patlak graphical analysis (r = 0.96), validating the assumption of low k4* values in liver metastases and supporting the use of pixel by pixel Patlak plot analysis of the data to generate parametric images. In normal liver, high levels of glucose-6-phosphatase produce much higher values of k4* than in liver metastases. Uncorrected Patlak graphical analysis underestimates K in normal liver, but this further increases the contrast between tumor and liver and facilitates both tumor detection and quantification. The technique is computationally feasible and is well suited for serial evaluations of tumor metabolism during treatment.
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PMID:Quantification of glucose utilization in liver metastases: parametric imaging of FDG uptake with PET. 152 57

Tumor uptake of 18F-fluorodeoxyglucose (FDG) was studied by dynamic positron emission tomography (PET) in 23 cases of hepatocellular carcinoma. The metabolic rate constants, K1 to K4, were generated by non-linear least square fitting method. We confirmed that K3 from the PET study significantly correlated with directly measured hexokinase activity of the cancer tissue. The region of HCC always had higher K3 values, which represents the hexokinase activity compared with the non-cancerous region. By FDG images, however, in 50% of cases the cancer region could not be clearly defined from the surrounding noncancerous hepatic tissue. These HCC cases without accumulation of FDG had a high ratio of K4/K3 (K4 represents glucose-6-phosphatase activity), which correlated well with the inverse ratio of FDG accumulating images on PET. According to the PET images which is represented by K4/K3 and the hexokinase activity which is represented by K3, we divided these 23 cases into three groups and retrospectively compared their survival rates. The groups with high K4/K3 (greater than or equal to 0.40) had longer survival than other groups. From the view point of glucose metabolism, the value of K4/K3 calculated from dynamic studies of FDG-PET may represent the functional differentiation of HCC.
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PMID:[Can fluorodeoxyglucose-positron emission tomography evaluate the functional differentiation of hepatocellular carcinoma]. 166 76

The cellular origin of estrogen-induced kidney tumors in male Syrian hamsters has been repeatedly the subject of controversy. Several authors have proposed that the tumors arise from proximal tubules, from a combination of tubular and interstitial stromal cells, or solely from interstitial cells. Because of the model character of this tumor for hormone-associated cancer, it was further investigated in this study with respect to morphology, enzyme and intermediate filament pattern, the expression of alpha-smooth muscle actin and the extracellular matrix proteins fibronectin and tenascin. These analyses were carried out with early and late tumors as well as metastases to determine possible changes in expression of biochemical parameters during the development and progression of this neoplasm. The enzyme histochemical and intermediate filament patterns were usually the same as those described previously for proliferative foci and early tumors, i.e. highly elevated activities of glucose-6-phosphate dehydrogenase, adenylate cyclase and alkaline phosphatase, a lack of glucose-6-phosphatase and gamma-glutamyltransferase and coexpression of vimentin and desmin, alpha-smooth muscle actin could not be detected in early lesions. In five of 24 advanced tumors inclusions of kidney tubules were found which showed various degrees of alteration in their morphology and enzyme histochemical pattern, but were often directly connected with tubular segments of normal appearance outside the tumor. Like the normal tubules, the enclosed tubular segments were strongly positive for cytokeratin but never expressed vimentin or desmin. Among the 24 tumors studied, two contained cysts which expressed cytokeratin and sometimes also vimentin but not desmin. The enzyme histochemistry of the cells lining the cysts was similar to that of the surrounding tumor mass, except adenylate cyclase was lacking and alkaline phosphatase was not uniformly distributed. In tumors containing cytokeratin-positive cysts, there often were cytokeratin-positive, vimentin-negative and desmin-negative tumor formations in close contact to these cysts. With the exception of cyst formation, the pattern of metastases were identical to that of the primary tumors. All large tumors and the main component of the metastases expressed vimentin, desmin and fibronectin. Mesothelia surrounding metastatic tumor complexes were positive for vimentin, desmin, alpha-smooth muscle actin, fibronectin, cytokeratin and tenascin. It was concluded from these and previous observations on early stages of tumor development that the estrogen-induced hamster kidney tumor originates from mesenchymal interstitial cells (probably pericytes) which may rarely acquire an epithelial phenotype by metaplastic transformation during tumor progression.
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PMID:Changes in the cellular phenotype and extracellular matrix during progression of estrogen-induced mesenchymal kidney tumors in Syrian hamsters. 171 81

The effects of alternating ad libitum feeding and 30% restriction of the dietary intake on the development of diethylnitrosamine (DEN)-induced hepatic neoplasia were investigated. Dietary restriction retarded the growth of glucose-6-phosphatase-deficient (G6Pd) preneoplastic foci and subsequently that of hepatocellular adenomas and adenocarcinomas. The number of foci in standardized liver sections increased from 4.44 foci/cm2 at 12 weeks to 9.65 foci/cm2 at 24 weeks in ad libitum fed animals but only from 2.35 foci/cm2 to 3.29 foci/cm2 in restricted animals. In animals fed first ad libitum for 12 weeks and then for 12 weeks on a restricted diet, the number of G6Pd foci dropped from 4.44 at 12 weeks to 3.54 at 24 weeks. This reduction appeared to be the result of a regression of the small sized G6Pd foci. Dietary restriction was most efficient in inhibiting the development of G6Pd foci when started early in life. Conversely, the growth of foci was stimulated when the mice first had restricted access to food and thereafter were fed ad libitum. The plasma insulin concentrations after a glucose challenge increased with age. Insulinaemia was much higher in ad libitum fed compared to the restricted mice. It was correlated to the number of G6Pd foci in the liver. This study suggests that insulin, which is a known mitogen for hepatocytes in vitro, may contribute to the promotion of DEN-induced liver tumours in mice.
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PMID:The effects of alternating dietary restriction and ad libitum feeding of mice on the development of diethylnitrosamine-induced liver tumours and its correlation to insulinaemia. 184 20

Dichloroacetic acid (DCA) has recently been shown to increase significantly the incidence of hepatic adenomas (HAs) and hepatocarcinomas (HCs) in male B6C3F1 mice. Although little is known about the mechanism of DCA carcinogenesis, chronic ingestion of the compound in drinking water induces primarily hyperplastic nodules (HNs) prior to the appearance of HAs and HCs. Given the putative preneoplastic potential of the HNs, we undertook this study to determine the role of the HNs in the progression of DCA-induced hepatocarcinogenesis. This role was assessed by detecting the expression of five different tumor markers: p21 ras, p39 c-jun, phosphotyrosine, tumor-associated aldehyde dehydrogenase and alpha-fetoprotein, all known from previous studies to be expressed more often in neoplastic liver lesions than in normal liver. Tumor marker expression was detected by immunohistochemical methods using formalin-fixed, paraffin-embedded sections of normal B6C3F1 mouse liver, and DCA-induced HNs, HAs and HCs. The results demonstrated that, except for the c-jun marker, HNs expressed the markers significantly less often than either HAs or HCs. Equal expression of c-jun occurred in any of the three lesion types. Although these results could be used to argue that no relationship existed between HNs and later-appearing HAs and HCs, those HNs that were marker positive contained small nests of marker-positive hepatocytes among a field of normally appearing unstained hepatocytes. No similar nests of marker-positive cells were detected in any area of normal liver outside the HNs. Also very few altered hepatic foci (AF) were detected with these markers or with hematoxylin and eosin, or with histochemical stains for ATPase or glucose-6-phosphatase deficiencies. These results suggested that these nests within some HNs were areas of transformed, or neoplastic hepatocytes. Phenotypic heterogeneity analysis, in which the number of tumor markers co-expressed by any given lesion was examined, confirmed a significantly greater percentage of HAs and HCs expressing multiple markers than HNs. Those HNs that expressed multiple markers, however, expressed at the same frequency as HAs and HCs and the expression was confined to the same nests of cells. Taken together, these data suggest that these nests of marker-positive cells within the HNs were neoplastic and could develop into later-appearing HAs and/or HCs. The absence of marker expression in normal liver and limited expression in the few AF indicates that the HNs may be the only significant preneoplastic lesion in DCA-induced hepatocarcinogenesis.
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PMID:The role of hyperplastic nodules in dichloroacetic acid-induced hepatocarcinogenesis in B6C3F1 male mice. 186 Jan 58

The livers of rats given either the peroxisome proliferating hepatocarcinogen di(2-ethylhexyl)phthalate (DEHP) following initiation by 2-acetylaminofluorene (AAF) or the neoplasm promoter phenobarbital (PB) were studied for changes in 8 histochemical properties. Male F344 rats were fed 200 ppm AAF for 7 weeks to induce hepatocellular altered foci, and were then fed diets containing either no chemical, 12,000 ppm DEHP or 500 ppm PB for 24 weeks. In hepatocytes, DEHP increased alkaline phosphatase activity throughout the lobule, but reduced gamma-glutamyltransferase (GGT) activity in periportal hepatocytes. PB, in contrast, increased GGT activity in periportal hepatocytes. In foci that were induced by AAF, DEHP reduced the histochemical activity of GGT and did not increase the number, mean volume or volume % of foci detected by deficiencies in iron storage, glucose-6-phosphatase, adenosine triphosphatase or fibronectin. PB enhanced the expression of all 8 phenotypic abnormalities in foci such that either more profiles were detected or the area of foci was increased.
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PMID:Effects of the peroxisome proliferator di(2-ethylhexyl)phthalate on enzymes in rat liver and on carcinogen-induced liver altered foci in comparison to the promoter phenobarbital. 197 53

The ability of methyl-deficient, amino-acid-defined diets to produce enzyme-altered foci was quantitatively determined in the livers of rats treated both with and without an initiating dose of diethylnitrosamine (DEN). Male weanling F-344 rats were fed a complete, amino-acid-defined diet for 1 week. They were then injected i.p. with a single dose of DEN (20 mg/kg body weight) and fed the complete diet for an additional week. Forty animals in each dose group were then maintained for 5-38 weeks on the complete diet (diet 1) or one of the three methyl-deficient diets customarily used in this laboratory: diet 2, devoid of methionine and choline; diet 3, devoid of methionine only; and diet 4, devoid of choline only. In diets 2 and 3, methionine was replaced by equimolar amounts of its metabolic precursor, DL-homocystine. Ten animals per group were killed 8, 12, 17, 24 and 41 weeks after DEN initiation. For 2 weeks prior to being killed, each group was maintained on the complete diet to minimize the histological abnormalities due to acute toxicity of the diets. Serial sections of the livers were obtained, stained sequentially for gamma-glutamyltranspeptidase, ATPase and glucose-6-phosphatase, and the quantitation of the focal lesions scored by these markers was carried out by quantitative stereology. The results indicated that, regardless of the enzyme marker(s) examined, there was a general correspondence between the volume and number of altered hepatic foci (AHF) formed and the previously described tumor-promoting activities of each diet. Thus, while all DEN-treated groups contained significant numbers of AHF 24 weeks after initiation, only the diet-2-fed animals displayed such foci at 8 weeks. Similarly, among the uninitiated rats, only those fed diet 2 exhibited the presence of AHF throughout the experimental period. Interestingly, the livers of uninitiated, choline-deficient rats showed a small number of AHF at 24 and 42 weeks; these foci were not observed at all in the corresponding DEN-untreated animals fed diet 3, deficient in methionine only. The results provide evidence that the carcinogenic effects of the methionine- and choline-deficient diet result more from its strongly promoting effect than from any initiating activity by the diet.
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PMID:The effect of choline and methionine deficiencies on the number and volume percentage of altered hepatic foci in the presence or absence of diethylnitrosamine initiation in rat liver. 230 54


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