Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0019204 (hepatocellular carcinoma)
 71,386 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The increase in tyrosine aminotransferase activity which occurs in rat hepatoma tissue culture (HTC) cells in response to cyclic AMP analogs has been shown to be an enzyme induction, similar to the larger response observed in certain other hepatoma cells and in liver. A specific antibody to tyrosine aminotransferase has been used to show that the number of enzyme molecules and the rate of enzyme synthesis are increased by N6,O2'-dibutyryl cyclic AMP in HTC cells. The effect on tyrosine aminotransferase is also produced by various 8-substituted derivatives of cyclic AMP and occurs whether or not the enzyme has been preinduced with a glucocorticoid. The response of the enzyme is greater when HTC cells are maintained in monolayer than in suspension cultures. Neither cell growth nor serum is required for the response.
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PMID:The influence of culture conditions on the induction of tyrosine aminotransferase by cyclic nucleotides in rat hepatoma cells. 1 19

Asparagine synthetase (L-aspartate:ammonia ligase (AMP-forming, EC 6.3.1.1) activity in rat liver increased when the animals were put on a low casein diet. The enzyme was purified about 280-fold from the supernatant of rat liver homogenate by a procedure comprising ammonium sulfate fractionation. DEAE-Sepharose column chromatography, and Sephadex G-100 gel filtration. The optimal pH of the enzyme was in the range 7.4-7.6 with glutamine as an amide donor. The molecular weight was estimated to be approximately 110,000 by gel filtration. Chloride ion was required for the enzyme activity. The apparent Km values for L-aspartate, L-glutamine, ammonium chloride, ATP, and Cl- were calculated to be 0.76, 4.3, 10, 0.14, and 1.7 mM, respectively. The activity was inhibited by L-asparagine, nucleoside triphosphates except ATP, and sulfhydryl reagents. It has been observed that the properties of asparagine synthetase from rat liver are not so different from those of tumors such as Novikoff hepatoma and RADA 1.
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PMID:Purification and properties of asparagine synthetase from rat liver. 2 63

Analogs of cyclic AMP elevate the synthesis of tyrosine aminotransferase (L-tyrosine:2-oxoglutarate aminotransferase; EC 2.6.1.5) in cultured hepatoma cells and rat liver at a post-transcriptional level but have no discernible effect on total soluble protein synthesis. In order to determine whether cyclic AMP exerts its effect on a step before or after initiation of the synthesis of this enzyme, we have analyzed the ribosomal transit times for both the aminotransferase and total soluble protein in hepatoma cells incubated in the presence or absence of N(6),O(2)'-dibutyryl cyclic AMP. The time required for one ribosome to translate one subunit of the "average" soluble protein (transit time) was about 2 min in cells incubated with or without the cyclic AMP analog. In contrast, the transit time for tyrosine aminotransferase was found to be reduced from 5-8 min under basal conditions to as low as 45 sec after exposure to dibutyryl cyclic AMP. Although the degree of effect varied from experiment to experiment, the relative rate of aminotransferase nascent chain elongation was found to be proportional to the stimulation of its activity. In contrast, dexamethasone did not alter the rate of aminotransferase elongation even though it elevated enzyme activity between 5- and 10-fold. These data are consistent with the hypothesis that induction of tyrosine aminotransferase with cyclic AMP analogs occurs by stimulation of the rate at which ribosomes translate pre-existing mRNA in contrast to adrenal steroids which act by increasing the level of translatable mRNA coding for this enzyme.
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PMID:Evidence for acceleration of the rate of elongation of tyrosine aminotransferase nascent chains by dibutyryl cyclic AMP. 2 12

Tyrosine adminotransferase (EC 2.6.1.5) has been found to be phosphorylated in intact rat hepatoma cells in culture. Incorporation of [32p]i into the enzyme is rapid and is exclusively found as phosphoserine. Cycloheximide treatment reduced phosphorylation of the aminotransferase only slightly and in the presence of three different inducers of this enzyme, dexamethasone, insulin, and dibutyryl cyclic AMP, [32P]I incorporation was increased. It is concluded that [32p]i incorporation into this enzyme probably reflects turnover of phosphate groups associated with pre-existing enzyme molecules catalyzed by a cyclic AMP-independent protein kinase.
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PMID:Relationship between phosphorylation of tyrosine aminotransferase and regulation of its synthesis by cyclic AMP and hormones. 2 2

Activity of 5'-nucleotidase was significantly lower in plasmatic membranes of highly malignant hepatoma 22 as compared with the activity found in normal liver tissue. The optimal activity of the enzyme from hepatoma 22 was found at pH 8.5 with AMP as a substrate. Decrease of pH value from 8.5 to 7.4 did not affect the enzymatic activity in homogenates and plasmatic membranes in the normal liver tissue. In all the experiments activity of 5'-nucleotidase was lower towards CMP as compared with AMP. The additive effect of the both substrates was observed only in experiments with hepatoma 22.
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PMID:[Comparison of the activity and properties of 5'-nucleotidase in the homogenates and plasma membranes of the normal liver, hepatomas and of the liver in mice with inoculated hepatomas of varying degrees of malignancy]. 4 19

Intracellular and extracellular levels of 3':5'-cyclic GMP and 3':5'-cyclic AMP were studied in synchronized Novikoff rat hepatoma cells. Intracellular levels of cyclic GMP increased spontaneously from 2-fold (without colcemid) to 10-fold (with colcemid), in proportion to the number of cells in mitosis. As cells entered mitosis, cellular cyclic AMP declined simultaneously with the rise in cyclic GMP. These reciprocal changes in cyclic nucleotide levels were reversed as cells passed out of metaphase and through anaphase. Maximum cyclic AMP and minimum cyclic GMP concentrations occurred during G-1. Less marked reciprocal fluctuations in both cyclic nucleotides were also found in S-phase and early G-2, where the ratio of cyclic AMP to cyclic GMP concentrations first fell and then increased. These changes in cyclic nucleotide ratios were closely correlated with major cell-cycle transitions at the boundaries between G-1/S-phase, S-phase/G-2, G-2/prophase, and metaphase/anaphase. Most, but not all, of the extracellular cyclic nucleotides were extruded when cells traversed mitosis. Colcemid or vinblastine completely prevented the appearance of extracellular cyclic AMP but augmented the appearance of extracellular cyclic GMP in parallel with the accumulation of mitotic cells. These results reflected changes in intracellular cyclic nucleotides and indicated that increased intracellular turnover of cyclic GMP and cyclic AMP occurred before and after metaphase, respectively. Elevated cyclic GMP levels during mitosis and S-phase are consistent with potential modulatory roles for this cyclic nucleotide in proliferation.
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PMID:Cell-cycle-related changes of 3':5'-cyclic GMP levels in Novikoff hepatoma cells. 6 82

Three ascites hepatoma cells of the rat, AH-41B, AH-34, and AH-64B, which had been determined in vivo as alpha-fetoprotein-negative, were cultivated in vitro in a medium containing adenosine 3',5'-cyclic monophosphate (cyclic AMP), cyclic dibutyryl-AMP, or theophylline. The concentration of alpha-fetoprotein in culture media was measured by the 125 I-radioimmunoassay. Results demonstrated that the AH-41B cells produced alpha-fetoprotein in vitor, the concentration of which being elevated in the media with three substances, while the remaining AH-34 and AH-64B cells did not. A comment was made on the producibility of alpha-fetoprotein in the so-called alpha-fetoprotein-negative hepatoma cells.
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PMID:Production of alpha-fetoprotein by cultured rat ascites hepatoma cells determined in vivo as alpha-fetoprotein-negative. 7 15

Full-length radiolabeled albumin and alpha-fetoprotein (AFP) cDNAs were synthesized from pure albumin and AMP mRNA preparations by using avian myeloblastosis virus reverse transcriptase (RNA-dependent DNA polymerase). The cDNAs have been used to quantitate the number of albumin and AFP genes in different rat tissues by two independent methods, both of which yielded similar results. First, the kinetics of the association of these cDNAs with nuclear DNA from rat liver, rat kidney, and Morris hepatoma 7777 under conditions of vast DNA excess indicated that the albumin and AFP mRNA's are transcribed from "nonrepetitive DNA." Second, saturation hybridization experiments in which a constant amount of rat liver DNA or Morris hepatoma 7777 was hybridized with increasing amounts of cDNA to albumin mRNA have shown the presence of 1--2 albumin genes per rat haploid genome. The number of AFP genes obtained in similar titration experiments was approximately 2--3. This was true whether rat liver DNA or hepatoma 7777 DNA was used in the reassociation experiments. When high molecular weight DNA preparations from both these tissues were digested with the restriction endonuclease EcoRI and the fragments were transferred to a nitrocellulose filter, the albumin and AFP [32P]cDNA probes hybridized to different sets of DNA fragments. However, each probe gave the same hybridization pattern whether Buffalo rat liver DNA or hepatoma 7777 DNA was utilized.
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PMID:alpha-Fetoprotein and albumin genes of rats: no evidence for amplification-deletion or rearrangement in rat liver carcinogenesis. 8 3

Selected biochemical properties, based on hepatocellular function, were assessed in the mouse hepatoma BW7756 and host and/or normal mouse liver. These biochemical properties included (a) alpha-fetoprotein (AFP) production, (b) lipid composition, (c) isozyme patterns and enzyme activities, and (d) cyclic AMP levels. The tumor evidenced an exponential growth phase and vigorous production of AFP in the first 3 weeks following transplant. The concentration of AFP in the sera of tumor-bearing mice increases roughly with the growth of the hepatoma. The percentage of total lipid in the hepatoma was greater than in either normal or host liver; however, the liver displayed more phospholipid than the tumor, while more triglyceride was demonstrable in the hepatoma. Of the 17 isozyme patterns analyzed, seven--acid phosphatase, malate dehydrogenase, aspartate amino-transferase, glucose-6-phosphate dehydrogenase, esterase, lactate dehydrogenase, and xanthine dehydrogenase--were different in the liver and the tumor. The cyclic AMP levels decreased in the tumor and the host spleen from day 10 to day 21; however, slight increases were noted in the tumor and host spleen and liver at day 28. These studies suggested 2--3 weeks posttransplantation as the optimal time for investigational use of this hepatoma.
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PMID:Characterization of murine hepatoma BW7756. I. Selected biochemical properties of liver and hepatoma. 8 49

Nutrient transport rates and cyclic AMP levels have been implicated in the regulation of cell proliferation. In the present study, however, changes in intracellular cyclic AMP level in several lines of cultured cells (normal 3T3 and SV40 and polyomavirus-transformed 3T3 cells; 3T6, C6 GLIOMA, MOUSE L, and Novikoff rat hepatoma cells) by treatment with papaverine, prostaglandine E1 or isoproterenol did not correlate with the inhibition of the uridine, hypoxanthine or deoxyglucose transport rates by these chemicals. Transport inhibitions by above chemicals or Persantin or Cytochalasin B occurred in most cell lines in the absence of any measurable change in intracellular cyclic AMP concentration. Furthermore, treatment of several cell lines with 1 mM dibutyryl cyclic AMP had no immediate effect on the transport of uridine, thymidine or deoxyglucose, although the transport capacity of the cells for uridine and thymidine, but not that for deoxyglucose, decreased progressively with time of treatment. We also observed that the uridine transport system of all cell lines derived from 3T3 cells and the hypoxanthine transport system of L cells exhibited high degrees of resistance to inhibition by the various chemicals. On the other hand, deoxyglucose transport was inhibited to about the same extent by these chemicals in all the cell lines investigated.
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PMID:Cyclic AMP, membrane transport and cell division. I. Effects of various chemicals on cyclic AMP levels and rate of transport of neucleosides, hypoxanthine and deoxyglucose in several lines of cultured cells. 16 72


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