Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0017638 (glioma)
 30,880 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two types of tumour cell have been obtained from a glioma transplacentally induced by ethylnitrosourea in a BD-IX rat. These were distinguished in culture by their different morphologies, responses to dibutyryl cyclic adenosine monophosphate, inducibility of glycerol phosphate dehydrogenase and growth in soft agar. They had different karyotypes, with distinctive numbers and arrangements of chromosomes. One cell type had an apparently normal diploid set of 42 whilst the other had 43 chromosomes. An additional chromosome No 4 was identified in the latter by Giemsa banding. Translocations and other abnormalities involving this chromosome were consistently observed. Both cell types produced malignant, astrocytic tumours when injected into newborn syngeneic rats, but with different latent periods and morphological features.
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PMID:Cellular heterogeneity in an ethylnitrosourea-induced glioma: malignancy, karyology and other properties of tumour cell types. 22 Oct 2

The tricyclic antidepressant desipramine, when added to culture medium, gave rise in C6 rat glioma cells to a decrease of the activity of the enzyme asialofetuin sialyltransferase. The inhibition was dose and time dependent and was observed in both multiplying cells and cells blocked with 2 mM thymidine or depletion of amino acids. This inhibition was rather specific to the sialyltransferase, as under the conditions where this enzyme was inhibited up to 70%, other enzymes such as dolichol phosphate mannose synthetase, glutamine synthetase, and glycerol phosphate dehydrogenase remained unaffected. This inhibition was not reversed after removal of desipramine from the medium and was not observed by direct addition of desipramine to the sialyltransferase incubation assay. Under the same conditions, W-7 [N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide], which is known to be a potent calmodulin antagonist and an inhibitor of calmodulin-dependent kinases, gave the same concentration-dependent inhibition profile of sialyltransferase as desipramine, whereas H-7 [1-(5-isoquinolinylsulfonyl)-2-methylpiperazine], which is an inhibitor of protein kinase C and cyclic nucleotide-dependent kinases, had no effect. So, it is suggested that desipramine inhibits the sialyltransferase activity in C6 glioma cells through a calmodulin-dependent system.
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PMID:Effect of desipramine on a glycoprotein sialyltransferase activity in C6 cultured glioma cells. 229 42

C6 glioma cells contain two types of receptors for adrenocorticoids. Glucocorticoid (Type II) receptors are present at higher density and mediate increases in glycerol phosphate dehydrogenase and glutamine synthetase activity. The function of mineralocorticoid (Type I) receptors present at low density in C6 cells is unknown. Since mineralocorticoid (Type I) receptors in renal epithelial cells regulate cation transport, we sought to determine whether adrenocorticoid receptors located in glioma cells are similarly linked to electrolyte transporting activity. Occupation of mineralocorticoid receptors in C6 glioma by adrenocorticoids did not alter Na+ or K+ transport, in contrast to their effects on renal epithelial and vascular smooth muscle cells. Occupation of glucocorticoid receptors produced a 20-25% decrease in K+ uptake into C6 cells, but did not alter Na+ influx. Stimulation of Na+ influx with the ionophore monensin produced a large ouabain-sensitive increase in glucose utilization, as measured by 2-deoxyglucose uptake. However, mineralocorticoid receptor occupation did not alter glucose utilization, providing further evidence that these receptors do not influence Na+ transport in C6 cells. These studies provide evidence that mineralocorticoid receptors in glioma cells do not regulate Na+ or K+ transport. Glial glucocorticoid receptors have an inhibitory effect on glial K+ influx, which may contribute to glucocorticoid hormone effects on brain excitability.
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PMID:Effect of adrenocorticoid receptors on potassium and sodium flux in rat C6 glioma cells. 282 17

The hormone-responsive enzymes tyrosine aminotransferase and glycerol-3-phosphate dehydrogenase were studied with respect to current models of the mechanism of glucocorticoid/cAMP interaction during the induction of enzyme activity in responsive cell hybrids between rat C6 glioma cells and rat FU5AH hepatoma cells. The results of experiments involving protein and mRNA synthesis inhibitors, sequential addition of inducers, and the assay of cyclic-AMP-dependent protein kinase could not be adequately explained by any one model of inducer interaction. Comparison of the hybrid clones revealed the presence of factors that may modify induction but that are not essential for synergistic induction.
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PMID:The synergistic interaction of hydrocortisone and dibutyryl cyclic AMP during enzyme induction in hybrids between rat C6 glioma cells and FU5AH hepatoma cells. 286 87

Utilizing a glycerol phosphate dehydrogenase cDNA clone from the rat glioma C6 cell line, we report that the glucocorticoid regulation of glycerol phosphate dehydrogenase gene expression in glial cells occurs at the transcriptional level. Furthermore, our transcription results in vitro, as well as Northern blot analysis, show that the short-chain fatty acid, sodium butyrate, totally blocks this hydrocortisone-induced transcription of glycerol phosphate dehydrogenase, demonstrating that the site of action of this fatty acid resides in the cell nucleus. The C6 glycerol phosphate dehydrogenase cDNA clone (pGPDH-1,1800 base pairs) used in these studies was selected from a C6 library generated from polysomal poly(A)+ RNA. pGPDH-1 hybridized to a 4.7-kilobase RNA from rat muscle and brain, mouse liver, and C6 cells; this mRNA is at least four times larger than the required coding sequence for glycerol phosphate dehydrogenase. Northern blot analysis of developing rat brain reveals a striking increase in glycerol phosphate dehydrogenase transcripts during the period most associated with peak myelination.
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PMID:Glucocorticoids regulate the transcription of glycerol phosphate dehydrogenase in cultured glial cells. 299 22

We have compared the effects of norepinephrine, forskolin, and dibutyryl cyclic AMP (Bt2cAMP) on the regulation of the cytosolic enzyme glycerol phosphate dehydrogenase (GPDH) in the C6 rat glioma cell line. Forskolin and Bt2cAMP elicit a dose-dependent increase in the levels of the enzyme that was, however, unaffected by norepinephrine. The half-maximal effect of forskolin was obtained at 7-8 microM, and the effect was maximal at 30 microM. Dexamethasone at a 50 nM concentration produced a two- to sixfold induction of GPDH after 48 h. The combination of dexamethasone with forskolin or Bt2cAMP leads to an elevation in GPDH levels that is higher than that produced by one of the compounds alone. This potentiation is found when both agents are added together with or after the glucocorticoid. The increase in uninduced and dexamethasone-induced GPDH activity was blocked by cycloheximide and actinomycin D, indicating that de novo protein and RNA synthesis are required. The activity of cytosolic lactate dehydrogenase activity did not change after incubation with dexamethasone, but increased with forskolin or Bt2cAMP.
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PMID:Regulation of glycerol phosphate dehydrogenase and lactate dehydrogenase activity by forskolin and dibutyryl cyclic AMP in the C6 glial cells. 302 Jan 71

We have shown that the second stage tumor promoters mezerein (MEZ) and phorbol 12-retinoate 13-acetate (PRA) inhibit the gluccocorticoid-induced increase in glycerol phosphate dehydrogenase (GPDH) activity in C6 rat glioma cells with ED 50-values of 3.9 and 2.9 nM, respectively. Phorbol 12-myristate 13-acetate (PMA) was 10-fold less potent. MEZ was likewise more potent than PMA for inhibition of cAMP formation in response to isoproterenol. Binding competition studies using [3H]phorbol 12,13-dibutyrate ([3H]PDBu) yielded apparent Ki-values for MEZ and PRA of 50-70 nM. The large difference between the biological potencies of MEZ and PRA and their affinity for the major phorbol ester receptor suggest they may be acting through a more complicated mechanism in these cells.
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PMID:Second stage tumor promoters: differences in biological potency and phorbol ester receptor affinity in C6 cells. 304 Feb 25

An oligodendroglial specific property, glucocorticoid regulation of glycerol-3-phosphate dehydrogenase (GPDH) levels, was inhibited in C6 rat glioma cells when 4 beta-phorbol 12-myristate 13-acetate (PMA) was added to the cultures. PMA inhibited GPDH induction in both logarithmic- and stationary-phase cells. These events are most likely mediated through the phorbol ester receptor since the ability of various phorbol ester analogs to compete with the ligand [3H]4 beta-phorbol 12,13-dibutyrate for binding to the receptor correlates with the ability the particular analog has to inhibit GPDH induction. Additionally, like tumor promotion in vivo, the inhibition of GPDH induction is reversible. The PMA effect is not restricted to the C6 cell line since PMA also inhibits GPDH inducibility in another rat glioma cell line. This PMA-mediated event has been partially characterized. PMA did not affect the overall rate of protein or RNA synthesis. It was ineffective in altering both glucocorticoid accumulation to the nucleus and the rate of GPDH degradation. It appears likely that PMA's inhibitory action occurs at the transcriptional or translational level.
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PMID:Glucocorticoid-mediated increases in glycerol phosphate dehydrogenase activity is inhibited by the phorbol ester tumor promoters. 386 70

Enzyme induction by hydrocortisone (HC) and dibutyryl cyclic AMP (dbcAMP) was studied in C6 rat glioma cells, FU5AH rat hepatoma cells, and five C6 x FU5AH hybrids. Hormone responsive enzymes from both parental lines were studied, including: tyrosine aminotransferase (TAT), alanine aminotransferase (AAT), glycerol phosphate dehydrogenase (GPDH), lactate dehydrogenase (LDH), and 2',3'-cyclic nucleotide 3'-phosphohydrolase (CNP). There was no overall dominance of one parental phenotype over the other in expression of uninduced or induced enzyme activity after fusion, and the hybrids possessed some enzymatic properties characteristic of both parents. GPDH was induced by dbcAMP in all five hybrids, and TAT was induced by dbcAMP in four of the hybrids, although neither of these enzymes were induced by dbcAMP in the parents. Furthermore, synergistic induction of these enzymes by HC and dbcAMP was observed in the hybrids but not in the parents. These hybrids provide a model system to study hormone interaction in enzyme induction.
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PMID:Synergistic enzyme induction by glucocorticoids and cyclic AMP observed in glioma x hepatoma cell hybrids but not in their parents. 614 8

To study the influence of cell surface-associated molecules on intercellular communication, C6 glioma cells were cultured both on plastic and on substrata of paraformaldehyde-fixed B104 neuroblastoma cells. By then comparing the phenotypic expression of these "cocultured" C6 cells with cells cultured on tissue culture plastic, the influence of the cellular substratum was determined. The beta-adrenergic-responsive cyclic AMP-generating system of C6 cells was compared on these various substrata. We found that fixed beds of dibutyryl cyclic AMP (dbcAMP)-treated B104 cells uncoupled beta-receptors from adenylate cyclase, whereas fixed beds of similarly treated C6 cells did not. However, other cellular properties were not affected by growth atop fixed dbcAMP-treated B104 cell beds including the rate of C6 cellular proliferation and their rate of protein synthesis. The cell surface-associated determinant on B104 cells capable of uncoupling the beta-responsive cyclase system of C6 cells is probably a protein, as judged by its susceptibility to protease treatment. Other properties of C6 cells were also affected by the various substrata including basal and hydrocortisone-induced levels of glycerol phosphate dehydrogenase (GPDH; an oligodendroglial marker) and the rate of RNA synthesis in these cells.
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PMID:Cell surface-mediated cellular interactions: effects of B104 neuroblastoma surface determinants on C6 glioma cellular properties. 629 40


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