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)

Previous reports have provided conflicting evidence as to whether the response to TRH desensitizes. Here we show that TRH stimulation of phosphoinositide (PPI) hydrolysis, measured as inositol phosphate accumulation in the presence of LiCl, desensitizes in rat pituitary GH3 cells and in rat glioma C6 cells stably transfected with mouse pituitary TRH receptor complementary DNA. In GH3 cells, the rate of stimulation by 1000 nM TRH of PPI hydrolysis was maximal initially and then decreased by 44 +/- 13% after 20 min. In an experimental paradigm in which PPI hydrolysis was measured by adding 20 mM LiCl at different times after TRH, desensitizations caused by 3, 10, and 1000 nM TRH were 33 +/- 5%, 41 +/- 6%, and 69 +/- 2%, respectively. In transfected C6 cells, TRH-induced desensitization of 76 +/- 9% was found. In GH3 cells, 1 microM phorbol myristate acetate (PMA), an activator of protein kinase C, inhibited the initial response to TRH by 75 +/- 6% and preexposure to PMA and TRH decreased the rate of PPI hydrolysis by 98 +/- 1% after 60 min. One hundred micromolar H-7 (1-(5-isoquinolinesulfonyl)-2-methyl piperazine), an inhibitor of protein kinases, abolished the effect of PMA but did not inhibit TRH-induced desensitization. Elevation of cytoplasmic free Ca2+ by K+ depolarization increased TRH stimulation of PPI hydrolysis. We conclude that TRH stimulation of PPI hydrolysis acutely desensitizes and that this effect is not specific to pituitary cells. TRH-induced desensitization, moreover, does not appear to be mediated by protein kinase C or by elevation of cytoplasmic free Ca2+.
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PMID:Thyrotropin-releasing hormone stimulation of phosphoinositide hydrolysis desensitizes. Evidence against mediation by protein kinase C or calcium. 165 82

C6 glioma cells in culture were treated with 1 mM dibutyryl cyclic AMP (Db-cAMP) for 5, 8, 24 and 72 h. The cells were labelled with [3H]-thymidine before either the end, or the beginning, of the Db-cAMP treatment. The cell cycle passage was monitored by the simultaneous determination of DNA content and DNA synthesis in propidium iodide stained autoradiograms. The data revealed an early (t less than or equal to 3-8 h) and moderate inhibitory effect of Db-cAMP on all phases of the cell cycle except mitosis; some cells (2%) were completely blocked in the S phase. Later (8 less than t less than 24-72 h), the cycling of a substantial part of the population became inhibited in G1 phase. Microdensitometric texture analysis of Feulgen-stained nuclei, performed 24 h after administration of Db-cAMP, showed a higher inhomogeneity of the DNA distribution in cell nuclei, caused by the condensation of a part of the chromatin. This may reflect either changes in genome expression taking part in the process of cAMP induced differentiation or transit of some cells into quiescent G0 or S0 phases.
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PMID:Changes in cell cycle and chromatin distribution in C6 glioma cells treated by dibutyryl cyclic AMP. 166 44

LD78 is a member of a newly identified superfamily of small inducible proteins involved in inflammatory responses, wound healing, and tumorigenesis. Southern blot analysis of the EcoRI-digested human genomic DNAs, using previously isolated LD78 cDNA as a probe, showed that in each individual there are 4.2- and 4.8-kilobase-pair (kb) fragments and that some have an additional 6.5-kb fragment. The 4.2-kb fragment contained genomic DNA sequences corresponding to the LD78 cDNA and was named the LD78 alpha gene. The 4.8-kb fragment contained similar sequences, showing 94% homology to the LD78 alpha gene, and was named the LD78 beta gene. The LD78 alpha gene was present in a single or a few copies per haploid genome, whereas the copy number of the LD78 beta gene and of the 6.5-kb fragment hybridizable to LD78 cDNA varied among the samples tested. Treatment of human myeloid cell lines HL-60 and U937 with phorbol 12-myristate 13-acetate (PMA) increased within 2 h cellular levels of the RNA hybridizable to LD78 cDNA. The human glioma cell line U105MG and primary culture of human fibroblasts also expressed the hybridizable RNA in response to PMA. Addition of cycloheximide had no apparent effect on this response in U937 cells and inhibited the response in fibroblasts, whereas it stimulated the response in HL-60 and U105MG cells. mRNA phenotyping experiments revealed that the LD78 alpha and LD78 beta genes were both transcribed in PMA-stimulated U937 cells.
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PMID:Structures of human genes coding for cytokine LD78 and their expression. 169 14

DNA methylation at HpaII (CmCGG) sites inhibits expression of a human proenkephalin-CAT fusion gene when it is transiently expressed in CV-1 cells or stably expressed in C6-glioma cells. The inhibitory effects of HpaII methylation have been mapped to a site within the human proenkephalin promoter located at position -72 relative to the start site of transcription. This region spans a cAMP and phorbol ester inducible enhancer and methylation at this position inhibits both basal transcription and transcription induced by either cAMP or TPA. The HpaII site is located within an element which binds the transcription factor AP-2. In vitro methylation at this HpaII site inhibits the binding of AP-2. These results suggest that CpG methylation inhibits proenkephalin gene expression by directly interfering with the binding of a positively acting transcription factor previously shown to be essential for maximal basal, cAMP, and TPA inducible transcription.
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PMID:CpG methylation inhibits proenkephalin gene expression and binding of the transcription factor AP-2. 169 33

Using DAPI-DNA cytofluorometry, the author analyzed nuclear DNA content of formalin fixed, paraffin embedded, glioma material obtained from 14 glioma cases at surgery. Sections of 10 microns were deparaffinized. Following simultaneous DAPI (4,6-diamidino-2-phenylindole dihydroporphyrin chloride)/HP (hematoporphyrin) staining, DAPI binds DNA and DNA-DAPI complexes emit blue fluorescence when exited by ultraviolet (UV) light. Through Zeiss fluorescence microscope, the author measured nuclear fluorescence intensity with histological verification of glioma cells. A DNA histogram was obtained with fluorescence intensity recorded on the abscissa and number of cells plotted on the ordinate. Samples of 20 normal non-neoplastic astrocytes taken from apparently normal brain tissue included in the histological slide were used as diploid (2 C) control. Based on DNA content, tumor cells were classified into 4 groups: N-group composed of cells with 2 C DNA content (normoploid), S-group with less than 2 C (hypoploid), L-group more than 4 C (hypertetraploid), I-group between 2 C and 4 C (intermediate ploidy). Intermediate ploidy was significantly higher and normoploid was significantly lower in glioblastoma compared with those of benign astrocytoma. Thus, DNA content and histological malignancy were well correlated. Due to limitation of measuring diaphragm of turret in the microscope, some extra large cell could not be included in it and was excluded from the measurement.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[DAPI-DNA cytofluorometric study of glioma cells--application of DAPI-DNA cytofluorometry to paraffin embedded archival glioma tissue for nuclear DNA content analysis]. 169 81

The muscarinic acetylcholine receptor (mAChR) is an integral membrane protein that transduces stimulus to effectors through the activation of guanine nucleotide-binding (G) proteins. Four or more subtypes of mAChR were detected in various tissues, and their primary structures were elucidated by cloning and sequence analysis of complementary DNA. Functional differences between them existed when they were expressed in clonal culture cells. mAChRI (m1) and mAChRIII (m3) preferentially activated phosphoinositide (PI) hydrolysis and opened Ca(2+)-activated K+ channels followed by closure of the M (K+)-currents, while such current activities were rarely evoked by mAChRII (m2)- and mAChRIV (m4)-transformed cells. Although it has been reported that mAChRII and mAChRIV inhibited adenylate cyclase, there was little or no such inhibition by mAChRI and mAChRIII. It is known that heart and neuronal mAChR modulate voltage-sensitive Ca2+ currents, but which species of mAChR subtypes are involved has been poorly understood. Recently we identified that endogenous mAChRIV and exogenous mAChRII expressed in NG108-15 neuroblastoma-glioma hybrid cells, but not mAChRI and mAChRIII, efficiently depressed high-threshold Ca2+ currents in a pertussis toxin-sensitive manner.
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PMID:[Coupling of muscarinic acetylcholine receptors, m1/m3 and m2/m4, to phosphoinositide metabolism and Ca2+ channels in DNA-transfected NG108-15 cells]. 172 Jul 57

Genome exposure studies were carried out on malignant CHO-K1 and C6 rat glioma cells and their respective, phenotypically normal counterparts (reverse-transformed CHO-K1, and both reverse-transformed C6 glioma and normal rat fibroblasts). Cells were subjected to the nick-translation technique previously developed to make visible the exposed (i.e., DNase I-sensitive) nuclear DNA, and examined by both epifluorescence and confocal microscopy. The confocal microscopy, by permitting examination of sections throughout the nucleus, made possible clearer identification of the regions of exposed and sequestered DNA in the cells studied. A peripheral shell of exposed DNA with some discontinuities was displayed in the great majority of the cells with normal phenotype, but in none of the cancer cells. Both types of cells displayed regions of exposed DNA in the nuclear interior, particularly surrounding the nucleoli. In accordance with previous theoretical proposals we postulate: the peripheral nuclear shell of exposed DNA contains differentiation-specific genes that include the specific growth-control genes and that are functional in normal cells but not in cancer; the exposed genes surrounding the nucleoli may represent housekeeping genes active in both normal and cancer cells; and the DNase I-resistant DNA in the interior of the nucleus we postulate to consist for the most part of genes specific to alternative differentiation states and to be sequestered and inactive. Previous differences in evaluation of roles of peripheral and internal DNA sensitivity to DNAse I hydrolysis appear to be reconciled by this formulation. Identification of exposed DNA may be useful in cancer diagnosis.
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PMID:Confocal microscopy of genome exposure in normal, cancer, and reverse-transformed cells. 172 54

Iododeoxyuridine is a halogenated pyrimidine and non-hypoxic cell radiosensitizer currently being used in clinical trials. The amount of radiosensitization by IdUrd is related to the amount of incorporation of the drug into a cell's DNA. These experiments were carried out in three human tumor cell lines (lung, glioma, and melanoma) in monolayer culture exposed to concentrations of IdUrd from 0.1-10 microM for one and three cell cycles before irradiation to determine incorporation and sensitization as a function of drug exposure. Except for the lung cell line, which required greater than 1 microM IdUrd, these cells demonstrate radiosensitization when exposed to 0.1 microM or greater of IdUrd. Maximum sensitization occurred at 10 microM IdUrd for all the cell lines at three cell cycles. The percent thymidine replacement by IdUrd increased with increasing concentrations, but was cell line dependent. Maximum percent replacement occurred at 10 microM at three cell cycles for all the cell lines: lung = 22.4%, glioma = 32.0%, and melanoma = 39.1%. The relationships between percent thymidine replacement and sensitization are not identical across these human tumor cell lines. If IdUrd is going to be a successful radiosensitizer in clinical trials, sustained plasma levels of 10 microM or greater for at least three cell cycles should be achieved during irradiation. This may be best accomplished with repeated short exposures to IdUrd (three cell cycles or approximately 4 days in these cell lines) every 1-2 weeks during radiation. Measurements of thymidine replacement in a tumor biopsy should be attempted prior to radiation to develop a predictive assay for radiosensitization.
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PMID:Iododeoxyuridine incorporation and radiosensitization in three human tumor cell lines. 173 85

We have previously shown that O6-benzylguanine can be used to deplete cells of the DNA repair protein O6-alkylguanine-DNA alkyltransferase and to enhance the sensitivity of human glioma (SF767) and colon tumor (HT29) cells to the cytotoxic effects of alkylnitrosoureas. In the present study, the combination of O6-benzylguanine and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) was evaluated in vitro to determine the number of DNA interstrand cross-links formed and in vivo to compare the therapeutic index with that of BCNU alone. The number of DNA interstrand cross-links, as measured by alkaline elution, was increased in HT29 cells treated with 10 microM O6-benzylguanine for 2 h prior to BCNU exposure compared to cells treated with BCNU only. The number of single strand breaks was not increased by prior exposure to O6-benzylguanine. To evaluate the therapeutic index, HT29 and SF767 cells were grown as xenografts in nude mice and the tumor growth rate after treatment with BCNU alone was compared with the rate after treatment with O6-benzylguanine and BCNU. Treatment was administered i.p. when tumors reached 100-200 mm3. For animals bearing HT29 xenografts that were treated with 60 mg/kg O6-benzylguanine 1 h prior to 20 mg/kg BCNU, the average time for tumor volume to increase by 200% was 25 days, compared to 10 days for animals treated with 20 mg/kg BCNU alone. For animals bearing SF767 xenografts, the tumor growth of controls was not significantly different from that of animals treated with O6-benzylguanine alone or BCNU alone up to the maximally tolerated dose (50 mg/kg). For these 3 groups, the average time for tumors to reach 300 mm3 was 9-12 days. However, when animals were treated with 80 mg/kg O6-benzylguanine 1 h prior to receiving 20 mg/kg BCNU tumor size did not increase for at least 21 days. Our studies demonstrate that the therapeutic index of BCNU can be increased when given in combination with O6-benzylguanine.
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PMID:Effect of O6-benzylguanine on the sensitivity of human tumor xenografts to 1,3-bis(2-chloroethyl)-1-nitrosourea and on DNA interstrand cross-link formation. 173 76

Expression of major heat shock and stress-induced protein, HSP70, is known to be under complex regulation in tumor cells. In this study, we investigated the alternations of cytokinetics and HSP70 expression by hyperthermia in the in vitro experimental systems, using two rat glioma cell lines, two human glioblastoma cell lines and rat glioblast cells. For hyperthermal treatment the flasks were placed in water baths warmed up at 41 -45 degrees C for 15 min. To determine the effect of hyperthermia on the cell cycle progression, the changes in the DNA distribution of the cell population were studied by flow cytometry (FCM). The levels of HSP70 protein were determined by immunoblot analysis. The relationship between cell cycle and HSP70 expression was investigated by FCM using PI and FITC-labelled HSP70 double staining technique. These results were as follows: 1) Compared with the control, hyperthermic treatment at 42 degrees C or 44 degrees C caused both 354A and T98G cells to accumulate in S phase 18 hours after treatment and G2/M phase after 6-18 hours. 2) Hyperthermic treatment at 42 degrees C caused C6 cells to accumulate in S phase 6 hours after treatment, whereas heat treatment at 44 degrees C caused C6 cells to accumulate in S phase after 18 hours and G2/M phase after 6 hours. 3) A172 cells were accumulated only in G2/M phase by hyperthermia. 4) Glioblast cells did not show the alterations of cytokinetics by heat treatment remarkably. 5) HSP70 protein synthesis were enhanced under hyperthermic conditions in all type of cells, whether primary glioblast or permanent glioma cell lines.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Alterations in cytokinetics and heat shock protein (70 kDa) expression of glial cell by hyperthermia]. 174 92


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