SEARCH · PubMed Health

Results for “variable methylation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources

PubMed1992

Abnormalities of insulin-like growth factor (IGF-I and IGF-II) genes in human tumor tissue.

Recent findings have indicated that Insulin-like growth factors (IGF-I and IGF-II) may play a role in neoplasia. Expression of their genes, which are highly complex structures, is tissue-specific and developmentally regulated. The purpose of the present study was to determine whether a relationship exists between tumorigenesis and the structure and expression of IGF genes. The structures of the IGF-I and IGF-II genes were investigated in 40 tumors by Southern blot analysis but no obvious re-arrangements (such as amplification or deletion) were observed in any of the tissues investigated. DNA methylation was also studied, using the enzyme Avall. The extent of DNA methylation of the IGF genes was highly variable in most of the tumors, as was the level of mRNA expression. A relationship could be detected between IGF over-expression and gene demethylation in tumors associated with hypoglycemia and in certain hepatocarcinomas. Loss of heterozygosity has been reported in the 11p15 region of some childhood tumors. The present findings provide further evidence of this loss of heterozygosity for the IGF-II gene and show an imbalance in the leukocyte alleles in several childhood tumors. Likewise, an imbalance in the alleles was noted in several adult tumors, including hepatocarcinomas and breast cancers. This suggests that in certain adult tumors alterations of the IGF-II gene may be associated with tumorigenesis, but in other tumors another mechanism may be involved.

Alleles↗

PubMed2000

Methylation mosaicism of 5'-(CGG)(n)-3' repeats in fragile X, premutation and normal individuals.

Fragile X syndrome (FRAXA) is characterized at the molecular level by an expansion of a naturally occurring 5'-(CGG)(n)-3' repeat in the promoter and 5'-untranslated region (5'-UTR) of the fragile X mental retardation (FMR1) gene on human chromosome Xq27.3. When expanded, this region is usually hypermethylated. Inactivation of the FMR1 promoter and absence of the FMR1 protein are the likely cause of the syndrome. By using the bisulfite protocol of the genomic sequencing method, we have determined the methylation patterns in this region on single chromosomes of healthy individuals and of selected premutation carriers and FRAXA patients. In control experiments with unmethylated or M- Sss I-premethylated DNAs, this protocol has been ascertained to reliably detect all cytidines or 5-methylcytidines as unmethylated or methylated nucleotides, respectively. Analyses of the DNA from FRAXA patients reveal considerable variability in the lengths of the 5'-(CGG)(n)-3' repeats and in the levels of methylation in the repeat and the 5'-UTR. In one patient (OEl) with high repeat length hetero-geneity ( n = 15 to >200), shorter repeats (n = 20-80) were methylated or unmethylated, longer repeats ( n = 100-150) were often completely methylated, but one repeat with n = 160 proved to be completely unmethylated. This type of methylation mosaicism was observed in several FRAXA patients. In healthy females, methylated 5'-CG-3' sequences were found in some repeats and 5'-UTRs, as expected for the sequences from one of the X chromosomes. The natural FMR1 promoter is methylation sensitive, as demonstrated by the loss of activity in transfection experiments using the unmethylated or M- Sss I-premethylated FMR1 promoter fused to the luciferase gene as an activity indicator.

5' Untranslated Regions↗

PubMed2006

Derivatisation using m-(trifluoromethyl)phenyltrimethylammonium hydroxide of organic materials in artworks for analysis by gas chromatography-mass spectrometry: unusual reaction products with alcohols.

The quaternary ammonium reagent m-(trifluoromethyl)phenyltrimethylammonium hydroxide (TMTFTH) has gained widespread use for the derivatisation for GCMS analysis of organic materials found in artists' materials, such as oils, plant resins and waxes. This paper discusses products formed from reactions of TMTFTH with alcohols--including fatty alcohols, hydroxyacids, terpenes and glycerol--that have diagnostic value in the analysis of samples from artworks. In addition to methyl ethers, (trifluoromethyl)phenyl ethers were formed to variable degrees from the different types of alcohol. The products were identified from their EI mass spectra. An understanding of these multiple reaction products is important for the interpretation of GCMS data from complex samples, especially in the case of polyfunctional alcohols such as glycerol, which forms a number of methyl, (trifluoromethyl)phenyl and mixed ethers. The significance of the reaction products, and the relative advantages of TMTFTH as compared to alternative ammonium and sulfonium methylating reagents, are discussed.

Alcohols↗

PubMed1993

Structural characterization and expression analysis of the Neurospora conidiation gene con-6.

The gene con-6 of Neurospora crassa is expressed during the formation of asexual spores (conidia), but it is not expressed in mycelium. con-6 mRNA appears upon induction of conidiation and reaches high levels at the late stages of conidiation, and in mature conidia. The CON6 polypeptide and a CON6-beta-Gal fusion protein were present at high levels only in free conidia. Shortly after spore germination con-6 mRNA disappears and the CON6 polypeptide is degraded. CON6 is a small, hydrophilic polypeptide containing a repeat sequence; it not homologous to any known protein but has features resembling the late embryogenesis abundant proteins of maize. Inactivation of con-6 by the repeat-induced point mutation process had no demonstrable effect on formation or germination of conidia. Upstream sequence comparisons for con-6 and other con genes identified a common potential regulatory sequence, designated CRS-B. DNA mobility shift analyses with cell extracts identified a factor that bound to synthetic DNA fragments containing this sequence. This binding factor was present in mycelium but not in conidiating cultures. Experiments with independent integrated con-6'-'lacZ translational fusions revealed substantial variability of expression among transformants carrying identical fusion constructs: This variability may be due to the differential methylation of transformant DNA noted by others.

Amino Acid Sequence↗

PubMed2006

Optimisation of integrated biodiesel production. Part II: a study of the material balance.

A study was made of the material balance for the fatty acid methyl ester (biodiesel) synthesis from sunflower oil using potassium hydroxide as the catalyst. A factorial design of experiments and a central composite design have been used to evaluate the influence of operating conditions on the process material balance. The responses chosen were the biodiesel yield and the yield losses due to triglyceride saponification and methyl ester dissolution in glycerol, while the variables studied were temperature, initial catalyst concentration and the methanol:vegetable oil molar ratio. The biodiesel yield increased and therefore the yield losses decreased by decreasing catalyst concentration and temperature. However, the methanol:sunflower oil molar ratio did not affect the material balance variables significantly. Second-order models were obtained to predict the biodiesel yield and both yield losses. Within the experimental range studied, these models largely matched the results from the experiments.

Biotechnology↗

PubMed1977

Non-equilibrium method for the radioimmunoassay of clozapine in the presence of metabolites.

Cross-reactions with metabolites are an ever-recurring problem encountered in the use of radioimmunoassay techniques to determine active compounds in biological material. Metabolites may interfere with the assay of the parent drug to a variable extent. Taking 8-chloro-11-(4-methyl-1-piperazinyl)-5H-dibenzo[b,e][1,4]diazepine (clozapine as an example, it was shown that the extent to which the antiserum produced interacts with the parent drug and the metabolites can be estimated by determining the equilibrium constants and the kinetics. In the present case, therefore, it was advantageous to carry out the radioimmunoassay in disequilibrium, i.e. in order to differentiate the metabolites from the parent drug, the sample was incubated with the antiserum for 10 min, after which the labelled antigen was added and the reaction mixture again incubated for a brief, exactly timed interval. It was shown that cross-reactions did not occur in mixtures of clozapine and its N-demethyl and N-oxide metabolites in the propor tions 1:1:2 over a range of concentration of 1.5-48 ng clozapine per 100 microliter human plasma. The equilibrium constants measured with the clozapine goat antiserum were as follows: clozapine 1.2 X 10(8) M-1, the N-demethyl metabolite 4.6 X 10(7) M-1 and the N-oxide metabolite 3.7 X 10(7) M-1 (pH 7.5 and 20 degrees C).

Administration, Oral↗

PubMed1984

Comparison of sigma- and kappa-opiate receptor ligands as excitatory amino acid antagonists.

Using the technique of microelectrophoresis in pentobarbitone-anaesthetized cats and rats, the effects of benzomorphans, with known actions at sigma- and kappa- opioid receptors, were tested on responses of spinal neurones to amino acids and acetylcholine. The racemic mixture and both enantiomers of the sigma opiate receptor agonist, N-allylnormetazocine (SKF 10, 047), and the dissociative anaesthetic, ketamine, reduced or abolished excitation evoked by N-methyl-aspartate (NMA) with only small and variable effects on responses to quisqualate or kainate. (+)-SKF 10, 047 was 1.2 +/- 0.7 times more potent than the (-)-enantiomer in antagonizing NMA. On Renshaw cells, (+)-SKF 10, 047 enhanced responses to acetylcholine whereas the (-) enantiomer produced only a small reduction. The kappa- opiate receptor agonist, ethylketocyclazocine, had no selective effects on responses to amino acids or to acetylcholine. We conclude that actions at sigma- but not kappa-, opiate receptors are responsible for the NMA antagonism observed with benzomorphans.

Acetylcholine↗

PubMed2001

Methanol-induced optic neuropathy: treatment with intravenous high dose steroids.

The aim of this study was to find the potential benefit of intravenous high dose steroids in the treatment of patients with methanol optic neuropathy. Four patients complaining of diminution of vision after taking methylated spirit presented to us within a variable period of its consumption. The systemic features of methanol poisoning were absent in these patients. Raised blood levels of methanol confirmed the diagnosis of methanol optic neuropathy. All these patients received high doses of intravenous steroids for three days, followed by oral steroids, 1 mg/kg body weight, for 11 days. The administration of high doses of intravenous steroids led to an improvement of visual status in all four patients. Intravenous high dose steroids benefit the visual status of patients with methanol-induced optic neuropathy, provided the interval between the consumption of methanol and starting treatment is short. Further studies should be undertaken to document the role of intravenous steroids in this context.

Adult↗

PubMed2002

The gene for domains rearranged methyltransferase (DRM2) in Arabidopsis thaliana plants is methylated at both cytosine and adenine residues.

The methylation patterns of cytosine and adenine residues in the Arabidopsis thaliana gene for domains rearranged methyltransferase (DRM2) were studied in wild-type and several transgene plant lines containing antisense fragments of the cytosine DNA-methyltransferase gene METI under the control of copper-inducible promoters. It was shown that the promoter region of the DRM2 gene is mostly unmethylated at the internal cytosine residue in CCGG sites whereas the 3'-end proximal part of the gene coding region is highly methylated. The DRM2 gene was found to be also methylated at adenine residues in some GATC sequences. Cytosine methylation in CCGG sites and adenine methylation in GATC sites in the DRM2 gene are variable between wild-type and different transgenic plants. The induction of antisense METI constructs with copper ions in transgene plants in most cases leads to further alterations in the DRM2 gene methylation patterns.

Adenine↗

PubMed2002

Chronic alpha1-adrenergic blockade improves hypertension and renal injury in L-NAME and low-renin L-NAME-DOCA hypertensive rats.

BACKGROUND: The present study investigated the contribution of alpha1-adrenergic blockade to hypertension induced by long-term blockade of nitric oxide and chronic treatment with deoxycorticosterone acetate (DOCA), which produced a low renin model of hypertension. We studied the effects of chronic administration of prazosin, an alpha1-receptor antagonist, on blood pressure (BP), renal injury, and other variables in N(omega)-nitro-L-arginine methyl ester (L-NAME) and L-NAME+DOCA hypertensive rats. MATERIAL/METHODS: The rats were divided into 6 groups: Control, DOCA, L-NAME, L-NAME+DOCA, L-NAME+ prazosin, and L-NAME+DOCA+prazosin. Tail systolic BP was measured twice a week. After a 6-week evolution, mean arterial pressure (MAP) was measured, along with selected metabolic, morphological and renal variables. RESULTS: The final MAP values were 105+/-1 for Control, 107+/-0.6 for DOCA, 153+/-3 for L-NAME, 175+/-2 for L-NAME+DOCA, 126+/-2 for L-NAME+prazosin and 127+/-5 for L-NAME+DOCA+prazosin. Proteinuria and hyaline arteriopathy were prevented in L-NAME+prazosin rats and markedly attenuated in the L-NAME+DOCA+prazosin group. Plasma urea and creatinine were significantly increased in the L-NAME+DOCA group, but not in the L-NAME+ DOCA+prazosin group as against controls. The DOCA and DOCA+L-NAME groups showed relative renal and cardiac hypertrophy, which was not observed in the DOCA+L-NAME+prazosin group. CONCLUSIONS: Alpha1-adrenergic tone plays an important role in the increased BP and renal injury of L-NAME hypertension. Our results also indicate that when PRA is suppressed by DOCA in L-NAME hypertension, the increased BP and renal injury are largely dependent on the alpha1-adrenergic tone.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed2005

Consistent transcriptional silencing of 35S-driven transgenes in gentian.

In this study, no transgenic gentian (Gentiana triflora x Gentiana scabra) plants produced via Agrobacterium-mediated transformation exhibited transgene (GtMADS, gentian-derived MADS-box genes or sGFP, green fluorescent protein) expression in their leaf tissues, despite the use of constitutive Cauliflower mosaic virus (CaMV) 35S promoter. Strikingly, no expression of the selectable marker gene (bar) used for bialaphos selection was observed. To investigate the possible cause of this drastic transgene silencing, methylation-specific sequences were analysed by bisulfite genomic sequencing using tobacco transformants as a control. Highly methylated cytosine residues of CpG and CpWpG (W contains A or T) sites were distinctively detected in the promoter and 5' coding regions of the transgenes 35S-bar and 35S-GtMADS in all gentian lines analysed. These lines also exhibited various degrees of cytosine methylation in asymmetrical sequences. The methylation frequencies in the other transgene, nopaline synthase (NOS) promoter-driven nptII, and the endogenous GtMADS gene coding region, were much lower and were variable compared with those in the 35S promoter regions. Transgene methylation was observed in the bialaphos-selected transgenic calluses expressing the transgenes, and methylation sequences were distributed preferentially around the as-1 element in the 35S promoter. Calluses derived from leaf tissues of silenced transgenic gentian also exhibited transgene suppression, but expression was recovered by treatment with the methylation inhibitor 5-aza-2'-deoxycytidine (aza-dC). These results indicated that cytosine methylation occurs exclusively in the 35S promoter regions of the expressed transgenes during selection of gentian transformants, causing transcriptional gene silencing.

Base Sequence↗

PubMed1994

Stereoselective differences in the binding of N-methylated barbiturates to human serum albumin.

The binding to human serum albumin (HSA) of a homologous series of N-methylated chiral barbiturates was studied by means of equilibrium dialysis. The length of the aliphatic side chain at C-5 of the barbiturate ring was variable, and the compounds used were: (+)-(S)- and (-)-(R)-5-methyl-(A), -5-ethyl-(B), -5-propyl-(C) and -5-butyl-(D)-1-methyl-5-phenyl-barbiturate. Binding parameters (numbers of binding classes and of binding sites in each class, affinity constant, total binding constant) were obtained from the Scatchard plot of the percent binding values. For both enantiomers of A and D as well as for (-)-(R)-B 2 classes were obtained; (+)-(S)-B and both enantiomers of C had only 1 class. The total binding constant (K) indicated a more than twofold higher binding of (-)-(R)-B (2.64 x 10(3).mol-1) and C (5.75 x 10(3).mol-1) compared with the corresponding (+)-(S)-enantiomer (1.02 and 2.00 x 10(3).mol-1, respectively); in the case of D the (+)-(S)-enantiomer was preferentially bound (K = 10.14 vs. 5.40 x 10(3).mol-1 for the (-)-(R)-enantiomer). The percent binding values of (+)-(S)-A were higher than those of (-)-(R)-A; however, the K-values of the A-enantiomers were almost identical.

Barbiturates↗

PubMed2003

Effects of omapatrilat on blood pressure and renal injury in L-NAME and L-NAME plus DOCA-treated rats.

BACKGROUND: This study investigates the effects of chronic administration of omapatrilat (OMA) on blood pressure (BP), renal injury, and other variables in N(omega)-nitro-L-arginine methyl ester (L-NAME) hypertension and in the low-renin model produced by the simultaneous administration of L-NAME and deoxycorticosterone acetate (DOCA). METHODS: The control, DOCA, L-NAME, L-NAME + DOCA, L-NAME + OMA, and L-NAME + DOCA + OMA groups were used. Tail systolic BP was measured twice a week. After 4 weeks of treatment, mean arterial pressure (MAP), and metabolic, morphologic, and renal variables were measured. RESULTS: The final values of MAP were 109 +/- 5.1 mm Hg for the control group, 113 +/- 3.0 mm Hg for DOCA, 175 +/- 3.7 mm Hg for L-NAME, 193 +/- 3.8 mm Hg for L-NAME + DOCA, 117 +/- 3.9 mm Hg for L-NAME + OMA, and 158 +/- 3.0 mm Hg for L-NAME + DOCA + OMA. The rats treated with L-NAME showed mild and scarce renal lesions, which were prevented by OMA treatment and the L-NAME + DOCA group showed proteinuria and hyaline arteriopathy, which were markedly attenuated in the L-NAME + DOCA + OMA group. Plasma urea and creatinine were significantly increased in the L-NAME + DOCA group, whereas these variables were not significantly greater in the L-NAME + DOCA + OMA group versus controls. The L-NAME + DOCA group showed relative renal and cardiac hypertrophy that was not observed in the L-NAME + DOCA + OMA group. CONCLUSIONS: The simultaneous blockade of neutral endopeptidase (NEP) and angiotensin converting enzyme (ACE) completely prevents L-NAME hypertension. Our results also show that OMA attenuates the increased BP and the renal injury in L-NAME hypertensive rats treated with DOCA. Assuming that this is a low-renin model of hypertension, the protective effect of OMA may be due to an increase in vasodilator peptides produced by both ACE and NEP inhibition.

Animals↗

PubMed2002

Competitive interaction of the OxyR DNA-binding protein and the Dam methylase at the antigen 43 gene regulatory region in Escherichia coli.

The antigen 43 surface protein of Escherichia coli is expressed in a phase-variable manner by a mechanism involving alternative activation and repression of transcription of the agn43 gene. The repressor is the OxyR DNA-binding protein, and its binding site was found to be located downstream of the agn43 transcription start site in a region of DNA that encompasses three 5'-GATC-3' sequences that are subject to Dam-mediated DNA methylation. It has been suggested previously that the phase-variable expression of antigen 43 results from a competition between Dam methylase and the OxyR repressor for these sites. The 5'-GATC-3' sequences were inactivated for methylation by site-directed mutagenesis, and all possible combinations of inactive and active sites were assessed for effects on phase-variable expression of the agn43 gene. Inactivation of any 5'-GATC-3' site individually had no effect; at least two sites had to be inactivated to disrupt the normal pattern of expression. Studies of OxyR interaction with agn43 DNA showed that methylation of any two 5'-GATC-3' sites was necessary and sufficient to block binding of the repressor. It was also found that the adenines of the second and third 5'-GATC-3' sites are required for OxyR binding, demonstrating that the sites for Dam methylation and for repressor binding are intimately associated. This is consistent with a competition model in which Dam and OxyR share a preference for specific DNA sequences in the regulatory region of the agn43 gene.

Adhesins, Bacterial↗

PubMed2004

Promoter methylation and protein expression of the E-cadherin gene in the clinicopathologic assessment of adenoid cystic carcinoma.

Adenoid cystic carcinoma, a relatively uncommon tumor of salivary glands, is characterized by a prolonged clinical course and a fatal outcome. The molecular events underlying their progression are unknown. In this study, we examined the methylation status of E-cadherin gene and its protein expression in 23 cases of adenoid cystic carcinoma and correlated the results with the clinicopathologic factors to determine its role in these tumors. We also analyzed the effect of 5-azacytidine on the re-expression in a methylated cell line of adenoid cystic carcinoma for this gene. In our study, E-cadherin immunoreactivity, although heterogeneous, showed a progressive reduction with high histological grade and in metastatic and recurrent lesions. Promoter methylation was detected in 16 of 23 cases (70%), but there was no correlation with the histological grade or patient prognosis. Microdissection of immuno-negative cells in heterogeneous tumors showed positive methlyation. In the cell line from salivary adenoid cystic carcinoma with methylated E-cadherin, 5-azacytidine restored the E-cadherin expression. Our results indicate that: (1) E-cadherin gene promoter is frequently methylated in adenoid cystic carcinoma, leading to reduced E-cadherin expression, (2) variable E-cadherin expression might result from the intratumoral heterogeneity, and (3) increased extent of methylated areas may be associated with progression and advancement of the disease.

Adult↗

PubMed1985

The effects of some beta lactam antibiotics on (3H)-methyl-yohimbine binding to intact human platelets.

Several antibiotics have been reported to cause a bleeding diathesis in man, characterized by reduced platelet aggregation. We investigated the effects of several of the penicillins and of moxalactam on the binding of (3H)-methyl-yohimbine to intact human platelets. The (3H)-methyl-yohimbine binding met the criteria for interaction at an alpha2 adrenergic binding site and showed low interindividual variability. Penicillin G, ticarcillin, carbenicillin, piperacillin and moxalactam all inhibited (3H)-methyl-yohimbine binding, but at concentrations far in excess of clinically achievable plasma levels. We conclude that these compounds exert their antiplatelet effects by a mechanism other than competitive inhibition of catecholamine binding.

Adrenergic alpha-Antagonists↗

PubMed1997

DNA hypomethylation in breast cancer: an independent parameter of tumor progression?

The global DNA methylation status was investigated on a series of 59 breast cancers by Southern blotting, using methylation sensitive restriction enzymes. By comparison to control DNA, almost all tumor DNAs were found globally hypomethylated. However, the demethylation was variable from tumor to tumor. Compared to other biological parameters, the methylation did not correlate with chromosome alterations, steroid hormone receptor status, or histopathological grading. Tumors which appeared to be the most evolved for other parameters were only mildly hypomethylated, whereas tumors with strongly hypomethylated DNA corresponded to those with slight alterations of the other parameters. Thus, DNA hypomethylation is a consistent characteristic of breast cancer, but its variations may not correlate with tumor progression of most breast cancers.

Age Factors↗

PubMed1984

Antiadrenergic antihypertensive drugs: their effect on renal function.

Peripheral alpha antagonists not only preserve renal hemodynamics, but decrease RVR and maintain renal perfusion autoregulation in the face of decreased systemic perfusion pressures. On the other hand, central alpha agonists appear to have variable effects. Clonidine preserves RBF and GFR both acutely and chronically, guanabenz decreases RBF acutely but not chronically, and alpha-methyl dopa preserved RBF but decreases GFR. Beta blockers also have variable effects on RBF: the most-often-studied beta blocker, propranolol, has reduced RBF by 10-20% while other commonly used beta blockers, such as nadolol and metoprolol, may preserve RBF. This may reflect propranolol's inability to maintain renal perfusion autoregulation in the face of decreased systemic blood pressure. This failure of propranolol is not completely understood but may be a function of its lack of cardioselectivity or ISA (49). It is also possible that inhibition of renal vasodilators such as the kallikrein-kinin system plays a role (49). Finally, it appears that patients with normal renal vascular tone may be at highest risk to suffer decrements in RBF with beta blockers. Perhaps most importantly, the clinical impact of propranolol's effect on renal function is unclear, since the reductions in GFR have not been sufficient to produce azotemia.

Administration, Oral↗