Occurrence Of Methylation Research Articles

Mercury isotopic evidence for the importance of particles as a source of mercury to marine organisms.

The origin of methylmercury in pelagic fish remains unclear, with many unanswered questions regarding the production and degradation of this neurotoxin in the water column. We used mercury (Hg) stable isotope ratios of marine particles and biota to elucidate the cycling of methylmercury prior to incorporation into the marine food web. The Hg isotopic composition of particles, zooplankton, and fish reveals preferential methylation of Hg within small (< 53 µm) marine particles in the upper 400 m of the North Pacific Ocean. Mass-dependent Hg isotope ratios (δ202Hg) recorded in small particles overlap with previously estimated δ202Hg values for methylmercury sources to Pacific and Atlantic Ocean food webs. Particulate compound specific isotope analysis of amino acids (CSIA-AA) yield δ15N values that indicate more-significant microbial decomposition in small particles compared to larger particles. CSIA-AA and Hg isotope data also suggest that large particles (> 53 µm) collected in the equatorial ocean are distinct from small particles and resemble fecal pellets. Additional evidence for Hg methylation within small particles is provided by a statistical mixing model of even mass-independent (Δ200Hg and Δ204Hg) isotope values, which demonstrates that Hg within near-surface marine organisms (0-150 m) originates from a combination of rainfall and marine particles. In contrast, in meso- and upper bathypelagic organisms (200-1,400 m), the majority of Hg originates from marine particles with little input from wet deposition. The occurrence of methylation within marine particles is supported further by a correlation between Δ200Hg and Δ199Hg values, demonstrating greater overlap in the Hg isotopic composition of marine organisms with marine particles than with total gaseous Hg or wet deposition.

Methylation and Polymorphism in CDH1 Gene Promoter Among Patients with Diffuse Gastric Cancer.

Background:The promoter methylation and single nucleotide polymorphisms (SNPs) affect the transcription activity of cancer-related genes in several cancers including diffuse gastric cancer (DGC). Here we aimed to evaluate the promoter methylation status and the rs16260 at the promoter region of the CDH1 gene in DGC.Methods:This case-control study was performed of 48 formalin-fixed paraffin-embedded (FFPE) blocks of DGC patients and 41 fresh frozen tissue samples of healthy individuals. Methylation status was evaluated using methylation-specific polymerase chain reaction (PCR) and the rs16260 at the promoter region of the CDH1 gene was assessed using PCR and sequencing method.Results:The occurrence of methylation at the promoter region of the CDH1 gene in DGC patients was significantly higher than control samples (P < 0.0001). The methylated status was significantly associated with the poor differentiated histological type of DGC (P = 0.0428). The frequency of AC genotype and the A allele in DGC patients was significantly higher than the control subjects (P = 0.006 and 0.003, respectively).Conclusions:Here we showed that methylation at the CDH1 promoter may contribute to the DGC development, and also the AC genotype was associated with the risk of DGC.

Cyanide Contamination of the Puyango-Tumbes River Caused by Artisanal Gold Mining in Portovelo-Zaruma, Ecuador.

To examine cyanide (CN-) contamination of a large river in southeastern Ecuador that has been severely impacted by the indiscriminate discharge of untreated gold processing effluents. Poor environmental stewardship of cyanide (CN-) use by 87 gold processing centers in Portovelo-Zaruma in southern Ecuador to leach residual gold from Hg-contaminated tailings has resulted in high CN- contamination of the Puyango-Tumbes River downstream from the centers. Free CN- concentrations were high in river surface waters for 50km below the processing plants, with the highest concentration 9088 times above the CCME standard of 5μg/L and 1136 times above the 24-h LC50 concentration of 40μg/L free CN- for some fish species. Due to cyanidation of mercury-contaminated tailings, the formation of Hg-CN complexes is a grave concern, as these complexes have been shown to be highly bioavailable. Preliminary tests conducted in a laboratory using bioassays with Danio rerio sp. and varying concentrations of synthetic Hg(CN)2 salt have shown significant THg bioaccumulation in muscle and kidney fish tissues exposed to concentrations >0.12mg/L. Furthermore, low MeHg results in fish tissues demonstrated little occurrence of methylation and that the bulk of the total mercury content was in the form of inorganic mercury. Although construction of a communal tailings facility (CTF) in Portovelo is a positive development to reduce riverine pollution, the requirement to truck tailings up to the CTF likely results in inadequate compliance of environmental regulations that are poorly enforced.

Epigenetic Silencing of DAPK1and p16 INK4a Genes by CpG Island Hypermethylation in Epithelial Ovarian Cancer Patients.

Transcriptional silencing induced by hypermethylation of CpG islands in the promoter regions of genes is believed to be an important mechanism of carcinogenesis in human cancers including epithelial ovarian cancer (EOC). Previously published data on gene methylation of EOC focused mainly on single gene or on cancer tissues. Objectives of the study were to estimate the promoter hypermethylation status of DAPK1 and p16 INK4a genes in circulating blood of EOC patients and to determine their association with clinicopathological features of EOC. This case-control study included 50 EOC patients and 20 apparently healthy and age matched female controls. Isolation of genomic DNA was carried out from peripheral venous blood. Methylation in promoter region of DAPK1 and p16 INK4a genes was determined by methylation-specific PCR. Methylation of DAPK1 was occurred in 42 out of 50 cases (84.0%) and methylation of p16 INK4a gene was occurred in 34 out of 50 cases (68.0%). Methylation of both genes was occurred in 25 cases (50.0%). Occurrence of methylation in DAPK1 and p16 INK4a genes was statistically significant (p < 0.0001) in cases compared to controls. Methylation of both genes was not statistically associated with age at diagnosis, menopausal status, histopathological types and FIGO staging of EOC. Identification of the peculiar promoter hypermethylation of DAPK1 and p16 INK4a genes might be a successful approach for ancillary diagnosis of EOC at early stage in blood sample.

The occurrence of methyl, ethyl, propyl, and butyl parabens in the urban rivers and stormwaters of Sydney, Australia

Solid-phase microextraction and gas chromatography-mass spectrometry (SPME-GC/MS) identified ethyl-paraben in Sydney's urban streams at greater concentrations than other parabens. Results were comparatively higher than studies from cities with combined sewer/stormwater systems.

Association analysis of toluene exposure time with high-throughput mRNA expressions and methylation patterns using in vivo samples

The emission of volatile organic compounds (VOCs) resulting from outdoor air pollution can contribute to major public health problems. However, there has been limited research on the health effects in humans from the inhalation of VOCs. Therefore, this study conducted an in vivo analysis of the effects of toluene, one of the most commonly used chemicals in many industries, on gene expression and methylation over time using the high-throughput technique of microarray analysis. We separated participants into three groups (control, short-term exposure, and long-term exposure) to investigate the influence of toluene exposure time on gene expression. We then comprehensively analyzed and investigated the correlation between variations in gene expression and the occurrence of methylation. Twenty-six genes were upregulated and hypomethylated, while 32 genes were downregulated and hypermethylated. The pathways of these genes were confirmed to be associated with cell survival and the immune system. Based on our findings, these genes can help predict the effects of time-dependent exposure to toluene on human health. Thus, observations from our data may have implications for the identification of biomarkers of toluene exposure.

Methylation frequencies of cell-cycle associated genes in epithelial odontogenic tumours

Objective The benign epithelial odontogenic tumours constitute a group of lesions derived from epithelial elements of the tooth-forming apparatus. This group includes lesions of different biological behaviour, such as ameloblastoma, calcifying cystic odontogenic tumour (CCOT) and adenomatoid odontogenic tumour (AOT). The pathogenesis of these neoplasms remains uncertain and the occurrence of methylation in cell-cycle related genes may be involved in their development. The aim of this study was to investigate the methylation status of P16, P21, P27, P53 and RB1 genes in epithelial odontogenic tumours. Design Methylation-specific polymerase chain reaction (MSP) was used to evaluate the presence of methylation in 13 samples of ameloblastoma, six samples of CCOT, three samples of AOT and 14 samples of dental follicles, included as control. Results Our results showed a distinct methylation profile in each group. In ameloblastoma, the highest methylated genes were P16 and P21, while in CCOT the P 21 and RB1 genes were the most commonly methylated genes . Only the P16 and P21 genes were methylated in the AOT samples. In the dental follicle samples, P16, P27 and RB1 genes were commonly methylated. A high percentage of the odontogenic tumours analysed showed methylation of the P21 gene, in contrast to dental follicles. Conclusions Epithelial odontogenic tumours show a distinct methylation profile in cell-cycle associated genes. In addition to this, the current findings show that epigenetic alterations are common events in epithelial odontogenic tumours.

Occurrence of methyl tert-butyl ether (MTBE) in riverbank fiftered water and drnking water produced by riverbank filtration. 2.

Bank filtration of river or lake water represents an efficient and natural purification process used for the drinking water production in many countries and at an amount of about 15-16% in Germany. From experiences over decades particularly at the river Rhine and Elbe, it is known that the occurrence of persistent pollutants in river water can represent a problem for the quality of drinking water produced by bank filtration. The common detection of the gasoline additive methyl tert-butyl ether (MTBE) in drinking water and the announced phase-out of the oxygenate in the U.S. show that MTBE can contaminate large water amounts due to its physicochemical properties. The MTBE situation in the U.S differs from Europe, and significantly lower concentrations in the German environment can be expected. Average MTBE concentrations of 200-250 ng/L in the Lower Main and Lower Rhine river in 2000/2001 were reported. At two sites at the Lower Rhine and Lower Main rivers MTBE concentrations in bank filtered water (n = 22), recovering well water, raw water, and drinking water produced by the water utility at the Lower Rhine site (n = 30) and tap water at Frankfurt/M City (n = 13) were analyzed from 1999 to 2001. Sample analysis is performed by a combination of headspace-solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC/MS) with a detection limit of 10 ng/L and a relative standard deviation of 11%. At the Lower Rhine site up to 80 m from the river an average MTBE concentration of 88 ng/L in riverbank filtered water, recovering well water, and raw water (n = 7) and of 43-110 ng/L in drinking water (n = 3) result. At the Lower Main site up to 400 m from the river MTBE concentrations from 52 to 250 ng/L (n = 7) were measured. Tap water samples at Frankfurt/M (mean of 35 ng/L, maximum of 71 ng/L) were in the same range as MTBE amounts in drinking water at the Lower Rhine site. Measured MTBE amounts eliminated by bank filtration at the Lower Rhine site are comparable to other contaminants. The results of this study show that concentrations measured in river water and drinking water are approximately 2-3 orders of magnitude lower than the U.S. drinking water standard of 20-40 microg/L, represent trace-level concentrations, and are not of major concern nowadays. However, the unfavorable combination of the occurrence of nonpoint MTBE emissions and the persistent behavior of the ether in water even at low concentrations should not be neglected in future discussion. The reported MTBE concentrations are relevant for precautionary aspects. MTBE concentrations in German river water show a tendency toward increasing concentrations since 1999, and in the future possible higher concentrations could represent a risk for the quality of drinking water that is being produced by water utility using bank filtered river water.

DNA methylation in mycobacteria: Absence of methylation at GATC (Dam) and [formula omitted] (Dcm) sequences

The presence of 6-methyladenine and 5-methylcytosine at Dam (GATC) and Dcm ( CCA TGG ) sites in DNA of mycobacterial species was investigated using isoschizomer restriction enzymes. In all species examined, Dam and Dcm recognition sequences were not methylated indicating the absence of these methyltransferases. On the other hand, high performance liquid chromatographic analysis of genomic DNA from Mycobacterium smegmatis and Mycobacterium tuberculosis showed significant levels of 6-methyladenine and 5-methylcytosine suggesting the presence of DNA methyltransferases other than Dam and Dcm. Occurrence of methylation was also established by a sensitive genetic assay.

Über Arthropodenabwehrstoffe, LXV. Die Chemische Ökologie des Grundschwimmers Laccophilus minutus / On Arthropode Defensive Compounds, LXV. The Chemical Ecology of the Water Beetle Laccophilus minutus

According to a GC-MS analysis of methylated extracts the abdominal tips of the water beetle Laccophilus minutus (Dytiscidae) contain four β-hydroxyalkanoic acids. On the basis of MS and GC data another compound was assigned the structure of 6-octenoic acid. The same β-hydroxyalkanoic acids, and in addition, traces of β-hydroxyheptanoic acids were identified in dissected pygidial defensive glands after trimethylsilylation. Methyl 3,4-dihydroxyphenylacetate was recognized as a further main component in the pygidial gland secretion from the mass spectrum of its TMSi ether. The Laccophilinae occupy unique position among all the dytiscide subfamilies because they are the only water beetles which store β-hydroxyalkanoic acids in their pygidial glands. On the other hand the dytiscides appear to form a monophyletic group which is supported by the occurrence of methyl 3,4-dihydroxyphenylacetate. This class of compound is also commonly encountered in the other dytiscide subfamilies

Occurrence of Methyl (+)-Abscisate as an Artefact of Extraction

Alkaline methanolic extracts of avocado (Persea gratissima) fruit contain large amounts of methyl (+)-abscisate but little or no (+)-ABA is liberated by alkaline hydrolysis of the aqueous solution left after extraction of ether-soluble acidic and neutral compounds. No methyl (-t-)-abscisate is detectable in acetone or acidic methanol extracts but (+)-ABA can be released by alkaline hydrolysis of the aqueous solution in these experiments. It is concluded that methyl (-f)-abscisate is an artefact of extraction caused by the methanolysis of a conjugate in neutral or basic conditions. Reports of neutral inhibitors in plant extracts require re-examination because some of the inhibitory activity may be attributable to methyl (+)-abscisate formed during methanol extraction. (+)-ABA biosynthesised from (+)-[3'-14C]mevalonolactone by avocados had a higher specific activity than had the bound (+)-ABA; this suggests that free (+)-ABA is formed first and the conjugate is derived from this, rather than the reverse.

Studies Related to Naturally Occurring Acetylene Compounds. IX. The Occurrence of Methyl dec-8-cis-en4:6-diynoate (= alpha,beta-Dihydro-Matricaria Ester) and 2-cis; 8-trans-Matricaria Ester in Nature.

Studies Related to Naturally Occurring Acetylene Compounds. IX. The Occurrence of Methyl dec-8-cis-en4:6-diynoate (= alpha,beta-Dihydro-Matricaria Ester) and 2-cis; 8-trans-Matricaria Ester in Nature.