Ab initio studies on the decomposition kinetics of CF<Subscript>3</Subscript>OCF<Subscript>2</Subscript>O radical

The present study deals with the decomposition of CF₃OCF₂O radical formed from a hydrofluoroether, CF₃OCHF₂ (HFE-125), in the atmosphere. The study is performed using ab initio quantum mechanical methods. Two plausible pathways of decomposition of the titled species have been considered, one involving C-O bond scission and the other occurring via F atom elimination. The geometries of the reactant, products and transition states involved in the decomposition pathways are optimized and characterized at DFT (B3LYP) level of theory using 6-311G(d,p) basis set. Single point energy calculations have been performed at G2M(CC,MP2) level of theory. Out of the two prominent decomposition channels considered, the C-O bond scission is found to be dominant involving a barrier height of 15.3 kcal mol⁻¹ whereas the F-elimination path proceeds with a barrier of 26.1 kcal mol⁻¹. The thermal rate constants for the above two decomposition pathways are evaluated using canonical transition state theory (CTST) and these are found to be 1.78 × 10⁶ s⁻¹ and 2.83 × 10⁻⁷ s⁻¹ for C-O bond scission and F-elimination respectively at 298 K and 1 atm pressure. Transition states are searched on the potential energy surfaces involved during the decomposition channels and each of the transition states is characterized. The existence of transition states on the corresponding potential energy surface is ascertained by performing intrinsic reaction coordinate (IRC) calculation.     

Genome-wide DNA methylation profiles in noncancerous gastric mucosae with regard to Helicobacter pylori infection and the presence of gastric cancer

Background and Aims: To determine genome‐wide DNA methylation profiles induced by Helicobacter pylori (H. pylori) infection and to identify methylation markers in H. pylori‐induced gastric carcinogenesis. Methods: Gastric mucosae obtained from controls (n = 20) and patients with gastric cancer (n = 28) were included. A wide panel of CpG sites in cancer‐related genes (1505 CpG sites in 807 genes) was analyzed using Illumina bead array technology. Validation of the results of Illumina bead array technique was performed using methylation‐specific PCR method for four genes (MOS, DCC, CRK, and PTPN6). Results: The Illumina bead array showed that a total of 359 CpG sites (269 genes) were identified as differentially methylated by H. pylori infection (p < .0001). The correlation between methylation‐specific PCR and bead array analysis was significant (p < .0001, Spearman coefficient = 0.5054). Methylation profiles in noncancerous gastric mucosae of the patients with gastric cancer showed quite distinct patterns according to the presence or absence of the current H. pylori infection; however, 10 CpG sites were identified to be hypermethylated and three hypomethylated in association with the presence of gastric cancer regardless of H. pylori infection (p < .01). Conclusions: Genome‐wide methylation profiles showed a number of genes differentially methylated by H. pylori infection. Methylation profiles in noncancerous gastric mucosae from the patients with gastric cancer can be affected by H. pylori‐induced gastritis. Differentially methylated CpG sites in this study needs to be validated in a larger population using quantitative methylation‐specific PCR method.     

Screening of iron- and zinc-enriched yeast strain and optimization of cultivation conditions

Saccharomyces cerevisiae LN-17 was selected from 26 kinds of primary yeast strains that belong to different genera and species. The iron- and zinc-enriched capability of strain LN-17 was higher than the others. The highest iron and zinc contents of the strain were obtained when the strain grew up under the following conditions: The strain was incubated (5%, v/v) in 50 mL wort medium (pH 6.0) with 100 mg/L Fe ion and 120 mg/L Zn ion. The medium was loaded into a 250-mL Erlenmeyer flask and shaken in a rotary shaker (200 rpm) at 30°C for 60 h. Ferrous sulfate and zinc sulfate were chosen as the source of Fe and Zn. The Fe and Zn contents of the dry cells were determined by atomic absorption spectrum analysis. Under the optimized cultivation conditions, the Fe and Zn contents reached 7.854 mg/g dry cells and 4.976 mg/g dry cells.     

Ceramide induces serotonin release from RBL-2H3 mast cells through calcium mediated activation of phospholipase A2

Ceramide has been suggested to function as a mediator of exocytosis in response to the addition of a calcium ionophore from PC12 cells. Here, we show that although cell-permeable C(6)-ceramide or a calcium ionophore alone did not increase either the degranulation of serotonin or the release of arachidonic acid (AA) from RBL-2H3 cells, their combined effect significantly stimulated these processes in a time- and dose-dependent manner. This effect was inhibited by the presence of an exogenous calcium chelator and significantly suppressed by the CERK inhibitor (K1) and phospholipase A(2) (PLA(2)) inhibitors. Moreover, cytosolic PLA(2) GIVA (cPLA(2) GIVA) siRNA-transfected RBL-2H3 cells showed a lower level of serotonin release than scramble siRNA-transfected cells. Little is known about the regulation of degranulation proximal to the activation of cytosolic phospholipase A(2) GIVA, the initial rate-limiting step in RBL-2H3 cells. In this study, we suggest that CERK, ceramide-1-phosphate, and PLA(2) are involved in degranulation in a calcium-dependent manner. Inhibition of p44/p42 mitogen-activated protein kinase partially decreased the AA release, but did not affect degranulation. Furthermore, treatment of the cells with AA (ω-6, C20:4), not linoleic acid (ω-6, C18:2) or α-linolenic acid (ω-6, C18:3), induced degranulation. Taken together, these results suggest that ceramide is involved in mast cell degranulation via the calcium-mediated activation of PLA(2).     

Regulation of growth performance and lipid metabolism by dietary n-3 highly unsaturated fatty acids in juvenile grass carp, Ctenopharyngodon idellus

To determine the effects of n-3 highly unsaturated fatty acids (HUFAs) in grass carp (Ctenopharyngodon idellus), a 75-day feeding experiment was conducted using five isonitrogenous and isoenergetic semi-purified diets containing 0% (control), 0.26%, 0.52%, 0.83% or 1.13% n-3 HUFAs. Weight gain, specific growth rate, feed efficiency and protein efficiency increased by increasing the dietary HUFAs content from 0% to 0.52%, and declined thereafter. Intraperitoneal fat content and the hepatopancreatic lipid levels were lowest in the 0.52% group. The tissue fatty acid level was well correlated with dietary HUFAs content. Hepatic lipoprotein lipase (LPL) activity was significantly higher in the 0.52% group, while that of malate dehydrogenase (MDH) was stable in the 0-0.52% groups, and was significantly lower in the 1.13% group. Superoxide dismutase (SOD) activity increased significantly with increasing dietary HUFAs content, consistent with the level of malondialdehyde (MDA). Hepatic mRNA expression of peroxisome proliferator-activated receptor-α (PPAR-α) was greatest in the 0.83% group and that of the LPL gene increased with increasing dietary HUFAs content up to 0.83%. These results indicate that adequate dietary HUFAs supplementation significantly promotes growth performance and lipid metabolism in freshwater fish grass carp. However, excess HUFAs fortification may exert adverse effects, which might be due to oxidative stress.     

Morphology and morphogenesis of a freshwater ciliate, Epistylis chlorelligerum Shen, 1980 (Ciliophora, Peritrichia)

An oligohalobic peritrichous ciliate, Epistylis chlorelligerum Shen, 1980, was collected from a ditch in Hangzhou, China. The morphology, oral infraciliature, and morphogenesis of the species were studied using living and protargol-impregnated specimens. Zooids of E. chlorelligerum are 160-230 × 50-60 μm in vivo, and characterized by green-colored endoplasm containing symbiotic algae. The oral infraciliature presents a well-developed filamentous reticulum linked to the circular fiber of the cytostome; the outer two rows of P3 extend adstomally over P1 and usually enfold it. During binary fission, one daughter cell inherits most part of the old buccal apparatus and the reorganized haplokinety and germinal kinety (Hk' and G'), and new buccal apparatus of the other daughter cell is mostly developed from the original germinal kinety (G) and haplokinety (Hk): new peniculi 2, 3 (2P2, 2P3), new haplokinety (2Hk), and new germinal kinety (2G) are formed from G, while the new peniculus 1 (2P1) and its peristomial extention (2Pk) originate from Hk. The epistomial membrane can be observed until the two sets of buccal apparatus begin to separate from each other.     

ABC transporters affect the detection of intracellular oxidants by fluorescent probes

Intracellular production of reactive oxygen species (ROS) plays an important role in the control of cell physiology. For the assessment of intracellular ROS production, a plethora of fluorescent probes is commonly used. Interestingly, chemical structures of these probes imply they could be substrates of plasma membrane efflux pumps, called ABC transporters. This study tested whether the determination of intracellular ROS production and mitochondrial membrane potential by selected fluorescent probes is modulated by the expression and activity of ABC transporters. The sub-clones of the HL-60 cell line over-expressing MDR1, MRP1 and BCRP transporters were employed. ROS production measured by luminol- and L-012-enhaced chemiluminescence and cytochrome c reduction assay showed similar levels of ROS production in all the employed cell lines. It was proved that dihydrorhodamine 123, dihexiloxocarbocyanine iodide, hydroethidine, tetrachloro-tetraethylbenzimidazolocarbo-cyanine iodide and tetramethylrhodamine ethyl ester perchlorate are substrates for MDR1; dichlorodihydrofluoresceine, hydroethidine and tetramethylrhodamine ethyl ester perchlorate are substrates for MRP1; dichlorodihydrofluoresceine, dihydrorhodamine 123, hydroethidine and tetrachloro-tetraethylbenzimidazolocarbo-cyanine iodide are substrates for BCRP. Thus, the determination of intracellular ROS and mitochondrial potential by the selected probes is significantly altered by ABC transporter activities. The activity of these transporters must be considered when employing fluorescent probes for the assessment of ROS production or mitochondrial membrane potential.