Time course evaluation of N-nitrosodialkylamines-induced DNA alkylation and oxidation in liver of mosquito fish

Here we simultaneously measured N7-alkylguanines and 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) in liver of small fish, respectively, to assess the time course of the formation and removal of alkylation and oxidative damage to DNA caused by N-nitrosodialkylamines. Mosquito fish (Gambusia affinis) were killed at various times during (4 days) and post-exposure (16 days) to N-nitrosodimethylamine (NDMA) and N-nitrosodiethylamine (NDEA) alone or their combination with concentrations of 10 and 50 mg/l. The modified guanine adducts were sensitively and selectively quantitated by isotope-dilution LC–MS/MS methods. During exposure, N7-methylguanine (N7-MeG) and N7-ethylguanine (N7-EtG) in liver DNA increased with the duration and dose of N-nitrosodialkylamine exposure, while 8-oxodG was dose-dependently induced within 1 day. It was found that NDMA formed substantially more N7-alkylated guanines and 8-oxodG than NDEA on the basis of adducts formed per micromolar concentration, suggesting that NDMA can be more easily bioactivated than NDEA to form reactive alkylating agents with the concomitant formation of oxygen radicals. After cessation of exposure, N7-alkylguanines remained elevated for 1 day and then gradually decreased over time but still higher than the background levels, even at day 16 (half-lives of 7–8 days). However, 8-oxodG was excised quickly from liver DNA and returned to the background level within 4 days post-exposure (half-lives less than 2 days). Taken together, this study firstly demonstrated that in addition to alkylation, N-nitrosodialkylamines can concurrently cause oxidative damage to DNA in vivo.     

Enhanced conversion rate of L-phenylalanine by coupling reactions of aminotransferases and phosphoenolpyruvate carboxykinase in Escherichia coli K-12.

In Escherichia coli, aspartate aminotransferase (encoded by aspC) and aromatic amino acid aminotransferase (encoded by tyrB) share overlapping substrate specificity in the syntheses of aromatic amino acids. Through the transamination reactions catalyzed by AspC or TyrB, L-phenylalanine (L-Phe) can be produced from phenylpyruvate with aspartic acid as the amino donor. To modulate and enhance the production levels of proteins, both aspC and tyrB were subcloned into a runaway-replication vector. As a result, the specific activities of AspC and TyrB obtained showed 65-fold and 50-fold increases, respectively, compared with the wild-type level. Employing resting cells of AspC- and TyrB-overproducing E. coli K-12 strains for L-Phe productions resulted in molar conversion yields of 70% and 55%, respectively. With an additional introduction of phosphoenolpyruvate carboxykinase (encoded by pck) into the transamination reactions, the conversion yields were improved to 93% from 70% and to 75% from 55% in a relatively short time. These results account for more than an 8-fold increase in productivity, as compared to the previous report (Calton et al., 1985). In addition, a four-run reuse of the recombinant cells for L-Phe production gave a total yield of 91 g/L with a 93% conversion.     

Micromonospora violae sp. nov., isolated from a root of Viola philippica Car

A novel actinomycete, designated strain NEAU-zh8^T, was isolated from a root of Viola philippica Car collected in China and characterized using a polyphasic approach. 16S rRNA gene sequence similarity studies showed that strain NEAU-zh8^T belongs to the genus Micromonospora, being most closely related to Micromonospora chokoriensis 2-9(6)^T (99.9 %), Micromonospora saelicesensis Lupac 09^T (99.3 %) and Micromonospora lupini Lupac 14N^T (99.0 %). gyrB gene analysis also indicated that strain NEAU-zh8^T should be assigned to the genus Micromonospora. The cell-wall peptidoglycan consisted of meso-diaminopimelic acid and glycine. The major menaquinones were MK-10(H₄), MK-10(H₂) and MK-10(H₆). The phospholipid profile contained diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylinositol. The major fatty acids were iso-C_15:0, C_16:0 and C_17:0 10-methyl. A combination of DNA–DNA hybridization results and some physiological and biochemical properties indicated that strain NEAU-zh8^T could be readily distinguished from the closest phylogenetic relatives. Therefore, it is proposed that strain NEAU-zh8^T represents a novel Micromonospora species, for which the name Micromonospora violae sp. nov. is proposed. The type strain is NEAU-zh8^T (=CGMCC 4.7102^T=DSM 45888^T).     

Detection and correction of assembly errors of rice Nipponbare reference sequence

A complete and high‐quality genome reference sequence of an organism provides a solid foundation for a wide research community and determines the outcomes of relevant genomic, genetic, molecular and evolutionary research. Rice is an important food crop and a model plant for grasses, and therefore was the first chosen crop plant for whole genome sequencing. The genome of the japonica representative rice variety, Nipponbare, was sequenced using a gold standard, map‐based clone‐by‐clone strategy. However, although the Nipponbare reference sequence (RefSeq) has the best quality for existing crop genome sequences, it still contains many assembly errors and gaps. To improve the Nipponbare RefSeq, first a robust method is required to detect the hidden assembly errors. Through alignments between BAC‐end sequences (BESs) embedded in the Nipponbare bacterial artificial chromosome (BAC) physical map and the Nipponbare RefSeq, we detected locations on the Nipponbare RefSeq that were inversely matched with BESs and could therefore be candidates for spurious inversions of assembly. We performed further analysis of five potential locations and confirmed assembly errors at those locations; four of them, two on chr4 and two on chr11 of the Nipponbare RefSeq (IRGSP build 5), were found to be caused by reverse repetitive sequences flanking the locations. Our approach is effective in detecting spurious inversions in the Nipponbare RefSeq and can be applied for improving the sequence qualities of other genomes as well.     

An efficient preparation of polyanionic affinity agent and its evaluation for the measurement of glycated hemoglobin

An efficient method was developed for the preparation of polyanionic affinity agent (3), a key component in the measurement of glycated hemoglobin (GHb). Glycated hemoglobin is an important clinical marker for diagnosis of patients with diabetes and useful to monitor the management of disease. The affinity agent (3) was prepared based on coupling reaction between poly(acrylic acid) (1) and 3-aminophenylboronic acid (2) in water. The critical features of this polymeric affinity agent (3), such as size, boronic acid incorporation ratio and concentration, on the measurement of glycated hemoglobin were evaluated. It was found that the agent (3) prepared using poly(acrylic acid) (1) with 225 kDa molecular weight gave optimal GHb measurement. The performance test results demonstrated that the boronic acid incorporation ratio and concentration of affinity agent (3) play a critical role in the assay and determines the precision of glycated hemoglobin measurement.     

长裙竹荪正己烷提取物化学组成及抑菌活性研究

以正己烷为溶剂,对长裙竹荪子实体进行索氏提取,提取率为1.36%。应用GC-MS对提取物的化学成分进行分析,Rxi-1ms柱分离,质谱解析鉴定出55种成分,其中23种成分是首次从竹荪属中检测出来,其主要成分为:羧酸、醇、酮、倍半萜、芳香烃、酯等。提取物对伤寒杆菌、金黄色葡萄球菌、变形杆菌和枯草芽孢杆菌有很好的抑制作用。     

Dynamic Changes of Lipopolysaccharide Levels in Different Phases of Acute on Chronic Hepatitis B Liver Failure

Background

High serum levels of lipopolysaccharide (LPS) with LPS-MD-2/TLR4 complex activated NF-kb and cytokine cause hepatic necrosis in animal models. We investigated the dynamic changes of LPS levels in patients with acute on chronic hepatitis B liver failure (ACHBLF).

Methods

We enrolled ACHBLF patients for a 12-week study. Patients’ LPS levels were measured along with 10 healthy controls. Patients on supportive care and recovered without intervention(s) were analyzed. Patients’ LPS levels during the disease progression phase, peak phase, and remission phase were compared with healthy controls.

Results

Among 30 patients enrolled, 25 who received interventions or expired during the study period were excluded from the analysis, five patients on supportive care who completed the study were analyzed. Significant abnormal distributions of LPS levels were observed in patients in different phases (0.0168±0.0101 in progression phase; 0.0960±0.0680 in peak phase; 0.0249±0.0365 in remission phase; and 0.0201±0.0146 in controls; respectively, p<0.05). The highest level of LPS was in the peak phase and significantly elevated when compared to controls (0.0201±0.0146 vs. 0.0960±0.0680, p = 0.007). There were no statistically significant differences in LPS levels between healthy controls and subjects in the progression phase or remission phase. Dynamic changes of LPS were correlated with MELD-Na in the progression phase (p = 0.01, R = 0.876) and in the peak phase (p = 0.000, R = −1.00).

Conclusions

Significant abnormal distributions of LPS levels were observed in ACHBLF with the highest level in the peak phase. The dynamic changes of LPS were correlated with disease severity and suggested LPS causing secondary hepatic injury.     

Diazotroph abundance and community composition in an acidic soil in response to aluminum-tolerant and aluminum-sensitive maize (Zea mays L.) cultivars under two nitrogen fertilizer forms

Plant and Soil - In acidic soil, plant aluminum (Al) tolerance and nitrogen (N) fertilizer form play the important roles in influencing plant growth. Diazotrophs as plant growth promoting...     

Molecular characterization of β-lactam-resistant Escherichia coli isolated from Fu River, China

The present study aims to demonstrate the β-lactam resistance phenotypes and genotypes of Escherichia coli isolates from the Fu River in Chengdu, southwestern China. We obtained 108 E. coli isolates from nine sampling sites during May and December 2010. The total bacterial count varied from 79 colony-forming units (CFU)/ml to 14,550 CFU/ml, and coliform group number from 13 to 1,435 MPN/ml. Among the 108 isolates, 0-31.48% were resistant to β-lactams and β-lactam inhibitors, 1.85-7.40% to aminoglycoside, 1-20% to fluoroquinolone, and 50% to trimethoprim- sulfamethoxazole. The total bacterial count and antimicrobial resistance of different sites were significantly correlated (P < 0.05). Among the 34 ampicillin-resistant isolates, polymerase chain reaction (PCR) amplification and DNA sequencing showed that bla (TEM), bla (SHV), and bla (CTX-M) were detected in 85.29% (n = 29), 41.18% (n = 14), and 5.88% (n = 2) of the isolates, respectively, whereas bla (KPC) and bla (GES) were not observed in any of the isolates. Enterobacterial repetitive intergenic consensus-PCR patterns revealed that the 34 ampicillin-resistant E. coli isolates belonged to three distinct groups. Plasmid DNAs from the 14 SHV producer isolates yielded one to five bands of ca. 0.15-40 kb. To our knowledge, the current study is the first to describe the phenotypic and genetic characterizations of β-lactam resistance in E. coli isolates of river water origin from the Fu River, Chengdu, southwestern China. Results of the present study suggest that the river water may be considered as a reservoir for antibiotic resistance genes.     

The decline in ascorbic acid content is associated with cadmium toxicity of rice seedlings

Cadmium (Cd) toxicity of rice (Oryza sativa L. cv. Taichung Native 1) seedlings was evaluated by the decrease in chlorophyll content and the increase in malondialdehyde (MDA) in the second leaves of rice seedlings. CdCl₂ (5 μM) treatment was accompanied by a decrease in the contents of ascorbic acid (AsA) and AsA + dehydroascorbate (DHA) and in the ratios of AsA/DHA in leaves. However, CdCl₂ treatment resulted in an increase in DHA content in leaves. Moreover, the decrease in AsA content was prior to the occurrence of chlorosis and associated with the increase in MDA content in the leaves of seedlings treated with Cd. Pretreatment with 0.5 mM AsA or l-galactono-1,4-lactone (GalL), the biosynthetic precursor of AsA, for 6 h resulted in an increase in the contents of AsA and reduced glutathione (GSH), the ratios of AsA/DHA and GSH/oxidized glutathione, and the activities of ascorbate peroxidase (APX) and glutathione reductase (GR) in the leaves of rice seedlings. Quantitative RT-PCR was applied to quantify the mRNA levels for OsAPX and OsGR genes from rice leaves to examine the effect of AsA or GalL pretreatment on the expression of OsAPX and OsGR genes in rice leaves. The expression of OsAPX2, OsAPX3, OsAPX4, OsAPX5, OsAPX6, OsAPX7, and OsGR1 was increased by AsA or GalL pretreatment. Rice seedlings pretreated with AsA or GalL were observed to reduce the subsequent Cd-induced toxicity. Our results suggest that AsA content may play a role in regulating Cd toxicity of rice seedlings.