Argonaute-integrated isothermal amplification for rapid, portable, multiplex detection of SARS-CoV-2 and influenza viruses.

Isothermal amplification methods are a promising trend in virus detection because of their superiority in rapidity and sensitivity. However, the generation of false positives and limited multiplexity are major bottlenecks that must be addressed. In this study, we developed a multiplex Argonaute (Ago)-based nucleic acid detection system (MULAN) that integrates rapid isothermal amplification with the multiplex inclusiveness of a single Ago for simultaneous detection of multiple targets such as SARS-CoV-2 and influenza viruses. Owing to its high specificity, MULAN can distinguish targets at a single-base resolution for mutant genotyping. Moreover, MULAN also supports portable and visible devices with a limit of detection of five copies per reaction. Validated by SARS-CoV-2 pseudoviruses and clinical samples of influenza viruses, MULAN showed 100% agreement with quantitative reverse-transcription PCR. These results demonstrated that MULAN has great potential to facilitate reliable, easy, and quick point-of-care diagnosis for promoting the control of infectious diseases.

Antitumor Effects of Astaxanthin on Esophageal Squamous Cell Carcinoma by up-Regulation of PPARγ.

Esophageal squamous cell carcinoma is a malignant tumor that is difficult to find and has a poor prognosis. The aim of this study is to explore the chemoprevention effect of Astaxanthin (AST) and reveal the possible mechanism of AST on the development of esophageal cancer based on PPARγ. We found that a stable and strong binding between PPARγ molecules and AST molecules using Autodock 4.0 software. AST significantly inhibited the viability of EC109 cells in a dose and time dependent manners (all P < 0.05), and up-regulated the protein expression level of PPARγ from the concentration of 6.25 µM (P < 0.05). Animal experiment showed that AST significantly decreased the incidences of NMBzA-induced esophageal carcinogenesis at 50 mg/kg AST in F344 rats (P < 0.05). AST inhibited the oxidative stress by improving the levels of superoxide dismutase (SOD), total antioxidant capacity (TAOC) and suppressing malondialdehyde (MDA) in serum, and increasing the protein of PPARγ, Bax/Bcl-2, Caspase-3 in esophagus tissue, especially in the 50 mg/kg of AST intervention group (all P < 0.05). In conclusion, our data suggested that protective effect of AST on esophageal cancer by inhibiting oxidative stress, up-regulating PPARγ, and activating the apoptotic pathway, which could provide a basis for clinical application of AST.

Association between dietary related factors and central obesity among married women: China Health and Nutrition Survey.

Waist-to-height ratio (WHtR) with a cut-off value of 0.5 has been recognized as an anthropometric indicator of central obesity to predict the risk of the chronic disease. The aim of our study was to identify dietary related risk factors of central obesity based on WHtR. We used cross-sectional data from the China Health and Nutrition Survey (CHNS) in 2011 obtained from 2881 married women aged 19-55. The association of dietary related factors and central obesity was analyzed using binary logistic regression and back-propagation artificial neural network. Overall, central obesity prevalence was 48.4% (1394/2881). Compared to the population of women without central obesity, the population of women with central obesity had an older average age (41.84 ± 6.89 years vs 38.45 ± 7.91 years, P < 0.001), and meanwhile an average lower per capita annual income (13904 ± 15916 CNY vs 16753 ± 19163 CNY, P < 0.001). Our analysis indicated that the score of dietary knowledge (adjusted odds ratio (aOR), 0.956; 95% confidence interval (CI), 0.936-0.976) and the score of food preferences (aOR, 0.961; 95% CI, 0.926-0.997) were significantly associated with lower risk of central obesity; whereas fast food (aOR, 1.002; 95% CI, 1.000-1.003) was associated with higher risk of central obesity. The study showed the score of dietary knowledge (15.5%), fast foods (10.2%), and the score of food preferences (8.8%) were the most important modifiable factors for central obesity. In summary, aging, fast food intake, and lower per capita annual income were positively associated with higher prevalence of central obesity, while higher scores of dietary knowledge and food preferences were negatively correlated. More nutrition education programs should be implemented by the government to strengthen the pro-healthy dietary behaviors.

Argonaute integrated single-tube PCR system enables supersensitive detection of rare mutations.

Technological advances in rare DNA mutations detection have revolutionized the diagnosis and monitoring of tumors, but they are still limited by the lack of supersensitive and high-coverage procedures for identifying low-abundance mutations. Here, we describe a single-tube, multiplex PCR-based system, A-Star, that involves a hyperthermophilic Argonaute from Pyrococcus furiosus (PfAgo) for highly efficient detection of rare mutations beneficial from its compatibility with DNA polymerase. This novel technique uses a specific guide design strategy to allow PfAgo selective cleavage with single-nucleotide resolution at 94°C, thus mostly eliminating wild-type DNA in the denaturation step and efficiently amplifying rare mutant DNA during the PCR process. The integrated single-tube system achieved great efficiency for enriching rare mutations compared with a divided system separating the cleavage and amplification. Thus, A-Star enables easy detection and quantification of 0.01% rare mutations with ≥5500-fold increase in efficiency. The feasibility of A-Star was also demonstrated for detecting oncogenic mutations in solid tumor tissues and blood samples. Remarkably, A-Star achieved simultaneous detection of multiple oncogenes through a simple single-tube reaction by orthogonal guide-directed specific cleavage. This study demonstrates a supersensitive and rapid nucleic acid detection system with promising potential for both research and therapeutic applications.

Changes of Serum Zinc-α2-Glycoprotein Level and Analysis of Its Related Factors in Gestational Diabetes Mellitus.

Previous studies have discovered that zinc-α2-glycoprotein (ZAG) is related to insulin resistance and lipid metabolism. The aim of the study is to explore the change of serum ZAG and its related factors in gestational diabetes mellitus (GDM). Eighty newly diagnosed GDM patients were enrolled in the case group, and 80 normal pregnant women were selected as the control group. The differences of baseline data between the two groups were compared, and the change of serum ZAG level and its relationship with related indexes was analyzed. Compared to the control group, the level of serum ZAG in GDM women decreased (P < 0.001). What is more, the serum ZAG level of overweight and normal subjects in two groups was also found to have statistical differences. The Pearson correlation (or Spearman correlation) analysis showed that serum ZAG level was negatively correlated with FPG, FINS, HOMA-IR, and TG (all P < 0.05) and positively correlated with HDL (P < 0.05). Multiple linear regression showed that HDL and HOMA-IR were independent factors of serum ZAG (P < 0.05). The level of serum ZAG in patients with gestational diabetes mellitus decreased, and HDL and HOMA-IR are the influencing factors in the case group.

[Distribution Characteristics of Carbon, Nitrogen, and Phosphorus Bearing Pollutants in the Ancient Town Rivers of Suzhou].

Suzhou is a water-deficient city with water quality issues. Despite water conservation measures, emission reductions, source control, and pollution interception, water quality remains poor. To understand the total mass and distribution characteristics of carbon, nitrogen, and phosphorus bearing pollutants and inform decisions regarding river dredging, sediment and water samples were collected from 20 representative sections in the town's rivers during the spring of 2019. The depths of the sediments were measured along with the concentrations of carbon, nitrogen, and phosphorus bearing pollutants in the sediments and water, and the pollution degree was evaluated. Variations in various parameters were predicted for change water, diversion water, rainfall, and dredging. The results show that the sediment depths ranged between 22 and 1025 mm (average=266 mm), and the total mass of sediment was approximately 5.2×105 t in the ancient town rivers of Suzhou. The average proportions and concentrations of TOC, TN, NH4+-N, TP, and AP in the sediments were 3.4%, 2074 mg·kg-1, 140.2 mg·kg-1, 1765 mg·kg-1, and 57.2 mg·kg-1, respectively, indicating a moderate level of pollution. The concentration of TP in the sediments at 90% of the sampling points exceeds the national standard. Huancheng River was found to have the highest concentration of TP, suggesting that dredging shuld be targeted here first. In the water samples, the average concentrations of TOC, BOD5, COD, TN, NH4+-N, Kjeldahl nitrogen, TP, and PO43--P were 7.8, 0.6, 13.1, 2.5, 0.643, 1.3, 0.18, and 0.09 mg·L-1, respectively, indicating a severe level of pollution. Overall, water quality in these rivers falls below Class V surface water, and the concentration of TN seriously exceeds the national standard. Based on the patterns of total carbon mass and nitrogen and phosphorus bearing pollutants, the recommended order of dredging in Suzhou is the Huancheng River, the northern rivers of the ancient town, Ganjiang River, and the southern rivers of the ancient town. Under the rainfall scenario, the initial concentrations of pollutants in runoff were high, which leads to a decline in water quality. The total mass of TN in the water was reduced by 0.2 t under the change water and diversion water scenarios, and was further reduced by 4.58 t and 2.19 t, respectively, after dredging. Phosphorus bearing pollutants in the sediment were mainly imported from other sources, meaning that the total mass of TP in the water may increase following dredging activities.

Argonaute with stepwise endonuclease activity promotes specific and multiplex nucleic acid detection.

Argonaute proteins (Agos) from thermophiles function as endonucleases via guide-target base-pairing cleavage for host defense. Since guides play a key role in regulating the catalytic specificity of Agos, elucidating its underlying molecular mechanisms would promote the application of Agos in the medical sciences. Here, we reveal that an Ago from Pyrococcus furiosus (PfAgo) showed a stepwise endonuclease activity, which was demonstrated through a double-stranded DNA cleavage directed by a single guide DNA (gDNA) rather than a canonical pair of gDNAs. We validated that the cleavage products with 5'-phosphorylated ends can be used as a new guide to induce a new round of cleavage. Based on the reprogrammable capacity of Ago's stepwise activity, we established a rapid and specific platform for unambiguous multiplex gene detection, termed Renewed-gDNA Assisted DNA cleavage by Argonaute (RADAR). Combined with a pre-amplification step, RADAR achieved sensitivity at the femtomolar level and specificity with at least a di-nucleotide resolution. Furthermore, RADAR simultaneously discriminated among multiple target sequences simply by corresponding multiple guides. We successfully distinguished four human papillomavirus serotypes from patient samples in a single reaction. Our technique, based on the unique properties of Ago, provides a versatile and sensitive method for molecular diagnosis.

Effect of sPP Content on Electrical Tree Growth Characteristics in PP-Blended Cable Insulation.

This paper aims at investigating the electrical tree characteristics of isotactic polypropylene (iPP)/syndiotactic polypropylene (sPP) blends for thermoplastic cable insulation. PP blended samples with sPP contents of 0, 5, 15, 30, and 45 wt% are prepared, and electrical treeing experiments are implemented under alternating current (AC) voltage at 50, 70, and 90 °C. Experimental results show that with the incorporation of sPP increasing to 15 wt%, the inception time of electrical tree increases by 8.2%. The addition of sPP by 15% distinguishes an excellent performance in inhibiting electrical treeing, which benefits from the ability to promote the fractal dimension and lateral growth of branches. Further increase in sPP loading has a negative effect on the electrical treeing resistance of blended insulation. It is proved by DSC and POM that the addition of sPP promotes the heterogeneous crystallization the of PP matrix, resulting in an increasing density of interfacial regions between crystalline regions, which contains charge carrier traps. Charges injected from an electrode into a polymer are captured by deep traps at the interfacial regions, thus inhibiting the propagation of electrical tree. It is concluded that the modification of crystalline morphology by 15 wt% sPP addition has a great advantage in electrical treeing resistance for PP-based cable insulation.

A novel bulk density-based recognition method for kitchen and dry waste: A case study in Beijing, China.

Identification technology of household kitchen and dry solid waste has played a major part in improving the accuracy of residents' separation by intelligent outdoor trashcan, which is an effective integral solid waste management tool for growing household solid waste (HSW). Our study aims to present a novel and simple recognition method for kitchen and dry waste based on bulk density. In three communities in Beijing, 270 bagged waste samples were collected, and their moisture content, separation accuracy, and bulk density, characterized. Then a bulk density index was developed to straightforwardly express residents' waste source separation accuracy by linear regression analysis above physical properties. In the 3 Beijing communities, we demonstrated a clear distinction in the bulk density index, for dry, mixed, and kitchen waste of <115, 115-211, >211 kg/m3, respectively. Our results provide a theoretical basis for the establishment of an intelligent waste supervision system, which is of great significance for waste management in developing countries like China.

Passive Film Properties of Bimodal Grain Size AA7075 Aluminium Alloy Prepared by Spark Plasma Sintering.

The bimodal-grain-size 7075 aluminium alloys containing varied ratios of large and small 7075 aluminium powders were prepared by spark plasma sintering (SPS). The large powder was 100 ± 15 µm in diameter and the small one was 10 ± 5 µm in diameter. The 7075 aluminium alloys was completely densified under the 500 °C sintering temperature and 60 MPa pressure. The large powders constituted coarse grain zone, and the small powders constituted fine grain zone in sintered 7075 aluminium alloys. The microstructural and microchemical difference between the large and small powders was remained in coarse and fine grain zones in bulk alloys after SPS sintering, which allowed for us to investigate the effects of microstructure and microchemistry on passive properties of oxide film formed on sintered alloys. The average diameter of intermetallic phases was 201.3 nm in coarse grain zone, while its vale was 79.8 nm in fine grain zone. The alloying element content in intermetallic phases in coarse grain zone was 33% to 48% higher than that on fine grain zone. The alloying element depletion zone surrounding intermetallic phases in coarse grain zone showed a bigger width and a more severe element depletion. The coarse grain zone in alloys showed a bigger electrochemical heterogeneity as compared to fine grain zone. The passive film formed on coarse grain zone had a thicker thickness and a point defect density of 2.4 × 1024 m-3, and the film on fine grain zone had a thinner thickness and a point defect density of 4.0 × 1023 m-3. The film resistance was 3.25 × 105 Ωcm2 on coarse grain zone, while it was 6.46 × 105 Ωcm2 on fine grain zone. The passive potential range of sintered alloys increased from 457 mV to 678 mV, while the corrosion current density decreased from 8.59 × 10-7 A/cm2 to 6.78 × 10-7 A/cm2 as fine grain zone increasing from 0% to 100%, which implied that the corrosion resistance of alloys increased with the increasing content of fine grains. The passive film on coarse grain zone exhibited bigger corrosion cavities after pitting initiation compared to that on fine grain zone. The passive film formed on fine grain zone showed a better corrosion resistance. The protectiveness of passive film was mainly determined by defect density rather than the thickness in this work.

Anticancer effects and possible mechanisms of lycopene intervention on N-methylbenzylnitrosamine induced esophageal cancer in F344 rats based on PPARγ1.

Lycopene, a natural carotenoid, has potential chemopreventive effects in many cancers. This study aimed to examine the effects of lycopene on regulating the inflammation and apoptosis of N-nitrosomethylbenzylamine(NMBzA) induced esophageal cancer in F344 rats. After the rats were fed normal diets containing different concentrations of lycopene for 25 weeks (10, 25, 50 mg/kg·d of lycopene, respectively), the incidence of tumors in the rats treated with lycopene was significantly lower than that in the simple exposed group (P < 0.05). The antioxidant activity of lycopene was exerted by measuring the levels of GSH-PX, SOD and MDA activity by oxidative stress kits. Furthermore, through western blotting analysis lycopene intervention was found to have significantly improved apoptosis cytokines by increasing the protein expression levels of PPARγ and caspase-3, and also significantly reduced inflammatory cytokines by decreasing the protein expression of NF-κB and COX-2 in the esophagus tissue, especially in the 25 mg/kg of lycopene intervention group (all P < 0.05). These results demonstrated that appropriate dose of lycopene intervention could inhibit the carcinogenesis of esophageal in F344 rats through the possible mechanisms of anti-inflammatory and pro-apoptosis.

A LCMS-based untargeted lipidomics analysis of cleft palate in mouse.

BACKGROUND: Recent studies have shown that lipid metabolism was abnormal during the formation of cleft palate. However, the composition of these lipid species remains unclear. OBJECTIVE: Aims of this study were to identify the lipid species components and reveal the key lipid metabolic disorders in cleft palate formation. METHODS: The pregnant mice were divided into experimental group exposed to all-trans retinoic acid (RA-treated group) (n = 12) and control group (n = 12) at embryonic gestation day 10.5 (E0.5). The component of the palatal tissue metabolome was analyzed using a LCMS-based nontargeted lipidomics approach. Multivariate statistical analysis was then carried out to assess the differences between the RA-treated group and the control group. RESULTS: Twenty-nine lipid species were found to discriminate between RA-treated and control embryos. Among them, 28 lipid species increased and 1 lipid species decreased in the RA-treated group. Among these lipids, 13 were triglycerides, 9 were PEs, 3 were PCs, 2 were PSs, 2 were DGs. Further analysis of the number of carbons and unsaturated bond of triglycerides showed that TGs with high unsaturated bonds constituted a higher fraction in the RA-treated group. A higher amount of triglycerides containing 52, 54, 56, 58, 60 carbons, and 1 to 8 unsaturated bonds. Of note, under RA treatment, TG 50:1, 52:2, 56:6and 60:8 became the most prominent. CONCLUSION: Lipid metabolism is significantly different in the formation of cleft palate induced by RA, and the unsaturated triglycerides increased in the RA-treated group may play an important role in the formation of cleft palate.

Mining database for the expression and gene regulation network of JAK2 in skin cutaneous melanoma.

BACKGROUND: Skin cutaneous melanoma (SKCM) is the most common subtype of skin malignancy, with ever-increasing incidence, mortality, and disease burden. Dysregulation of JAK-STATs signaling pathway is involved in the pathogenesis and progression of cancers, thus affecting the prognosis of cancer patients. The function of JAKs in SKCM is still not clarified. METHODS: A total of five online portal (GEPIA, TIMER, GeneMANIA, LinkedOmics, and GSCALite) is used to mine the expression and gene regulation network JAK2 in SKCM. RESULTS: JAK2 expression was downregulated in SKCM and significantly associated with pathological stage and the prognosis of patients. The functions of JAK2 and associated genes were primarily involved in the DNA recombination, cell cycle checkpoint, metabolic process, NOD-like receptor signaling pathways, p53 signaling pathway and apoptosis. JAK2 level was significantly correlated with the abundance of immune cells and the level of immune biomarkers. Low expression of JAK2 were resistant to QL-VIII-58, TL-1-85, Ruxolitinib, TG101348 and Sunitinib. CONCLUSIONS: Our results reveal the expression and gene regulation network of JAK2 in skin cutaneous melanoma, providing more evidences about the role of JAK2 in carcinogenesis.

Coupling Effect of Molecular Chain Displacement and Carrier Trap Characteristics on DC Breakdown of HDPE/LDPE Blend Insulation.

This work focuses on the coupling effect of molecular chain displacement and trap characteristics on direct current (DC) breakdown properties of high density/low density polyethylene (HDPE/LDPE) blend insulation. Frequency domain spectroscopy (FDS) and isothermal discharge current (IDC) are used to characterize the dielectric relaxation and trap characteristics of HDPE/LDPE blends. A DC breakdown model is proposed to reveal the mechanisms of the molecular chain displacement and carrier trap on the DC breakdown strength. The dielectric relaxation α and δ present segmental motions and thermal ion polarization behaviours of HDPE/LDPE blends, respectively. α dielectric relaxation strength ( Δεα) increases as the amount of HDPE increases from 0 to 5 wt%, and then declines with a further increase of HDPE content to 20 wt%. According to the velocity equation, the increase of Δεα will increase the molecular chain displacement, resulting in a larger free volume, which will provide electrons with larger free path λ to form hot electrons. A positive correlation exists between the activation energy of the dielectric relaxation process δ and trap density, and the increase of δ dielectric relaxation strength (Δεδ) will adversely affect the breakdown strength of the specimen. HDPE/LDPE blends with 15 wt% HDPE content have lower Δεα and lowest Δεδ, which decreases the mean free path λ of molecular chain and thermal ion polarization. At the same time, it has the highest deep trap density, thus increasing the probability of hot electrons being captured and improving the DC breakdown strength. It is concluded the breakdown of the dielectric is synergistically affected by the molecular chain displacement and carrier trap.

Circulating irisin levels of prenatal and postnatal patients with gestational diabetes mellitus: A systematic review and meta-analysis.

AIMS: At present, there are few studies on the relationship between circulating irisin levels and gestational diabetes mellitus (GDM), and the results are inconsistent. Therefore, this study conducts a systematic review and meta-analysis to comprehensively discuss the role of irisin in the occurrence and development of GDM. METHODS: We searched the articles on the relationship between GDM and circulating irisin levels up to September 2019, using the CNKI, WANFANG-DATA, PubMed and the Web of Science databases. RESULTS: Twenty two articles including 3563 participants were selected in the meta-analysis. Meta-analysis found the blood irisin levels for GDM group were significantly lower than that for control group during pregnancy(SMD = -0.88, 95%CI: -1.34, -0.42, P < 0.001). However, there was no significant difference of irisin levels in the postpartum blood and cord blood between the two groups (SMD = -1.44, 95 %CI: -3.79, 0.92, P = 0.23; SMD = -0.17, 95 %CI: -0.59, 0.25, P = 0.42, respectively). CONCLUSIONS: Compared with the control group, irisin levels in the GDM group during pregnancy are lower. However, it is no significant difference of irisin levels in the postpartum blood and cord blood. Irisin may play an important role in the occurrence and development of GDM, which needs further research to demonstrate.

Dietary natural astaxanthin at an early stage inhibits N-nitrosomethylbenzylamine-induced esophageal cancer oxidative stress and inflammation via downregulation of NFκB and COX2 in F344 rats.

Purpose: Esophageal cancer is a common malignant tumor that develops rapidly and has a poor prognosis clinically. Astaxanthin (AST) is a carotenoid pigment with strong antioxidant, anti-inflammation, and antitumor activities. However, little is known about the effects of astaxanthin in esophageal cancer. The present study aimed to investigate the protective effects and related mechanisms of natural astaxanthin against N-nitrosomethylbenzylamine (NMBA)-induced esophageal cancer in rats. Methods: F344 rats were induced subcutaneously with NMBA dissolved in dimethyl sulfoxide (0.35 mg/kg body weight three times per week for 5 weeks). Rats were fed normal diets with or without 25 mg/kg/day AST at different stages. At different time points, levels of oxidative stress factors in serum and esophagus tissue were analyzed. Western blotting was performed to observe the expression of NFκB and COX2 in esophagus tissue. Results: AST clearly reduced the incidence of visible tumors in esophageal cancer during the early-stage intervention group. Furthermore, when compared with the simple exposed group, AST significantly increased levels of GPx and SOD activity, decreased the activity level of malondialdehyde (all P<0.05). Early-stage and whole-stage intervention groups effectively attenuated expression levels of NFκB and COX2 proteins compared with the simple exposed group (all P<0.05). Conclusion: Natural AST significantly suppressed the occurrence of esophageal cancer by increasing antioxidant capacity and anti-inflammation capacity by inhibiting expression levels of NFκB and COX2 proteins.

Inhibition Effect of Graphene on Space Charge Injection and Accumulation in Low-Density Polyethylene.

Space charge injection and accumulation is attracting much attention in the field of dielectric insulation especially for electronic devices, power equipment and so on. This paper proposes using the inhibition effect of graphene for the injection and accumulation of space charge in low-density polyethylene (LDPE). Scanning electron microscope (SEM) and transmission electron microscopy (TEM) images were employed to observe the dispersion of graphene with a two-dimensional structure in LDPE. The time-dependent space charge dynamic behaviors of graphene/LDPE nanocomposites with the filler content of 0, 0.003, 0.005, 0.007 and 0.01 wt % were characterized by the pulsed electro-acoustic (PEA) test at 40, 60 and 80 °C, and the charge mobility was evaluated by its depolarization processes. The experimental results show that for the undoped LDPE film, large amounts of space charges were injected from the electrodes into samples, especially at 60 and 80 °C. The graphene/LDPE nanocomposites with a filler content of 0.005 wt % could markedly suppress the space charge injection and accumulation even at 80 °C, which is attributed to the large quantities of graphene-polymer in interface regions. These interface regions introduced numbers of deep trap sites within the forbidden band of nanocomposites, which can reduce the de-trapping rate of charges and suppress the space charge accumulation in the polymer bulks. The graphene/LDPE nanocomposites are suggested for dielectric applications, intending the inhibition of space charge injection and accumulation.

Trap Modulated Charge Carrier Transport in Polyethylene/Graphene Nanocomposites.

The role of trap characteristics in modulating charge transport properties is attracting much attentions in electrical and electronic engineering, which has an important effect on the electrical properties of dielectrics. This paper focuses on the electrical properties of Low-density Polyethylene (LDPE)/graphene nanocomposites (NCs), as well as the corresponding trap level characteristics. The dc conductivity, breakdown strength and space charge behaviors of NCs with the filler content of 0 wt%, 0.005 wt%, 0.01 wt%, 0.1 wt% and 0.5 wt% are studied, and their trap level distributions are characterized by isothermal discharge current (IDC) tests. The experimental results show that the 0.005 wt% LDPE/graphene NCs have a lower dc conductivity, a higher breakdown strength and a much smaller amount of space charge accumulation than the neat LDPE. It is indicated that the graphene addition with a filler content of 0.005 wt% introduces large quantities of deep carrier traps that reduce charge carrier mobility and result in the homocharge accumulation near the electrodes. The deep trap modulated charge carrier transport attributes to reduce the dc conductivity, suppress the injection of space charges into polymer bulks and enhance the breakdown strength, which is of great significance in improving electrical properties of polymer dielectrics.

Selenium-mediated protection in reversing the sensitivity of bacterium to the bactericidal antibiotics.

Inducing production of damaging reactive oxygen species (ROS) is an important criterion to distinguish the bactericidal antibiotics from bacteriostatic antibiotics. Selenoenzymes were generally recognized to be a powerful antioxidant capable of scavenging free radicals, protecting the cells from the harmful effects of ROS. Therefore, the present study was carried out to investigate the selenium (Se)-mediated protection in reversing antibiotic sensitivity and the role of selenoenzymes in alleviating the negative effects of oxidative stress. The cellular antioxidant activity of Se-enriched bacteria was analyzed, as well as intracellular ROS production and elimination when Se-enriched bacteria in the presence of various antibiotics. Compared to complete inhibition of the parental strain by bactericidal antibiotics, it only exhibited slight and reversible inhibition of Se-enriched Escherichia coli ATCC25922 and Staphylococcus aureus ATCC25923 at the same conditions, which indicated that intracellular selenium provided substantial protection against antibiotics. ROS generation caused by bactericidal antibiotics was confirmed by fluorescence spectrophotometry using 2', 7'-dichloro- uorescein diacetate (DCFH-DA) as substrate. The time course experiments of pretreatment with selenium showed significant decrease of ROS level at 2h. In summary, the present study provides experimental evidence supporting selenoenzymes has good scavenging effect to ROS and can protect bacteria from oxidative stress injury induced by bactericidal antibiotics.