Development of a one-pot and sequence-specific LAMP assay based on the self-quenching probe integrated by the complementary oligonucleotide for an enhanced fluorescence quenching.

Single-modified fluorogenic primer (Sfp) enables accurate identification of LAMP amplicons without being affected by non-specific products. However, the fluorescence self-quenching by nucleobases for Sfp is generally of low efficiency, and the high background signal makes it a great challenge to achieve visual inspection with naked eyes. In the present study, the oligonucleotide (Ao) complementary to Sfp was designed, which would hybridize to Sfp and dramatically heighten the quenching effect, leading to a low background signal in negative reaction. Instead, for positive reaction, Sfp is incorporated into the double-stranded amplicons, resulting in dequenching and consequently, enhanced fluorescence. The detection scheme can be further improved by a dual-color fluorescence strategy, allowing visual detection of 1 pg rainbow trout DNA in a closed-tube format within 30 min. Therefore, our LAMP-Ao-Sfp assay represents a useful tool for rapid and sensitive detection, and can serve as a reliable method for on-site detection in low-resource settings.

Influence of alternating electric field on deep dewatering of municipal sludge and changes of extracellular polymeric substance during dewatering.

A self-prepared experimental device made of plexiglass with alternating power supply system was used to study the deep dewatering of municipal dewatered sludge. Considering the reduction rate of sludge water content (Wr) as the index, factors affecting enhanced electric settlement of sludge such as exchange electrode method, voltage gradient, sludge thickness, and mechanical pressure were studied, and the dewatering mechanism was elucidated. The single-factor experiment combined with the surface response method based on the Box-Behnken central experimental design was performed. With Wr as the response value, the voltage gradient conditions, time ratio, and sludge thickness were optimized. Pearson correlation analysis showed that the reduction of proteins/polysaccharides was beneficial to improving the sludge dewatering effect. Tightly bound extracellular polymeric substances (TB-EPSs) showed a significant influence on the sludge dewatering effect. Under the action of the external electric field, particles with negative charge moved toward the anode sludge, water with partial positive charge flowed to the cathode, and the sludge cellular structure was damaged. This resulted in the dissolution of a large number of EPSs and the release of bound water. The anode sludge cake got thickened due to the accumulation of the sludge particles, leading to the increase in resistance. The TB-EPS was deconstructed by the ohmic heating to improve the sludge dewatering effect and achieve deep dewatering. Scanning electron microscopy results showed that the drying problem of anode sludge was alleviated during the dewatering process.

High directionality of surface radiation for surface emitting distributed feedback lasers.

Improving the directionality of surface radiation is the key to increase the output power and the differential quantum efficiency of grating-coupled surface-emitting distributed feedback lasers. We proposed a scheme to realize the high directionality of surface radiation. In the structure, the second-order grating is fabricated on the p-side of the epitaxial wafer. A SiO2/Si3N4 multilayer reflector arranged above the grating is used to redirect the upward-diffracted beam. The design of the intermediate layer between the grating and the reflector is an important part of achieving high directionality, because the adjustment of its thickness can be used to phase the redirected light with the downward-diffracted light. The calculation results show that the directionality of this structural scheme can reach more than 98% which meets the device requirements. This design provides a reference for surface-emitting distributed feedback lasers with high performance and high stability.

Resonant-cavity-enhanced p-i-n photodetector using a high-contrast-grating for 940nm.

Two novel top mirror designs of high contrast gratings (HCG) are used as the top mirrors of the resonant-cavity enhanced photodetector (RCE PD) operating at 940 nm. The bottom mirror is composed of 36-pair AlAs/GaAs, while the top mirror is a thin-layer grating providing reflectivity higher than 99%. With grating periods varying from 450 to 490 nm, different designs with FWHM of about 0.2∼3 nm are attained. A broadband HCG as top reflector can result in significantly improved manufacturing cost, as well as near unity quantum efficiency (QE). A resonator HCG can result in a new splitting responsivity spectrum with on-off ratio of 14 dB, which has the potential to serve as the basic elements of ternary system, polarization dichroism or diattenuation, and optical switch.

The essential role of CYP2E1 in metabolism and hepatotoxicity of N,N-dimethylformamide using a novel Cyp2e1 knockout mouse model and a population study.

N,N-Dimethylformamide (DMF) is a widespread contaminant of leather factories and their surrounding environment. There is a lack of direct in vivo evidence supporting CYP2E1 as a primary enzyme responsible for DMF metabolism and hepatotoxicity. In this study, a novel Cyp2e1 knockout (KO) mouse model was generated and used to assess whether DMF metabolism and hepatotoxicity is CYP2E1 dependent using an acute toxicity protocol with a single dose of 1500 mg DMF/kg. An epidemiological study in 698 DMF-exposed workers and 188 non-DMF-exposed controls was conducted to investigate the associations between functional polymorphisms of CYP2E1 (rs6413432/rs2031920) and DMF metabolite (N-methylcarbmoylated-hemoglobin [NMHb]). We successfully established Cyp2e1 KO mice with evidence from DNA sequence analysis, which showed 1-bp insertion at 65 bp (C) site of Cyp2e1 Exon 1. In addition, western blot and in vivo pharmacokinetic study also showed a complete absence of CYP2E1 protein and a 92% and 88% reduction in CYP2E1 activity among males and females, respectively. DMF metabolism as evidenced by increased blood NMHb, and hepatotoxicity as evidenced by elevated liver/body weight ratio, activity of liver enzymes and massive liver necrosis were detected in wild-type (WT) mice but were completely abrogated in KO mice, strongly supporting a CYP2E1-dependent pattern of DMF metabolism and hepatotoxicity. Moreover, variant allele of CYP2E1-rs6413432 was also significantly associated with higher NMHb levels in DMF-exposed workers (P = 0.045). The increase of glucose-regulated protein 94 detected in WT mice but not in KO mice suggested CYP2E1-dependent endoplasmic reticulum stress may be a key mechanism underlying DMF-induced hepatotoxicity.

[Effects of N, N-dimethylformamide on hepatic antioxidant capacity and liver PPARs mRNA levels in rats].

OBJECTIVE: To investigate the effects of N, N-dimethylformamide(DMF)exposure on liver anti-oxidative capacity and peroxisome proliferator activated receptor(PPAR)αand PPARγin rats. METHODS: A total of 30 male SD rats were randomly divided into 6 groups and orally administered with DMF 150 mg/kg body weight. Blood and liver tissues were collected on day 0(before DMF exposure), 1, 3, 7, 14 and 28 after DMF exposure. Blood were collected for blood routine examination and liver tissues for H&E staining. Glutathione peroxidase(GSH-Px)and catalase(CAT)were detected by kits, the mRNA levels of PPARαand PPARγwere detected by real-time PCR, and proinflammatory cytokines[interleukin-1 beta(IL-1ß), interleukin-6(IL-6)and tumor necrosis factor-alpha(TNF-α)]were detected by ELISA kits. RESULTS: Compared with day 0(control group), white blood cell(WBC)level in blood was significantly increased after 1 day exposure[(8. 30±0. 61)×10~9/L vs. (12. 64±1. 02)×10~9/L, P<0. 05]. As exposure time increases, WBC levels were increasing. In addition, DMF causes serious liver damage, including cell swelling, lymphocyte infiltration, and punctuate necrosis. GSH-Px was significantly increased on the first day after DMF exposure[(1006. 00±168. 60)U vs. (1437. 00±321. 00)U, P<0. 05]. However, after DMF exposure, the CAT levels increased significantly on day 28[(35. 17±4. 90)U/mg vs. (51. 80±10. 32)U/mg, P<0. 05]. Compared with day 0, the mRNA levels of PPARαand PPARγwere significantly increased on day 7 after DMF exposure(1. 35±1. 30 vs. 35. 70±10. 88, 1. 04±0. 33 vs. 191. 10±44. 70, P<0. 01). IL-1ß, IL-6 and TNF-αdecreased after DMF exposure, in which IL-1ß significantly decreased on day 28 after DMF exposure when compared with day 0[(34. 75±5. 94)pg/mL vs. (25. 52±1. 65)pg/mL, P<0. 05]. IL-6 decreased continuously after DMF exposure and the lowest value on day 14 after DMF exposure[(139. 10±23. 10)pg/mL vs. (97. 86±4. 15)pg/mL, P<0. 01], and TNF-αalso continuously decreased after DMF exposure, and decreased on the bottom value on day 28 after DMF exposure[(295. 40±29. 31)pg/mL vs. (217. 10±7. 43)pg/mL, P<0. 01]. CONCLUSION: A large amount ROS was produced during DMF metabolized by CYP2E1, which can cause oxidative stress and lead to inflammation. Therefore, it negative feedback up-regulates the transcription levels of PPARs and inhibits the proinflammatory cytokines secretions so as to reduce the inflammatory reaction.

A Comparative Benchmark Dose Study for N, N-Dimethylformamide Induced Liver Injury in a Chinese Occupational Cohort.

Widespread contamination of N,N-dimethylformamide (DMF) has been identified in the environment of leather industries and their surrounding residential areas. Few studies have assessed the dose-response relationships between internal exposure biomarkers and liver injury in DMF exposed populations. We assessed urinary N-methylformamide (NMF) and N-acetyl-S-(N-methylcarbamoyl) cysteine (AMCC) and blood N-methylcarbmoylated hemoglobin (NMHb) levels in 698 Chinese DMF-exposed workers and 188 nonDMF- exposed workers using ultraperformance liquid-chromatography tandem mass-spectrometry. Liver injury was defined as having abnormal serum activities of any of the 3 liver enzymes, including alanine aminotransferase, aspartate aminotransferase, and γ-glutamyl transpeptidase. Higher liver injury rates were identified in DMF-exposed workers versus nonDMF-exposed workers (9.17% vs 4.26%, P = .029) and in male versus female workers (11.4% vs 3.2%, P < .001). Positive correlations between environmental exposure categories and internal biomarker levels were identified with all 3 biomarkers undetectable in nonDMF-exposed workers. Lower confidence limit of benchmark dose (BMDL) was estimated using the benchmark dose (BMD) method. Within all study subjects, BMDLs of 14.0 mg/l for NMF, 155 mg/l for AMCC, and 93.3 nmol/g for NMHb were estimated based on dose-response relationships between internal levels and liver injury rates. Among male workers, BMDLs of 10.9 mg/l for NMF, 119 mg/l for AMCC, and 97.0 nmol/g for NMHb were estimated. In conclusion, NMF, AMCC, and NMHb are specific and reliable biomarkers and correlate well with DMF-induced hepatotoxicity. NMF correlates the best with liver injury, while NMHb may be the most stable indicator. Males have a greater risk of liver injury than females upon DMF exposure.

Alteration of gut microbial community after N,N-Dimethylformamide exposure.

N,N-Dimethylformamide (DMF), a solvent commonly used in factories, can induce liver toxicities, including hepatitis, fibrosis, cirrhosis and hepatoma. It is well known that the gut microbial community plays a role in the metabolism of many toxic substance and in liver regeneration. However, the effect of DMF on rat gut microbial community is poorly understood. The gut microbiotas in control rats and rats exposed to DMF were characterized by high-throughput sequencing of the bacterial 16S rRNA gene. The levels of biochemical parameters in the serum of rats, including cholesterol, bile acid, alanine aminotransferase (ALT), and aspartate aminotransferase (AST), were evaluated. The weight was lower in the DMF exposure group than in the control group. DMF exposure led to changes in gut microbiotas that were reflected in a decreased abundance of Prevotellaceae, Lactobacillaceae, and increased abundance of S24-7, Baceroidaceae, Rikenellaceae and Peptostreptococcaceae. Compared with control group, the cholesterol level was substantially reduced in the DMF exposure group (p < 0.05), while the concentration of bile acid was significantly increased in the DMF exposure group (p < 0.05). The present data established that the gut microbiotasy were changed after DMF exposure, and it revealed the relationship between DMF and gut microbiotas for the first time.