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1.
J Colloid Interface Sci ; 581(Pt B): 576-585, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32814185

RESUMO

Enhancing the dispersibility and conductivity is an effective solution to develop the application zeolitic imidazole frameworks (ZIF) in the electrochemical field. This work thus employs a novel reaction-diffusion framework (RDF) technique for the in situ growth of ZIF-8 crystals on graphene oxide (GO@ZIF-8) matrixes. In detail, the outer electrolyte of 2-methyl imidazole naturally diffuses into the inner agar gel matrix containing Zn2+ cations and GO nanosheets. The long reaction-diffusion makes the growth of ZIF-8 crystals controllable in a vertical gradient. After thermal treatment, the title product of ZIF-8 in situ grown on reduced graphene oxide (rGO@ZIF-8) is obtained and thus exhibits good dispersibility, high conductivity, large surface area, and more catalytic sites. The glassy carbon electrode (GCE) was modified by casting the rGO@ZIF-8 suspension. The obtained rGO@ZIF-8/GCE displays excellent catalytic activity toward naphthol (NAP) isomers. Under the optimal conditions, the amperometric currents of 1-NAP and 2-NAP demonstrate the good linear relationship in wide ranges of 0.05-12 µM and 0.02-15 µM, respectively. Their limits of detection are as low as 15 and 17 nM, respectively. The fabricated modified electrode exhibits excellent selectivity, stability, and reproducibility. The sensor is also utilized to detect NAP molecules in real water samples and indicates good accuracy and reliability.

2.
Biosens Bioelectron ; 171: 112713, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33059166

RESUMO

Procalcitonin (PCT) as a disease marker is of great significance in the early diagnosis of septicemia and pyemia. Biosensor have good prospects for analysis and detection of disease markers, but developing highly sensitive detection methods for detecting PCT remains a daunting task. In this paper, we develop a ratiometric electrochemical immunosensor with Au NPs modified SiO2-Fc-COOH complex as matrix and UiO-66 loaded with Toluidine blue (TB) as a marker for quantitative detection of procalcitonin (PCT). The SiO2 modified by APTES not only has a large specific surface area but also contains abundant amino groups, which can be connected to the electrochemical probe of ferrocenecarboxylic acid (Fc-COOH). UiO-66 has the advantages of large specific surface area, high porosity and adjustable structure, which can adsorb toluidine blue electrochemical probe through electrostatic attraction. Measurement and analysis of the prepared immunosensor by Differential Pulse Voltammetry (DPV) show that the oxidation peak currents of Fc-COOH and TB appear at potentials of 0.30 V and -0.30 V respectively. As the PCT concentration increases, the oxidation peak current of TB increases and the oxidation peak current of Fc-COOH decreases. The ratios (ΔI=ΔITB/ΔIFc-COOH) between the double signals could show a certain linear relationship with the concentration of the PCT within a certain range. Under optimal conditions, the linear range of detection obtained by the immunosensor was 1 pg/mL-100 ng/mL and the detection limit was 0.3 pg/mL. In this work, the developed ratiometric electrochemical immunosensor not only provides a simple, reliable and sensitive strategy for quantitative detection of PCT but also provides a useful method for clinical detection of other disease markers.

3.
Food Chem ; 337: 127774, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-32777570

RESUMO

Apis cerana honey collected from the Qinling Mountains in China has been widely used for its antimicrobial property in traditional Chinese medicine. However, its antibacterial mechanism against Salmonella Typhimurium LT2 is still uncertain. A total of 52 volatile components were identified using headspace-gas-chromatography-ion-mobility, and Qinling A. cerana honey exhibited more abundant aromas than monofloral honeys. The phenolic extracts of honey sample F exhibited the lowest minimum inhibitory concentration (5 mg/mL), and chlorogenic acid exhibited the highest (155.91 ± 0.79 mg/kg), followed by caffeic acid, and rutin. After being treated with the extract, cell membranes of S. Typhimurium LT2 significantly shrunk and further collapsed. The extract treatment on mice caused a significant decrease in S. Typhimurium LT2, and a dramatic increase in the potential prebiotic Lactobacillus in both the caecum and colon. The results demonstrate that the Qinling A. cerana honey extract could effectively inhibit S. Typhimurium in vitro and in vivo.


Assuntos
Anti-Infecciosos/farmacologia , Mel/análise , Salmonella typhimurium/efeitos dos fármacos , Salmonella typhimurium/patogenicidade , Compostos Orgânicos Voláteis/química , Animais , Anti-Infecciosos/química , Anti-Infecciosos/uso terapêutico , Abelhas , Modelos Animais de Doenças , Cromatografia Gasosa-Espectrometria de Massas , Camundongos , Testes de Sensibilidade Microbiana , Fenóis/química , Infecções por Salmonella/tratamento farmacológico , Compostos Orgânicos Voláteis/farmacologia , Compostos Orgânicos Voláteis/uso terapêutico
4.
Artigo em Inglês | MEDLINE | ID: mdl-33170611

RESUMO

N-doped carbon materials are well known as promising metal-free catalysts and applied in innumerable industrial synthetics. However, most of the N-doped carbon materials obtained by conventional synthetic means exhibit generally low mesoporosity, and their reported pore volumes reached only 1-3 cm3 g-1, which greatly limits their further industrial application in heterogeneous catalysis. Especially for oxidation reaction of alkylbenzenes, this type of reaction is almost always accompanied by many different byproducts, while the reaction activity and selectivity are mainly affected by mesoporosity of catalysts. Traditionally, graphitic carbon nitride (GCN) is commonly considered as a self-sacrificed nitrogen source together with multifarious organic compounds to obtain N-doped carbon materials by a co-pyrolysis process. However, the mechanisms of formation process are still complex and uncontrollable to date. In this work, we present a novel co-pyrolysis synthetic strategy by a facile chemical vapor deposition method for preparing a series of ultrathin N-doped carbon nanosheets with high mesoporosity. More importantly, it is found that GCN containing abundant hydrogen bonds can be irreversibly anchored by carbonaceous gas fragments (CxHy+) released from various organic substances via thermogravimetry-differential thermal analysis coupled with mass spectrometry and X-ray photoelectron spectroscopy analysis, and the CxHy+ fragments exhibit a non-negligible role during the transformation. Our results further demonstrated that the residue of incompletely decomposed GCN is a key point to enlarge porosity in final products which are obtained via mixing pyrolysis between an organic precursor and GCN (or GCN precursors). Benefitting from the outstanding mesoporosity and ultrathin morphology, the representative ABCNS-900 exhibits excellent catalytic performance for oxidizing ethylbenzene to acetophenone with extremely low dosage and high selectivity. Our findings show a universal synthetic strategy for ultrathin N-rich carbon nanosheets with a high mesopore volume, further promoting the application of N-doped carbon materials in heterogeneous catalytic industry.

5.
Artigo em Inglês | MEDLINE | ID: mdl-33220950

RESUMO

The development of recyclable photocatalysts with broad-spectral photoresponse has drawn much attention for the practical application in flowing wastewater treatment. Herein, we have reported the construction of BiOBr/Ag/AgBr junctions on carbon fiber cloth (CFC) as broad-spectral-response filter-membrane-shaped photocatalyst that is efficient and easily recyclable. With CFC as the substrate, BiOBr nanosheets (diameter: 0.5-1 µm) were firstly synthesized by a hydrothermal method, and then Ag/AgBr nanoparticles (size: 100-300 nm) were prepared on the surface of CFC/BiOBr by using a chemical bath deposition route. CFC/BiOBr/Ag/AgBr presents superior flexibility and wide UV-Vis-NIR photoabsorption (from 200 to 1000 nm). Under visible light irradiation, CFC/BiOBr/Ag/AgBr (area: 4 × 4 cm2) can remove 99.8% rhodamine B (RhB), 99.0% acid orange 7 (AO7), and 93.0% tetracycline (TC) after 120 min, better than CFC/BiOBr (95.4% RhB, 55.0% AO7 and 91.2% TC). Interestingly, when CFC/BiOBr/Ag/AgBr is served as a filter-membrane in a photoreactor to purify the flowing sewage (RhB, rate: ~1.5 L h-1), the degradation rate of RhB goes up to 90.0% after ten filtering grades. Therefore, CFC/BiOBr/Ag/AgBr has great potential to purify the flowing wastewater as a novel filter-membrane-shaped photocatalyst.

6.
Chemosphere ; : 128960, 2020 Nov 13.
Artigo em Inglês | MEDLINE | ID: mdl-33223209

RESUMO

Here, the bio-nanocomposite (n-HFP + n-HFS)@An was developed to simultaneously immobilize Pb, Cd and As in the severely contaminated soil. The immobilization rates of diethylenetriaminepentaacetic acid (DTPA)/decarbonate-extracted bioavailable Pb, Cd and As were 59.87%, 31.28% and 62.30%, and the immobilization rates of their water-soluble forms were 63.12%, 60.02% and 89.39%, respectively. Moreover, the ten-year acid rain simulated leaching assay showed that the maximum cumulative release contents of Pb, Cd and As in the treated soil samples were decreased by 2.94, 2.46 and 40.60 times, comparing to the un-treated ones. Additionally, the results of SBRC (Solubility Bioaccessibility Research Consortium) revealed that the bioaccessible rates of the three metals in intestinal phase were lower than in gastric phase, and both of them decreased with increasing the immobilization time. The gastric bioaccessibility of Pb, Cd and As had a higher correlation with the contents of water-soluble forms, while the intestinal bioaccessibility was more strongly positively associated with the bioavailable forms.

7.
Molecules ; 25(21)2020 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-33182368

RESUMO

False indigo (Amorpha fruticosa L., A. fruticosa) is the preferred tree indigenous for windbreak and sand control in Northwest China, while information on nutritional and bioactive characteristics of its honey is rare. Herein, 12 honey of Amorpha fruticosa L. (AFH) were sampled in Northwest China and the nutritional composition was determined. Sixteen mineral element and ten dominant polyphenols content were identified and quantified by ICP-MS (Inductively coupled plasma mass spectrometry) and HPLC-QTOF-MS (High performance liquid chromatography-Quadrupole time-of-flight mass spectrometry), respectively. Moreover, AFH demonstrated high levels of DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging activity (IC50 100.41 ± 15.35 mg/mL), ferric reducing antioxidant power (2.04 ± 0.29 µmol FeSO4·7H2O/g), and ferrous ion-chelating activity (82.56 ± 16.01 mg Na2EDTA/kg), which were significantly associated with total phenolic contents (270.07 ± 27.15 mg GA/kg) and ascorbic acid contents (213.69 ± 27.87 mg/kg). The cell model verified that AFH exhibited dose-dependent preventive effects on pBR322 plasmid DNA and mouse lymphocyte DNA damage in response to oxidative stress. Taken together, our findings provide evidence for the future application of AFH as a potential antioxidant dietary in food industry.

8.
Nanoscale ; 2020 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-33211053

RESUMO

Though solar energy availability is predicted for centuries, the diurnal and asymmetrical nature of the sun across the globe presents significant challenges in terms of harvesting sunlight. Photo/electro-catalysis, currently believed to be the bottleneck, promises a potential solution to these challenges along with a green and sustainable environment. This review aims to provide the current highlights on the application of inorganic-semiconductor-based ternary nanocomposites for H2 production and pollutant removal. Various engineering strategies employing integration of 2D materials, 1D nanorods, and/or 0D nanoparticles with inorganic semiconductors to create multiple nano-junctions have been developed for the excellent photocatalytic activity. Following a succinct description of the latest progress in photocatalysts, a discussion on the importance of ternary electrocatalysts in the field of next-generation supercapacitors has been included. Finally, the authors' perspectives are considered briefly, including future developments and critical technical challenges in the ever-growing field of photo/electro-catalysis.

9.
Sensors (Basel) ; 20(22)2020 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-33228068

RESUMO

Feature point detection is the basis of computer vision, and the detection methods with geometric invariance and illumination invariance are the key and difficult problem in the field of feature detection. This paper proposes an illumination-invariant feature point detection method based on neighborhood information. The method can be summarized into two steps. Firstly, the feature points are divided into eight types according to the number of connected neighbors. Secondly, each type of feature points is classified again according to the position distribution of neighboring pixels. The theoretical deduction proves that the proposed method has lower computational complexity than other methods. The experimental results indicate that, when the photometric variation of the two images is very large, the feature-based detection methods are usually inferior, while the learning-based detection methods performs better. However, our method performs better than the learning-based detection method in terms of the number of feature points, the number of matching points, and the repeatability rate stability. The experimental results demonstrate that the proposed method has the best illumination robustness among state-of-the-art feature detection methods.

10.
Cell Rep ; 33(6): 108369, 2020 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-33176141

RESUMO

Nerve injury in somatosensory pathways may lead to neuropathic pain, which affects the life quality of ∼8% of people. Long-term enhancement of excitatory synaptic transmission along somatosensory pathways contributes to neuropathic pain. Caspase 3 (Casp3) plays a non-apoptotic role in the hippocampus and regulates internalization of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) subunits. Whether Casp3-AMPAR interaction is involved in the maintenance of peripheral hypersensitivity after nerve injury remained unknown. Here, we show that nerve injury suppresses long-term depression (LTD) and downregulates Casp3 in the anterior cingulate cortex (ACC). Interfering with interactions between Casp3 and AMPAR subunits or reducing Casp3 activity in the ACC suppresses LTD induction and causes peripheral hypersensitivity. Overexpression of Casp3 restores LTD and reduces peripheral hypersensitivity after nerve injury. We reveal how Casp3 is involved in the maintenance of peripheral hypersensitivity. Our findings suggest that restoration of LTD via Casp3 provides a therapeutic strategy for neuropathic pain management.

11.
Clin Cancer Res ; 2020 Nov 24.
Artigo em Inglês | MEDLINE | ID: mdl-33234511

RESUMO

Purpose:Although chimeric antigen receptor T cell (CAR-T) therapy development for B cell malignancies has made significant progress in the last decade, broadening the success to treating T-ALL has been limited. We conducted two clinical trials to verify the safety and efficacy of GC027, an "off-the-shelf" allogeneic CAR-T product targeting T cell antigen CD7. Here we report two patients as case reports with relapsed/refractory T-ALL who were treated with GC027. Experimental Design:Both of the two trials reported are open-labeled and single-arm. A single infusion of GC027 was given to each patient after preconditioning therapy. Result:Robust expansion of CAR-T cells along with rapid eradication of CD7+ T-lymphoblasts were observed in the peripheral blood, bone marrow and cerebrospinal fluid. Both patients achieved complete remission (CR) with no minimal residual disease (MRD) detectable. At data cut off Sep.30, 2020 one of the two patients remains in ongoing remission for over one year after CAR-T cell infusion. Grade 3 cytokine release syndrome (CRS) occurred in both patients and was managed by a novel approach with a ruxolitinib-based CRS management. Ruxolitinib showed promising activity in a preclinical study conducted at our center. No Graft-versus-host-disease (GvHD) was observed. Conclusion:The two case reports demonstrate that a stand alone therapy with this novel CD7 targeted "off-the-shelf" allogeneic CAR-T therapy may provide deep and durable responses in select r/r T-ALL patients. GC027- might have a potential to be a promising new approach for treating refractory/relapsed T - ALL. Further studies are warranted.

12.
World Neurosurg ; 2020 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-33217592

RESUMO

The paper uses an optimized denoising algorithm, combined with spiral CT coronary angiography (CCTA) in conjunction with carotid ultrasound, serological markers relevance for the assessment of coronary artery disease was analysed early T2DM and coronary heart disease (CHD) in patients with coronary and carotid artery disease to provide diagnostic evidence. Papers selected from January 2017 to December 2019 in hospital diagnosed 95 patients CHD, CHD were divided into three groups (n = 45) and T2DM with CHD group (n depending on whether T2DM disease = 50), were compared coronary arteries, the degree of carotid lesions, high-sensitivity C- reactive protein (hsC-RP) and the difference of FFA. CCTA display, combined with CHD of T2DM in double-vessel coronary artery disease and three main right coronary artery, left circumflex artery plaques appear more CHD combined group of T2DM, and three double-vessel coronary disease carotid plaque compared with the number of single-vessel disease and more. Spearman correlation analysis showed, hsC-RP positively correlated with FFA, hsC-RP and coronary artery lesion count was positively correlated. CCTA display, T2DM with CHD in coronary plaque with soft plaque and mixed plaque mainly extensive coronary artery disease, carotid artery ultrasound prompted the more peripheral vascular plaque number, the more the number of diseased vessels, the more severe the disease. Joint CCTA Clinically, carotid ultrasound and hsC-RP, FFA level detection can improve the rate of diagnosis of T2DM with CHD, reduce false positives, should be widely applied.

13.
Artigo em Inglês | MEDLINE | ID: mdl-33105115

RESUMO

Oxide materials have shown promising thermoelectric applications due to their availability, tunability, and thermal stability. Among oxide materials, the layered tin oxides (SnO) attract raising attention in the electronic and optoelectronic field owing to their lone pair electrons. We have investigated the thermoelectric properties of layered SnO structures through first-principle calculations. SnO exhibits superior n-type thermoelectric properties and the metallicity of SnO becomes stronger with the number of layers increasing. The lone pair electrons around Sn atoms are the key factor to n-type properties and they will get bonded and anti-bonded in the case of interlayer interaction. Monolayer SnO exhibits the best thermoelectric performances and the average n-type ZT value of monolayer SnO can achieve 0.85 at 500~700K. Our results demonstrate that layered SnO will be the potential n-type two-dimensional oxide thermoelectric material.

14.
Org Lett ; 22(21): 8634-8637, 2020 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-33049136

RESUMO

Research on perfluoroalkyl ether carboxylic acids (PFECAs) as alternatives for perfluoroalkyl substances continues with the goal of protecting the environment. However, very little is known about the utilization of decomposition products of PFECAs. We report herein a new series of deoxyfluorination reagents featuring OCF2 functional groups derived from certain PFECAs. Alkyl fluorides were generated from various alcohols in ≤97% yield by these novel reagents. The mechanistic experiment verified in situ generation of carbonic difluoride (COF2).

15.
Int J Mol Med ; 46(6): 2115-2125, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33125101

RESUMO

Oral cancer (OC) is the most common type of head and neck malignant tumor. Tumor­derived exosomes induce a complex extracellular environment that affects tumor immunity. In the present study, exosomes were isolated from OC cell lines (WSU­HN4 and SCC­9) by ultrafiltration and the protein content of these oral cancer­derived exosomes (OCEXs) was analyzed by mass spectrometry, which revealed the enrichment of transforming growth factor (TGF)­ß1. Natural killer (NK) cells were examined by flow cytometry following co­culture with OCEXs. The expression of killer cell lectin like receptor K1 (KLRK1; also known as NKG2D, as used herein) and natural cytotoxicity triggering receptor 3 (NCR3; also known as NKp30, as used herein) in NK cells was found to be significantly upregulated following co­culture with the OCEXs for 1 day, whereas this expression decreased at 7 days. Killer cell lectin like receptor C1 (KLRC1; also known as NKG2A; as used herein) expression exhibited an opposite trend at 1 day. In addition, NK cell cytotoxicity against the OC cells was enhanced at 1 day, but was attenuated at 7 days. TGF­ß1 inhibited the function of NK cells at 7 days, whereas it had no obvious effects at 1 and 3 days. On the whole, the findings of the present study reveal changes in NK cell function and provide new insight into NK cell dysfunction.

16.
J Stroke Cerebrovasc Dis ; 29(12): 105400, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33096491

RESUMO

OBJECTIVE: The present study aimed to summarize the clinical characteristics, therapeutic effects, and long-term prognosis of cases confirmed with primary angiitis of the central nervous system (PACNS) by biopsy, analyze the risk factors, and provide clinical guidance for the diagnosis and treatment of the disease. METHODS: Retrospective analysis was performed on 28 cases of PACNS confirmed by biopsy, and the age, gender, pathological results, course of the disease, imaging manifestations, treatment, and prognosis of the patients were analyzed and summarized. RESULTS: The cohort (age 16-60 years) comprised of 16 males. The average time from the visit to diagnosis was 6 months. The first symptom was chronic headache in 18 patients. The pathological results were accompanied by demyelination in 10 cases and glial hyperplasia in 6 cases. A total of 27 patients received treatments including glucocorticoid+cyclophosphamide; of these, 3 cases of craniotomy were improved. Among the 28 patients, 15 patients improved after the treatment, 12 patients had no significant improvement, and 1 patient was deceased. Patients with a long course of the disease before diagnosis, a Karnofsky performance status (KPS) score <60 at the time of diagnosis, a behavioral, cognitive abnormality before treatment, and a short-term relapse (0.3-1 month) have a poor outcome. CONCLUSIONS: PACNS patients are prone to misdiagnosis and mistreatment, with unknown etiology and poor prognosis due to delayed treatment. Therefore, early biopsy, pathological diagnosis, and timely treatment with glucocorticoid shock are recommended, and patients with obvious mass effect should be treated by surgical resection.

17.
Zhongguo Gu Shang ; 33(10): 902-6, 2020 Oct 25.
Artigo em Chinês | MEDLINE | ID: mdl-33107250

RESUMO

OBJECTIVE: To explore clinical effects of micro external fixator for the treatment of supracondylar fracture of humerus in children. METHODS: From October 2017 to December 2018, 20 children with supracondylar fracture of humerus (treatment group) were admitted and treated with micro-external fixation after closed reduction, including 14 males and 6 females, aged from 6 to 14 years old with an average of (7.9±2.4) years old, classified to Gartland Ⅲ. Thirty nine children with supracondylar fracture of humerus were admitted as control group from January 2015 to September 2017, and treated with closed reduction Kirschner wire fixation. Among them, including 24 males and 15 females, aged from 6 to 14 years old with an average of (8.1±1.9) years old, classified to GartlandⅢ. Operation time, times of intraoperative fluoroscopy, and complications between two groups were observed and compared, Mayo scoring system at the latest follow up was used to evaluate clinical effect. RESULTS: Twenty children in treatment group were followed up from 6 to 12 months with an average of (8.0±2.5) months, operation time was(30.10±12.50) min, times of intraoperative fluoroscopy was(10.00±2.50). Fifteen patients got excellent results, 3 good, 2 fair according to Mayo elbow joint scoring. No ulnar nerve injury moderate or severe elbow varus occurred in treatment group. Thirty-nine children in control group were followed up from 5 to 13 months with an average of (9.0±3.1) months, operation time was(45.60±18.90) min, times of intraoperative fluoroscopy was(19.00±5.60). Twenty-three patients got excellent results, 12 good, 3 fair and 1 poor according to Mayo elbow joint scoring. One child occurred ulnar nerve injury and recovered at the final follow-up, 1 child occurred severe cubitus varus and 2 children occurred moderate cubitus varus. There was no statistical difference in clinical effect between two groups (P>0.05). Occurrence rate of moderate and server cubitus varus, operation time and times of intraoperative fluoroscopy in treatment group were better than that of control group(P<0.05). CONCLUSION: Treated with closedreduction and mini external fixator fixed on children humerus condyle fracture could receive the same clinical result as closed as reduction gram needle fixation, which has advantages of shorter operation time, less times of intraoperative fluoroscopy, not esay to damage ulnar nerve during operation, less incidence of moderate and severe cubitus varus deformity after operation, and the permeation was simple.


Assuntos
Fixação Interna de Fraturas , Fraturas do Úmero , Adolescente , Estudos de Casos e Controles , Criança , Pré-Escolar , Fixadores Externos , Feminino , Humanos , Fraturas do Úmero/cirurgia , Úmero , Masculino
18.
Mol Oral Microbiol ; 2020 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-33000897

RESUMO

Fluoride has been used as an effective anticaries agent for more than 70 years, which might result in the emergence of fluoride-resistant strains. However, the fluoride resistance mechanism and the cariogenic properties of fluoride-resistant mutant for cariogenic bacterial species Streptococcus mutans remain largely unknown. We describe here the construction and characterization of a mariner-based transposon system designed to be used in S. mutans, which is also potentially applicable to other streptococci. To identify genetic determinants of fluoride resistance in S. mutans, we constructed a library of S. mutans transposon insertion mutants and screened this library to identify mutants exhibiting fluoride resistance phenotype. Two mutants were found to carry transposon insertion in two different genetic loci (smu.396 and smu.1291c), respectively. Our subsequent genetic study indicates the fluoride-resistant phenotype for the mutant with the insertion in smu.1291c is resulting from the constitutive overexpression of downstream operon smu.1290c-89c, which is consistent with the previous reports. We also demonstrate for the first time that the deletion of smu.396 is responsible for the fluoride-resistant phenotype and that the combining of smu1290c-89c overexpression and smu.396 deletion in one strain could attribute an additive effect on the fluoride resistance. In addition, our results suggest that the biological fitness of those fluoride-resistant mutants is reduced compared to that of wild-type strain. Overall, our identification and characterization of genetic determinants responsible for fluoride resistance in S. mutans expand our understanding of the fluoride resistance mechanism and the biological consequence of the fluoride resistance strains.

19.
Appl Microbiol Biotechnol ; 104(22): 9773-9783, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32997202

RESUMO

Modification of C4-dicarboxylate transport processes is an important strategy for the development of efficient malic acid producing cell factory in Aspergillus niger. However, there is a lack of identification and functional research of malic acid transport proteins, which seriously hinders the construction of high-yield malic acid metabolic engineering strains. A C4-dicarboxylate transport protein (DCT) DCT1 is identified as major malic acid transport protein and exhibits significant elevation in malic acid production when overexpressed. DCT1 is found by homology searches and domain analyses with SpMAE1 from Schizosaccharomyces pombe as the template. Phylogenetic and domain analyses show that DCTs belong to voltage-dependent slow-anion channel transporter (SLAC1) family and are members of Tellurite-resistance/Dicarboxylate Transporter (TDT) Family. DCT1 disruption dramatically decreases malic acid titer by about 85.6% and 96.2% at 3 days and 5 days compared with the parent strain, respectively. Meanwhile, the citric acid titers increase by 36.4% and 13.7% at 3 days and 5 days upon DCT1 deficiency. These results suggest that DCT1 is the major malic acid transporter in A. niger. Overexpression of dct1 with its native promoter significantly improves malic acid production yielding up to 13.86 g/L and 30.79 g/L at 3 days and 5 days, respectively, which is 36.8% and 22.8% higher than those in the parent strain. However, the citric acid has no significant change during the 5-day fermentation. These results demonstrate the importance of C4-dicarboxylate transporters for the efficient production of malic acid. Furthermore, enhancement of malic acid transport process is a feasible approach of efficient malic acid production in this citric acid producing A. niger strain. KEY POINTS: • A dicarboxylate transporter DCT1 is identified as a major malic acid transporter. • DCT1 deficiency results in significant decrease of malic acid. • DCT1 overexpression leads to increased titers of malic acid. • Enhancement of malic acid transport is vital for malic acid production in A. niger.

20.
Emerg Microbes Infect ; 9(1): 2315-2321, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32981485

RESUMO

Prolonged presence of viral nucleic acid was reported in certain patients with coronavirus disease 2019 (COVID-19), with unclear clinical and epidemiological significance. We here described the clinical and epidemiological characteristics of 37 recovered COVID-19 patients with prolonged presence of viral RNA in Wuhan, China. For those who had been discharged and re-admitted, their close contacts outside the hospital were traced and evaluated. The median age of the 37 patients was 62 years (IQR 50, 68), and 24 (64.9%) were men. They had common or severe COVID-19. With prolonged positive RT-PCR, most patients were clinically stable, 29 (78.4%) denied any symptoms. A total of 431 PCR tests were carried out, with each patient at a median of 8 time points. The median time of PCR positivity to April 18 was 78 days (IQR 67.7, 84.5), and the longest 120 days. 22 of 37 patients had been discharged at a median of 44 days (IQR 22.3, 50) from disease onset, and 9 had lived with their families without personal protections for a total of 258 person-days and no secondary infection was identified through epidemiological investigation, nucleic acid and antibody screening. Infectiousness in COVID-19 patients with prolonged presence of viral nucleic acid should not solely be evaluated by RT-PCR. Those patients who have clinically recovered and whose disease course has exceeded four weeks were associated with very limited infectiousness. Reconsideration of disease control in such patients is needed.


Assuntos
Betacoronavirus/fisiologia , Infecções por Coronavirus/virologia , Pneumonia Viral/virologia , RNA Viral/genética , Idoso , Betacoronavirus/genética , China/epidemiologia , Infecções por Coronavirus/epidemiologia , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Pandemias , Pneumonia Viral/epidemiologia , Reação em Cadeia da Polimerase , RNA Viral/metabolismo
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