Effects of lead pollution on bacterial communities in biofilm attached to submerged plants.

Submerged plants and biofilms have significant advantages in hydro-ecology rehabilitation, but their tolerance and physiological responses to heavy metal stress have thus far been under-investigated. This study investigated the influence of lead on physiological and biochemical responses, as well as variation in bacterial communities and functional characteristics of submerged plant biofilms. The results showed that chlorophyll a content of two submerged plants decreased with increased lead concentration. The concentration of malondialdehyde of both submerged plants was higher under high lead concentrations than under low lead concentrations, and the concentrations of malondialdehyde and hydrogen peroxide in Vallisneria natans were more stable. The antioxidant enzyme systems of the two plants played protective roles against lead stress. High lead concentration can inhibit the bacterial community and lead to decreased diversity. The most abundant bacterial phyla were Proteobacteria (40.9%), Cyanobacteria (21.5%), and Bacteroidetes (14.3%). Proteobacteria abundance decreased with increased lead concentration, while Cyanobacteria abundance increased. The lead concentration in plants (19.7%, P < 0.01) and the lead concentration in aquatic environment (17.7%, P < 0.01) were significantly correlated with variation in bacterial communities. High lead concentration inhibits the activity of these bacteria related to the conversion of nitrogen and sulfur.

Influence of margin design and restorative material on the stress distribution of endocrowns: a 3D finite element analysis.

BACKGROUND: This study aimed to evaluate the stress distributions in endocrown restorations as applied to endodontically treated teeth (ETT), according to the factors of "margin design" (four levels) and "restorative material" (six levels). METHODS: Four 3D-finite elements models were constructed for endocrown restored molars considering different margin designs. Model A was prepared with a flat butt joint margin and received an endocrown with a 2.0-mm occlusal thickness. Model B was prepared with a 20° bevel margin and received an endocrown with a 2.0-mm occlusal thickness. Model C was prepared with an axial reduction and 1-mm shoulder margin and received an endocrown with a 2.0-mm occlusal thickness. Model D was prepared with an anatomic margin and received an endocrown with a 2.0-mm occlusal thickness. The following endocrown materials were used: In-Ceram Zirconia (Zr), Vita Suprinity (VS), IPS Empress (IE), Grandio blocs (GR), VisCalor bulk (VS), and CopraPeek Light (CP). The Load application (600 N) was performed at the food bolus and tooth surface during the closing phase of the chewing cycle. The results for the endocrown and tooth remnants were determined according to the von Mises stress. The failure risk of the cement layer was also calculated based on the normal stress criterion. RESULTS: Model D (with an anatomic margin) showed the greatest stress concentrations, especially in the irregular and sharp angles of the restoration and tooth remnants. The stress concentrated on the dentin was significantly lower in Model B with a 20° bevel margin (20.86 MPa), i.e., 1.3 times lower than the other three margin designs (27.80 MPa). Restorative materials with higher elastic moduli present higher stress concentrations inside the endocrown and transmit less stress to the cement layer, resulting in lower bonding failure risks. In contrast, materials with an elastic modulus similar to that of dentin presented with a more homogeneous stress distribution on the whole structure. CONCLUSIONS: An endocrown with a 20° bevel margin design could be a favorable preparation option for ETT. Composite resins (GR and VC) exhibit a more even stress distribution, and seem to be more promising materials for endocrown molars.

Optimal cuspal coverage of ceramic restorations using CAD/CAM: Biomechanical characteristic analysis by 3D finite element analysis and in vitro investigation.

AIM: The present in vitro study aimed to evaluate the stress distribution patterns, resistance to fracture, and failure modes of endodontically treated molars restored with different cuspal coverage options. MATERIALS AND METHODS: Three-dimensional models of mandibular first molars with six kinds of typical cuspal coverage were generated: T1: mesiobuccal cuspal coverage; T2: coverage of all buccal cusps; T3: mesiolingual cuspal coverage; T4: coverage of all lingual cusps; T5: mesiobuccal and mesiolingual cuspal coverage; T6: coverage of all cusps. All restorations were fabricated with zirconia-reinforced lithium silicate ceramic. The stress and its distributions under axial and oblique loading were analyzed by finite element analysis (FEA). Sixty human mandibular molar samples were randomly allocated into six groups (n = 10) to simulate the application of six types of restorations with different cuspal coverage, as in the FEA analysis, and were then subjected to a compressive test. All fractured specimens were subjected to fractography. Data were analyzed by one-way analysis of variance (ANOVA), the Tukey post hoc test, and the Fisher exact test (α = 0.05). RESULTS: The T2 and T6 groups presented superior stress distribution patterns under both axial and oblique loading compared with the other models. The fracture loads in the T2 (1627 ± 358 N) and T6 (1639 ± 355 N) groups were significantly higher than those in the other groups (P < 0.05). The T2 and T6 groups exhibited more restorable failure modes. Fractography showed more cracks below the cementoenamel junction in the T3, T4, and T5 groups. CONCLUSIONS: Onlay restorations with whole functional cuspal coverage provided comparable effects to coverage of all cusps in endodontically treated molars, and both methods exhibited a more even stress distribution and fracture resistance and better mechanical performance in high occlusal areas than other types of cuspal coverage. (Int J Comput Dent 2022;25(3):267-276; doi: 10.3290/j.ijcd.b2599709).

Multi-Feature Intelligent Oral English Error Correction Based on Few-Shot Learning Technology.

The computer-aided language teaching system is maturing thanks to the advancement of few-shot learning technologies. In order to support teachers and increase students' learning efficiency, more computer-aided language teaching systems are being used in teaching and examinations. This study focuses on a multifeature fusion-based evaluation method for oral English learning, completely evaluating specific grammar, and assisting oral learners in improving their oral pronunciation skills. This study proposes an improved method based on HMM a posteriori probability scoring, in which the only standard reference model is no longer used as the basis for scoring and error determination, and instead, the average level of standard pronunciation in the entire corpus is introduced as another judgment basis, based on a preliminary study of speech recognition technology, scoring methods, and relevant theoretical knowledge of information feedback. This strategy can reduce the score limitation caused by standard pronunciation personal differences, lower the system's misjudgment rate in detecting pronunciation errors, and improve the usefulness of error correction information. An expert opinion database has been created based on the most prevalent forms of spoken pronunciation problems, which can successfully assist learners improve their spoken English level by combining the database's corrected information. Finally, this study proposes an artificial scoring system for spoken English that performs activities such as identification, scoring, error judgment, and correction opinion feedback, among others. Finally, it has been demonstrated through trials and tests that adding the average pronunciation level to the system improves the system's scoring performance and has a certain effect on increasing users' oral pronunciation level.

Performance evaluation of CA242 by flow fluorescence assay.

ABSTRACT: Carbohydrate antigen 24-2 (CA24-2) is usually used as a biomarker for the diagnosis of pancreatic cancer and colorectal cancer. Currentlly, a new quantitative assay kit for CA242 by flow fluorometry assay (FFA) was developed by Shanghai Tellgen Cooperation Co. Ltd. China. Therefore, we conducted the performance evaluation for it.According to the "Guiding principles on performance analysis of diagnostic reagents in vitro" and "American association of clinical laboratory standardization guidelines EP15-A2", the accuracy, precision, linear range, reportable range, biological reference interval verification, carry-over contamination rate, anti-interference capability and cross reaction of the assay kit used in TESMI F3999-Luminex200 automatic immunoassay system were evaluated. In addition, the assay kit was performed in parallel to CanAg kit (CanAg Diagnostics Products Beijing Co., Ltd.) to analyze the correlation between the 2 kits.The bias of accuracy of the new assay kit was less than 12.5% and the coefficient of variations (CVs) of precision were all less than 10.0%. The linear range of CA242 concentration of the testing kit was between 3.46 U/ml and 434.76 U/ml and the reportable range was 6.00 to 535.13 U/ml. The CA242 reference interval 0.00 to 20.00 U/ml was suitable for use in laboratory. The carry-over contamination rate was -0.14%. Correlation analysis showed a satisfactory relevance and consistency (r = 0.982, P < .001) between the new assay kit and CanAg kit, with a regression equation Y = 1.0012X to 0.878 (R2 = 0.9647, P < .001). No statistically significant difference between serum samples without interferences and samples containing lipemia, bilirubin and hemoglobin. And no cross reaction existed between the assay kit and the other tumor markers, such as carbohydrate antigen 125 (CA125), alpha-fetoprotein (AFP), and cytokeratin-19 soluble fragment (CYFRA21-1).The new CA242 quantitative assay kit possesses good detection performance when it is used in TESMI F3999-Luminex200 automatic immunoassay system, which can be used for the examination of CA242 in clinical practice.

Effects of different habitats on the bacterial community composition in the water and sediments of Lake Taihu, China.

Bacterial communities are sensitive to environmental fluctuations, and a better understanding of the relationships between bacterial community distribution and complex environmental conditions is important for the remediation of lake ecosystems. In this study, bacterial communities from 7 water and 7 sediment samples in 3 different regions (east, the hydrophyte-dominated region; north, the transitional region; west, the highly polluted region) of Lake Taihu were investigated via high-throughput sequencing. The physicochemical characterization showed that there were obvious differences in the trophic statuses of the three lake regions, which were mainly due to the differences in pollutant concentration and hydrophyte coverage. The Shannon and Simpson values indicated that the diversity of bacterial communities in water was the highest in the eastern region, followed by the northern and western regions, while there was no significant difference in the bacterial community characteristics in sediments among lake regions. We found that the western lake region had the highest Cyanobacteria concentration (34.71%), suggesting that Cyanobacteria may have competitive advantages over the other bacterioplankton in water columns without plants. The abundances of Chlorobi detected in the water samples in the east (2.69%) and north (6.66%) were higher than those in the west because the high turbidity in the western lake region was unsuitable for the growth of Chlorobi. Nitrospirae (average 6.36%) and Chloroflexi (average 11.62%) were more common in the sediments than in the water of Lake Taihu, suggesting that the nutrient level of Lake Taihu sediment was higher than that of water bodies. Welch's t test revealed that there were significant differences in species abundance (such as Microcystis, Synechococcus, Flavobacterium, and hgcI_clade) among the different regions, except that the east was relatively similar to the north. Canonical correspondence analysis demonstrated that TN, TP, and DO showed significant effects on the relative abundance of the dominant bacterial genera in water, while TOC, TP, and TN were positively correlated with TOC, TP and TN. This study provides useful information for understanding the variation in the diversity of bacterial communities in different habitats of Lake Taihu.

Clinical efficacy of different marginal forms of endocrowns: study protocol for a randomized controlled trial.

BACKGROUND: After root canal treatment, most tooth defects need to be restored. Onlay restoration is widely used to restore dental defects. Endocrown is a new type of onlay; however, dentists have yet to obtain a full understanding of the clinical effects of marginal forms of endocrowns. Here, we present a multicenter protocol to compare the clinical efficacy of two marginal forms (flat and 90-degree shoulder) for tooth restoration. The efficacy will be evaluated by marginal fit, marginal discoloration, and integrity of restoration. METHODS: The proposed flat and 90-degree shoulder marginal endocrown assessment trial is an open-label, parallel-group, multicenter randomized controlled trial involving two hospitals. A total of 200 patients will be included in this trial, and the following patient inclusion criteria will be applied: good oral hygiene habits, no periodontal diseases, receipt of standard root canal treatment, and need for endocrown restoration. Patients will be enrolled after providing signed informed consent and will be divided into two groups (flat and 90-degree shoulder endocrown) in accordance with a random number table. Treatment allocation will be balanced (1:1). Endocrowns will be cemented by dual-cured luting composite. Clinical evaluations will be performed at baseline and at 24 months after treatment in accordance with modified US Public Health Service criteria by two independent evaluators. The primary outcome will be marginal fit; secondary outcome measures will include debonding, marginal discoloration, and integrity of restoration. All acquired data will be analyzed by an independent statistician. Wilcoxon one-sample tests will be used for intra-group comparisons, and Wilcoxon two-sample tests will be used for inter-group comparisons. The Bonferroni method will be used to correct for multiple comparisons, and hierarchical logistic regression will be applied to determine central effects. DISCUSSION: The results of this trial will provide a clinical basis for clinicians to restore teeth by endocrowns and to improve long-term restoration for patients. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT03398395. Registered on 12 January 2018.

Functional Characterization of c-di-GMP Signaling-Related Genes in the Probiotic Lactobacillus acidophilus.

The bacterial second messenger cyclic diguanylate monophosphate (c-di-GMP) regulates a series of cellular functions, including biofilm formation, motility, virulence, and other processes. In this study, we confirmed the presence of several c-di-GMP related genes and evaluated their activities and functions in Lactobacillus species. Bioinformatic and biochemical analyses revealed that Lactobacillus acidophilus La-14 have an active c-di-GMP phosphodiesterase (PdeA) that may act in the metabolic cycle of c-di-GMP. A GGDEF protein (DgcA) induced two c-di-GMP-dependent phenotypes (low motility and high production of curli fimbriae) in Escherichia coli by heterologously expressed in vivo but showed no diguanylate cyclases activity in vitro while in the expression without the N-terminal transmembrane domain. The degenerated EAL-domain protein (PdeB), encoded by the last gene in the gts operon, serve as a c-di-GMP receptor which may be associated with exopolysaccharide (EPS) synthesis in L. acidophilus. Heterologously expressed GtsA and GtsB, encoded by the gts operon, stimulated EPS and biofilm formation in E. coli BL21. Constitutive expression in L. acidophilus revealed that a high concentration of intracellular DgcA levels increased EPS production in L. acidophilus and enhanced the co-aggregation ability with E. coli MG1655, which may be beneficial to the probiotic properties of Lactobacillus species. Our study imply that the c-di-GMP metabolism-related genes, in L. acidophilus, work jointly to regulate its functions in EPS formation and co-aggregation.

[Expression, purification and activity analysis of GGDEF and EAL domain-containing proteins from Lactobacillus acidophilus].

OBJECTIVE: To identify the functions of the proteins containing the GGDEF or EAL domain in Lactobacillus acidophilus for investigation of the regulatory mechanism of c-di-GMP in this strain. METHODS: The DNA fragments of NH13_07045-GGDEF, NH13_07050 and NH13_07055 from Lactobacillus acidophilus ATCC4356 were amplified by PCR and cloned into the expression vector pMAL-His-c2. After sequencing, the recombinant plasmids were transformed into competent Escherichia coli cells, which were induced by IPTG to express the recombinant proteins fused with maltose binding protein (MBP). The fusion proteins were purified using amylose resin column for diguanylate cyclase (DGC) or phosphodiesterase (PDE) activity assays in vitro followed by analysis with high-performance liquid chromatography (HPLC). RESULTS: The target DNA fragments were obtained by PCR, and their sequences were all identical to that in GenBank. The purified and concentrated fusion proteins, which were identified by SDS-PAGE and Western blotting, had relative molecular masses of 59 kD, 67 kD and 72 kD. HPLC analysis showed no DGC activity in NH13_07045-GGDEF, while PDE activity was found in NH13_07050 but not in NH13_07055. CONCLUSION: We obtained the protein encoded by NH13_07050 that possesses PDE activity in vitro. This protein may facilitate the evaluation of the regulatory function of c-di-GMP in Lactobacillus acidophilus.