Arsenic effectively improves the degradation of fluorene by Rhodococcus sp. 2021 under the combined pollution of arsenic and fluorene.

The performance of bacterial strains in executing degradative functions under the coexistence of heavy metals/heavy metal-like elements and organic contaminants is understudied. In this study, we isolated a fluorene-degrading bacterium, highly arsenic-resistant, designated as strain 2021, from contaminated soil at the abandoned site of an old coking plant. It was identified as a member of the genus Rhodococcus sp. strain 2021 exhibited efficient fluorene-degrading ability under optimal conditions of 400 mg/L fluorene, 30 °C, pH 7.0, and 250 mg/L trivalent arsenic. It was noted that the addition of arsenic could promote the growth of strain 2021 and improve the degradation of fluorene - a phenomenon that has not been described yet. The results further indicated that strain 2021 can oxidize As3+ to As5+; here, approximately 13.1% of As3+ was converted to As5+ after aerobic cultivation for 8 days at 30 °C. The addition of arsenic could greatly up-regulate the expression of arsR/A/B/C/D and pcaG/H gene clusters involved in arsenic resistance and aromatic hydrocarbon degradation; it also aided in maintaining the continuously high expression of cstA that codes for carbon starvation protein and prmA/B that codes for monooxygenase. These results suggest that strain 2021 holds great potential for the bioremediation of environments contaminated by a combination of arsenic and polycyclic aromatic hydrocarbons. This study provides new insights into the interactions among microbes, as well as inorganic and organic pollutants.

Theoretical Insights into Imidazolidine Oxidation of Imidacloprid by Cytochrome P450 3A4.

The metabolic mechanisms for imidazolidine oxidation of imidacloprid (IMI) by cytochrome P450 3A4 (CYP3A4) have been investigated using quantum mechanical/molecular mechanical (QM/MM) calculations. The binding mode of CYP3A4 with IMI is examined by molecular docking in collaboration with molecular dynamics (MD) simulations. The results show that there are six amino acid residues, involving Arg192, Phe195, Ile349, Ala285, Phe284 and Phe88, closely distributed around the IMI. The binding free energy analysis exhibits that the CYP3A4-IMI binding structure is stabilized by electrostatic interaction and van der Waals interaction. Arg192 plays a major role in the binding of CYP3A4 with IMI based on its polarity and the hydrogen bond between the H atom in Arg192 side chain and the nitryl O atom of IMI. Two possible pathways, pathway 1 and pathway 2, are evaluated. Two spin states of the Fe (III) center, quartet and doublet, are considered. The free energy calculations are done using QM/MM steered molecular dynamics (SMD) simulation at the B3LYP/6-31 + G(d):ff14SB level for two pathways. The ONIOM QM/MM single-point calculations at the B3LYP/6-311 + G(2d,2p):ff99SB//B3LYP/6-31 + G(d): ff14SB and M06-2X/6-311 + G(2d,2p):ff99SB//B3LYP/6-31 + G(d):ff14SB levels are carried out to obtain more credible energy information. The results indicate that for both pathways, the free energy barriers on the low-spin doublet state are lower than those on the high-spin quartet state. Both pathways are the stepwise processes. Pathway 1 has higher possibility to occur with the free energy barriers being lower by 10-15 kcal·mol-1 compared with pathway 2, which gives rise to trans-5'-hydroxyl-IMI as the final product. The first proton-transfer is the rate-limiting step and the calculated activation free energy is consistent with the experimental conclusion.

Effects of muramyl dipeptide on the differentiation of human dental pulp cells / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the nucleotide-binding oligomerization domain-2 (NOD-2) gene expression in deep caries and the effects of NOD-2 agonist muramyl dipeptide (MDP) on the differentiation of human dental pulp cells (hDPC).</p><p><b>METHODS</b>NOD-2 gene level in deep caries and healthy pulp tissue was determined by real-time quantitative polymerase chain reaction (realtime-PCR). Realtime-PCR, Western blotting and immunofluorescence were performed to evaluate NOD-2 gene and protein expression. Dentin sialoprotein (DSP) protein level was assessed when hDPC were challenged by different concentrations of MDP for 24 hours, and sialophosphoprotein (DSPP), osteocalcin (OCN) mRNA and osteopontin (OPN) protein level were detected at different time points after incubation with 0.1 mg/L MDP.</p><p><b>RESULTS</b>NOD-2 mRNA level was higher in pulp tissue of deep caries (0.2610 ± 0.0824) than that in healthy controls (0.0024 ± 0.0002), P < 0.05. The expression of NOD-2 gene and protein increased in a time denpendent manner upon stimulation with MDP. Immunofluorescence confirmed that NOD-2 protein was located in cytoplasm. Moreover, 0.1 mg/L MDP augmented DSP protein level. DSPP and OCN mRNA were elevated with time and reached the peak at 12 h and down-regulated. OPN protein level also increased with time.</p><p><b>CONCLUSIONS</b>Dental pulp NOD-2 expression are up-regulated in pulp tissue of deep caries. MDP may be related to the differentiation of hDPC.</p>

Application and prospect on the resin-dentin adhesion in the root canal therapy / 华西口腔医学杂志

The application of adhesive root canal filling materials is the tendency in root canal obturation. The orientation is to develop the adhesive core material and sealer making a whole structure. In this review, we summarized the researches on the resin-dentin adhesion in the root canal obturation.

Clinical observation on the characteristics of occlusion and tooth abrasion in patients with cracked tooth / 中华口腔医学杂志

<p><b>OBJECTIVES</b>To investigate the occlusal characteristics and the condition of tooth abrasion in patients with cracked tooth and to discuss the etiology of the cracked tooth and the relationships between occlusal disorder, tooth abrasion and cracked tooth.</p><p><b>METHODS</b>Twenty-seven patients with cracked tooth were selected. The occlusal courses were recorded by T-ScanIII system in intercuspal position, protrusive movement and lateral movement. Teeth with cracked tooth were regarded as the cracked tooth group, and the healthy adjacent teeth as the control group. The distribution of premature contact, occlusal interference, the center of occlusal force were examined. The abrasive conditions of the two groups were recorded according to the Smith tooth wear index and compared.</p><p><b>RESULTS</b>There were more teeth with occlusal interference in cracked tooth group (20 teeth) than in the control group (6 teeth), which was significantly different (OR = 5.67, chi(2) = 8.45, P = 0.003). In 24 patients with single affected tooth, the center of occlusal force (COF) located in the inside and outside ellipse were 6 teeth (25%) and 18 teeth (75%) respectively, Z test showed that there were statistical differences between the cracked tooth group and normal people. In cracked tooth group, the proportion of the teeth with abrasion was higher in teeth with occlusal interference than those without occlusal interference (chi(2) = 4.79, P = 0.029).</p><p><b>CONCLUSIONS</b>The formation of the cracked tooth was related to the occlusal disorder and associated with the tooth abrasion.</p>

Morphological characteristics of the mandibular first premolars in people from Pearl River Delta region in Guangdong province / 华西口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the morphological characteristics of the mandibular first premolars in people from Pearl River Delta region in Guangdong province using three techniques, including periapical radiographs, the radiographs with files inserted the canals and the clearing technique.</p><p><b>METHODS</b>A total of 363 extracted mandibular first premolars were collected and numbered. Two preoperative radiographs were taken in buccolingual and mesiodistal directions respectively. After access opening, the files were placed in the canals and two other radiographs were taken. The mandibular first premolars with multi-canal system were selected and observed under dental operating microscope (DOM). The mandibular first premolars were made transparent and were categorized using the Vertucci's classification.</p><p><b>RESULTS</b>There were different results among the three approaches. Periapical radiographs could be used to distinguish only between one and multiple canals systems. The incidence of multiple canals was 33.33% from the radiographs with file. The mandibular first premolars had a high frequency (34.44%) of multi-canal system by clearing method. The root canal morphology of the mandibular first premolars showed great variance. The canal orifices of the mandibular first premolars with one or two canal distributed in a buccolingual line. The floor of pulp chamber of the mandibular first premolars with three or four canals was a plat form.</p><p><b>CONCLUSION</b>The mandibular first premolars have a high frequency multi-canal system and could be classified in many categories. Using DOM and radiographs with file is a useful way in judging the canal numbers and categories.</p>

Preparation and stability assessment of a new resin root canal filling material / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To synthesize a new resin root canal filling material (NRCFM) and evaluate its stability in water and artificial saliva.</p><p><b>METHODS</b>The new root canal filling material was made of thermoplastic elastomer (TPE), ethylene vinyl acetate (EVA) and activity fillers. The NRCFM's stability in water and artificial saliva with different pH values was assessed using gravimetric analysis, ICP and FE-SEM.</p><p><b>RESULTS</b>NRCFM1 and NRCFM2 were successfully made. Gravimetric evaluation showed that the changes in mass over 30 days different solution medium for NRCFM1 and NRCFM2 were comparable to that of GP (P > 0.05) and significantly different from Resilon (P < 0.001). ICP showed slight changes in Si concentration for NRCFM1 and NRCFM2, Zn for GP, Na and Si for Resilon in the alkaline artificial saliva (pH 9.5). GP and Resilon showed release of Zn and Na respectively in distilled water whereas NRCFM1 and NRCFM2 were stable. FE-SEM micrographs showed that there were slight changes on the surface topography of NRCFM1 and NRCFM2.</p><p><b>CONCLUSIONS</b>The new resin root canal filling material NRCFM1 and NRCFM2 had good stability in different experimental solutions.</p>

Comparative study of sealing ability and fracture resistance of roots endodontically treated with bonded and unbonded filling materials / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To compare the sealing ability and fracture resistance of roots endodontically treated with bonded and unbonded filling materials.</p><p><b>METHODS</b>One hundred and fifteen straight mandibular premolar teeth with single canal were divided randomly into 6 experimental groups, with 15 samples each, and 3 control groups. The sealing ability was evaluated using a glucose quantitative microleakage mode and fracture resistance was tested by universal testing machine.</p><p><b>RESULTS</b>The microleakage results showed that the bonded filling material had the lowest value while the unbonded filling material had the highest value in all groups. There were significant differences in microleakage value among the groups (P < 0.01), but no significant difference was noted in the fracture resistance among the testing groups (P = 0.7016).</p><p><b>CONCLUSIONS</b>Bonded filling material enhanced the sealing ability but could not reinforce the fracture resistance of endodontically treated teeth.</p>

Effects of adenovirus-mediated human bone morphogenetic protein-7 on proliferation and differentiation of human dental pulp cells / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate the effect of adenovirus expressing human bone morphogenetic protein-7 (hBMP-7) on proliferation and differentiation of human dental pulp cells.</p><p><b>METHODS</b>The replication-deficient adenoviral vector encoding hBMP-7 gene was constructed by using homologous recombinant modality. The efficiency of transfection was evaluated by fluorescent microscopy and flow cytometry. The expression of hBMP-7 protein in adenovirus-infected dental pulp cells was determined by Western blot. The proliferation of cells was tested by MTT method, the activity of alkaline phosphatase was assayed, von Kossa staining was used to detect mineralized nodule formation, and the expression of DSPPmRNA in cells was detected using semi-quantitative RT-PCR.</p><p><b>RESULTS</b>Green fluorescent protein was visible under fluorescent microscopy. Higher transfection efficiency (91.1 +/- 1.0)% could be obtained at MOI of 75. Western blot from dental pulp cells infected with Ad-hBMP-7 for 48h detected protein expression of a hBMP-7 gene. The activity of alkaline phosphatase in cells was significantly higher than those of the control groups (P < 0.05). The cells infected with Ad-hBMP-7 had the ability of mineralization. DSPP mRNA expression of cells was in a time- and dose- dependent manner.</p><p><b>CONCLUSIONS</b>Ad-hBMP-7 can induce human pulp cells into odontoblasts, but has no obvious effect on their proliferation.</p>