Dextranase from Arthrobacter oxydans KQ11-1 inhibits biofilm formation by polysaccharide hydrolysis

Dental plaque is a biofilm of water-soluble and water-insoluble polysaccharides, produced primarily by Streptococcus mutans. Dextranase can inhibit biofilm formation. Here, a dextranase gene from the marine microorganism Arthrobacter oxydans KQ11-1 is described, and cloned and expressed using E. coli DH5α competent cells. The recombinant enzyme was then purified and its properties were characterized. The optimal temperature and pH were determined to be 60°C and 6.5, respectively. High-performance liquid chromatography data show that the final hydrolysis products were glucose, maltose, maltotriose, and maltotetraose. Thus, dextranase can inhibit the adhesive ability of S. mutans. The minimum biofilm inhibition and reduction concentrations (MBIC₅₀ and MBRC₅₀) of dextranase were 2 U ml^?1 and 5 U ml^?1, respectively. Scanning electron microscopy and confocal laser scanning microscope (CLSM) observations confirmed that dextranase inhibited biofilm formation and removed previously formed biofilms.     

Influence of connection type on the biomechanical behavior of distal extension mandibular removable partial dentures supported by implants and natural teeth

Few studies are performed to evaluate the influence of connection type on the stress distribution of distal extension mandibular removable partial dentures (RPDs) supported by both implants and natural teeth. In this study, five three-dimensional finite element models were prepared to simulate mandibular bilateral partially edentulous arches. Four were RPDs supported by both implants and natural teeth, and the other one was RPDs supported only by natural teeth. The maximum equivalent (EQV) stress values of bone around implants, the abutments, and the mucosa displacements of the related supporting structures were measured. It was found that a non-rigid telescopic coping was more favorable to protect the implant than a rigid telescopic coping. Compared with other connection types, the easy resilient attachment (ERA) system seemed to be effective to associate implant without complications. However, the results obtained in the present study should be cautiously interpreted in the clinic.     

Mechanical response comparison in an implant overdenture retained by ball attachments on conventional regular and mini dental implants: a finite element analysis

This study investigates the bone/implant mechanical responses in an implant overdenture retained by ball attachments on two conventional regular dental implants (RDI) and four mini dental implants (MDI) using finite element (FE) analysis. Two FE models of overdentures retained by RDIs and MDIs for a mandibular edentulous patient with validation within 6% variation errors were constructed by integrating CT images and CAD system. Bone grafting resulted in 2 mm thickness at the buccal side constructed for the RDIs-supported model to mimic the bone augmentation condition for the atrophic alveolar ridge. Nonlinear hyperelastic material and frictional contact element were used to simulate characteristic of the ball attachment-retained overdentures. The results showed that a denture supported by MDIs presented higher surrounding bone strains than those supported by RDIs under different load conditions. Maximum bone micro strains were up to 6437/2987 and 13323/5856 for MDIs/RDIs under single centric and lateral contacts, respectively. Corresponding values were 4429/2579 and 9557/5774 under multi- centric and lateral contacts, respectively. Bone micro strains increased 2.06 and 1.96-folds under single contact, 2.16 and 2.24-folds under multiple contacts for MDIs and RDIs when lateral to axial loads were compared. The maximum RDIs and MDIs implant stresses in all simulated cases were found by far lower than their yield strength. Overdentures retained using ball attachments on MDIs in poor edentulous bone structure increase the surrounding bone strain over the critical value, thereby damaging the bone when compared to the RDIs. Eliminating the occlusal single contact and oblique load of an implant-retained overdenture reduces the risk for failure.     

Expression of RNA-binding protein Rbfox1l demarcates a restricted population of dorsal telencephalic neurons within the adult zebrafish brain

Rbfox RNA-binding proteins are expressed in the adult mammalian brain and are required for proper brain development and function. Studies in mice and humans have implicated Rbfox1/RBFOX1 in autism, neuronal excitation and epilepsy, and Rbfox2/RBFOX2 in cerebellar development. The zebrafish has emerged as a prominent model system for brain study, possessing neuroanatomical conservation with mammals and an extensive capacity for adult neurogenesis and plasticity. In this study, we characterize Rbfox1l and Rbfox2 expression in the adult zebrafish brain. While Rbfox2 is expressed broadly, Rbfox1l is expressed in restricted populations of neurons in the dorsal telencephalon and cerebellum. In the dorsal telencephalon, Rbfox1l is expressed in a specific population of neurons spanning Dm and Dc regions. In the cerebellum, Rbfox1l and Rbfox2 are expressed in the Purkinje cell layer, reminiscent of Rbfox1 and Rbfox2 expression in the mammalian cerebellum. Our findings motivate future studies of Rbfox function in the zebrafish brain.     

西安市某医院成人与儿童血清25羟基维生素D水平的研究

目的:比较西安市某医院不同年龄段的成人与儿童血清25羟基维生素D(25-OH-VD)水平,并探讨其水平与年龄之间的关系。方法:收集2017年1月-2018年1月西安高新医院检测血清25-OH-VD的2116例样本,比较成人与儿童血清中25-OH-VD水平的差异,分析成人与儿童血清中25-OH-VD水平与年龄之间的关系。结果:儿童组健康人群、低水平人群血清25-OH-VD水平均高于成人组(P0.05);儿童组健康人群、低水平人群血清25-OH-VD水平与年龄呈负相关(P0.05),成人组健康人群血清25-OH-VD水平与年龄呈正相关(P0.05)。结论:西安市某医院的儿童血清25-OH-VD水平高于成人,且成人与儿童的血清25-OH-VD水平与年龄存在一定的关系,有必要建立不同的参考区间,为临床诊治提供更精确的依据。     

Novel CaO/polylactic acid nanoscaffold as dental resin nanocomposites and the investigation of physicochemical properties

In this study, for the first time, calcium oxide (CaO)/polylactic acid nanoscaffolds were synthesized by co‐precipitation assistant reverse micelles method. The physical and chemical (physicochemical) properties of the structures as dental resin composites were also studied. Nanocomposite materials as primary and basic dental compounds can be conveniently applied as dental filling materials with a high esthetic quality. In this research nanoscaffolds act as a bed for nanoparticles and improve the mechanical and chemical (mechanochemical) properties, CaO nanoparticles were loading in polylactic acid nanoscaffold as a bioactivity polymer for usage in the dental resin composites. Mechanical properties of the dental resin composite containing CaO/polylactic acid nanoscaffold were calculated: the flexural strength (137.2 MPa), modulus (12.9GPa) and compressive strength (344.2 MPa). Potential of the basic nanoparticle and the products were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), dynamic light scattering (DLS), ultraviolet‐visible spectroscopy (UV‐visible) and atomic force microscopy (AFM) showed the size of the optimized nanostructures was about 85 to 120 nm. According to TGA results of polylactic acid nanofibers with thermal stability below 300°C these high thermal stability materials can be used as dental resin composites.     

Lipopolysaccharide upregulates the proliferation,migration, and odontoblastic differentiation of NG2+ cells from human dental pulp in vitro

NG2⁺ cells have been proven to differentiate into odontoblasts in vivo, and their contribution to odontoblasts is significantly increased, especially after tooth injury. However, their characteristics in vitro, especially under an inflammatory environment, are still not fully understood. Therefore, this study aimed to explore their proliferation, migration, and odontoblastic differentiation ability after treatment with lipopolysaccharide (LPS) in vitro. In our study, NG2 ⁺ cells were isolated from the human dental pulp by magnetic‐activated cell sorting, and these isolated cells were proven to be NG2 ⁺ by immunostaining. When compared with human dental pulp cells (hDPCs), the NG2 ⁺ cells showed no significant differences in cell migration with or without LPS incubation, but their proliferative ability was weaker. When treated with LPS, NG2 ⁺ cells expressed elevated levels of pro‐inflammatory cytokines including interleukin‐1β (IL‐1β), IL‐6, IL‐8, and tumor necrosis factor‐α, and among these, the expression of IL‐1β and IL‐6 were higher than that of hDPCs. Their multipotent differentiation potential was confirmed by the induction of odontoblastic and adipogenic differentiation, and LPS increased their odontoblastic differentiation capacity. In the odontoblastic differentiation process, Wnt5a, BMP2, and BMP7 mRNA were increased, while the canonical Wnt‐related genes were decreased. In conclusion, the LPS stimulation promotes the migration, proliferative, and odontoblastic differentiation ability of NG2 ⁺ cells from the human dental pulp in vitro, and bone morphogenetic protein and the noncanonical Wnt pathway may be involved in their odontoblastic differentiation. These results indicated their special roles in tooth injury repair and potential application in pulp regeneration.     

布氏田鼠哺乳期低温经历抑制成年期神经再生

哺乳动物在出生前后所经历的环境条件对其成年后的行为和生理等具有重要影响。环境温度是影响动物后代表型的重要因素之一。本研究将分娩当天的布氏田鼠母体和幼仔在常温（23℃±1℃）或低温（4℃±1℃）饲养,断乳（21日龄）时转至常温环境,至第63日龄时再随机将两组动物各分为常温组和低温暴露组,期间检测体重、摄食量、静止代谢率、认知能力和神经细胞增殖和存活等,以验证哺乳期的低温经历可影响成年动物的代谢生理、行为表型和相关脑区神经再生的假说。结果发现：哺乳期低温经历导致成年布氏田鼠摄食量显著降低,与代谢有关的下丘脑以及学习记忆有关的海马区细胞增殖和存活数量减少。当动物在成年期面临冷暴露时,与哺乳期常温经历的动物相比,哺乳期低温经历的动物摄食量较低,在Y迷宫新异臂中的穿梭次数和停留时间显著降低,但海马和下丘脑部分核团的细 胞增殖以及海马CA的细胞存活明显升高。这表明哺乳期低温经历对布氏田鼠的能量代谢、行为和相关脑区的成体神经再生产生了持久的抑制效应,但成年后再次面对低温时,动物的代谢能力和代谢及学习记忆相关脑区的神经细胞可塑性优于哺乳期未曾经历低温的动物。     

燃煤污染型氟中毒患者氟暴露、骨相损伤程度与骨形成标志物的关系

慢性氟暴露是世界范围内的公共卫生问题之一.为研究燃煤污染型氟中毒患者中氟暴露、骨相损伤程度与骨形成标志物血清碱性磷酸酶(ALP)、骨钙素(BGP)之间的相关关系,以贵州省织金县荷花村(燃煤污染型地方性氟中毒病区)和安顺市张官村(非氟暴露村)为调查点,采集环境样品,采用氟离子选择电极法测定环境介质及食物中的氟含量.在知情同意的原则下,对295例氟暴露和85例非氟暴露调查对象进行氟斑牙、氟骨症诊断;收集其尿液及外周血,测定尿氟(UF)浓度、ALP活性和BGP含量.结果表明: 病区环境中大米、辣椒、玉米、饮水、黏土、菜土、煤以及室内外空气氟含量均明显高于对照区,但较以往报道数据降低;随着尿氟浓度的升高,ALP活性、BGP含量显著升高,氟骨症病情差异有统计学意义,氟斑牙病情差异无统计学意义;氟骨症病情与ALP活性、BGP含量呈正相关.表明燃煤污染型低氟暴露可引起人群的骨相损害,且ALP、BGP可用于评估氟骨症患者骨转换情况,在氟骨症的辅助诊断、疗效评估中有着一定的应用价值.