Application of mechanical mobility of periodontal tissues to tooth mobility examination

Tooth mobility examination is important in planning dental treatment, as it may give an indication of alveolar bone loss and the condition of the periodontal ligament. In clinical dental diagnosis a manual tooth mobility examination is useful. However, its determination of tooth mobility is subjective and depends on the skill and experience of the clinician. The authors have previously reported on a device for measuring the biomechanical properties of human periodontium using an impedance head. Using this device, the mechanical mobility of periodontium can be measured and the mechanical parameters of the periodontal physical model are obtained. Tooth mobility is defined objectively on the basis of discriminant scores of mechanical parameters, and a mobility triangle (MT) figure is drawn as a record for visual interpretation. The paper describes the validation of the mechanical mobility measurements and their interpretation using mobility parameters and a personal computer to produce a mobility triangle figure. The method is compared favourably with clinical mobility measurement. The relationship of the model to underlying pathology is tested by measurements performed on various tooth model systems.     

Immunolocalization of lubricin in the rat periodontal ligament during experimental tooth movement

Lubricin is a protein which contributes to the boundary lubrication, facilitating low friction levels at the interfacing surfaces of joints. In tendons and ligaments it facilitates the relative movement of collagen bundles. Its expression is affected by mechanical signals and cytokines. During application of orthodontic forces to teeth, there is a transduction of mechanical forces to the cells of the periodontal ligament (PDL), which triggers several biological reactions causing the synthesis of prostaglandins, cytokines and growth factors. The aim of the present study was to examine the immunolocalization of lubricin and to evaluate if it is time-dependently and differentially detected within the PDL following the application of orthodontic forces to create areas of compression and tension. This was achieved by placing elastic bands between the maxillary first and second molars of 16 male Sprague-Dawley rats (each weighing 120-200 g) for 12 and 24 h. The molar-bearing segments were dissected and processed for histological and immunohistochemical examination. Binding of a monoclonal antibody was used to evaluate lubricin localization using an indirect streptavidin/biotin immunperoxidase technique. Lubricin, was constitutively expressed in the PDL of rat molars. After the experimental force was applied to the tooth, lubricin was down-regulated, on both sides (compression and tension) of the PDL, in a time-dependent fashion, although to a different extent, being at any time more expressed on the tension side. Furthermore, in every sample, almost all PDL cells in the adjacent tooth cementum and alveolar bone, were more heavily immunolabeled by lubricin antibody, contrary to those located in the central portion of the PDL. Lubricin expression therefore seems related to PDL remodeling and tooth displacement following the application of an orthodontic force, and it appears that lubricin may play an important role during tooth movement.     

Phenotypic analyses of mononuclear cells recovered from healthy and diseased human periodontal tissues

Mononuclear cells were recovered from the gingival tissues of normal individuals and from patients with periodontal disease. Lymphocyte phenotypic markers were identified by immunofluorescence after reaction with monoclonal antibodies to T-cell subset markers. The normal tissues exhibited T4/T8 ratios almost identical to those in the peripheral blood. The diseased tissue cell ratios were significantly reduced, in both the adult periodontitis and the juvenile periodontitis groups (P<0.01 andP<0.02, respectively), indicating alterations in the T-cell subset distribution in these tissues. Each diseased patient showed a much decreased T4/T8 ratio in the gingival lymphocytes when these were compared with the peripheral blood ratio from the same patient. The T4/T8 ratios of the more severe sites were significantly lower than those of the less severe sites in the same disease category. The decreases in subset ratios could be attributed to statistically significant reductions in T4⁺-lymphocyte recoveries relative to peripheral blood and also to slight relative increases in T8⁺ lymphocytes. A highly significant (P<0.001) correlation between the average probeable periodontal pocket depth and the T4/T8 ratio of each disease category was demonstrated. The relative recoveries of B cells from the various tissues did not differ between diseased and normal tissues. It is suggested that T-cell regulatory expression in gingival tissues is distinct from peripheral blood regulatory expression and that there is a local immunoregulatory imbalance in periodontal disease.     

Forces applied by anterior and posterior teeth and roles of periodontal afferents during hold-and-split tasks in human subjects

Hold-and-split tasks were performed by 20 subjects (12 females and 8 males) using the right central incisors, canines, 2nd premolars, and 1st molars, respectively. Half a peanut was positioned on a transducer-equipped plate and the subject was instructed to hold the plate with the peanut between two antagonistic teeth, and not using more force than necessary. After ca. 3 s the subject was instructed to split the peanut in a natural manner. Each session consisted of a series of three in which the subject performed the hold-and-split task five times for each tooth. Thus, in total, data were obtained from 60 trials for each subject. The magnitude of the forces and the force rates used to split the peanut increased distally along the dental arch. However, the duration of the split phase was similar for the various teeth examined. During anesthesia of the periodontal ligament (four subjects), no significant changes were seen in the split phase. The forces used to hold the peanut between the teeth also increased distally along the dental arch: 0.60 N for the incisor, 0.77 N for the canine, 1.15 N for the 2nd premolar, and 1.74 N for the 1st molar. The difference in hold forces for the various teeth can be explained by the different sensitivity characteristics of the periodontal afferents innervating anterior and posterior teeth. During periodontal anesthesia, the magnitude and variability of the hold forces increased for all types of teeth, thus supporting the suggestion that periodontal afferent information is used in the regulation of the level of forces used to hold and manipulate morsels between the teeth.     

牙周炎的病变程度与牙髓组织改变关系的研究

为了分析牙周炎的病变程度与牙髓组织改变的关系,对100个牙体完好的具有不同牙周破坏程度的牙周炎患牙进行了组织学观察,分析牙根暴露量、牙周袋深度和牙齿松动度与牙髓病变的关系。结果表明牙周炎的病变程度与牙髓改变有一定的关系:在牙周炎时,随着牙周破坏程度加重,牙髓病变发生率逐渐增高,根据这个观察结果,作者认为牙髓炎症与牙周炎有一定的关系,但与牙周的破坏程度无重要关系。牙髓坏死主要见于牙周破坏非常严重的病例。     

人体乳腺组织电阻抗特性的研究

以人体乳腺组织电阻抗特性为依据的乳腺电阻抗扫描成像技术的出现,为乳腺癌的早期检查与辅助诊断开辟了一个新的方向。人体乳腺组织的电阻抗特性反映了乳腺组织的病理生理状态,而对它的测量成为乳腺电阻抗扫描成像技术的前提和基础。主要讨论了人体乳腺组织电阻抗特性的测量方法、测量结果以及存在的问题,对乳腺电阻抗成像技术的应用前景进行了展望。     

Comparative analysis of expression of microbial sensing molecules in mucosal tissues with periodontal disease

Host-derived pattern recognition receptors (PRRs) are necessary for effective innate immune engagement of pathogens that express microbial-associated molecular patterns (MAMP) ligands for these PRRs. This study used a nonhuman primate model to evaluate the expression of these sensing molecules in gingival tissues. Macaca mulatta aged 12–24 with a healthy periodontium (n?=?13) or periodontitis (n?=?11) provided gingival tissues for assessment of naturally-occurring periodontitis. An additional group of animals (12–23 years; n?=?18) was subjected to a 5 month longitudinal study examining the initiation and progression of periodontitis, RNA was isolated and microarray analysis conducted for gene expression of the sensing PRRs. The results demonstrated increased expression of various PRRs in naturally-occurring established periodontitis. Selected PRRs also correlated with both bleeding on probing (BOP) and pocket depth (PD) in the animals. The longitudinal model demonstrated multiple TLRs, as well as selected other PRRs that were significantly increased by 2 weeks during initiation of the lesion. While gene expression levels of various PRRs correlated with BOP and PD at baseline and resolution of disease, few correlated with these clinical parameters during initiation and progression of the lesion. These findings suggest that the levels of various PRRs are affected in established periodontitis lesions, and that PRR expression increased most dramatically during the initiation of the disease process, presumably in response to the juxtaposed microbial challenge to the tissues and goal of reestablishing homeostasis.     

Transient response studies of biological cell impedance

The transient response of a biological cell impedance has been found to be distinctly different from a simple exponential. This could follow from the fact that the impedance of a cell membrane could not be simply described by a lossy dielectric, but instead a constant-phase frequency-dependent component of the form (jωC)^α to explain its frequency characteristics. A mathematical analysis of the impedance function of this form shows that the voltage or current transient, in response to a step current or a step voltage respectively, can be expressed by a definite integral and that it is a well-behaved function of time. For a given α the response can be evaluated numerically at discrete time intervals for comparison with experimental results. A simple scheme is introduced to derive from the measured response those parameters characterising the impedance. The scheme utilises the convergence property of the voltage transient curves and by a normalisation process (both in magnitude and in time scale) the measured transient curve can be compared with a set of computed curves iteratively to obtain the closest fit.     

松质骨的一维撞击动力响应

基于对松质骨结构特征的观察,引入了描述松质骨的两相多孔弹性模型,对松质骨在一维撞击载荷作用下的动力响应进行了深入的分析。研究表明：由于松质骨中流体组分的扩散和流动,松质骨呈现着一种强烈的表观粘弹性行为以及能量耗散性质。     

Elastic system fibers in rat incisor periodontal ligament - immunohistochemical study using sections of fresh-frozen un-demineralized tissues

The aim of this study was to examine the localization and distribution of the components of elastic system fibers in the periodontal ligament of continuously erupting rat incisors in an effort to understand the mechanism of the eruption of the tooth. Sections of fresh-frozen, un-demineralized incisors of the rat mandible were prepared for immunohistochemical localization of elastin, fibrillin-2 and microfibril-associated glycoprotein-1 (MAGP-1). The structure of the periodontal ligament was well preserved in sections of fresh-frozen tissues. At the basal region of the ligament, intense immunolabelling for fibrillin-2 and MAGP-1 was observed as dot-like structures (transversely sectioned fibers) mainly on the tooth side of the ligament close to the cementum. These dot-like structures gradually increased in number towards the incisal area and were distributed throughout the tooth side of the ligament. This pattern of distribution was the same as that of reported oxytalan fibers. Elastin-immunopositive fibers were also detected in the ligament, although the labelling was limited and distribution was sparse. In conclusion, both fibrillin-2 and MAGP-1 immunopositive fibers may serve as a scaffold for deposition of tropoelastin during elastogenesis in the periodontal ligament. They may also provide guidance for the migration of fibroblasts to the occlusive side, which generates contractile forces for the movement of the tooth for continuous eruption of incisors.     

人体腰椎松质骨冲击响应的实验研究

本文利用传统的分离式Ｈｏｐｋｉｎｓｏｎ压杆技术，测试了新鲜人腰椎松质骨在冲击载荷下的力学性质。以表观密度和应变率为自变量，以弹性模量、极限强度和终应变为因变量，按模型Ｙ＝ａｐｂｅｃ拟合出回归方程，并与准静态下相同的模型进行了比较，发现高应变率下弹性模量和极限强度与表观密度的相关性下降，而与应变率的相关并有增高的趋势，终应变与表观密度无关而与应变率的相关性显著提高。本文还对松质骨本构关系进行了探讨。     

The effects of acceleration on the mechanical impedance response of a primate model exposed to sinusoidal vibration

Criteria for developing active and passive isolation mechanisms for reducing the effects of whole-body vibration exposure rely on a thorough understanding of the stiffness, damping, and resonance behaviors of the human or human surrogate body. Three Rhesus monkeys were exposed to seated whole-body sinusoidal vibration between 3 and 20 Hz at 0.69 and 3.47 msec⁻² rms (0.1 and 0.5 g peak) accelerations. The mechanical impedance magnitude and phase were calculated as the ratio and phase relation between the transmitted force and input velocity, respectively, at the seat. The resultant profiles showed a significant decrease in the primary resonance frequency with increasing acceleration. At the lower acceleration level, a second lower impedance peak was observed at approximately 5 Hz. A three-mass, two degree-of-freedom model, which included upper torso and leg representation, was used to determine the mechanical parameters that best described the measured responses. The mean stiffness coefficients and the mean undamped natural frequencies associated with the upper torso and leg subsystems showed a significant decrease with increases in the acceleration level. The results of this study strongly suggested that nonlinear stiffness properties were responsible for the observed differences in the biodynamic response of the Rhesus monkey with acceleration level.     

Effect of Nrf2 on rat ovarian tissues against atrazine-induced anti-oxidative response

The environmental persistence and bioaccumulation of herbicide atrazine may pose a significant threat to human health. In this experiment, Wistar rats were treated by 5, 25 and 125 mg·kg^-1 atrazine respectively for 28 days, and the oxidative stress responses as well as the activations of Nrf2 signaling pathway in ovarian tissues induced by atrazine were observed. The results showed that after be treated by atrazine, the proportion of atretic follicles in the rat ovary were increased, the contents of NO and MDA in the tissue homogenates were increased, the over-expressed Nrf2 transferred into the nuclei and played an antioxidant role by up-regulated the expression of II phase detoxifying enzymes such as HO1 and NQO1 and the expression of antioxidant enzymes such as CAT, SOD and GSH-PX.     

动物组织复电阻抗谱随离体时间的变化

建立基于四电极法的测量系统，测量了犬和兔部分离体组织的复阻抗谱，观察了部分动物组织复电阻抗谱随离体时间而发生的变化，结果发现，随着动物组织离体时婚的延长，其复阻抗谱发生显著变化：1、低频段电阻显著增加；2、复阻抗谱的虚部增加(容性成份增加)；3、特征频率降低。结合动物组织离体后发生的组织、细胞水平的变化，我们认为：动物组织复电阻抗谱随离体时间的变化应该与组织细胞内液、细胞外液的离子成份变化相关，同时应该与细胞膜活性相关。     

The mechanical response of active human muscle during and after stretch

Summary Five subjects contracted forearm supinator muscles which were stretched after development of maximal isometric torque. The ratio of torque at the end of stretch over isometric torque at that position was calculated as excess torque. Excess torque increased with stretch velocity and decreased with stretch amplitude, and it was not dependent upon final muscle length. The rate of decay of torque following stretch could not be shown to depend upon stretch variables.The absence of significant changes in myoelectric activity suggested that with high initial forces, reflex activity did not account for the observed changes. Time-constants of decay (0.15 s to 1.8 s) were much greater than time-constants of rise (approx. 0.07 s) of isometric torque at the same muscle length. This indicates that interaction of series elastic and contractile elements is not the sole cause of prolonged torque following stretch. It is concluded that stretch temporarily enhances the intrinsic contractile properties of a group of human muscles in a manner similar to, but quantitatively different from that seen in isolated muscle preparations.     

Common variation in genes related to immune response and risk of childhood leukemia

An abnormal immune response to common infection(s) may be a plausible etiological mechanism in childhood leukemia. We investigated whether 931 tagging single nucleotide polymorphisms (SNPs) selected in gene regions related to immune response are associated with childhood leukemia susceptibility in a hospital-based case-control study (63 cases and 148 controls) conducted among Korean children. The AT or TT genotype of rs7939734 in Fas-associated protein with death domain (FADD) was associated with increased risk of childhood leukemia compared with the AA genotype (odds ratio [OR] = 2.26, 95% confidence interval [95% CI] = 1.20-4.25, p(trend) = 0.0007, min p = 0.002, false discovery rate [FDR] p = 0.17). The CG or GG genotype of rs2301696 in TRPM5 was associated with decreased risk of childhood leukemia compared with the CC genotype (OR = 0.30, 95% CI = 0.14-0.63, p(trend) = 0.002, min p = 0.004, FDR p = 0.17). Our findings suggest that genetic polymorphisms in immune response genes might play a role in childhood leukemia development with limited biologic evidence.     

EGFR-p38 MAPK信号通路参与机械通气肺损伤大鼠肺组织HMGB1的表达

 目的：研究表皮生长因子受体(epidermal growth factor receptor, EGFR)-p38丝裂原活化蛋白激酶(mitogen-activated protein kinase, MAPK)信号通路在机械通气肺损伤(ventilator-induced lung injury, VILI)大鼠肺组织高迁移率族盒蛋白1 (high mobility group box 1 protein, HMGB1)表达中的作用。方法：健康SD大鼠32只随机分为4组：对照组（A组）不行机械通气,保留自主呼吸;小潮气量通气组（B组）潮气量(VT)为8 mL/kg;大潮气量通气组（C组）VT为40 mL/kg;大潮气量通气+EGFR拮抗剂AG-1478组为D组。机械通气4 h后处死动物,测定支气管肺泡灌洗液中总蛋白水平、白细胞计数以及肺湿干重比值(W/D)和髓过氧化物酶(MPO)活性,采用HE染色观察肺组织病理学改变,Western blotting方法检测肺组织磷酸化EGFR、磷酸化p38和HMGB1蛋白表达,RT-PCR方法检测EGFR mRNA的表达。结果：通气4 h后,与A组比较,C组肺组织病理学改变明显,总蛋白水平、白细胞计数、肺W/D、MPO活性、EGFR mRNA表达和磷酸化水平、p38磷酸化水平以及HMGB1蛋白表达均显著增加（P<0.05）;与C组比较,D组上述各项指标的变化均显著降低（P<0.05）。结论：大潮气量机械通气可引起大鼠急性肺损伤,其机制可能与通过EGFR-p38 MAPK信号通路介导HMGB1蛋白的表达有关。     

Impact of Toll-like receptor 4 polymorphisms on risk of cancer

Toll-like receptor 4 (TLR4) is one of the key immune system effectors playing the main role in recognition of viruses and bacteria. Dysregulation of the TLR4 signaling owing to single nucleotide polymorphisms (SNPs) may alter the ligand binding and balance between pro- and anti-inflammatory cytokines, thereby modulating the risk of chronic inflammation and cancer. TLR4 polymorphisms may be associated with at least nine types of cancer. The most intensively investigating TLR4 polymorphisms are Asp299Gly (rs4986790) and Thr399Ile (rs4986791). It seems to be that Asp299Gly and Thr399Ile are related to increased risk of precancerous gastric lesions, and, possibly, gastric cancer. Thr399Ile also may be connected with gallbladder cancer, and both of these polymorphisms apparently have no impact on risk of prostate cancer. However, the data about many SNPs and their associations with different types of cancer are conflicting, and further large, well-designed, comprehensive studies in various populations are necessary for solution of this problem. The short list of TLR4 SNPs for further investigation may include TLR4_896A/G (Asp299Gly, rs4986790), TLR4_1196C/T (Thr399Ile, rs4986791), Thr135Ala, TLR4_1859 G/A (rs11536858), TLR4_2032T/C (rs10116253), TLR4_2437A/G (rs1927914), TLR4_2856T/C (rs10759932), TLR4_3725 G/C (rs11536889), TLR4_7764 G/A (rs1927911), TLR4_11350G/C, TLR4_11912 G/T (rs2149356), TLR4_16649G/C (rs7873784), and TLR4_17050T/C (rs11536891).     

基于车人碰撞事故重建的行人头部动力学响应

目的 研究行人交通事故中,不同碰撞速度、不同车型及行人不同受撞击部位与行人头部损伤严重度的关系。方法 通过MADYMO多刚体动力学软件对一起有视频的行人交通事故进行事故重建,获得初始和边界条件,然后通过获得的边界和初始条件进行不同车速(20、30、40、50、60 km/h)、不同车型(轿车、SUV型车、面包车)、行人不同受撞击部位(正面、侧面、背面)的模拟碰撞实验,对模拟碰撞实验中行人头部损伤情况进行分析,并利用两例真实行人交通事故对部分结果进行验证。结果 不仅车辆碰撞速度、车辆前置结构影响行人头部损伤严重度,行人受撞击部位也是影响行人头部损伤严重度的重要原因。在碰撞速度≤30 km/h时,行人与地面接触造成的损伤可能比与车辆造成的损伤严重;碰撞速度≥40 km/h时,行人头部损伤主要是与车辆接触所致。结论 利用监控录像能比较准确地开展行人交通事故重建,从而对行人动力学响应进行分析。在行人交通事故频发路段,对不同车型进行不同限速,能有效减小行人头部损伤的严重程度。