Bacterial endotoxins in periodontal health and diseases

Bacterial endotoxins are a major concern in periodontal health and diseases owing to their structure and biological activity. With up-to-date knowledge of endotoxins and the recent findings about the influence of endotoxins in dental health, their probable mode of pathogenesis, and standard detection methods, this review analyzes the potential efficacy and benefits of probiotics in combination with conventional and contemporary treatment measures. In the oral cavity, Gram-negative bacteria are documented to predominate in the pulpal lesions with radiolucent areas and in the root canal with pulp necrosis, where they pose an absolute threat by promoting a series of inflammatory reactions. Endotoxin, a constituent of Gram-negative bacteria establishes a nexus between cytokine stimulation and proinflammatory reactions, therefore plays a critical role in decaying dental pulp and modulating periodontal diseases. Currently, the treatment regimen involves several biochemical preparations. In addition, probiotics have been reported to control endotoxin in gingivitis and contribute to the overall improvement of dental health. A potential benefit of a combination of probiotics as a complementary treatment along with the conventional treatment warrant more empirical evidence to elucidate its role and mechanism in resolving the clinical manifestations associated with endotoxins in the periodontal region.     

Regeneration in echinoderm larvae.

The ability of echinoderms to regenerate missing body parts has been a subject of interest to scientists for many years. Asexual reproduction (by fission or budding) is a phenomenon that involves regeneration of missing structures. Although asexual reproduction and regeneration have been the focus of many studies in adult echinoderms, there have been comparatively fewer studies examining these phenomena in echinoderm larvae, and most of these have been conducted in the last few years. In this article we review regeneration in larval echinoderms. We also discuss larval asexual reproduction.     

Direct activation of cardiac adrenergic nerve endings by defibrillator shocks

Defibrillator shocks ranging in intensity from three to nine times current threshold were delivered to four isolated, metabolically supported, beating canine hearts. The shocks produced an immediate, current-dependent depression of left ventricular isovolumic systolic pressure. This depression was transient, reproducible, and was followed by a transient overshoot in ventricular systolic pressure. Then 1 mg propranolol hydrochloride in 1 ml H2O was injected into the coronary arterial supply of the isolated heart, and the shocks were repeated. The magnitude of the immediate cardiac depression after shock was unchanged; however, the time required for full recovery of left ventricular systolic pressure to a pre-shock control value was prolonged. In addition, the transient overshoot in ventricular systolic pressure seen in the untreated state was absent. These results are consistent with the hypothesis that defibrillatory shocks produce a direct activation of cardiac adrenergic nerves, which aid in recovery of ventricular contractility following defibrillator shocks.     

Regulatory mechanisms of periodontal regeneration

The periodontal ligament, located between the cementum and the alveolar bone, has a width ranging from 0.15 to 0.38 mm. Regeneration and homeostasis of the periodontal ligament are highly significant functions in relation to periodontal therapy, tooth transplantation or replantation, and orthodontic tooth movement. The purpose of this review is to discuss the regulatory mechanisms of regenerative and homeostatic functions in the periodontal ligament based on currently published studies and also on our own experimental data. We consider the capability of the ligament tissue to promote or to suppress calcification in connection with bone and cementum formation and the maintenance of the periodontal ligament space. Also discussed are the involvement of the periodontal ligament tissue in the regenerative ability, cell proliferation, growth and differentiation factors, extracellular matrix proteins, homeostatic phenomena, function of Malassez epithelial rests, tooth movement, or occlusal loading. Regulatory mechanisms for regeneration and homeostasis of the periodontal ligament are hypothetically proposed.     

Age-dependent changes of the periodontal ligament in rats

Even after the end of the natural tooth eruption, there is a continuous renewal of the periodontal collagenous fiber system, depending on functional demands. The aim of this study was to analyse the age-dependent changes and regional differences of the collagen renewal rate of the periodontal ligament in healthy rats. The study was performed by autoradiography of the molars of rats aged 1, 8, and 18 months, where collagen was labelled by intravenously applied 3H-proline. After an 8-hour incorporation period, the animals were killed. For comparative examinations, molar roots were subdivided into cervical, middle, and apical thirds. Structural and quantitative analyses were performed by light microscopy and autoradiography, using an image-analysing computer-assisted operating unit that determined the 3H-proline-labelled collagen by photometry based on extinction measurement. With increasing age of the animals, the number of silver grains (3H-proline-blackened collagen) was reduced and the quantitative evaluation indicated a reduction of 3H-proline in the periodontal ligament. The lowest level of 3H-proline activities was observed in the middle, and the highest level in the apical root third, independent of age. All preparations revealed condensations of silver grains, which were located in the region of the periodontal ligament adjacent to the alveolar bone, but did not reveal any preferred position with regard to the dental topography. With progressive age, the uptake of 3H-proline in the periodontal ligament was reduced by about 20 to 30%, a result that corresponds to a decrease in collagenous fiber production. Collagen was mainly formed in the apical and cervical root third, starting from the alveolar bone side, presumably in response to functional strain.     

Regeneration of spines and pedicellariae in echinoderms: a review.

Morphogenesis of tissues during regeneration of echinoderm spines and pedicellariae is reviewed. Regeneration of the skeleton is rather well documented while that of associated soft tissues is poorly investigated. In particular, little information is available on the early regeneration stages which follow wound healing. From the available information, it is suggested that regeneration of broken spines proceeds through a morphallactic process of which the organizational information, as well as the involved cells, lies in the stump. In contrast, regeneration of removed spines and pedicellariae may depend on an epimorphic process whose organizational information could be located in the mutable connective tissue that joins the appendage to the main body wall.     

Calcium in secretory vesicles of neurohypophysial nerve endings: quantitative comparison by X-ray microanalysis of cryosectioned and freeze-substituted specimens

The calcium content of individual secretory vesicles in rat neurohypophysial nerve endings was measured by quantitative electron probe X-ray microanalysis. Directly frozen control and potassium-depolarized isolated endings were analysed using two presumably equivalent preparative techniques: (1) freeze-substitution in presence of oxalic acid followed by sectioning of resin-embedded pellets; or (2) direct cryosectioning of the frozen pellets followed by freeze-drying in the column of the microscope. In the pellets of stimulated endings, both approaches revealed an increase in the calcium content of neurosecretory vesicles. This increase was statistically more significant in the specimens prepared by cryosectioning, probably because in this case the contribution of 'dead' nerve endings could be eliminated on the basis of excessive cytoplasmic sodium and chloride. The results demonstrate that an increase in cytosolic calcium can lead to an increase in intravesicular calcium, and that when this occurs, it occurs within a subpopulation of vesicles in a given nerve ending. In addition, measured intravesicular calcium was dispersed over a wide range of concentrations, as predicted by the hypothesis of intravesicular calcium priming. When the vesicular calcium content was averaged per nerve ending, a relatively wide distribution of concentrations was again observed, indicating that some nerve endings respond more strongly to the stimulation than others.     

薄层色谱仪数据系统升级改造的研究

首次对岛津CS-9000型薄层色谱仪（TLC）的数据系统进行了硬件和软件方面的升级改造。硬件方面，设计了以通用型数字信号处理器（DSP）芯片为主体的数据采集和处理电路，一定程度上提高了数据采集的速度和精密度。软件方面以VB6为基础，开发了数据处理和数据采集界面。该软件可以安装在WINDOWS98、2000、XP环境下，人机对话界面友好，数据处理和采集功能强大，操作简单易学。同时在硬件和软件的设计上充分考虑了分析仪器的共同特征，为设计通用的数据处理系统的硬件和软件奠定了基础。     

科学仪器升级改造的现状和展望

对各种类型科学仪器尤其是分析测试仪器的升级改造方法进行了综述。并对我国的仪器升级改造事业进行了展望。     

The role of periodontal disease in atherosclerotic cardiovascular disease

Atherosclerotic cardiovascular disease (ASCVD) includes a group of disorders of the heart and blood vessels and accounts for major morbidity and premature death worldwide. Periodontitis is a chronic inflammatory disease with the gradual destruction of supporting tissues around the teeth, including gingiva, periodontal ligament, alveolar bone, and cementum. Periodontitis has been found to potentially increase the risk of ASCVD. Generally, oral microorganisms and inflammation are the major factors for periodontitis to the incidence of ASCVD. Recently, evidence has shown that the loss of masticatory function is another important factor of periodontitis to the incidence of ASCVD. In this review, we illustrate the recent finding of the relationship between periodontitis and ASCVD, from a microscale perspective-oral microorganisms, inflammation, and tooth loss. With the high prevalence of periodontitis, it is important to add oral therapy as a regular ASCVD prevention strategy. Regular dental visits could be a helpful strategy for ASCVD patients or general medical practitioners.     

万能渐开线齿形测量仪的智能化改造

主要介绍3201A型万能渐开线齿形测量仪的智能化改造,实现运用单片机进行数据采集和数据处理,并采用Matlab和VC++混合编写计算机程序软件对测量数据进行采集、处理、显示、分析与计算最终得到了有效的结果。     

戴安CSRS阳离子抑制器的再生

针对戴安CSRS阳离子抑制器中毒失效这一实验现象,分析了其产生的原因,并通过实验恢复了抑制器的性能,为今后离子色谱仪用户出现类似问题提供了解决方案。     

油液净化再生技术的应用

对油液的主要性能与影响性能的主要因素作了评述。分析和制定了油液载体净化再生原理和方法。阐述油液载体净化机的工艺特点及流程。对其市场前景作了展望，认为是一种有前途的油液净化再生技术。     

再生润滑油在不同条件下的摩擦学性能研究

通过再生添加剂方法对废汽轮机油和废油膜轴承油进行再生处理,去除废润滑油中的非理想组分,补加适合的添加剂。针对汽轮机和轴承的摩擦副材料特点,采用钢-钢、钢-铜摩擦副材料,在四球摩擦试验机上研究不同试验条件如不同载荷和速度、不同摩擦副材料下再生汽轮机油和油膜轴承油的摩擦学性能,并与对应的新油进行比较。结果表明：再生油对于不同的摩擦副材料（钢/钢和铜/钢）、在不同载荷和速度条件下都具有广泛的润滑适应性,抗磨减摩性能达到甚至超过新油。     

废乳化油的净化与再生新工艺

针对工厂实际情况提出了废乳化油的再生新工艺,克服了传统废油再生工艺的缺点,该工艺综合利用率高,无二次污染,油的回收率可达９０％适合于小规模废乳化油的净化、再生。     

Unbiased and efficient estimation of the total number of terminal bronchiolar duct endings in lung: a modified physical disector

A novel modification of the physical disector is described which was used to estimate the total number of terminal bronchiolar duct endings (TBDEs) in human infant lung. TBDEs are closed three-dimensional space curves of complex shape that are inherently difficult to count from histological sections. However, careful consideration of the microanatomy of the terminal duct endings provides us with the opportunity to define a very simple and unbiased counting rule. To apply the rule in practice we also need to determine a suitable disector height. Owing to the complex shape of the TBDE we had no prior knowledge of what disector height would be suitable for counting the TBDE structures. Exhaustive serial sectioning of complete TBDE structures was carried out and showed that any disector height under 90 μm would give unbiased counts. A further empirical study was then undertaken to determine the most efficient disector height. This was found to be 50 μm.
The total number of TBDEs in the upper lobe of the right lung of six human infants aged between 13 and 25 weeks was also estimated. The estimates of numerical density obtained with our modification of the physical disector were multiplied by estimates of lung lobe volume obtained using Cavalieri's Principle. The total number of TBDEs in the lobes ranged from 15 323 to 57 768, with a mean of 40 306. The average coefficient of error of the number estimates was 19%, which was deemed precise enough given the biological coefficient of variation between TBDE number of 36%.     

溶剂再生塔重沸器泄漏及振动原因分析

某公司芳烃抽提装置溶剂再生塔重沸器近年来多次发生泄漏,在平时的运行中振动也较明显,塔体也有明显的振动。根据GB151—1999对横向流诱发振动的可能性进行了验算分析,认为紊流抖动和流体弹性不稳定引发了管束振动,在振动和腐蚀的联合作用下导致了管束的泄漏。同时提出了解决办法：增加支持板数,更改换热管材质。     

Time-dependent mechanical behaviour of the periodontal ligament

The process of tooth displacement in response to orthodontic forces is thought to be induced by the stresses and strains in the periodontium. The mechanical force on the tooth is transmitted to the alveolar bone through a layer of soft connective tissue, the periodontal ligament. Stress and/or strain distribution in this layer must be derived from mathematical models, such as the finite element method, because it cannot be measured directly in a non-destructive way. The material behaviour of the constituent tissues is required as an input for such a model. The purpose of this study was to determine the time-dependent mechanical behaviour of the periodontal ligament due to orthodontic loading of a tooth. Therefore, in vivo experiments were performed on beagle dogs. The experimental configuration was simulated in a finite element model to estimate the poroelastic material properties for the periodontal ligament. The experiments showed a two-step response: an instantaneous displacement of 14.10 +/- 3.21 microns within 4 s and a more gradual (creep) displacement reaching a maximum of 60.00 +/- 9.92 microns after 5 h. This response fitted excellently in the finite element model when 21 per cent of the ligament volume was assigned a permeability of 1.0 x 10(-14) m4/N s, the remaining 97 per cent was assigned a permeability of 2.5 x 10(-17) m4/N s. A tissue elastic modulus of 0.015 +/- 0.001 MPa was estimated. Our results indicate that fluid compartments within the periodontal ligament play an important role in the transmission and damping of forces acting on teeth.