甘草酸对酸性环境中变异链球菌生长影响的体外研究

目的研究酸性环境中甘草酸对体外培养变异链球菌生长的影响。方法在pH 7.0、pH 5.5和pH 4.0环境中培养变异链球菌,同时在培养基中加入3种浓度（0.78、1.57、3.13 mg·mL-1）的甘草酸,37 ℃下厌氧培养24 h后,测定各组的菌落计数和菌悬液吸光度值,分别以阴性对照组和pH 7.0组细菌生存率为对照,计算各组细菌的生存率。结果以阴性对照组为对照,0.78、1.57和3.13 mg·mL-1甘草酸组在pH 5.5环境时细菌生存率为60.96%、60.27%和45.58%,在pH 4.0时细菌生存率为68.75%、53.12%和45.83%。以pH 7.0组为对照,0.78、1.57和3.13 mg·mL-1甘草酸组在pH 5.5和pH 4.0时细菌生存率分别为52.25%和39.05%、74.39%和43.11%、86.38%和55.30%。结论在酸性环境中,甘草酸能够抑制体外变异链球菌的生长,环境酸度降低可使甘草酸的抑菌作用增强。     

透明质酸改性聚乳酸支架组织工程软骨的构建

目的 利用透明质酸( hyaluronic acid,HA)改性聚乳酸(polylactic acid,PLA)支架来构建同种异体组织工程软骨,分析探讨HA改性PLA支架构建组织工程软骨的可行性.方法 采用盐析法制备出高孔隙率的PLA支架,采用低浓度NaOH、碳化二亚胺和HA进行支架改性.支架预湿后接种第3代兔髁突软骨细胞悬液,体外培养1周后用于动物实验.软骨细胞-HA改性PLA支架复合体为实验组,软骨细胞-PLA支架复合体为对照组.分别于4、6、8周按照标记取出植入物,进行组织学检测.利用ImageJ软件进行免疫组化染色阳性强度的分析.结果 细胞-支架复合体植入后,未产生排斥反应.HE染色结果示软骨样组织形成.Masson染色及甲苯胺蓝染色结果显示染色逐渐加深.Ⅱ型胶原免疫组化染色随时间增加阳性强度增加,实验组4、6、8周时的免疫组化染色强度差异有统计学意义(F=26.68,P=0.000),对照组4、6、8周时的免疫组化染色强度差异有统计学意义(F=20.59,P=0.000).相同时间点实验组Ⅱ型胶原分泌强度高于对照组.结论 利用HA改性PLA支架可以构建同种异体软骨,且其质量高于未改性PLA.     

牛血小板衍化生长因子的氨基酸组成分析

目的：测定分析牛血小板衍化生长因子的氨基酸组成。方法：采用酸水解方法。结果：牛血小板衍化生长因子含有１７种不同量的氨基酸，其中含有相对较多的碱性氨基酸。结论：该因子与人血小板衍化生长因子的氨基酸组成基本相近。     

Burning mouth syndrome (BMS): controlled open trial of the efficacy of alpha-lipoic acid (thioctic acid) on symptomatology

BACKGROUND: Alpha-lipoic acid (ALA), is a potent antioxidant mitochondrial coenzyme, the trometamol salt of thioctic acid that has been shown in clinical studies to be neuroprotective. This study examined the effect of ALA on the symptomatology of Burning mouth syndrome (BMS). SUBJECTS AND METHODS: Forty-two patients with BMS and no clinical or laboratory evidence of organic oral disease were divided into two groups (Test and Control) each of 21 subjects, matched for age and sex. The Test group were given ALA (thioctic acid; Tiobec) for 30 days, as 600 mg per day orally for 20 days followed by 200 mg per day for 10 days. The Control group were given cellulose starch 100 mg per day as placebo for 30 days. All BMS patients were reviewed at 10-day intervals and scored for changes in symptomatology. RESULTS: Significant improvements were shown in the symptomatology of BMS in up to two-thirds of patients with BMS receiving alpha-lipoic acid, in about 15% of those using placebo and also in up to two-thirds of those who, having tried placebo, were switched to ALA.     

Electrochemical self-assembly of nordihydroguaiaretic acid/Nafion modified electrodes and their electrocatalytic properties for catecholamines and ascorbic acid

Electrochemically active 1,4-bis(3,4-dihydroxyphenyl)-2,3-dimethylbutane (nordihydroguaiaretic acid, NDGA) films can be directly deposited on Nafion modified electrodes from aqueous nordihydroguaiaretic acid. The deposited NDGA/Nafion films are stable, and show obvious electrochemical activity in aqueous solutions with various pH. An electrochemical quartz crystal microbalance and cyclic voltammetry were used to study the in situ growth of the NDGA/Nafion films. When freshly prepared NDGA/Nafion films were transferred to aqueous solutions at various pH, the formal potential was found to be pH dependent. The NDGA/Nafion films electrocatalytically oxidized dopamine, epinephrine, and norepinephrine in aqueous solutions, with the electrocatalytic oxidation current developing through the oxidized form of the NDGA/Nafion film. NDGA/Nafion films also showed reversible electrocatalytic properties. Such films electrocatalytically reduce the oxidation products of dopamine, epinephrine, and norepinephrine resulting from the electrocatalytic oxidation of these compounds by the NDGA/Nafion film. The NDGA/Nafion modified films also electrocatalytically oxidized a mixture of dopamine and ascorbic acid. The chemical reaction of dopamine quinone with ascorbic acid was investigated using the rotating ring-disk electrode method.     

Pulpal response to topical application of citric acid to root dentin

Abstract The purpose of the present study was to investigate the pulpal reactions to citric acid (pH 1.0) applied for 3 min to exposed root dentin. We used 48 roots of 24 maxillary and mandibular third and fourth permanent premolars from dogs divided equally into experimental (citric acid) and control (saline) roots. Following surgical exposure of the buccal root surface and the removal of the cementum with a Gracey curette, citric acid or saline was applied on the exposed dentin. The pulpal reactions were histologically evaluated 1, 7 and 15 days postoperatively using hematoxylineosin stained sections. Results obtained from 43 specimens showed no difference in the pulpal response at any of the observation intervals between citric acid and saline-treated teeth.     

正常人唾液中透明质酸含量的研究

目的 检测非刺激和刺激情况下,正常人全唾液和纯肋腺液中透明质酸的含量,以探讨正常人唾液中透明质酸的含量和了解唾液中透明质酸在伤口愈合中的作用。方法 采用酶联免疫吸附试验法（ELISA）,对20名健康成人唾液进行测定。结果 透明质酸的含量依次为：非刺激下全唾液（369.89mg/ml）,刺激下全唾液（158.61ng/m）,非刺激下腮腺液（95.80ng/m）,刺激下腮腺液（79.20ng/ml）。结论 ①唾液中含有透明质酸;②宵同类型的唾液透明质酸的含量有较大差异;③透明质酸在唾液中的高浓度可能有助于唾液的伤口愈合、口腔粘膜的保护和润滑作用。     

Scanning electron microscopic investigation of the effectiveness of phosphoric acid in smear layer removal when compared with EDTA and citric acid

Introduction

The smear layer adheres to dentinal surface, thus occluding the dentinal tubules. Because this layer disfavors the penetration of irrigant solutions and root canal fillings, it should be removed. The aim of this study was to compare the effectiveness of 37% phosphoric acid with that of 17% EDTA and 10% citric acid in the removal of smear layer.

Materials and Methods

Fifty-two maxillary single-rooted human canines were accessed and instrumented. Between each instrument used, the canals were irrigated with sodium hypochlorite. After instrumentation, the teeth were irrigated with distilled water and then divided into groups according to the time and substances employed. The substances used were 17% EDTA, 10% citric acid, and 37% phosphoric acid solution and gel. The experimental time periods were of 30 seconds, 1 minute, and 3 minutes. The samples were prepared and observed by means of scanning electron microscopy. Three photomicrographs (2,000×) were recorded for each sample regarding the apical, middle, and cervical thirds. A score system was used to evaluate the images.

Results

None of the substances analyzed in this study was effective for removing the smear layer at 30 seconds. In the 1-minute period, the phosphoric acid solution showed better results than the other substances evaluated. In the 3-minute period, all the substances worked well in the middle and cervical thirds although phosphoric acid solution showed excellent results even in the apical third.

Conclusions

These findings point toward the possibility that phosphoric acid solution could be a promising agent for smear layer removal.     

Citric acid treatment of periodontitis-affected cementum

Previous studies have described an inconsistent histological occurrence of a zone of surface demineralization on periodontitis-affected cementum following treatment with citric acid, and a lack of connective tissue attachment to the latter surfaces. In view of these findings, the purpose of the present study was to use scanning electron microscopy to examine the surface morphology of cementum from normal and periodontitis-affected root surfaces following citric acid treatment for differences in the effects of the demineralizing solution on these surfaces. Cementum surfaces were derived from the roots of extracted human teeth from areas beneath attached periodontal ligament fibers (normal) and calculus deposits (periodontitis-affected). 5 specimens were evaluated in both groups. Periodontal ligament fibers were removed from normal root surfaces with a curette, and calculus deposits were removed from periodontitis-affected root surfaces using an ultrasonic scaler. The resultant 5 specimens in each group were then sectioned in half, one-half serving as the untreated control and the other as the experimental, citric acid treated specimen. Experimental specimens were immersed in a saturated solution of citric acid, pH 1 for 3 min and then rinsed in tap water. Both control and experimental specimens were dehydrated in ethanol, critical-point dried, sputter-coated with gold and examined in the scanning electron microscope for morphological characteristics. Citric acid treatment of cementum from normal root surfaces produced an undulating, markedly fibrillar surface morphology which is consistent with the exposure of a fibrillar, collagen substrate. Periodontitis-affected cementum, however, was not appreciably altered in appearance by the citric acid treatment, having only a faint mat-like surface texture. (ABSTRACT TRUNCATED AT 250 WORDS)     

Adaptation by Streptococcus mutans to acid tolerance

Our previous continuous culture studies with strains of Streptococcus mutans have indicated that the organism has the capacity of adapt to growth in acidic environments. This study was undertaken to examine this question in more detail. S. mutans Ingbritt and the phosphotransferase system (PTS)-defective mutant, S. mutans DR0001/6, were grown in continuous culture at pH 7.5 and 5.5 or 5.1, and the pH optimum for glucose uptake and glycolysis and the capacity of the cells to generate pH gradients were determined over the pH range 4.5 to 8.0 with steady state, washed cells. In addition, the proton permeability of the cells was measured over the pH range by an acid pulse technique. The results indicate that the pH optimum for glucose uptake by S. mutans Ingbritt grown at pH 7.5 was 7.5 and this optimum shifted to 7.0 and 6.0 for cells grown at pH 5.5 and 5.1, whereas with the S. mutans DR0001/6, the optimum shifted from 7.5 to 7.0 for the pH 5.5 cells. A similar shift in the pH optimum for glycolysis was observed for the 2 strains, and this was particularly pronounced for cells incubated with glucose in the presence of gramicidin to dissipate proton gradients. The capacity of the cells to generate pH gradients was related to their metabolic activity, and although larger gradients were not formed by the pH 5.5 cells, these cells were nevertheless capable of maintaining gradients at a lower pH; S. mutans DR0001/6 generated 2-fold larger pH gradients at pH 5.5 than S. mutans Ingbritt.(ABSTRACT TRUNCATED AT 250 WORDS)     

Electrochemical properties of a tetrabromo-p-benzoquinone modified carbon paste electrode. Application to the simultaneous determination of ascorbic acid,dopamine and uric acid

The electrochemical study of a tetrabromo-p-benzoquinone modified carbon paste electrode (TBQ-MCPE), as well as its efficiency for electrocatalytic oxidation of ascorbic acid, dopamine and uric acid, is described. Cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. Three linear segments were found with slope values of ?58.4 mV/pH, ?28.1 mV/pH and 0.0 mV/pH in the pH range 2.0–7.1, pH 7.1–9.0 and pH 9.0–11.0, respectively. The apparent charge transfer rate constant, k_s, and transfer coefficient, α, for electron transfer between TBQ and CPE were calculated as 3.79 ± 0.10 s^?1 and 0.55, respectively. The electrode was also employed to study the electrocatalytic oxidation of AA, using cyclic voltammetry, chronoamperometry and differential pulse voltammetry as diagnostic techniques. It has been found that the oxidation of AA at the surface of TBQ-MCPE occurs at a potential of about 430 mV less positive than that of an unmodified CPE. The diffusion coefficient of AA was also estimated using chronoamperometry. The kinetic parameters such as the electron transfer coefficient, α, and heterogeneous rate constant, $k_{\mathrm{h}}^{\prime }$, for oxidation of AA at the TBQ-MCPE surface was determined using cyclic voltammetry. Differential pulse voltammetry (DPV) exhibits two linear dynamic ranges and a detection limit of 0.62 μM for AA. In DPV, the TBQ-MCPE could separate the oxidation peak potentials of AA, DA and UA present in the same solution, though at the unmodified CPE the peak potentials were indistinguishable. This modified electrode was quite effective not only to detect AA, DA and UA, but also in simultaneous determination of each component concentration in the mixture.     

聚—DL—乳酸复合材料的细胞毒性评价

本文对新研制的聚-DL-乳酸可吸收复合材料进行细胞毒性的实验研究,采用L-929小鼠成纤维细胞,经材料浸提液与细胞接触2、4、7 天后,在分光光度仪下测定光吸收度,以评价材料的细胞毒性.结果表明;该材料对培养细胞无明显细胞毒性刺激作用,细胞生长良好,各期实验组的细胞增殖状况与阴性对照组相似.     

唾液肌酐和尿酸的酶法测定及其应用

目的　探讨唾液肌酐和尿酸的酶法测定及其与血清肌酐和尿酸的关系。方法　用肌氨酸氧化酶测定唾液肌酐 ,尿酸酶 -过氧化物酶法测尿酸 ,与血清肌酐和尿酸作对照分析。结果　健康人唾液肌酐和尿酸分别为 13.2 7± 5 .15 μmol/L和 10 8.2± 2 5 .4 μmol/L;唾液肌酐与血清肌酐浓度显著相关 (r =0 .88,P <0 .0 1) ,唾液尿酸与血清尿酸亦显著相关 (r=0 .5 3,P <0 .0 1)。结论　唾液肌酐浓度测定可用于慢性肾脏疾病经常性监测手段。     

A differential pulse voltammetric method for simultaneous determination of ascorbic acid,dopamine, and uric acid using poly (3-(5-chloro-2-hydroxyphenylazo)-4,5-dihydroxynaphthalene-2,7-disulfonic acid) film modified glassy carbon electrode

A stable modified glassy carbon electrode based on the poly 3-(5-chloro-2-hydroxyphenylazo)-4,5-dihydroxynaphthalene-2,7-disulfonic acid (CDDA) film was prepared by electrochemical polymerization technique to investigate its electrochemical behavior by cyclic voltammetry. The properties of the electrodeposited films, during preparation under different conditions, and their stability were examined. The homogeneous rate constant, k_s, for the electron transfer between CDDA and glassy carbon electrode was calculated as 5.25(±0.20) × 10² cm s⁻¹. The modified electrode showed electrocatalytic activity toward ascorbic acid (AA), dopamine (DA), and uric acid (UA) oxidation in a buffer solution (pH 4.0) with a diminution of their overpotential of about 0.12, 0.35, and 0.50 V for AA, DA, and UA, respectively. An increase could also be observed in their peak currents. The modified glassy carbon electrode was applied to the electrocatalytic oxidation of DA, AA, and UA, which resolved the overlapping of the anodic peaks of DA, AA, and UA into three well-defined voltammetric peaks in differential pulse voltammetry (DPV). This modified electrode was quite effective not only for detecting DA, AA, and UA, but also for simultaneous determination of these species in a mixture. The separation of the oxidation peak potentials for ascorbic acid–dopamine and dopamine–uric acid were about 0.16 V and 0.17 V, respectively. The final DPV peaks potential of AA, DA and UA were 0.28, 0.44, and 0.61 V, respectively. The calibration curves for DA, AA, and UA were linear for a wide range of concentrations of each species including 5.0–240 μmol L⁻¹ AA, 5.0–280 μmol L⁻¹ DA, and 0.1–18.0 μmol L⁻¹ UA. Detection limits of 1.43 μmol L⁻¹ AA, 0.29 μmol L⁻¹ DA and 0.016 μmol L⁻¹ UA were observed at pH 4. Interference studies showed that the modified electrode exhibits excellent selectivity toward AA, DA, and UA.     

Tooth surface loss and exposure to organic and inorganic acid fumes in workplace air

The effect of inorganic and organic acid fumes on teeth was explored in a cross-sectional study using blind dental examinations. A sample of 180 workers from two factories was randomly drawn. Among the 169 workers who participated in the survey, 88 were exposed to acid fumes and 81 were controls. The percentage of inorganic acid workers with tooth surface loss was 63.2%, while that for the controls was 37.7% (P less than 0.005). The corresponding figures in the organic acid company were 50.0% and 14.3% (P less than 0.02). In both companies the acid workers had significantly more often teeth with surface loss in the maxilla than their controls (P less than 0.02). Both anteriors and posteriors were affected. On the basis of the findings. it can be concluded that acid fumes at work are strongly associated with tooth surface loss.     

An EQCM investigation of oxidation of formic acid at gold electrode in sulfuric acid solution

The oxidation of HCOOH at Au electrode in sulfuric acid solution was investigated using the electrochemical quartz crystal microbalance (EQCM). The potentiodynamic mass responses in HCOOH-containing solution were compared to that in the background solution. This comparison provided valuable information on the mechanism of HCOOH oxidation. The effect of the potential scan rate on the current peak corresponding to oxide reduction was also discussed.     

The interaction of glass-ionomer cements containing vinylphosphonic acid with water and aqueous lactic acid

A glass-ionomer cement containing an acrylic acid/vinyl phosphonic acid copolymer, has been investigated for its interaction with water and with aqueous lactic acid and the results compared with those from conventional glass-ionomers based on polyacrylic acid. Cylindrical specimens (12 mm high x 6 mm diameter) were placed in 8 cm3 of aqueous lactic acid (20 mmol dm(-3); pH 2.7) for 1 week, at the end of which the pH was determined. Each specimen was then placed in a fresh 8 cm3 volume of lactic acid and the pH determined after a further week. This procedure was continued for a total of 13 weeks for each specimen. Experiments were also carried out on similar specimens exposed to 8 cm3 of water for 1 week only. Further experiments were carried out in which discs of cement were exposed to thin films (0.15 mm) of lactic acid at pH 4.5, with pH values determined at 30 s, 1, 2, 5 and 10 min. After 1 week, cements had changed the pH of the lactic acid to a mean value of 3.63 (SD 0.08) while in weeks 2-13 they changed it to a mean value of 3.31 (SD 0.11). After 1 week in aqueous lactic acid the cements had gained mass by a mean of 1.26% (SD 0.59%) compared with 1.22% (SD 0.14%) in water. After 13 weeks in lactic acid, cements had lost a mean of 2.83% (SD 0.74%) in mass. Thin films of aqueous lactic acid changed from pH 4.5-5.1 at 30 s and to a steady value of 5.6 (SD 0.3) between 2 and 10 min. These results were similar to those for conventional glass-ionomer cements based on carboxylic acid polymers. Hence, it was concluded that the presence of the vinylphosphonic acid units made no significant difference to the interaction of cements with aqueous solutions.     

Immunohistochemical and ultrastructural evaluation of the effects of phosphoric acid etching on dentin proteoglycans

It has been reported that phosphoric acid (PA) produces structural and molecular alterations in dentin collagen fibrils; however, no relevant information exists on the influence of etching with PA on dentin non-collagenous macromolecules. The present study investigated, by immunohistochemistry and ultrastructural histochemistry, the behavior of dentin proteoglycans (PG) after etching human dentin samples with 35% PA gel (thickened with colloidal silica) or with a 35% PA liquid for 15, 30 and 120 s. Immunolabeling with a mouse monoclonal anti-chondroitin sulfate antibody demonstrated that glycosaminoglycans (GAG) were preserved within dentinal tubules opened to the surface after etching with PA gel. In addition, the cationic tracer polyethyleneimine, used for the ultramicroscopic localization of PG anionic sites, revealed that treatment of dentin samples with PA gel preserved the polyanionic peritubular PG in the etched area. On the other hand, etching with the PA liquid produced loss of peritubular GAG and PG anionic sites in the etched dentin surface. The results obtained indicated that similar concentrations of PA in gel or liquid formulations differently affect the organization of dentin PG. The clinical significance of these in vitro findings and the structural and molecular interactions of dentin PG with adhesive systems are still unknown.