Influence of antifungal polyenes on the adhesion of Candida albicans and Candida glabrata to human epithelial cells in vitro

Candidal adherence to mucosal surfaces is considered as the first step in the pathogenesis of oral candidiasis. We examined the effect of antifungal polyenes, amphotericin B, nystatin and natamycin, at sublethal and minimum inhibitory concentrations (MICs) on the adherence of Candida albicans and Candida glabrata to HeLa cervical carcinoma and HSC-3 oral squamous cell carcinoma cells. A total of six oral Candida isolates were used throughout the study. Two Candida strains, C. albicans (44990) and C. glabrata (MYA-275) were obtained from ATCC. Four Candida strains, C. albicans 19 and 24 and C. glabrata 15 and 21, were isolated from patients with documented Candida-associated denture stomatitis. Cells were either incubated with Candida in the presence of the drug, or pre-incubated with yeasts and exposed subsequently to the drug. In the drug-free controls, the mean number of C. albicans yeasts associated with HeLa cells obtained from all experiments (130.1±10.1 yeasts/mm²) was significantly greater than that for HSC-3 cells (114.7±10.1 yeasts/mm²; P<0.025). For C. glabrata, the mean adherence to HeLa and HSC-3 cells was 84.4±5.5 and 84.4±3.3 yeasts/mm², respectively, and these values were not statistically different (P>0.4). Candidal adherence was significantly reduced when the tested polyenes were present during the “adherence phase”. The obtained values were significantly different from the controls, except for the effect of nystatin at the MIC on the adherence of C. glabrata strain MYA-275 to HeLa cells (P<0.375). Amphotericin B had the highest effect against both Candida species, reducing adherence by 50 and 60%, at the MIC and sublethal concentrations, respectively. The susceptibility of cell-associated Candida to polyenes was decreased markedly and the treatment did not result in significant detachment of adherent yeasts. The reduction in adherence was between 2 and 10%, when compared to the drug-free controls. These findings suggest that sub-therapeutic levels of polyenes that are likely to persist in the oral cavity following topical treatment may modulate candidal colonization when present during the “adherence phase”.     

人牙周膜细胞中内源性骨形成蛋白的流式细胞仪分析

目的：定量检测和分析人牙周膜细胞（ＰＤＬＣ）表达内源性骨形成蛋白（ＢＭＰ）的情况。方法：应用ＢＭＰ单克隆抗体，通过流式细胞仪和免疫组化ＡＢＣ的方法双重判定。结果：在离体培养的人ＰＤＬＣ中有一半左右的细胞能表达ＢＭＰ。结论：牙周膜细胞具有一定的合成和分泌ＢＭＰ的能力；可以进一步认为人的牙周膜细胞是具有成骨潜能的，在牙周组织再生中有积极作用。     

正常大鼠颌下腺上皮细胞极性培养

目的为了探索简便、有效的涎腺上皮细胞的体外培养方法。方法采用自制鼠尾胶原胶为底物．在培养液中加入一些促进上皮细胞生长分化的刺激物，对出生一天的Wistar大鼠颌下腺上皮细胞进行原代培养。通过相差显微微镜、光镜及透射电镜对上皮细胞的生长及分化进行观察和研究。结果培养的大鼠颌下腺上皮细胞呈多层生长且为极性分化，保留了腺泡导管分泌单位的三种上皮成份。结论本研究所采用的方法是一种简便、可行、有效的涎腺上皮细胞的体外培养方法，其中自制胶原胶是本研究培养成功的关键。     

In-situ resistance measurements of Nafion® 117 membranes in polymer electrolyte fuel cells

The resistance of the Nafion® 117 membrane in $\text{H}{}_2\text{O}{}_2$ and $\text{H}{}_2\text{air}$ polymer electrolyte fuel cells (PEFCs) has been measured in situ using fast current pulses. The dependence of the membrane resistance on current density, temperature, pressure and flow-field design was investigated. It was found that, independent of other variations, the resistance increases with increasing current density. When the current density in the cell is increased from 0.2 to 0.7 A cm^?2, the membrane resistance increases by up to 22%. Even on open circuit the resistance at 60°C is 15%–35% higher than that measured ex situ, indicating that the membrane is not fully hydrated under the fuel cell operating conditions. The resistance on open circuit also depends on the design of the flow field. In a design with forced gas convection the resistance at 60°C is substantially higher (210 mΩ cm²) than in a design without forced convection (186 mΩ cm²).     

脂肪干细胞在骨软骨组织工程中的应用研究

种子细胞一直是骨软骨组织工程研究的焦点.近年来,脂肪干细胞由于具有多种优点而逐渐成为组织工程的种子细胞.本文就脂肪干细胞的概述、体外分化能力和表面标志、体内实验的研究进展作一综述.     

差速传代纯化大鼠牙囊细胞

目的:建立一种简捷的分离培养和纯化大鼠牙囊细胞的方法。方法:分离出生后6dSD大鼠上下颌第一和第二磨牙完整牙胚,剥离牙囊和成釉器,剪碎后酶消化并混合培养,再利用多次差速传代纯化牙囊细胞。结果:原代细胞为牙囊细胞和成釉器细胞混合生长,差速传代培养到第4代可获得纯化的牙囊细胞。倒置显微镜下观察牙囊细胞呈长梭形或三角形,免疫组化染色抗波形丝蛋白阳性,抗角蛋白阴性。结论:利用多次差速传代可从混合培养的原代细胞中获得纯化的牙囊细胞。     

Calcium ion release from calcium hydroxide stimulated fibronectin gene expression in dental pulp cells and the differentiation of dental pulp cells to mineralized tissue forming cells by fibronectin

Aim The effect of calcium ions on dental pulp cells was examined and the mechanism of dentine bridge formation by calcium hydroxide was investigated. Methodology Human dental pulp cells were treated with high concentration of calcium or magnesium ions for 24 h and fibronectin gene expression was measured by the quantitative PCR method. Human dental pulp cells were then cultured on fibronecin‐coated dishes for 24 h, and osteocalcin and osteopontin gene expression, which are typical phenotypes of mineralized tissue forming cells, were measured by the quantitative PCR method. Results Fibronectin gene expression was stimulated by calcium ions dose‐dependently. On the other hand, magnesium ions did not influence fibronectin gene expression. Furthermore, pulp cells cultured on fibronectin‐coated dishes enhanced the expression of phenotypes of mineralized tissue forming cells. Conclusions Calcium ions released from calcium hydroxide stimulates fibronectin synthesis in dental pulp cells. Fibronectin might induce the differentiation of dental pulp cells to mineralized tissue forming cells that are the main cells to form dentine bridges, via contact with cells.     

大鼠舌背上皮细胞体外培养及其生物学特性观察

目的:探讨舌背上皮细胞体外培养的可行性,并观察其生长特性。方法:断颈处死出生后1d的SD大鼠,70%乙醇浸泡3～5min,切取舌体及下颌骨。以DMEM/F12作为基础培养液,原代培养舌背黏膜上皮。当细胞铺满整个培养瓶底70%时,进行细胞传代。采用广谱角蛋白细胞免疫化学染色法及透射电镜观察法对上皮细胞进行鉴定。结果:接种时,原代细胞形状、大小不等,呈多样性,表现为多角状扁平细胞、体积较大的球形细胞和体积较小的球形细胞。大多数细胞在培养24h后贴壁;培养3d后,细胞增殖形成许多小而不规则的细胞克隆或集落,开始进入指数增殖阶段,形成细胞团块。随着时间推移,细胞团块周围结构疏松,间隙增大,细胞团块不断增大,融合、连接成片,排列成铺路石状,可传3～4代。结论:以DMEM/F12为基础培养液,可成功地培养出舌背上皮细胞。