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GIS (Gas Insulated Switchgear) is used in electric power system to insure non conductivity, breaking capacity and operating reliability. In the present study, dynamic analysis on the closing resistors of the GIS has bees carried out by the commercial dynamic analysis code COSMOS MOTION and 3-D modeling program SOLID WORKS. In order to find the minimum value of chatter vibration of closing resistors, the motion of moving and fixed resistor parts of closing resistors were simulated by varying the spring constant, the damping coefficient and the mass of moving and fixed resistor parts. The simulated results were compared with experimental results. The application of the results could reduce chatter vibration of closing resistors of the GIS. These data are also useful on the development of future model GIS with minimum chatter vibration for the determinations of the spring constant, the damping coefficient and mass of a moving part.

The purpose of this study was to examine whether the sonicated extract of Enterococcus faecalis (SEF) alters the cell cycle transition of lymphocytes and thus regulates the fate of the arrested cells. Human lymphocytes were activated by phytohemagglutinin in the presence or absence of SEF, and cell cycle was assessed by flow cytometry. Seventy-two hours after activation with phytohemagglutinin, cells were activated from G0/G1 to S (6.1%) and G2/M (3.8%) phases of the cell cycle. In contrast, pretreatment with SEF resulted in 90.5% of cells remaining in G0/G1, and cell cycle progression to the S and G2/M phases was consequently inhibited. Caspase assay demonstrated that SEF-treated cells exhibited significantly increased apoptosis (56.7%) compared with phytohemagglutinin alone (28.1%). We propose that if this irreversible cell cycle arrest induced by E. faecalis occurs in vivo, it may result in local immunosuppression and contribute to the pathogenesis of endodontic failure. Our findings that E. faecalis can inhibit lymphocyte responses may be of particular relevance to the pathogenesis of endodontic failure. Although the immunologic mechanism involved in the pathogenesis of persistent periapical lesion is not clearly defined, it is reasonable to predict that the altered immune reaction may be linked to the immunosuppressive potential of E. faecalis or other oral bacteria.

This study was undertaken to investigate the capacity of polymorphonuclear neutrophils (PMNs) to secrete Macrophage Inflammatory Protein (MIP)-1alpha and MIP-1beta after stimulation with Porphyromonas endodontalis lipopolysaccharide (LPS). Escherichia coli LPS was used as a positive control. Venous blood was collected and PMNs were isolated from healthy volunteers. Cells were cultured with various concentrations of LPS for different periods of time. Cell supernatants were assayed by enzyme-linked immunosorbent assay. The levels of chemokine secretion in PMNs stimulated with each LPS were found to be significantly higher than in the unstimulated control cells (p0.05), and this expression occurred in a time- and dose-dependent manner. E. coli LPS induced higher levels of cytokines than P. endodontalis LPS. These findings demonstrated that P. endodontalis LPS is capable of stimulating PMNs to produce chemotactic cytokines and suggested that PMNs stimulated with P. endodontalis LPS may play a crucial role in the inflammatory and immunopathological reactions of pulpal and periapical diseases.

The objective of this study was to investigate the expression of surface markers on T lymphocytes and the Th1/Th2 immune response in pulpal inflammation associated with specific bacteria. Pulpal inflammation was experimentally induced in rat mandibular incisors by drilling, without coolant, to open pulp chambers. Streptococcus mutans (S. mutans group), Porphyromonas endodontalis (P. endodontalis group), and a sterile cotton pellet only (control group) were inoculated in the canal. The expression of CD25 and CD54 on CD4+, and CD8+ lymphocytes in pulp tissues was determined by using a flow cytometer. The levels of interleukin (IL)-2, interferon (IFN)-gamma, and IL-4 were measured by ELISA. Flow-cytometric analysis showed that the mean ratio of CD4+:CD8+ was 0.96 in the control group, 0.99 in the S. mutans group, and 0.52 in the P. endodontalis group. An increase in CD25 and CD54 expression on CD4+ T lymphocytes was related to the bacterial infection (p0.05) and accompanied an increase in IL-2 concentration. The higher concentration of IFN-gamma than IL-4 in the P. endodontalis group suggested a Th1 reaction in the early stage of pulpal inflammation induced by P. endodontalis.

This study was undertaken to investigate immunopathologic mechanism of Enterococcus faecalis in relation to persistent apical periodontitis. We monitored the expression levels of alpha4 integrin in human polymorphonuclear neutophils (PMNs) after stimulated with sonicated extracts of E. faecalis (SEF) and compared with lipopolycaccarides (LPS) of Escherichia coli for various incubation time. Venous blood was collected from healthy volunteers and then PMNs were isolated and cultured with various concentrations of SEF for different periods of time. The levels of alpha4 integrin were measured by flow cytometry analysis. E. coli LPS group was used as a positive control and untreated PMNs as a negative control. Results showed that the expressions levels of alpha4 integrin were increased in human PMNs stimulated with E. coli LPS in comparison with unstimulated control cells (p0.05). In case of SEF stimulated group, the expression levels were decreased in time-dependent manner in comparison to E. coli LPS group (p0.05). Notably, after 12 h for incubation with SEF, the expression of alpha4 integrin was decreased in dose-dependent manner (p0.05). These findings suggest that E. faecalis seem to suppress PMNs recruiting activity by down-regulating alpha4 integrin expression, providing the possible mechanism that E. faecalis may play a crucial role in persistent apical periodontitis.

In the present authors' previous study, sonicated Enterococcus faecalis extracts were shown to suppress the cell cycle progression of human lymphocytes. To study the effect of this microorganism on the function of lymphocytes, the authors investigated the levels of interleukin-2 (IL-2) and interleukin-4 (IL-4) production by T lymphocytes before and after the addition of sonicated E. faecalis extracts. In this study, levels of IL-2 and IL-4 produced from T cells were evaluated by using the quantitative sandwich enzyme immunoassay technique. In response to phytohemagglutinin (PHA) stimulation, T cells produced increased levels of IL-2 and IL-4. However, the expressions of both cytokines were significantly inhibited when PHA-activated T cells were preexposed to 12.5 microg/ml and 25 microg/ml of sonicated E. faecalis extracts (p < 0.05). This effect was concentration-dependent, because the levels of IL-2 and IL-4 expressions were not affected by the addition of a low concentration (5 microg/ml) of sonicated extract. These findings suggest that Th1 and Th2 immunosuppression mediated by E. faecalis could be a part of the pathogenic mechanism of the endodontic failure associated with this microorganism.

The purpose of this study was to evaluate the tissue levels of matrix metalloproteinase (MMP)-1, -2, -3 and their distributions in inflamed human dental pulps and periapical lesions. Samples were subjected to enzyme-linked immunosorbent assay and/or immunohistochemistry by using specific antibodies to MMP-1, -2, and -3. Results from enzyme-linked immunosorbent assay were analyzed by using the Mann-Whitney U test and presented as p values. The concentrations of MMP-1 in all experimental groups were significantly higher than in the control (p < 0.05). The acute pulpitis and control groups were significant different in terms of their MMP-2 levels (p < 0.05). The concentration of MMP-3 in acute pulpitis was significantly higher than the control and chronic pulpitis groups (p < 0.05). Immunohistochemically, MMP-1 and MMP-3 were localized in the infiltrating neutrophils, macrophages, and extracellular matrix of the acute pulpitis group. These results suggest that MMPs play an important role in the pulp tissue destruction of acute, inflamed pulp.

Mineral trioxide aggregate (MTA) would influence healing of periapical tissues by modulating the production of growth factors and cytokines from PDL fibroblasts, however, the studies are insufficient. Therefore, the purpose of this study was to monitor the expression of transforming growth factor-beta1 (TGF- β 1), fibroblast growth factor-2 (FGF-2), and interleukin-6 (IL-6) from PDL fibroblasts in the presence of MTA. The human PDL fibroblasts were seeded onto the set MTA or IRM at a level of 1 × 10 5 cells per unit well, and further incubated for 6, 12, 24, and 48 hours. The levels of TGF-β 1, FGF-2, and IL-6 from the supernatant were measured by enzyme-linked immunosorbent assay (ELISA). The data were analyzed using one-way ANOVA. The level of TGF-β 1 was down-regulated when the cells were grown in the presence of MTA except at 6 hours. The levels of FGF-2 release were significantly suppressed when PDL fibroblasts were grown in the presence of MTA or IRM at all time intervals (p < 0.05). The expressions of IL-6 from MTA treated cells were comparable to those of untreated control cells throughout the observation periods. We presume that this material inhibits the stimulatory function of growth factors on granulation tissue formation and in turn, it promotes the healing process modulated by other bone-remodeling cells.

This in vitro study monitored MMP-8 production on PMN by stimulated with the following three groups; Sonicated extracts of E. faecalis (SEF), SEF treated with Ca(OH)2 (12.5㎎/㎖) for 7 days, and lipopolysaccharides (LPS) of E. coli. The level of MMP-8 in each group was immediately measured by ELISA. The data were analyzed with Kruskal-Wallis test and Mann-Whitney U test. In the SEF group, the level of production of MMP-8 was higher than the negative control group in low concentration (0.05㎍/㎖) of SEF (p 0.05). All of the levels in E. coli LPS were increased with increasing concentrations (p < 0.05). According to this study we could summarize as follows: 1. MMP-8 was expressed at low level in untreated PMN group and the levels of MMP-8 were upregulated in PMN stimulated by E. coli LPS groups. 2. In the SEF groups, the level of production of MMP-8 decreased with an increase in the concentration of SEF (p < 0.05). So E. faecalis may have suppressive effect on the production of MMP-8 by PMN. 3. In the case of SEF treated with Ca(OH)2, all of the MMP levels at different SEF concentrations were higher than untreated PMN group (p < 0.05), but no statistical difference was found among the differ

In order to examine the immunoresponse of host cells to Enterococcus faecalis, this in vitro study monitored the production of Interleukin-2 (IL-2), Interleukin-4 (IL-4) and Transforming growth factor-β 1 (TGF-β 1) in human lymphocytes. Lymphocytes were activated with PHA in the presence or abscence of sonicated extracts of E. Faecalis (SEF) and further incubated for 72 hours. The level of each cytokine was measured by ELISA. Data were analyzed with Kruskal-Wallis test and MannWhitney U test (P < 0.05). PHA-activated group did exhibit higher level of IL-2 and IL-4 than untreated control group. The levels of expression of both cytokines were significantly decreased following the treatment of high (25 ㎍/㎖) and medium concentration (12.5 ㎍/㎖) of SEF (P

Immunoinhibitory protein extracted from sonicated Treponema denticola have been shown to suppress cell cycle progression of human lymphocytes. To study in detail about the effect of this microorganism on the function of lymphocytes. we investigated the levels of Interleukin-2 (IL-2) and Interleukin-4 (IL-4) production by T lymphocytes before and after the addition of T. denticola sonicated extracts. In this study. levels of IL-2 and IL-4 produced from T cells pretreated with sonicated extracts were evaluated by using the quantitative sandwich enzyme immunoassay technique. In response to phytohemagglutinin (PHA) stimulation. T cell produced increased levels of IL-2 and IL-4. However. the expressions of both cytokines were significantly inhibited when PHA activated-T cells were pre-exposed to sonicated T. denticola extracts (p

Bacterial lipopolysaccharide (LPS) plays a major role in stimulating the synthesis and release of the principal osteoclast-activating cytokines, namely, interleukin 1 and tumor necrosis factor- from immune cells. Although rnonocytes/macrophages are the main producers of these cytokines, recent evidence has indicated that polymorphonuclear leukocytes (PMN) have the ability to release IL-1 and TNF-. Calcium hydroxide has been shown to be an effective medicament in root canal infections, reducing the microbial titre within the canal. It has been proposed that the therapeutic effect of Ca(OH) may also be the result of direct inactivation of LPS. The purpose of this study was to investigate whether treatment of Porphyromonas endodontalis LPS with calcium hydroxide alters its biological action as measured by human PMN secretion of IL-1 and TNF-, and it was compared with Escherichia coli LPS. P. endodontalis ATCC 35406 was cultured in anaerobic condition, and LPS was extracted using the hot-phenol water extraction method and purified. Purchased E. coli LPS was also purified. 100 /ml of each LPS in pyrogen free water were incubated with 25mg/ml Ca(OH) at 37 for 7 days. The supernatants were subjected to ultrafiltration, and the isolates were lyophilized and weighed. PMNs were obtained from peripheral blood by centrifugation layered over Lymphoprep. The cells were resuspended (410 cells/ml) in RPMI 1640 followed by treatment with various concentrations of LPS (0, 0.1, 1, 10/ml) for 24 hours at 37 in 5% incubator. The supernatants of cells were collected and the levels of IL-1, IL=1 and TNF- were measured by enzyme-linked immunosorbent assay. The results were as follows ; 1. The levels of IL-1, IL-1, TNF- from PMN treated with each LPS were significantly higher than those released from unstimulated PMN of the control group (p0.05) 3. The levels of secretion for all three cytokines were affected in a dose-dependent manner in PMN stimulated with each LPS (p0.05). 4. The levels of all three cytokines released from PMN stimulated with p. endodontalis LPS were significantly lower than those released from PMN stimulated with E coli LPS (p

방 법 실험적으로 치수의 염증반응을 일으키기 위하여 치수염의 원인균으로 알려진 Prevotella nigrescens를 이용 하였다. 실험동물의 하악절치의 incisal tip부분을 절단한 후(n=120), 치수강을 개방시켰다. 실험군에서는 Prevotella nigrescens를 멸균된 면구에 묻혀서 개방된 치수강 내에 접종하였으며, 대조군에서는 균을 접종하 지 않고 멸균된 면구만을 개방된 치수강 내에 위치시켰다. 그 후 1, 2, 5일이 경과되었을 때 실험에 사용된 치아를 발치 하여, 치수조직을 적출하였다. Amersham사의 ELISA kit를 사용하여 적출된 치수조직내의 Interleukin-6와 Interleukin-10의 양을 측정하였으며 그 결과를 Mann-Whitney rank sum test를 사용하여 통계학적 유의성을 검증 하였다. 조직학적 검사를 위해서는 발치된 치아를 nitric acid를 사용하여 탈회시킨 후 헤마톡실린-에오신 염색을 시행 한 후 관찰하였다.

Immune responses associated with bacterial infection involve various inflammatory cells. Clinical symptoms and pathologic features are particularly influenced by the predominant cells. Among inflammatory cells, T cells have the heterogenity. T cells may develop into the mature cells expressing the cell surface markers with different functions and T helper cells are categorized into Th1 and Th2 cells based on their different patterns of cytokine production. The objective of this study was to investigate the change of expression of surface markers on T cells and the Th1/Th2 immune response in pulpal inflammation associated with specific bacteria. We experimentally induced pulpal inflammation in rat incisors by drilling without coolant and innoculated with Streptococcus mutans (S.M. group), Porphyromonas endodontalis (P.E. group), or only sterile cotton (control group). After 1, 2, and 5 days, mandibular incisors were extracted and the pulp tissues were extirpated. The expressions of IL-2 recepters (CD25) and ICAM1 (CD54) on CD4+ and CD8+ cells in the pulps were determined using a flow cytometer, and the concentration of IL-2, IFN-γand IL-4 was measured by enzyme-linked immunosorbent assay. The results were as follows; 1. In the S.M. group, CD4+ cells were more increased at 2nd day than 1st day and in the P.E. group, CD8+ cells were more increased at 2nd day than 1st day. 2. The percentages of CD4+, CD4+25+ and CD4+54+ cells were decreased in the pulp tissues at 5th day after irritation in all groups. 3. The ratios of CD4+/CD8+, CD4+/CD4+25+ and CD4+/CD4+54+ in the pulps at 2nd day after irritation by P. endodontalis were significantly lower than the other groups. 4. The higher concentrations of IFN-γthan IL-4 in the pulps at 2nd day after irritation by P. endodontalis showed that T helper 1 reaction were predominant in the early stage of the pulpal inflammation induced by P. endodontalis. 5. The higher concentrations of IL-4 than IFN-γin the pulps at 1st day and 5th day after irritation by S. mutans were measured but the differences were not significant.