• Title/Summary/Keyword: mediated effect

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The Effect of Youth's Experience of School Violence on Cyber Violence -Focus on the Multiple Mediating Effects of Human Rights Sensitivity and Peer Conformity- (청소년의 학교폭력 경험이 사이버폭력에 미치는 영향 - 인권감수성과 또래동조성의 다중매개효과를 중심으로 -)

  • Kim, Jung-Ae
    • The Journal of the Korea Contents Association
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    • v.21 no.5
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    • pp.446-464
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    • 2021
  • The purpose of this study is to verify the multi-mediated effects of human rights sensitivity and peer-coordination in the relationship between teenagers' school violence experience and cyberbullying in order to find alternatives to prevent cyberbullying as teenagers increase their use of smartphones. In order to achieve this research goal, four middle schools were selected by the education office located in downtown Busan and analyzed on 908 middle school students. The results of the study are as follows. First, school violence experiences have been shown to affect cyberbullying. Second, the experience of abuse and neglect during school violence affected human rights sensitivity, but the experience of damage did not affect human rights sensitivity. Third, among school violence experiences, the experience of damage and abuse influenced peer co-operation, but the experience of sitting on the sidelines did not affect peer co-operation. Fourth, human rights sensitivity affected cyberbullying. Fifth, peer groupings affected cyberbullying. Sixth, human rights sensitivity influenced peer-reaction. Seventh, among human rights sensitivities, bystander experience and cyberbullying were found to be mediating bystander experience and cyberbullying, but the damage experience and abuse experience did not have a mediating effect in human rights sensitization and cyberbullying. Eighth, peer cooperation was found to be mediating cyberbullying, but there was no mediating effect between on-the- sidelines experience and cyberbullying. Ninth, human rights sensitivity and peer creation are shown to mediate the relationship between on-the- sidelines experience and cyberbullying sequentially. However, human rights sensitivity and peer creation did not mediate cyberbullying sequentially between the experience of damage and the experience of perpetration. The implications of this study were to verify the effects of teenagers' school violence damage experience, abuse experience, and bystander experience on cyberbullying, and multiple interventions of human rights sensitivity and peer group.

How Male and Female Job Seekers Differently React to Favorable/Unfavorable Diversity Cue on Job Postings (채용 공고에 제시된 유리/불리 다양성 단서에 대한 남성과 여성 구직자의 반응 차이)

  • Taekyeong Lee;Hyewon Lee;Jakyung Seo;Jeong Ryu;Young Woo Sohn
    • Science of Emotion and Sensibility
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    • v.26 no.2
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    • pp.67-84
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    • 2023
  • Gender diversity policies aim to reduce institutional discrimination in a male-dominated society and the underutilization of women in terms of the economy. Extant gender diversity literature has focused on gender diversity policies premised on women being treated as a minority. However, since women-centered occupational groups do exist, women cannot be considered an absolute minority. Therefore, we explored the gender difference in job seekers' reactions to a diversity policy favorable to men. The experiment divided participants into 2 (Gender: Male, Female) × 2 (Diversity: Favorable, Unfavorable), canvassing 329 college students (156 male, 173 female). Participants evaluated the organizational justice and organizational attractiveness of the virtual company by looking at the diversity cues presented in the job posting seeking new employees. As a result, it was confirmed that if the diversity cues presented in the job posting were favorable (vs. unfavorable) to the individual, the organization's distribution justice and procedural justice perceptions were generated differently according to the gender of the job seeker. Moreover, female job seekers perceived distribution justice and procedural justice as higher than male job seekers when they encountered diversity cues that were favorable (vs. unfavorable) to them. In addition, the relationship between diversity cues and organizational attractiveness was mediated by the perception of organizational justice, and this mediating effect was moderated by gender. For women, on the one hand, the mediating effect through the perception of distributive justice and procedural justice was significant in the relationship between diversity cues and organizational attractiveness. On the other hand, the mediating effect alone through the perception of procedural justice was significant for men. Our findings suggest that identical diversity managements are distinguished by individuals' social status or affiliation and may even result in differentiated behaviors.

The Effects of Isopropyl 2-(1,3-dithioetane-2-ylidene)-2-[N-(4-methyl-thiazol-2-yl)carbamoyl]acetate (YH439) on Potentiated Carbon Tetrachloride Hepatotoxicity (상승적 화학적 간독성에 미치는 YH439의 영향)

  • Kim, Sang-Geon;Cho, Joo-Youn
    • The Korean Journal of Pharmacology
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    • v.32 no.3
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    • pp.407-416
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    • 1996
  • The reactive intermediates formed during the metabolism of therapeutic agents, toxicants and carcinogens by cytochromes P450 are frequently capable of covalently binding to tissue macromolecules and causing tissue damage. It has been shown that YH439, a congener of malotilate, is effective in suppressing hepatic P450 2E1 expression. The present study was designed to further establish the mechanistic basis of YH439 protection against toxicant by assessing its effects against chemical-mediated potentiated hepatotoxicity. Retinoyl palmitate (Vit-A) pretreatment of rats for 7 days substantially enhanced carbon tetrachloride hepatotoxicity, as supported by an ${\sim}5-fold$ increase in serum alanine aminotransferase (ALT) activity, as compared to $CCl_4$ treatment alone. The elevation of ALT activity due to Vit-A was completely blocked by the treatment of $GdCl_3$ a selective inhibitor of Kupffer cell activity. Concomitant pretreatment of rats with both YH439 and Vit-A resulted in a 94% decrease in Vit-A-potentiated $CCl_4$ hepatotoxicity. YH439 was also effective against propyl sulfide-potentiated $CCl_4-induced$ hepatotoxicity. Whereas propyl sulfide (50 mg/kg, 7d) enhanced $CCl_4-induced$ hepatotoxicity by >5-fold, relative to $CCl_4$ treatment alone, concomitant treatment of animals with both propyl sulfide and YH439 at the doses of 100 and 200 mg/kg prevented propyl sulfide-potentiated $CCl_4$ hepatotoxicity by 35% and 90%, respectively. Allyl sulfide, a suppressant of hepatic P450 2E1 expression, completely blocked the propyl sulfide-enhanced hepatotoxicity, indicating that propyl sulfide potentiation of $CCl_4$ hepatotoxicity was highly associated with the expression of P450 2E1 and that YH439 blocked the propyl sulfide-enhanced hepatotoxicity through modulation of P450 2E1 levels. Propyl sulfide- and $CCl_4-induced$ stimulation of lipid peroxidation was also suppressed by YH439 in a dose-related manner, as supported by decreases in malonedialdehyde production. The role of P450 2E1 induction in the potentiation of $CCl_4$ toxicity and the effects of YH439 were further evaluated using pyridine as a P450 2E1 inducer. Pyridine pretreatment substantially enhanced the $CCl_4$ hepatotoicity by 23-fold, relative to $CCl_4$ alone. YH439, however, failed to reduce the pyridine-potentiated toxicity, suggesting that the other form(s) of cytochroms P450 inducible by pyridine, but not suppressible by YH439 treatment, may play a role in potentiating $CCl_4-induced$ hepatotoxicity. YH439 was capable of blocking cadmium chloride-induced liver toxicity in mice. These results demonstrated that YH439 efficiently blocks Vit-A-enhanced hepatotoxiciy through Kupffer cell inactivation and that the suppression of P450 2E1 expression by YH439 is highly associated with blocking of propyl sulfide-mediated hepatotoxicity.

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Protective Effect of Plantago asiatica L. Leaf Ethanolic Extract Against Ferric Nitrilotriacetate-Induced Prostate Oxidative Damage in Rats (랫드에서의 Fe-NTA 유발 산화스트레스에 대한 차전초 에탄올 추출물의 전립선보호 효과)

  • Hong, Seung-Taek;Hong, Chung-Oui;Nam, Mi-Hyun;Ma, Yuan-Yuan;Hong, Yun-Jin;Son, Da-Hee;Chun, Su-Hyun;Lee, Kwang-Won
    • Journal of Food Hygiene and Safety
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    • v.26 no.3
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    • pp.260-265
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    • 2011
  • Plantago asiatica L. (P. asiatica) has been used as one of the popular folk medicines in Asia for human health care practices. Various activities of P. asiatica have been reported, such as anti-oxidant, anti-glycation, anti-inflammatory and hepatoprotective activity. Therefore, the potential of P. asiatica to reduce oxidative stress has been studied in several ways for over 20 years, especially at liver and kidney. However no investigation has been reported revealing its protective effect on prostate. Method: Treatment of P. asiatica leaf ethanolic extract (PLE) (1 g/kg body weight (b.w.), 2 g/kg b.w., or 4 g/kg b.w.) were given separately to animals for pretreatment once per day for 7 days, and on the seventh day ferric nitrilotriacetate (Fe-NTA; 0.24 mmol Fe/kg b.w.), which is known as an oxidative stress-inducer at prostate, was administrated by i.p to negative control group. At the end of the study period, dissection was carried out for detecting the prostate protective effect of PLE. Result: Fe-NTA-treated animals produced reactive oxygen species (ROS) resulting in depletion of antioxidant biomaker, such as glutathione (GSH), glutathione reductase (GR), and glutathione s-transferase (GST) and increase of lipid peroxidation in prostate. However, PLE pretreatment resulted in an increase in the GSH, GST and GR levels concentration dependent manner and in an significant decrease in the levels of lipid peroxidation. Conclusion: Our data suggest that PLE may be effective in protecting oxidative stress-induced damage of prostate, and PLE may be an chemopreventive agent against Fe-NTA-mediated prostate oxidative damage.

Protective Effect of Plantago asiatica L. Extract Against Ferric Nitrilotriacetate (Fe-NTA) Induced Renal Oxidative Stress in Wistar Rats (차전초 추출물을 투여한 랫드에서의 Fe-NTA 유발 산화스트레스에 대한 신장보호 효과)

  • Hong, Chung-Oui;Hong, Seung-Teak;Koo, Yun-Chang;Yang, Sung-Yong;Lee, Ji-Young;Lee, Yanhouy;Ha, Young-Min;Lee, Kwang-Won
    • Journal of Food Hygiene and Safety
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    • v.26 no.2
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    • pp.107-113
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    • 2011
  • Plantago asiatica L. (PA), which is widely distributed in Korea, Japan and China, has traditionally been used as a popular folk medicine for the treatment of liver diseases. A variety of activities of PA was reported, that is hepatoprotective, anti-inflammatory, anti-glycation and anti-oxidant effect. Ferric nitrilotriacetate (Fe-NTA) is a potent nephrotoxic agent and has been reported to induce renal proximal tubular necrosis. In the present study, pre-treatment with PA extract (PAE) in Wistar rat followed by Fe-NTA i.p. treatment (13.5 mg Fe/kg body weight) was performed to detect the renal protective effect of PAE. Only Fe-NTA treated group showed increases in the level of serum blood urea nitrogen (BUN) and serum creatinine (Cr), and renal tissue malondialdehyde (MDA), product of lipid peroxidation. Moreover, the level of biomarkers indicate the antioxidants status, reduced glutathione (GSH), glutathione-S-transferase (GST) and glutathione reductase (GR) were decreased. However, PAE pre-treated group showed decreases in the levels of serum BUN, serum Cr and renal tissue MDA in concentration dependent manner and increases in the level of GSH, GST and GR. These results are significantly different (p < 0.05) to the other groups. Our data suggest that PAE may be used as an chemopreventive material against Fe-NTA-mediated renal oxidative stress.

Effect of Retrovirus Mediated TNF-$\alpha$ Gene Transfer to Tumor Necrosis Factor(TNF) Sensitive Tumor Cell Lines on Sensitivity to TNF (Retroviral Vector를 이용한 TNF-$\alpha$ 유전자의 이입이 암세포의 종양괴사인자(TNF) 감수성에 미치는 효과)

  • Oh, Yeon-Mok;Park, Kyeo-Yeong;Jung, Man-Pyo;Yoo, Chul-Gyu;Kim, Young-Whan;Han, Sung-Goo;Sim, Young-Soo;Han, Yong-Chol
    • Tuberculosis and Respiratory Diseases
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    • v.41 no.2
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    • pp.87-96
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    • 1994
  • Background : Since tumor necrosis factor was discovered in 1975, TNF has been well known about its cytotoxic effect on tumor cells in vivo and in vitro. According to the recent improvement of molecular biological techinques, it is possible that exogenous TNF gene is transferred to tumor cells and is expressed in theirs. By virtue of TNF gene transfer, we have expected that TNF expressed in TNF-gene-transferred tumor cells would kill tumor cells in vivo without systemic side effect. The expected mechanisms in which antitumor effects of TNF expressed in TNF-gene-transferred tumor cells are working would be as followings. In the first mechanism, TNF expressed in TNF-gene-transferred tumor cells would kill tumor cells around(like homicide). In the second mechanism, TNF expressed in TNF-gene-transferred tumor cells would kill themselves(like suicide). In the third mechanism, TNF expressed in TNF-gene-transferred tumor cells would recruit immune effector cells and kill tumor cells indirectly. In the last mechanism, TNF expressed in TNF-gene-transferred tumor cells would augment cytokine such as interferon-$\gamma$ to kill tumor cells. Among these four mechanisms of antitumor effect, only the second mechanism has not been established yet. Therefore, to elucidate the second mechanism, We performed this study. Method : We transferred TNF-$\alpha$ gene to NCI-H2058, a human mesothelioma cell line and WEHI164, a murine fibrosarcoma cell line by using retroviral vector(pLT12SNTNF). And, We determined by using MTT assay whether TNF expressed in TNF-gene-transferred tumor cell lines would kill themselves like suicide or not. Then, if TNF-gene-transferred tumor cell lines would not suicide themselves, I would know more about the TNF sensitivity of TNF-gene-transferred tumor cell lines to exogenous TNF also by MTT assay. Result : NCI-H2058 and WEHI164 which were sensitive to TNF, became far less sensitive to endogenous and exogenous TNF after being transferred TNF-$\alpha$ gene to. Conclusion : TNF-gene-transfer to NCI-H2058 and WEHI164 gave them resistance to TNF.

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Implementation Strategy for the Elderly Care Solution Based on Usage Log Analysis: Focusing on the Case of Hyodol Product (사용자 로그 분석에 기반한 노인 돌봄 솔루션 구축 전략: 효돌 제품의 사례를 중심으로)

  • Lee, Junsik;Yoo, In-Jin;Park, Do-Hyung
    • Journal of Intelligence and Information Systems
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    • v.25 no.3
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    • pp.117-140
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    • 2019
  • As the aging phenomenon accelerates and various social problems related to the elderly of the vulnerable are raised, the need for effective elderly care solutions to protect the health and safety of the elderly generation is growing. Recently, more and more people are using Smart Toys equipped with ICT technology for care for elderly. In particular, log data collected through smart toys is highly valuable to be used as a quantitative and objective indicator in areas such as policy-making and service planning. However, research related to smart toys is limited, such as the development of smart toys and the validation of smart toy effectiveness. In other words, there is a dearth of research to derive insights based on log data collected through smart toys and to use them for decision making. This study will analyze log data collected from smart toy and derive effective insights to improve the quality of life for elderly users. Specifically, the user profiling-based analysis and elicitation of a change in quality of life mechanism based on behavior were performed. First, in the user profiling analysis, two important dimensions of classifying the type of elderly group from five factors of elderly user's living management were derived: 'Routine Activities' and 'Work-out Activities'. Based on the dimensions derived, a hierarchical cluster analysis and K-Means clustering were performed to classify the entire elderly user into three groups. Through a profiling analysis, the demographic characteristics of each group of elderlies and the behavior of using smart toy were identified. Second, stepwise regression was performed in eliciting the mechanism of change in quality of life. The effects of interaction, content usage, and indoor activity have been identified on the improvement of depression and lifestyle for the elderly. In addition, it identified the role of user performance evaluation and satisfaction with smart toy as a parameter that mediated the relationship between usage behavior and quality of life change. Specific mechanisms are as follows. First, the interaction between smart toy and elderly was found to have an effect of improving the depression by mediating attitudes to smart toy. The 'Satisfaction toward Smart Toy,' a variable that affects the improvement of the elderly's depression, changes how users evaluate smart toy performance. At this time, it has been identified that it is the interaction with smart toy that has a positive effect on smart toy These results can be interpreted as an elderly with a desire to meet emotional stability interact actively with smart toy, and a positive assessment of smart toy, greatly appreciating the effectiveness of smart toy. Second, the content usage has been confirmed to have a direct effect on improving lifestyle without going through other variables. Elderly who use a lot of the content provided by smart toy have improved their lifestyle. However, this effect has occurred regardless of the attitude the user has toward smart toy. Third, log data show that a high degree of indoor activity improves both the lifestyle and depression of the elderly. The more indoor activity, the better the lifestyle of the elderly, and these effects occur regardless of the user's attitude toward smart toy. In addition, elderly with a high degree of indoor activity are satisfied with smart toys, which cause improvement in the elderly's depression. However, it can be interpreted that elderly who prefer outdoor activities than indoor activities, or those who are less active due to health problems, are hard to satisfied with smart toys, and are not able to get the effects of improving depression. In summary, based on the activities of the elderly, three groups of elderly were identified and the important characteristics of each type were identified. In addition, this study sought to identify the mechanism by which the behavior of the elderly on smart toy affects the lives of the actual elderly, and to derive user needs and insights.

An Exploratory Study on the Effects of Relational Benefits and Brand Identity : mediating effect of brand identity (관계혜택과 브랜드 동일시의 역할에 관한 탐색적 연구: 브랜드 동일시의 매개역할을 중심으로)

  • Bang, Jounghae;Jung, Jiyeon;Lee, Eunhyung;Kang, Hyunmo
    • Asia Marketing Journal
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    • v.12 no.2
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    • pp.155-175
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    • 2010
  • Most of the service industries including finance and telecommunications have become matured and saturated. The competitions have become severe while the differences among brands become smaller. Therefore maintaining good relationships with customers has been critical for the service providers. In case of credit card and debit card, the similar patterns are shown. It is important for them to maintain good relationships with customers, and therefore, they have used marketing program which provides customized services to customers and utilizes the membership programs. Not only do they build and maintain good relationships, but also highlight their brands from the emotional aspects. For example, KB Card or Hyundai Card uses well-known designers' works for their credit card design. As well, they differentiate the designs of credit cards to stress on their brand personalities. BC Card introduced the credit card with perfume that a customer would like. Even though the credit card is small and not shown to public easily, it becomes more important for those companies to touch the customers' feelings with the brand personalities and their images. This is partly because of changes in consumers' lifestyles. Y-generations becomes highly likely to express themselves in many different ways and more emotional than X-generations. For the Y-generations, therefore, even credit cards in the wallet should be personalized and well-designed. In line with it, credit cards with good design can be seen as an example of brand identity, where different design for each customer can be used to recognize the membership groups that customers want to belong. On the other hand, these credit card companies offer the special treatment benefits for those customers who are heavy users for the cards. For example, those customers who love sports will receive some special discounts when they use their credit cards for sports related products. Therefore this study attempted to explore the relationships between relational benefits, brand identification and loyalty. It has been well known that relational benefits and brand identification lead to loyalty independently from many other studies, but there has been few study to review all the three variables all together in a research model. Furthermore, as reviewed above, in the card industry, many companies attempt to associate the brand image with their products to fit their customers' lifestyles while relational benefits are still playing an important role for their business. Therefore in our research model, relational benefits, brand identification, and loyalty are all included. We focus on the mediating effect of brand identification. From the relational benefits perspective, only special treatment benefit and confidence benefit are included. Social benefit is not applicable for this credit card industry because not many cases of face-to-face interaction can be found. From the brand identification perspective, personal brand identity and social brand identity are reviewed and included in the model. Overall, the research model emphasizes that the relationships between relational benefits and loyalty will be mediated by the effect of brand identification. The effects of relational benefits which are confidence benefit and special treatment benefits on loyalty will be realized when they fit to the personal brand identity and social brand identity. In the research model, therefore, the relationships between confidence benefit and social brand identity, and between confidence benefit and personal identity are hypothesized while the effects of special treatment benefit on social brand identity and personal brand identity are hypothesized. Loyalty, then, is hypothesized to have positive relationships with personal brand identity and social brand identity. In addition, confidence benefit among the relational benefits is expected to have a direct, positive relationship with loyalty because confidence benefit has been recognized as a critical factor for good relationships and satisfaction. Data were collected from college students who have been using either credit cards or debit cards. College students were regarded good subjects because they are in Y-generation cohorts and have tendency to express themselves more. Total sample size was two hundred three at the beginning, but after deleting those data with many missing values, one hundred ninety-seven data points were remained and used for the model testing. Measurement items were brought from the previous literatures and modified for this research. To test the reliability, using SPSS 14, chronbach's α was examined and all the values were from .874 to .928 exceeding over .7. Using AMOS 7.0, confirmatory factor analysis was conducted to investigate the measurement model. The measurement model was found good fit with χ2(67)=188.388 (p= .000), GFI=.886, AGFI=.821, CFI=.941, RMSEA=.096. Using AMOS 7.0, structural equation modeling has been used to analyze the research model. Overall, the research model fit were χ2(68)=188.670 (p= .000), GFI=.886, AGFI=,824 CFI=.942, RMSEA=.095 indicating good fit. In details, all the paths hypothesized in the research model were found significant except for the path from social brand identity to loyalty. Personal brand identity leads to loyalty while both confidence benefit and special treatment benefit have a positive relationships with personal and social identities. As well, confidence benefit has a direct positive effect on loyalty. The results indicates the followings. First, personal brand identity plays an important role for credit/debit card usage. Therefore even for the products which are not shown to public easy, design and emotional aspect can be important to fit the customers' lifestyles. Second, confidence benefit and special treatment benefit have a positive effects on personal brand identity. Therefore it will be needed for marketers to associate the special treatment and trust and confidence benefits with personal image, personality and personal identity. Third, this study found again the importance of confidence and trust. However interestingly enough, social brand identity was not found to be significantly related to loyalty. It can be explained that the main sample of this study consists of college students. Those strategies to facilitate social brand identity are focused on high social status groups while college students have not been established their status yet.

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Anti-inflammatory effect of Sinhyowoldo-san Extract with regard to Pro-inflammatory Mediators in PMA plus A23187-induced Human Mast Cells (인간 비만세포에서 PMA와 A23187에 의해 유도된 전염증 매개체에 대한 신효월도산 추출물의 항염증 효과)

  • Wi, Gyeong;Yang, Da-Wun;Kang, Ok-Hwa;Kim, Sung-Bae;Mun, Su-Hyun;Seo, Yun-Soo;Kang, Da-Hye;Lim, Jae-Soo;Kim, Ma-Ryong;Kwak, Nam-Won;Kong, Ryong;Kwon, Dong-Yeul
    • The Korea Journal of Herbology
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    • v.29 no.6
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    • pp.117-123
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    • 2014
  • Objectives : Sinhyowoldo-san (SHWDS) is said to be a traditional medicine used for shigellosis, abdominal pain, diarrhea. But mechanism of SHWDS mediated-modulation of immune function is not sufficiently understood. To ascertain the molecular mechanisms of SHWDS 70% EtOH extract on pharmacological and biochemical actions in inflammation, we researched the effect of pro-inflammatory mediators in phorbol-12-myristate-13-acetate (PMA)+ A23187-activated human mast cell line (HMC-1). Methods : In the present research, cell viability was measured by MTS assay. pro-inflammatory cytokine production was measured by performing enzyme-linked immunosorbent assay (ELISA), reverse transcription polymerase chain reaction (RT-PCR), and western blot analysis to analyze the activation of mitogen-activated protein kinases (MAPKs), nuclear factor kappa-light-chain-enhancer of activated B cells ($NF-{\kappa}B$). The investigation focused on whether SHWDS inhibited the expressions of interleukin-6 (IL-6), interleukin-8 (IL-8), MAPKs and $NF-{\kappa}B$ in PMA+A23187-activated HMC-1 cells. Results : SHWDS has no cytotoxicity at measured concentration (50, 100, and $250{\mu}g/ml$). SHWDS ($250{\mu}g/ml$) inhibits pro-inflammatory cytokine expression in PMA+ A23187-activated HMC-1 cells. Moreover, SHWDS inhibited cyclooxygenase (COX)-2 expression. In activated HMC-1 cells, SHWDS suppressed phosphorylation of extracellular signal-regulated kinase (ERK 1/2) and c-jun N-terminal Kinase (JNK 1/2). Then, SHWDS suppressed activation of nuclear factor $NF-{\kappa}B$ in nuclear, degradation of IkB ${\alpha}$ in cytoplasm. Conclusions : We propose that SHWDS has an anti-inflammatory therapeutic potential, which may result from inhibition of ERK 1/2, JNK 1/2 phosphorylation and $NF-{\kappa}B$ activation, thereby decreasing the expression of pro-inflammatory genes.

Effects of ${\alpha}_1-Adrenergic$ Stimulation on Membrane Potential, Twitch Force, Intracellular $Na^+,\;and\;H^+$ Activity in Hyperthyroid Guinea Pig Ventricular Muscle (갑상선 기능 항진 기니픽 심근에서 ${\alpha}_1-Adrenergic$ 수용체 자극이 막전위, 수축력 및 세포내 $Na^+$$H^+$ 활성도에 미치는 영향)

  • Kim Jin-Sang;Chae Soo-Wan;Cho Kyu-Park
    • The Korean Journal of Pharmacology
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    • v.31 no.1 s.57
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    • pp.39-51
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    • 1995
  • The roles of ${\beta}-adrenoceptor$ were well known in hyperthyroidal heart, but not with ${\alpha}-adrenoceptor$. So we studied the effects of phenylephrine on membrane potential, intracellular sodium activity ($a^{i}_{Na}$), twitch force, and intracellular pH ($pH_i$) by continuous intracellular recordings with ion-selective and conventional microelectrodes in the papillary muscles of hyperthyroid guinea pig heart. ${\alpha}_1-adrenoceptor$ stimulation by phenylephrine (10^{-5}\;or\;3{\times}10^{-5}M$) produced the following changes: variable changes in action potential duration, a hyperpolarization ($1.5{\pm}0.1mM$) of the diastolic membrane potential, an increase in $a^{i}_{Na}\;(0.4{\pm}0.15mM)$, a stronger positive inotropic effect ($220{\pm}15%$), an increase in $pH_i\;(0.06{\pm}0.002\;unit)$. These changes were flocked by prazosin and atenolol. This indicated that the changes in membrane potential, $a^{i}_{Na}$ twitch force, and $pH_i$ are mediated by a stimulation of the ${\alpha}_1-adrenoceptor$. Ethylisopropylamiloride ($10^{-5}$) also blocked the increase in $a^{i}_{Na}$ and twitch force. On the other hand, strophanthidin, tetrodotoxin, $Cs^+$ or verapamil did not block the increase in $a^{i}_{Na}$ and twitch force. Thus, it was suggested that ${\alpha}_1-adrenoceptor$ stimulation increased $a^{i}_{Na}\;and\;pH_i$ by stimulation of $Na^{+}-H^{+}$ exchange, thereby allowing intracellular alkalinization and $a^{i}_{Na}$ increase. These results were very different from euthyroidal heart which showed ${\alpha}_1-adrenoceptor$-induced decrease in $a^{i}_{Na}$ and initial negative inotropic effect. From the above results, it was concluded that ${\alpha}_1-adrenoceptor$ had a important role in hyperthy-roidal heart.

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