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MEASUREMENT ERROR BIAS IN RETURNS TO EDUCATION: EVIDENCE FROM A DEVELOPING COUNTRY - SRI LANKA
RASIKA RANASINGHE,THOMAS HERTZ 중앙대학교 경제연구소 2008 Journal of Economic Development Vol.33 No.2
There is a continuing debate about the size and direction of the bias in estimates of returns to education. Evidence from developing countries is particularly scarce. This paper addresses the problem of measurement error bias in returns to schooling for Sri Lanka, by exploiting dual measurements of reported schooling for a sub-sample of the data and deriving a reliability estimate of schooling. This is used to obtain measurement error corrected fixed effects estimates of the proportionate increase associated with an additional level of schooling. This corrected measure is 5.5%, which is less than the OLS estimate of 7.8% for two person households.
Measurement Error Bias in Returns to Education : Evidence from a Developing Country - Sri Lanka
RASIKA RANASINGHE;THOMAS HERTZ 경제연구소 2008 Journal of Economic Development Vol.33 No.2
There is a continuing debate about the size and direction of the bias in estimates of returns to education. Evidence from developing countries is particularly scarce. This paper addresses the problem of measurement error bias in returns to schooling for Sri Lanka, by exploiting dual measurements of reported schooling for a sub-sample of the data and deriving a reliability estimate of schooling. This is used to obtain measurement error corrected fixed effects estimates of the proportionate increase associated with an additional level of schooling. This corrected measure is 5.5%, which is less than the OLS estimate of 7.8% for two person households.
Immortalized gingival fibroblasts as a cytotoxicity test model for dental materials.
Illeperuma, Rasika P,Park, Young J,Kim, Jin M,Bae, Jung Y,Che, Zhong M,Son, Hwa K,Han, Mi R,Kim, Kwang M,Kim, Jin Chapman and Hall ; Kluwer Academic Publishers 2012 Journal of materials science, Materials in medicin Vol.23 No.3
<P>In vitro cytotoxicity test is an initial step to identify the harmful effects of new dental materials. Aim of this study was to develop a stable human cell line derived from normal gingival fibroblasts (hNOF) and to assess its feasibility in in vitro cytotoxicity testing. Immortalized human gingival fibroblasts (hTERT-hNOF) were successfully established with human telomerase reverse transcriptase gene transfection, preserving its phenotypical characteristics, replicative potential and biological properties. Utilizing standard cytotoxicity test modeling and dental materials, hTERT-hNOF were evaluated for their feasibility in cytotoxicity testing, compared with hNOF and L929 cells. Similar pattern of cytotoxic response was observed among hNOF, hTERT-hNOF and L929 cells. Cytotoxicity response of hTERT-hNOF was significantly similar to hNOF, moreover hTERT-hNOF and hNOF were found to be more sensitive towards the tested dental materials compared to L929 cells. This study suggested that hTERT-hNOF is an effective cytotoxic test model for dental materials.</P>
Illeperuma, Rasika P.,Kim, Do Kyeong,Park, Young Jin,Son, Hwa Kyung,Kim, Jue Young,Kim, Jinmi,Lee, Doo Young,Kim, Ki‐,Yeol,Jung, Da‐,Woon,Tilakaratne, Wanninayake M.,Kim, Jin Alan R. Liss, Inc 2015 International journal of cancer Vol.137 No.11
<▼1><P>Molecular crosstalk between cancer cells and fibroblasts has been an emerging hot issue in understanding carcinogenesis. As oral submucous fibrosis (OSF) is an inflammatory fibrotic disease that can potentially transform into squamous cell carcinoma, OSF has been considered to be an appropriate model for studying the role of fibroblasts during early stage carcinogenesis. In this sense, this study aims at investigating whether areca nut (AN)‐exposed fibroblasts cause DNA damage of epithelial cells. For this study, immortalized hNOF (hTERT‐hNOF) was used. We found that the levels of GRO‐α, IL‐6 and IL‐8 increased in AN‐exposed fibroblasts. Cytokine secretion was reduced by antioxidants in AN‐exposed fibroblasts. Increase in DNA double strand breaks (DSB) and 8‐oxoG FITC‐conjugate was observed in immortalized human oral keratinocytes (IHOK) after the treatment of cytokines or a conditioned medium derived from AN‐exposed fibroblasts. Cytokine expression and DNA damage were also detected in OSF tissues. The DNA damage was reduced by neutralizing cytokines or antioxidant treatment. Generation of reactive oxygen species (ROS) and DNA damage response, triggered by cytokines, were abolished when NADPH oxidase (NOX) 1 and 4 were silenced in IHOK, indicating that cytokine‐triggered DNA damage was caused by ROS generation through NOX1 and NOX4. Taken together, this study provided strong evidence that blocking ROS generation might be a rewarding approach for cancer prevention and intervention in OSF.</P></▼1><▼2><P><B>What's new?</B></P><P>Fibroblasts in the tumor microenvironment influence tumor initiation and growth and are of particular interest in oral submucous fibrosis (OSF), a progressive fibrotic disease of malignant potential. This study shows that the release of tumor‐promoting cytokines by fibroblasts exposed to areca nut, the primary cause of OSF, induce DNA damage in oral keratinocytes. The findings suggest that fibroblasts indirectly promote epithelial transformation in OSF by secreting cytokines, whereby DNA damage of epithelial cells is inflicted by reactive oxygen species generated <I>via</I> NADPH oxidases. These insights could inform the development of new therapeutic approaches for OSF.</P></▼2>