• Sleep Medicine and Psychophysiology
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• v.10 no.2
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• pp.93-99
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• 2003

Objectives：Sleep loss and excessive daytime sleepiness may have serious consequences, including traffic and industrial accidents, decreased productivity, learning disabilities and interpersonal problems. Yet despite these adverse effects, there are few epidemiological studies on sleep loss and daytime sleepiness in the general population of Korea. This study investigates the number of people who suffer from sleep insufficiency, how much recovery sleep occurs on weekends, and the relationship between the amount of recovery sleep and daytime sleepiness. Methods：A total 164 volunteers, aged 20 and over, were recruited by advertisement. The subjects were workers and college students living in Seoul, Korea. Subjects were excluded if they were aged over 60；if they had medical, neurological, psychiatric or sleep disorders that could cause insomnia or daytime sleepiness；if they were not following a regular sleep schedule；if they traveled abroad during the study；or if they did not leave home to work or were shift workers. They were interviewed and given a sleep log to complete on each of 14 consecutive mornings. They also completed the Epworth Sleepiness Scale (ESS) at noontime on the last day of the second week. All statistical data were analyzed by t-test, $X^2$-test or ANOVA, using SPSS/PC+. Results：The results showed that the subjects woke up at 6：50 (${\pm}1$：16) on weekdays, 7：09 (${\pm}1$：29) on Saturdays, and 8：12 (${\pm}1$：39) on Sundays and holidays. They took more frequent and longer naps on Sundays than on weekdays and Saturdays. The mean sleep duration was 6h 35 min. on week nights, with a mean increase of about 1h on weekends. Only 9.1% of the subjects spent more than 8h in bed on week nights, with 67% spending less than 7h, and 49.4% reported recovery sleep of more than 1h on Sundays. The subjects who reported recovery sleep of more than 2h on Sundays, showed significantly more excessive daytime sleepiness than those who reported less than 30 min (F=2.62, p<.05). Conclusions：These findings suggest that sleep insufficiency and excessive daytime sleepiness are relatively common in Korea, and that the people who get insufficient sleep on weekdays try to compensate for sleep loss with oversleeping and daytime napping on Sundays and holidays. It appeared that daily sleep insufficiency had a cumulative effect and increased daytime sleepiness.

• Journal of Preventive Medicine and Public Health
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• v.29 no.2 s.53
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• pp.173-186
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• 1996

This is a cross-sectional study to evaluate the relationships between physical fitness, leisure time physical activity, and serum lipid levels in middle-aged male workers. Physical fitness was measured by a step test score, and leisure time physical activity was self-reported on a questionnaire. Serum total cholesterol was negatively related to physical fitness(r=-0.27), and positively to obesity index(r=0.27). But leisure time physical activity was related to total cholesterol negatively(r=-0.20) only in subjects whose total cholesterol levels were above 170mg/dl. High density lipoprotein(HDL) cholesterol was positively related to physical fitness(r=0.15), negatively to obestiy index(r=-0.22), and positively to weekly alcohol consumption(r=0.14). Total cholesterol/HDL cholesterol ratio was related to physical fitness(r=-0.23), obesity index(r=0.32), total cigarette index (r=0.13), weekly alcohol consumption(r=-0.13), and vegetable preference(r=0.13). Physical fitness was also related to leisure time physical activity(r=0.19) and obesity index(r=-0.18). In multiple linear regression models, physical fitness(beta=-0.23) and obesity index(beta=0.18) were significantly associated with total cholesterol, obesity index(beta=-0.25) with HDLcholesterol, and obesity index(beta=0.30), physical fitness(beta=-0.16) and vegetable preference (beta=0.14) with total cholesterol/HDL cholesterol ratio. In conclusion, as physical fitness has a stronger relationship with serum lipid levels than leisure time physical activity, and the association between physical fitness and leisure time physical activity is modest, physical fitness should be added as an important variable in addition to activity in future epidemiologic studies.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.16 no.1
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• pp.1-13
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• 2011

The Yellow Sea Cold Water (YSCW) is formed by cold and dry wind in the previous winter, and is known to spread southward along the central trough of the Yellow Sea in summer. Water characteristics of the YSCW and its movement in the northern East China Sea (ECS) are investigated by analyzing CTD (conductivity-Temperature-Depth) data collected from summertime hydrographic surveys between 2003 and 2009. By water mass analysis, we newly define the North Western Cold Water (NWCW) as a cold water mass observed in the study area. It is characterized by temperature below $13.2^{\circ}C$, salinity of 32.6~33.7 psu, and density (${\sigma}_t$) of 24.7~25.5. The NWCW appears to flow southward at about a speed less than 2 cm/s according to the geostrophic calculation. The newly defined NWCW shows an interannual variation in the range of temperature and occupied area, which is in close relation with the sea surface temperature (SST) over the Yellow Sea and the East China Sea in the previous winter season. The winter SST is determined by winter air temperature, which shows a high correlation with the winter-mean Arctic Oscillation (AO) index. The negative winter-mean AO causes the low winter SST over the Yellow Sea and the East China Sea, resulting in the summertime expansion and lower temperature of the NWCW in the study area. This study shows a dynamic relation among the winter-mean AO index, SST, and NWCW, which helps to predict the movement of NWCW in the northern ECS in summer.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.6 no.2
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• pp.120-128
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• 2003

Purpose: Recently, while the authors were experiencing that the epidemic period of rotaviral infection happened more in the early spring, we tried to find out how the outbreaks of rotaviral infection are changing in detail depending on the weather condition since it has something to do with the climate factors and PM10. Methods: Fourteen hundreds seventy nine patients who were proved to be positive to rotavirus were chosen among children less than 5 years old from January 1995 to June 2003. Among various climate factors, monthly average temperature, humidity, rainfall and PM10 were selected. Results: Rotaviral infection was most active in 2002 as 309 (20.9%) patients. It has been the spring that is the most active period of rotaviral infection since 2000. The temperature (RR=0.9423, CI=0.933424~0.951163), rainfall (RR=1.0024, CI=1.001523~1.003228) and PM10 (RR=1.0123, CI=1.009385~1.015248) were significantly associated with the monthly distribution of rotaviral infection. Conclusion: Through this study we determined that the epidemic period of rotaviral infection is changed to spring, which is different from the usual seasonal periods such as late fall or winter as reported in previous articles. As increased PM10 which could give serious influence to the human body, and changing pattern of climate factors such as monthly average temperature and rainfall have something to do with the rotaviral infection, we suppose that further study concerning this result is required in the aspects of epidemiology, biology and atmospheric science.

• Journal of Chest Surgery
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• v.32 no.4
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• pp.341-346
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• 1999

Background: Thirty children ranging from 3 to 15 years of age underwent cardiac valve replacement at Dongsan Medical Center from 1982 to 1997. Material and Method: There were 16 boys and 14 girls. The mean age was 12.1. The underlying pathological cause for valve replacement was congenital heart disease in 17 children and acquired heart disease in 13. The valve replaced was mitral in 15 children, aortic in 11, tricuspid in 3, and combined aortic and mitral in 1. Twenty-one mechanical and 10 tissue valves were placed: primary mechanical valve have been utilized since 1985. Eight of ten patients with tissue valves have had successful second valve replacements 4 to 11 years after the initial operation. Result: The operative mortality was 6.7%, but mortality was higher among patients less than 5 years of age and patients who had previous cardiac operations. Of the 28 operative survivors, 4 patients were lost to follow-up: the remaining patients were observed for a total of 2091 patient/months(mean 74.7 months, maximum 187 months). There was one late death from dilated cardiomyopathy after mitral valve replacement in 7 year-old patient with atrioventricular septal defect. After the operation, all patients with mechanical valves were placed on a strict anticoagulant regimen with Coumadin. The actuarial survival rate was 96% at the end of the follow-up. No instance of thromboembolism or major bleeding were observed in the survivors. Conclusion: These results indicate that valve replacement can be performed with low mortality in children, and with satisfactory long-term survival.

• Investigative Magnetic Resonance Imaging
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• v.9 no.1
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• pp.30-35
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• 2005

Purpose : The purpose of this study is to observe the blood oxygen level dependent (BOLD) contrast changes due to the reaction of human brain at a gustatory sense in response to a salty-taste stimulation. Materials and Methods : Twelve healthy, non-smoking, right-handed male subjects (mean age: 25.6, range: 23-28 years) participated in this salty-taste stimulus functional magnetic resonance (fMRI) study. MRI scans were performed with 1.57 GE Signa, using a multi-slice GE-EPI sequence according to a blood-oxy-gen-level dependent (BOLD) experiment paradigm. Scan parameters included matrix size $128\times128$, FOV 250 mm, TR 5000 msec, TE 60 msec, TH/GAP 5/2 mm. Sequential data acquisitions were carried out for 42 measurements with a repetition time of 5 sec for each taste-stimulus experiments. Analysis of fMRI data was carried out using SPM99 implemented in Matlab. NaCl solution $(3\%)$ was used as a salty stimulus. The task paradigm consisted of alternating rest-stimulus cycles (30-second rest, 15-second stimulus) for 210 seconds. During the stimulus period, NaCl-solution was presented to the subject's mouth through plastic tubes as a bolus of delivered every 5 sec using -processor controlled auto-syringe pump. Results : Insula, frontal opercular taste cortex, amygdala and orbitofrontal cortex (OFC) were activated by a salty-taste stimulation $(NaCl,\;3\%)$ in the fMRI experiments. And dosolateral prefrontal cortex (DLPFC) was also significantly responded to salty-taste stimuli. Activation areas of the right side hemisphere were more superior to the left side hemisphere. Conclusion : The results of this study well correspond to the fact that both insula, amygdala, OFC, DLPFC areas are established as taste cortical areas by neuronal recordings in primates. Authors found that laboratory-developed auto-syringe pump is suitable for gustatory fMRI study. Further research in this field will accelerate to inquire into the mechanism of higher order gustatory process.

• Clinical and Experimental Pediatrics
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• v.50 no.10
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• pp.965-969
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• 2007

Purpose : Measurement of antistreptolysin O (ASO) is often necessary to confirm a clinical diagnosis of recent streptococcal infection, especially in patients suspected of rheumatic fever and acute glomerulonephritis. Standard normal ranges for ASO should be established locally for each age group. We analyzed ASO to determine the upper limit of normal (ULN) ASO in children in the Gyeonggi-Incheon area. Methods : ASO in normal individual concentrations were measured quantitatively by nephelometry on sera from 753 children (Male : 381, Female : 372). ULN were determined by separating the upper 20% from the lower 80% of the group (80 percentile). Results : The mean ASO concentration calculated in a total cases was $149.9{\pm}7.2IU/mL$. The ASO concentration in neonates was $83.4{\pm}10.7IU/mL$, and lowest in the 1 year of age group, $26.7{\pm}6.6IU/mL$, and increased to $318.0{\pm}33.2IU/mL$ gradually in the 9 years of age group. Thereafter, ASO concentration decreased. The ULN for neonates was 122 IU/mL, for 0-3 years, 40 IU/mL; for 4-6 years, 113 IU/ mL; for 7-9 years, 489 IU/mL; for 10-19 years, 433 IU/mL; for 20-29 years, 122 IU/mL. Conclusion : The age-specific ULN for children in the Gyeonggi-Incheon area were determined. The distribution of ASO concentration according to age groups was different from previous reports. These results should be of clinical value to physicians to interprete the ASO results of their patients.

• Journal of the Korean Society of Groundwater Environment
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• v.5 no.4
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• pp.177-191
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• 1998

For various kinds of waters including surface water, shallow groundwater (＜70 m deep) and deep groundwater (500∼810 m deep) from the Pungki area, an integrated study based on hydrochemical, multivariate statistical, thermodynamic, environmental isotopic (tritium, oxygen-hydrogen, carbon and sulfur), and mass-balance approaches was attempted to elucidate the hydrogeochemical and hydrologic characteristics of the groundwater system in the gneiss area. Shallow groundwaters are typified as the 'Ca-HCO$_3$'type with higher concentrations of Ca, Mg, SO$_4$and NO$_3$, whereas deep groundwaters are the 'Na-HCO$_3$'type with elevated concentrations of Na, Ba, Li, H$_2$S, F and Cl and are supersaturated with respect to calcite. The waters in the area are largely classified into two groups: 1) surface waters and most of shallow groundwaters, and 2) deep groundwaters and one sample of shallow groundwater. Seasonal compositional variations are recognized for the former. Multivariate statistical analysis indicates that three factors may explain about 86% of the compositional variations observed in deep groundwaters. These are: 1) plagioclase dissolution and calcite precipitation, 2) sulfate reduction, and 3) acid hydrolysis of hydroxyl-bearing minerals(mainly mica). By combining with results of thermodynamic calculation, four appropriate models of water/ rock interaction, each showing the dissolution of plagioclase, kaolinite and micas and the precipitation of calcite, illite, laumontite, chlorite and smectite, are proposed by mass balance modelling in order to explain the water quality of deep groundwaters. Oxygen-hydrogen isotope data indicate that deep groundwaters were originated from a local meteoric water recharged from distant, topograpically high mountainous region and underwent larger degrees of water/rock interaction during the regional deep circulation, whereas the shallow groundwaters were recharged from nearby, topograpically low region. Tritium data show that the recharge time was the pre-thermonuclear age for deep groundwaters (＜0.2 TU) but the post-thermonuclear age for shallow groundwaters (5.66∼7.79 TU). The $\delta$$\^$34/S values of dissolved sulfate indicate that high amounts of dissolved H$_2$S (up to 3.9 mg/1), a characteristic of deep groundwaters in this area, might be derived from the reduction of sulfate. The $\delta$$\^$13/C values of dissolved carbonates are controlled by not only the dissolution of carbonate minerals by dissolved soil CO$_2$(for shallow groundwaters) but also the reprecipitation of calcite (for deep groundwaters). An integrated model of the origin, flow and chemical evolution for the groundwaters in this area is proposed in this study.

• Pediatric Gastroenterology, Hepatology & Nutrition
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• v.9 no.2
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• pp.139-146
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• 2006

Purpose: Human astrovirus (HAstV) is known to be an important etiologic agent of acute gastroenteritis in infants worldwide. However, the prevalence of HAstV infection varies according to geographic region and patient age. The purpose of our study was to investigate the incidence of HAstV infection among hospitalized children at a tertiary hospital in Seoul. Methods: Fecal samples were collected from hospitalized children up to five years of age with acute gastroenteritis. A total of 812 fecal samples were collected from hospitalized children with acute gastroenteritis between February 2004 and January 2005. Fecal specimens were screened for rotavirus, enteric adenovirus and norovirus by enzyme immunoassay (EIA) or reverse transcriptase polymerase chain reaction (RT-PCR). HAstV positive samples were characterized by RT-PCR. Results: Rotavirus was detected in 16.9% (138/812), norovirus in 11.6% (94/812), and adenovirus in 4.0% (33/812) of the study population. HAstV was detected in 4.0% (33/812) samples by RT-PCR. The age distribution of HAstV positive patients was as follows: <12 month old, 82.0% (27/33); 1~2 years old, 6.0% (2/33); 2~5 years old, 12.0% (4/33). The seasonal distribution of HAstV positive samples was as follows; April (3), May (5), June (4), August (12), September (4), October (2), November (2), and December (1). The peak rate of HAstV infection was observed during the summer season, 2004. A mixed infection of viral agents was confirmed in 2.7% (22 /812) of the study population, most commonly with rotavirus and norovirus, and with rotavirus and HAstV. Genotype 1 was the predominant type (91%, 20/22) and genotype 8 was detected in two cases. Conclusion: The prevalence of HAstV infection was 4.0% in hospitalized children with acute gastroenteritis, and was especially high in infants. HAstV can be considered as an important etiologic agent of gastroenteritis in children.

• Journal of Life Science
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• v.27 no.10
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• pp.1199-1206
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• 2017

The lymphotoxin ${\beta}$ receptor ($LT{\beta}R$), a member of the tumor necrosis factor receptor family, plays an important role in lymphoid tissue's architecture and organogenesis. We found that $LT{\beta}R$ stimulation induced changes in stress fibers (SFs) in fibroblastic reticular cells (FRCs). MLCK and ROCK play critical roles in the regulation of SF formation in cells. The present study was performed to investigate the antifibrotic effects on SF regulation of $LT{\beta}R$ signaling, with a focus on MLCK inhibition. The effect of $LT{\beta}R$ on the SF change was analyzed using immunoblot and fluorescence assays and agonistic $anti-LT{\beta}R$ antibody-treated FRCs. In addition, we checked the level of Rho-guanosine diphosphate (GDP)/guanosine triphosphate (GTP) exchange activity with FRC lysate. Phospho-ezrin proteins acting as membrane-cytoskeleton linkers completely de-phosphorylated in agonistic $anti-LT{\beta}R$ antibody-treated FRCs. The actin bundles rearranged into SFs, where phospho-myosin light chain (p-MLC) co-localized in FRCs. ML7-treated FRCs completely blocked SFs and showed retraction and shrinkage processes comparable to those observed in agonistic $anti-LT{\beta}R$ antibody-treated cells. Inhibition of ROCK activity induced changes in the actin cytoskeleton organization; however, some SFs remained in the cells, while they were completely disrupted by MLCK inhibition with ML7. We showed that the phosphorylation of MLC was completely abolished with $LT{\beta}R$ stimulation in FRCs. When $LT{\beta}R$ was stimulated with the agonistic $anti-LT{\beta}R$ antibody, the Rho-GDP/GTP exchange activity was reduced, however, the activity was not completely abolished. Collectively, the results illustrated that MLCK was potently responsible for the SF regulation triggered via $LT{\beta}R$ signaling in FRCs.