Biomedical subjects

Joon Sakong

Publications and source records attributed to Joon Sakong.

11 recordsLinked to original sources

PubMed2006

Evaluation of MR signal index for the assessment of occupational manganese exposure of welders by measurement of local proton T1 relaxation time.

Magnetic resonance (MR) imaging has become a useful tool for the estimation of occupational exposure to manganese (Mn). However, validity of signal indices on T1-weighted imaging, a proxy measurement of T1 relaxation time shortening due to Mn deposition, needs to be evaluated in an occupationally exposed population. We performed MR imaging on 20 male welders and 10 age- and gender-matched, non-office workers in a shipyard. We measured the relative signal intensity ratio of the globus pallidus (GP) to the frontal white matter on T1-weighted MR images (pallidal index, PI). We also assessed the visual scale for the relative signal intensity of the GP, which was graded as 0-2 by a radiologist. We evaluated both signal index and visual scale in relation to the T1 relaxation time measured at the GP. Both PI and T1 relaxation time were significantly increased in the welders compared to the non-welders. T1 relaxation time began to decrease from visual scale 2, while PI began to increase from visual scale 1. Environmental Mn exposure indices correlated well with both T1 relaxation time and PI. However, blood Mn level correlated only with T1 relaxation time, and not with PI. T1 relaxation time correlated with PI only at the higher level of PI. These results indicate the possible inaccuracy of visual scoring and the discrepancy between T1 relaxation time and PI, especially at the lower level of signal intensity. Although both T1 and PI are good biomarkers for the environmental Mn exposure, non-linearity of the relationship between T1 and PI must be considered in the assessment of Mn exposure using MRI.

Adult↗

PubMed2006

Effect of occupational manganese exposure on the central nervous system of welders: 1H magnetic resonance spectroscopy and MRI findings.

This study investigated the relationship between long-term occupational manganese (Mn) exposure on the regional Mn concentration in the brain, neuronal loss, and neurobehavioral effects on welders. 1H MRS of the basal ganglia (BG) was performed on 20 male welders and 10 age- and gender-matched, non-office, control workers in a shipyard to assess the metabolic change, and the N-acetylaspartate (NAA)/creatine (Cr), choline (Cho)/Cr and NAA/Cho ratios, by the level of Mn exposure. We also assessed the signal intensity of T1-weighted image of magnetic resonance imaging (MRI) on globus pallidus (GP) compared to that of the frontal white matter (pallidal index, PI). The welders had significantly higher signal intensity than the controls. PI showed a significant dose-response relationship with cumulative exposure index (CEI) (r=0.54, p=0.002). CEI and PI showed different relationships with NAA/Cr according to smoking status, and the correlation was evident only in non-smokers (r=-0.73 and -0.57, respectively). There were no significant differences between the welders and the controls in NAA/Cr, Cho/Cr, and NAA/Cho ratios obtained from BG. CEI was positively correlated with simple reaction time. PI was positively correlated with mean sway (MSWAY), sway area (SWAYA), and sway intensity (SWAYI), and negatively correlated with maximum frequency (MAXF). After categorizing the subjects into two groups according to NAA/Cr ratio level, the low NAA/Cr ratio group showed significantly lower score on digit span backward and significantly higher score on MSWAY, SWAYA and SWAYI in regression analysis than the high NAA/Cr ratio group. We speculated that the NAA/Cr ratio of MRS in BG seems to reflect the cumulative effect of Mn exposure on the human brain. Due to uneven distribution of smoking among the welders and the controls, in addition to the small number of subjects in our study, our findings are needed further studies with a larger number of subjects.

Adult↗

PubMed2006

The association between neurobehavioral performance and lung function.

This study investigated the relationship between neurobehavioral performance and pulmonary function in young and middle adults. Data were collected from 178 subjects (88 male, 90 female) aged 20-50 years. Neurobehavioral performance was assessed by the Korean version of The Swedish Performance Evaluation System (SPES-K), on five items: simple reaction time, symbol digit, digit span, and finger tapping speed for dominant and non-dominant hands. Pulmonary function, as indicated by the 1-s forced expiratory volume (FEV1), was measured according to American Thoracic Society criteria and the potential association was analyzed by linear regression. For simple reaction time, symbol digit, and digit span, the performance of subjects with FEV1 levels exceeding 3.29 l was 2-4% greater than those with the lowest levels of less than 2.60 l, after controlling for the effects of age, sex, education, smoking, and height. Finger tapping speed, however, did not show any significant association. These findings suggest that pulmonary function may influence neurobehavioral performance, especially cognitive abilities, throughout adulthood.

Adult↗

PubMed2006

High signal intensity on magnetic resonance imaging as a predictor of neurobehavioral performance of workers exposed to manganese.

INTRODUCTION: Using previously obtained cross-sectional data from a nationwide survey on workers exposed to manganese (Mn), we assessed the relation of high signal intensity with neurobehavioral effects, and reevaluated the preexisting cross-sectional data to get additional findings on the relation of high signals with other Mn-exposure indices. SUBJECTS AND METHODS: Subjects were the same as those in the previous study. The exposure status was reassessed based on similar exposure groups. The signal intensity of the globus pallidus (GP) relative to frontal white matter was subjectively evaluated as either with or without increased signals, and the increased signals were further graded into three categories. For quantitative evaluation of signal intensities of the GP we also calculated the pallidal index (PI). Neurobehavioral function was assessed using the World Health Organization Neurobehavioral Core Test Battery. In addition, computerized finger tapping speed was included to assess motor speed. RESULTS: The mean blood Mn for those with grade III was significantly greater than those without increased signals and those with grade I. Airborne Mn and PI also showed similar findings. PI paralleled subjective MRI gradings. The proportion of workers with increased signals increased with all the Mn-exposure variables, airborne and blood Mn, the duration of work, and cumulative exposure. The PI was significantly associated with a correct score of pursuit aiming II tests and finger tapping of the dominant hand after control of age and educational level among neurobehavioral performances. DISCUSSION: The present findings showed that signal index on T1-weighted MRI showed a dose-response relationship with all the Mn-exposure variables. The two neurobehavioral tests reflecting fine motor function were significantly decreased above 107.1 of PI, the cutoff point between those with and without increased signals. Hence, signal intensity on MRI is an effective predictor of the neurobehavioral performance of Mn exposed workers.

Air Pollutants↗

PubMed2006

Neurobehavioral function in children with low blood lead concentrations.

Debate continues as to whether low blood lead level, even below 5 microg/dl, impairs neurodevelopmental function in children. This study assessed the association between neurodevelopmental performance and lead exposure below 5 microg/dl in Korean children. Data were collected from 61 children, aged 7-16 years with a mean blood lead level of 2.9 microg/dl, who participated with their mothers. Neurodevelopmental function was measured with computer-based neurobehavioral tests. The analyzed data included children's performances on five neurobehavioral tests as the dependent variables, and children's blood lead level, sex, age, and mother's performance as the four independent variables. For simple reaction time and digit span, which, respectively reflect attention and short-term memory, there was a small and significant association between the children's neurodevelopmental performance and their blood lead levels (p=0.05, 0.08, respectively). Our study suggests that low blood lead below 5 microg/dl can influence children's neurobehavioral performance.

Adolescent↗

PubMed2006

Evaluation of reliability of traditional and computerized neurobehavioral tests.

Most Korean blue-collar workers are taking government-mandated medical screening periodically. The periodic neurobehavioral test provides a great chance to evaluate the functional change of the central nervous system. To utilize periodic neurobehavioral tests effectively, the reliability of currently used neurobehavioral tests needs to be evaluated. Test-retest of neurobehavioral tests were conducted to evaluate the reliability of neurobehavioral tests that are commonly used for Korean workers. The test-retest of five computerized tests, simple reaction time, additions, symbol digit, digit span, and finger tapping speed, and five traditional tests, Benton visual retention, digit symbol, digit span, pursuit aiming, and pegboard, were administered to 85 college students and 35 hospital workers over a 1 month interval. Computerized additions was found to have the highest test-retest reliability coefficient (r=0.90), followed by finger tapping speed (nondominant hand, r=0.89; dominant hand, r=0.85), symbol digit (r=0.82), and digit span (r=0.74). However, only two traditional tests, digit symbol (r=0.86) and pursuit aiming (r=0.72), showed a reliability coefficient greater than 0.70. These results suggest that the computerized additions, symbol digit, finger tapping speed, and traditional digit symbol are more satisfactory for periodical evaluation of the central nervous system of workers exposed to neurotoxic substances in Korea.

Adult↗

PubMed2006

[Effects of the personal stereo system on hearing in adolescents].

OBJECTIVES: This study was conducted to evaluate the effects of the personal stereo system on the hearing in adolescents. METHODS: A total of 68 adolescents (age: 13-18 years) who visited the ENT Department at a University Hospital in Daegu were personally interviewed. The questionnaires were about general characteristics of the subjects, the time of personal stereo system use (year, hour) and place. Cumulative exposure to the personal stereo system was calculated by the product of the total years and the daily hours of their use. Pure tone audiometry was performed and the hearing threshold was measured at 500, 1000, 2000, 4000 and 8000 Hz. RESULTS: The average time of using a personal stereo system a day was about 3 hours and 75% of the subjects used a personal stereo system for 2-5 years. The elevation of threshold was more prominent in the subjects who used personal stereo systems for 4 years and more compared with those subjects who used them for 3 years and under. The elevation of hearing threshold was also more prominent in the subjects who used personal stereo systems for 4 hours and more a day compared with those subjects who used personal stereo systems for 3 hours and under a day. The elevation of hearing threshold was more prominent in the subjects who used personal stereo systems for 13 hour x years and more compared to the subjects who used them 12 hour x years and under. CONCLUSIONS: These results suggest that the elevation of hearing threshold can happen to adolescents who used personal stereo systems for a long time. In order to prevent hearing loss, we need to teach adolescents appropriate usage of the personal stereo system and hearing tests should be included in the periodic school-based physical examination for the adolescents.

Adolescent↗

PubMed2005

Janus kinase-signal transducer and activator of transcription mediates phosphatidic acid-induced interleukin (IL)-1beta and IL-6 production.

We have found previously that phosphatidic acid (PA) can induce inflammatory mediators such as cytokines, which implies that PA plays a role in inflammatory response. In the present study, we provide evidence of the PA-mediated activation of the Janus tyrosine kinase (JAK)-signal transducer and activator of transcription (STAT) signaling pathway, which results in the production of interleukin (IL)-1beta and IL-6. PA elicited the rapid phosphorylations of JAK2 and STAT1/3, and the subsequent nuclear translocation. Macrophages that had been transiently transfected with a luciferase reporter construct containing eight consecutive gamma-interferon activating sequence (GAS) elements, a known STAT binding site, exhibited enhanced reporter gene activity in response to PA stimulation, which further supports the involvement of JAK-STAT activation in the PA-induced signaling pathway. Of the inflammatory cytokines, IL-1beta, IL-6, and tumor necrosis factor (TNF)-alpha were detected in media from macrophages stimulated with PA. Moreover, the JAK2 inhibitor alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide (AG-490) abolished PA-induced IL-1beta and IL-6 release but not TNF-alpha production, which is consistent with the notion that IL-1beta and IL-6 but not TNF-alpha contain a STAT binding element in their promoter region. The knockdown of JAK2 in macrophages by small interfering RNA significantly attenuated PA-induced IL-1beta and IL-6 production. In addition, JAK2 inhibitor suppressed PA-induced Akt phosphorylation, and the Akt inhibitor 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) blocked GAS activation (GAS contains a promoter that responds to PA), suggesting that PA-mediated JAK2 activation leads to phosphatidylinositol 3-kinase/Akt phosphorylation and STAT activation, and the subsequent translocation of STAT to the nucleus. Together, our data demonstrate that PA-activated macrophages produce IL-1beta and IL-6 and that these processes require the activation of the JAK2-STAT1/3 or JAK2-Akt-STAT signaling pathways.

Active Transport, Cell Nucleus↗

PubMed2005

Pallidal index on MRI as a target organ dose of manganese: structural equation model analysis.

We have used a structural equation model (SEM) to analyze the interrelationships among exposure markers, magnetic resonance imaging (MRI) signal index, and neurobehavioral effects. Based on exposure groups, we assessed blood manganese, MRI measurements of pallidal index (PI), and neurobehavioral core test battery (WHO-NCTB) on 111 male workers occupationally exposed to manganese, including welders, smelter workers, and welding rod manufacturing workers. Latent variables were constructed to represent the neurobehavioral effects in an integrated way. The structural equation model revealed that airborne manganese and blood manganese contribute to PI significantly. Manganese exposure in the ambient air may lead to an increase in the internal dose, not only indirectly, by increasing blood manganese level, but also directly, independent of blood concentration. PI significantly contributed to a decrease in neurobehavioral test scores. We found that airborne manganese contributed to PI, and that PI is the most effective predictor of neurobehavioral performance, after adjusting for age and level of education. In conclusion, PI on MRI reflects target organ dose of occupational manganese exposure.

Accidents, Occupational↗

PubMed2003

Gabapentin effect on neuropathic pain compared among patients with spinal cord injury and different durations of symptoms.

STUDY DESIGN: This study evaluated the effect of gabapentin on neuropathic pain in patients with spinal cord injury. OBJECTIVE: To compare the effect of gabapentin on neuropathic pain refractory to conventional analgesics in patients with spinal cord injury and different durations of symptoms. SUMMARY OF BACKGROUND DATA: Neuropathic pain in patients with spinal cord injury severely compromises their quality of life. Gabapentin is a new antiepileptic drug that may additionally have a role in the treatment of neuropathic pain. So far, there has been little prospective research investigating the effect of gabapentin on neuropathic pain in patients after spinal cord injury or comparing gabapentin-treated patients with varying durations of symptoms after spinal cord injury. METHODS: The study included 31 patients who had experienced neuropathic pain associated with spinal cord injury or cauda equina syndrome. These subjects were divided into two groups. Group 1 (n = 13) was composed of patients whose duration of pain was less than 6 months, and Group 2 (n = 18) comprised patients whose symptoms of neuropathic pain had lasted more than 6 months. Although these patients had been treated with conventional analgesics such as antidepressants, anticonvulsants, membrane stabilizer, and neuroleptics, they reported that their condition did not improve after a medication trial of at least 2 weeks duration. In this study, conventional analgesics were continued at a therapeutic level, and gabapentin was administrated for an 18-day titration period followed by a 5-week maintenance period at a dosage of 1800 mg/day or the maximum tolerable dosage. The efficacy of gabapentin administration was gauged by a pain score and a sleep interference score using a 100-mm visual analogue scale (VAS) every 2 weeks. The scores of the two groups were compared every 2 weeks over the course of the 8-week study. RESULTS: The mean pain score and the mean sleep interference score for Group 1 decreased more than that of Group 2 during the interval between 2 to 8 weeks (P < 0.05). The mean pain score for Group 1 decreased from 7.3 +/- 0.5 initially to 3 +/- 0.6 after 8 weeks of treatment, whereas the corresponding score for Group 2 decreased from 7.6 +/- 0.4 to 5.1 +/- 0.6 ( < 0.05). The mean sleep interference score for Group 1 decreased from 5.7 +/- 0.9 initially to 1.8 +/- 0.8 after 8 weeks of treatment, whereas the corresponding score for Group 2 decreased from 5.9 +/- 0.8 to 4.2 +/- 0.7 (P < 0.05). As compared with the onset of this study, a decrease in pain score of 2 or more was reported at the completion of this study for 11 patients (100%) in Group 1 and 10 (71%) of 14 patients in Group 2. A decrease of 2 or more in sleep interference scores was reported for 8 (89%) of 9 patients with sleep interference in Group 1 and for 8 (62%) of 13 patients with sleep interference in Group 2. Some adverse effects such as somnolence were noted, but they were mild or moderate in intensity. CONCLUSIONS: Gabapentin may be effective in decreasing neuropathic pain refractory to conventional analgesics in some patients with spinal cord injury whose duration of symptoms is less than 6 months, although those with duration of symptoms longer than 6 months showed a significant decrease as well. The drug is unlikely to cause serious adverse effects that limit its use in patients with spinal cord injury.

Acetates↗

PubMed2003

Cross-cultural comparison of neurobehavioral performance in Asian workers.

Widely-used neurobehavioral tests have been developed and standardized on Western populations, but studies on subject factors for Asian populations have been very limited. For the effective application and interpretation of neurobehavioral tests in Asian populations, an evaluation of the effects of subject factors, including cultural background, is necessary. A cross-cultural study was conducted to evaluate the effects of cultural background and the interaction between cultural background and education on neurobehavioral tests in Asian populations. The Korean version of the Swedish Performance Evaluation System (Simple Reaction Time, Symbol Digit, and Finger Tapping Speed) and a pegboard test were administered to 537 workers who were not exposed to chemicals at work from Fareast (Korea and Chinese), Central (Uzbekistan and Tajikistan), and South Asia (Sri Lanka and Indonesia). The Fareast Asian group exhibited better performance in adjusted test scores than other Asian groups, achieving significance for Symbol Digit and Finger Tapping Speed in both genders. The magnitude of the effect of cultural background on Symbol Digit was comparable to the effect of about 10 years of education. Cultural background did not modify the relation between years of education and Symbol Digit in either males or females. This study may provide the first evidence that cultural background has a large impact on neurobehavioral test performance, even within Asian populations, and suggests that cultural background is a critical confounding factor that must be controlled in epidemiologic studies which include Asian populations in the sample.

Adolescent↗