Biomedical subjects

Young Hoon Sung

Publications and source records attributed to Young Hoon Sung.

At least 19 recordsLinked to original sources

PubMed2006

Decreased frontal white-matter integrity in abstinent methamphetamine abusers.

This study explored differences in frontal white-matter (WM) integrity between methamphetamine (MA) abusers and healthy comparison subjects using diffusion tensor imaging (DTI). Fractional anisotropy (FA) values, which indicate WM integrity, were calculated for regions-of-interest in frontal WM on diffusion tensor images of 32 MA abusers and 30 healthy comparison subjects. Frontal executive functions were also assessed by the Wisconsin Card Sorting test (WCST). MA abusers had significantly lower FA values in bilateral frontal WM at the anterior commissure-posterior commissure (AC-PC) plane and the right frontal WM 5 mm above the AC-PC plane relative to healthy comparison subjects. MA abusers had more total, perseveration and non-perseveration errors in the WCST relative to healthy comparison subjects. FA values of the right frontal WM 5 mm above the AC-PC plane negatively correlated with the number of total and non-perseveration errors in the WCST in MA abusers. In the sub-analysis for gender differences, lower FA values in frontal WM and more errors in the WCST were found only in male MA abusers, not in female MA abusers, relative to comparison subjects of the respective gender. We report that frontal WM integrity of MA abusers is compromised. This finding may also be related to impairment in frontal executive function. In addition, the neurotoxic effect of MA on frontal WM may be less prominent in women than in men, possibly due to oestrogen's neuroprotective effect.

Adult↗

PubMed2006

Relationship between N-acetyl-aspartate in gray and white matter of abstinent methamphetamine abusers and their history of drug abuse: a proton magnetic resonance spectroscopy study.

OBJECTIVE: Altered concentrations of the brain metabolites, including N-acetyl-aspartate (NAA) and myo-inositol (MI), may indicate neurotoxicity associated with drug abuse. In this study, the authors explored differences in brain metabolites between abstinent methamphetamine (MA) abusers and healthy comparison subjects and the associations between metabolite concentrations and clinical characteristics. METHOD: Proton magnetic resonance spectroscopy (MRS) was performed on 30 abstinent MA abusers and 20 healthy comparison subjects. Two sets of MA user subgroups were defined depending on abstinence duration (greater or less than 6 months) or the total cumulative MA dose (greater or less than 100 g lifetime). NAA and other metabolites were measured in the frontal gray and white matter and compared between MA abuser groups and healthy comparison subjects. RESULTS: MI concentrations were higher for the MA abusers relative to healthy comparison subjects. NAA concentration was lower in frontal white matter of MA abusers with a 'large' cumulative dose relative to those with a 'small' cumulative dose and to healthy comparison subjects. Additionally, in MA abusers NAA concentrations in frontal white matter correlated inversely with the cumulative MA dose. In contrast, there was no significant difference in frontal gray matter NAA concentration among the three groups. However, frontal gray matter NAA concentrations for MA abusers correlated negatively with the total cumulative MA dose and positively with the duration of abstinence. There were no differences between the different MA user groups for MI. CONCLUSIONS: The current findings suggest that MA-induced metabolic alterations of frontal gray and white matter are dose-dependent, for primarily male subjects. Additionally, these findings potentially suggest that the MA-related abnormalities may, in part, recover with abstinence in gray matter, but not in the white matter regions.

Adult↗

PubMed2006

Jab1 induces the cytoplasmic localization and degradation of p53 in coordination with Hdm2.

The biological mechanisms for maintaining the basal level of p53 in normal cells require nuclear exclusion and cytoplasmic degradation. Here, we showed that Jab1 facilitates p53 nuclear exclusion and its subsequent degradation in coordination with Hdm2. p53 was excluded from the nucleus in the presence of Jab1; this exclusion was prevented by leptomycin B treatment. Nuclear export of p53 was accompanied by a decrease in the levels of p53, as well as of its target proteins, which include p21 and Bax. Domain analyses of Jab1 showed that the N-terminal domain, 1-110, was capable of inducing cytoplasmic translocation of p53. Furthermore, 110-191 was required to facilitate the degradation of p53. Neither of these mutants incorporated into the CSN complex, indicating that Jab1 could affect the levels of p53 independent of intact CSN complex. Conversely, Jab1 was incapable of translocating and degrading two p53 mutants, W23S and 6KR, neither of which could be modified by Hdm2. Moreover, Jab1 did not affect the cellular localization or protein levels of p53 in p53 and Hdm2 double-null mouse embryo fibroblasts. We further observed that the ablation of endogenous Jab1 by small interfering RNA prevented Hdm2-mediated p53 nuclear exclusion. Under stressed conditions, which could sequester Hdm2 in its inactive state, Jab1 did not affect p53. Our studies implicate that Jab1 is required to remove post-translationally modified p53 and provide a novel target for p53-related cancer therapies.

Animals↗

PubMed2006

Role of INK4a locus in normal eye development and cataract genesis.

The murine INK4a locus encodes the critical tumor suppressor proteins, p16(INK4a) and p19(ARF). Mice lacking both p16(INK4a) and p19(ARF) (INK4a-/-) in their FVB/NJ genetic backgrounds developed cataracts and microophthalmia. Histopathologically, INK4a-/- mice showed defects in the developmental regression of the hyaloid vascular system (HVS), retinal dysplasia, and cataracts with numerous vacuolations, closely resembling human persistent hyperplastic primary vitreous (PHPV). Ocular defects, such as retinal fold and abnormal migration of lens fiber cells, were observed as early as embryonic day (E) 15.5, thereby resulting in the abnormal differentiation of the lens. We also found that ectopic expression of p16(INK4a) resulted in the induction of gammaF-crystallin, suggesting an important role of INK4a locus during mouse eye development, and also providing insights into the potential genetic basis of human cataract genesis.

Animals↗

PubMed2006

The relationship between the biogenetic temperament and character and psychopathology in adolescents.

BACKGROUND: This study was conducted to investigate the relationship between patterns of temperament and character and self-reported psychopathology in adolescents from the community. SAMPLING AND METHODS: The Junior Temperament and Character Inventory (JTCI) and Youth Self-Report (YSR) instruments were administered to 623 Korean middle school students (boys/girls = 331/292; age = 13.3 +/- 0.9 years old). Multiple linear regression analyses were used to evaluate the relationship between temperament and character based on Cloninger's biogenetic theory of personality and youth psychopathology of internalizing and externalizing problems. RESULTS: Internalizing problems of the YSR (withdrawn, somatic complaint and anxious/depressed scales) were significantly related to high Harm Avoidance and low Reward Dependence (JTCI temperament) and low Self-Directedness and high Self-Transcendence (JTCI character). Externalizing problems of the YSR (delinquency and aggression) were significantly associated with high Novelty Seeking and high Harm Avoidance (JTCI temperament) and low Self-Directedness, low Cooperativeness and high Self-Transcendence (JTCI character). CONCLUSIONS: Findings of the current study suggest that specific patterns of temperament and character potentially influence adolescents' psychopathology in the community.

Adolescent↗

PubMed2006

Regional cerebral cortical thinning in bipolar disorder.

OBJECTIVE: This study was conducted to explore differences in cortical thickness between subjects with bipolar disorder and healthy comparison subjects using cortical surface-based analysis. METHODS: Brain magnetic resonance images were acquired from 25 subjects with bipolar disorder and 21 healthy comparison subjects. Cortical surface-based analysis was conducted using the Freesurfer application. Group differences in cortical thickness, defined by the distance from gray/white boundary to the pial surface, were assessed using statistical difference maps. RESULTS: Subjects with bipolar disorder exhibited significantly decreased cortical thickness in left cingulate cortex, left middle frontal cortex, left middle occipital cortex, right medial frontal cortex, right angular cortex, right fusiform cortex and bilateral postcentral cortices, relative to healthy comparison subjects (all p < 0.001). Duration of illness in bipolar subjects was inversely correlated with the cortical thickness of the left middle frontal cortex. CONCLUSIONS: Cortical thinning was present in multiple prefrontal cortices in bipolar disorder. There was also cortical thinning in sensory and sensory association cortices, which has not been reported in previous studies using region-of-interest or voxel-based morphometry methods. Cortical thinning observed in the current study may be related to impairment of emotional, cognitive, and sensory processing in bipolar disorder but longitudinal studies will be necessary to test this hypothesis.

Adult↗

PubMed2005

Decreased cerebral blood flow of the right anterior cingulate cortex in long-term and short-term abstinent methamphetamine users.

BACKGROUND: The aim of the current study was to explore changes of relative regional cerebral blood flow (rCBF) in short-term and long-term abstinent methamphetamine (MA) users. METHODS: Relative rCBF in 40 abstinent MA users and 23 healthy comparison subjects was compared by the technetium-99m-hexamethyl-propylene amine oxime ((99m)Tc-HMPAO) single photon emission computed tomography (SPECT). Relative rCBF in areas that were found to differ significantly was also compared in groups of MA users with short-term (<6 months) and long-term (>or=6 months) abstinence. RESULTS: MA users showed decreased relative rCBF in the right anterior cingulate cortex (Brodmann area 32) relative to healthy comparison subjects. Long-term abstinent MA users had significantly greater rCBF than short-term abstinent MA users. CONCLUSIONS: We report that abstinent MA users have decreased rCBF in the anterior cingulate cortex with smaller relative decreases in subjects with prolonged abstinence.

Adult↗

PubMed2005

Decreased blood flow of temporal regions of the brain in subjects with panic disorder.

OBJECT: The purpose of the current study was to investigate alterations of regional cerebral blood flow (rCBF) in subjects with panic disorder. METHODS: Twenty-two subjects with panic disorder who were under psychotropic medications and 25 age and gender-matched healthy comparison subjects were assessed regarding the rCBF of using Tc-99m-hexamethyl propylenamino oxime single photon emission tomography (SPECT). Using statistical parametric mapping, the rCBF was compared between panic disorder and healthy comparison groups. RESULTS: Decreased rCBF flow in right superior temporal lobe was observed in subjects with panic disorder (p<0.05 after correction for multiple comparisons). The rCBF in right superior temporal gyrus negatively correlated with the duration of illness, scores of panic disorder severity scale (PDSS), Hamilton anxiety rating scale (HARS) and Zung self-rating anxiety scale (Z-SAS). CONCLUSION: We report that there is a decreased cerebral blood flow of temporal regions of the brain in panic disorder and that this decrease may, in part, reflect the clinical severity of panic disorder.

Adult↗

PubMed2005

Increased white matter hyperintensities in male methamphetamine abusers.

BACKGROUND: The current study was conducted to compare the prevalence, severity, and location of white matter signal hyperintensities (WMH) on brain magnetic resonance (MR) imaging in methamphetamine (MA) abusers. METHODS: Thirty-three MA abusers and 32 age- and gender-matched healthy comparison subjects were studied. Axial T-2 weighted images and fluid attenuated inversion recovery axial images were obtained using 3.0 T MR scanner. The severity of WMH was assessed separately for deep and periventricular WMH. Ordinal logistic regression models were used to assess the odds ratio for WMH. RESULTS: MA abusers had greater severity of WMH than the healthy comparison subjects (odds ratio: 7.06, 8.46, and 4.56 for all, deep, and periventricular WMH, respectively). Severity of deep WMH correlated with total cumulative dose of MA (p = 0.027). Male MA abusers had greater severity of WMH than female MA abusers (odds ratio = 10.00). While male MA abusers had greater severity of WMH than male comparison subjects (odds ratio = 18.86), there was no significant difference in WMH severity between female MA abusers and female comparison subjects. CONCLUSIONS: The current study reports increased WMH in MA abusers, which may be related to MA-induced cerebral perfusion deficits. In addition, female MA abusers had less severe WMH than male MA abusers, possibly due to estrogen's protective effect against ischemic or neurotoxic effects of MA.

Adult↗

PubMed2005

The pleiotropy of telomerase against cell death.

The end of eukaryotic genomic DNA is capped by a specialized structure called as "telomere", which consists of the repetitive array of nucleotide sequence, TTAGGG, in humans and mice, and a variety of binding proteins. Telomerase is a ribonucleoprotein (RNP) complex responsible for the elongation of telomeres to maintain the genomic integrity, and is composed of telomerase reverse transcriptase (TERT), telomerase RNA component (TERC), and their associated factors regulating the catalytic activity of telomerase. Although it is now apparent that telomerase protects cells from apoptosis via the maintenance of genomic integrity by stabilizing telomeres, our understanding for the physiological role of telomerase is yet far from completion, and emerging evidence suggests that telomerase has additional extratelomeric roles in mediating cell survival and anti-apoptotic functions against various cytotoxic stresses. Here we summarize and discuss how telomerase and telomeres are involved in mediating cellular protection against apoptosis.

Animals↗

PubMed2005

Prefrontal grey-matter changes in short-term and long-term abstinent methamphetamine abusers.

Authors explored grey-matter density in 29 methamphetamine abusers and 20 healthy comparison subjects using voxel-based morphometry. Grey-matter density changes and performances on the Wisconsin Card Sorting test (WCST) were also compared between 11 short-term (<6 months) and 18 long-term (>or=6 months) abstinent methamphetamine abusers. Methamphetamine abusers had lower grey-matter density in the right middle frontal cortex (corrected p<0.05) and more total errors in the WCST (p<0.01) relative to healthy comparison subjects. Grey-matter density decrease in the right middle frontal cortex correlated with total errors in the WCST in methamphetamine abusers (r=-0.45). Long-term abstinent abusers had significantly less right middle frontal grey-matter density decrease (p<0.01) and total errors in the WCST (p<0.01) than short-term abstinent abusers, but more than the healthy comparison subjects. We report that methamphetamine abusers have prefrontal grey-matter deficit, which may, in part, recover with long-term abstinence.

Adult↗

PubMed2005

Generation of reversible Rb-knockdown mice.

This study describes the generation of reversible Rb-knockdown mice using Tet-off system coupled with Rb-deficient mice currently available. Mice expressing pRB conditionally in Rb-/- background were generated by crossings P(hCMV)-tTA/TRE-Rb transgenic mice with conventional Rb+/- mice. Transgenic Rb was tightly controlled with reversibility and biologically effective as exemplified by cyclin E expression in a doxycycline-dependent manner in mouse embryonic fibroblasts. However, its ectopic expression was not sufficient to rescue the phenotypes of Rb-/- embryos at organismal level, suggesting the requirement of more sophisticated regulation of pRB. With all, these results demonstrate that our experimental strategy can be an alternative way to convert classical gene-disrupted mice into reversible conditional ones.

Animals↗

PubMed2005

Frontal glucose hypometabolism in abstinent methamphetamine users.

Changes in relative regional cerebral glucose metabolism (rCMRglc) and their potential gender differences in abstinent methamphetamine (MA) users were explored. Relative rCMRglc, as measured by (18)F-fluorodeoxyglucose positron emission tomography, and frontal executive functions, as assessed by Wisconsin card sorting test (WCST), were compared between 35 abstinent MA users and 21 healthy comparison subjects. In addition, male and female MA users and their gender-matched comparison subjects were compared to investigate potential gender differences. MA users had lower rCMRglc levels in the right superior frontal white matter and more perseveration and nonperseveration errors in the WCST, relative to healthy comparison subjects. Relative rCMRglc in the frontal white matter correlated with number of errors in the WCST in MA users. In the subanalysis for gender differences, lower rCMRglc in the frontal white matter and more errors in the WCST were found only in male MA users, not in female MA users, relative to their gender-matched comparison subjects. The current findings suggest that MA use causes persistent hypometabolism in the frontal white matter and impairment in frontal executive function. Our findings also suggest that the neurotoxic effect of MA on frontal lobes of the brain might be more prominent in men than in women.

Adult↗

PubMed2005

Putaminal gray matter volume decrease in panic disorder: an optimized voxel-based morphometry study.

Our study aimed to identify gray matter volume differences between panic disorder patients and healthy volunteers using optimized voxel-based morphometry. Gray matter volume was compared between 18 panic subjects and 18 healthy volunteers. Panic disorder severity scale (PDSS) and Zung self-rating anxiety scale (Z-SAS) were administered. Gray matter volumes of bilateral putamen were decreased in panic subjects relative to healthy comparison subjects (corrected P < 0.05). Decreased gray matter volume was also observed in the right precuneus, right inferior temporal gyrus, right inferior frontal gyrus, left superior temporal gyrus, and left superior frontal gyrus at a less conservative level of significance. PDSS score negatively correlated with gray matter volume in the left putamen, right putamen, right inferior frontal gyrus, and left superior frontal gyrus in panic subjects. The duration of illness negatively correlated with left putaminal gray matter volume. There was also a negative correlation between gray matter volume in right putamen and Z-SAS score in panic subjects. The current study reports a putaminal gray matter volume decrease in panic subjects, which may be related to the clinical severity of panic disorder.

Adult↗

PubMed2004

Functional genomics approach using mice.

The rapid development and characterization of the mouse genome sequence, coupled with comparative sequence analysis of human, has been paralleled by a reinforced enthusiasm for mouse functional genomics. The way to uncover the in vivo function of genes is to analyze the phenotypes of the mutant animals. From this standpoint, the mouse is a suitable and valuable model organism in the studies of functional genomics. Therefore, there have been enormous efforts to enrich the list of the mutant mice. Such a trend emphasizes the random mutagenesis, including ENU mutagenesis and gene-trap mutagenesis, to obtain a large stock of mutant mice. However, since various mutant alleles are needed to precisely characterize the role of a gene in vivo, mutations should be designed. The simplicity and utility of transgenic technology can satisfy this demand. The combination of RNA interference with transgenic technology will provide more opportunities for researchers. Nevertheless, gene targeting can solely define the in vivo function of a gene without a doubt. Thus, transgenesis and gene targeting will be the major strategies in the field of functional genomics.

Animals↗

PubMed2004

Three-year follow up of women with and without borderline personality disorder: development of Cloninger's character in adolescence.

The purpose of the present study was to examine the developmental patterns of Cloninger's biogenetic character traits in subjects with borderline personality disorder (BPD). Study subjects met Diagnostic and Statistical Manual of Mental Disorders (3rd edn, revised; DSM-III-R) criteria for BPD without comorbid axis I or II disorders, as determined by the Diagnostic Interview for Borderlines-Revised, Structured Clinical Interview for the DSM-III-R, and Diagnostic Interview for Personality Disorders. The BPD subjects and age- and sex-matched healthy comparison subjects were initially interviewed for Cloninger's biogenetic characters and re-interviewed at an interval of 1 year for the following 3 years. There were significant differences in the developmental patterns of self-directedness, cooperativeness, and self-transcendence between BPD and healthy comparison subjects (significant group by time interaction: repeated measures manova, F = 17.3, d.f. = 3,240, P < 0.001; F = 28.5, d.f. = 3,240, P < 0.001; F = 4.7, d.f. = 3,240, P < 0.01, respectively). The BPD subjects had less changes in character-related maturity with increasing age than did healthy comparison subjects. Post-hoc tests with Duncan's statistics revealed that subjects with BPD had significantly lower scores on self-directedness at all assessment time periods (P < 0.01) and lower scores on cooperativeness at the second-year and third-year follow-up assessments as compared to healthy comparison subjects (P < 0.01). The BPD subjects had a distinctively different developmental pattern of Cloninger's character compared to healthy comparison subjects. The character development of BPD patients was more fixed and immature than those of healthy comparison subjects.

Adolescent↗

PubMed2004

Trait and state aspects of harm avoidance and its implication for treatment in major depressive disorder, dysthymic disorder, and depressive personality disorder.

The authors evaluated the trait/state issues of harm avoidance in depressive-spectrum disorders and its predictive potential for antidepressant response. Subjects with Diagnostic and Statistical Manual of Mental Disorders (4th edn; DSM-IV) major depressive disorder (n = 39), dysthymic disorder (n = 37), depressive personality disorder (n = 39), and healthy control subjects (n = 40) were evaluated with the Temperament and Character Inventory and the 17-item Hamilton Depression Rating Scale (HDRS-17) at baseline and after a 12 week antidepressant treatment period. Higher harm avoidance scores predicted lesser improvement in subjects with dysthymic disorder and major depressive disorder, as determined by lesser decrease in HDRS-17 scores. Mean harm avoidance scores in depressed subjects were consistently greater than those in healthy controls, controlling for age, gender and diagnosis. Mean harm avoidance scores decreased significantly in all depressive-spectrum disorders after treatment, but still remained higher than harm avoidance scores in control subjects. The present study reports that harm avoidance is a reliable predictor of antidepressant treatment in subjects with major depressive disorder and dysthymic disorder and that harm avoidance is both trait- and state-dependent in depressive-spectrum disorders.

Adult↗

PubMed2004

Attention deficit hyperactivity symptoms and internet addiction.

The objective of this study was to evaluate the relationship between attention deficit-hyperactivity/impulsivity symptoms and Internet addiction. In total, 535 elementary school students (264 boys, 271 girls; mean age, 11.0 +/- 1.0 years) were recruited. The presence or severity of Internet addiction was assessed by the Young's Internet Addiction test. Parents and teachers of the children completed the DuPaul's attention deficit hyperactivity disorder (ADHD) rating scale (ARS; Korean version, K-ARS) and Child Behavior Checklists. Children with the highest and lowest quartiles in K-ARS scores were defined to be in ADHD and non-ADHD groups, respectively. Five children (0.9%) met criteria for a definite Internet addiction and 75 children (14.0%) met criteria for a probable Internet addiction. K-ARS scores had significant positive correlations with Young's Internet Addiction test scores. The Internet addiction group had higher total scores of K-ARS and ADHD-related subcategories in the Child Behavior Checklists than the non-addiction group. The ADHD group had higher Internet addiction scores compared with the non-ADHD group. Therefore, significant associations have been found between the level of ADHD symptoms and the severity of Internet addiction in children. In addition, current findings suggest that the presence of ADHD symptoms, both in inattention and hyperactivity-impulsivity domains, may be one of the important risk factors for Internet addiction.

Attention Deficit Disorder with Hyperactivity↗