Biomedical subjects

Seung Ha Oh

Publications and source records attributed to Seung Ha Oh.

13 recordsLinked to original sources

PubMed2006

Immunohistochemical study of the distribution of sodium-dependent vitamin C transporters in adult rat brain.

Sodium-dependent vitamin C transporters (SVCTs) is known to transport the reduced form of ascorbic acid into the cell, whereas the oxidized form of vitamin C (VC) is moved through a facilitative sugar transporter, such as glucose transporter (GLUT). With regard to the distribution of SVCT1 and -2 within the various organs, they were reported to be expressed in different types of cells. Especially in the central nervous system, only SVCT2 mRNA was expressed mainly in neurons and some types of neuroglial cells. However, data on the expression of SVCT proteins in the brain are scant. Therefore, we tried to develop comprehensive data on the distribution of SVCT proteins in adult rat brain by using immunohistochemical techniques for the first time. In our study, SVCT2 immunoreactivities (IRs) were intensely localized in the neurons of cerebral cortex, hippocampus, and Purkinje cells of cerebellum, and much weaker SVCT2 IRs were found in the other brain regions. Judging from double-immunohistochemical data, most of the cells expressing SVCT2 IRs were likely to be neurons or microglia, even though the cells in choroids plexus or ependymal cells around the ventricles also exhibited SVCT2 IRs. Complete mapping of the distribution of SVCT2 IRs was available by using a semiquantitative method. The subcellular localization of SVCT proteins is necessary for understanding the exact role of the protein, so the current overall mapping of SVCT IRs in the rat brain could be the basis for further studies on related subjects.

Animals↗

PubMed2005

Three-dimensional analysis of electrode behavior in a human cochlear model.

Three-dimensional (3D) finite element analysis is used in this study to model the mechanical effects of the electrode in a cochlear implant. We employ six electrodes with different stiffness produced by different arrangements of metal wires. Different wire arrangements are generated by changing the fitness function of a genetic program. The human cochlea is modeled by the spiral-approximation method. Reconstructed three-dimensional CT images are used to model the real insertion condition. The contact pressure at the tip and the insertion force are found to be highest when the wires are stacked horizontally. Axial rotation of the electrode has minimal effect on the stimulating current spread. The electrode does not contact the basilar membrane. The results indicate that considering the electrode stiffness is important to minimizing mechanical trauma in cochlear implantation.

Acoustic Stimulation↗

PubMed2005

Voxel-based statistical analysis of cerebral glucose metabolism in the rat cortical deafness model by 3D reconstruction of brain from autoradiographic images.

PURPOSE: Animal models of cortical deafness are essential for investigation of the cerebral glucose metabolism in congenital or prelingual deafness. Autoradiographic imaging is mainly used to assess the cerebral glucose metabolism in rodents. In this study, procedures for the 3D voxel-based statistical analysis of autoradiographic data were established to enable investigations of the within-modal and cross-modal plasticity through entire areas of the brain of sensory-deprived animals without lumping together heterogeneous subregions within each brain structure into a large region of interest. METHODS: Thirteen 2-[1-(14)C]-deoxy-D: -glucose autoradiographic images were acquired from six deaf and seven age-matched normal rats (age 6-10 weeks). The deafness was induced by surgical ablation. For the 3D voxel-based statistical analysis, brain slices were extracted semiautomatically from the autoradiographic images, which contained the coronal sections of the brain, and were stacked into 3D volume data. Using principal axes matching and mutual information maximization algorithms, the adjacent coronal sections were co-registered using a rigid body transformation, and all sections were realigned to the first section. A study-specific template was composed and the realigned images were spatially normalized onto the template. Following count normalization, voxel-wise t tests were performed to reveal the areas with significant differences in cerebral glucose metabolism between the deaf and the control rats. RESULTS: Continuous and clear edges were detected in each image after registration between the coronal sections, and the internal and external landmarks extracted from the spatially normalized images were well matched, demonstrating the reliability of the spatial processing procedures. Voxel-wise t tests showed that the glucose metabolism in the bilateral auditory cortices of the deaf rats was significantly (P<0.001) lower than that in the controls. There was no significantly reduced metabolism in any other area, and no area showed a significant increase in metabolism in the deaf rats with the same threshold, demonstrating the high localization accuracy and specificity of the method developed in this study. CONCLUSION: This study established new procedures for the 3D reconstruction and voxel-based analysis of autoradiographic data which will be useful for examining the cerebral glucose metabolism in a rat cortical deafness model.

Algorithms↗

PubMed2005

Head position dependency of induced nystagmus to ice-water irrigation in peripheral vestibulopathy.

OBJECTIVE: Evaluation of head-position dependency during the ice-water test is essential when the test is indicated. Because ice-water irrigation (IWI) in the prone position is frequently skipped in many laboratories, we investigated the importance of evaluating position dependency in an ice-water test. DESIGN AND SETTING: Twenty-five unilateral peripheral vestibulopathy patients showing no nystagmus during warm irrigation were included. IWI was performed in supine and prone positions, and maximum slow-phase velocity and direction of nystagmus were assessed by using video nystagmography. RESULTS: Eleven cases showed head-position dependency and were interpreted as hypofunctional. Fourteen cases showed no dependency, suggesting the absence of end organ function. In the latter group, 6 patients showing definite nystagmus in supine position could have been misinterpreted as hypofunctional, had it not been for prone-position results. CONCLUSIONS: Evaluation of head position dependency by using IWI is important in the determination of lateral semicircular canal function.

Adult↗

PubMed2004

Subcellular localization of WD40 repeat 1 protein in PC12 rat pheochromocytoma cells.

The dynamics of actin filament protein is crucial for various physiological processes of the cells. Among the proteins correlating with actin dynamics, a novel 67-kDa WD40 repeat protein 1 (WDR1) was the vertebrate homologue of actin-interacting protein 1 (Aip1). Even though previous studies have provided the clues on the function of WDR1 in specific organs under pathological conditions, the exact subcellular localization of WDR1 is not known. Therefore, in the present study, we undertook to determine the distribution of WDR1 within PC12 pheochromocytoma cells (PC12 cells) using light and electron microscopic techniques. Double immunocytochemistry clearly showed that WDR1 immunoreactivities (IRs) were co-localized with anti-actin antibody, suggesting the involvement of WDR1 in actin dynamics. WDR1 immunoreactivities (IRs) in PC12 cells showed different distribution patterns as nerve growth factor (NGF) concentrations varied. During active proliferation, the distribution of WDR1 IRs seemed to be similar to those found in cortical actin patches, whereas WDR1 IR was observed in cytoplasmic actin cables after PC12 cells were induced to differentiate by treating with NGF. Though further studies are necessary to determine the function of WDR1, the current data represents a first step towards the in vitro study of WDR1 protein.

Actins↗

PubMed2004

The distribution of c-myb immunoreactivities in the adult mouse retina.

The myb gene family is composed of three different myb-related genes, A-, B- and c-myb. Among these, the presence of c-myb mRNA in developing and adult retina was previously reported. However, further study on the expression of c-myb in the retina is warranted because the previous study was only performed on developing retinal tissues by in situ hybridization technique. Therefore, in this study, we tried to perform immunohistochemical study, with a focus on the c-myb protein expression in adult retina. Although the cell types were unconfirmed, c-myb protein was likely to have been found in the ganglion, amacrine, horizontal and photoreceptor cells, judging from their locations and morphologies. The experimental data suggested that c-myb immunoreactivities were expressed by the cells in the neural retina, even in the adult stage, especially within some types of cells in specified retinal layers. This suggests that c-myb might play a role in the physiology of the retinal cells, not only in differentiation during retinal development.

Animals↗

PubMed2004

Neural changes associated with speech learning in deaf children following cochlear implantation.

Brain plasticity was investigated, which underlies the gaining of auditory sensory and/or auditory language in deaf children with an early onset deafness after cochlear implantation (CI) surgery. This study examined both the glucose metabolism of the brain and the auditory speech learning using 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) and the Central Institute of Deaf (CID) test, respectively, both before and after the CI surgery. In a within analysis comparing the pre-CI and the post-CI PET results, CI itself resulted in an increase in the glucose metabolism in the medial visual cortex, the bilateral thalamus, and the posterior cingulate. Compared with the normal hearing controls, the brain activity of the deaf children was greater in the medial visual cortex and bilateral occipito-parietal junctions after the CI. The better speech perception ability was associated with increases in activity in the higher visual areas such as middle occipito-temporal junction (hMT/V5) and posterior inferior temporal region (BA 21/37) in the left hemisphere and associated with decreases in activity in the right inferior parieto-dorsal prefrontal region. These findings suggest that the speech learning resulted in a greater demand of the visual and visuospatial processings subserved by the early visual cortex and parietal cortices. However, only those deaf children who successfully learned the auditory language after CI used more visual motion perception for mouth movement in the left hMT/V5 region and less somatosensory function in the right parieto-frontal region.

Adolescent↗

PubMed2004

Age-associated changes of cerebral glucose metabolic activity in both male and female deaf children: parametric analysis using objective volume of interest and voxel-based mapping.

Quantitative analysis of brain activity in the brains of children requires the establishment of age-associated norms. We investigated regional differences in age-associated changes in fluorodeoxyglucose (FDG) uptake in the developmental brains. From 87 (44 male and 43 female) deaf children from the age of 1 to 15, brain FDG positron emission tomography (PET) images were examined after spatial normalization, smoothing, and global normalization to identify brain regions showing a correlation between FDG uptake and age. Using population-based probabilistic volume of interests (VOIs), an objective VOI analysis was performed where normalized relative FDG uptake was measured and their correlations with age were examined in both genders. For the voxel-based analyses, the correlations with age were examined in a general linear model using statistical parametric mapping (SPM99). Both methods revealed that FDG uptake linearly increases with age both in the bilateral inferior prefrontal/orbitofrontal gyri and the right dorsomedial frontal gyrus and decreases in the inferior temporal gyrus and internal capsule white matter. Male children showed age-associated increases of FDG uptake in the right dorsomedial frontal gyrus, and female children in the left dorsolateral prefrontal cortex and thalamus. These changes in FDG uptake in various brain regions may suggest changes in synaptic density or regional activity resulting from normal maturation or deaf-induced adaptation. Caution should be exercised in interpreting the differences in the brain of child patients when compared with adult control's or with a different gender. Further research will be needed to examine if gender difference is manifested in the development rate of behavioral/cognitive functions in association with the age-associated changes of the right medial frontal (male) or the left dorsolateral prefrontal cortices.

Adolescent↗

PubMed2003

Bone morphogenetic protein 4 (BMP4): a regulator of capsule chondrogenesis in the developing mouse inner ear.

Formation of the cartilaginous otic capsule is directed by otic epithelial-periotic mesenchymal interactions. In response to induction by otic epithelium, condensations of mesenchyme appear in the periotic region and form a chondrified otic capsule that serves as the template for the subsequent formation of the endochondral bony labyrinth. Previous studies indicate that members of the transforming growth factor beta superfamily, including transforming growth factor beta(1), participate in guiding these tissue interactions. In this study, we report the localization of bone morphogenetic protein 4 (BMP4) to the mesenchymal and epithelial-derived tissues of the mouse inner ear between 10.5 and 14 days of embryonic development. We demonstrate modulation of chondrogenesis in cultured mouse periotic mesenchyme by exogenous BMP4 protein and investigate the function of endogenous BMP4 in otic capsule chondrogenesis. We show that in the presence of the BMP antagonist, Noggin, otic capsule chondrogenesis is suppressed in culture in a dose-dependent manner. Consistent with this finding, addition of BMP4-specific antisense oligonucleotide to cultures of mouse periotic mesenchyme containing otic epithelium decreases levels of endogenous BMP4 protein and suppresses the chondrogenic response of the cultured periotic mesenchyme, providing evidence of the necessity for BMP4 in mediating otic capsule chondrogenesis. Supplementation of either Noggin- or BMP4 antisense oligonucleotide-treated cultures with BMP4 protein can restore the extent of chondrogenesis to normal levels. Our findings support BMP4 as an essential mediator of chondrogenesis in the developing otic capsule in situ.

Animals↗

PubMed2003

Prognostic factors of recidivism in pediatric cholesteatoma surgery.

OBJECTIVE: To analyze the results on a series of pediatric cholesteatomas, using various preoperative factors, including some of the proposed classification systems, to identify those factors that influence the postoperative result. METHOD: Retrospective review of 118 children with acquired cholesteatoma who underwent surgery from January 1978 to October 1999. The median observation period was 5 years, range 1-20 years. The rate of recidivism calculated using the Kaplan-Meier method and relative risk by the Cox regression model. RESULTS: Cholesteatoma in patients less than 8 years old with mastoid involvement had significantly higher risk of recidivism than the other groups examined. CONCLUSIONS: In this study, cholesteatoma recurred up to 5 years after operation, and long-term close follow-up is important especially in cases involving higher risk such as younger child with mastoid extension of cholesteatoma.

Adolescent↗

PubMed2003

Management of intratemporal facial nerve schwannoma.

OBJECTIVE: The aim of this study was to report a series of 18 facial nerve schwannomas, including 2 infantile cases. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Eighteen patients with facial nerve schwannoma, operated on between 1980 and 2000. INTERVENTION: Surgical treatments were performed in all cases. MAIN OUTCOME MEASURES: The presenting symptoms and facial nerve function were graded using the House-Brackmann scale and eye closure. RESULTS Facial nerve paralysis was the most common symptom, presenting in 94% of cases, followed by hearing loss and mass lesion. In one case, the tumor was shaved, leaving the facial nerve intact. In the other cases, the facial nerve reconstruction with hypoglossal-facial anastomosis or interposition graft was performed. The postoperative facial function was House-Brackmann grade IV in most cases (88.2%). In terms of the functional recovery classified by complete or incomplete eye closure, the moderate preoperative facial nerve palsy group showed a better functional outcome than severe group. CONCLUSION: In cases with good facial nerve function, it would be better to consider an alternative method for preserving the facial nerve. Furthermore, when facial nerve paralysis has developed to more than House-Brackmann grade III, an immediate operation is recommended to obtain a good postoperative facial functional recovery.

Adolescent↗

PubMed2003

PET evidence of neuroplasticity in adult auditory cortex of postlingual deafness.

UNLABELLED: Controversy regarding functional reorganization in the adult brain remains. To investigate whether neuroplasticity is present in adults with postlingual deafness, we examined the pattern of cerebral glucose metabolism on (18)F-FDG brain PET images of postlingually deaf patients by comparing the auditory cortical activation pattern with those of age- and sex-matched healthy control subjects. We also correlated the cerebral glucose metabolism in deaf patients with the duration of deafness using statistical parametric mapping. METHODS: In the resting state (eye closed, ears unoccluded in a dark and quiet environment), (18)F-FDG brain PET scans were performed on 9 postlingually deaf patients and 9 age- and sex-matched healthy volunteers. Significant increases and decreases of regional cerebral metabolism in the patient group were estimated by comparing their PET images with those of the healthy volunteers using t statistics at every voxel. To reveal regions in which metabolism was significantly correlated with the duration of deafness, the general linear model with the duration of deafness as a covariate was tested at each voxel. RESULTS: When we compared (18)F-FDG brain PET images of postlingually deaf patients with those of age- and sex-matched healthy control subjects by performing a t test at every voxel, the glucose metabolism of deaf patients was significantly (P < 0.001) lower than that of the control subjects in both anterior cingulate gyri (Brodmann area 24 [BA24]) and superior temporal cortices (BA41, BA42) and in the right parahippocampal gyrus. No area showed a significant increase of metabolism in deaf patients with the same threshold. When we correlated glucose metabolism of deaf patients with the duration of deafness after total deprivation of hearing capability using a general linear model with the duration of deafness as a covariate at every voxel, metabolism in both anterior cingulate gyri (BA24) and superior temporal cortices (BA41, BA42) showed a significant (P < 0.005) positive correlation with the duration of deafness. CONCLUSION: This study suggests that plasticity is present in adult brains of postlingually deaf patients. In the mature brain, auditory deprivation decreased neuronal activity transiently in primary auditory and auditory-related cortices, and, over time, functional reorganization likely takes place in the auditory cortex. Plasticity was prominent in superior temporal and anterior cingulate gyri in the sensory-deprived mature brain and militated against postimplantation improvement in patients with cochlear implants.

Adult↗

PubMedDate not supplied

Nasopharyngeal carcinoma with skull base invasion: a necessity of staging subdivision.

PURPOSE: To investigate prognostic values of nasopharyngeal carcinoma (NPC) with skull base invasion for optimal management, according to its extent of involvement. METHODS: From January 1985 through December 2000, 119 patients with histologically proven NPC were analyzed retrospectively with review of their computed tomography/magnetic resonance imaging and medical records. All patients underwent sequential chemoradiotherapy except 2 cases, which were treated concurrently. The mean duration of follow-up was 61 months (range 8-179). Potential prognostic factors were evaluated by univariate and multivariate analyses by the Kaplan-Meier method and the Cox model, with a particular emphasis on the extent of skull base invasion. RESULTS: Skull base invasion was found in 46 (38.6%) of 119 patients. Cranial nerve palsy and intracranial extension was discovered in 34 (28.6%) and 23 (19.3%) of these patients, respectively. The sole erosion of the skull base was not found to be a poor prognostic factor. Patients with involvement of both anterior (I-VIII) and posterior (IX-XII) cranial nerves had a worse prognosis than those with involvement of either anterior or posterior cranial nerves (P = 0.0219). The presence of intracranial extension was the worst prognostic factor in NPC with skull base invasion (P = 0.0269). The advanced neck stage and histology did not affect the prognosis of NPC in the presence of skull base invasion. CONCLUSION: Our results show that NPC with skull base invasion should be divided into the groups with, simple skull base erosion, minimal involvement of either anterior or posterior cranial nerves, multiple involvements of both cranial nerves, and intracranial extension.

Adolescent↗