Tae-Hoon Kang

Hanyang University Medical Center, Sŏul, Seoul, South Korea

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Publications (12)24.47 Total impact

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    ABSTRACT: Primary central nervous system (CNS) sarcomas are exceedingly rare, and, to the best of our knowledge, there has not yet been a report of intramedullary sarcoma. Here, we report a primary intradural intramedullary sarcoma of the spinal cord in a four-year-old boy who presented with low back pain and a radiculopathy involving both lower extremities. The tumor showed significant enhancement on magnetic resonance (MR) images due to its extreme vascularity. Gross total tumor removal was performed with microelectrical pulse recording, and the patient also received adjuvant radiotherapy and chemotherapy. After the operation, the patient's sensory deficits were improved. Because CNS dissemination is common, entire neuraxis evaluation is essential, although there was no evidence of dissemination in this case. The prognosis of primary CNS sarcoma is poor due to infiltrative nature and early CNS dissemination is common, and the treatment of choice is radical surgical resection. Adjuvant therapy is also beneficial with radiotherapy and chemotherapy.
    Journal of Korean Neurosurgical Society 11/2010; 48(5):448-51. · 0.60 Impact Factor
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    ABSTRACT: In the mammalian retina, information concerning various aspects of an image is transferred in parallel, and cone bipolar cells are thought to play a major role in this parallel processing. We have examined the synaptic connections of calbindin-immunoreactive (IR) ON cone bipolar cells in the inner plexiform layer (IPL) of rabbit retina and have compared these synaptic connections with those that we have previously described for neurokinin 1 (NK1) receptor-IR cone bipolar cells. A total of 325 synapses made by calbindin-IR bipolar axon terminals have been identified in sublamina b of the IPL. The axons of calbindin-IR bipolar cells receive synaptic inputs from amacrine cells through conventional synapses and are coupled to putative AII amacrine cells via gap junctions. The major output from calbindin-IR bipolar cells is to amacrine cell processes. These data resemble our findings for NK1 receptor-IR bipolar cells. However, the incidences of output synapses to ganglion cell dendrites of calbindin-IR bipolar cells are higher compared with the NK1-receptor-IR bipolar cells. On the basis of stratification level and synaptic connections, calbindin-IR ON cone bipolar cells might thus play an important role in the processing of various visual aspects, such as contrast, orientation, and approach sensing, and in transferring rod signals to the ON cone pathway.
    Cell and Tissue Research 11/2009; 339(2):311-20. · 3.68 Impact Factor
  • Chung-Pyo Hong, Tae-Hoon Kang, Shin-Dug Kim
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    ABSTRACT: An intelligent network management should be designed to satisfy all the requirements of applications designed for ubiquitous computing environment. Recently there may be several heterogeneous network interfaces in the same location, where a mobile terminal needs switching from one wireless interface to another. However, most of vertical handoff mechanisms are based on the network information or requirements of any single application. Thus, they cannot perform vertical handoff (VHO) at the right time and do not satisfy all the applications running on any mobile terminal. To overcome this problem, we propose an efficient scheme to solve multi-application situation by designing application manager and VHO decision manager. The proposed scheme performs VHO after checking the quality of service (QoS) in factor by factor. Factors of the abstracted profile are used to verify the QoS of networks. By performing VHO in this way, we can design an effective handoff decision algorithm and consequently this algorithm provides a multi-application oriented and QoS enhanced VHO scheme.
    Embedded Software and Systems, 2005. Second International Conference on; 01/2006
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    ABSTRACT: Despite the importance of seamless connectivity in ubiquitous computing, research for seamless connectivity has not been considered properly. To provide seamless connectivity, this paper proposes an application execution model for seamless services with an intelligent context-aware handoff scheme based on context information, such as user intentions and application requirements as well as issues of network layer. In this paper, we define several profiles reflecting various context informations and design basic modules organizing middleware architecture for seamless service management and efficient vertical handoff (VHO) management. Consequently, the proposed seamless service management with context-aware handoff scheme provides service continuity in ubiquitous computing environment by preventing unnecessary handoffs, changing application service modes adaptively, and eventually maintaining optimal network configuration. And also simulation results show about 38% enhanced performance in the processing rate, about 13% enhanced performance from service continuity, and about 29% enhanced performance in the processing time, compared with conventional schemes.
    Management of Convergence Networks and Services, 9th Asia-Pacific Network Operations and Management Symposium, APNOMS 2006 Busan, Korea, September 27-29, 2006, Proceedings; 01/2006
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    Chung-Pyo Hong, Tae-Hoon Kang, Shin-Dug Kim
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    ABSTRACT: Specifically ubiquitous computing paradigm is based on seamless connectivity. And also to guarantee the seamless connectivity, an intelligent network management between heterogeneous network interfaces, called vertical handoff (VHO), should be designed. Besides, conventional VHO schemes are based on network information only, and do not provide any service manage-ment scheme for seamless service. For this reason, this paper proposes a middleware architecture supporting efficient seamless connectivity with service management. In this architecture, we define modules to perform VHOs in accordance with contexts of services, user intention as well as network information. And also we define profiles used to express the contexts related to the process of VHOs and service management. With the proposed scheme, we can reduce the number of unnecessary VHOs and application failures significantly. This leads to around 130% of enhancement in data throughput, and also 85% of application failures can be reduced.
    Management of Convergence Networks and Services, 9th Asia-Pacific Network Operations and Management Symposium, APNOMS 2006 Busan, Korea, September 27-29, 2006, Proceedings; 01/2006
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    ABSTRACT: Despite the importance of seamless connectivity in ubiquitous computing, research for seamless connectivity is not considered properly. To provide seamless connectivity, this paper proposes intelligent context- aware handoff management scheme and middleware architecture. In this paper, we defined our own profiles about various contexts like user intentions as well as issues of network layer and designed modules for efficient vertical handoff (VHO) management and continuous service. Consequently, proposed context-aware handoff management scheme prevents unnecessary handoff cases and eventually maintains optimal network configuration in ubiquitous computing environment. And also simulation results show about 40% enhanced performance in the number of VHOs and about 20% enhanced performance in throughput compared with conventional schemes.
    Proceedings of the 2006 International Conference on Pervasive Systems & Computing, PSC 2006, Las Vegas, Nevada, USA , June 26-29, 2006; 01/2006
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    ABSTRACT: Using immunocytochemistry, a type of amacrine cell that is immunoreactive for aquaporin 1 was identified in the mouse retina. AQP1 immunoreactivity was found in photoreceptor cells of the outer nuclear layer (ONL) and in a distinct type of amacrine cells of the inner nuclear layer (INL). AQP1-immunoreactive (IR) amacrine cell somata were located in the INL and their processes extended through strata 3 and 4 of the inner plexiform layer (IPL) with thin varicosities. The density of the AQP1-IR amacrine cells increased from 100/mm(2) in the peripheral retina to 350/mm(2) in the central retina. The AQP1-IR amacrine cells comprise 0.5% of the total amacrine cells. The AQP1-IR amacrine cell bodies formed a regular mosaic, which suggested that they represent a single type of amacrine cell. Double labeling with AQP1 and glycine, gamma-aminobutyric acid (GABA) or GAD(65) antiserum demonstrated that the AQP1-IR amacrine cells expressed GABA or GAD(65) but not glycine. Their synaptic input was primarily from other amacrine cell processes. They also received synaptic inputs from a few cone bipolar cells. The primary synaptic targets were ganglion cells, followed by other amacrine cells and cone bipolar cells. In addition, gap junctions between an AQP1-IR amacrine process and another amacrine process were rarely observed. In summary, a GABAergic amacrine cell type labeled by an antibody against AQP1 was identified in the mouse retina and was found to play a possible role in transferring a certain type of visual information from other amacrine or a few cone bipolar cells primarily to ganglion cells.
    The Journal of Comparative Neurology 09/2005; 488(3):352-67. · 3.66 Impact Factor
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    ABSTRACT: We have investigated and further characterized, in the rabbit retina, the synaptic connectivity of the ON-type cone bipolar cells that are immunoreactive for an antibody against the neurokinin-1 receptor (NK1R). NK1R-immunoreactive bipolar cell axons terminate in stratum 4 of the inner plexiform layer. The axons of NK1R-positive bipolar cells receive synaptic inputs from amacrine cells through conventional synapses and from putative AII amacrine cells via gap junctions. The major outputs from NK1R-positive bipolar cells make contacts with amacrine cell processes. The most frequent postsynaptic dyads comprise two amacrine cell processes. Double-labeling experiments with antibodies against NK1R and either calretinin or glycine have demonstrated that NK1R-immunoreactive bipolar cells form gap junctions with AII amacrine cells. Thus, NK1R-positive cone bipolar cells, together with calbindin-positive cone bipolar cells, may play an important role in transferring rod signals to the ON-type ganglion cells of the cone pathway in the rabbit retina.
    Cell and Tissue Research 08/2005; 321(1):1-8. · 3.68 Impact Factor
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    ABSTRACT: DBA/2J (D2) mice develop a form of progressive pigmentary glaucoma with increasing age. We have compared retinal cell populations of D2 mice with those in control C57BL/6J mice to provide information on retinal histopathology in the D2 mouse. The D2 mouse retina is characterized by a reduction in retinal thickness caused mainly by a thinning of the inner retinal layers. Immunocytochemical staining for specific inner retinal neuronal markers, viz., calbindin for horizontal cells; protein kinase C (PKC) and recoverin for bipolar cells, glycine, gamma-aminobutyric acid (GABA), choline acetyltransferase (ChAT), and nitric oxide synthase (NOS) for amacrine cells, and osteopontin (OPN) for ganglion cells, was performed to detect preferentially affected neurons in the D2 mouse retina. Calbindin, PKC, and recoverin immunoreactivities were not significantly altered. Amacrine cells immunoreactive for GABA, ChAT, and OPN were markedly decreased in number, whereas NOS-immunoreactive amacrine cells increased in number. However, no changes were observed in the population of glycine-immunoreactive amacrine cells. These findings indicate a significant loss of retinal ganglion and some amacrine cells, whereas glycinergic amacrine cells, horizontal, and bipolar cells are almost unaffected in the D2 mouse. The reduction in amacrine cells appears to be attributable to a loss of GABAergic and particularly cholinergic amacrine cells. The increase in nitrergic neurons with the consequent increase in NOS and NO may be important in the changes in the retinal organization that lead to glaucomain D2 mice. Thus, the D2 mouse retina represents a useful model for studying the pathogenesis of glaucoma and mechanisms of retinal neuronal death and for evaluating neuroprotection strategies.
    Cell and Tissue Research 05/2005; 320(1):51-9. · 3.68 Impact Factor
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    ABSTRACT: We examined cholinergic cells in the retinas of BALB/C albino, C57BL/6J black, and 129/SvJ light chinchilla mice by using immunocytochemistry with specific antisera against choline acetyltransferase (ChAT). Two types of ChAT-immunoreactive amacrine cell bodies were found in the inner nuclear layer (INL) and ganglion cell layer in the retinas of all three mouse strains. They were distributed with mirror-image symmetry and their processes ramified in strata 2 and 4 of the inner plexiform layer. A distinct type of ChAT-immunoreactive cell was found only in C57BL/6J mouse retina. The somata of this third type of ChAT-immunoreactive cell were located in the outermost part of the INL, with their processes extending toward the outer plexiform layer. Double-labeling experiments demonstrated that these were not horizontal cells and that they were GABA-immunoreactive. The results suggested that these cells were probably "misplaced" cholinergic amacrine cells showing GABA immunoreactivity. This feature of the C57BL/6J mouse retina should be taken into account in studies of mutant mice having a mixed genetic background with a C57BL/6J contribution.
    Cell and Tissue Research 09/2004; 317(2):109-15. · 3.68 Impact Factor
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    ABSTRACT: Hyperpolarization-activated cation currents (I(h)) have been identified in neurons in the central nervous system, including the retina. There is growing evidence that these currents, mediated by the hyperpolarization-activated cyclic nucleotide-gated cation channel (HCN), may play important roles in visual processing in the retina. This study was conducted to identify and characterize HCN1-immunoreactive (IR) bipolar cells by immunocytochemistry, quantitative analysis, and electron microscopy. The HCN1-IR bipolar cells were a subtype of OFF-type cone bipolar cells and comprised 10% of the total number of cone bipolar cells. The axons of the HCN1-IR cone bipolar cells ramified narrowly in the border of strata 1 and 2 of the inner plexiform layer (IPL). These cells formed a regular distribution, with a density of 1,825 cells/mm(2) at a position 1 mm ventral to the visual streak, falling to 650 cells/mm(2) in the ventral periphery. Double-labeling experiments demonstrated that their axons stratified narrowly within and slightly proximal to the OFF-starburst amacrine cell processes. In the IPL, they were presynaptic to amacrine cell processes. The most frequent postsynaptic dyads formed of HCN1-IR bipolar cell axon terminals are pairs composed of both amacrine cell processes. These results suggest that these HCN1-IR cone bipolar cells might be the same as the DAPI-Ba1 bipolar population, and might therefore be involved in a direction-selective mechanism, providing inputs to the OFF-starburst amacrine cells and/or the OFF-plexus of the ON-OFF ganglion cells.
    The Journal of Comparative Neurology 01/2004; 467(3):389-402. · 3.66 Impact Factor
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    ABSTRACT: Hantaan virus (HTN) is a causative agent of hemorrhagic fever with renal syndrome (HFRS). Little is known of its pathogenesis or the molecular mechanisms underlying resistance to HTN infection. In the present study, DNA microarray technology was used to monitor changes in mRNA levels after HTN infection, to elucidate resistance mechanisms to viral infection by understanding virus-host interactions. We found that several interferon (IFN)-inducible genes were up-regulated in host cells infected with HTN. According to previous available data, IFNs have been reported to be inhibitory, but their mode of action has not been yet clear. In this study, the 2',5'-oligoadenylated synthetase (OAS) and Mx1 genes, not a double-stranded RNA-dependent protein kinase R (PKR), of the IFN response pathways are associated with antiviral activity during HTN infection. Furthermore, A549 cells treated with IFN-alpha were protected against HTN infection. Taken together, these results confirmed that IFN plays a role in cellular defenses against HTN infection at an early stage of the infection and revealed the resistance mechanism for HTN infection.
    Virus Genes 02/2003; 26(1):31-8. · 1.84 Impact Factor