Chul Han Kim

Soonchunhyang University, Onyang, Chungcheongnam-do, South Korea

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Publications (62)69.16 Total impact

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    ABSTRACT: Background: Reactive oxygen species (ROS) play an important role in the induction of apoptosis under pathological conditions. Recently, a significant increase in ROS production and disrupted apoptosis mechanisms in keloids have been reported. Nuclear factor erythroid 2-related factor 2 (Nrf2) represents one of the most important cellular defense mechanisms against oxidative stress and is implicated in the regulation of apoptosis. Recently, it has been reported that Nrf2 upregulates Bcl-2, an anti-apoptotic protein. Objective: To compare Nrf2 protein expression in normal skin tissues to keloid tissues. Methods: ROS generation in keloid tissues was evaluated with OxyBlot analysis. Western blotting and/or immunohistochemical staining approaches were used to study expression of Nrf2 or Bcl-2 in keloid and normal skin tissues. Cellular fractionation was performed to examine subcellular distribution of Nrf2. Transfection of fibroblasts with Nrf2-specific small interfering RNA (siRNA) was conducted to understand the relationship between Nrf2 expression and apoptosis induction. Results: Protein oxidation, a marker of oxidative stress, is increased in keloid tissues. Western blot analysis clearly showed that Nrf2 and Bcl-2 are downregulated in keloid tissues. Immunohistochemical staining of Nrf2 confirmed the results of the western blot analysis. Transfection of fibroblasts with the Nrf2-specific siRNA results in increased apoptosis and decreased cell viability. Conclusion: Collectively, our data indicate that Nrf2 expression is downregulated in keloid tissues, and that Nrf2 is involved in the development of apoptosis in Nrf2 siRNA-transfected fibroblasts. We propose that a defective antioxidant system and apoptotic dysregulation may participate in keloid pathogenesis.
    Full-text · Article · Oct 2015 · Annals of Dermatology
  • Chul Han Kim
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    ABSTRACT: The impact of equivalent optical bandwidth on the performance of a system using a reflective electroabsorption modulator (R-EAM) based optical source has been experimentally evaluated with signals operating at 2.5 Gb/s and beyond. The equivalent optical bandwidth of our source with a broadband seed light was simply adjusted by using a bandwidth tunable optical filter. From the measurements, we have estimated the required equivalent optical bandwidth of our source for an error-free transmission (@ bit-error-rate of 10-12) and a forward error correction (FEC) threshold of 2 × 10-4.
    No preview · Article · Aug 2015 · Journal of the Optical Society of Korea
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    ABSTRACT: We demonstrate a spectrum-sliced wavelength-division-multiplexed passive optical network with the channel spacing of 25 GHz, where even and odd channels are spectrum sliced separately using a pair of 50-GHz arrayed-waveguide gratings (AWGs). The 50-GHz AWGs have an offset of 25 GHz with respect to each other. Similarly, the demultiplexing is done using a pair of 50-GHz AWGs for even and odd channels separately. Our use of 50-GHz AWGs gives better bit-error rate performances than using 25-GHz AWGs in a conventional way. With 50-GHz AWGs, the channel bandwidth is increased about two times larger than using 25-GHz AWGs. Moreover, the increased spectral overlap between adjacent channels produces relatively small crosstalk since the channels are incoherent and their intensity noise is absorbed by reflective semiconductor amplifiers. The 25-GHz spaced spectrum-sliced WDM passive optical network can be realized more easily using 50-GHz AWGs since 50-GHz AWGs are more available in the market than 25-GHz AWGs.
    No preview · Article · Jul 2015 · IEEE Photonics Technology Letters
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    Jang Hyun Lee · Jin Young Kim · Chul Han Kim

    Preview · Article · Jul 2015 · Yonsei medical journal
  • Ki-Young Lee · Chul Han Kim · Dongwook Park · Chang-Min Kim
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    ABSTRACT: The validity of applying the Modified Airy Function (MAF) method to the problems of graded-index optical waveguides and graded potential barrier analysis was critically examined. In the former case, the method yielded very accurate results from the derived eigenvalue equations. In the latter case, however, the same method produced results that deviated significantly from exact numerical results for barriers with a smooth peak. The causes of the discrepancies were investigated in detail.
    No preview · Article · Apr 2015 · Journal of the Optical Society of Korea
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    ABSTRACT: The authors report a rare case of Horner syndrome in a patient with neurofibromatosis type 1 (NF-1). A 31-year-old man visited the clinic with drooping left eyelid. The physical examination revealed ptosis of the left eyelid, miotic pupil, facial anhidrosis, and several skin masses on the chest. The radiological examination of the chest demonstrated a well-defined left posterior mediastinal mass close to the vertebral bodies of the upper thoracic spine at the level of T1-T5. The masses of mediastinum and skin were totally removed. They were diagnosed as neurofibromas. Neurofibromatosis type 1 was diagnosed. To the best of my knowledge, this is a rare case of a patient with NF-1 who presented with Horner syndrome. Clinicians should be vigilant on the possibility of Horner syndrome in patients with NF-1.
    No preview · Article · Dec 2014 · Journal of Craniofacial Surgery
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    ABSTRACT: Background Reactive oxygen species (ROS) damages cell molecules, and modifies cell signaling. The nuclear factor E2-related factor (Nrf2) is a critical transcription regulator, which protects cells against oxidative damage. Nrf2 expression is increased in a large number of cancers. However, little information has been reported regarding the expression of Nrf2 in skin cancers. Hence, we explored the expression of Nrf2 protein in skin cancers. Methods The Nrf2 protein expression in 24 specimens, including 6 malignant melanomas (MM), 6 squamous cell carcinomas (SCC), 6 basal cell carcinomas (BCC), and 6 normal skin tissues, was evaluated by western blotting. Immunohistochemical staining was performed. The expression of Kelch-like ECH-associated protein 1 (Keap1), the key regulator of Nrf2, was also analyzed by western blotting. Results Small interfering RNA transfection to the melanoma cell line G361 confirmed that an approximately 66 kDa band was the true Nrf2 band. The western blot revealed that the Nrf2 protein was definitely expressed in normal skin tissues, but the Nrf2 expression was decreased in MM, SCC, and BCC. Immunohistochemical examination showed that expression of Nrf2 was decreased in all skin cancer tissues compared to the normal skin tissues. Keap1 was not expressed in all malignant skin tumors and normal skin tissues by western blot. Conclusions ROS was increased in various types of cancers which proteins were highly expressed or underexpressed. This study demonstrated that the expression of Nrf2 protein was down-regulated in human malignant skin tumors. We suggest that decreased expression of Nrf2 is related to skin cancers.
    Preview · Article · Nov 2014 · Archives of Plastic Surgery
  • Byoung-Wook Kang · Kwanil Lee · Sang Bae Lee · Chul Han Kim
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    ABSTRACT: We have demonstrated an amplified wavelength-division multiplexed (WDM) passive optical network (PON) by using broadband light source (BLS) seeded optical sources and chirped fiber Bragg gratings (FBGs) based dispersion compensators. Chirped FBGs located at central office (CO) were fabricated and used as channel-by-channel dispersion compensators in order to mitigate the dispersion-induced distortion of both downstream and upstream signals. Owing to a low insertion loss of chirped FBG based dispersion compensator, the optical signal-to-noise ratio (OSNR) of the downstream signal could be improved to be ~28 dB. Thus, we re-confirmed that an error-free transmission of 1.25 Gb/s signals over a 100 km single-mode fiber (SMF) link could be achieved with a proposed amplified WDM-PON architecture. We have also evaluated the impact of various noises on the system's performance, and found that the low OSNR of the downstream signal would be a main limiting factor on the maximum reach of the proposed amplified WDM-PON architecture. From the measured ~13 dB improvement in OSNR of the downstream signal compared to our previously-proposed dispersion compensating module based scheme, we believe that the proposed architecture can accommodate a reach of longer than 100 km SMF link easily.
    No preview · Article · Oct 2014 · Journal of the Optical Society of Korea
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    ABSTRACT: Background Patients with diabetes mellitus often have a difficult life, suffering from foot ulceration or amputation. Diabetes is characterized by chronic inflammation, and one of the features of inflammation is hypoxia. Recently, it has been reported that KAI1 is a hypoxia target gene. There is no published research on hypoxia-related KAI1 protein levels in human diabetic skin. Therefore, we have investigated the expression of KAI1 protein in diabetic skin tissue in vivo. Methods The expression of KAI1 protein was evaluated by western blotting in 6 diabetic skin tissue samples and 6 normal skin samples. Immunohistochemical staining was carried out to identify KAI1 expression. Results The western blotting revealed significantly increased expression of the KAI1 protein in diabetic skin tissues as compared to normal skin tissues. Immunohistochemical examination demonstrated that KAI1 was expressed in all diabetic skin tissues with moderate-to-strong positivity and weakly expressed in normal skin tissues. Conclusions Our data suggest that a high expression of the KAI1 protein can be observed in diabetic skin tissue. To the best of our knowledge, this is the first report suggesting that KAI1 protein expression in diabetic skin tissues may be associated with chronic inflammatory states and hypoxia.
    Full-text · Article · May 2014 · Archives of Plastic Surgery
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    ABSTRACT: Primary mucosal melanomas of the head and neck are rare. In addition, second primary mucosal melanoma following primary cutaneous malignant melanomas is very rare. We report a second primary mucosal melanoma. A 76-year-old woman, who had a previously cutaneous malignant melanoma of the left foot, visited with a complaint of a foreign body sensation of the throat. Endoscopy revealed a black mass at the left piriform sinus of the hypopharynx. After wide surgical excision of the lesion and reconstruction with a radial forearm free flap, the histopathology was confirmed to be a second primary mucosal malignant melanoma of the hypopharynx. Five months postoperatively, masses were palpated in the neck, and metastasis was diagnosed. The patient was treated with adjuvant chemotherapy and radiotherapy. Eight months postoperatively, computed tomography scans showed other metastatic masses in the liver, spleen, both adrenal glands, soft tissues of the abdominal wall, and both lungs. After that, the patient died 9 months postoperatively. We report a rare case of second primary mucosal malignant melanoma of the hypopharynx. Although rare, this case shows that a detailed examination of the hypopharynx and the head and neck should be a part of the follow-up examination in all cutaneous malignant melanoma patients.
    No preview · Article · Feb 2014 · The Journal of craniofacial surgery
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    Moon Kyun Cho · Je Min An · Chul Han Kim · Sang Gue Kang

    Preview · Article · Jan 2014 · Archives of Plastic Surgery
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    Moon Kyun Cho · Je Min An · Chul Han Kim · Sang Gue Kang
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    ABSTRACT: Aurora kinase A (Aurora-A) plays an important role in the regulation of mitosis and cytokinesis. Dysregulated Aurora-A leads to mitotic faults and results in pathological conditions. No studies on Aurora-A expression in human diabetic skin tissue have been reported. In light of this, we explored the expression of Aurora-A in human diabetic skin tissue. Aurora-A protein was evaluated by western blotting in 6 human diabetic skin tissue and 6 normal skin specimens. Increased expression of Aurora-A protein was detected in all diabetic skin tissue samples in both western blot analysis and immunohistochemical staining. However, in the case of the normal skin tissue, no bands of Aurora-A protein were detected in either the western blotting analysis or the immunohistochemical staining. Thus far, there have been no studies on the expression of Aurora-A in diabetic skin tissue. However, we believe that oxidative DNA damage related to the expression of Aurora-A protein and Aurora-A could be involved inhuman diabetic skin tissue.
    Preview · Article · Jan 2014 · Archives of Plastic Surgery
  • Chul Han Kim
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    ABSTRACT: The author reports a rare case of Horner syndrome in a patient who resulted from stenosis of the vertebral artery after blunt trauma. A 31-year-old man was transferred to our department for evaluation of left medial orbital wall and nasal bone fractures. Five days ago, he was hospitalized due to multiple second to fourth rib fractures of the right chest following blunt trauma of the face, neck, and chest. Surgery was performed. Ten days later, he complained of drooping of the right eyelid. Physical examination revealed a discrete miosis and ptosis with normal levator function in the right eye. A workup for Horner syndrome was performed. Magnetic resonance angiography of the head and neck revealed a stenosis of the distal part of the right vertebral artery without the abnormality of carotid artery. He wore a cervical collar and underwent anticoagulation. However, Horner syndrome was not resolved over the next 12 months. Acute traumatic Horner syndrome may be associated with vertebral artery dissection in which the possibility of life-threatening injury can be masked.
    No preview · Article · Nov 2013 · The Journal of craniofacial surgery
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    Chul Han Kim
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    ABSTRACT: Diabetes is characterized by chronic hyperglycemia, which can increase reactive oxygen species (ROS) production by the mitochondrial electron transport chain. The formation of ROS induces oxidative stress and activates oxidative damage-inducing genes in cells. No research has been published on oxidative damage-related extracellular superoxide dismutase (EC-SOD) protein levels in human diabetic skin. We investigated the expression of EC-SOD in diabetic skin compared with normal skin tissue in vivo. The expression of EC-SOD protein was evaluated by western blotting in 6 diabetic skin tissue samples and 6 normal skin samples. Immunohistochemical staining was also carried out to confirm the EC-SOD expression level in the 6 diabetic skin tissue samples. The western blotting showed significantly lower EC-SOD protein expression in the diabetic skin tissue than in the normal tissue. Immunohistochemical examination of EC-SOD protein expression supported the western blotting analysis. Diabetic skin tissues express a relatively small amount of EC-SOD protein and may not be protected against oxidative stress. We believe that EC-SOD is related to the altered metabolic state in diabetic skin, which elevates ROS production.
    Preview · Article · Sep 2013 · Archives of Plastic Surgery
  • Chul Han Kim · Jang Hyun Lee
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    ABSTRACT: The authors retracted the infraorbital nerve (ION) using a vessel loop to explore the orbital floor fracture site and analysed when the traction of the ION was needed. In ninety-one patients, the location of the fracture according to its position relative to the infraorbital groove, the location of the infraorbital groove from the midpoint of the orbital floor, and involvement of the ION in the fracture site were recorded retrospectively from computed tomography scans. An analysis of any associations between the traction of ION and the location of the fracture and ION passage was performed. Traction of the ION was performed in 14 cases, of which 10 cases had involvement of the ION in the fracture site and 4 cases did not. All of them were posterior fractures. In 51 cases with posterior fractures, the ION passage in patients who had ION traction was statistically located more medially (0.50 ± 1.19 mm) than in patients who had no traction (2.38 ± 1.12 mm) (p < 0.05). The ION may interfere with the exposure of the fracture site in a posterior orbital floor fracture with the involvement of the ION in the fracture site and a medially located ION passage.
    No preview · Article · Jul 2013 · Journal of cranio-maxillo-facial surgery: official publication of the European Association for Cranio-Maxillo-Facial Surgery
  • Chul Han Kim
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    ABSTRACT: The performance of reflective electro-absorption modulator (R-EAM) based optical source has been evaluated for the use in high-capacity wavelength-division multiplexed passive optical networks (WDM-PONs). In our measurements, a broadband light source (BLS) was used as a seeding source for the cost-effective implementation of R-EAM based optical source. At first, a bit-error rate (BER) floor at 10<sup>-6</sup> was observed even in a back-to-back configuration with the BLS seeded R-EAM source. This is mainly because of the excess intensity noise (EIN) within BLS and the signal-to-noise ratio (SNR) degradation induced by a high insertion loss of R-EAM. To mitigate both effects of EIN and SNR degradation, a reflective semiconductor optical amplifier (RSOA) was also used for the implementation of our BLS seeded R-EAM source. Then, we have evaluated the impact of various noises, such as EIN, chromatic dispersion of transmission fiber and in-band crosstalk, on the system's performance using our BLS seeded R-EAM optical source. From the results, we have found that a 3-dB bandwidth of the BLS seeded R-EAM optical source should be wider than ~0.8 nm to achieve an error-free transmission of 1.25 Gb/s signal. We have also confirmed that there was a trade-off between the dispersion- and the in-band crosstalk-induced penalties due to the wide source bandwidth of our BLS seeded R-EAM source, like the cases of BLS seeded RSOA and Fabry-Perot laser diode (FP-LD) sources.
    No preview · Article · May 2013 · Optics Express
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    Chul Han Kim

    Preview · Article · May 2013 · Archives of Plastic Surgery
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    Chul Han Kim

    Preview · Article · Jan 2013 · Archives of Plastic Surgery
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    Chul Han Kim

    Preview · Article · Nov 2012 · Archives of Plastic Surgery
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    Chul Han Kim

    Preview · Article · Nov 2012 · Archives of Plastic Surgery

Publication Stats

225 Citations
69.16 Total Impact Points

Institutions

  • 2010-2015
    • Soonchunhyang University
      • College of Medicine
      Onyang, Chungcheongnam-do, South Korea
  • 2005-2015
    • University of Seoul
      • School of Electrical and Computer Engineering
      Sŏul, Seoul, South Korea
  • 2008
    • Yonsei University Hospital
      • Department of Internal Medicine
      Seoul, Seoul, South Korea
    • Korea Advanced Institute of Science and Technology
      • Department of Electrical Engineering
      Sŏul, Seoul, South Korea
  • 2007
    • Hanyang University
      Sŏul, Seoul, South Korea