Biomedical subjects

J W Chung

Publications and source records attributed to J W Chung.

At least 19 recordsLinked to original sources

PubMed2006

Immunosensor with a controlled orientation of antibodies by using NeutrAvidin-protein A complex at immunoaffinity layer.

The orientation of antibody was controlled by using NeutrAvidin-protein A complex on the gold surface of SPR biosensor. The surface density of receptor antibody (anti-hIgG) was compared by treatment of receptor antibody to the layer of avidin, NeutrAvidin, protein A, NeutrAvidin-protein A complex and bare gold surface of SPR biosensor. The ligand antibody (hIgG) was injected to each IA layer and the binding ratio of ligand antibody per unit receptor was estimated as a parameter of orientation control. The NeutrAvidin-protein A complex on gold surface of SPR biosensor showed the highest surface density of receptor antibody as well as the binding ratio of ligand antibody per receptor antibody. The NeutrAvidin-protein A complex was also prepared on biotin-labelled SAM, and the binding ratio of ligand per receptor was found to be significantly improved in comparison to the IA layer prepared by chemical coupling of receptor antibody to the SAM layer. The NeutrAvidin-protein A complex which showed the highest efficiency for the binding of ligand antibodies, was applied for the detection of a cancer marker called CEA. By using NeutrAvidin-protein A complex and sandwich assay for signal amplification, sensitivity was improved to be 1.5-fold higher than bare gold surface and the detection of CEA with the detection limit of 30 ng/ml was achieved.

Antigen-Antibody Complex↗

PubMed2006

Sequential analysis of multiple analytes using a surface plasmon resonance (SPR) biosensor.

A sequential analysis method for the analysis of two analytes was developed using a surface plasmon resonance (SPR) biosensor. A sample with both analytes was introduced into the single sensing region and then each analyte was analyzed sequentially. Two detection models were devised for the samples with the following composition: (1) one target analyte resulting in a sensor response without any label and the other analyte with only additional label, (2) both target analytes requiring additional labels for detection. A standard curve for each model was prepared and applied for sequential analysis of anti-bovine serum albumin (anti-BSA) antibodies and horseradish peroxidase (HRP). The errors of the sequential analysis of Models 1 and 2 were found to be less than 6%, and this method was therefore acceptable for application. No cross-reaction arising from non-specific binding among the participating antigens and antibodies was shown to occur in Models 1 and 2. For optimization of the analyte binding capacity of immunoaffinity (IA), the concentration ratio of the molecular recognition element at the immobilization step was adjusted. Subsequently, from the measurement of the maximum sensor response (R(max)), optimization of the analyte binding capacity could be made. Using Model 2, the feasibility of sequential analysis was demonstrated by detecting levels of human chorionic gonadotropin (hCG) and human albumin (hA) in healthy human urine, since both proteins are known to be related to abortion and preterm delivery during early pregnancy.

Albumins↗

PubMed2006

Lipo-prostaglandin E1 in combination with steroid therapy is effective for treatment of sudden sensorineural hearing loss in Korean patients with Type 2 diabetes.

BACKGROUND: Diabetes mellitus is a risk factor for sudden sensorineural hearing loss (SSNHL), possibly as a result of microvascular damage, increased blood viscosity and embolic and thrombotic episodes. Aim To perform a prospective, randomized clinical trial to determine the therapeutic effect of lipo-prostaglandin E(1) (lipo-PGE(1)) on SSNHL in Korean patients with Type 2 diabetes. METHODS: The study group consisted of 270 consecutive Korean patients (130 male, 140 female) in whom SSNHL was diagnosed. Patients were classified as diabetic or non-diabetic by the new American Diabetes Association criteria. With the approval of the institute ethics committee, patients were randomly assigned to treatment with of 10 microg lipo-PGE(1) (lipo-PGE(1) group) given as a continuous infusion over 5 days, or saline (placebo group). In addition, all patients studied were treated with 48 mg methylprednisolone for 5 days. RESULTS: The overall recovery rates after treatment were 51.5% in diabetic and 64.2% in non-diabetic patients. In diabetic patients, there was a significantly higher rate of hearing improvement in the lipo-PGE(1) group (64.7%) compared with the placebo group (37.5%), whereas, in non-diabetic patients, there was no significant difference in rate of hearing improvement between the lipo-PGE(1) group (70.3%) and the placebo group (58.3%). CONCLUSION: Lipo-PGE(1) may have beneficial effects in the treatment of SSNHL in Korean patients with Type 2 diabetes.

Alprostadil↗

PubMed2005

New immobilization method for immunoaffinity biosensors by using thiolated proteins.

A new immobilization method for immunoaffinity (IA) biosensors that ensures the high surface density and the stability of the IA layer was developed. For the immobilization of biomolecules, the molecular recognition protein was first thiolated by covalent conjugation of mercaptopropionic acid, and then the thiolated protein was attached on the gold surface of the transducer. In this work, horseradish peroxidase (HRP) and its antibody were used as a model antigen-antibody, and the following properties of the IA layer prepared by thiolated protein were estimated: (i) biological integrity of HRP after the immobilization process by using activity assay, (ii) charge transfer resistance by immobilization, (iii) mass loading by the surface plasmon resonance (SPR) biosensor, (iv) number of binding sites, and (v) feasibility test for the measurement of capacitive change by the antigen-antibody interaction. Based on these parameters, the immobilization method by using thiolated protein was determined to be feasible for application to IA biosensors.

Affinity Labels↗

PubMed2004

Kinetic roughening of ion-sputtered Pd(001) surface: beyond the Kuramoto-Sivashinsky model.

We investigate the kinetic roughening of Ar+ ion-sputtered Pd(001) surface both experimentally and theoretically. In situ real-time x-ray reflectivity and in situ scanning tunneling microscopy show that nanoscale adatom islands form and grow with increasing sputter time t. Surface roughness W(t) and lateral correlation length xi(t) follow the scaling laws W(t) approximately t(beta) and xi(t) approximately t(1/z) with the exponents beta approximately 0.20 and 1/z approximately 0.20, for an ion beam energy epsilon=0.5 keV, which is inconsistent with the prediction of the Kuramoto-Sivashinsky (KS) model. We thereby extend the KS model by applying the coarse-grained continuum approach of the Sigmund theory to the order of O(inverted Delta(4),h(2)), where h is the surface height, and derive a new term of the form inverted Delta(2)(inverted Delta h)(2) which plays a decisive role in describing the observed morphological evolution of the sputtered surface.

Journal Article↗

PubMed2004

Systemic-to-pulmonary venous shunt in superior vena cava obstruction: depiction on computed tomography venography.

PURPOSE: To describe computed tomography (CT) venographic appearances of systemic-to-pulmonary venous shunts with CT venography and three-dimensional reconstruction images from patients with superior vena cava obstruction. MATERIAL AND METHODS: From January 1994 to April 2002, CT venography was performed in 45 patients with superior vena cava obstruction using a single-detector helical CT scanner (n=38) and four-detector row CT scanner (n=7). Analysis of CT scan data included the cause and degree of venous obstruction, the presence of pleural thickening and enhancement, and the attenuation of pulmonary veins. The causative factor for systemic-to-pulmonary venous shunt was evaluated using the Fisher exact test. RESULTS: Systemic-to-pulmonary venous shunts were observed in four patients (9%) who had high-attenuated pulmonary veins and pleural enhancement on CT venography. Pleural thickening (P=0.01) and a history of pulmonary tuberculosis (P=0.034) are statistically significant risk factors. CONCLUSION: CT venography showed strong pleural enhancement and high-attenuated pulmonary veins indicating systemic-to-pulmonary venous shunts. Radiologists should study the earlier enhancement of pulmonary veins in patients with superior vena cava obstruction.

Adult↗

PubMed2002

Adsorbate-induced pinning of a charge-density wave in a quasi-1D metallic chains: Na on the In/Si(111)-(4x1) surface.

We find that foreign adsorbates acting as local impurities can induce a metal-insulator transition by pinning a charge-density wave (CDW) on the quasi-1D metallic In/Si(111)-(4x1) chain system. Our scanning tunneling microscopy image clearly reveals the presence of a new local 4x2 structure nucleated by Na adatoms at room temperature, which turns out to be insulating with a doubled periodicity along the chains. We directly determine a CDW gap energy Delta = 105+/-8 meV by identifying a characteristic loss peak in our high-resolution electron-energy-loss spectra. We thus report the first observation of a local impurity-derived Peierls-like reconstruction of a quasi-1D system.

Journal Article↗

PubMed2002

Synthesis of 188 Re-labelled long chain alkyl diaminedithiol for therapy of liver cancer.

Radioisotope-labelled lipiodol has been used in the therapy of liver cancer. Recently a lipiodol solution of 188Re-labelled diaminedithiol (DD) has been reported to show a high uptake in the liver cancer. We synthesized long-chain alkyl DD derivatives to improve their uptake and retention in tissue. As the length of the alkyl chain increased, tissue uptake and retention also increased due to hydrophobic interaction with lipiodol. Among the synthesized compounds, the lipiodol solution of 188Re-HDD, the DD derivative with the longest side chain (C16), is a promising agent for therapy of liver cancer.

Animals↗

PubMed2002

Effect of sustained contraction on motor unit action potentials and EMG power spectrum of human masticatory muscles.

The sequelae of a sustained clench are incompletely understood. Our experimental questions were to compare the responses of men and women, to compare masseter and anterior temporalis muscles, and to test hypotheses for the reduction of the median frequency of power spectra. We recorded duration, amplitude, number of phases, and area of the motor unit action potential before and after a sustained clench and the median frequency of the electromyographic power spectrum in 41 subjects. After the clench, the median frequency was lower, the action potential duration longer, the number of phases increased, and the area larger, but the amplitude was not different. Males and females failed to differ. Compared with the temporalis, the masseter had a lower median frequency, longer duration, larger number of phases, and increased area. Our results are consistent with a decrease in the conduction velocity of the muscle action potential as an explanation of the spectral shift.

Action Potentials↗

PubMed2001

Transient expression of phospholipase D1 in developing rat hippocampus.

We investigated the distribution of phospholipase D1 (PLD1) protein in the developing rat hippocampus using an affinity-purified peptide antibody against PLD1. Immunoreactivity for PLD1 was first seen in some scattered cells in the hippocampus at embryonic day 18. At postnatal day 1 (P1), many PLD1 immunoreactive cells were observed in the CA1 and CA3 sectors, subiculum and the hilus of the dentate gyrus. During the first postnatal week, there was an abrupt increase of immunoreactive neurons in the hippocampus, and their number and intensity peaked at P7. During the second postnatal week, there was an abrupt decrease in the number of immunoreactive hippocampal neurons. By P14, no significant labeling was found in the hippocampus. These results corresponded well with those from Western blot analysis, suggesting that PLD1 may regulate the developmental processes of hippocampal neurons.

Animals↗

PubMed2001

Acetylcholine-evoked calcium increases in Deiters' cells of the guinea pig cochlea suggest alpha9-like receptors.

The medial efferent system innervates outer hair cells in the organ of Corti. Neurotransmission at this synapse is mediated by acetylcholine (ACh) acting on nicotinic ACh receptors containing the alpha9 subunit. In addition to the sensory cells, the supporting cells of the mammalian cochlea also receive efferent innervation but the neurotransmitter(s) at these synapses are not known. We show slow transient increases of intracellular calcium evoked by ACh in isolated Deiters' cells of the guinea pig cochlea. The antagonists atropine, d-tubocurarine and strychnine blocked the ACh-effect. Nicotine was an ineffective agonist. The pharmacologic profile and the kinetics of the calcium response suggest an alpha9-like ACh receptor on Deiters' cells similar but not identical to that on the outer hair cells.

Acetylcholine↗

PubMed2001

Reorganization of horizontal cell processes in the developing FVB/N mouse retina.

We investigated the morphological changes of horizontal cells after postnatal photoreceptor degeneration in the developing FVB/N mouse retina, using immunocytochemistry with anti-calbindin D-28K. From postnatal day 14 (P14) onwards, processes emerging from horizontal cells descend into the inner plexiform layer (IPL) and ramify mainly in stratum 1 of the IPL. Electron microscopy revealed that the descending processes make synaptic contacts with bipolar cells in the outer plexiform layer. Our results clearly demonstrate that loss of photoreceptor cells induces the reorganization of horizontal cell processes in the retinas of FVB/N mice as they mature.

Animals↗

PubMed2001

Expression of osteopontin mRNA in developing rat brainstem and cerebellum.

This study was undertaken to investigate the developmental expression of osteopontin (OPN) in the rat brainstem and cerebellum by Northern blotting and in situ hybridization. The expression of OPN was noted in the mesencephalic Vth nucleus initially at embryonic day 16 (E16). At E20, the labeling extended into other brainstem nuclei including the cochlear, vestibular, facial motor, and hypoglossal nuclei. During the first week of postnatal life, the OPN signal in the brainstem increased markedly, and by P14, OPN expression was found in functionally diverse areas including motor-related areas, sensory relay nuclei, and the reticular formation. The adult labeling pattern was established in central neurons at this time. These results corresponded well with those from Northern blot analysis. On the basis of morphological and distribution criteria, the OPN signal in several nuclei appeared to be contained exclusively within neuronal soma. OPN expression in neurons occurred during the period of neuronal differentiation and increased with maturation. Our results therefore suggest that OPN contributes to developmental processes, including the differentiation and maturation of specific neuronal populations, in the rat brain.

Animals↗

PubMed2001

ATP and nitric oxide modulate intracellular calcium in isolated pillar cells of the guinea pig cochlea.

Supporting cells in the mammalian cochlea have recently received attention as potential targets of neurotransmitters, neuromodulators, and neurohumoral agents. Calcium homeostasis in Deiters' and Hensen's cells, for example, is regulated by ATP and nitric oxide. We studied the intracellular calcium concentration [Ca2+]i in isolated pillar cells of the guinea pig cochlea in response to extracellular ATP and nitric oxide using the fluorescent indicator fluo-3. [Ca2+]i increased rapidly and significantly throughout the pillar cell in response to a bolus of ATP or 2-methylthio ATP while alpha,beta-methylene ATP was ineffective. The response to ATP was inhibited by suramin and Cibacron Blue but not by pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid. This pharmacological profile is consistent with a [Ca2+]i increase largely mediated by P2Y receptors. In Ca2+-free medium supplemented with EGTA, the response to extracellularATP was reduced by 33%, suggesting a contribution of calcium influx to the overall effect. The ATP-induced increase of [Ca2+] was attenuated by NO donors (sodium nitroprusside or diethylamine NONOate), and this attenuation was reversed by KT5823, an antagonist to protein kinase G. The results indicate the involvement of purinergic mechanisms and the nitric oxide/cyclic GMP/protein kinase G pathway in the regulation of [Ca2+]i in cochlear pillar cells.

Adenosine Triphosphate↗

PubMed2001

Liver abscess after transcatheter oily chemoembolization for hepatic tumors: incidence, predisposing factors, and clinical outcome.

PURPOSE: To evaluate the incidence of, predisposing factors for, and clinical outcome of liver abscess developing in patients with hepatic tumors after transcatheter oily chemoembolization (TOCE). MATERIALS AND METHODS: During the past 6-year period, 2,439 patients with hepatic tumors underwent a total of 6,255 TOCE procedures. With a retrospective review of medical records, the authors evaluated the occurrence of liver abscess, the statistical significance of potential predisposing factors including portal vein obstruction, metastatic tumors, biliary abnormalities (type 1, simple biliary obstruction; type 2, status prone to ascending biliary infection), malignant gastrointestinal mucosal lesions, and additional gelatin sponge particle embolization in liver abscess formation, and the clinical outcome of abscess. RESULTS: Fifteen liver abscesses occurred in 14 patients (0.2%). Liver abscesses developed in three of 987 (0.3%) TOCE procedures for portal vein obstruction, three of 114 (2.6%) procedures for metastatic tumors, one of 49 (1.8%) for type 1 biliary abnormality, four of 55 (7.4%) for type 2 biliary abnormality, two of 18 (11.1%) for malignant gastrointestinal mucosal lesion, and nine of 2,108 (0.4%) for additional gelatin sponge particle embolization. Univariate and multivariate statistical analysis showed that type 2 biliary abnormality was a significant predisposing factor. The mortality related to liver abscess occurred in two patients (13.3%). Thirteen liver abscesses were successfully treated with parenteral antibiotics and percutaneous catheter drainage. However, irreversible deterioration of liver function occurred in two patients. Two of nine further TOCE procedures in three patients caused recurrent septicemia and liver abscess. CONCLUSION: The biliary abnormality prone to ascending biliary infection was the most important predisposing factor to the development of liver abscess after TOCE. Postembolic liver abscess could be effectively managed with percutaneous catheter drainage.

Anti-Bacterial Agents↗

PubMed2001

Chromosomal integration of the Vitreoscilla hemoglobin gene in Burkholderia and Pseudomonas for the purpose of producing stable engineered strains with enhanced bioremediating ability.

Using the pUT-miniTn5 vector system developed by the laboratory of K.N. Timmis, the Vitreoscilla hemoglobin gene (vgb) was integrated into the chromosomes of Pseudomonas aeruginosa and Burkholderia cepacia; Vitreoscilla hemoglobin (VHb) was expressed at 8.8 and 0.8 nmol/g wet weight of cells in the respective engineered strains. The vgb-bearing P. aeruginosa outgrew wild-type P. aeruginosa and degraded benzoic acid faster than the latter strain at both normal and low aeration. In contrast, the vgb-bearing B. cepacia strain had a growth advantage over the wild-type strain at ca. 90 ppm, but not at ca. 120 ppm 2,4-dinitrotoluene (DNT); no difference in DNT degradation was seen between the two strains at either normal or low aeration. The results demonstrate the practicality of enhancing bioremediation with vgb stably integrated into the chromosome, but also suggest that a minimal level of VHb expression is required for its beneficial effects to be seen.

Bacterial Proteins↗

PubMed2001

Inhibition of cholesteatomatous bone resorption with pamidronate disodium.

Bone destruction is known to be an important cause of complications in chronic cholesteatomatous otitis media. A strategy that blocks localized bone resorption may prevent the progression of the disease. The bisphosphonate drug pamidronate is known to inhibit bone resorption and has been used in the treatment of Paget's disease and osteoporosis. The aim of this study was to investigate the effect of pamidronate on the inhibition of bone resorption in cholesteatoma using a neonatal rat calvarial culture system. Radioactive calcium was subcutaneously injected into pregnant rats. Neonatal calvariae were harvested after i.p. injection of pamidronate disodium to neonatal rats and culture supernatants of cholesteatoma keratinocytes were then added to the calvarial culture media. Radioactive calcium release was measured using a beta-ray scintillation counter. The percentage of calcium release was significantly higher in cholesteatoma culture supernatant than in Dulbecco's modification of Eagle's medium. The percentage calcium release in cholesteatoma culture supernatant was significantly lower with the high dose of pamidronate than with the low dose. These results suggest that pamidronate can inhibit the bone resorption caused by cholesteatoma. This study suggests a possible application for pamidronate in the prevention of cholesteatomatous bone destruction.

Animals↗

PubMed2001

Hepatocellular carcinoma: correlation between vascular endothelial growth factor level and degree of enhancement by multiphase contrast-enhanced computed tomography.

RATIONALE AND OBJECTIVES: To determine whether vascular endothelial growth factor (VEGF) is a histopathological factor influencing contrast enhancement of hepatocellular carcinoma (HCC) on computed tomography (CT). METHODS: Twenty-two nodular HCCs underwent multiphase helical CT and surgery. Tumor size, histological grading of differentiation, and type of hepatitis were evaluated. Tumor attenuation was graded as hyperattenuated, isoattenuated, and hypoattenuated. Immunohistochemical staining with anti-VEGF antibody was performed and scored as weak, intermediate, or strong. Spearman's rank correlation test was used. RESULTS: Tumors ranged from 1.0 to 12.0 cm (mean 5.1 cm). The degree of enhancement during the hepatic arterial phase was significantly correlated with VEGF expression. Size was negatively correlated with VEGF expression and the degree of enhancement, but histological grade and type of hepatitis were not correlated with VEGF expression, tumor size, or degree of enhancement. CONCLUSIONS: In HCC, VEGF expression is correlated with the degree of contrast enhancement during arterial-phase CT.

Adult↗