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Biomedical subjects

H C Cho

Publications and source records attributed to H C Cho.

At least 19 recordsLinked to original sources
PubMed2001

Increased frequencies of glutathione S-transferase (GSTM1 and GSTT1) gene deletions in Korean patients with acquired aplastic anemia.

Patients with reduced ability to metabolize environmental carcinogens or toxins may be at risk of developing aplastic anemia. Glutathione S-transferase (GST) has been implicated in detoxifying mutagenic electrophilic compounds. This study asked whether the homozygous gene deletions of GSTM1 and GSTT1 affect the likelihood of developing aplastic anemia. The incidence of GSTM1 and GSTT1 gene deletions was significantly higher for aplastic anemia patients (odds ratio [OR]: 3.1, P =.01 and OR: 3.1, P =.004, respectively) than for healthy controls. Among the aplastic anemia patients, 17.5% (10:57) had chromosomal abnormalities at the time of diagnosis, and all aplastic anemia patients with chromosomal abnormalities showed GSTT1 gene deletions (P =.048). Individuals with GSTM1 and GSTT1 gene deletions may have greater susceptibility to aplastic anemia. It is possible that genetic instability or chromosomal damage due to abnormal detoxification of environmental toxins might have worked as an important pathophysiologic mechanism of aplastic anemia for patients with GSTT1 gene deletions.

Adolescent↗
PubMed2001

Removal of unburned carbon from coal fly ash using a pneumatic triboelectrostatic separator.

A pneumatic triboelectrostatic beneficiation system of fly ash was studied using a continuous, bench-scale electroseparator composed of two vertical electrode plates and an ejector-tribocharger. Tests were conducted to evaluate the charge density and the separation efficiency at various operating conditions. It was found that the higher charge densities were obtained at (1) the air flow rate of 1.75 m3/min. (2) the feed rate of less than 50 kg/h. and (3) the relative humidity of less than 30% with use of a stainless ejector tribocharger. With these optimum conditions, the clean ash of less than LOI 3% was recovered with a yield over 75% when operated at the diffuser slit gap of 4mm, the diffuser outlet velocity of 16.1-18.6 m/s, and the distance of 15 cm between diffuser slit and splitter. The optimum feed rate was found to be 740 kg/h per m2 of electrode surface area, which can be used as a scale-up factor of electroseparator.

Air Pollutants↗
PubMed2001

Ovarian sclerosing stromal tumors: gray scale and color Doppler sonographic findings.

Sclerosing stromal tumors are rare benign ovarian stromal tumors, which have distinctive clinical and pathologic features. The tumors occur predominantly in the second and third decades and are histologically characterized by the pseudolobular pattern of the cellular and hypocellular areas, marked vascularity, and heterogeneity of the cellular area. We analyzed 7 cases of sclerosing stromal tumors, which showed a typical sonographic appearance. On sonograms, sclerosing stromal tumors were solid and cystic and contained multiple round or cleftlike cysts. Ascites was rare. On transvaginal color Doppler sonograms, sclerosing stromal tumors were very hypervascular in the peripheral solid area and internal intercystic space and showed low-impedance flow. We conclude that sclerosing stromal tumors should be considered in young women with menstrual irregularity who have hypervascular solid and cystic adnexal masses.

Adult↗
PubMed2000

Two critical cysteine residues implicated in disulfide bond formation and proper folding of Kir2.1.

Inwardly rectifying potassium channels are important in cellular repolarization of many excitable tissues. Amino acid sequence alignment of different mammalian inward rectifier K(+) channels revealed two absolutely conserved cysteine residues in the putative extracellular face, suggesting a possible disulfide bond. Replacement of these cysteine residues in the Kir2.1 channel (i.e., C122 and C154) with either alanine or serine abolished current in Xenopus laevis oocytes although Western blotting established that the channels were fully expressed. The digestion pattern of channels treated with V8 protease combined with Western blotting under reducing and nonreducing conditions confirmed intrasubunit cross-linking of C122 and C154. Whole-cell and single channel current recordings of oocytes expressing tandem tetrameric constructs with one or two of the mutant subunits suggested that insertion of one mutant subunit is sufficient to eliminate channel function. Coexpression studies confirmed that the cysteine mutant channels eliminate wild-type Kir2.1 currents in a dominant-negative manner. Despite these results, sulfhydryl reduction did not alter the functional properties of Kir2.1 currents. Molecular modeling of Kir2.1 with the two cysteines cross-linked predicted that the extracellular loop between the first transmembrane domain and the pore helix contains a beta-hairpin structure. Distinct from the KcsA structure, the disulfide bond together with the beta-hairpin structure is expected to constrain and stabilize the P-loop and selectivity filter. Taken together, these results suggest that intramolecular disulfide bond exists between C122 and C154 of Kir2.1 channel and this cross-link might be required for proper channel folding.

Amino Acid Sequence↗
PubMed2000

Serologic heterogeneity of HLA-A24 correlates with allelic types in the Korean population.

HLA-A24 is the second most frequently expressed HLA-A type in Koreans (GF 22.8%). Four different serologic reaction patterns were observed in Korean A24 positive samples using a commercial serologic typing kit. To clarify the nature of serologic heterogeneity, thirteen A24 positive DNA samples representing the four different serologic reaction patterns were subjected to DNA sequencing analysis of the amplified HLA-A genes from each sample. Four A*24 alleles (A*2402101, A*2403, A*2408, and A*2421) were associated with the four unique serologic reaction patterns. During this study, a novel allele, A*2421, was characterized. The new sequence is similar to A*2402101, differing at codon 127 (AAA-->AAC; K-->N). By comparing putative amino acid sequences and serologic reaction patterns of A*24 allelic products identified in this study, several crucial sites for A24- and A9-specific antibody binding were predicted: 127K for A24 antibody binding, and 62E-65G and 166D-167G for A9 antibody binding. This information will be helpful for accurately assigning HLA-A24 types by serology and for predicting serologic types of new alleles.

Alleles↗
PubMed2000

Korean Nationwide Surveillance of Antimicrobial Resistance of Bacteria in 1998.

Antimicrobial resistance surveillance can provide information needed for empirical therapy of antimicrobial agents and for control of resistance. To determine the trend of antimicrobial resistance in Korea, in vitro susceptibility data in 1998 were collected from 25 hospitals participating to a program of Korean Nationwide Surveillance of Antimicrobial Resistance (KONSAR). The data were analyzed based upon hospital location and bed capacity. The results showed that cefoxitin-resistant E. coli and K. pneumoniae and 3rd-generation cephalosporin-resistant K. pneumoniae were prevalent, that 3rd-generation cephalosporin-resistant E. cloacae, S. marcesens and A. baumannii had increased, and ampicillin-resistant S. enterica were not rare. Oxacillin-resistant S. aureus, penicillin-non-susceptible pneumococci and beta-lactamase-producing H. influenzae were prevalent even smaller hospitals surveyed, and an increase of imipenem-resistant P. aeruginosa and vancomycin-resistant E. faecium is a new obvious threat. In general, resistance rates to some old antimicrobial agents, i.e., E. coli to ampicillin and S. aureus to oxacillin were high and did not vary greatly between the different levels of hospitals, while the rates to some of the newer ones, i.e., P. aeruginosa to imipenem, was quite variable and depended on the hospitals, probably reflecting difference in selective pressure.

Ampicillin↗
PubMed1998

Microtiter plate-format optode.

Microtiter plate-format optodes could be assembled by casting bulk-response membranes into the standard 96-well polypropylene-based plate or by screen printing them on an optically transparent substrate with 96-well pattern. The compositions of thick optode membranes, especially the ratios of poly(vinyl chloride) (PVC) to plasticizer [bis-(2-ethylhexyl) sebacate (DOS)], were carefully optimized to provide reproducible and rapid response. Adjusting the ratio of PVC to DOS by 1:6, bulk-response membranes containing neutral carrier (4-tert-butyl calix[4]arene tetraacetic acid tetraethyl ester for sodium-selective membrane or valinomycin for potassium-selective membrane) and lipophilic pH indicator (ETH 5294) could exhibit equilibrium response in 5 min. The practical utility of microtiter plate-format optodes has been examined by determining clinically relevant electrolytes in serum samples. It was demonstrated that microtiter plate-format optodes can provide high sample throughput (approximately 100 samples in less than 5 min), analytical performance comparable to that of a potentiometric clinical analyzer, and additional information on electrolytes using the same samples prepared for other colorimetric measurements.

Animals↗
PubMed1998

Anticardiolipin and anti-beta2-glycoprotein I antibodies in Behcet's disease.

To investigate prevalence of anticardiolipin antibodies (aCL) in patients with Behcet's disease (BD) and to determine whether they are related to anti-beta2-glycoprotein I antibodies (aGPI), we measured aCL and aGPI in 47 patients of BD and 14 patients of systemic lupus erythematosus (SLE). The levels of aCL and aGPI were determined by conventional enzyme immunoassay for both IgG and IgM classes. Twelve (25.5%) patients with BD were positive for IgG or IgM aCL and no patient was positive for aGPI. Eleven (78.6%) patients with SLE were also positive for aCL and among them, 8 (72.7%) patients were positive for aGPI. Positive IgG aCL patients with BD showed lower level of IgG aCL than those with SLE (15.7+/-7.3 vs 34.1+/-16.0 GPL, p<0.05). There was no relation between the presence of aCL in BD and either dinical activity or clinical features. In the patients with BD, aCL are found but it would not be associated with aGPI as they are in patients with SLE. In patients with BD, aCL seem to be authentic aCL unlike those in patients with SLE and may not be related with vascular complications in BD.

Adult↗
PubMed1998

Korean Nationwide Surveillance of Antimicrobial Resistance of bacteria in 1997.

Antimicrobial-resistant bacteria are known to be prevalent in tertiary-care hospitals in Korea. Twenty hospitals participated to this surveillance to determine the nationwide prevalence of resistance bacteria in 1997. Seven per cent and 26% of Escherichia coli and Klebsiella pneumoniae were resistant to 3rd-generation cephalosporin. Increased resistance rates, 19% of Acinetobacter baumannii to ampicillin/sulbactam, and 17% of Pseudomonas aeruginoa to imipenem, were noted. The resistance rate to fluoroquinolone rose to 24% in E. coli, 56% in A. baumannii and 42% in P. aeruginosa. Mean resistance rates were similar in all hospital groups: about 17% of P. aeruginosa to imipenem, 50% of Haemophilus influenzae to ampicillin, 70% of Staphylococcus aureus to methicillin, and 70% of pneumococci to penicillin. In conclusion, nosocomial pathogens and problem resistant organisms are prevalent in smaller hospitals too, indicating nosocomial spread is a significant cause of the increasing prevalence of resistant bacteria in Korea.

Bacterial Physiological Phenomena↗
PubMed1995

Reliability and validity of the cognitive impairment diagnosing instrument (CIDI) in the elderly.

The reliability and validity of the Cognitive Impairment Diagnosing Instrument (CIDI) were studied in 67 nursing home elderly subjects and 251 elderly psychiatric patients. Its possible highest score is 77 and covers 10 subscales: short-term memory, long-term memory, concentration/calculation, abstract thinking, judgement, memory registration, higher cortical functions, orientation in time, orientation in place and object naming. Test-retest correlations were between 0.827 and 0.990 for the subscale scores and 0.984 for the total score. Inter-tester kappas for each item ranged from 0.200 to 1.000 with a mean of 0.698. Concordance rates were between 50.0 and 100.0% with a mean of 87.2%. Cronbach's alphas for the items of the individual subscales ranged from 0.702 to 0.915. Inter-subscale and subscale-total correlations ranged from 0.503 to 0.820 with a mean of 0.684 and from 0.721 to 0.883, respectively. Cronbach's alpha of the subscales was 0.934. Sensitivity and specificity were 93.3% and 93.8% at the cut-off point of 57.0/57.5 for dementia. Subscale and total scores were significantly different between the demented and non-demented. The total CIDI score was significantly correlated with scores of the Blessed Dementia Rating Scale and the Korean version of the Mini-Mental State Examination.

Aged↗
PubMed1994

Reverse-SSO hybridization provides an accurate and simple HLA-DR typing--a comparative study with HLA-DR serologic typing.

The HLA-DR molecule is a polymorphic membrane glycoprotein and one of the key molecules causing allograft rejection and graft-versus-host disease in organ transplantation. Serologic typing using DR specific alloantisera has long been used, but several problems have limited its application. The purpose of this study was to establish an efficient reverse-SSO typing system that detects DRB1 and DRB3/B4/B5 alleles on a single membrane. A DR typing membrane was prepared by immobilizing 21 dT-tailed sequence specific oligonucleotides (SSOs) on a nylon membrane and was used in a hybridization assay with digoxigenin-labeled PCR-amplified target DNA. The positive signals were detected on X-ray film using chemiluminescence. A comparison study with serology using DNAs from 105 unrelated individuals demonstrated that the reverse-SSO typing system was superior to serologic typing in terms of accuracy (100% vs 90.5%), simplicity, range of application, rapidity, and cost of the test. These data indicate that the reverse-SSO typing system can replace serology as a routine DR test, and will be useful in time-restricted solid organ transplantation and in selection of an unrelated marrow donor prior to bone marrow transplantation.

Base Sequence↗
PubMed1989

Protection of dogs against death from experimental rabies by postexposure administration of rabies vaccine and hyperimmune globulin (human).

Two experiments on simulated postexposure treatment were carried out in dogs using human rabies immunoglobulin (RIGH) and human diploid cell vaccine for human use. In one experiment, when animals were challenged by injecting street virus into the masseter muscle and treated with a combination of RIGH and vaccine, 50% of the animals were protected from rabies. In the other trial, in which animals were challenged by injecting the virus into the femoral muscle, treatment with RIGH and vaccine protected all the animals against rabies. To our knowledge this is the highest rate of postexposure survival in animals reported to date. In addition, five out of eight (62.5%) dogs that received RIGH alone after the virus challenge were protected, while none of the animals receiving vaccine alone were protected from rabies. These trials suggest that animals can be protected from rabies by postexposure treatment. The route of exposure and timing of the administration of vaccine and hyperimmune serum would seem to be important.

Animals↗
PubMed1979

Measurement of antibodies to rabies virus by immunoelectron microscopy.

Immunoelectron microscopy (IEM) was used to measure rabies antibodies in 47 serum samples from vaccinees with results similar to those obtained by mouse neutralization test (MNT). The use of inactivated rabies virus for IEM eliminated the hazard associated with live virus used in the MNT.

Antibodies, Viral↗
PubMed1972

Antibody and immunoglobulin response to antirabies vaccination in man.

Serum neutralization antibody and immunoglobulin responses in 30 individuals were studied in paired serum samples which had been obtained before and 2 to 3 weeks after the administration of a recall dose of rabies tissue culture vaccine. The immune reaction consisted of a predominantly immunoglobulin G (IgG) antibody response. Also, a significant increase in neutralizing antibody titers was observed, but without a consistently correlated change of the IgG levels in the individual serum samples. The radial immunodiffusion test appears to contain the elements necessary for the development of a routine test to determine rabies antibody in single serum samples.

Animals↗
PubMed1970

Radial immunodiffusion of chicken serum proteins. I. Standardization of optimal test procedures.

Optimal conditions were determined for the quantitaion of chicken serum albumin, conalbumin, IgG and IgM by the radial immunodiffusion test. The best diluent was 0.15 M phosphate buffered saline, pH 7.2. The optimal concentration of the rabbit antiserum in the agar plate was inversely related to the molecular weight of the protein under study. The incubation time required for maximum ring formation was directly related to the molecular weight of the proteins under study. The reproducibility of the tests was evaluated using stored and fresh antiserum-agar plates.

Animals↗