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Biomedical subjects

J W Choi

Publications and source records attributed to J W Choi.

At least 19 recordsLinked to original sources
PubMed2007

The effects of container materials and buffer additives on decreasing the iodide concentration in a disposal vault for spent nuclear fuel.

To retard the migration of iodine released from a spent fuel after the break of a container, the reducing effects on the concentration of the iodide by container corrosion products and some buffer additives were examined in a solution with bentonite. Iron and copper, and their corrosion products scarcely reduced the iodide concentration. And kaolinite, chalcopyrite, pyrite, copper ore and galena, known as having a sorption property for iodine, did not noticeably sorb the iodide. However, palm active carbon, silver metal and Ag2O lowered the iodide concentration. Especially, Ag2O put into a disposal container would effectively hinder the migration of iodine to the outside of a disposal vault without a great loss if the pore size of the compacted buffer layer is maintained below 1 mu m.

Buffers↗
PubMed2006

Electrochemical detection of pathogen infection using cell chip.

The immobilized cell using self-assembled synthetic oligopeptide was applied to the electrochemical detection of pathogen infection. Thin films based on cysteine-terminated synthetic oligopeptides were fabricated for the immobilization of HeLa cell on gold (Au) substrate. Layer formation and immobilization of the cell were investigated with surface plasmon resonance (SPR) and electrochemical impedance spectroscopy (EIS). Experimental results showed that the thin film of cysteine-terminated synthetic oligopeptide was successfully fabricated and it could be applied for the immobilization of HeLa cells. The adhered living cell was exposed to E. coli O157:H7, which induced the change of SPR angle and electrochemical impedance signal. The proposed cell immobilization method using self-assembly technique can be applied to construct the cell microarray for on-site pathogen monitoring.

Carcinoma↗
PubMed2006

Comparison of the amount of nuclides released from the spent fuel in contact with and without a compacted bentonite block.

A spent LWR fuel specimen between Ca-bentonite blocks was leached in a simulated bentonite-saturated granitic water (SBGW) for 165 days and its results were compared with those of a specimen leached without a bentonite block. The amounts of Cs, Sb, Sr, Eu, Am, U and Pu released from a 4.3 mm thickness of a fuel pellet with a 50,400 MWD/MTU burn-up in the SBGW without a bentonite block were 2.2, 0.25, 0.15, 0.02, 0.01, 0.01 and approximately 5 x 10(-4)% of their inventories, respectively. However, the amounts of nuclides released from the specimen between the 1.4 Mg/m(3) bentonite blocks were decreased by three times at least. Moreover, the concentrations of the nuclides in the leachate were very low because most of them were retained in the bentonite blocks.

Bentonite↗
PubMed2006

Biological responses of anodized titanium implants under different current voltages.

The oxide layer of a titanium surface is very stable, and seems to result in excellent biocompatibility and successful osseointegration. The purpose of this study was to investigate the effects of high anodic oxidation voltages on the surface characteristics of titanium implants and the biologic response of rabbit tibiae. Bone tissue responses were evaluated by removal torque tests and histomorphometric analysis. Screw-shaped implants with microthreads were made of commercially pure titanium (Grade II). We prepared anodized implants under 300 V (group I), 400 V (group II), 500 V (group III) and 550 V (group IV). The surface characteristics of specimens were inspected according to three categories: surface morphology, surface roughness and oxide layer thickness. The screw-shaped implants were installed in rabbit tibiae. The removal torque values were measured and histomorphometric analysis was done after 1- and 3-month healing periods. Data indicate that as anodic oxidation voltage increased above 300 V, oxide layer thickness increased rapidly and pore size also increased. The roughness values of the implants increased with voltage up to 500 V, but decreased at 550 V. In the removal torque test, group III showed higher values than groups I and II at a statistically significant level (P < 0.05) after a 1-month healing period. In histomorphometric analysis, groups III and IV, after a 3-month healing period, showed greater bone to implant contact ratios for the total implant surface than did group I (P < 0.05).

Animals↗
PubMed2006

Peripheral T-cell lymphoma in the neck: CT findings of lymph node involvement.

OBJECTIVE: To describe the CT findings of lymph nodes of the neck involved in peripheral T-cell lymphomas (PTCL). MATERIALS AND METHODS: Twenty-seven patients with pathologically proved PTCL with involvement of the lymph nodes of the neck were enrolled in this study. We retrospectively evaluated the lymph nodes on CT images with special attention to nodal necrosis, the margin, and enhancement patterns. RESULTS: In the 27 patients studied, nodal necrosis and ill-defined margin were seen in 11 (41%) and 19 (70%), respectively. Heterogeneous enhancement of enlarged lymph nodes was noted on CT images in 19 (70%) of 27 patients. Homogeneous enhancement without ill-defined margin and/or nodal necrosis was only seen in 6 of 27 patients (22%). CONCLUSION: Necrosis, an ill-defined margin, and heterogeneous enhancement of enlarged lymph nodes in the neck are relatively common CT features of PTCL. For patients with cervical lymph node enlargement, the presence of these findings may suggest high-grade non-Hodgkin's lymphoma, including PTCL.

Female↗
PubMed2005

Relationships between tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) and hematopoietic activity in healthy adults.

To investigate the relationship between hematopoiesis and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), we measured soluble TRAIL concentrations, reticulocytes, hemograms, and anthropometric variables in 156 healthy subjects. Serum TRAIL concentrations were analyzed by an enzyme immunoassay. Serum ferritin, thyroid hormone, total cholesterol, creatinine, and blood glucose levels were determined. There were no significant differences in blood cell counts and biochemical parameters between the subjects with TRAIL less than 63.5 pg/ml and TRAIL at least 63.5 pg/ml, nor between those with TRAIL at most 47.5 pg/ml (20th percentile) and TRAIL > or =80.9 pg/ml (80th percentile). However, hemoglobin, mean corpuscular hemoglobin (MCH), and MCH concentration (MCHC) averaged 15.6+/-0.8 g/dl, 31.9+/-1.1 pg, and 34.5+/-0.9 g/dl in the subjects with TRAIL at most 47.5 pg/ml, which were significantly above the values in those with TRAIL at least 80.9 pg/ml (14.7+/-0.9 g/dl, 30.4+/-1.3 pg, and 33.2+/-1.2 g/dl, P<0.05, respectively). Serum TRAIL levels were significantly higher in the subjects with decreased MCH than in those with elevated MCH. Soluble TRAIL concentrations were significantly correlated with hemoglobin (r=-0.25, P<0.05), MCH (r=-0.32, P<0.05), and MCHC (r=-0.29, P<0.05), but not correlated with leukocyte differentials and platelet counts. In conclusion, soluble TRAIL does not seem to influence leukocyte and platelet production but has an important relationship to erythropoiesis in healthy adults.

Adult↗
PubMed2004

Optimization of submerged culture condition for the production of mycelial biomass and exopolysaccharides by Agrocybe cylindracea.

The optimization of submerged culture conditions and nutritional requirements was studied for the production of exopolysaccharide (EPS) from Agrocybe cylindracea ASI-9002 using the statistically based experimental design in a shake flask culture. Both maximum mycelial biomass and EPS were observed at 25 degrees C. The optimal initial pH for the production of mycelial biomass and EPS were found to be pH 4.0 and pH 6.0, respectively. Subsequently, optimum concentration of each medium component was determined using the orthogonal matrix method. The optimal combination of the media constituents for mycelial growth was as follows: maltose 80 g/l, Martone A-1 6 g/l, MgSO4 x 7H2O 1.4 g/l, and CaCl2 1.1 g/l; for EPS production: maltose 60 g/l, Martone A-1 6 g/l, MgSO4 x 7H2O 0.9 g/l, and CaCl2 1.1 g/l. Under the optimal culture condition, the maximum EPS concentration achieved in a 5-l stirred-tank bioreactor indicated 3.0 g/l, which is about three times higher than that at the basal medium.

Agaricales↗
PubMed2004

Morphological and rheological properties of the three different species of basidiomycetes Phellinus in submerged cultures.

AIMS: The objective of this work was to investigate the morphological and rheological properties in submerged culture of the three different basidiomycetes Phellinus (P. baumii, P. gilvus and P. linteus) that produce pharmacologically important exopolysaccharides (EPS). METHODS AND RESULTS: In flask cultures, pH proved to be a critical factor affecting mycelial growth, morphological change and EPS production. The macroscopic morphologies observed under different pHs in flask cultures were also comparable: i.e. starfish-like pellets with a lesser extent of free mycelium appeared in P. baumii, whereas smooth pellets with higher amounts of free mycelium were observed in P. gilvus and P. linteus. The pelleted fermentations were further characterized in a 5-l stirred-tank fermenter by image analysis with respect to mean diameter, core area and pellet circularity. Phellinus baumii showed the largest pellet size (5.2 mm in diameter), whereas P. linteus had extremely small and spherical pellets. The culture broth of P. baumii and P. gilvus yielded extremely high apparent viscosities, ranging from 5 to 7 Pa s. CONCLUSIONS: Three important species of Phellinus showed significantly different morphological and rheological properties. The morphological variation of the three Phellinus species was closely linked to EPS productivity and the apparent viscosity of the whole broth. SIGNIFICANCE AND IMPACT OF THE STUDY: The morphological change in the three species of Phellinus was a good indicator for identifying cell activity for EPS production. Our finding may be beneficial for further optimization of other fungal fermentation processes for large-scale production of EPS.

Basidiomycota↗
PubMed2003

Molecular basis and characteristics of KATP channel in human corporal smooth muscle cells.

Relaxation of the corpus cavernosum smooth muscle is an absolute prerequisite for penile erection. Potassium channels play a role in the physiologic regulation of corporal smooth muscle tone. In spite of the physiological importance of K(ATP) channel in the modulation of corporal smooth muscle tone, there is a shortage of information available about the K(ATP) channel subtype(s) present in the corporal smooth muscle. The purpose of this study was to investigate the subunit type of K(ATP) channel, that is, the combinations of the Kir subunit and the SUR subunit in the human corporal smooth muscle and determine whether the electrophysiological kinetics and pharmacological properties of K(ATP) channels meet the subunit characteristics of the ion channel. We used cultured human corporal smooth muscle cells. To determine the presence of Kir and SURs subunits, RT-PCR was performed using Kir6.1, Kir6.2, SUR1, SUR2A, and SUR2B gene-specific primers. For electrophysiological recordings, the whole-cell, inside-out, and cell-attached configurations of the patch-clamp technique were used. We observed transcripts for Kir6.1, Kir6.2, and SUR2B in mRNA isolated from smooth muscle cells of cultured human corpus carvernosum. We recorded the unitary K(ATP) channel under the condition of intracellular and extracellular 140 mM [K(+)], and the slope conductance of the channel was 42.0+/-2.6 pS which is an intermediate conductance between that of either Kir6.1 or Kir6.2. The pinacidil (10 microM) increased the magnitude of the outward K(+) current (214.6+/-89.2%, n=12, < or = 0.05), which was blocked by the subsequent addition of the specific K(ATP) channel subtype selective blocker, glibenclamide (10 microM). The SIN-1(200 microM) induced increases in whole-cell outward K(+) currents (126.0+/-1.4%, n=4). The increased currents by SIN-1 were inhibited by glibenclamide (10 microM). We are the first to show that K(ATP) channel in human corporal smooth muscle is composed of Kir6.1-Kir6.2 construct expressed with SUR2B by RT-PCR. These findings, taken together with the electrophysiological results, suggest that K(ATP) channel in corporal smooth muscle cells is composed of heteromultimers of Kir6.1 and Kir6.2 with the ratio of 3 : 1 or 4 : 0 and SUR2B.

ATP-Binding Cassette Transporters↗
PubMed2003

Production and molecular characteristics of four groups of exopolysaccharides from submerged culture of Phellinus gilvus.

AIMS: The objective of the present study was to determine the optimal culture conditions for the production of four groups of exopolysaccharides (EPSs) in Phellinus gilvus by submerged culture and to investigate their molecular properties by multi-angle laser-light scattering (MALLS) analysis. METHODS AND RESULTS: The optimal temperature and initial pH for the production of both mycelial biomass and EPSs in P. gilvus by submerged flask cultures were found to be 30 degrees C and pH 9.0, respectively. Glucose and corn steep powder were the most suitable carbon and nitrogen source for both mycelial biomass and EPS production. Optimal medium composition was determined to be glucose 30 g l-1, corn steep powder 5 g l-1, MgSO4 1.23 g l-1, KH2PO4 0.68 g l-1, and K2HPO4 0.87 g l-1. Four groups of EPSs (Fr-I, II, III, and IV) were obtained from the culture filtrates by gel filtration chromatography on Sepharose CL-4B and characterized by size exclusion chromatography (SEC) coupled with MALLS. The weight average molar mass (Mw) of Fr-I, Fr-II, Fr-III and Fr-IV were determined to be 8.628 x 106 (+/-129 420), 1.045 x 106 (+/-19 855), 61.09 x 104 (+/-1244), and 33.55 x 104 (+/-134) g mol-1, respectively. CONCLUSIONS: Under optimal culture conditions, the maximum EPS production in a 5-l stirred fermenter indicated 5.3 g l-1 after 11 days of fermentation. The SEC/MALLS analysis revealed that Fr-I, which has extremely high molecular weight, was presumably an aggregate of complex polysaccharides forming a compact globular shape; whereas Fr-II was nearly spherical, Fr-III and Fr-IV were rod-like chains in an aqueous solution. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report on the production of high amounts of EPSs from liquid-culture of the basidiomycete, P. gilvus. The SEC/MALLS approach used in this study could be useful in providing greater insight into the characterization of the mushroom polysaccharides without carrying out elaborate fractionation procedures prior to analysis.

Amino Acids↗
PubMed2003

Expression of an artificial polypeptide with a repeated tripeptide glutamyl-tryptophanyl-lysine in Saccharomyces cerevisiae.

AIMS: Artificial genes, which encode 48 or 64 repeats of a tripeptide, glutamyl-tryptophanyl-lysine have been cloned to the yeast expression vector pAM82 containing the PHO5 promoter and expressed in Saccharomyces cerevisiae AH22. METHODS AND RESULTS: When the yeast cells harbouring recombinant plasmids pALTG6-2 and pALTG4-4 were derepressed in Burkholder minimal medium (Toh-e, A., Ueda, Y., Kakimoto, S.I. and Oshima, Y. (1973) Journal of Bacteriology113, 727-738) containing low phosphate (0.03 g l-1 KH2PO4 and 1.5 g l-1 KCl), the expression was the highest after 24 h induction and the artificial polypeptides were synthesized to about 10% (pALTG6-2) and 14% (pALTG4-4) of the total cell protein. CONCLUSIONS: The artificial polypeptides produced in yeast were made to react with the rabbit antiserum against the polypeptide purified from Escherichia coli and found only in the pellet fraction of cell lysates, indicating the formation of inclusion body. Artificial polypeptide consisting of Glu-Trp-Lys may be useful as partial supplement in food and feeds. SIGNIFICANCE AND IMPACT OF THE STUDY: The production of single cell enriched with homopolymers of an essential amino acid in yeast might be an important tool of supplementing cereal diets and feed grain rations and could be used as means for improvement of the amino acid profile of single cell protein and production of pharmaceutical peptides.

Amino Acids, Essential↗
PubMed2003

Effect of aeration and agitation on the production of mycelial biomass and exopolysaccharides in an enthomopathogenic fungus Paecilomyces sinclairii.

AIMS: The objective of the present study was to investigate the influence of aeration rate and agitation intensity on the production of mycelial biomass and exopolysaccharide (EPS) in Paecilomyces sinclairii. METHODS AND RESULTS: The P. sinclairii was cultivated under various aeration and agitation conditions in a 5 l stirred-tank bioreactor. The highest mycelial biomass (30.5 g l-1) and EPS production (11.5 g l-1) were obtained at a high aeration rate (3.5 v.v.m.) and at a high agitation speed (250 rev min-1). The apparent viscosities (6000-8000 cP) of fermentation broth increased rapidly towards the end of fermentations at high aeration and agitation conditions. CONCLUSIONS: The high level of dissolved oxygen achieved at a high aeration rate (3.5 v.v.m.) associated with higher hyphal density eventually resulted in enhanced EPS production. Agitation intensity was also proved to be a critical factor influencing on both the mycelial biomass and EPS production: high agitation speeds up to 250 rev min-1 were preferred to the yields of biomass and EPS production. SIGNIFICANCE AND IMPACT OF THE STUDY: The critical effects of aeration and agitation in the culture process of P. sinclairii were found, which is widely applicable to other kinds of basidiomycetes or ascomycetes in their submerged culture processes.

Aerobiosis↗
PubMed2003

Association between blood lead concentrations and body iron status in children.

Blood lead concentrations and body iron status were investigated in 279 children. Blood lead concentrations showed no increase during iron depletion phase (stage I) but markedly increased from the phase of iron deficient erythropoiesis (stage II). Increased blood lead concentrations in anaemic subjects significantly decreased after iron supplementation.

Adolescent↗
PubMed2003

Antimicrobial performance of alkaline ionic fluid (GC-100X) and its ability to remove Escherichia coli O157:H7 from the surface of tomatoes.

An efficacy test of GC-100X, a noncorrosive alkaline ionic fluid (pH 12) composed of free radicals and supplemented with xylitol, was carried out against six major foodborne pathogens-Staphylococcus aureus FRI 913, Salmonella enterica serovar Enteritidis ATCC 13076, S. enterica serovar Typhimurium DT104 Korean isolate, Vibrio parahaemolyticus ATCC 17803, Escherichia coli O157:H7 ATCC 43894, and Pseudomonas aeruginosa KCTC 1637-at three different temperatures (4, 25, and 36 degrees C) with or without organic load (2% yeast extract). Results revealed a more than 4-log10 (CFU/ml) reduction (1.0 x 10(4) CFU/ml reduction) against all pathogens reacted at 37 degrees C for 3 h in the absence of organic material. GC-100X solution diluted with an equal volume of distilled or standard hard water (300 ppm CaCO3) showed effective bactericidal activity, particularly against gram-negative bacteria. Washing efficacy of GC-100X solution was compared against E. coli O157:H7 on cherry tomato surfaces with those of a commercially used detergent and chlorine water (100 ppm). Viable cell counts of E. coli O157:H7 that had penetrated to the cores of tomatoes after sanitizing treatment revealed that GC-100X stock and its 5% diluted solutions had similar washing effects to 100-ppm chlorine water and were more effective than the other kitchen detergent. These results indicate that GC-100X has good bactericidal and sanitizing activities and is useful as a new sanitizer for food safety and kitchen hygiene.

Chlorine↗
PubMed2003

Does Helicobacter pylori infection relate to iron deficiency anaemia in prepubescent children under 12 years of age?

AIM: To investigate the association between Helicobacter pylori (H. pylori) infection and iron deficiency anaemia (IDA). METHODS: Haemoglobin levels, iron parameters and serum IgG antibodies to H. pylori were measured in 693 children aged 9 to 12 y. RESULTS: No significant differences in the seroprevalence of H. pylori infection and antibody titres to H. pylori were found between the IDA group and the non-anaemic controls. CONCLUSION: H. pylori infection does not seem to contribute to iron deficiency in prepubescent children.

Anemia, Iron-Deficiency↗
PubMed2002

Reliable and reproducible LightCycler qPCR for HIV-1 DNA 2-LTR circles.

Highly active anti-retroviral therapy (HAART) has reduced the plasma load of HIV-1 to undetectable levels. It has however failed to eliminate the virus from other body compartments. Current methods for monitoring persistent viral replication in HIV-1+ patients require a large amount of blood and/or repeated tissue biopsies. Furthermore, some of the viral reservoirs, such as brain and eye, are inaccessible for sampling. The detection of episomal HIV-1 DNA 2-LTR circles in CD4+ cells is indicative of recent, acute infection events. This paper describes a reliable and reproducible LightCycler-based assay for the quantitative measurement of HIV-1 DNA 2-LTR circles in human peripheral blood mononuclear (PBMN) cells. It details the modifications to the DNA extraction procedure and to the LightCycler PCR procedure that were required to achieve this. This new surrogate marker of persistent viral replication can now be reliably, reproducibly and robustly used to study the clinical progress of large numbers of patients whose plasma HIV-1 RNA has been reduced to undetectable levels by anti-retroviral drugs.

DNA Restriction Enzymes↗
PubMed2002

LightCycler qPCR optimisation for low copy number target DNA.

The LightCycler is a rapid air-heated thermal cycler which incorporates a fluorimeter for the detection and quantification of Polymerase Chain Reaction (PCR) amplified products. It provides real-time cycle-by-cycle analysis of product generation. Amplification occurs in glass capillary tubes. The products are detected using a fluorescent double stranded DNA binding dye or fluorescent probes. However, conditions that work well in conventional PCR reactions do not readily translate to the LightCycler. Whilst using this new technology to study an infectious pathogen in human tissue samples, several parameters were identified which can have an adverse effect on the reliable and reproducible quantification of low copy number target DNA. They included abstraction of PCR reagents on glass, primer-dimer formation, non-specific product generation, and a failure to amplify low copy number target when it is present in a high background of human chromosomal DNA. For each problem identified, several solutions are described. Novel approaches are also described to ensure that amplification of target DNA and of the quantification standards occurs with the same efficiency. With appropriate changes to the protocols currently in use, LightCycler quantitative Polymerase Chain Reaction (LC-qPCR) can be used to achieve a level of accuracy that exceeds that of an enzyme immunoassay. The LC-qPCR optimisation strategies described are of particular relevance when applying this technology to the study of pathogens in tissue samples. The technique offers the enormous potential for reliable and reproducible quantitative PCR of low copy number target DNA.

DNA Primers↗