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Biomedical subjects

J W Choi

Publications and source records attributed to J W Choi.

At least 55 records · Page 3Linked to original sources
PubMed2001

Change in erythropoiesis with gestational age during pregnancy.

To investigate the changes in erythropoiesis during pregnancy, 342 pregnant and postpartum women were examined for reticulocyte subpopulations, reticulocyte maturity index (RMI), and serum transferrin receptor (sTfR) levels. The reticulocyte subpopulations were analyzed by flow cytometry, and the sTfR concentration was measured by an immunoenzymometric method. There were no significant differences in the values of reticulocyte subpopulations, RMI, and sTfR between first trimester and non-pregnant women. However, the RMI and sTfR concentration increased gradually from the second trimester of pregnancy, during which time values were twofold higher than those in the first trimester, and peaked in the third trimester. Then the RMI and sTfR values decreased abruptly 1-4 weeks postpartum and finally dropped to the levels of non-pregnant women 5 weeks after delivery. The maternal sTfR concentration correlated significantly with the corrected reticulocyte count (r = 0.52, P < 0.01), RMI (r = 0.67, P < 0.01), and high fluorescence reticulocytes (HFR) (r = 0.62, P < 0.01); however, the serum ferritin level correlated poorly with the reticulocyte subpopulations during pregnancy. In conclusion, erythropoiesis increases with gestational age during pregnancy and returns to normal 5 weeks after delivery. Measurement of sTfR in combination with RMI may improve the assessment of erythropoietic activity during pregnancy.

Adult↗
PubMed2001

The usefulness of serum transferrin receptor and ferritin for assessing anemia in rheumatoid arthritis: comparison with bone marrow iron study.

OBJECTIVES: This study was aimed at investigating the usefulness of serum transferrin receptor (sTfR) and ferritin in anemic patients with rheumatoid arthritis (RA) compared with bone marrow storage iron and other tests for anemia. METHODS: Fifty-five anemic RA patients underwent anemia study. Bone marrow iron stain was performed in 18 patients. sTfR and serum ferritin levels were compared with bone marrow iron stores. RESULTS: (1) Mean sTfR concentration was 2.63+/-1.91 mg/L, (2) sTfR correlated with most indicators of anemia, (3) sTfR showed no correlation with CRP and ESR, whereas ferritin did, and (4) sTfR was higher in the "iron depleted" subgroup than in the "iron nondepleted" subgroup in bone marrow study. CONCLUSION: The measurement of sTfR and ferritin is useful in finding the cause of anemia in RA and is a possible substitute for invasive bone marrow iron study.

Anemia, Iron-Deficiency↗
PubMed2001

Y-chromosome multiplexes and their potential for the DNA profiling of Koreans.

We have developed four multiplex genotyping systems (GeneKin Y-STR multiplexes) using silver staining with allelic ladders for ten Y-chromosome STR markers (DYS19, DYS385, DYS388, DYS389I/II, DYS390, DYS391, DYS392, DYS393 and DXYS156Y), with a view towards the application of rapid and simple genotyping assay methods for DNA profiling. The GeneKin Y-STR multiplexes developed have followed the published nomenclature and ISFG guidelines for STR analysis. Allele and haplotype frequencies at these Y-STRs loci were analysed by PCR amplification using the GeneKin Y-STR multiplexes, followed by denaturing polyacrylamide gel electrophoresis in 316 unrelated males in the Korean population. A total of 295 different haplotypes were found, 279 of them being unique. Gene diversity ranged from 0.4026 at DYS391 to 0.9606 at DYS385. The haplotype diversity value (which is the same as the discrimination index) calculated from all ten loci combined was 0.9995, which is informative. Our results revealed that a set of ten Y-STRs can discriminate between most of the male individuals in the Korean population (discrimination capacity: 93.35%). The Y-STR multiplexes thus provide useful information for forensic analysis and paternity tests and can also be of great benefit for providing information not normally available from autosomal DNA systems.

Alleles↗
PubMed2001

Antisense and sense expression of cDNA coding for CYP73A15, a class II cinnamate 4-hydroxylase, leads to a delayed and reduced production of lignin in tobacco.

A number of plant species contain the class II of genes encoding the cytochrome P450, CYP73, the cognate protein of which cinnamic acid 4-hydroxylase, is the second enzyme of the phenylpropanoid pathway. In order to begin to determine possible functionality, tobacco has been transformed with a truncated French bean class II cinnamate hydroxylase (CYP73A15) in the sense and antisense orientations. Signals for C4H protein could be detected in vascular tissue from wild-type plants using heterologous probes. The transformed plants showed a normal phenotype, even though detectable C4H protein was much reduced in tissue prints. Young propagated transformants displayed a range of reduced C4H activities, as well as either reduced or no phloroglucinol-stainable lignin. However, all mature tobacco plants showed the accumulation of lignin, even though its deposition was apparently delayed. This was not due to induction of tyrosine ammonia-lyase activity, which was not detected, but instead it is presumed due to sufficient C4H residual activity. Analysis of the lignin content of the plants showed reductions of up to 30% with a slightly reduced syringyl to guaiacyl ratio as compared to wild type. This reduction level was favourable in comparison with some other targets in the lignification pathway that have been manipulated including that of class I cinnamate 4-hydroxylase. It is proposed that the class II cinnamate 4-hydroxylase might also function in lignification in a number of species including French bean and tobacco, based on these data.

Cytochrome P-450 Enzyme System↗
PubMed2001

Chlorinated persistent organic pollutants in black-tailed gulls (Larus crassirostris) from Hokkaido, Japan.

Concentrations and patterns of several chlorinated persistent organic pollutants (POPs) including polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs) and biphenyls (PCBs) and DDTs, HCHs, CHLs and HCB were determined in black-tailed gulls (Larus crassirostris) from breeding grounds in Hokkaido, Japan. Subcutaneous fat of five adult gulls was analyzed, which had different concentrations of target compounds, whereas gull eggs contained similar concentrations of target compounds. Similar congener profiles were found between adult gulls and eggs. The concentrations of non-ortho PCBs varied from 3.4 to 13.5 ng/g lipid weight (lw) in the fat of black-tailed gulls and from 2.4 to 7.4 ng/g lw in their eggs. 2,3,7,8-PCDD/Fs occurred at relatively lower concentrations than non-ortho PCB congeners in both adult gulls and eggs. The total TEQs (toxic equivalents, PCDD/Fs+ non-ortho PCB) ranged from 0.26 to 1.0 ng/g lw in adult gulls and ranged from 0.19 to 0.58 ng/g lw in eggs.

Adipose Tissue↗
PubMed2001

An on-chip magnetic bead separator using spiral electromagnets with semi-encapsulated permalloy.

A new planar bio-magnetic bead separator on a glass chip has been designed, fabricated and tested. The separator is composed of micromachined semi-encapsulated spiral electromagnets and fluid channels, which have been separately fabricated and then bonded. The device was tested with super-paramagnetic beads of mean diameter 1 microm which were suspended in a buffered solution. When a DC current of 300 mA was applied to the inductor, the bio-magnetic beads were successfully separated on the electromagnets, showing a functional capability as a magnetic bead separator. To evaluate separation rate and capability, the inductance measurement method has been introduced and the inductance variation according to the separation rate has been characterized. Using this separator, cells or cell fragments and magnetic beads bonded with protein or enzyme suspended in bio-buffer solutions can be successfully separated from their suspensions, envisaging a filterless bio-separator.

Biological Factors↗
PubMed2001

Color image detection by biomolecular photoreceptor using bacteriorhodopsin-based complex LB films.

A biomolecular photoreceptor consisting of bacteriorhodopsin (bR)-based complex Langmuir-Blodgett (LB) films was developed for color image detection. By mimicking the functions of the pigments in retina of human visual system, biomolecules with photoelectric conversion function were chosen and used as constituents for an artificial photoreceptor. bR and flavin were deposited onto the patterned (9-pixelized) ITO glass by LB technique. A 9-pixel biomolecular photoreceptor was fabricated with a sandwich-type structure of ITO/LB films/electrolyte gel/Pt. Since each functional molecule shows its own response characteristic according to the light illumination in the visible region, the simplified knowledge-based algorithm for interpretation of the incident light wavelength (color) was proposed based on the basic rule describing the relationship between the photoelectric response characteristics and the incident light wavelength. When simple color images were projected onto the photoreceptor, the primary colors in visible light region, red, green, and blue were clearly recognized, and the projected color images were fairly well reproduced onto the color monitor by the proposed photoreceptor with the knowledge-based algorithm. It is concluded that the proposed device has a capability of recognizing the color images and can be used as a model system to simulate the information processing function of the human visual system.

Algorithms↗
PubMed2001

Optical organophosphorus biosensor consisting of acetylcholinesterase/viologen hetero Langmuir-Blodgett film.

The fiber-optic biosensor consisting of an acetylcholinesterase (AChE)-immobilized Langmuir-Blodgett (LB) film was developed to detect organophosphorus compounds in contaminated water. The sensing scheme was based on the decrease of yellow product, o-nitrophenol, from a colorless substrate, o-nitrophenyl acetate, due to the inhibition by organophosphorus compounds on AChE. Absorbance change of the product as the output of enzyme reaction was detected and the light was guided through the optical fibers. The enzyme portion of the sensor system was fabricated by the LB technique for formation of the enzyme film. AChE-immobilized LB film was formed by adsorbing the enzyme molecules onto a viologen monolayer using the electrostatic force. The proposed kinetics for irreversible inhibition of organophosphorus compounds on AChE agreed well with the experimental data. The surface topography of AChE-immobilized LB film was investigated by atomic force microscope (AFM). The immobilized AChE had the maximum activity at pH 7. The proposed biosensor could successfully detect the organophosphorus compounds up to 2 ppm and the response time to steady signal of the sensor was about 10 min.

Acetylcholinesterase↗
PubMed2001

Rectified photocurrent of molecular photodiode consisting of cytochrome c/GFP hetero thin films.

Photoinduced electron transfer in the molecular electronic device consisting of protein-adsorbed hetero Langmuir-Blodgett (LB) film was investigated. Three kinds of functional molecules, cytochrome c, viologen, and green fluorescent protein (GFP) were used as an electron acceptor, a mediator, and a sensitizer, respectively. The hetero-LB film was fabricated by subsequently depositing cytochrome c and viologen onto the pretreated ITO or quartz glass. GFP adsorbed hetero-LB films were prepared by soaking the hetero-LB films into the buffer solution containing GFP. The MIM (metal/insulator/metal) structured molecular device was constructed by depositing aluminum onto the surface of the GFP-adsorbed hetero LB films. Due to the excitation by irradiation with a 460 nm monochromic light source, the photoinduced unidirectional flow of electrons in the MIM device could be achieved and was detected as photocurrents. The photoswitching function was achieved and the rectifying characteristic was observed in the molecular device. Based on the measurement of transient photocurrent of molecular device, the unidirectional flow of electrons was verified.

Biosensing Techniques↗
PubMed2001

Visual information processing using bacteriorhodopsin-based complex LB films.

Image extraction and visual information processing using bacteriorhodopsin (bR)-based bioelectronic devices is presented. Image extraction was achieved using a photoreceptor consisting of bR and spiropyran films. The undesired signals from the photoreceptor were automatically eliminated from the whole signal by spiropyran films acting as an optical noise filter that increases the target signal to an undesired signal ratio. For the information processing, the photoreceptor consisting of bR and lipid films deposited with different configurations was used and the target signals were processed to achieve the pattern recognition. The pattern recognition was based on not only the response variability of bacteriorhodopsin, induced by different film configurations, but also on the initial learning process. The input patterns were predicted by simple calculation with the known signals through the initial learning process.

Bacteriorhodopsins↗
PubMed2001

Resource utilization and clinical outcomes of coronary stenting: a comparison of intravascular ultrasound and angiographical guided stent implantation.

BACKGROUND: Intravascular ultrasound (IVUS) guided stent implantation studies have demonstrated that inadequate stent implantation can occur despite achieving an optimal angiographic result. Furthermore, IVUS-guided stent implantation has been shown to improve lesional acute gain. However, it is unknown whether the use of IVUS guidance during stent implantation is associated with improved acute and long-term clinical outcomes. Moreover, the additional procedural cost and time incurred with the use of IVUS-directed stent implantation has not been evaluated. Thus the purpose of this study was to determine whether IVUS-guided stent implantation is associated with improved clinical outcomes compared with angiographically guided stent implantation and to evaluate the difference in resource utilization between these respective stent deployment strategies. METHODS: Data were collected on 278 consecutive patients in whom 455 stents were deployed in native coronary arteries. High-pressure (> or = 12 atm) balloon inflations were performed until an optimal angiographic result was obtained. In the angiographically guided group, no IVUS imaging was performed. In the IVUS-guided group, IVUS imaging and additional interventions were performed attempting to achieve full apposition, absence of edge tear, and acute gain (lesion lumen area: distal reference lumen area) > or = 0.8 in subsequent IVUS imaging. Total procedure time, fluoroscopy time, contrast media volume, number of balloons, stents, guidewires, guide catheters, and procedural cost were calculated. In hospital abrupt closure rate and 6-month major adverse cardiovascular events (cardiac death, myocardial infarction, target vessel revascularization) rate were obtained. RESULTS: A total of 178 patients underwent IVUS-guided stent placement and 100 patients underwent angiographically guided stent implantation. There was no significant difference in procedure time (107 +/- 49 vs 100 +/- 50 minutes, P = .22), fluoroscopy time (33 +/- 24 vs 30 +/- 18 minutes, P = .36), contrast volume (411 +/- 157 vs 386 +/- 181 mL, P = .23), guide catheters (1.3 +/- 0.8 vs 1.3 +/- 0.6, P = .69), guidewires (1.6 +/- 1.2 vs 1.6 +/- 1.0, P = .99), balloons (2.4 +/- 1.0 vs 2.3 +/- 1.3, P = .58), and stents (1.7 +/- 0.9 vs 1.6 +/- 0.9, P = .42). Intraprocedural cost was significantly higher in the IVUS-guided group, $4142 +/- 1547 verus $3635 +/- 1949 (P = .03), which was primarily related to the cost of the IVUS catheter. However, the in-hospital acute vessel closure rate was significantly lower in the IVUS-guided group, 0.6% versus 4% (P = .04). There was a trend toward lower target vessel revascularization rate in the IVUS-guided group (11% vs 19%, P = .08). By multivariate analysis IVUS use was demonstrated to be an independent negative predictor of cardiac death, myocardial infarction, repeat revascularization, and abrupt stent closure with a relative risk of 0.49 (95% confidence interval of 0.25 to 0.98), and P = .04. CONCLUSIONS: The use of IVUS guidance during stent implantation does not significantly increase procedure time, fluoroscopy exposure, contrast volume, or device utilization. Furthermore, despite the increase in procedural cost, IVUS-guided stent implantation is associated with a significant decrease in the in-hospital abrupt closure rate and a trend toward a lower 6-month target vessel revascularization.

Aged↗
PubMed2001

Biodegradable polymer scaffolds with well-defined interconnected spherical pore network.

Scaffolding plays pivotal role in tissue engineering. In this work, a novel processing technique has been developed to create three-dimensional biodegradable polymer scaffolds with well-controlled interconnected spherical pores. Paraffin spheres were fabricated with a dispersion method, and were bonded together through a heat treatment to form a three-dimensional assembly in a mold. Biodegradable polymers such as PLLA and PLGA were dissolved in a solvent and cast onto the paraffin sphere assembly. After dissolving the paraffin, a porous polymer scaffold was formed. The fabrication parameters were studied in relation to the pore shape, interpore connectivity, pore wall morphology, and mechanical properties of the polymer scaffolds. The compressive modulus of the scaffolds decreased with increasing porosity. Longer heat treatment time of the paraffin spheres resulted in larger openings between the pores of the scaffolds. Foams of smaller pore size (100-200 microm) resulted in significantly lower compressive modulus than that of larger pore sizes (250-350 or 420-500 microm). The PLLA foams had a skeletal structure consisting of small platelets, whereas PLGA foams had homogeneous skeletal structure. The new processing technique can tailor the polymer scaffolds for a variety of potential tissue engineering applications because of the well-controlled architecture, interpore connectivity, and mechanical properties.

Absorbable Implants↗
PubMed2001

Tectorigenin, an isoflavone of Pueraria thunbergiana Benth., induces differentiation and apoptosis in human promyelocytic leukemia HL-60 cells.

Cytotoxic effects of six isoflavonoids, tectorigenin, glycitein, tectoridin, glycitin, 6''-O-xylosyltectoridin, and 6''-O-xylosylglycitin isolated from the flower of Pueraria thunbergiana Benth. together with genistein, a known differentiation and apoptosis inducer, were examined. Among these isoflavonoids, tectorigenin and genistein exhibited cytotoxicity against various human cancer cells; glycitein showed only mild cytotoxicity. These results suggest that the isoflavone structure and 5-hydroxyl group are crucial for the cytotoxic properties and that glycosides are inactive. Moreover, tectorigenin induced differentiation of human promyelocytic leukemia HL-60 cells to granulocytes and monocytes/macrophages, and caused apoptotic changes of DNA in the cells, as did genistein. Tectorigenin also inhibited autophosphorylation of epidermal growth factor (EGF) receptor by EGF and decreased the expression of Bcl-2 protein, with less activity than genistein. From these results, tectorigenin may be a possible therapeutic agent for leukemia.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Changes in serum lipid concentrations during iron depletion and after iron supplementation.

To investigate the effects of body iron depletion and iron supplementation on serum lipid concentrations, hematologic indices, iron markers, and serum lipid profiles were measured in 427 girls, age 14-19 yr. There were no significant differences in serum lipid concentrations between subjects with moderate iron deficiency anemia (blood Hb < 12.0 g/dL) and healthy controls. However, serum total cholesterol concentration (mean +/- SD, 148 +/- 16 mg/dL) in severely anemic subjects with blood Hb < 8.0 g/dL was significantly lower than in subjects with blood Hb > or = 14.0 g/dL (170 +/- 17 mg/dL) (p < 0.01). Moreover, serum triglyceride concentration in subjects with blood Hb > 14.0 g/dL was 2-fold higher than in the severely anemic subjects. Mean values of serum total cholesterol and triglyceride (149 +/- 17 mg/dL and 58 +/- 22 mg/dL) in girls with severe anemia were significantly elevated after iron supplementation (164 +/- 17 mg/dL and 98 +/- 26 mg/dL) (p < 0.01, respectively). In the severely anemic subjects, blood Hb concentration was correlated with serum total cholesterol (r = 0.49, p < 0.01) and triglyceride concentrations (r = 0.51, p < 0.01). These findings indicate that severe iron deficiency anemia in girls is attended by decreased concentrations of serum total cholesterol and triglyceride, and that these reduced serum lipid levels return to normal following iron supplementation.

Adolescent↗
PubMed2000

The new genotypic human calicivirus isolated in Seoul.

A new type of human calicivirus (HuCV) showing the classic cup-shaped surface morphology was identified in the stool sample from a child with symptoms of acute gastroenteritis in Seoul, Korea (SK virus). Genomic RNA was extracted directly from the stool sample, and the nucleotide sequence of 3.2 kb of the 3' end of SK virus was determined from cDNA. This region spanned sequences from the RNA-dependent RNA polymerase (RDRP) region in the open reading frame 1 (ORF1) to the 3' poly A tail. The non-structural and capsid protein coding sequences were fused in a single ORF as observed in Manchester type (Genogroup III). However, ORF2 of Manchester virus was missing in SK virus. In RDRP region, SK virus showed amino acid and nucleotide identities of 74-75% and 68-69% respectively, with those of Manchester virus, while showed 34-46% and 55-60% identities respectively with those of other human caliciviruses. However, capsid protein of SK virus showed a partial (29-46%) amino acid identity with those of other caliciviruses including Manchester type. The closest resemblance in amino acid (97-99%) and nucleotide sequence (85-86%) identities were found in RDRP region with Vanderbijlpark and Pretoria isolates recently found in South Africa. These results suggest that SK virus together with Vanderbijlpark and Pretoria isolates belong to a new type different from Manchester virus.

Amino Acid Sequence↗
PubMed2000

Hypoglycemic and hypolipidemic effects of tectorigenin and kaikasaponin III in the streptozotocin-lnduced diabetic rat and their antioxidant activity in vitro.

Tectorigenin and kaikasaponin III from the flowers of Pueraria thunbergiana showed potent hypoglycemic and hypolipidemic effects in the streptozotocin-induced diabetic rats. Intraperitoneal administration of these two compounds with 5 and 10 mg/kg, respectively, for seven days to streptozotocin-induced rats significantly reduced the blood glucose, total cholesterol, LDL- and VLDL-cholesterol and triglyceride levels when compared with those of control group. Glycitein in which 5-OH is unlinked and tectoridin (7-O-glycoside of tectorigenin) isolated from the flowers of P. thunbergiana did not improve hyperglycemia and hyperlipidemia. In addition, tectorigenin showed in vitro antioxidant effects on 1,1diphenyl-2-pirylhydrazyl (DPPH) radical, xanthine-xanthine oxidase superoxide anion radical, and lipid peroxidation in rat microsomes induced by enzymatic and non-enzymatic methods. We further found that tectorigenin and kaikasaponin III protected the Vero cell line (normal monkey kidney) from injury by hydrogen peroxide. From these findings, it seems likely that the antioxidant action of tectorigenin and kaikasaponin III may alleviate the streptozotocin-induced toxicity and contribute to hypoglycemic and hypolipidemic effects.

Animals↗
PubMed2000

Role of intracoronary ultrasound after high-pressure stent implantation.

BACKGROUND: Poststent high-pressure balloon inflation has been shown to improve clinical outcomes. However, it is unknown whether intracoronary ultrasound (ICUS) provides additional clinical guidance after initial high-pressure balloon inflation is used during stent placement. Thus the purpose of this study was to determine if stent deployment techniques are improved with ICUS imaging despite an optimal angiographic result achieved with high-pressure balloon inflation. METHODS AND RESULTS: Prospective data were collected on 96 consecutive patients in whom 151 stents were deployed. Stents and high-pressure balloons were angiographically sized 1:1 by visual estimation. High-pressure (> or =12 atm in all cases) balloon inflations were continued until angiographic completion (<10% residual stenosis), after which index ICUS imaging was performed. Stent apposition, symmetry, and lumen dimensions were evaluated. An optimal ICUS result was defined as full apposition of the stent, symmetry ratio > or =0.80, and acute gain > or =0.80 of the reference lumen area. If inadequate ICUS results were found, further dilations with higher pressures or larger balloons and subsequent stent reevaluation with ICUS were performed. Sixty-nine (46%) stents required additional balloon inflations. Of these stents, 35 (23%) had initial acute gains that were <80% of the reference lumen area. Forty-six (30%) stents were found to have unapposed struts and 24 (16%) had a symmetry ratio <0.80. In patients requiring additional inflations, minimum stent area increased from 7.6 +/- 2.2 mm(2) to 9.2 +/- 2.4 mm(2) (P <.0001). Similarly, complete stent apposition improved from 33% to 68% of total stents (P <.0001). After initial ICUS, higher-pressure dilations were performed in 40 patients, whereas larger balloons greater than or equal to ICUS reference vessel diameter were used in 33 patients. Follow-up was obtained in 95 (99%) patients. The overall major adverse cardiac event rate at 6 months was 9.3%, which consisted of 8 target vessel revascularizations and 1 abrupt closure requiring repeat intervention. CONCLUSIONS: Even when poststent high-pressure balloon inflation achieves an optimal angiographic result, ICUS assists in optimizing acute gain, symmetry, and apposition of intracoronary stents in approximately 50% of patients. Moreover, ICUS guidance is associated with low rates for target vessel revascularization and major adverse cardiac events at 6-month follow-up.

Aged↗