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Biomedical subjects

S K Choi

Publications and source records attributed to S K Choi.

At least 37 records · Page 2Linked to original sources

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↗

Does every patient with ureteropelvic junction obstruction need voiding cystourethrography?

PURPOSE: Voiding cystourethrography is routinely recommended to detect vesicoureteral reflux in children with ureteropelvic junction obstruction. Vesicouretral reflux coexisting with primary ureteropelvic junction obstruction is usually of low grade and resolves spontaneously after pyeloplasty, whereas pseudo ureteropelvic junction obstruction and obstruction secondary to high grade reflux usually present with a dilated ureter that is easily detected on real-time ultrasonography. We assessed the role of voiding cystourethrography in children with ureteropelvic junction obstruction by retrospectively evaluating the incidence and natural history of coexisting vesicourethral reflux. MATERIALS AND METHODS: We reviewed the records of 106 children younger than 15 years who underwent pyeloplasty for ureteropelvic junction obstruction at our hospital between January 1990 and December 1998. A patient who had initially undergone antireflux surgery later underwent pyeloplasty for newly developed secondary obstruction was not included in the analysis. The diagnosis of ureteropelvic junction obstruction was based on ultrasonography and diuretic renography. Preoperative voiding cystourethrography was performed in all patients to detect vesicourethral reflux. We categorized reflux as low grade if the ureters were not dilated and as high grade if the ureters were dilated and tortuous. RESULTS: There were 89 boys and 17 girls who underwent 115 pyeloplasties, including 9 who underwent bilateral pyeloplasty. Mean patient age at surgery was 27.4 months (63 infants, 6 between 1 and 2 years old, and 37 older than 2 years). Of these 106 patients 85 had unilateral (left side 64, right side 21) and 21 had bilateral ureteropelvic junction obstruction. Vesicourethral reflux was documented in 19 ureters of 12 children. Of the 85 cases of unilateral ureteropelvic junction obstructions 10 had vesicourethral reflux, which was bilateral 6, ipsilateral in 2 and contralateral in 2. Of the 21 cases of bilateral obstructions 2 had reflux, which was bilateral in 1 and was unilateral in 1. Reflux was low grade reflux in 6 and high grade in 6 cases. All low grade reflux disappeared spontaneously at an average period of 4.2 months (range 2 to 10) after pyeloplasty. All 6 patients with high grade reflux subsequently underwent antireflux surgery because of breakthrough urinary tract infection in 2 and persistent in 4 at an average of 36 months (range 3 to 112) after pyeloplasty. All high grade reflux coexisting with ureteropelvic junction obstruction was easily detected on real-time ultrasonography. CONCLUSIONS: Low grade reflux coexisting with ureteropelvic junction obstruction spontaneously disappeared after pyeloplasty, and all high grade reflux coexisting with obstruction was easily detected on ultrasonography using real-time mode. Therefore, we believe that indication for voiding cystourethrography in children with ureteropelvic junction obstruction should be limited to those with dilated ureters on ultrasonography.

Adolescent↗

A structurally biased combinatorial approach for discovering new anti-picornaviral compounds.

BACKGROUND: Picornaviruses comprise a family of small, non-enveloped RNA viruses. A common feature amongst many picornaviruses is a hydrophobic pocket in the core of VP1, one of the viral capsid proteins. The pocket is normally occupied by a mixture of unidentified, fatty acid-like moieties, which can be competed out by a family of capsid-binding, antiviral compounds. Many members of the Picornaviridae family are pathogenic to both humans and livestock, yet no adequate therapeutics exist despite over a decade's worth of research in the field. To address this challenge, we developed a strategy for rapid identification of capsid-binding anti-picornaviral ligands. The approach we took involved synthesizing structurally biased combinatorial libraries that had been targeted to the VP1 pocket of poliovirus and rhinovirus. The libraries are screened for candidate ligands with a high throughput mass spectrometry assay. RESULTS: Using the mass spectrometry assay, we were able to identify eight compounds from a targeted library of 75 compounds. The antiviral activity of these candidates was assessed by (i) measuring the effect on the kinetics of viral uncoating and (ii) the protective effect of each drug in traditional cell-based assays. All eight of the candidates exhibited antiviral activity, but three of them were particularly effective against poliovirus and rhinovirus. CONCLUSIONS: The results illustrate the utility of combining structure-based design with combinatorial chemistry. The success of our approach suggests that assessment of small, targeted libraries, which query specific chemical properties, may be the best strategy for surveying all of chemical space for ideal anti-picornaviral compounds.

Animals↗

Massive gastrointestinal bleeding caused by ectopic pancreas mimicking jejunal tumor.

BACKGROUND: Ectopic pancreas is usually an incidental finding at surgery or autopsy and rarely produces clinical symptoms. But it is capable of producing symptoms, depending on its location, size and involvement of the overlying mucosa. CASE REPORT: We report a case with massive gastrointestinal bleeding from ectopic pancreas mimicking jejunal tumor, confirmed by emergency operation. A 40-year-old male was admitted to Chonnam National University Hospital with a 2-day history of melena. A technetium-99m-labeled RBC scan showed massive radioactivity in loops of small bowel due to active bleeding. Superior mesenteric angiography revealed a hypervascular stained mass supplied by proximal jejunal branch. A computed tomographic scan of abdomen revealed an enhancing mass in the proximal jejunum. At emergency operation, bleeding from the center of the mass was found situated approximately 30 cm from the Treitz ligament. Segmental resection of the involved jejunum and end-to-end anastomosis were performed. Histologic examination of resected specimen revealed an ectopic pancreas. CONCLUSION: So far, there have been no case reports of massive gastrointestinal bleeding from ectopic pancreas mimicking jejunal tumor as described in our case. In every patient in whom ectopic pancreas can definitely be seen to cause clinical symptoms including gastrointestinal bleeding, the lesion should be excised.

Adult↗

Caffeine as a lipolytic food component increases endurance performance in rats and athletes.

Caffeine is one of the famous ergogenic aids in the athletic field. Caffeine has been known to stimulate lipolysis that spares stored glycogen utilization during moderate intensity exercise. Therefore, we investigated the effects of caffeine ingestion on exercise performance in rats and athletes. Rats were administered the caffeine (6 mg/kg) 1 h prior to the exercise then were run on a treadmill at a speed of 20 m/min. They were decapitated at 0 min, 30 min, 60 min of exercise, and exhausted time point. Human subjects ingested the caffeine (5 mg/kg) 1 h prior to the exercise. They exercised on a cycle ergometer at 60% of their VO2max for 45 min, and then the exercise intensity was increased to 80% of their VO2max until exhaustion. Blood and breathing gas samples were collected and calculated every 10 min during exercise. Respiratory exchange ratio of the caffeine trial was significantly lower than that of the placebo trial in the athletes' study (p<0.05). Blood free fatty acid (FFA) levels in studies of both rats and athletes were increased by caffeine ingestion during exercise (p<0.05). Blood lactate levels were also increased during exercise in both rats and athletes (p<0.05). Increased FFA and glycerol concentrations reduced glycogen utilization during exercise compared with placebo group in rats. In addition, endurance time to exhaustion was significantly increased by the caffeine ingestion in both rats and athletes (p<0.05). These results suggest that the caffeine ingestion enhanced endurance performance resulting from spare stored glycogen with increasing lipolysis from adipose tissues and fat oxidation during exercise both in rats and in athletes.

Adipose Tissue↗

Effects of carnitine coingested caffeine on carnitine metabolism and endurance capacity in athletes.

The purpose of this study was to examine whether caffeine (CAF), carnitine (CAR), or CAF+CAR mixture administration affects exercise endurance time via carnitine metabolism. Water (CON), CAF, CAR, or CAF+CAR mixture was administered to five male rugby athletes participating in this study by a randomized double-blind fashion who were made to ride a cycle ergometer for exercise. The CAF effect on exercise endurance time was small, but the CAR trial significantly increased the exercise endurance time compared with CON trial; a further CAF+CAR mixture trial had greater effects on the exercise endurance time than those of a CON, CAF, or CAR trial. A CAR or CAF+CAR mixed trial increased urinary nonesterified carnitine (NEC) and total carnitine (TCAR), but no changes were observed in acid-soluble acylcarnitine (ASAC) and acid-insoluble acylcarnitine (AIAC) excretion. A CAR or CAF+CAR mixed trial resulted in higher levels of plasma NEC, ASAC, and TCAR fractions than the CON and CAF trials did on exhaustion time. Total cholesterol, triglyceride, and free fatty acid in blood were significantly increased at exhaustion time, but they were not affected in the CAF or the CAR trial. These results suggest that carnitine ingestion could promote fat oxidation, resulting in higher endurance performance in athletes, and especially these ergogenic effects of carnitine coingested with caffeine may be greater than those of carnitine alone.

Adult↗

A case of hemorrhagic gallbladder paraganglioma causing acute cholecystitis.

Gallbladder paraganglioma is a very rare tumor and so far only a few cases have been reported. Most of these were asymptomatic and were found incidentally during operation. Recently, we experienced a gallbladder paraganglioma that gave rise to hemorrhage, which in turn caused acute cholecystitis. Our case involved a 45 year-old female patient complaining of an intermittent right upper abdominal pain. After a preoperative evaluation, cholecystectomy and lymphadenectomy were performed under the impression of gallbladder cancer with acute cholecystitis. Postoperative pathologic examination revealed a hemorrhagic gallbladder paraganglioma accompanied by acute cholecystitis. Immunohistochemical staining of the chief cells for neuron specific enolase, chromogranin and synaptophysin were positive. Sustentacular cells also stained positively for S100 protein.

Acute Disease↗

Aggressive epithelial odontogenic ghost cell tumor in the mandible: CT and MR imaging findings.

We report a case of aggressive epithelial odontogenic ghost cell tumor arising from the mandible in a 32-year-old man. On CT and MR studies, the tumor was seen as a large, heterogeneous soft-tissue mass that caused marked destruction of the mandible and invaded the mouth floor and tongue base. The tumor displayed a variety of densities and signal intensities on CT and MR images, which correlated well with the degree of cellularity of epithelial islands, abundance of ghost cells and eosinophilic materials, calcification, and cystic areas on histologic sections. Owing to the unpredictable biological behavior of this type of tumor, careful, long-term follow-up is highly recommended.

Adult↗

Closed-loop identification and control application for dissolved oxygen concentration in a full-scale coke wastewater treatment plant.

The objective of this paper is to apply a closed-loop identification to actual dissolved oxygen control system in the coke wastewater treatment plant. It approximates the dissolved oxygen dynamics to a high order model using the integral transform method and reduces it to the first-order plus time delay (FOPTD) or second-order plus time delay (SOPTD) for the PID controller tuning. To experiment the process identification on the real plant, a simple set-point change of the speed of surface aerator under the closed-loop control without any mode change was used as an activation signal of the identification. The full-scale experimental results show a good identification performance and a good tracking ability for set-point change. As a result of improved control performance, the fluctuation of dissolved oxygen concentration variation has been decreased and the electric power saving has been accomplished.

Biomass↗

The joining of ribosomal subunits in eukaryotes requires eIF5B.

Initiation of eukaryotic protein synthesis begins with the ribosome separated into its 40S and 60S subunits. The 40S subunit first binds eukaryotic initiation factor (eIF) 3 and an eIF2-GTP-initiator transfer RNA ternary complex. The resulting complex requires eIF1, eIF1A, eIF4A, eIF4B and eIF4F to bind to a messenger RNA and to scan to the initiation codon. eIF5 stimulates hydrolysis of eIF2-bound GTP and eIF2 is released from the 48S complex formed at the initiation codon before it is joined by a 60S subunit to form an active 80S ribosome. Here we show that hydrolysis of eIF2-bound GTP induced by eIF5 in 48S complexes is necessary but not sufficient for the subunits to join. A second factor termed eIF5B (relative molecular mass 175,000) is essential for this process. It is a homologue of the prokaryotic initiation factor IF2 (re and, like it, mediates joining of subunits and has a ribosome-dependent GTPase activity that is essential for its function.

Amino Acid Sequence↗

Cloning of a new Bacillus thuringiensis cry1I-type crystal protein gene.

A new cry1I-type gene, cry1Id1, was cloned from a B. thuringiensis isolate, and its nucleotide sequence was determined. The deduced amino acid sequence of Cry1Id1 is 89.7%, 87.2%, and 83.4% identical to the Cry1Ia, Cry1Ib, and Cry1Ic proteins, respectively. The upstream sequence of the cry1Id1 structural gene was not functional as promoter in B. subtilis. The Cry1Id1 protein, purified from recombinant E. coli cells, had a toxicity comparable to that of Cry1Ia against Plutella xylostella, but it was significantly less active than Cry1Ia against Bombyx mori. Cry1Id1 was not active against the coleopteran insect, Agelastica coerulea.

Amino Acid Sequence↗

Massive gastrointestinal bleeding from jejunal varices.

We report a patient with massive gastrointestinal bleeding from jejunal varices, confirmed by emergency laparotomy. A 54-year-old woman was admitted to Chonnam National University Hospital with a 5-day history of melena with hematochezia. Fifteen years previously, she had undergone cholecystectomy for gallstone. Seven years previously, she had undergone an operation because of possible common bile duct stone. The details of this operation were not known. Upper gastrointestinal endoscopy revealed no varices in the esophagus, stomach, and proximal duodenum. Colonoscopy demonstrated black-colored blood clots throughout the colon. A technetium-99m-labeled red blood cell (RBC) scan showed active proximal small bowel bleeding. Abdominal aortic angiography revealed mesenteric varices in the upper abdomen, but no active bleeding source was recognized. Because of the patient's continued massive gastrointestinal bleeding despite medical therapy, emergency laparotomy was performed. We found evidence of micronodular cirrhosis of the liver and an apparent Roux-en-Y anastomosis. There were numerous collateral variceal vessels in the jejunal limb with the liver and abdominal wall. Segmental resection of the involved jejunum and end-to-end anastomosis were perdilated formed. Histologic examination revealed submucosal veins with mucosal erosion.

Female↗

New aspects of hepatic fibrosis.

Hepatic stellate cells are the major source of extracellular matrix proteins in hepatic fibrosis, including Type I collagen. In response to liver injury, the hepatic stellate cells change from a quiescent to an activated phenotype. This activation process includes a phenotypic change to a myofibroblast-like cell, increased proliferation rate, loss of retinoid stores, increased production of extracellular matrix proteins, chemokines, and cytokines, and contractility. Ongoing studies are characterizing the genes that are differentially expressed in the quiescent and activated hepatic stellate cells. We have also investigated the regulation of Type I collagen expression, the cleavage of collagen propeptides, and the formation of collagen cross-links. Understanding these pathways may provide new insights into the molecular pathogenesis of hepatic fibrosis.

Bone Morphogenetic Proteins↗

Analysis of tnrA alleles which result in a glucose-resistant sporulation phenotype in Bacillus subtilis.

Bacillus subtilis cells cannot sporulate in the presence of catabolites such as glucose. During the analysis of Tn10-generated mutants, we found that deletion of the C-terminal region of the tnrA gene, which encodes a global regulator that positively regulates a number of genes in response to nitrogen limitation, results in a catabolite-resistant sporulation phenotype. Analyses of nrg-lacZ and nasB-lacZ, which are activated by TnrA under nitrogen limitation, showed that C-terminally truncated TnrA activates nitrogen-regulated genes constitutively. The relief of catabolite repression of sporulation may result from the uncontrolled expression of the TnrA-regulated genes.

Alleles↗