Biomedical subjects

K W Choi

Publications and source records attributed to K W Choi.

At least 37 records · Page 2Linked to original sources

PubMed2001

The effect of sildenafil on lower esophageal sphincter and body motility in normal male adults.

OBJECTIVE: Sildenafil relaxes smooth muscle by blocking type 5 phosphodiesterase, which destroys nitric oxide-stimulated cyclic guanosine monophosphate. The aim of this study is to investigate the change of lower esophageal sphincter (LES) and body motility with the lapse of time after sildenafil infusion in normal male adults. METHODS: After basal esophageal manometry in eight healthy male adult volunteers, we infused a 50-mg tablet of sildenafil dissolved in water in the stomach through the manometry catheter and observed the changes of LES and body motility with the lapse of time. We randomized the study population into two groups, and esophageal manometry was repeated in LES and body sequence in four volunteers and in body and LES sequence in the other four volunteers immediately after sildenafil infusion. RESULTS: LES resting pressure significantly decreased after sildenafil infusion. The body peristaltic amplitude gradually decreased and eventually disappeared, and the latency increased significantly after sildenafil infusion in both the proximal and distal esophagus. CONCLUSIONS: These data support that nitric oxide mediates LES relaxation and the timing of esophageal peristalsis. In the future, sildenafil can be tried in some esophageal motor disorders, which have defects in nitric oxide neuromuscular communication.

Adult↗

PubMed2001

Inducible nitric oxide synthase (iNOS) immunoreactivity and its relationship to cell proliferation, apoptosis, angiogenesis, clinicopathologic characteristics, and patient survival in pancreatic cancer.

BACKGROUND: The clinicopathological and biological significance of the expression of iNOS in pancreatic cancer remains unclear. The goal of this study was to determine the possible roles and clinical significance of iNOS expression in pancreatic cancer. METHODS: Seventy-two pancreatic adenocarcinoma tissue specimens were obtained by surgical resection. We investigated the immunohistochemical expression of iNOS in 72 patients with pancreatic cancer with respect to variable clinicopathological characteristics, proliferation activity (assessed by Ki-67 expression), apoptosis (assessed by TUNEL stain), and microvessel density (assessed by CD34 expression; angiogenesis). RESULTS: Immunohistochemical investigations demonstrated immunolabeling of tumor cells with anti-iNOS antibody. Positivity for iNOS was observed in 48/72 (66.7%). The expression of iNOS protein did not correlate with age, bilirubin, tumor marker, location, size, AJCC stage, differentiation, distant metastasis, or patient survival. No significant association was found between iNOS expression and proliferation or microvessel density in pancreatic cancer. Apoptotic index (AI) of positive iNOS expressions were significantly higher than negative expression (p < 0.001). CONCLUSION: Inducible nitric oxide synthase (iNOS) is expressed by human pancreatic cancer, and its presence is positively correlated with apoptosis of cancer cells that could provide the basis for the development of therapeutic strategies in human pancreatic cancer.

Adenocarcinoma↗

PubMed2000

Novel signaling from the peripodial membrane is essential for eye disc patterning in Drosophila.

The Drosophila eye disc is a sac of single layer epithelium with two opposing sides, the peripodial membrane (PM) and the disc proper (DP). Retinal morphogenesis is organized by Notch signaling at the dorsoventral (DV) boundary in the DP. Functions of the PM in coordinating growth and patterning of the DP are unknown. We show that the secreted proteins, Hedgehog, Wingless, and Decapentaplegic, are expressed in the PM, yet they control DP expression of Notch ligands, Delta and Serrate. Peripodial clones expressing Hedgehog induce Serrate in the DP while loss of peripodial Hedgehog disrupts disc growth. Furthermore, PM cells extend cellular processes to the DP. Therefore, peripodial signaling is critical for eye pattern formation and may be mediated by peripodial processes.

Animals↗

PubMed2000

An increased rectal maximum tolerable volume and long anal canal are associated with poor short-term response to biofeedback therapy for patients with anismus with decreased bowel frequency and normal colonic transit time.

PURPOSE: Biofeedback is an effective therapy for a majority of patients with anismus. However, a significant proportion of patients still failed to respond to biofeedback, and little has been known about the factors that predict response to biofeedback. We evaluated the factors associated with poor response to biofeedback. METHODS: Biofeedback therapy was offered to 45 patients with anismus with decreased bowel frequency (less than three times per week) and normal colonic transit time. Any differences in demographics, symptoms, and parameters of anorectal physiologic tests were sought between responders (in whom bowel frequency increased up to three times or more per week after biofeedback) and nonresponders (in whom bowel frequency remained less than three times per week). RESULTS: Thirty-one patients (68.9 percent) responded to biofeedback and 14 patients (31.1 percent) did not. Anal canal length was longer in nonresponders than in responders (4.53 +/- 0.5 vs. 4.08 +/- 0.56 cm; P = 0.02), and rectal maximum tolerable volume was larger in nonresponders than in responders. (361 +/- 87 vs. 302 +/- 69 ml; P = 0.02). Anal canal length and rectal maximum tolerable volume showed significant differences between responders and nonresponders on multivariate analysis (P = 0.027 and P = 0.034, respectively). CONCLUSIONS: This study showed that a long anal canal and increased rectal maximum tolerable volume are associated with poor short-term response to biofeedback for patients with anismus with decreased bowel frequency and normal colonic transit time.

Adult↗

PubMed2000

Evaluation of individual symptoms cannot predict presence of gastric hypersensitivity in functional dyspepsia.

Recently, the concept of gastric hypersensitivity was introduced as an important factor in the pathophysiology of functional dyspepsia (FD), but it is unclear which symptoms can predict the presence of gastric hypersensitivity. Therefore, we evaluated the relationship between common symptoms of FD and various parameters measured by gastric barostat in FD patients. Gastric barostat tests were performed in 64 FD patients and 20 healthy control subjects without gastrointestinal symptoms. Individual symptoms such as early satiety, postprandial fullness, sense of delayed emptying, nausea, vomiting, and epigastric soreness were collected and graded as mild to severe. Basal tone, gastric compliance, and postprandial receptive relaxation were similar in controls and patients, the threshold of abdominal discomfort was lower in FD patients than in controls (8.9 +/- 3.6 mm Hg and 14.5 +/- 3.7 mm Hg, respectively, P < 0.05). However, there were no significant differences in the threshold of abdominal discomfort according to the severity of individual symptoms. In conclusion, a simple evaluation of individual symptoms could not predict the presence of gastric hypersensitivity.

Adult↗

PubMed1999

Discs Lost, a novel multi-PDZ domain protein, establishes and maintains epithelial polarity.

Polarization of epithelial cells depends on a hierarchical process whereby specific membrane-associated proteins become targeted to specialized membrane domains. Here, we describe a novel Drosophila protein, Discs Lost (DLT), that plays a crucial role in the polarization of embryonic epithelia during cellular blastoderm formation. At subsequent stages of development, DLT interacts with the apical determinant Crumbs (CRB) and the laterally localized protein Neurexin IV (NRX IV). Mutations in dlt or double-stranded RNA interference lead to aberrant localization of CRB and NRX IV and cause a concomitant loss of epithelial cell polarity. Hence, DLT is required to establish and maintain cell polarity and participates in different molecular complexes that define apical and lateral membrane domains.

Amino Acid Sequence↗

PubMed1999

The etiologic role of gastric hypersensitivity in functional dyspepsia in Korea.

To evaluate the role of gastric hypersensitivity and the relationship between gastric hypersensitivity and delayed gastric emptying in Korean functional dyspepsia (FD) patients, the authors performed gastric barostat and gastric emptying scintigraphy in 64 FD patients and compared these results with those of control subjects. Basal tones and gastric compliance were similar in control subjects and patients. However, threshold of abdominal discomfort was lower in FD patients than in control subjects (8.9 +/- 3.6 mmHg and 14.5 +/- 3.7 mmHg respectively; p < 0.05). Twenty-four of 64 patients (37.5%) experienced abdominal discomfort at a pressure less than 7 mmHg above minimal distending pressure (corresponding to the 95th percentile of normal values). Half time of solid-phase gastric emptying in patients and control subjects was not significantly different. Twenty-three of 64 patients (35.9%) had delayed gastric emptying compared with control subjects (normal ranges were mean +/- two standard deviations in control subjects). Thresholds of abdominal discomfort were not significantly different in patients with and without delayed gastric emptying (9.3 +/- 4.0 mL/mmHg vs. 8.6 +/- 3.3 mL/mmHg). There were also no significant differences in the proportion of patients with delayed gastric emptying between patients with and without gastric hypersensitivity. In conclusion, gastric hypersensitivity plays an important role in FD, and the presence of gastric hypersensitivity was not related to the presence of delayed gastric emptying.

Abdominal Pain↗

PubMed1999

Lack of association of Helicobacter pylori infection with gastric hypersensitivity or delayed gastric emptying in functional dyspepsia.

OBJECTIVE: We evaluated the relationship between Helicobacter pylori (H. pylori) infection and gastric sensitivity to distention or gastric emptying rate to define the role of H. pylori in the pathogenesis of functional dyspepsia. METHODS: Gastric barostat, gastric emptying scintigraphy, and 13C urea breath test were performed in 34 consecutive patients with functional dyspepsia. RESULTS: Between H. pylori-positive and -negative patients with functional dyspepsia, there were no significant differences in basal tone (57.2 +/- 15.0 ml vs 66.8 +/- 18.3 ml), compliance (41.0 +/- 11.2 ml/mm Hg vs 38.2 +/- 11.8 ml/mm Hg), threshold of first sense (3.6 +/- 2.7 mm Hg vs 2.3 +/- 1.5 mm Hg), threshold of abdominal discomfort (9.4 +/- 4.0 mm Hg vs 7.3 +/- 1.9 mm Hg), and postprandial receptive relaxation (115.4 +/- 89.7 ml vs 99.0 +/- 88.7 ml), measured by gastric barostat. Half gastric emptying time (88.6 +/- 24.5 min vs 91.4 +/- 21.6 min) and retention rate at 120 min (32.8 +/- 17.8% vs 41.9 +/- 20.1%) were also similar between the two groups. CONCLUSION: H. pylori infection was not associated with gastric hypersensitivity to distention or delayed gastric emptying.

Abdominal Pain↗

PubMed1999

Ten-year cardiovascular risk in a Hong Kong population.

BACKGROUND: Cardiovascular disease is a major health issue in Hong Kong. We conducted a screening program to assess the 10-year risk for the population and to assess the potential benefit of large-scale screening in Hong Kong. METHOD: A local screening program for cardiovascular risk was carried out in a health service network with a total of 17,716 participants. Retrospective data analysis for the prevalence and distribution of the various risk factors was performed. The data were then applied to calculate the 10-year risk of each individual, according to the European Task Force coronary risk chart. RESULTS: Of the participants, 54.2% had total cholesterol levels > 5.2 mmol/l; 28.7% had body mass index > 25 kg/m2; 18.5% were hypertensive; 15.1% were smokers; and 3.7% had diabetes mellitus. There were 35.5% of the screened population who had at least two risk factors and 10.9% had at least three risk factors. A total of 9049 individuals satisfied the criteria for the European Task Force guidelines and were selected for 10-year cardiovascular risk analysis. We calculated that 68.0% of the male population had at least 10% risk and 41.5% had at least 20% risk of developing a coronary heart event within 10 years. Among women, 48.2% of the population carried at least 10% risk and 2.8% carried at least 20% risk. CONCLUSION: The calculated 10-year risk of the population, particularly for men, is significant. Our study demonstrated that mass screening is feasible, and has the benefit of early identification of high-risk individuals, which could be a reasonable strategy for cost-effective medicine.

Adolescent↗

PubMed1998

Fringe is essential for mirror symmetry and morphogenesis in the Drosophila eye.

An early event in Drosophila eye development is the division of the eye disc into dorsoventral domains. The dorsoventral pattern is displayed in the adult compound eye as a distinct mirror symmetry across the dorsoventral midline or equator. The dorsoventral axis is also implicated in organizing early development of the eye, as retinal differentiation is initiated at the posterior dorsoventral midline. Here we show that Fringe is expressed specifically in the ventral half of the undifferentiated eye disc, thus creating a dorsoventral boundary. Ectopic Fringe borders that are generated by clones of fringe cells can reverse the planar polarity of photoreceptor clusters, indicating that the Fringe boundary is crucial for the induction of mirror symmetry. Lack of a Fringe boundary disrupts equatorial expression of Notch signalling proteins and causes a complete failure of eye development. Our results indicate that the formation of the Fringe boundary and subsequent Notch signalling at the equator are essential for organizing mirror symmetry and eye morphogenesis.

Animals↗

PubMed1998

Phylogenetic analysis of the nef gene reveals a distinctive monophyletic clade in Korean HIV-1 cases.

To study the genetic variation of the HIV-1 strains prevalent in South Korea, we analyzed the nef sequences derived from 46 HIV-1-positive individuals living in various geographic regions in Korea. Phylogenetic analysis revealed four subtypes of HIV-1: A (3 patients), B (41 patients), D (1 patient), and a type that could not be clearly classified to any known subtype (1 patient). Thirty-five of the 41 Korean subtype B isolates formed a distinct monophyletic clade that is not related to any of the international sequences from the Los Alamos Database or GenBank as of June 1997. Indeed, the presence of unique conserved sequences was identified among the Korean isolates in this Korean subtype B group. The variations in the nucleotide sequences of a majority (32 of 35) subtype B samples within the Korean clade were 1.9% to 8.8%, and amino acid sequences varied from 3.9% to 15.5%. These results suggest that HIV-1 strains currently present in South Korea might have originated from a few sources or might be developing through a certain selective pressure. This is the first report on the molecular nature of the HIV-1 infection present in South Korea.

Adolescent↗

PubMed1998

Detection of reactive oxygen species (ROS) and apoptosis in human fragmented embryos.

In human in-vitro fertilization (IVF)-embryo transfer, the in-vitro culture environment differs from in-vivo conditions in that the oxygen concentration is higher, and in such conditions the mouse embryos show a higher concentration of reactive oxygen species (ROS) in simple culture media. ROS are believed to cause damage to cell membranes and DNA fragmentation in somatic cells. This study was conducted to ascertain the level of H2O2 concentration within embryos and the morphological features of cell damage induced by H2O2. A total of 62 human oocytes and embryos (31 fragmented, 15 non-fragmented embryos, 16 unfertilized oocytes) was obtained from the IVF-embryo transfer programme. The relative intensity of H2O2 concentrations within embryos was measured using 2',7'-dichlorodihydrofluorescein diacetate by Quanti cell 500 fluorescence imaging and DNA fragmentation was observed with transmission electron microscopy and an in-situ apoptosis detection kit. The H2O2 concentrations were significantly higher in fragmented embryos (72.21 +/- 9.62, mean +/- SEM) compared to non-fragmented embryos (31.30 +/- 3.50, P < 0.05) and unfertilized oocytes (30.75 +/- 2.67, P < 0.05). Apoptosis was observed only in fragmented embryos, and was absent in non-fragmented embryos. Electron microscopic findings confirmed apoptotic bodies and cytoplasmic condensation in the fragmented blastomeres. We conclude that there is a direct relationship between increased H2O2 concentration and apoptosis, and that further studies should be undertaken to confirm these findings.

Apoptosis↗

PubMed1998

mirror, a Drosophila homeobox gene in the Iroquois complex, is required for sensory organ and alula formation.

The Drosophila notum, the dorsal body wall of the thorax, is subdivided genetically into longitudinal domains (Calleja, M., Moreno, E., Pelaz, S. and Morata, G. (1996) Science 274, 252-255). Two homeobox genes clustered in the iroquois complex, araucan and caupolican, regulate proneural genes and are required for development of sensory bristles in the lateral notum (Gomez-Skarmeta, J. L., del Corral, R. D., de la Calle-Mustienes, E., Ferres-Marco, D. and Modolell, J. (1996) Cell 85, 95-105). An iroquois-related homeobox gene, mirror, was recently isolated and is localized close to the iroquois complex region (McNeil, H., Yang, C.-H., Brodsky, M., Ungos, J. and Simon, M. A. (1997) Genes and Development 11, 1073-1082; this study). We show that mirror is required for the formation of the alula and a subset of sensory bristles in the lateral domain of the notum. Genetic analysis suggests that mirror and the other iroquois genes interact to form the alula as well as the sensory organs. Based on similarities between mirror and the iroquois genes in their genetic map positions, expression, protein structure and function, mirror is considered a new member of the iroquois complex and is involved in prepatterning sensory precursor cells in the lateral notum.

Animals↗

PubMed1998

Femoral anteversion: estimation by 3D modelling.

Femoral anteversion is the inclination of the femoral neck axis with reference to the tangent plane of the distal femur. For estimating femoral anteversion, following three major parameters are required; the neck axis, the long axis, the knee axis. Conventional methods on the basis of 2D images are ambiguous to determine these major axes. As the femur has a complex 3 dimensional structure, the 3 dimensional model should be applied for accurate and reliable measurement of femoral anteversion. In this paper, we model femur and define three parameters. The neck axis is defined from the femoral head and neck model. The long axis is determined from the cylindrical model of the femoral shaft. The knee axis is also determined from the model of femoral condyles. According to the definition of the femoral anteversion, the femoral anteversion is efficiently estimated from these models. 30 specimens were tested by conventional 2D imaging method, 3D imaging method which was developed by authors and the new 3D modelling method. The study provides accurate, fast and human factor free measurement for femoral anteversion.

Algorithms↗

PubMed1998

Role of hyperinsulinemia and glucose intolerance in the pathogenesis of nonalcoholic fatty liver in patients with normal body weight.

OBJECTIVES: The pathogenesis of nonalcoholic fatty liver in non-obese persons is poorly understood. We aimed to elucidate whether hyperinsulinemia and glucose intolerance are associated with development of fatty liver in patients with normal body weight. METHODS: Forty-seven patients with fatty liver were divided into non-obese (n = 25) and obese groups (n = 22) according to age adjusted body mass index. Inclusion criteria were as follows: (1) elevated transaminase levels during more than 3 months of follow up period, (2) no detectable HBsAg or anti-HCV in the serum, (3) alcohol consumption less than 40 gm/week, (4) no use of potential hepatotoxic drugs within 3 months and (4) sonographic evidence of fatty liver(moderate to severe degree). Baseline insulin levels and oral glucose tolerance test using 75gm of glucose were performed and the results were compared in each group of patients. RESULTS: Mean baseline insulin levels were elevated in both groups above the reference value, 9.3 +/- 3.5 microU/L in non-obese group and 9.9 +/- 3.5 microU/L in obese group (p = 0.26). Seventeen of non-obese patients (68%) had elevated basal insulin level and 16 of obese patients (73%) had elevated basal insulin level (p = 0.39). In oral glucose tolerance test, there was no difference in glucose level between non-obese and obese groups from O minute to 180 minutes (p > 0.05). Eleven patients from the non-obese group (44%) and 8 patients from the obese group (36%) had either impaired glucose tolerance or diabetes (p = 0.29). CONCLUSION: Our data suggest that hyperinsulinemia and glucose intolerance may play a role in the pathogenesis of fatty liver in patients with normal body weight as well as in patients with obesity.

Adult↗

PubMed1997

Expression of a cDNA encoding Phytolacca insularis antiviral protein confers virus resistance on transgenic potato plants.

To develop an antiviral agent and virus-resistant plants, a cDNA clone encoding Phytolacca insularis antiviral protein (PIP) was isolated from a cDNA library constructed with poly(A)+ RNA purified from leaves of P. insularis. The PIP cDNA contains an open reading frame encoding 307 amino acids. The deduced amino acid sequence includes a putative signal sequence of 22 amino acids at the N-terminus. The amino acid sequence of PIP shares 84% homology with that of the pokeweed antiviral protein (PAP). In addition, the mature PIP exhibits the conserved putative active site found in other ribosome-inactivating proteins (RIPs). Recombinant PIP (rPIP) synthesized in Escherichia coli inhibits protein synthesis in vitro in rabbit reticulocyte lysate through the N-glycosidase activity in a similar manner with other RIPs. Local lesion assays with purified rPIP revealed that it inhibits infection of various viruses to plants. Transgenic potato plants expressing the PIP cDNA under the control of the cauliflower mosaic virus 35S promoter are resistant to viruses, such as potato virus X, potato virus Y, and potato leafroll virus. These results suggest that the PIP cDNA could be used for the development of an antiviral agent and transgenic plants resistant against a broad spectrum of plant viruses infecting through both mechanical and aphid transmission.

Amino Acid Sequence↗

PubMed1997

Current topics on digestive disease in Korea.

This is a summary of the research topics, of current interest, relating to digestive disease in Korea. This review is based on the subjects of the papers that were accepted for presentation at the 34th Annual Meeting of the Korean Society of Gastroenterology and the 39th Semiannual Meeting of the Korean Society of Gastrointestinal Endoscopy held November 22-24, 1995, in Seoul. The most popular topics were on Helicobacter pylori infection. These included experimental papers on the pathogenesis of bacteria-associated gastritis and the duodenal ulcer. Recently, the increase in the number of papers published on the motility of the gastrointestinal and pancreaticobiliary tracts is quite remarkable. Molecular genetic works on oncogenesis using cultured tumour cell lines, on the enzyme expression in the biopsied mucosal cells of the small intestine, and on the various expressions of viral genomes in the hepatocytes are among these recent topics of research. Clinical works, such as therapeutic endoscopy in malignant diseases and therapeutic trials in the hepatitis virus-associated chronic liver diseases are also popular topics.

Digestive System Diseases↗

PubMed1997

Arthropathy in Behçet's disease.

We analyzed the incidence, clinical features, and the long-term sequelae of arthropathy in 84 patients with Behçet's disease. After a mean disease duration of 44.7 months, 59 patients (70%) had at least 1 episode of arthropathy. Of these, arthropathy was present at the time of diagnosis in the majority of patients (75%). In the remainder, arthropathy developed 4 to 80 months (mean 29) after the diagnosis of Behçet's disease. Female patients were significantly more likely to have arthropathy than male patients (89 versus 56%, p = 0.006). The pattern of involvement was oligoarticular in 75%, monoarticular in 23%, and polyarticular in 2% of these patients. The most commonly involved site was the knee, followed by the ankle and the wrist. Radiologic examination of the involved site was normal in 80% of the patients. After a mean duration of arthropathy of 43.2 months, by the American College of Rheumatology (ACR) criteria, the functional class of the arthropathy was I-II in 88%, and III-IV in 12%. In conclusion arthropathy is a fairly common manifestation in patients with Behçet's disease, but crippling arthritis is relatively rare.

Adult↗