Biomedical subjects

I J Choi

Publications and source records attributed to I J Choi.

At least 37 records · Page 2Linked to original sources

PubMed2004

Measurement of nonrandom event-by-event fluctuations of average transverse momentum in square root of (sNN)=200 GeV Au+Au and p+p collisions.

Event-by-event fluctuations of the average transverse momentum of produced particles near midrapidity have been measured by the PHENIX Collaboration in square root of (sNN)=200 GeV Au+Au, and p+p collisions at the Relativistic Heavy Ion Collider. The fluctuations are observed to be in excess of the expectation for statistically independent particle emission for all centralities. The excess fluctuations exhibit a dependence on both the centrality of the collision and on the pT range over which the average is calculated. Both the centrality and pT dependence can be well reproduced by a simulation of random particle production with the addition of contributions from hard-scattering processes.

Journal Article↗

PubMed2004

J/psi production from proton-proton collisions at square root of s=200 GeV.

J/psi production has been measured in proton-proton collisions at square root of s=200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at the Relativistic Heavy Ion Collider. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 4.0+/-0.6(stat)+/-0.6(syst)+/-0.4(abs) mu b. The mean transverse momentum is 1.80+/-0.23(stat)+/-0.16(syst) GeV/c.

Journal Article↗

PubMed2003

Midrapidity neutral-pion production in proton-proton collisions at square root s = 200 GeV.

The invariant differential cross section for inclusive neutral-pion production in p+p collisions at sqrt[s]=200 GeV has been measured at midrapidity (|eta|<0.35) over the range 1<p(T) less, similar 14 GeV/c by the PHENIX experiment at the Relativistic Heavy Ion Collider. Predictions of next-to-leading order perturbative QCD calculations are consistent with these measurements. The precision of our result is sufficient to differentiate between prevailing gluon-to-pion fragmentation functions.

Journal Article↗

PubMed2003

Elliptic flow of identified hadrons in Au+Au collisions at sqrt sNN =200 GeV.

The anisotropy parameter (v(2)), the second harmonic of the azimuthal particle distribution, has been measured with the PHENIX detector in Au+Au collisions at sqrt[s(NN)]=200 GeV for identified and inclusive charged particle production at central rapidities (|eta|<0.35) with respect to the reaction plane defined at high rapidities (|eta|=3-4 ). We observe that the v(2) of mesons falls below that of (anti)baryons for p(T)>2 GeV/c, in marked contrast to the predictions of a hydrodynamical model. A quark-coalescence model is also investigated.

Journal Article↗

PubMed2003

Scaling properties of proton and antiproton production in sqrt[s(NN)]=200 GeV Au+Au collisions.

We report on the yield of protons and antiprotons, as a function of centrality and transverse momentum, in Au+Au collisions at sqrt[s(NN)]=200 GeV measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider. In central collisions at intermediate transverse momenta (1.5<p(T)<4.5 GeV/c) a significant fraction of all produced particles are protons and antiprotons. They show a centrality-scaling behavior different from that of pions. The pmacr;/pi and p/pi ratios are enhanced compared to peripheral Au+Au, p+p, and e(+)e(-) collisions. This enhancement is limited to p(T)<5 GeV/c as deduced from the ratio of charged hadrons to pi(0) measured in the range 1.5<p(T)<9 GeV/c.

Journal Article↗

PubMed2003

Absence of suppression in particle production at large transverse momentum in sqrt[s(NN)]=200 GeV d+Au collisions.

Transverse momentum spectra of charged hadrons with p(T)<8 GeV/c and neutral pions with p(T)<10 GeV/c have been measured at midrapidity by the PHENIX experiment at BNL RHIC in d+Au collisions at sqrt[s(NN)]=200 GeV. The measured yields are compared to those in p+p collisions at the same sqrt[s(NN)] scaled up by the number of underlying nucleon-nucleon collisions in d+Au. The yield ratio does not show the suppression observed in central Au+Au collisions at RHIC. Instead, there is a small enhancement in the yield of high momentum particles.

Journal Article↗

PubMed2003

Suppressed pi(0) production at large transverse momentum in central Au+Au collisions at sqrt[s(NN)]=200 GeV.

Transverse momentum spectra of neutral pions in the range 1<p(T)<10 GeV/c have been measured at midrapidity by the PHENIX experiment at BNL RHIC in Au+Au collisions at sqrt[s(NN)]=200 GeV. The pi(0) multiplicity in central reactions is significantly below the yields measured at the same sqrt[s(NN)] in peripheral Au+Au and p+p reactions scaled by the number of nucleon-nucleon collisions. For the most central bin, the suppression factor is approximately 2.5 at p(T)=2 GeV/c and increases to approximately 4-5 at p(T) approximately 4 GeV/c. At larger p(T), the suppression remains constant within errors. The deficit is already apparent in semiperipheral reactions and increases smoothly with centrality.

Journal Article↗

PubMed2003

Prediction of lymph nodes metastasis by sentinel node biopsy in gastric cancer.

AIM: The application of sentinel node (SN) biopsy in gastric cancer remains controversial. In this study, detection rate and predictive values of SN biopsy were determined to evaluate its feasibility in gastric cancer. Various clinicopathologic features were also analysed to determine the factors affecting the detection rate and predictive values. METHODS: Seventy-one gastric adenocarcinoma patients without serosal invasion and distant metastasis, were studied. One percent isosulfan blue stained nodes were defined as SNs, and standard gastrectomy with D2 lymphadenectomy was performed. All lymph nodes were studied by hematoxylin and eosin staining. RESULTS: SNs were identified in 65 of 71 patients and average number of SNs per patient was 2.5 (range 1-8). Among the 65 patients with SNs, metastatic SNs were found in 11 and the remaining 54 were free of metastasis. In eight of the 11 patients with metastasis of the SNs, metastases were also identified in non-SNs. CONCLUSIONS: SN biopsy is feasible in early stage gastric cancer. However, complementary procedures may be needed to improve the detection rate and predictive values. SNs biopsy results should be treated with caution in male patients and for tumours at the upper part of stomach due to the low detection rate.

Adenocarcinoma↗

PubMed2002

Efficacy of low-dose clarithromycin triple therapy and tinidazole-containing triple therapy for Helicobacter pylori eradication.

BACKGROUND: Proton pump inhibitor-based triple therapies are recommended as the first-line treatment for Helicobacter pylori eradication. AIM: To evaluate the efficacies of low-dose clarithromycin triple therapy and tinidazole-containing triple therapy in a metronidazole resistance prevalent area and to compare the efficacies with standard triple therapy. METHODS: In a randomized, multicentre, prospective study, a total of 352 patients with duodenal ulcer or non-ulcer dyspepsia were randomly divided into three groups according to the administered regimen: OAC250 group (omeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 250 mg), OAC500 group (omeprazole, 20 mg, amoxicillin, 1000 mg, and clarithromycin, 500 mg) and OTC group (omeprazole, 20 mg, tinidazole, 500 mg, and clarithromycin, 500 mg). The three groups received each regimen twice daily for 7 days. Upper gastrointestinal endoscopy was performed before and 4 weeks after treatment. H. pylori status was determined by rapid urease test and 13C urea breath test. RESULTS: The eradication rates in the OAC250, OAC500 and OTC groups were 76.2%, 65.7% and 64.8% (95% confidence interval: 67.9-84.4%, 56.7-74.8% and 55.7-73.9%), respectively, by intention-to-treat analysis (P=0.149) and 92.8%, 87.2% and 84.1% (95% confidence interval: 84.4-97.3%, 77.9-93.8% and 73.9-91.2%), respectively, by per protocol analysis (P=0.088). All regimens were well tolerated and compliance was excellent. CONCLUSIONS: Both low-dose clarithromycin triple therapy and tinidazole-containing triple therapy are effective and safe regimens for H. pylori eradication.

Adult↗

PubMed2002

Effect of Helicobacter pylori eradication on duodenal ulcer scar in patients with no clinical history of duodenal ulcer.

BACKGROUND: Helicobacter pylori eradication has become the standard treatment for duodenal ulcer. However, there is no relevant evidence for antibacterial treatment of the white scar stage of duodenal ulcer (duodenal ulcer scar) in patients with no past history of duodenal ulcer. AIM: To investigate whether H. pylori eradication could decrease duodenal ulcer recurrence in patients with duodenal ulcer scar and no past history of duodenal ulcer. PATIENTS AND METHODS: We prospectively enrolled 66 patients with duodenal ulcer scar: 53 were H. pylori-positive and 13 were H. pylori-negative. H. pylori-positive patients were randomly assigned into two groups (two-to-one allocation): 36 patients were assigned to the treatment group and 17 to the follow-up group. Thirteen H. pylori-negative patients were followed up according to the study protocol. Follow-up endoscopy was performed to evaluate ulcer scar changes and H. pylori status 6 weeks after anti-H. pylori treatment and then every 6 months for up to 30 months. RESULTS: Active duodenal ulcer recurrence was identified in seven of 23 H. pylori-positive/non-cured patients (30%). There was no duodenal ulcer recurrence in 43 H. pylori-negative/cured patients (0%), which was significantly different in terms of duodenal ulcer recurrence (P=0.001). CONCLUSIONS: H. pylori eradication is effective at preventing active duodenal ulcer recurrence in patients with duodenal ulcer scar and no past history of duodenal ulcer.

Amoxicillin↗

PubMed2001

Relation of apolipoprotein E polymorphism to clinically diagnosed Alzheimer's disease in the Korean population.

The gene for human apolipoprotein E (APOE) is found on the long arm of chromosome 19 (19q13.2) and exists in three common allelic forms, epsilon2, epsilon3, and epsilon4. The APOE epsilon4 allele is overrepresented in Alzheimer's disease (AD) and is accepted as a genetic risk factor. Some studies reported a protective effect of the APOE epsilon2 allele for AD. However, there are some ethnic variations in the proportion of different APOE alleles and their relationship to AD. We examine the distribution of APOE alleles from 30 AD patients and 158 controls in Korea. The control subjects were all cognitively intact unrelated Koreans. The frequencies of APOE alleles in AD patients were 18.3% (epsilon2), 58.3% (epsilon3), and 23.3% (epsilon4). The corresponding frequencies in controls were 13.3% (epsilon2), 72.5% (epsilon3), and 14.2% (epsilon4). The frequency of the APOE epsilon2 allele in AD patients was not significantly different from that in controls. When statistical analysis was conducted after the exclusion of the APOE epsilon2 allele, the frequency of the APOE epsilon4 allele in AD patients was significantly higher than that in controls (P < 0.05). These results support that the APOE epsilon4 allele plays a role as a risk factor for AD in Koreans and suggest that the APOE epsilon2 allele may not play a protective role in the development of AD in Koreans.

Adult↗

PubMed2001

An analysis of 4,514 cases of renal biopsy in Korea.

To evaluate the distribution and changing patterns of renal diseases in Korea, a total of 4,514 cases of renal biopsy collected over a 23-year period between 1973 and 1995 were reviewed. Of 4,200 cases excluding 314 unsatisfactory biopsies, adult cases comprised 59.5% and pediatric cases, 40.5%. The male to female ratio was 1.5:1 in adults and 2.2:1 in children. Glomerulonephritis (GN) comprised 80.0% of the total. The most common primary GN in adults was minimal change disease (MCD) (26.6%), followed by IgA nephropathy (IgAN) (22.1%), membranous GN (MGN) (11.8%), and membranoproliferative GN (MPGN) (5.9%). In children, the primary GN incidence rates were MCD (24.8%), IgAN (10.3%), poststreptococcal (including postinfectious) GN (PSGN) (8.6%), and focal segmental glomerulosclerosis (FSGS) (4.0%). The most common secondary GN in adults was lupus nephritis and in children Henoch-Schonlein purpura nephritis. The most common cause of nephrotic syndrome was MCD in both adults and children, followed by MGN and FSGS. The elderly, aged sixty years and older, comprised 2.7% of cases and recorded equal numbers of MCD and MGN. The proportion of the biopsies found to be seropositive for HBs antigen was 27.9%, and these showed either MGN or MPGN pattern. Repeat biopsy was performed in 168 patients, due to previous biopsy failure in 15.5%. When the primary GN cases were analyzed at 5-year intervals, the prevalence of PSGN, which was greater than 25% during the 1973-1982 period, decreased abruptly in children thereafter, whereas the prevalence of FSGS increased slowly since the 1988-1992 period in both adults and children. The decrease of PSGN and the increase of FSGS suggest a role for socioeconomic and environmental factors in Korea.

Adult↗

PubMed2001

Glomerular growth under cyclosporine treatment in childhood nephrotic syndrome.

BACKGROUND: Glomerular hypertrophy is important in children with idiopathic nephrotic syndrome in regard to diagnosis and pathogenesis. Moreover, glomerular growth may be altered by cyclosporine (CsA) treatment in these patients. METHODS: Bowman's area (BA) and the glomerular tuft area (GA) of pre- and post-treatment biopsies was measured by morphometry in 47 children with idiopathic nephrotic syndrome (39 MCD and 8 FSGS) treated with CsA and low-dose prednisolone for up to 2 years. RESULTS: BA and GA increased with age. The mean BA and GA were 1.2 times larger in FSGS than in MCD and the proportional increase was similar in both diseases after treatment. BA and GA decreased in 48.9% and 40.4% of cases after treatment, respectively, whereas tubulointerstitial lesion (TIL) developed in 27.7%. BA and GA decreased to 10.4% and 8.3%, respectively in children who developed TIL after treatment and the values were largely unchanged in those treated for more than 16 months. CONCLUSIONS: Glomerular growth is hampered by CsA nephrotoxicity, which is a more common complication than TIL. The impairment of glomerular growth is related to the duration of treatment and the development of TIL, but not to age or diagnosis.

Child↗

PubMed2000

Long-term clinical course and prognostic factors in intestinal Behçet's disease.

PURPOSE: The present study was aimed at evaluating the long-term course of intestinal Behçet's disease and determining predictive factors of prognosis. METHODS: This report is a retrospective study based on the records of 43 patients with intestinal Behçet's disease. The mean follow-up duration was 73 +/- 60 months. We evaluated the efficacy of medical treatment for the intestinal lesion at initial eight weeks. The cumulative probabilities were calculated by using Kaplan-Meier method, and the results were compared by using the log-rank test. RESULTS: Sixteen patients (38 percent) achieved a complete remission of intestinal lesions eight weeks after medical treatment had begun. The patients who achieved a complete remission had a lower probability of receiving an operation than those who had not (13 percent at 2 and 5 years vs. 36 and 43 percent, respectively; P = 0.028). The recurrence probability of intestinal lesions was 25 percent at two years and 49 percent at five years after complete remission with medical treatment. Patients who had a history of intestinal perforation or fistula had a higher probability of recurrence after operation than those without such history (59 vs. 33 percent at 2 years; 88 vs. 57 percent at 5 years; P = 0.020). Patients who had taken azathioprine had a lower probability of receiving reoperation than those who did not (7 vs. 25 percent at 2 years; 25 vs. 47 percent at 5 years; P = 0.035). The length of ileal resection and whether hemicolectomy was performed had no significant effect on the recurrence or reoperation rate. CONCLUSIONS: Intestinal Behçet's disease frequently requires a surgical treatment and has a high recurrence rate. The patients who achieved a complete remission with medical treatment, who had no history of intestinal perforation, and who received azathioprine after operation showed better clinical courses. Resection of a short segment of bowel would be a more appropriate surgical procedure.

Adolescent↗

PubMed2000

One-allele system in the Korean for MboI-RFLP in exon 1 of the human tyrosinase (TYR) gene.

Oculocutaneous albinism is an autosomal recessive genetic disorder. Several types of oculocutaneous albinism are caused by mutation in related genes. Oculocutaneous albinism 1 is associated with the tyrosinase gene. The human tyrosinase gene (TYR) encodes tyrosinase, a key enzyme in melanin biosynthesis. As exon 1 of the gene shows an MboI-RFLP within codon 192 in Caucasians, we studied allele frequencies of MboI 192 polymorphism in 200 chromosomes from 100 unrelated normal Korean individuals. As a result, only one allele system, the presence of the MboI 192 site, was detected in the Korean.

Albinism, Oculocutaneous↗

PubMed2000

Analysis of cathepsin D in human breast cancer: usefulness of the processed 31 kDa active form of the enzyme as a prognostic indicator in node-negative and node-positive patients.

The relative amounts of the precursor (52 kDa) and processed (31,27 kDa) forms of cathepsin D have been analyzed by Western blotting in biopsied breast tissue cytosols from 134 lesions from invasive breast cancer patients, 24 lesions from patients with ductal carcinoma in situ (DCIS), 227 lesions from benign breast disease patients, and 28 lesions from normal control subjects. The mean relative percentage amount of the 31 kDa form was significantly increased (p < 0.001) in the invasive breast cancer group compared to the other three groups. In addition, the mean relative percentage amount of the 31 kDa form was significantly increased (p < 0.05) in node-positive compared to node-negative breast cancer patients. In the benign breast disease group, patients with proliferative-type disease had a significantly increased (p = 0.02) mean relative percentage amount of the 31 kDa form of cathepsin D compared to patients with nonproliferative-type disease. Invasive breast cancer patients were followed for up to 75 months to determine if the relative percentage amount of the 31 kDa form of cathepsin D was predictive of disease-free and overall survival. Although the amount of the 31 kDa form was not predictive of disease-free survival, patients in the 'high' 31 kDa group (> 18%) were significantly (p < 0.05) more likely to die than patients in the 'low' 31 kDa group (< or = 18%). The 12 patients who died were all node-positive and in the high 31 kDa group. It thus appears that the relative amount of the processed, active 31 kDa form of cathepsin D is a useful prognostic indicator, at least in node-positive breast cancer patients.

Adult↗

PubMed2000

Prediction of the clinical course of Behçet's colitis according to macroscopic classification by colonoscopy.

BACKGROUND AND STUDY AIMS: The lesions in Behçet's colitis show aphthoid or punched-out ulceration, but the macroscopic types of lesion found have not been defined. To predict the clinical outcome in patients with Behçet's colitis according to the colonoscopic findings, we classified the characteristic colonic ulcers, evaluated the efficacy of medical treatment on colonoscopic lesions, and calculated the operation rates and recurrence rates relative to the macroscopic types. PATIENTS AND METHODS: The medical records and colonoscopic photographs of 50 patients with Behçet's colitis were reviewed. The colonic lesions were examined by colonoscopy in patients with Behçet's disease and gastrointestinal symptoms. The colonoscopic findings were categorized into three types of ulceration: volcano-like, geographic, and aphthous. The efficacy of medical treatment was assessed by follow-up colonoscopy or double-contrast barium enema four to eight weeks after treatment, and recurrence of the lesions was evaluated during the follow-up periods. Cumulative surgery rates were obtained using the Kaplan-Meier method. RESULTS: The macroscopic classification of colonic ulcers identified 25 of 50 patients (50%) with volcano-type lesions, 11 (22%) with the geographic type, and 14 (28%) with the aphthous type. The rates of complete remission after medical treatment and surgery, respectively, were six of 25 (24%) and 13 of 25 (52%) with volcano-type ulcerations; eight of 11 (73%) and one of 11 (9%) with the geographic type; and nine of 14 (64%) and two of 14 (14%) with the aphthous type. The endoscopic and clinical recurrence rates were nine of 19 (47%) in volcano-type ulcerations, one of nine (11%) in the geographic type, and one of 11 (9%) in the aphthous type. CONCLUSION: Volcano-type ulcerations in Behçet's colitis showed a less favorable response to medical treatment, a more frequent requirement for surgery, and more frequent recurrences than the geographic and aphthous types of ulcerations.

Adult↗

PubMed1997

The safety and efficacy of transcatheter arterial chemoembolization in the treatment of patients with hepatocellular carcinoma and main portal vein obstruction. A prospective controlled study.

BACKGROUND: Transcatheter arterial chemoembolization (TACE) has been contra-indicated for the treatment of patients with hepatocellular carcinoma (HCC) and main portal vein (MPV) obstruction because of the potential risk of hepatic insufficiency resulting from ischemia after TACE. The current controlled study was undertaken to assess the safety, efficacy, and predictive factors of favorable response to TACE in patients with HCC and MPV obstruction with good hepatic function and adequate collateral circulation around the MPV. METHODS: Of a total of 47 patients, 31 were treated with TACE, and 16 who declined the procedures were untreated controls. Thirty-six patients (77%) had diffuse-type HCC and 11 (23%) had nodular-type HCC. During the first week after TACE immediate postprocedural complications were evaluated, and the development of hepatic insufficiency as a late complication was assessed at the end of the fourth week. The cumulative survival rate was estimated by the Kaplan-Meier method, and predictors of better prognosis were obtained by univariate and multivariate analyses. RESULTS: Although no patients showed clinical evidence of hepatic insufficiency as an immediate complication, transient fever and abdominal pain were common. Progressive hepatic insufficiency developed at the fourth week; however, there was no difference between the treated and untreated groups. The survival time of treated patients was statistically no longer than that of untreated patients. In the univariate analysis, tumor type and size, the pattern of iodized oil uptake in the tumor, and the presence of iodized oil uptake in the tumor thrombi at the MPV significantly influenced the prognosis. Tumor type, whether treated or not, was the most important prognostic factor patients with nodular-type HCC had significantly longer survival time (median, 11 months) than those with diffuse-type HCC (median, 4 months). Regarding the efficacy of TACE, there was no statistical difference in survival between treated and untreated diffuse-type HCC patients. In comparison, with nodular-type HCC it seemed that survival time was longer for TACE-treated patients (median, 30 months) than for untreated patients (median, 7 months). CONCLUSIONS: TACE may be a safe modality for the treatment of patients with HCC and MPV obstruction, provided that the patients have good hepatic function and collateral circulation around the MPV. However, TACE was not efficacious in the treatment of diffuse-type HCC. The authors recommend TACE for treating nodular-type HCC because of the potential benefit of prolonged survival.

Adult↗