Biomedical subjects

D S Ahn

Publications and source records attributed to D S Ahn.

At least 19 recordsLinked to original sources

PubMed2006

Differential cross section and photon-beam asymmetry for the gamma n --> K+ Sigma- reaction at E gamma = 1.5-2.4 GeV.

Differential cross sections and photon-beam asymmetries have been measured for the gamma n --> K+ Sigma- and gamma p --> K+Sigma0 reactions separately using liquid deuterium and hydrogen targets with incident linearly polarized photon beams of E gamma = 1.5-2.4 GeV at 0.6 < cos ThetacmK< 1. The cross section ratio of sigma K+ Sigma-/sigma K+ Sigma0, expected to be 2 on the basis of the isospin 1/2 exchange, is found to be close to 1. For the K+ Sigma- reaction, large positive asymmetries are observed, indicating the dominance of K* exchange. The large difference between the asymmetries for the K+ Sigma- and K+ Sigma0 reactions cannot be explained by simple theoretical considerations based on Regge model calculations.

Journal Article↗

PubMed2005

Near-threshold diffractive psi-meson photoproduction from the proton.

Photoproduction of a phi meson on protons was studied by means of linearly polarized photons at forward angles in the low-energy region from threshold to Egamma = 2.37 GeV. The differential cross sections at t = -|t|min do not increase smoothly as Egamma increases but show a local maximum at around 2.0 GeV. The angular distributions demonstrate that phi mesons are photoproduced predominantly by helicity-conserving processes, and the local maximum is not likely due to unnatural-parity processes.

Journal Article↗

PubMed2005

Comparison of evidence-based therapeutic intervention between community- and hospital-based primary care clinics.

The purpose of this study was to compare the proportion of therapeutic interventions that is supported by scientific evidence between hospital-based and community-based primary care clinics. The study setting is a primary care clinic in university-affiliated tertiary hospital and community-based primary care clinic in a region in Seoul. A retrospective review of patients' medical records was done according to the primary diagnosis and treatment for 890 patients in community-based clinic and 307 in hospital-based clinic. The evidence for the intervention was searched for in Medline (1966-2001) and other evidence-based databases. The evidence was then classified as one of the three categories (i) evidence from randomised controlled trials (RCTs); (ii) convincing non-experimental evidence; and (iii) interventions without substantial evidence. In the hospital-based clinics, out of 356 primary diagnosis and treatment pairs, 59.6% were supported by evidence from at least one RCTs, and 19.4% were supported by convincing non-experimental evidence. In the community-based clinics, 47.1% out of 893 pairs and 10.5% fell into each category. As a result, the proportion of interventions in community settings that were based on evidence meeting our criteria was significantly lower than that of the hospital-based settings. To facilitate evidence-based practice, supportive activity should be focused on the primary care settings based on community where medical practices are less evidence-based.

Ambulatory Care↗

PubMed2003

Beam-polarization asymmetries for the p(gamma-->, K+)Lambda and p(gamma-->, K+)Sigma(0) reactions for E(gamma)=1.5-2.4 GeV.

Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured for the first time for E(gamma)=1.5-2.4 GeV and 0.6<cos((theta(c.m.)(K+))<1.0 by using linearly polarized photons at the Laser-Electron-Photon facility at SPring-8 (LEPS). The observed asymmetries are positive and gradually increase with rising photon energy. The data are not consistent with theoretical predictions based on tree-level effective-Lagrangian approaches. Including the new results in the development of the models is, therefore, crucial for understanding the reaction mechanism and to test the presence of baryon resonances which are predicted in quark models but are thus far undiscovered.

Journal Article↗

PubMed2003

Evidence for a narrow S = +1 baryon resonance in photoproduction from the neutron.

The gamman-->K(+)K(-)n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed at 1.54+/-0.01 GeV/c(2) with a width smaller than 25 MeV/c(2) and a Gaussian significance of 4.6sigma. The strangeness quantum number (S) of the baryon resonance is +1. It can be interpreted as a molecular meson-baryon resonance or alternatively as an exotic five-quark state (uuddsmacr;) that decays into a K+ and a neutron. The resonance is consistent with the lowest member of an antidecuplet of baryons predicted by the chiral soliton model.

Journal Article↗

PubMed2002

Primary antiphospholipid syndrome presenting with abdominal angina and splenic infarction.

The antiphospholipid syndrome is an autoimmune hypercoagulability syndrome in which a wide variety of thromboembolic diseases may occur. Gastrointestinal manifestations associated with vascular occlusion include Budd-Chiari syndrome, hepatic and splenic infarction, pancreatitis, omental and intestinal infarction, and esophageal variceal bleeding due to portal vein thrombosis, but chronic mesenteric ischemia associated with mesenteric arterial thrombosis is very rare in this syndrome. We experienced a female patient with primary antiphospholipid syndrome with abdominal angina and splenic infarction associated with celiac trunk and mesenteric arterial thromboses. This is the first report describing chronic mesenteric ischemia and splenic infarction in a patient with primary antiphospholipid syndrome.

Abdominal Pain↗

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↗

PubMed2001

Hand elevation: a new test for carpal tunnel syndrome.

Hand elevation can reproduce the symptoms of carpal tunnel syndrome. This phenomenon prompted the idea of developing a simple hand elevation test to diagnose carpal tunnel syndrome. A total of 200 hands in 118 patients diagnosed with carpal tunnel syndrome were tested prospectively from September 6, 1999, to February 3, 2000. Three provocative tests (hand elevation test, Phalen's test, and Tinel's test) were performed on each hand for both the experimental group (200 hands) and the control group (200 hands). McNemar chi-squared analysis was used to compare the sensitivity and specificity of the new hand elevation test with those of Phalen's test and Tinel's test. The sensitivity and specificity of the hand elevation test is 75.5% and 98.5% respectively. Phalen's test had 67.5% sensitivity and 91.0% specificity. Tinel's test had 67.5% sensitivity and 90.0% specificity. The difference in sensitivities between the hand elevation test and Phalen's test was significant (p = 0.05). No significant difference was found in the sensitivity between the hand elevation test and Tinel's test. The comparison of specificity of the hand elevation test and Phalen's test was significant (p = 0.001). Significance was also observed in specificity between the hand elevation test and Tinel's test (p = 0.001). In this study, the sensitivity and specificity of the elevation test were higher than those of Phalen's test and Tinel's test. Statistical analysis confirms the eligibility of the hand elevation test as a useful, provocative test.

Adult↗

PubMed2001

The outcome of the nonoperated contralateral hand in carpal tunnel syndrome.

It is not well known how the nonoperated contralateral hand behaves in bilateral carpal tunnel syndrome (CTS). The postoperative clinical course of the nonoperated contralateral hand in unilateral CTS is not well documented either. Of 324 CTS patients, the authors studied 37 who had carpal tunnel release on one hand only to evaluate the postoperative outcome of the nonoperated contralateral hand. The other 287 patients had operations on both hands. Seven patients were excluded because of missing data or because they could not be contacted. All 324 patients were subject to clinical and electrodiagnostic studies on both hands. The patients were divided into three groups. Group I was composed of patients who had bilateral CTS, diagnosed clinically and electrophysiologically, but who had surgery done only on the hand with the most pronounced symptoms. The patients in group II showed symptoms of CTS in one hand only. However, the opposite hand was diagnosed with subclinical CTS: Electrodiagnostic studies showed involvement of the median nerve, but without symptoms. Group III was composed of true unilateral CTS patients, diagnosed by symptoms and electrodiagnostic study. The results of the electrodiagnosis were categorized according to the severity of median nerve damage (mild, moderate, severe). The outcome and postoperative clinical course of the nonoperated contralateral hand were evaluated by electromyography and telephone survey. This method of survey was used because of the vast spread of patients throughout the country. Within 1 year, all 30 operated hands showed significant improvement, 20 of which belonged to group I. Regarding progress of the nonoperated contralateral hand, 10 patients showed improvement of one grade whereas 5 patients showed three grades of improvement. In another 5 patients there was no change whatsoever. In addition, from groups II and III there were 5 patients who showed no change in the nonoperated hand. The postoperative electromyographic findings of the nonoperated contralateral hand was not commensurate with the symptoms. However, regardless of electromyographic results, the nonoperated contralateral hand showed significant improvement (p < 0.0001). Patients with unilateral CTS did not experience any symptom development in the nonoperated contralateral hand.

Adult↗

PubMed2000

A prospective study of the anatomic variations of the median nerve in the carpal tunnel in Asians.

A prospective study of anatomic variations of the median nerve and its relationship to the surrounding structures was performed of 354 consecutive operations in 192 patients with carpal tunnel syndrome at Korea University Anam Hospital from July 1995 to September 1997. A total of 184 patients were women and 8 patients were men. A total of 162 patients were bilateral and 30 were unilateral. Regarding the course of the motor branch, the extraligamentous type was most common (96.1%, 340 patients). A total of 81.1% of patients (N = 287) had the origin of the motor branch at the radial side of the median nerve (or radial one third), and 17.2% of patients (N = 61) had the origin of the motor branch at the anterior portion of the median nerve. Of these 61 patients, 30 patients (49.1%) were of the preligamentous type. Only one motor nerve branch was found in 89.5% of patients (N = 317), and multiple branches were found in 10.5% of patients. As a result of the comparison between two hands when both hands were operated, the origin and number of motor branches and their courses were identical in most patients (>60%). Hypertrophy of the flexor pollicis brevis was found in 8.5% of patients (N = 30), hypertrophy of the palmaris brevis was found in 4.2% of patients (N = 15), absence of the palmaris longus was discovered in 0.6% of patients (N = 2), existence of the median artery was found in 0.6% of patients (N = 2), and high division of the median nerve rejoining with the thenar motor nerve was found in 0.3% of patients (N = 1). Clearly, the anatomy of the carpal tunnel in Koreans is somewhat different, in part, from the results obtained from studies of whites, but overall results are not significantly different. These results can help obtain a better surgical outcome and complete decompression of the median nerve during operation while preventing inappropriate or inadvertent injury to the motor branch of the median nerve in Koreans.

Adult↗

PubMed2000

Membrane stretch increases the activity of Ca(2+)-activated K+ channels in rabbit coronary vascular smooth muscles.

It has been proposed that Ca(2+)-activated K+ channels play an essential role in maintaining vascular tone during stretch of blood vessel. However, the underlying mechanism of stretch-induced change of Ca(2+)-activated K+ channel activities are still unknown. The present experiment was designed to investigate the effect of membrane stretch on these channels whose activity was measured from rabbit coronary smooth muscle cells using a patch clamp technique. Ca(2+)-activated K+ channel were identified by their Ca2+ and voltage dependencies and its large conductances as in other preparations. Perfusion of cells with a hypotonic solution, which mimics stretching the cell membrane by making a cell swelling, produced an increase in channel activity in cell-attached patch mode. The similar increase was observed when negative pressure was applied into the patch pipette for stretching the cell membrane within a patch area. In inside-out patch, stretch still increased channel activity even under the conditions which exclude the possible involvement of secondary messengers, or of transmembrane Ca2+ influx via stretch-activated cation channels. Pretreatment of arachidonic acid or albumin showed no effect on stretch-induced channel activation, excluding the possibility of fatty acids mediated channel activation during membrane stretch. These results indicate that the stretch may directly increase the activity of Ca(2+)-activated K+ channels in our experimental condition.

Animals↗

PubMed2000

Sulfhydryl modification affects coronary artery tension by changing activity of delayed rectifier K+ current.

It has been reported that a change in the cellular redox state may be involved in the regulation of vascular tone, but the underlying mechanism is not fully understood. The present study was designed to investigate the cellular effect of sulfhydryl modifying agents in the coronary artery of rabbit using the tension measurement and whole cell clamping method. The application of diamide, a sulfhydryl oxidizing agent, relaxed the endothelium denuded coronary arteries in a dose dependent manner. The fact that this diamide-induced relaxation was significantly attenuated by a pretreatment of 4-AP, and the coronary arteries precontracted with 100 mM K+ instead of histamine, suggests the involvement of 4-AP sensitive K+ channels in the diamide-induced relaxation of coronary arteries. Whole cell patch clamp studies revealed that the 4-AP sensitive IdK was significantly enhanced by the membrane permeant oxidizing agents, diamide and DTDP, and were reversed by subsequent exposure to the reducing agent, DTT. Neither the membrane impermeant oxidizing or reducing agents, GSSG or GSH, had any effect on the activity of IdK, indicating that intracellular sulfhydryl modification is critical for modulating IdK activity. The Diamide failed to significantly alter the voltage dependence of the activation and inactivation parameters, and did not change the inactivation process, suggesting that diamide increases the number of functional channels without altering their gating properties. Since IdK has been believed to play an important role in regulating membrane potential and arterial tone, our results about the effect of sulfhydryl modifying agents on coronary arterial tone and IdK activity should help understand the pathophysiology of the diseases, where oxidative damage has been implicated.

Animals↗

PubMed1999

Down-regulation of insulin-like growth factor binding proteins and growth modulation in hepatoma cells by retinoic acid.

We observed that all-trans-retinoic acid (RA) down-regulated insulin-like growth factor binding proteins (IGFBPs) in cultured human hepatoma cells (Hep 3B, PLC/PRF/5, and Hep G2); therefore, we characterized the role of this down-regulation in cell growth. Treatment with 10 micromol/L RA revealed a rapid decrease in IGFBP-3 within 2 days, and continued treatment with RA for 6 days resulted in a time-dependent stimulation of Hep 3B cell growth. However, RA treatment decreased IGFBP-1 in PLC/PRF/5 cells and in Hep G2 cells, and the growth-stimulatory activity of RA was transient and less prominent, and was finally obliterated in both cell lines. The addition of 5 ng/mL or 50 ng/mL insulin-like growth factors (IGFs) did not change the growth effects elicited by RA. The addition of IGFBP-3 (1,000 ng/mL) inhibited the growth of Hep 3B cells and counteracted the growth-stimulatory activity of RA, but not completely, suggesting that RA has direct growth-stimulatory activity and that this is enhanced by autocrine down-regulation of IGFBP-3. IGFBP-3 also inhibited the growth of PLC/PRF/5 cells and of Hep G2 cells. Treatment with phosphorylated IGFBP-1 (1,000 ng/mL) alone or with RA did not affect the growth of PLC/PRF/5 cells or Hep G2 cells. However, addition of dephosphorylated IGFBP-1, derived from in vivo dephosphorylation of the phosphorylated form, stimulated the growth of both cell lines, independent of interaction with IGF-I. From these observations, we propose that RA down-regulates IGFBPs, which in turn causes autocrine modulation of cell growth independent of IGF in hepatoma cells in vitro or in vivo. In addition, RA regulates IGFBPs at the posttranscriptional (Hep 3B cells and Hep G2 cells) or transcriptional level (PLC/PRF/5 cells) in a cell-specific manner.

Carcinoma, Hepatocellular↗

PubMed1999

Report of phenol peel for Asians.

With the advancement of trichloroacetic acid peel technology and wound care, trichloroacetic acid peeling has become very successful in Korea. Its success has opened studies on the possibility of using phenol on Korean skin. Dr. Mee's phenol formula (molding mask technique) was chosen for experiments on Korean skin because of the presumed safety of use on non-Caucasian skin. Between January of 1996 and January of 1998, 30 cases of significant small pox scars were treated with phenol at the Korea University Anam Hospital. The age range was from 43 to 60 years, with a mean of 49 years. The average follow-up period was 13 months, ranging from 1 month to 2 years. All of the procedures were performed in the operating room while the patient was under deep i.v. sedation. After the entire face was peeled, it was covered with an occlusive tape mask. During the recovery period, the patients underwent a post-peel skin care program. All 30 patients showed significant improvement of the severe pox marks with a marked rejuvenation effect. There was no sign of hypopigmentation or hyperpigmentation. As a complication, two patients developed hypertrophic scars on the perioral area, which responded well to steroid injections. Another pair of patients had herpetic infection, which left minimal scarring. Five patients developed cardiac arrhythmia with this rapid technique, but this was safely managed by an anesthesiologist during the procedure. Korean skin belongs to Fitzpatrick types IV and V and occasionally to type III or VI. It is common knowledge that performing chemical peeling on the latter types of skin is dangerous, but in this report, excellent results were obtained from all 30 patients, even though the peeling itself was very deep. With more knowledge and experience, phenol peel can be safely conducted on Asian skin.

Adult↗

PubMed1999

Facial resurfacing in xeroderma pigmentosum with chemical peeling.

We describe our experience with two patients with xeroderma pigmentosum who underwent multiple trichloroacetic acid chemical peels. Trichloroacetic acid and phenol were used in one case. Until now numerous treatment modalities have been reported. Deep chemical peeling has not been reported before in patients with xeroderma pigmentosum. Chemical peeling is a simple procedure with less associated morbidity.

Adult↗

PubMed1998

Correlation of clinical history and electrodiagnostic abnormalities with outcome after surgery for carpal tunnel syndrome.

A retrospective study on 294 wrists in 154 patients who had been diagnosed with carpal tunnel syndrome and subsequently had surgery performed was undertaken; both clinical and electrodiagnostic findings were correlated. The cases were divided into three groups based on electromyographic severity (mild, moderate, severe), and recovery from symptoms was evaluated after 1 week, 3 months, and 1 year. The cases were also divided into five groups based on symptom duration, and the same investigations were performed. All operations were conducted by applying the open release method with the limited-palmar incision technique. Operative outcomes showed no association between recovery from symptoms and the severity of electromyographic findings or the duration of symptoms, although the group that had the shortest duration of symptoms recovered faster than the long-duration groups statistically. Postoperative results after 1 year were also successful for those patients who had had symptoms of long duration. Of the 294 wrist operations studied, good to excellent postoperative outcomes were recorded in 242 cases (82 percent), fair outcomes in 39 cases (13 percent), and poor outcomes in 13 cases (4 percent). Patients whose electromyogram revealed double crush syndrome still showed improvement, with good-to-excellent results in 11 out of 15 cases (73 percent). Patients with diabetes mellitus also showed improvement, with good-to-excellent results in 14 out of 19 patients (74 percent). This study showed that postoperative results were satisfactory within 1 year, regardless of the degree of electromyographic severity, symptom duration, presence of diabetes mellitus, or double crush syndrome.

Adult↗

PubMed1997

pH regulation of voltage-dependent K+ channels in canine pulmonary arterial smooth muscle cells.

Voltage-dependent K+ currents (Kv) may play a role in hypoxic pulmonary vaso constriction. The effects of changes in extracellular pH (pHo) and intracellular pH (pHi) on Kv currents in smooth muscle cells isolated from canine pulmonary artery were studied using the amphotericin B perforated-patch technique for whole-cell recording. Under these conditions, cellular mechanisms for pHi regulation remain intact, and the effects of pHo were examined by directly changing the pH of external solutions and changes in pHi were produced by external application of weak extracellular acids and bases and the cation/H+ ionophore, nigericin. Ca(2+)-free external solutions were used to isolate whole-cell Kv currents from contaminating Ca(2+)-activated K+ currents. Extracellular acidification (pHo = 6.4-7.0) reduced Kv currents, produced a positive voltage shift in steady-state activation and reduced maximum Kv conductance (gK). Extracellular alkalinization (pHo = 8.0-8.4) increased Kv currents, produced a small negative voltage shift in steady-state activation, and increased gK. Intracellular acidification produced by exposure of cells to external sodium butyrate (20 mM) or nigericin (5 micrograms/ml) increased Kv currents, produced a negative voltage shift in steady-state activation, and increased gK. Intracellular alkalinization produced by exposure of cells to external trimethylamine (20 mM) reduced Kv currents, produced a small positive voltage shift in steady-state activation and reduced gK. These results suggest that the effects of pHo and pHi on Kv currents are distinctly different, but are consistent with reported effects of pHo and pHi on hypoxic pulmonary vasoconstriction, suggesting that such modulation may be mediated in party by pH-induced alterations in Kv channel activity.

Amphotericin B↗

PubMed1997

Differences in immunophenotyping of mucosal lymphocytes between ulcerative colitis and Crohn's disease.

OBJECTIVES: Immunologic studies have characterized the numbers and types of inflammatory cells in diseased inflammatory bowel disease (IBD) mucosa but have yielded conflicting results regarding intestinal lymphocytes activation in IBD. We investigated the levels of lymphocytes subsets, interleukin-2 receptor, transferrin receptor, and T cell receptors in mainly isolated lamina propria lymphocytes. Including intraepithelial lymphocytes of normal colonic mucosa or IBD (ulcerative colitis and Crohn's disease) mucosa to understand the pathogenesis of IBD. We have results from this study. RESULTS: 1) In comparing ulcerative colitis with control, IL-2R (p < 0.05), TR (p < 0.01), and CD3/HLA-DR (< 0.05) showed a significant increase. 2) In comparing Crohn's disease with control, CD3 (P < 0.05), TCR alpha/beta (p < 0.01) and TCR gamma/delta (p < 0.05) showed a significant decrease. 3) In comparing Crohn's disease with ulcerative colitis, CD19 (p < 0.01), TR (p < 0.01), TCR alpha/beta (p < 0.01) and TCR gamma/delta (p < 0.05) showed a significant decrease. CONCLUSION: From these results, there are increased T cell markers, IL-2R, TR, and CD3/HLA-DR in UC, but differently, decreased CD3, TCR alpha/beta and TCR gamma/delta in CD compared with control. In addition, definitive differences in lymphocytes markers, CD19, TR, TCR alpha/beta and TCR gamma/delta, which are higher in UC than in CD, may elucidate the different immunopathogenesis between UC and CD.

Adult↗