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Biomedical subjects

Y S Choi

Publications and source records attributed to Y S Choi.

At least 73 records · Page 4Linked to original sources
PubMed1998

Effects of soluble dietary fibers on lipid metabolism and activities of intestinal disaccharidases in rats.

The present study was aimed to investigate the effects of indigestible dextrin and polydextrose, soluble dietary fibers with low molecular weight, on lipid metabolism and disaccharidase activities of intestinal mucosa in rats fed a high sucrose diet. Their effects were compared with those of well-known soluble fibers, pectin, and guar gum, and also with an insoluble fiber, cellulose. Dietary fibers added to diets at the 5% (w/w) level were alpha-cellulose, pectin, guar gum, indigestible dextrin, and polydextrose. Male Sprague-Dawley rats were given free access to test diets for 6 weeks. Body weight gain was the lowest in rats fed guar gum, the highest in rats fed cellulose, and in-between in rats fed other diets. Although guar gum, pectin, and indigestible feeding dextrin had lower plasma lipid values than cellulose feeding did, the differences were statistically insignificant. Liver triglyceride of the guar gum-fed group was about a third that of the cellulose-fed group, but although those of rats fed polydextrose, indigestible dextrin, and pectin were lower than that of cellulose, the differences were insignificant. Liver cholesterol and phospholipid concentrations were similar among groups. Daily fecal excretion of total lipid, cholesterol, and bile acids were highest in rats fed guar gum, followed by pectin-fed and cellulose-fed rats, and the lowest in rats fed indigestible dextrin and polydextrose. Jejunal sucrase activity was low in the order of guar-gum, polydextrose, indigestible dextrin, pectin, and cellulose. The results indicate that the hypolipidemic effect of soluble dietary fibers would be lessened with reduction in molecular weight, but that the lower sucrase activity by soluble fibers with low molecular weight might be beneficial for hypoglycemic effect.

Animals↗
PubMed1998

Study of user preference of graphic user interface in laboratory information system.

In order to elucidate employees satisfaction levels in using graphic user interface. (GUI) in a laboratory information system (LIS), users attitudes toward GUI versus CUI. (Character User Interface) in a similar LIS were surveyed one month after implementing upgraded version of LIS in a tertiary care university hospital laboratory. The outcome of the study showed that approximately two third of users preferred to have GUI in LIS. There was no difference in preference of GUI of users whether they had previous experience with GUI or not. However the female and older employees tend to shy away from GUI. The employee productivity was improved with GUI although it takes slightly longer program loading time than that of CUI. In conclusion, the laboratory employee satisfaction was higher with GUI than CUI and their productivity was improved with GUI.

Adult↗
PubMed1997

Identification and activation mechanism of the interleukin-4-induced nuclear factor binding to the CD23(b) promoter in human B lymphocytes.

CD23 is a B cell activation antigen involved in B cell proliferation and production of IgE, of which two isoforms are known. While CD23(a) is constitutively expressed in B cells, the expression of CD23(b) is specifically induced by interleukin-4 (IL-4) or selected mitogenic stimuli. We have previously shown that CD23(b) is a primary response gene rapidly activated by IL-4 in resting human B cells. We now report the identification of a nuclear factor binding to the IL-4-response element (IL-4RE) in CD23(b) promoter in purified human tonsillar B cells. Activation of this factor, named NF-IL-4/CD23, occurred within 5 min after IL-4 treatment in a cycloheximide-insensitive manner. The activation was sensitive to phosphatases and inhibitors of protein tyrosine kinases, but it was not sensitive to inhibitors of protein kinase C. This behavior, in fact, closely correlates with the IL-4-induced activation mechanism of CD23 gene expression. In transformed B cell line Raji, where the IL-4-induced CD23 mRNA expression was hardly detected, no activation of NF-IL-4/CD23 was noted. The activation was also observed that although a sequence highly homologous to the IL-4RE of the CD23(b) promoter is present in the CD23(a) promoter, the IL-4-induced factor did not bind the sequence. These results strongly suggest that NF-IL-4/CD23 acts as an IL-4 signal transducer leading to CD23(b) gene activation in human B cells. Further characterization of this factor is now in progress, including comparison with STAT6, recently shown to be involved in IL-4 signal transduction and transcriptional activation.

B-Lymphocytes↗
PubMed1997

The functional role of B cell antigen receptor stimulation and IL-4 in the generation of human memory B cells from germinal center B cells.

The germinal center (GC) is an anatomical site where memory B cells are generated. Ag-Ab complexes presented by follicular dendritic cells in GC select precursors of memory B cells. Using a unique in vitro experimental system in which the survival of GC B cells is supported by a defined follicular dendritic cell-like cell line, we investigated the effects of B cell Ag receptor (BCR) stimulation and IL-4 on the memory B cell generation from centroblasts. IL-4 is reported to be critical for GC formation. Centroblasts differentiated to centrocytes during the culture period of 3 days as demonstrated by the down-regulation of CD77 expression and induction of CD44 as well as Bcl-2 expression. The transition of centroblast to centrocyte was enhanced by BCR stimulation and IL-4. Upon further culture, the centrocytes differentiated to memory B cells, a process that was enhanced by BCR stimulation and IL-4. The presence of IL-4 in the culture did not increase the number of plasma cells. These experimental data provide formal in vitro evidence that Ags in GC may participate not only in the selection but also in the expansion of memory B cells and that IL-4 is a growth factor promoting this expansion.

ADP-ribosyl Cyclase↗
PubMed1997

The apoptosis and proliferation of SAC-activated B cells by IL-10 are associated with changes in Bcl-2, Bcl-xL, and Mcl-1 expression.

Interleukin-10 (IL-10), a cytokine from mouse Th2 cells and macrophage that inhibits IL-2 and IFN-gamma production by Th1 cells, has been reported to stimulate growth and differentiation of B cells activated by CD40 or antigen receptor crosslinking. Our early observation revealed that IL-10 had B cell growth factor (BCGF) activity in human B cells preactivated with SAC or anti-Ig. The responsiveness of the preactivated B cells to IL-10 greatly increased when B cells were activated in the presence of IL-2, whereas IL-10 has no BCGF activity when added at the initiation of activation by SAC. To investigate the dual effects (proliferation and apoptosis) of IL-10 on B cells, the expression of a panel of bcl-2 protoncogene family members, bcl-2, bcl-x, mcl-1, and bax, was analyzed when B cells were activated by SAC. Bcl-xL protein was not expressed in the small resting B cells but was induced by SAC stimulation, reaching its peak at 48 hr. The addition of IL-2 further augmented the Bcl-xL expression with the same kinetics, whereas Bcl-2 and Mcl-1 were expressed by resting B cells and enhanced by SAC stimulation. However, the addition of IL-10 at the initiation of activation down-regulated Bcl-xL, Bcl-2, and Mcl-1 expression. At the same time, B cell proliferation was inhibited and apoptotic cell number increased, suggesting the growth arrest and/or apoptosis of B cells. The apoptosis of SAC-activated B cells by IL-10 was further confirmed by propidium iodide-staining and Annexin V-FITC-staining methods. In contrast, IL-10 failed to down-regulate the Bcl-xL and Bcl-2 expression but rather augmented the expression of Mcl-1 of B cells after preactivation for 48 hr with SAC and IL-2. Under this culture condition, B cells responded to IL-10 to proliferate and differentiate, while IL-2 and IL-10 had an additive or synergistic effect. Taken together, our data suggest that IL-10 acts on the induction stage of Bcl-xL expression and regulates the apoptosis and proliferation of SAC-activated B cells through their bcl-2 family gene expression.

Animals↗
PubMed1997

Considerations for toxicology studies of respiratory drug products.

The standard approaches for the preclinical development of chronically administered drugs also apply to most respiratory drugs. Modifications from the standard preclinical development plan, however, may be necessary if the drug is administered intranasally or by inhalation. Administration by these routes may result in airway toxicity and the intended patient population is often particularly susceptible. Current and former representatives of the Division of Pulmonary Drug Products (CDER, U.S. FDA) present this article to describe general principles of preclinical development for respiratory drug indications. The article addresses drugs intended for administration by the intranasal or inhalation routes. The article describes the types of studies recommended, considers the initial human dose, and discusses dose-escalation strategies in clinical trials. Other areas of special concern with intranasal or inhalation administration include immunotoxicity, reproductive toxicity, types of dosing apparatus, excipients and extractables, and formulation changes. The approaches described in this article are intended as general information and should be adapted to the scientific considerations and circumstances of a particular drug under development.

Humans↗
PubMed1997

Differentiation and apoptosis of human germinal center B-lymphocytes.

An in vitro experimental model was developed to characterize the cellular and molecular factors that regulate germinal center (GC)-B-cell differentiation and apoptosis. In the culture system that sustains the GC-B-cell survival, CD40L stimulation is essential for GC-B-cell proliferation and differentiation in the presence of 1L-2, IL-4, and IL-10. IL-2 and Il-4 promote proliferation of GC-B-cells, whereas IL-10 is required for generation of plasma cells. Generation of memory B cells requires CD40L, IL-2, IL-4, but not IL-10. There are two mechanisms that cause apoptosis. In the early stage, spontaneous apoptosis occurs in the absence of CD40 stimulation. Following CD40L stimulation, Fas-mediated apoptosis operates to eliminate GC-B-cells, unless activated GC-B-cells encounter a second signal via B-cell Ig receptors. Physiological significance of these findings is discussed.

Animals↗
PubMed1997

Assessment of mitral annulus velocity by Doppler tissue imaging in the evaluation of left ventricular diastolic function.

OBJECTIVES: This study assessed the clinical utility of mitral annulus velocity in the evaluation of left ventricular diastolic function. BACKGROUND: Mitral inflow velocity recorded by Doppler echocardiography has been widely used to evaluate left ventricular diastolic function but is affected by other factors. The mitral annulus velocity profile during diastole may provide additional information about left ventricular diastolic function. METHODS: Mitral annulus velocity during diastole was measured by Doppler tissue imaging (DTI) 1) in 59 normal volunteers (group 1); 2) in 20 patients with a relaxation abnormality as assessed by Doppler mitral inflow variables (group 2) at baseline and after saline loading; 3) in 11 patients (group 3) with normal diastolic function before and after intravenous nitroglycerin infusion; and 4) in 38 consecutive patients (group 4) undergoing cardiac catheterization in whom mitral inflow velocity and tau as well as mitral annulus velocity were measured simultaneously. RESULTS: In group 1, mean +/- SD peak early and late diastolic mitral annulus velocity was 10.0 +/- 1.3 and 9.5 +/- 1.5 cm/s, respectively. In group 2, mitral inflow velocity profile changed toward the pseudonormalization pattern with saline loading (deceleration time 311 +/- 84 ms before to 216 +/- 40 ms after intervention, p < 0.001), whereas peak early diastolic mitral annulus velocity did not change significantly (5.3 +/- 1.2 cm/s to 5.7 +/- 1.4 cm/s, p = NS). In group 3, despite a significant change in mitral inflow velocity profile after nitroglycerin, peak early diastolic mitral annulus velocity did not change significantly (9.5 +/- 2.2 cm/s to 9.2 +/- 1.7 cm/s, p = NS). In group 4, peak early diastolic mitral annulus velocity (r = -0.56, p < 0.01) and the early/late ratio (r = -0.46, p < 0.01) correlated with tau. When the combination of normal mitral inflow variables with prolonged tau (> or = 50 ms) was classified as pseudonormalization, peak early diastolic mitral annulus velocity < 8.5 cm/s and the early/late ratio < 1 could identify the pseudonormalization with a sensitivity of 88% and specificity of 67%. CONCLUSIONS: Mitral annulus velocity determined by DTI is a relatively preload-independent variable in evaluating diastolic function.

Adult↗
PubMed1997

Keratitis from corneal anesthetic abuse after photorefractive keratectomy.

After having photorefractive keratectomy (PRK), a 29-year-old man suffered from delayed epithelial healing and corneal stromal ring infiltrates. All laboratory results including smear, culture, and biopsy for bacteria, herpes simplex virus, and Acanthamoeba were negative. The suspected cause was patient abuse of anesthetics. Subsequently, it was discovered that for 6 months, since just after the PRK, the patient had intermittently used topical proparacaine drops. After all medication was discontinued and the eye pressure patched, the corneal epithelium healed completely. Practitioners should consider the possibility of topical anesthetic abuse in cases of keratitis after PRK.

Administration, Topical↗
PubMed1997

Epidural morphine plus ketamine for upper abdominal surgery: improved analgesia from preincisional versus postincisional administration.

Increased postoperative pain may be caused by central nervous system plasticity, which may be related to actions of N-methyl-D-aspartic acid (NMDA) receptors on neurons in the dorsal horn of the spinal cord. Opioids act mainly on presynaptic receptors and reduce neurotransmitter release, while ketamine antagonizes NMDA receptors and prevents wind-up and long-term potentiation. Thus, we postulated that central nervous system sensitization would be prevented more effectively by the preoperative use of these two drugs simultaneously, and the effect of preemptive analgesia would be demonstrated. Ketamine, 60 mg, and morphine, 2 mg, were injected epidurally through an indwelling catheter that was inserted at the T7-8 interspace in 60 ASA physical status class 1-2 patients. The drugs were injected before induction of anesthesia (Group 1; n = 30) or immediately after removal of a surgical specimen (Group 2; n = 30). An additional 2 mg of morphine was injected when the patients complained of resting pain. The analgesic effect was assessed by the time from first analgesic injection to second dose and the number of patients who needed supplemental injections. Complications were also noted. The duration of analgesia was longer (P < 0.01) in Group 1 (31.1 +/- 16.0 h) than in Group 2 (21.1 +/- 12.0 h), and the proportion of patients who needed supplemental injections was decreased (P < 0.05) in Group 1 (56.7%) compared with Group 2 (90.0%). The incidence of adverse effects was not different between the two groups. In conclusion, preoperative administration of morphine and ketamine is more effective in reducing postoperative pain than it is when given during the operation.

Abdominal Pain↗
PubMed1997

[Infection status with trematode metacercariae in the fresh-water fish from Chunamchosuchi (pond), Uichang-gun, Kyongsangnam-do, Korea].

The present study was performed to analyze the infection status of trematode metacercariae in fishes caught from Chunamchosuchi (pond) located in Uichang-gun, Kyongsangnam-do. A total of 130 freshwater fish of 5 species was collected by a fish net and fish traps from November, 1995 to May, 1996. They were examined under a stereomicroscope after artificial digestion with pepsin-HCl solution. A total of 8 species of metacercaria, i.e. Clonorchis sinensis, Echinochasmus japonicus, Cyathocotyle orientalis, Diplostomum sp., Metorchis orientalis, Holostephanus nipponicus, Exorchis oviformis and unidentified echinostome, was detected from them. The metacercariae of C. sinenesis were found in 8/20 (40.0%) Acanthorhodeus asmussi, 20/20 (100%) Culter brevicauda, 31/45 (68.9) Cultriculus eigenmanni and 21/25 (84.0%) Pseudorasbora parva, and the average number of metacercariae detected in each fish species were 1.9, 31.7, 15.3, and 73.0. From the above results, it was confirmed that fresh-water fishes from Chunamchosuchi (pond) were highly infected with metacercariae of avian trematode, i.e. C. orientalis, H. nipponicus, M. orientalis, E. japonicus and Diplostomum sp., and 4 species of fish, P. parva, C. brevicauda, C. eigenmanni and A. asmussi, were infected with metacaecariae of C. sinensis.

Animals↗
PubMed1997

The effect of diphenyl-dimethyl-dicarboxylate on cyclosporine-A blood level in kidney transplants with chronic hepatitis.

An adequate blood level of cyclosporine-A (CsA) is essential to keep graft function in kidney transplants. Due to a narrow therapeutic index and highly variable pharmacokinetic properties associated with CsA, drug interactions may have a significant impact on the immunosuppressive efficacy or toxicity of CsA. Numerous drug interactions of potential clinical significance involving CsA have been reported. Dephenyl-dimethyl-dicarboxylate (PMC), a hepatotonic drug, is a substance derived from the synthesis of Schizandrae fructus elements. We have experienced two cases of drug interaction between CsA and PMC in kidney transplants with chronic hepatitis. In both cases, CsA troughs decreased markedly to a subtherapeutic level following administration of PMC. We, therefore, suggest that PMC could decrease the CsA trough level and thus a close monitoring of the CsA trough level is necessary during a PMC therapy.

Chronic Disease↗
PubMed1997

Temperature-guided radiofrequency catheter ablation of accessory pathway.

OBJECTIVES: This study was performed to evaluate the usefulness of temperature-guided radiofrequency catheter ablation for the elimination of accessory pathway conduction in patients with Wolff-Parkinson-White syndrome. METHODS: Temperature-guided radiofrequency catheter ablation was attempted in 138 patients with 144 accessory pathways (88 pathways along the left free wall, 5 in the anteroseptal region, 2 in the midseptal region, 19 in the posteroseptal region and 30 along the right free wall). The energy source was a HAT 200S which regulated the power automatically to the set temperature of 70 degrees C. Radiofrequency current was delivered through a thermocatheter to the atrial or ventricular side of mitral or tricuspid annulus. RESULTS: Accessory pathway conduction was eliminated in 130 of 144 pathways (90.3%). The mean power outputs of the successful ablations at the atrial side of the annulus were higher than those at the ventricular side (34.0 +/- 8.9W versus 20.0 +/- 7.6W, p < 0.01), but the maximum temperatures were lower at the atrial side of the annulus than those at the ventricular side (66.4 +/- 14.0 degrees C versus 77.2 +/- 6.4 degrees C, p < 0.01). There were 3 non-fatal complications (2.1%), 2 patients with hemopericardium and 1 with femoral artery thrombus, during or after ablation procedures. Recurrences of AV re-entrant tachycardia or delta wave on the electrocardiogram occurred in 4 patients (2.8%) who had successful second procedures. There were no late complications during a mean follow-up period of 41 +/- 25 months (range, 3 to 55). CONCLUSION: We conclude that 1) temperature-guided radiofrequency catheter ablation can be performed reliably and safely in eliminating accessory pathway conduction in patients with WPW syndrome, and 2) temperature monitoring and adjustment of the power to the set temperature during ablation would be useful for the avoidance of impedance rises and coagulum formation.

Adolescent↗
PubMed1997

MR of childhood metachromatic leukodystrophy.

PURPOSE: To investigate the MR findings of childhood metachromatic leukodystrophy (MLD). METHODS: Nine MR imaging studies in seven children (five girls and two boys, 10 to 32 months old) with MLD were evaluated retrospectively for the extent and progression of white matter abnormalities and the presence of contrast enhancement. RESULTS: All seven cases showed symmetric, confluent high signal intensity on T2-weighted images in the periventricular white matter and centrum semiovale. A posterior predominance of white matter abnormalities was noted in all cases. Although initially spared from demyelination in all cases, in one case, the subcortical U fibers were later involved in demyelination of follow-up MR studies. Other sites of involvement were the genu (n = 5) and splenium (n = 6) of the corpus callosum, the posterior limbs of the internal capsule (n = 5), the descending pyramidal tracts (n = 4), the claustrum (n = 4), and the cerebral white matter (n = 2); diffuse brain atrophy was seen in two cases. No enhancement of the lesion was seen on any of the five postcontrast examinations. A "tigroid" pattern, previously described in cases of Pelizaeus-Merzbacher disease, was noted in the centrum semiovale in six cases. CONCLUSION: In late-infantile MLD, demyelination is more prominent in the occipital region. In addition to demyelination of the periventricular white matter, common manifestations include a "tigroid" pattern and involvement of the corpus callosum, the internal capsule, and the corticospinal tract.

Brain↗
PubMed1997

Computer analysis of human depth EEG in different sleep stages.

This study compares delta (< 4 Hz), theta (4-8 Hz), alpha (8-12 Hz) and beta (12-20 Hz) band EEG signals during wakefulness, rapid-eye-movement (REM) sleep, and stage 1 and stage 2 non-REM sleep recorded from both surface and depth electrodes in patients with drug-resistant partial seizures. Computer analysis utilizing Fast Fourier Transforms (FFT) was performed with the Neurovision software developed for this purpose. Mean amplitudes were calculated for each of the frequency bands. Preliminary analysis was performed with emphasis on the presence and characteristics of theta activity in the hippocampus of the brain. Results demonstrate theta wave activity in the hippocampus with an increase of theta activity in REM sleep as compared to non-REM sleep (stages 1 and 2).

Adult↗
PubMed1996

CD48 delivers an accessory signal for CD40-mediated activation of human B cells.

CD48, a glycosyl phosphatidylinositol anchored molecule has recently been shown to be a ligand for the T cell surface protein CD2 in mouse, human, and rat. It is expressed on practically all human T and B cells; however, its function remains unknown. We examined whether CD48 may be involved in the delivery of activating signals to human B cells. Costimulation with anti-CD48 J4-57 significantly increased CD40-mediated activation of tonsillar B cells. Costimulatory effect of anti-CD48 was observed on B cell aggregation, proliferation, and IgG secretion. Anti-CD48 alone did not stimulate resting B cells. Accessory signal provided through CD48 required the presence of IL-4 and/or IL-10, whereas responses of B cells to IL-2 was not affected. Ligation of CD48 by specific antibody induced CD23 expression on IL-4-stimulated Ramos B cell line but did not affect expression of CD25. We also examined the biochemical nature of the costimulatory effect of anti-CD40 and CD48. Ligation of CD40 or CD48 on the B cells induced tyrosine phosphorylation of proteins. CD40 induced earlier changes in the protein phosphorylation than CD48 did. Taken together, our data suggest that the stimulation via CD40 provides initial signals to activate B cells and CD48 may be involved in enhancing the activating signal to B cells, resulting in increased responsiveness of B cells to IL-4 and IL-10.

Antibodies, Monoclonal↗
PubMed1996

Up-regulation of Bcl-xL expression protects CD40-activated human B cells from Fas-mediated apoptosis.

CD40--CD40L interactions between resting B cells and activated T cells are essential for germinal center formation. It has been shown that CD40L can induce both Fas expression and susceptibility to Fas-mediated killing in B cells, while anti-Ig can partially rescue B cells from Fas-mediated killing. However, the intracellular mechanism for this phenomenon is not known. We examined the expression of Fas and bcl-2 family gene products, such as Bcl-2, Bcl-x, Bax, and Mcl-1, in human tonsillar B cells. The activation of naive B cells by CD40L induced transient expression of Bcl-xL. As the Bcl-xL level decreased in CD40-activated B cells, the cells became susceptible to apoptosis by anti-Fas antibodies. Though anti-Ig did not change the Fas expression, it protected CD40-activated B cells from Fas-mediated killing by up-regulating Bcl-xL expression. The addition of anti-Ig did not significantly change Bcl-2, Bax, and Mcl-1 levels compared to those of B cells activated by CD40L alone.

Apoptosis↗