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Biomedical subjects

S R Lee

Publications and source records attributed to S R Lee.

At least 55 records · Page 3Linked to original sources
PubMed1998

Rapid subgrouping of nonpolio enterovirus associated with Aseptic Meningitis by RFLP (Restriction Fragment Length Polymorphism) assay.

In Korea, there was a big outbreak of Aseptic Meningitis due to enterovirus infection in 1993. Since virus isolation and neutralizing tests are too laborious and time-consuming for the detection of enterovirus from clinical specimen, we have developed a new molecular identification method for rapid subgrouping of isolates from patients with aseptic meningitis. For the rapid subgrouping of isolates, RT-PCR (Reverse Transcription-Polymerase Chain Reaction) and RFLP (Restriction Fragment Length Polymorphism) assays were used. We have selected two oligonucleotide primers from the conserved 5'-UTR/VP2 and VP1 regions. A 652 bp (base pair) product was amplified from the 5'-UTR/VP2 region of reference viruses and the isolates. For the subgrouping of the isolates by RFLP assay, we have used 12 reference viruses (Echovirus, E6, E9, E11, E12, Coxsackievirus, CB1, CB3, CB4, CB5, Coxsackievirus, CA9, CA16, CA21, CA24), which are the common viral agents associated with aseptic meningitis. By using subgroup-specific restriction enzymes BsmAI, , HinP1I, and PleI, the isolates were classified into Echovirus subgroups. We have also shown that subgrouping of the isolates by RFLP assay based on the VP1 region is possible.

Capsid↗
PubMed1998

Nitric oxide inhibits c-Jun N-terminal kinase 2 (JNK2) via S-nitrosylation.

S-nitrosylation by S-nitrosoglutathione (GSNO), a nitric oxide (NO) donor, suppresses the phosphotransferase activity of cJun N-terminal kinase 2 (JNK2)/stress activated protein kinase (SAPK) in dose- and time-dependent manners in vitro. JNK2 activity is significantly decreased at 10 microM of GSNO, which is dramatically reversed by adding 10 mM of DTT. Reduced form of glutathione protects the GSNO-induced suppression of JNK2 activation in a dose-dependent fashion. However, GSNO-treated Sek1 does not affect the JNK2 activity of phosphotransferation toward c-Jun N-terminal1-79 protein. These results indicate that NO may exert a regulatory role of JNK2 activity by S-nitrosylation of the protein in apoptotic signaling pathway. Suppression of JNK2 phosphotransferase activity by NO is also supported by the observation that NO plays an important anti-apoptotic roles in heptocytes, splenocytes, eosinophils and B lymphocytes.

Apoptosis↗
PubMed1998

Reversible inactivation of protein-tyrosine phosphatase 1B in A431 cells stimulated with epidermal growth factor.

Stimulation of various cells with growth factors results in a transient increase in the intracellular concentration of H2O2 that is required for growth factor-induced protein tyrosine phosphorylation. The effect of H2O2 produced in response to epidermal growth factor (EGF) on the activity of protein-tyrosine phosphatase 1B (PTP1B) was investigated in A431 human epidermoid carcinoma cells. H2O2 inactivated recombinant PTP1B in vitro by oxidizing its catalytic site cysteine, most likely to sulfenic acid. The oxidized enzyme was reactivated more effectively by thioredoxin than by glutaredoxin or glutathione at their physiological concentrations. Oxidation by H2O2 prevented modification of the catalytic cysteine of PTP1B by iodoacetic acid, suggesting that it should be possible to monitor the oxidation state of PTP1B in cells by measuring the incorporation of radioactivity into the enzyme after lysis of the cells in the presence of radiolabeled iodoacetic acid. The amount of such radioactivity associated with PTP1B immunoprecipitated from A431 cells that had been stimulated with EGF for 10 min was 27% less than that associated with PTP1B from unstimulated cells. The amount of iodoacetic acid-derived radioactivity associated with PTP1B reached a minimum 10 min after stimulation of cells with EGF and returned to base line values by 40 min, suggesting that the oxidation of PTP1B is reversible in cells. These results indicate that the activation of a receptor tyrosine kinase by binding of the corresponding growth factor may not be sufficient to increase the steady state level of protein tyrosine phosphorylation in cells and that concurrent inhibition of protein-tyrosine phosphatases by H2O2 might also be required.

Amino Acid Sequence↗
PubMed1998

Survival of patients with glioblastoma multiforme is not influenced by altered expression of p16, p53, EGFR, MDM2 or Bcl-2 genes.

Deregulated expression of one or more growth control genes including p16, p53, EGF receptor (EGFR), MDM2 or Bcl-2 may contribute to the treatment resistance phenotype of GBM and generally poor patient survival. Clinically, GBM have been divided into two major groups defined by (1) histologic progression from a low grade tumor ("progressive" or "secondary" GBM) contrasted with (2) those which show initial clinical presentation without a prior history ("de novo" or "primary" GBM). Using molecular genetic analysis for p53 gene mutations together with immunophenotyping for overexpression of EGFR, up to four GBM variants can be distinguished, including the p53+/EGFR- progressive or the p53-/EGFR+ de novo variant. We examined the survival of 80 adult patients diagnosed with astrocytic GBM stratified by age category (>40, 41-60 or 61-80) to determine whether alterations in any one given growth control gene or whether different genetic variants of GBM (progressive versus de novo) were associated with different survival outcomes. Survival testing using Kaplan-Meier plots for GBM patients with or without altered expression of p16, p53, EGFR, MDM2 or Bcl-2 showed no significant differences by age group or by gene expression indicating a lack of prognostic value for GBM. Also the clinical outcome among patients with GBM showed no significant differences within each age category for any GBM variant including the progressive and de novo GBM variants indicating similar biologic behavior despite different genotypes. Using a pairwise comparison, one-third of the GBM with normal p16 expression showed accumulation of MDM2 protein and this association approached statistical significance (0.01 < P < 0.05) using the Bonferroni procedure. These GBM may represent a variant in which the p19ARF/MDM2/p53 pathway may be deregulated rather than the p16/cyclin D-CDK4/Rb pathway.

Adult↗
PubMed1998

Use of overlapping synthetic peptides to characterize samples from blood donors with indeterminate results to hepatitis C virus core antigen.

BACKGROUND AND OBJECTIVES: Despite recent improvements in supplemental assays, isolated reactivity to the hepatitis C virus (HCV) core antigen continues as one of the main problems in the confirmation of anti-HCV in blood donors. Reactivity against individual peptides from the c22-3 HCV recombinant antigen has been described as a useful tool for anti-HCV confirmation and donor counseling in such cases. MATERIALS AND METHODS: We used a previously described set of overlapping peptides spanning the entire sequence of the c22-3 antigen to study 87 single serum samples from blood donors with reactivity for c22-3 antigen alone in second generation recombinant immunoblot assay (RIBA-2). All of them had been previously studied by RIBA-3, anti-HCV E2 EIA and HCV PCR. RESULTS: 66 of the 87 samples studied could be classified as positive or negative for anti-HCV core using the multipeptide assay and such classification correlated well with the results obtained with RIBA-3 and the anti-E2 EIA. However, some discrepancies were found. The epitopes located along the N-terminal half of the molecule were mainly responsible for the specific antibody recognition but those enclosed within amino acids 1-15 were frequently involved in nonspecific reactivity. Some 38% of samples were considered to have specific antibody to the c22-3 antigen and a further 9% reacted for both anti-E2 and single core peptides that were often involved in specific antibody recognition. CONCLUSION: Testing of blood donor samples indeterminate to the HCV c22-3 antigen for reactivity against individual core peptides can confirm the presence of specific antibody and recognize nonspecific reactivity with certain cross-reacting epitopes. Third generation supplemental tests have reduced such false reactivity, but confirmation of samples with anticore alone is still necessary. Single reactivity to the HCV core antigen is likely to reflect prior exposure to the virus, but rarely active infection, either acute or chronic.

Antibody Specificity↗
PubMed1998

Right ventricular dysfunction after tetralogy repair in a pediatric patient with successful ECMO support--a case report.

Right ventricular dysfunction after surgical repair of tetralogy is a serious life threatening complication. Although pulmonary vasodilators and inotropes can be used for cardiac support in tetralogy repair, these drugs may be ineffective in some patients. To date extracorporeal membrane oxygenation (ECMO) support may be used effectively in these patients when medical therapy fails. We report a case with successful ECMO support in right ventricular dysfunction and pulmonary hypertension after total surgical correction of Fallot's tetralogy. ECMO circuit was instituted in the operating room due to difficulty in weaning from cardiopulmonary bypass in spite of aggressive medical therapy. We reviewed and discussed the indications, contraindications of application of ECMO and patient survival with treatment of ECMO. At the same time we wish to share our limited experience we gained in our first attempt of ECMO support.

Extracorporeal Membrane Oxygenation↗
PubMed1998

Multiple cerebellar infarction due to vertebral artery obstruction and bulbar symptoms associated with vertical subluxation and atlanto-occipital subluxation in ankylosing spondylitis.

Ankylosing spondylitis (AS) results in disease-specific inflammation at the site of ligamentous insertion into the bone. Atlantoaxial joint subluxation and vertical subluxation of the axis may occur as a consequence of instability resulting from the inflammatory process. Spontaneous anterior atlantoaxial subluxation is a well recognized complication in about 2% of patients with AS, and presents with or without signs of spinal cord compression. Vertical subluxation may follow anterior or posterior subluxation. It was noted in 3-8% of patients with rheumatoid arthritis, but is an exceedingly rare complication of AS. Moreover, it has never been reported that multiple cerebellar infarction and bulbar symptoms developed spontaneously due to atlanto-occipital subluxation and vertical subluxation in a patient with a long [corrected] history of AS. We describe a man with AS who developed multiple cerebellar infarction due to vertebral artery obstruction and bulbar symptoms associated with atlanto-occipital subluxation and vertical subluxation.

Arterial Occlusive Diseases↗
PubMed1997

Immunologic events during the incubation period of hepatitis C virus infection: the role of antibodies to E2 glycoprotein. Multicentre Hemodialysis Cohort Study on Viral Hepatitis.

BACKGROUND: The study of the sensitivity of screening assays is greatly facilitated by testing the sequential changes in seroconverting individuals. The aim of this study was to investigate the early immunologic response after hepatitis C virus (HCV) infection and to evaluate whether HCV envelope (E2) recombinant antigen would provide a significant increase in sensitivity for detection of anti-HCV. STUDY DESIGN AND METHODS: Twenty hemodialysis patients who were seroconverting to anti-HCV were included in this study. They were followed up for a mean period (+/- SD) of 10.5 +/- 3.3 months, in which 13 to 46 serum samples per case were collected. Each sample was tested for anti-HCV by second- and third-generation enzyme immunoassay (EIA-2 and EIA-3) and recombinant immunoblot assay (RIBA-3). E2 antibodies were tested by a prototype EIA in which E2 was expressed as a recombinant antigen in Chinese hamster ovary cells. RESULTS: Alanine aminotransferase elevation was observed in 18 of 20 cases. Reactivity against c100, c33c, c22, NS5, and E2 was detected in 15 (75%), 19 (95%), 15 (75%), 2 (10%), and 17 (85%) patients, respectively; c33c was the most immunogenic antigen, followed in descending order by E2, c22, c100, and NS5. E2 antibody reactivity resolved the two RIBA-3-indeterminate cases. However, there was no case in which E2 reactivity preceded all other HCV antigens. Anti-E2 was found to react in all patients of genotypes 1a, 1b, and 3a but in only 2 of 4 patients of genotype 4a. CONCLUSION: In this group of seroconverting individuals, E2 antigen was shown to be highly immunoreactive and did resolve some RIBA-3-indeterminate samples as being positive, on the basis of reactivity to multiple antigens, but it did not improve early detection of seroconversion.

Aged↗
PubMed1996

A heme-containing ascorbate oxidase from Pleurotus ostreatus.

A novel type of ascorbate oxidase was purified 420-fold from the cytosolic fraction of the mycelia of Pleurotus ostreatus with an overall yield of 13%. The molecular mass of the native enzyme determined by high performance gel permeation chromatography was 94 kDa. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the enzyme consists of two subunits with a molecular mass of 46 kDa. The N-terminal amino acid sequence of the enzyme was Asp-Val-Lys-Thr-Leu-Gln-Glu-His-Leu-Gln-Leu-Ala-Leu-Met-Val-. The enzyme was optimally active at pH 5.2, monitored at 37 degrees C. The enzyme had affinity toward L-ascorbic acid, D-ascorbic acid, L-erythroascorbic acid, and D-erythroascorbic acid. Under optimal conditions, the Km value of the enzyme toward L-ascorbic acid was 0.48 mm. The absorption spectra of the native enzyme exhibited a Soret maximum at 418 nm in its oxidized form and at 426 nm in its reduced form, and alpha and beta bands at 558 and 527 nm only in its reduced form, respectively. On the basis of spectral changes after treatment with cyanide and carbon monoxide, the enzyme is a hemoprotein, quite similar to b-type cytochrome, and contains 2 mol of heme per molecule. The reaction catalyzed by the enzyme was L-ascorbic acid + O2 --> dehydro-L-ascorbic acid + H2O2.

Amino Acid Sequence↗
PubMed1996

Characterization of HIV incubation distributions and some comparative studies.

In this paper we use a general stochastic model to characterize the HIV incubation distributions. We generate some Monte Carlo data under different conditions and compare the fitting of HIV incubation distributions by some well known parametric models and some non-parametric methods. The parametric models include most of those that have appeared in the literature. The non-parametric methods include the Kaplan--Meier method, the EMS method, the spline approximation and the Bacchetti method. The comparison criteria are the chi-square statistic, the residual sum of squares, the AIC and the BIC. We show that the non-parametric methods, especially the EMS method, provide excellent fits in almost all cases; for the parametric models, the generalized log-logistic distributions with three and with four parameters fit better than other parametric models.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Clinical significance of hepatitis C viral RNA status and its correlation to antibodies to structural HCV antigens in anti-HCV reactive patients with normal liver tests.

Extensive serological testing and HCV RNA determination by RT-PCR was performed in serum, PBMCs, and liver tissue in thirteen anti-HCV reactive patients with persistently normal liver tests. Absolute concordance in the status of HCV RNA between serum, PBMCs, and liver was noted. Five patients were HCV RNA positive but only three had mild histological changes. Eight patients were HCV RNA negative in all three sites and had virtually normal liver histology. Patterns of reactivity in RIBA 2.0 strip immunoblot assay did not differentiate viremic from nonviremic patients. ELISA testing using multiple individual HCV recombinant antigens from the structural and non-structural regions of HCV demonstrated mean antibody titers to the structural antigens, in particular HCV E2 antibodies, to be significantly lower in HCV RNA negative patients. The status of HCV RNA in the serum appears to infer the status of HCV RNA in the liver and PBMCs in patients with persistently normal liver tests. Patients with persistently normal liver tests and undetectable HCV RNA have probably spontaneously cleared HCV infection.

Adult↗
PubMed1996

Non-ketotic hyperglycaemic chorea: a SPECT study.

OBJECTIVE: To study regional blood flow of the striatum in non-ketotic hyperglycaemic choreic patients. METHODS: Brain SPECT was performed with intravenous injection of 20 mCi 99mTc hexamethylpropylene amineoxime in six non-ketotic hyperglycaemic choreic patients and 10 age matched patients with a similar level of hyperglycaemia without chorea as a control. The focal perfusion defects were analysed by visual interpretation and semiquantitative determination with reference to homolateral occipital blood flow. RESULTS: The measured blood flow of striatum on the contralateral side of chorea was significantly decreased. CONCLUSIONS: Hypometabolism of the striatum is seen not only in Huntington's disease, but also in non-ketotic hyperglycaemic chorea. Hypofunction of the striatum is a possible common pathogenesis in the development of contralateral chorea in different diseases. Furthermore, the sensitivity and reliability of SPECT is as good as PET in assessing choreic patients.

Aged↗
PubMed1995

Molecular cloning of cDNA for sapecin B, an antibacterial protein of Sarcophaga, and its detection in larval brain.

A cDNA clone for sapecin B, an antibacterial protein of Sarcophaga, was isolated. This cDNA encoded a precursor protein of sapecin B consisting of a signal sequence (24 residues), prosegment (30 residues) and mature sapecin B (34 residues). Sapecin B was synthesized almost exclusively in the fat body when the larval body wall was injured, but the brain of naive larvae was also demonstrated to contain a significant amount of sapecin B. These findings suggested that sapecin B is a bifunctional protein.

Amino Acid Sequence↗
PubMed1995

Characterization of HIV infection and seroconversion by a stochastic model of the HIV epidemic.

In this paper we use a stochastic model for the HIV epidemic in homosexual populations to characterize the HIV infection and seroconversion. Using computer generated data, we compare the fitting of infection distributions and of seroconversion distributions by different parametric models as well as by nonparametric methods. The nonparametric methods include the Kaplan-Meier method, EMS method, Bacchetti's method, and the spline approximation. The parametric models include most of the models which have been used in the literature. The comparison criteria are the chi-square statistic, the AIC (Akaike Information Criterion) and the residual sums of squares. The numerical results suggest that for the proportional mixing pattern, the EMS method, the spline method, Bacchetti's method, and the generalized log-logistic distributions with three and with four parameters provide better fitting for the infection and the seroconversion distributions in most cases. For the restricted mixing patterns, the EMS method, the spline method, Bacchetti's method, and some mixtures of distributions provide close fitting to the infection and the seroconversion distributions.

Disease Outbreaks↗