PubMed Health⌕ Search

Biomedical subjects

S K Oh

Publications and source records attributed to S K Oh.

At least 19 recordsLinked to original sources
PubMed2005

Reduced L-arginine level and decreased placental eNOS activity in preeclampsia.

Nitric oxide is produced enzymatically by the nitric oxide synthase (NOS), which converts L-arginine in the presence of oxygen to L-citrulline and NO. Moreover, it has been reported that asymmetric dimethylarginine (ADMA) acts as is an endogenous inhibitor of endothelial NOS (eNOS) by competing with the enzyme for L-arginine. In this study, we measured L-arginine and ADMA in normal and preeclamptic women, and also investigated the association between the Glu298Asp eNOS gene polymorphism and preeclampsia. Finally, we assessed eNOS expression levels in the placentas of both normal and preeclamptic patients, using Western blot and immunohistochemistry. L-arginine levels were found to be significantly lower in the preeclamptic women than in the normal pregnant women (p=0.02) but there were no significant differences in ADMA levels between the normal and preeclamptic women. We also determined there to be no association between the Glu298Asp eNOS gene and preeclampsia. With regard to placental eNOS expression, we detected a lower degree of eNOS expression in the preeclamptic syncytiotrophoblasts than in the normal syncytiotrophoblasts. We suggest that reduced L-arginine levels, rather than increased ADMA levels, contribute to the development of preeclampsia, and also that decreased placental eNOS expression constitutes a characteristic finding in preeclamptic placentas.

Adult↗
PubMed2001

Inhibition of baclofen on morphine-induced hyperactivity, reverse tolerance and postsynaptic dopamine receptor supersensitivity.

The effects of baclofen on the development of reverse tolerance and postsynaptic dopamine receptor supersensitivity induced by morphine were examined in mice. A single administration of morphine induced hyperactivity and the morphine-induced hyperactivity was inhibited dose dependently by the administration of a GABA(B)receptor agonist, baclofen (1.25, 2.5 and 5 mg kg(-1), i.p.). Daily repeated administration of morphine developed reverse tolerance to the hyperactivity of morphine. The concomitant administration of baclofen inhibited the morphine-induced hyperactivity and the baclofen administration prior to and during the chronic administration of morphine in mice inhibited the development of reverse tolerance to the hyperactivity of morphine (10 mg kg(-1), s.c.). Postsynaptic dopamine receptor supersensitivity was also developed in reverse-tolerant mice that had received the same morphine. The development of postsynaptic dopamine receptor supersensitivity was evidenced by the enhanced ambulatory activity of apomorphine (2 mg kg(-1), s.c.). Baclofen also inhibited the development of postsynaptic dopamine receptor supersensitivity induced by the chronic administration of morphine. These results suggest that the hyperactivity, reverse tolerance and postsynaptic dopamine receptor supersensitivity induced by morphine may be modulated via the activation of GABA(B)receptors induced by baclofen.

Animals↗
PubMed2001

Inhibitory effects of MK-801 on contextual sensitization to climbing behavior and on development of tolerance to hypothermia induced by a single high dose of apomorphine.

A single high dose of apomorphine (10 mg x kg(-1)) produced not only contextual sensitization to and conditioning of climbing behavior, but also context-independent tolerance to hypothermia. MK-801 (0.15 and 0.3 mg x kg(-1)) inhibited contextual sensitization to and conditioning of climbing behavior. Development of tolerance to hypothermia was also inhibited by MK-801. Dopamine D1 antagonist, SCH23390 (0.5 mg x kg(-1)), but not D2 antagonist, sulpiride, inhibited sensitization to and conditioning of climbing behavior. D2 antagonist, sulpiride (50 mg x kg(-1)), but not D1 antagonist, SCH23390, inhibited development of tolerance to hypothermia. These results suggest that MK-801 inhibited contextual sensitization to climbing behavior and development of tolerance to hypothermia through glutamatergic modulation of dopaminergic functions at dopamine receptors.

Animals↗
PubMed2001

Inhibitory effect of fangchinoline on excitatory amino acids-induced neurotoxicity in cultured rat cerebellar granule cells.

Glutamate receptors-mediated excitotoxicity is believed to play a role in the pathophysiology of neurodegenerative diseases. The present study was performed to evaluate the inhibitory effect of fangchinoline, a bis-benzylisoquinoline alkaloid, which has a characteristic as a Ca2+ channel blocker, on excitatory amino acids (EAAs)-induced neurotoxicity in cultured rat cerebellar granule neuron. Fangchinoline (1 and 5 microM) inhibited glutamate (1 mM), N-methyl-D-aspartate (NMDA; 1 mM) and kainate (100 microM)-induced neuronal cell death which was measured by trypan blue exclusion test. Fangchinoline (1 and 5 microM) inhibited glutamate release into medium induced by NMDA (1 mM) and kainate (100 microM), which was measured by HPLC. And fangchinoline (5 microM) inhibited glutamate (1 mM)-induced elevation of intracellular calcium concentration. These results suggest that inhibition of Ca2+ influx by fangchinoline may contribute to the beneficial effects on neurodegenerative effect of glutamate in pathophysiological conditions.

Alkaloids↗
PubMed2001

Fluorodeoxyglucose positron emission tomography for detection of recurrent or metastatic breast cancer.

Fluorodeoxyglucose-positron emission tomography (FDG-PET) is a noninvasive imaging technique capable of identifying primary tumors and metastases with high sensitivity and accuracy. The aim of this study was to evaluate the diagnostic accuracy of whole-body FDG-PET imaging for the detection of recurrent or metastatic breast cancer after surgery. Whole-body FDG-PET imaging was performed on 27 patients with suspected recurrent breast carcinoma. PET images were evaluated qualitatively for each patient and lesion. FDG-PET scans showed that there were 61 reference sites of malignant or benign lesions in 27 patients. In a patient-based analysis, FDG-PET scans correctly identified 16 of 17 patients with recurrent or metastatic disease and 8 of 10 without recurrence, resulting in a sensitivity, specificity, and accuracy of 94%, 80%, and 89%, respectively. In a lesion-based analysis, FDG-PET scans correctly identified 46 of 48 lesion sites with recurrent or metastatic disease and 11 of 13 without recurrence. The overall sensitivity, specificity, and accuracy for all lesion sites were 96%, 85%, and 93%, respectively. FDG-PET scans revealed unsuspected recurrent or metastatic diseases in 8 of 27 (30%) of patients and 11 of 20 (55%) distant metastatic lesions. In 13 patients treatment was altered by the outcome of the PET scan. We concluded that whole-body FDG-PET scan is a useful diagnostic imaging modality for detecting recurrent or metastatic breast carcinoma in patients suspected of having recurrent disease after primary surgery.

Adult↗
PubMed2000

Molecular cloning, expression, and functional analysis of a cis-prenyltransferase from Arabidopsis thaliana. Implications in rubber biosynthesis.

cis-Prenyltransferase catalyzes the sequential condensation of isopentenyl diphosphate with allylic diphosphate to synthesize polyprenyl diphosphates that play vital roles in cellular activity. Despite potential significance of cis-prenyltransferase in plant growth and development, no gene of the enzyme has been cloned from higher plants. Using sequence information of the conserved region of cis-prenyltransferase cloned recently from Escherichia coli, Micrococcus luteus, and yeast, we have isolated and characterized the first plant cis-prenyltransferase from Arabidopsis thaliana. Sequence analysis revealed that the protein is highly homologous in several conserved regions to cis-prenyltransferases from M. luteus, E. coli, and yeast. In vitro analyses using the recombinant protein overexpressed in E. coli revealed that the enzyme catalyzed the formation of polyprenyl diphosphates ranging in carbon number from 100 to 130 with a predominance of C(120). The enzyme exhibited a higher affinity for farnesyl diphosphate than for geranylgeranyl diphosphate, with the K(m) values being 0.13 and 3.62 micrometer, respectively, but a lower affinity for isopentenyl diphosphate, with a K(m) value of 23 micrometer. In vitro rubber biosynthesis analysis indicated that the Arabidopsis cis-prenyltransferase itself could not catalyze the formation of higher molecular weight polyprenyl diphosphates similar to natural rubber. A reverse transcriptase-polymerase chain reaction analysis showed that the gene was expressed at low levels in Arabidopsis plant, in which expression of the cis-prenyltransferase in leaf and root was higher than that in stem, flower, and silique. These results indicate the tissue-specific expression of cis-prenyltransferase and suggest a potential role and significance of the enzyme in the polyisoprenoid biosynthesis in plants.

Amino Acid Sequence↗
PubMed2000

Use of a dual monoclonal solid phase and a polyclonal detector to create an immunoassay for the detection of human cardiac troponin I.

OBJECTIVES: We report the development of a fully automated, random access, chemiluminescent immunoassay, for the detection of human cardiac Troponin I (cTnI) in serum and plasma for use on the ACS:180(R) System. DESIGN AND METHODS: This assay format uses a combination of two monoclonal antibodies covalently coupled to paramagnetic (PMP) particles as a solid phase and an affinity purified polyclonal antibody, specific to the N-terminal domain of cTnI (peptide-3 region) labeled with a chemiluminescent compound as the detector antibody. The assay offers excellent low-end sensitivity and precision. RESULTS: No interferences are observed from by blood components such as HAMA and drugs used in cardiac therapy. Patient samples tested on the ACS:180 cTnI assay showed good correlation with the Stratus cTnI assay (ACS: cTnI = 1. 02*Stratus + 0.05 g/L, r = 0.96, n = 1170). CONCLUSION: Paired with the other ACS:180 cardiac assays, myoglobin and CKMBII, the ACS:180 system now offers an excellent panel of cardiac assay for use in rapid and accurate diagnosis of a myocardial event.

Antibodies, Monoclonal↗
PubMed2000

Flow cytometric analysis of primary tumors and their corresponding metastatic nodes in breast cancer.

Human breast carcinoma is biologically heterogeneous, and its clinical course may vary from one which is indolent to one which rapidly progresses. Although it is the metastasis rather than the primary tumor that ultimately overwhelms the patients, studies concerning the DNA pattern have focused on the primary tumors. This study was undertaken to identify heterogeneities between primary tumors and metastases, and to evaluate the prognostic significance of the ploidy pattern and the S-phase fraction (SPF) of metastatic nodes in axillary node positive patients. Seventy-four frozen specimens of the primary and corresponding metastatic nodes from 37 patients have been analyzed by flow cytometry and the SPF calculated. The results of ploidy pattern analysis in primaries revealed 25 diploidy (67.6%) and 12 aneuploidy (32.4%), while those in metastasis showed 17 diploidy (46.0%) and 20 aneuploidy (54.0%). The aneuploidy group in metastatic nodes had the poorer histological grade (85.0% vs. 15.0%, p = 0.02), and more mean metastatic nodes (5.75 +/- 2.10 vs. 3.05 +/- 1.56, p = 0.018), and more frequent lymphatic vessel invasion (65.0% vs. 11.8%, p = 0.031) than its counterpart. Decreased expression of ER (70.6% vs. 25.0% p = 0.006) and increased expression of c-erbB2 (65.0% vs. 23.5%, p = 0.012) were observed in the aneuploidy of metastatic nodes. The group with higher SPF in metastatic nodes had more metastatic nodes (5.47 +/- 2.31 vs. 4.00 +/- 1.78, p = 0.042), and the higher incidence of lymphatic vessel invasion (57.9% vs. 22.2%, p = 0.027), and poor histological grade (71.4% vs. 37.5%, p = 0.039). In conclusion, the cell populations in metastatic nodes revealed DNA pattern which differed from that of primary tumors. The ploidy pattern and SPF in metastatic nodes might be considered as discriminate measure for risk factors in breast cancer patients with positive axillary node.

Adult↗
PubMed2000

Experimental basis for cancer prevention by vitamin E.

Recent clinical trials have demonstrated the significant cancer preventive potential of vitamin E in many different cancer sites, ranging from oral and pharyngeal cancer to prostate cancer. There is an extensive experimental basis for this clinical cancer inhibition. The experimental background includes animal studies (experimental pathology, immunology and molecular biology, synergism, selectivity and safety), in vitro biochemical studies, and human studies (epidemiology and biomarkers, prevention of many pathologic entities other than cancer).

Animals↗
PubMed1999

Isolation, characterization, and functional analysis of a novel cDNA clone encoding a small rubber particle protein from Hevea brasiliensis.

Biochemical evidence reported so far suggests that rubber synthesis takes place on the surface of rubber particles suspended in the latex of Hevea brasiliensis. We have isolated and characterized a cDNA clone that encodes a protein tightly bound on a small rubber particle. We named this protein small rubber particle protein (SRPP). Prior to this study, this protein was known as a latex allergen, and only its partial amino acid sequence was reported. Sequence analysis revealed that this protein is highly homologous to the rubber elongation factor and the Phaseolus vulgaris stress-related protein. Southern and Northern analyses indicate that the protein is encoded by a single gene and highly expressed in latex. An allergenicity test using the recombinant protein confirmed that the cloned cDNA encodes the known 24-kDa latex allergen. Neither ethylene stimulation nor wounding changed the transcript level of the SRPP gene in H. brasiliensis. An in vitro rubber assay showed that the protein plays a positive role in rubber biosynthesis. Therefore, it is likely that SRPP is a part of the rubber biosynthesis machinery, if not the rubber polymerase, along with the rubber elongation factor.

Allergens↗
PubMed1999

Effect of protease inhibitor on ischemia-reperfusion injury to rat liver.

Liver failure due to ischemia-reperfusion injury, believed to be closely related to the generation of oxygen-free radicals, is a serious problem during liver surgery. Gabexate mesilate, a synthetic protease inhibitor, suppresses the extracellular release of oxygen-free radicals in the microvascular endothelium. To determine its effects on ischemia-reperfusion injury to the liver, we performed experiments with rats. We divided the animals into two ischemia-reperfusion groups: an experimental group, which underwent ischemic injury for 30 minutes, along with the infusion of gabexate mesilate, and a control group, which underwent injury only. Each group was then divided into four subgroups: ischemic injury only and 60-, 120-, and 180-minute reperfusion injury. The test parameters were tumor necrosis factor alpha (TNFalpha) and interleukin-6 (IL-6) in serum and superoxide dismutase (SOD), catalase, and malondialdehyde (MDA) in liver and lung tissues. The experimental group had a significantly higher liver SOD and catalase levels and a significantly lower level of liver and lung MDA than the control groups. TNFalpha levels in the experimental groups were significantly lower during the early phase, but a comparison of IL-6 levels between the two groups yielded no differences. Levels of lung catalase and SOD were not significantly different between the two groups. We concluded that protease inhibitor suppressed liver ischemia-reperfusion injury, and that it was due to an increase of antioxidant or suppression of oxygen-free radicals. The roles of TNFalpha and IL-6 in liver reperfusion injury were not clear, though TNFalpha might have had an effect during the early phase. With liver ischemia-reperfusion injury, the mechanism of lung involvement might be different from that of liver involvement.

Animals↗
PubMed1999

Detection of cancer in augmented breasts by positron emission tomography.

OBJECTIVE: To assess the diagnostic efficiency of positron emission tomography with 18-fluorine fluorodeoxyglucose in detecting breast cancer in augmented breasts. DESIGN: Retrospective study. SETTING: University hospital, Korea. SUBJECT: 9 cases or 8 patients with breasts augmented with paraffin or silicone. INTERVENTION: FDG-PET, mammography, and ultrasonography RESULTS: The mammogram detected the breast cancer in only 1 of 3 patients, and ultrasonography gave a false positive result in 1 patient with an augmented breast. In contrast, PET predicted all the cancers and 5/6 benign lesions. 2/3 breast cancers had axillary FDG uptake interpreted as showing metastatic involvement, and in 1 case with cancer with no axillary lymph node involvement there was no FDG uptake in the axilla, which correlated with the pathological finding. CONCLUSIONS: Although the high cost of PET makes its use as a screening test for all patients with augmented breasts unrealistic, it would be the best diagnostic choice if other methods failed.

Axilla↗
PubMed1999

Chromosomal abnormalities in child psychiatric patients.

To determine the frequency of chromosomal abnormalities in a child psychiatric population, and to evaluate possible associations between types of abnormalities and patient's clinical characteristics, cytogenetic examination was performed on 604 patients. Demographic data, reasons for karyotyping, clinical signs, and other patient characteristics were assessed and correlated with the results from karyotyping. Chromosomal abnormalities were found in 69 patients (11.3%); these were structural in 49 cases and numerical in 20. Inversion of chromosome nine was found in 15 subjects, trisomy of chromosome 21 in 11, and fragile X in five patients. When karyotyping was performed because of intellectual impairment or multiple developmental delay, significantly more abnormalities were found than average; when performed because autistic disorder was suspected, the number of abnormalities was significantly fewer. There were no differences in clinical variables between structural and numerical abnormalities, nor among nine types of chromosomal abnormalities, except that numerical abnormalities and polymorphism were found at a later age, and that walking was more delayed and IQ was lower in patients with Down syndrome. Clinicians should be aware of the possible presence of chromosomal abnormalities in child psychiatric populations; the close collaboration with geneticists and the use of more defined guidelines for cytogenetic investigation are important.

Adolescent↗
PubMed1998

Diagnostic value of positron emission tomography for detecting breast cancer.

Positron emission tomography (PET) is an imaging method that employs radionuclide and tomography techniques. PET has high sensitivity for detecting breast cancer, both the primary tumor and axillary node metastasis. From June 1995 to November 1996 a total of 27 patients underwent breast operations based on PET results at Seoul National University Hospital. Whole-body PET images were obtained beginning 60 minutes after injection of 370 MBq (10 mCi) 18F-fluorodeoxyglucose. Regional scans were also obtained with transmission images. We compared the PET results with those from the physical examination and mammography. All cases were histologically confirmed. The diagnostic accuracy of PET was excellent for the primary tumor mass (97%) compared with that of the physical examination (78%) and mammography (67%). For axillary lymph node metastasis, PET had outstanding detection accuracy (96%) compared with the physical examination and mammography (74% and 60%, respectively). Whole-body PET scans made it possible to see all of the metastatic lesions at a glance in cases of metastatic or recurrent breast cancer. There was a probable correlation between the standard uptake value (SUV) and the number of axillary lymph node metastases, but in this study statistical significance was not proved because of the small number of cases. PET also could detect breast cancer in paraffin-augmented breasts. We concluded that PET is a highly sensitive, accurate diagnostic tool for breast cancer and that SUV, after more studies, could be used as an important prognostic factor.

Breast Neoplasms↗
PubMed1995

Effect of growth factors on the expression of proto-oncogenes c-fos and c-myc in FRTL-5 cell line.

This study was performed to prove the hypothesis that oncogene expressions would have the same patterns with those of cellular growth to growth factors in FRTL-5 cells. Ribonucleic acids of FRTL-5 were extracted at 15', 30', 60' and 120' after administration of growth factors to quiescent FRTL-5, and blotted to the nitrocellulose membrane. They were hybridized with radiolabelled c-fos, c-myc and beta-actin probes. Hybridized dot blots were autoradiographed and the amount of radioactivity was measured by densitometry. Densitometric readings were used as the indices of oncogene expressions. Expressions of c-fos and c-myc were more prominent in combined administrations of TSH (10 mU/ml) and IGF-I (100 ng/ml) or IgG of Graves' disease (Graves' IgG; 1 mg/ml) and IGF-I than in combined administration of TSH and Graves' IgG. IgG of primary myxedema suppressed oncogene expressions by TSH or Graves' IgG, but not by IGF-I. From the above results, it was suggested that expressions of c-fos and c-myc to growth factors would have similar patterns with those of cell growth to growth factors in FRTL-5, and the actions of TSH and Graves' IgG would be manifested through same signal transduction system, but IGF-I would be manifested by its own.

Animals↗
PubMed1994

Hyper-stimulation of monoclonal antibody production by high osmolarity stress in eRDF medium.

An earlier study (Chua et al., 1994) showed that hybridoma 2HG11 cultivated in a basal medium called eRDF, which is enriched in amino acids, enabled higher immunoglobulin (Ig) production with and without serum, when compared to two other traditional media RPMI and DMEM/F12. A further enhancement of Ig productivity was achieved when the osmolarity of the culture medium was increased from 300 mOsm to 350 mOsm (Oh et al., 1993). To determine whether the eRDF media was indeed better, three other cell lines, two IgG producers (TB/C3 and I13/17) and an IgM producer (B10), were tested. The results showed that maximum viable cell densities in eRDF medium were up to 3-times higher than in RPMI and maximum Ig titres were 2-8-times higher than in DMEM/F12 and RPMI. The three cell lines were similarly subjected to osmotic increases from 300 mOsm to 350 and 400 mOsm by addition of NaCl. There was an increase in Ig titres of between 30% to 100% compared to the control medium, although cell growth was reduced. Thus, hyper-stimulation by osmolarity stress was found to be generally effective in eliciting higher Ig production; the extent of enhancement being more pronounced for certain cell lines. Other osmolytes such as sucrose and KCl demonstrated similar effects of increasing Ig productivity. Study on the mechanism of action of osmotic stress on hybridoma 2HG11 revealed that hyper-stimulation of Ig productivity was fundamentally related to a greater availability of amino acids to cells as the cells actively accumulated more salt and amino acids to compensate for the higher medium osmolarity. Uptake of the amino acid analogues 14C-aminoisobutyric acid and 3H-methylaminoisobutyric acid into cells increased to 2.34 x 10(3) cpm per cell per min and 6.35 x 10(3) cpm per cell per min, respectively, under osmotic stress. This corresponds to an 85% increase in uptake via the Na(+)-dependent symport and a 50% increase in uptake via the Na(+)-independent and Na(+)-dependent symports. In the 350 mOsm medium, hybridomas also demonstrated an increase in metabolic activities of 5-10% compared to the control. This, together with the reduced specific growth rate in cells under osmotic stress, suggests that more energy was channelled into the biosynthetic pathway of Ig production.

Amino Acids↗
PubMed1994

Quantitation of interferon-induced Mx protein in whole blood lysates by an immunochemiluminescent assay: elimination of protease activity of cell lysates in toto.

Due to the rapidly expanding usage of interferons and its costliness of therapy, it is important to evaluate the clinical efficacy of the various interferons. Directly assaying circulating interferon is technically quite difficult. Here, we present an alternate method to evaluate interferon therapy by assaying a unique protein, called Mx protein, which is a 78 kDa cytoplasmic protein selectively induced by type-1 interferon in human leukocytes. The current assay is a two-site chemiluminescent immunoassay, designed to detect Mx protein in whole blood lysates. Since the Mx protein once solubilized, is highly susceptible to proteolysis in whole blood lysates, we have devised a new procedure both to maximize its solubility and virtually eliminate its proteolytic degradation. A mouse monoclonal antibody conjugated to the derivatized-paramagnetic particles and an acridinium ester-labeled antibody serve as the solid phase capture and detector antibodies, respectively. This assay is applicable to both manual and automated modes with a detection limit of Mx protein at 20 ng/ml whole blood. Availability of a reliable assay for Mx protein should facilitate the clinical evaluation of many of the newly constructed type-1 interferons.

Animals↗