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Biomedical subjects

S Ryu

Publications and source records attributed to S Ryu.

At least 19 recordsLinked to original sources

Genetic analysis of dopaminergic system development in zebrafish.

Zebrafish have become an important model organism to study the genetic control of vertebrate nervous system development. Here, we present an overview on the formation of dopaminergic neuronal groups in zebrafish and compare the positions of DA neurons in fish and mammals using the neuromere model of the vertebrate brain. Based on mutant analysis, we evaluate the role of several signaling pathways in catecholaminergic neuron specification. We further discuss the prospect of identifying novel genes involved in dopaminergic development through forward genetics mutagenesis screens.

Animals↗

Abdominal obesity, systolic blood pressure, and microalbuminuria in normotensive and euglycemic Korean men.

OBJECTIVES: To evaluate the relationship between abdominal obesity and microalbuminuria (MA) in normotensive, euglycemic Korean men. DESIGN: A cross-sectional study at a health screening center. SUBJECTS: A total of 1321 healthy, normotensive Korean men, aged 20-78 years, with a fasting plasma glucose level <100 mg/dl. MEASUREMENTS: Height, weight, and waist; systolic blood pressure (SBP); diastolic blood pressures (DBP); urinary albumin to creatinine ratio (ACR); fasting glucose, insulin, lipids, C-reactive protein (CRP), and white blood cell count. Waist circumference (WC) was used to indicate abdominal obesity and a single measurement of ACR was used to estimate MA. We also calculated body mass index (BMI) based on weight and height. RESULTS: Mean BMI, WC, and SBP were significantly higher in subjects with MA than in those without (24.8+/-4.1 vs 23.8+/-2.7 kg/m2, 86+/-9 vs 83+/-8 cm, and 115+/-5 vs 112+/-7 mmHg, respectively). Multiple logistic regression analyses showed that only WC and SBP were independent predictors of MA. CONCLUSION: WC and SBP were positively associated with MA in normotensive and euglycemic Korean men.

Abdominal Fat↗

Emergency department experience of primary diffusion weighted magnetic resonance imaging for the patient with lacunar syndrome.

BACKGROUND: The purpose of this study was to evaluate the usefulness of a particular magnetic resonance imaging technique known as primary diffusion weighted imaging (DWI) for patients with lacunar syndrome in the emergency department (ED). METHODS: Patients with one of five classic lacunar syndromes underwent DWI as primary imaging modality. The DWI findings were classified into groups: (a) having a lesion with high signal intensity, (b) having a lesion with mixed signal intensity, and (c) unremarkable. The final clinical diagnoses were extracted from the patients' medical records, and used as a reference standard. RESULTS: Of 151 DWI images, 120 (79%) were interpreted as high signal lesions, 21 (14%) as mixed signal lesions, and 10 (7%) as unremarkable. All patients with high signal lesions or unremarkable findings were diagnosed with ischaemic stroke. The patients with mixed signal lesions were diagnosed with haemorrhagic stroke with an exception of one ischaemic stroke. CONCLUSION: Primary DWI is a feasible and useful neuroimaging tool for patients with lacunar syndrome in the ED.

Adult↗

IL-17 increased the production of vascular endothelial growth factor in rheumatoid arthritis synoviocytes.

Interleukin-17 (IL-17) is a proinflammatory cytokine that is expressed in the synovium T cells of rheumatoid arthritis (RA). This cytokine is implicated in the inflammation and destruction of the joint. However, the role of IL-17 on the production of vascular endothelial factor (VEGF) important to synovial proliferation has still not been identified. In this study, we investigated the effect on cultured rheumatoid fibroblast-like synoviocytes (FLS) of the IL-17 on the production and expression of VEGF, which play an important role in angiogenesis in rheumatoid synovium. IL-17 increased the production of VEGF dose dependently and the mRNA expression of VEGF. These results suggest that IL-17 might influence angiogenesis in RA by up-regulating the expression of VEGF in rheumatoid FLS.

Arthritis, Rheumatoid↗

Correlation functions for inhomogeneous magnetic field in random media with application to a dense random pack of spheres.

In porous media subject to applied magnetic field, the internal field arises out of susceptibility contrast of the constituents. We have examined the spatial inhomogeneity of the internal fields in a random pack of spheres using numerical computation. We find that the pair-correlation function of the internal field (K2) is a close approximation to the structure factor of the material, thus K2 can be used to characterize pore geometry. The magnetic length scale LambdaM exhibited in K2 is shown to be related to the fluid transport in the medium.

Anisotropy↗

Cross-resistance between rifampicin and KRM-1648 is associated with specific rpoB alleles in Mycobacterium tuberculosis.

KRM-1648 resistant Mycobacterium tuberculosis strains were identified from a collection of rifampicin-resistant strains. Several strains had novel rpoB gene mutations in codons 512, 529 and 533 of the rpoB gene. The strains with mutations in codons 526 or 531, major mutation sites in rifampicin-resistant M. tuberculosis, were resistant to KRM-1648. Also, the strains with other mutations in the rpoB gene that were initially susceptible to KRM-1648 were prone to developing KRM-1648 resistance after further mutation. Thus, KRM-1648 is unlikely to be useful for the treatment of rifampicin-resistant tuberculosis.

Alleles↗

Enhanced apoptosis and radiosensitization by combined 13-cis-retinoic acid and interferon-alpha2a; role of RAR-beta gene.

PURPOSE: Combined use of 13-cis-retinoic acid (cRA) and interferon-alpha2a (IFNalpha) induced significant radiosensitization in human cervical cancer ME-180 cell line, whereas it failed to achieve similar radiation enhancement in HeLa cells. The differential radiosensitization could be from the difference of retinoic acid receptor (RAR) expression because RAR-beta was highly expressed in ME-180 cells in contrast to the HeLa cells where RAR-beta was not detectable. We examined the role of this gene in mediating radiosensitization by cRA and IFNalpha, and explored the mechanism of radiation-induced cell killing. METHODS AND MATERIALS: Human cervical cancer cell lines, ME-180 and HeLa, were treated with cRA and IFNalpha followed by radiation. Apoptosis and radiosensitization were quantitated by TUNEL assay (in situ DNA nick end labeling) and colony-forming ability of surviving cells. The cells were transfected with bcl-2 gene and RAR-beta gene to test the role of these genes in mediating radiosensitization and apoptosis. RESULTS: Synergistic radiosensitization and apoptosis was observed by combined use of cRA and IFNalpha with radiation in ME-180 cells which express high level of RAR-beta mRNA, whereas these were not seen in HeLa cells where RAR-beta mRNA is not detectable. Both radiosensitization and apoptosis were abolished by bcl-2 gene in ME-180 cells. RAR-beta gene transfection induced similar radiation enhancement and apoptosis in HeLa cells. CONCLUSION: Apoptosis and radiation response were enhanced in the cells with high level of RAR-beta mRNA expression. The RAR-beta gene appears to mediate the radiation-induced apoptosis by cRA and IFNalpha. These findings indicate that presence of RAR-beta in the cancer cells could be exploited for patient selection in using these drugs for apoptosis and radiosensitization.

Antineoplastic Agents↗

Identifying patients with gastroesophageal reflux disease in a managed care organization.

The ability of various strategies to identify patients with gastroesophageal reflux disease (GERD) and the relative economic impact on disease management programs for GERD were studied. A telephone interview was conducted of a random sample of patients enrolled in any of three health plans in a 100,000-member managed care organization who had either a pharmacy claim or an encounter claim during 1997. The telephone interview identified patients with GERD and served as the standard by which the sensitivity, specificity, and predictive values of the following patient-identification strategies were compared: (1) telephone interview, (2) chart review, (3) use of encounter claims, (4) use of pharmacy claims, (5) use of both encounter claims, and pharmacy claims, and (6) use of encounter claims or pharmacy claims. Conservative estimates of costs and projected savings were then used to model the potential return on investment of the strategies. A total of 1186 patients completed the telephone interview, of whom 390 (33%) met the case definition of GERD. The most sensitive method for identifying patients with GERD was using either pharmacy or encounter claims (26%). The most specific strategy with the highest positive predictive value (PPV) (87%) was using both pharmacy and encounter claims, but this approach had a case-detection rate of only 3%. Encounter claims were significantly more sensitive than pharmacy claims and yielded a higher estimate of prevalence. The telephone interview identified the most subjects who could have benefited from a disease management program and cost 84% less than chart review. While use of administrative data (pharmacy and encounter claims) was the least costly strategy, it identified 74% fewer patients expected to benefit from disease management. The efficiency of disease management programs for GERD may depend on the method of patient identification, which in turn may depend on whether PPV or negative predictive value (NPV) should be maximized. If there is a need to identify all cases (i.e., sensitivity and NPV are most important), then telephone interview may provide the greatest opportunity for disease management with the greatest return on investment, but at the expense of enrolling many patients who may not benefit.

Data Collection↗

Evidence for estradiol-induced apoptosis and dysregulated T cell maturation in the thymus.

In an attempt to delineate the immunological alterations that may occur following treatment with estrogen, groups of C57BL/6 mice were treated with 75mg/kg body weight of beta-estradiol-17-valerate (E2) or the vehicle. The thymus from these mice were harvested on days 1, 4 and 7 following treatment. The thymocytes from E2-treated mice when cultured in vitro for 24h, showed increased levels of apoptosis when compared to controls. The apoptosis was demonstrable by both TUNEL assay and AnnexinV/propidium iodide (PI) staining. Also, thymic atrophy and increased apoptosis of thymocytes when cultured in vitro were seen when lower doses of E2 (5mg/kg) were administered. The thymus from E2-treated mice on days 4 and 7 also showed a decrease in the percentage of CD4(+)CD8(+) (DP) T cells and an increase in the percentage of CD4(-)CD8(-) (DN), CD4(+) and CD8(+) T cells. However, the total cellularity of all T cell subsets in the thymus was decreased following E2 treatment. Earlier studies from our laboratory and elsewhere have demonstrated that in thymocytes undergoing apoptosis, there is increased expression of surface markers including CD3, alphabetaTCR and CD44 with a simultaneous decrease in the expression of J11d. Similar changes were observed in thymocytes from mice on days 4 and 7 following E2 treatment. These data therefore confirmed that the thymocytes were indeed undergoing apoptosis following E2 treatment. Together, our studies suggest for the first time that estrogen may induce thymic atrophy by triggering apoptosis.

Animals↗

Heat shock RNA polymerase (E sigma(32)) is involved in the transcription of mlc and crucial for induction of the Mlc regulon by glucose in Escherichia coli.

Mlc is a global regulator of carbohydrate metabolism. Recent studies have revealed that Mlc is depressed by protein-protein interaction with enzyme IICB(Glc), a glucose-specific permease, which is encoded by ptsG. The mlc gene has been previously known to be transcribed by two promoters, P1(+1) and P2(+13), and have a binding site of its own gene product at +16. However, the mechanism of transcriptional regulation of the gene has not yet been established. In vitro transcription assays of the mlc gene showed that P2 promoter could be recognized by RNA polymerase containing the heat shock sigma factor final sigma(32) (E sigma(32)) as well as E sigma(70), while P1 promoter is only recognized by E sigma(70). The cyclic AMP receptor protein and cyclic AMP complex (CRP.cAMP) increased expression from P2 but showed negative effect on transcription from P1 by E sigma(70), although it had little effect on transcription from P2 by E sigma(32) in vitro. Purified Mlc repressed transcription from both promoters, but with different degrees of inhibition. In vivo transcription assays using wild type and mlc strains indicated that the level of mlc expression was modulated less than 2-fold by glucose in the medium with concerted action of CRP.cAMP and Mlc. A dramatic increase in mlc expression was observed upon heat shock or in cells overexpressing final sigma(32), confirming that E sigma(32) is involved in the expression of mlc. Induction of ptsG P1 and pts P0 transcription by glucose was also dependent on E sigma(32). These results indicate that E sigma(32) plays an important role in balancing the relative concentration of Mlc and EIICB(Glc) in response to availability of glucose in order to maintain inducibility of the Mlc regulon at high growth temperature.

Bacterial Proteins↗

A 2.1 A resolution structure of an uncleaved alpha(1)-antitrypsin shows variability of the reactive center and other loops.

Serpin (serine protease inhibitor) proteins are involved in diverse physiological processes including inflammation, coagulation, matrix remodeling, and cell differentiation. Deficiency of normal serpin functions leads to various hereditary diseases. Besides their clinical importance, serpin proteins draw much attention due to the large conformational changes that occur upon interaction with proteases. We present here the crystal structure of an uncleaved alpha(1)-antitrypsin determined by the multiple isomorphous replacement method and refined to 2.1 A resolution. The structure, which is the first active serpin structure based on experimental phases, reveals novel conformations in the flexible loops, including the proximal hinge region of the reactive center loop and the surface cavity region in the central beta-sheet, sheet A. The determined loop conformation explains the results of recent mutagenesis studies and provides detailed insights into the protease inhibition mechanism. The high-resolution structure of active alpha(1)-antitrypsin also provides evidence for the existence of localized van-der-Waals strain in the central hydrophobic core.

Amino Acid Sequence↗

The Escherichia coli glucose transporter enzyme IICB(Glc) recruits the global repressor Mlc.

In addition to effecting the catalysis of sugar uptake, the bacterial phosphoenolpyruvate:sugar phosphotransferase system regulates a variety of physiological processes. Exposure of cells to glucose can result in repression or induction of gene expression. While the mechanism for carbon catabolite repression by glucose was well documented, that for glucose induction was not clearly understood in Escherichia coli. Recently, glucose induction of several E.coli genes has been shown to be mediated by the global repressor Mlc. Here, we elucidate a general mechanism for glucose induction of gene expression in E.coli, revealing a novel type of regulatory circuit for gene expression mediated by the phosphorylation state-dependent interaction of a membrane-bound protein with a repressor. The dephospho-form of enzyme IICB(Glc), but not its phospho-form, interacts directly with Mlc and induces transcription of Mlc-regulated genes by displacing Mlc from its target sequences. Therefore, the glucose induction of Mlc-regulated genes is caused by dephosphorylation of the membrane-bound transporter enzyme IICB(Glc), which directly recruits Mlc to derepress its regulon.

Bacterial Proteins↗

Dopamine transporter expression distinguishes dopaminergic neurons from other catecholaminergic neurons in the developing zebrafish embryo.

To characterize the formation of the dopaminergic system in the developing zebrafish CNS, we cloned cDNAs encoding tyrosine hydroxylase (th), an enzyme in dopamine synthesis, and the dopamine transporter (dat), a membrane transport protein which terminates dopamine action by re-uptake. Dopaminergic neurons are first detected between 18 and 19 h post-fertilization in a cluster of cells in the ventral diencephalon. Subsequently, th and dat detection identifies dopaminergic neurons in the olfactory bulb, the pretectum, the retina and the locus coeruleus. Neurons expressing th but not dat are adrenergic or noradrenergic, and are found in the locus coeruleus, the medulla, the likely analog of the carotid body, and precursors of the enteric and sympathetic nervous system.

Amino Acid Sequence↗

Decreased circulating levels of estrogen alter vaginal and clitoral blood flow and structure in the rabbit.

Aging and menopause related decline in circulating levels of estrogen has been shown to adversely affect female sexual arousal function. Our aim was to study the effects of circulating levels of estrogen on the hemodynamic mechanism of vaginal and clitoral engorgement and on the structure of the vaginal and clitoral cavernosal tissue in the rabbit. New Zealand White female rabbits (3.5-4 kg) were randomly divided into three groups with five rabbits in each group: control; bilateral oophorectomy; bilateral oophorectomy undergoing subcutaneous injection of estrogen (40 microg/kg/day). After 6 weeks, the serum levels of 17 beta-estradiol were measured and systemic blood pressure was monitored. Vaginal and clitoral cavernosal blood flows were measured with laser Doppler flowmeter before and after pelvic nerve stimulation. Cross sections of the clitoris and vagina were processed for histologic examination and histomorphometric image analysis. Serum level of 17 beta-estradiol (pg/ml; mean+/-s.d.) revealed a significant decrease in the oophorectomy group (25.4+/-5.1) compared with the control (38.5+/-7.6) and estrogen replacement (115.9+/-57.3) groups (P<0.05). Nerve stimulation-induced peak vaginal and clitoral intracavernosal blood flows in the oophorectomy group (28.9+/-16.3 and 6.1+/-1.4, respectively) were significantly less than those recorded in the control (48.9+/-6.5 and 11.0+/-2.4, respectively) or estrogen replacement (48.7+/-12.2 and 10.1+/-2.8, respectively) group (P<0.05). In histology, marked thinning of the vaginal epithelial layers, decreased vaginal submucosal microvasculature, and diffuse clitoral cavernosal fibrosis were evident in the oophorectomy group but not in the estrogen supplement and control groups. In histomorphometry, the percentage of clitoral cavernosal smooth muscle in the oophorectomy group (49.6+/-6.2) was significantly decreased compared with the control (56.8+/-2.6) and estrogen replacement (58+/-3.0) groups (P<0.05). Our studies show that decline in circulating levels of estrogen impairs the hemodynamic mechanism of vaginal and clitoral engorgement and leads to histopathologic changes in the vagina and clitoral cavernosal tissue. These observations suggest that decreased circulating levels of estrogen, a physiologic change in the menopausal state, may play a role in the development of female sexual arousal dysfunction.

Animals↗

Alteration of a single amino acid changes the substrate specificity of dihydroflavonol 4-reductase.

Many plant species exhibit a reduced range of flower colors due to the lack of an essential gene or to the substrate specificity of a biosynthetic enzyme. Petunia does not produce orange flowers because dihydroflavonol 4-reductase (DFR) from this species, an enzyme involved in anthocyanin biosynthesis, inefficiently reduces dihydrokaempferol, the precursor to orange pelargonidin-type anthocyanins. The substrate specificity of DFR, however, has not been investigated at the molecular level. By analyzing chimeric DFRs of Petunia and Gerbera, we identified a region that determines the substrate specificity of DFR. Furthermore, by changing a single amino acid in this presumed substrate-binding region, we developed a DFR enzyme that preferentially reduces dihydrokaempferol. Our results imply that the substrate specificity of DFR can be altered by minor changes in DFR.

Alcohol Oxidoreductases↗

gly gene cloning and expression and purification of glycinecin A, a bacteriocin produced by Xanthomonas campestris pv. glycines 8ra.

Glycinecin A, a bacteriocin produced by Xanthomonas campestris pv. glycines, inhibits the growth of X. campestris pv. vesicatoria. We have cloned and expressed the genes encoding glycinecin A in Escherichia coli. Recombinant glycinecin A was purified from cell extracts by ammonium sulfate precipitation followed by chromatography on Q-Sepharose, Mono Q (ion exchange), and size exclusion columns. Purified glycinecin A is composed of two polypeptides, is active over a wide pH range (6 to 9), and is stable at temperatures up to 60 degrees C. Glycinecin A is a heterodimer consisting of 39- and 14-kDa subunits, as revealed through size exclusion chromatography and cross-linking analysis. Two genes, glyA and glyB, encoding the 39- and 14-kDa subunits, respectively, were identified based on the N-terminal sequences of the subunits. From the nucleotide sequences of glyA and glyB, we conclude that both genes are translated as bacteriocin precursors that include N-terminal leader sequences. When expressed in E. coli, recombinant glycinecin A was found primarily in cell extracts. In contrast, most glycinecin A from Xanthomonas was found in the culture media. E. coli transformed with either glyA or glyB separately did not show the bacteriocin activity.

Bacteriocins↗

Reversal of established autoimmune diabetes by restoration of endogenous beta cell function.

In NOD (nonobese diabetic) mice, a model of autoimmune diabetes, various immunomodulatory interventions prevent progression to diabetes. However, after hyperglycemia is established, such interventions rarely alter the course of disease or allow sustained engraftment of islet transplants. A proteasome defect in lymphoid cells of NOD mice impairs the presentation of self antigens and increases the susceptibility of these cells to TNF-alpha-induced apoptosis. Here, we examine the hypothesis that induction of TNF-alpha expression combined with reeducation of newly emerging T cells with self antigens can interrupt autoimmunity. Hyperglycemic NOD mice were treated with CFA to induce TNF-alpha expression and were exposed to functional complexes of MHC class I molecules and antigenic peptides either by repeated injection of MHC class I matched splenocytes or by transplantation of islets from nonautoimmune donors. Hyperglycemia was controlled in animals injected with splenocytes by administration of insulin or, more effectively, by implantation of encapsulated islets. These interventions reversed the established beta cell-directed autoimmunity and restored endogenous pancreatic islet function to such an extent that normoglycemia was maintained in up to 75% of animals after discontinuation of treatment and removal of islet transplants. A therapy aimed at the selective elimination of autoreactive cells and the reeducation of T cells, when combined with control of glycemia, is thus able to effect an apparent cure of established type 1 diabetes in the NOD mouse.

Adoptive Transfer↗

T wave alternans for predicting adverse effects of amiodarone in a patient with dilated cardiomyopathy.

An implantable cardioverter defibrillator (ICD) was used in a 62-year-old man with dilated cardiomyopathy (DCM) because of hemodynamically intolerable ventricular tachycardia (VT). Amiodarone was administered after a second episode of ICD discharge. Three weeks later, incessant VT appeared, and DC discharge failed to terminate it. Microvolt T wave alternans (TWA), measured by a spectral method, was observed in this patient with and without amiodarone administration. The onset heart rate with TWA was lower and the alternans voltage was higher with amiodarone than without it. The effects of amiodarone appeared to be related to the exacerbation of VT and an increased defibrillation threshold. TWA might be useful in predicting the proarrhythmic effects of amiodarone in similar cases.

Amiodarone↗