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Biomedical subjects

S Cho

Publications and source records attributed to S Cho.

At least 127 records · Page 7Linked to original sources
PubMed1998

Nicardipine normalizes elevated levels of antioxidant activity in response to xanthine oxidase-induced oxidative stress in hypertensive rat heart.

It has been reported that the production of oxygen radicals mediated by xanthine oxidase (XO) is stimulated in hypertensive cardiovascular endothelium, suggesting involvement of oxidative stress in pathogenesis of hypertension. In this study we estimated the effect of nicardipine, a calcium blocker, on the oxidative stress and antioxidant activities in left ventricles from spontaneously hypertensive rat (SHR) and stroke-prone SHR (SHRSP). The activity of XO increased 3.5-fold in SHR and 6.2-fold in SHRSP compared to that in normal controls (WKY). Interestingly, the levels of glutathione (GSH) and the activity of its synthesizing enzyme (gamma-glutamylcysteine synthetase, gamma-GCS) elevated concomitantly in SHR and SHRSP: the level of GSH increased 1.2-fold in SHR and 1.3-fold in SHRSP. The activity of gamma-GCS was elevated 1.5-fold in SHR and 2.4-fold in SHRSP, accompanying an increase in the expression of its mRNA. Treatment of these rats with nicardipine, for 4 weeks improved blood pressure, from 176 +/- 10 to 140 +/- 8 mmHg in SHR, and from 201 +/- 11 to 167 +/- 5 mmHg in SHRSP, respectively, and decreased wet weight of heart, levels of GSH, and the activities of XO and gamma-GCS. Nicardipine reduced the expression of gamma-GCS mRNA. Collectively, these results suggest that reactive oxygen species produced by XO in hypertensive rat heart cause induction of the expression of gamma-GCS and nicardipine plays a role in reducing the oxidative stress in hypertensive heart.

Animals↗
PubMed1998

The role of alpha1-adrenoceptors in the clonidine-induced contraction and relaxation of rat aorta.

Clonidine causes dilatation of the aorta in the presence of endothelium, while it causes contraction of the aorta in the absence of endothelium. The present study was carried out to clarify the role of alpha-1-adrenoceptors in the vascular action of clonidine. The aortic rings were suspended in Krebs-Henseleit (K-H) medium, and the effects of alpha-1- and alpha-2-adrenoceptor antagonists on the clonidine-induced contractions were measured. Moreover, the role of the phosphatidylinositol (PI) response was examined. The aortic slices were incubated in K-H medium containing, [3H]myo-inositol and clonidine. The formation of [3H]inositol monophosphate (IP1) was measured with a liquid scintillation counter. Clonidine caused contraction of the aorta in the absence of endothelium, in a dose-dependent manner. This contraction was inhibited by antagonists in the following order of the potency: prazosin > phentolamine > spiperone > urapidil = yohimbine > L-659066 > atipamezole. On the other hand, clonidine inhibited norepinephrine (NE)-induced contraction in the aorta in the absence and in the presence of endothelium. Clonidine enhanced IP1 accumulation in the aorta in the absence of endothelium, whereas it inhibited NE-induced IP1 accumulation in the aorta. The present results show that alpha-1-adrenoceptors are probably involved in the clonidine-induced contraction and relaxation of the rat aorta.

Adrenergic alpha-1 Receptor Agonists↗
PubMed1998

Standardization of the nationwide health examination in Korea.

The Korea Medical Insurance Corporation has held the periodic Health Examination for the public servants and teachers from 1977 as a nationwide health preventive task. But the Health Examination result is not computerized rather than paperwork, so the use of the Health Examination is limited and the results of Health Examination can not be stored or interchangeable between hospitals or health examination centers in this system. So we planed the Standardization of the Nationwide Health Examination project and developed the Health Examination computer program in 1996. The object of standardized program is to contribute to cost-effective analysis of each item or other studies about the factors influences development of diseases. And now, an Exhibition work for the standardization is being held with the Health Examination computer program. At the ending of the Exhibition work, we will evaluation and revision the computerized program for standardization process.

Computer Systems↗
PubMed1998

Information system for a periodic examination and health promotion center.

The periodic examination and health promotion center (PEHPC) in Seoul National University Hospital has developed and adopted an information system supported by computers which use an electronic medical record to improve the quality of patient care, advance the science of medicine, lower health care costs, and enhance the education of health care professionals. This information system adopted the concept of incomplete and evolutionary systems to conduct the pursuit of practicalness and efficacy. It has increased efficiency to save costs and to enhance the quality of the medical service. It has also activated clinical research due to ease of managing data. We are also preparing for telecare. Telecare and WWW-using information system is postponed because the protection of a patients privacy is not established.

Ambulatory Care Facilities↗
PubMed1998

[Energy expenditure in patients with pulmonary emphysema].

We evaluated resting energy expenditure (REE) using canopy mode indirect calorimetry in 21 ambulatory, clinically stable outpatients with pulmonary emphysema (age: 69.3 +/- 8.4, %IBW: 79.3 +/- 12.5, FEV1: 0.98 +/- 0.36) and compared it with that of a 14 age-matched healthy controls (age: 71.1 +/- 6.0, %IBW: 94.5 +/- 13.4). We also compared REE in malnourished patients (%IBW < 90; 73.0 +/- 7.6, N = 14) and normonourished patients (%IBW > or = 90; 92.0 +/- 5.6, N = 7). We examined the relation ship between %REE (REE/REEpred. x 100) and measurements of lung function tests in 21 emphysema patients using single regression analysis. The REE of the patient group was significantly higher than that of the control group (%REE; 115.9 +/- 12.0 vs 86.5 +/- 8.7, p < 0.01). The REE of the malnourished patient subgroup was significantly higher than that of the normonourished patient subgroup (%REE; 121.9 +/- 7.9 vs 109.9 +/- 9.2, p < 0.01). There were no significant differences in FEV1(L), RV/TLC(%), TLC(pred.%) or DLco/VA (pred.%) between the two patient subgroups. The REE of the normonourished subgroup was significantly higher than that of control group (%REE; 109.1 +/- 9.2 vs 86.5 +/- 8.7, p < 0.01). There were significant relations hips among %REE and FEV1, %FVC, FEV1% G, %DLco/VA and RV/TLC (p < .05). These findings suggest that elevated REE may have a significant relation ship with abnormal lung function, and that elevated REE may be a cause of malnutrition in clinically stable patients with pulmonary emphysema.

Aged↗
PubMed1998

Digital dynamic telepathology--the Virtual Microscope.

The Virtual Microscope is being designed as an integrated computer hardware and software system that generates a highly realistic digital simulation of analog, mechanical light microscopy. We present our work over the past year in meeting the challenges in building such a system. The enhancements we made are discussed, as well as the planned future improvements. Performance results are provided showing the system scales well, so that many users can be adequately serviced by an appropriately configured data server.

Computers↗
PubMed1997

Evidence for autocrine inhibition of gonadotropin-releasing hormone (GnRH) gene transcription by GnRH in hypothalamic GT1-1 neuronal cells.

To examine whether an ultrashort feedback mechanism of gonadotropin-releasing hormone (GnRH) operates at the level of gene transcription, we studied the effects of GnRH analogs on GnRH promoter activity and GnRH mRNA level in hypothalamic GT1-1 neuronal cells. Treatment of GT1-1 cells with buserelin, a GnRH agonist, or native GnRH for 24 h significantly decreased GnRH promoter activity and its mRNA level, whereas that with GnRH antagonists, antide or [D-Phe2,D-Ala6]-GnRH, showed no effect. The inhibitory effects of buserelin on GnRH gene transcription and GnRH mRNA level were dose-related, and a significant inhibition was observed in cells treated with buserelin at concentrations higher than 0.1 microM. Time-course experiments showed that significant decreases in GnRH promoter-driven luciferase activity and GnRH mRNA level were observed within 12 h and sustained up to 48 h. Moreover, treatment with GnRH agonist for 12 h significantly decreased the transcription rate of the mouse GnRH gene, as revealed by nuclear run-on transcription assay. The promoter analysis with the 5'-deletional constructs demonstrated that cis-acting elements important for GnRH autoregulation by GnRH agonist reside within -854 bp upstream from the transcription start site. These data clearly demonstrate that GnRH can exert autocrine regulation at the level of GnRH gene transcription.

Animals↗
PubMed1997

The crystal structure of an Fe-superoxide dismutase from the hyperthermophile Aquifex pyrophilus at 1.9 A resolution: structural basis for thermostability.

Superoxide dismutase (SOD) from Aquifex pyrophilus, a hyperthermophilic bacterium, is an extremely heat-stable enzyme that maintains about 70% of its activity after heat treatment for 60 minutes at 100 degrees C. To understand the molecular basis of thermostability of this enzyme, we have determined the crystal structure of A. pyrophilus superoxide dismutase (Ap SOD), an Fe containing homotetrameric enzyme, at 1.9 A resolution, and compared it with SOD structures from a mesophile and a thermophile, and other enzyme structures from other hyperthermophiles. The structure has been refined to a crystallographic R-factor (I > 2sigma) of 17.0% and R-free (I > 2sigma) of 19.9%. While the overall structure of the Ap SOD monomer is similar to the other SODs, significant conformational differences are observed in a highly variable loop region and the C-terminal helix. The conformational differences in these regions alter the subunit arrangement of this enzyme and generate a very compact tetramer. Structural comparisons of three SODs have revealed that Ap SOD has some stabilizing features at both the tertiary and the quaternary structural level: The Ap SOD monomer contains a large number of ion-pairs and the Ap SOD tetramer has a dramatically increased buried surface area per monomer. Comparisons of the Ap SOD structure with that of other known enzymes from hyperthermophiles reveal that the increased number of intrasubunit ion-pairs is a common feature.

Amino Acid Sequence↗
PubMed1997

Differential effects of cytolytic T cell subsets on intracellular infection.

In analyzing mechanisms of protection against intracellular infections, a series of human CD1-restricted T cell lines of two distinct phenotypes were derived. Both CD4(-)CD8(-) (double-negative) T cells and CD8(+) T cells efficiently lysed macrophages infected with Mycobacterium tuberculosis. The cytotoxicity of CD4(-)CD8(-) T cells was mediated by Fas-FasL interaction and had no effect on the viability of the mycobacteria. The CD8(+) T cells lysed infected macrophages by a Fas-independent, granule-dependent mechanism that resulted in killing of bacteria. These data indicate that two phenotypically distinct subsets of human cytolytic T lymphocytes use different mechanisms to kill infected cells and contribute in different ways to host defense against intracellular infection.

Antigens, CD1↗
PubMed1997

Melatonin administration protects CA1 hippocampal neurons after transient forebrain ischemia in rats.

Melatonin administered at the beginning of cerebral reperfusion protected CA1 neurons against 10, 20 and 30 min of transient forebrain ischemia. Intraperitoneal injections of saline or melatonin (10 mg/kg) were given after 0, 2 and 6 h, or 1, 2 and 6 h of cerebral reperfusion, or 30 min prior to ischemia. One week later, quantitative histological analysis demonstrated that CA1 neuronal density was significantly increased in the melatonin groups that were treated at 0, 2, 6 h compared to the saline-treated controls. Ischemic protection of CA1 was lost in the animals in which the melatonin treatment was delayed by 1 h, or given 30 min prior to the ischemia.

Analysis of Variance↗
PubMed1997

Incidence and impact on outcome of streptokinase allergy in the GUSTO-I trial. Global Utilization of Streptokinase and t-PA in Occluded Coronary Arteries.

We evaluated allergic reactions in 20,201 patients randomized to the streptokinase arms of The Global Utilization of Streptokinase and t-PA (Tissue Plasminogen Activator) in Occluded Coronary Arteries (GUSTO-I) trial, and tested the hypothesis that patients with streptokinase allergy would exhibit higher mortality. After adjusting for baseline variables and time of death, we found comparable coronary patency, left ventricular function, mortality, and bleeding complications between patients with versus those without streptokinase allergy.

Anaphylaxis↗
PubMed1997

Regulation of tyrosine hydroxylase and aromatic L-amino acid decarboxylase by dopaminergic drugs.

We provide evidence that dopamine receptors differentially modulate tyrosine hydroxylase and aromatic L-amino acid decarboxylase in the mouse striatum. The dopamine D1 receptor family (D1-like) antagonist, R(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1 H-3-benazepine (SCH 23390), elevated aromatic L-amino acid decarboxylase activity and protein content in striatum, as well as the mRNA for the enzyme in midbrain. The dopamine D1-like receptor agonist, (+/-)-1-phenyl-2,3,4,5-tetrahydro-(1 H)-3-benzazepine-7,8-diol (SKF 38393), had no effect on aromatic L-amino acid decarboxylase. The dopamine D1-like drugs had no effect on tyrosine hydroxylase. In contrast, the dopamine D2 receptor family (D2-like) antagonists haloperidol and spiperone elevated both tyrosine hydroxylase and aromatic L-amino acid decarboxylase activities. The increase in aromatic L-amino acid decarboxylase activity was accompanied by elevated enzyme protein content but not mRNA. The dopamine D2-like receptor agonists, bromocriptine, quinpirole and (+/-)-7-hydroxydipropylaminotetralin (7-OH-DPAT), all decreased striatal tyrosine hydroxylase. Under the conditions used, bromocriptine and 7-OH-DPAT, but not quinpirole, decreased aromatic L-amino acid decarboxylase activity of striatum. Both the dopamine D1- and D2-like receptor antagonists enhanced the turnover of striatal dopamine to differing degrees, as judged by the ratio of acid metabolites of dopamine to dopamine. Taken together our results indicate that aromatic L-amino acid decarboxylase can be modulated independently of tyrosine hydroxylase.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1997

Exploration of the action pattern of Streptomyces hyaluronate lyase using high-resolution capillary electrophoresis.

Hyaluronic acid was treated exhaustively with a hyaluronate lyase (hyaluronidase, EC 4.2.2.1) from Streptomyces hyalurolyticus to obtain a tetrasaccharide and a hexasaccharide product in a molar ratio of 1 to 1.2. The tetrasaccharide product was fluorescently labeled at the reducing end by reductive amination with 7-amino 1,3-naphthalene disulfonic acid (AGA) and the structure of the conjugate was determined spectroscopically. Partial treatments of hyaluronic acid with hyaluronate lyase afforded complex mixtures of oligosaccharides that were similarly fluorescently labeled. These labeled oligosaccharide mixtures were analyzed using high-resolution capillary electrophoresis. The resulting electropherograms showed the content of each hyaluronic acid derived oligosaccharide, having a degree of polymerization (dp) from 4 to 50, throughout the enzymatic reaction. Computer simulation studies gave comparable kinetic profiles suggesting that hyaluronate lyase exhibits a random endolytic action pattern. Interestingly, oligosaccharides of certain size (dp) were under-represented in these oligosaccharide mixtures suggesting that linkages at spacings of 10 to 12 saccharide units are somewhat resistant to this enzyme. The cause of this resistance might be the result of secondary or higher order structural features present in the hyaluronic acid polymer.

Carbohydrate Sequence↗
PubMed1997

DNA binding by the male and female doublesex proteins of Drosophila melanogaster.

Drosophila yolk protein genes are regulated by doublesex male protein (DSXM) in males and doublesex female protein (DSXF) in females. Both proteins bind to the same DNA sites from which DSXM represses and DSXF activates transcription. The proteins are identical through 397 NH2-terminal amino acids that include domains for oligomerization and DNA binding. The remaining COOH termini are sex-specific and include an essential part of a second oligomerization domain. We report here mobility shift assays that examine the DNA binding properties of purified DSXM and DSXF. Dimers of DSXM and DSXF bind to a regulatory site, dsxA, with the same affinity (Kapp = 0.2 nM), specificity (specific/nonspecific approximately 1.2 x 10(4)), and dependence on monovalent and divalent cations. The DNA association rate constants also are indistinguishable (kon = 4.6 x 10(6) M-1 s-1) as are the several terms of the dissociation reaction. Dissociation has an intrinsic rate of koff = 5.1 x 10(-4) s-1 and other rate terms that depend on the free concentration of specific DNA binding sites (2.4 x 10(4) M-1 s-1) or nonspecific binding sites (2.4 M-1 s-1). This first order dependence on unbound DNA suggests that a direct transfer between DNAs is likely to occur when DSX proteins search for specific sites in the many short open DNA regions of chromatin. Overall, dimer binding to individual DNA sites appears to be determined by the sex-nonspecific part of the two proteins. We infer that the sex-specific oligomerization domains play roles in binding cooperativity to multiple DNA sites or in other protein:protein interactions.

Animals↗
PubMed1997

Structure-activity relationships of selective estrogen receptor modulators: modifications to the 2-arylbenzothiophene core of raloxifene.

The 2-arylbenzothiophene raloxifene, 1, is a selective estrogen receptor modulator which is currently under clinical evaluation for the prevention and treatment of postmenopausal osteoporosis. A series of raloxifene analogs which contain modifications to the 2-arylbenzothiophene core have been prepared and evaluated for the ability to bind to the estrogen receptor and inhibit MCF-7 breast cancer cell proliferation in vitro. Their ability to function as tissue-selective estrogen agonists in vivo has been assayed in a short-term, ovariectomized (OVX) rat model with end points of serum cholesterol lowering, uterine weight gain, and uterine eosinophil peroxidase activity. These studies have demonstrated that (1) the 6-hydroxy and, to a lesser extent, the 4'-hydroxy substituents of raloxifene are important for receptor binding and in vitro activity, (2) small, highly electronegative 4'-substituents such as hydroxy, fluoro, and chloro are preferred both in vitro and in vivo, (3) increased steric bulk at the 4'-position leads to increased uterine stimulation in vivo, and (4) additional substitution of the 2-aryl moiety is tolerated while additional substitution at the 4-, 5-, or 7-position of the benzothiophene results in reduced biological activity. In addition, compounds in which the 2-aryl group is replaced by alkyl, cycloalkyl, and naphthyl substituents maintain a profile of in vitro and in vivo biological activity qualitatively similar to that of raloxifene. Several novel structural variants including 2-cyclohexyl, 2-naphthyl, and 6-carbomethoxy analogs also demonstrated efficacy in preventing bone loss in a chronic OVX rat model of postmenopausal osteopenia, at doses of 0.1-10 mg/kg.

Adenocarcinoma↗
PubMed1997

Prevalence of spinal disc disease among interventional cardiologists.

A suspected, but undocumented, excess of axial skeletal disease among interventional cardiologists (possibly a consequence of lead apron use) was investigated by comparing questionnaire responses from cardiologists, orthopedic surgeons, and rheumatologists (n = 714). Cardiologists reported more neck and back pain, more subsequent time lost from work, and a higher incidence of cervical disc herniations, as well as multiple level disc disease (all p <0.01): "interventionalist's disc disease" is a confirmed entity.

Adult↗
PubMed1997

Establishing norms for age-related changes in proton T1 of human brain tissue in vivo.

The goal of this study was to determine the expected normal range of variation in spin-lattice relaxation time (T1) of brain tissue in vivo, as a function of age. A previously validated precise and accurate inversion recovery method was used to map T1 transversely, at the level of the basal ganglia, in a study population of 115 healthy subjects (ages 4 to 72; 57 male and 58 female). Least-squares regression analysis shows that T1 varied as a function of age in pulvinar nucleus (R2 = 56%), anterior thalamus (R2 = 51%), caudate (R2 = 50%), frontal white matter (R2 = 47%), optic radiation (R2 = 39%), putamen (R2 = 36%), genu (R2 = 22%), occipital white matter (R2 = 20%) (all p < 0.0001), and cortical gray matter (R2 = 53%) (p < 0.001). There were no significant differences in T1 between men and women. T1 declines throughout adolescence and early adulthood, to achieve a minimum value in the fourth to sixth decade of life, then T1 begins to increase. Quantitative magnetic resonance imaging provides evidence that brain tissue continues to change throughout the lifespan among healthy subjects with no neurologic deficits. Age-related changes follow a strikingly different schedule in different brain tissues; white matter tracts tend to reach a minimum T1 value, and to increase again, sooner than do gray matter tracts. Such normative data may prove useful for the early detection of brain pathology in patients.

Adolescent↗