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Biomedical subjects

J Ko

Publications and source records attributed to J Ko.

At least 19 recordsLinked to original sources
PubMed2006

ICA and water in Korea--overview.

The natural water quality in Korea has improved significantly in the last 20 years since major collective national initiatives were implemented by governmental agencies, non-governmental organizations, and professionals among many others. Recently instrumentation, control, and automation (ICA) technology has become one of the most important technologies for carrying out this task. Korea has become especially well known with a strong reputation for information technology and international business with commercial products like semi-conductors, computers, mobile phones, computer games, and other electronic products. In this paper the background of Korean water quality is reviewed and several of the most significant national projects related to ICA are discussed. The major projects may include the Automatic Monitoring Network of River Water Quality and the Integrated Management System of Wastewater Treatment Plants in Upper Basin Area of Multi-purpose Dams.

Automation↗
PubMed2006

Comparison of sevoflurane and isoflurane in domestic ferrets (Mustela putorius furo).

Isoflurane anesthesia is commonly used in ferrets for routine examinations and diagnostics. Sevoflurane is now being used as well, but there have been no studies to date directly comparing these agents in domestic ferrets. A prospective study was designed to evaluate the quality and speed of anesthetic induction and recovery using isoflurane and sevoflurane in ferrets. In addition effects on heart rate, blood pressure and packed cell volume were also recorded. No significant differences were noted between anesthetic agents.

Anesthetics, Inhalation↗
PubMed2004

Laser pediatric Class II composites utilizing no anesthesia.

Interproximal lesions can now be restored without local anesthesia and removing unnecessary healthy tooth structure. This paper will focus on a new ultra-conservative technique in Class II composites utilizing the laser, a new technique in cavity preparation.

Anesthesia, Dental↗
PubMed2002

Evaluation of several respirometry-based activated sludge toxicity control strategies.

Four different strategies including influent storage and reintroduction, step-feeding, rapid sludge recycle and waste sludge storage were evaluated using the denitrification layout of the IWA simulation benchmark. The control objective was to minimise deterioration in effluent quality caused by a certain toxic input event. In these strategies the maximum specific respiration rate (Rmax) was selected as a measured and controlled variable. To simplify the analysis, the toxicant was assumed to be a soluble and nonbiodegradable substance. Two toxic influent files were developed with square-wave input lasting 3 hours. To detect the influent toxicity, a pseudo-online flow-through respirometer was applied. A number of simulations were performed and the results suggested that the influent storage and reintroduction strategy provided the most optimistic results and other strategies could not mitigate the toxic effect. The influent storage and reintroduction strategy strongly depended on reintroduction flow rate from the storage tank. The simulation according to reintroduction flow could estimate the time required for completely treating toxic wastewater stored in the storage tank. Also the IWA simulation benchmark was enhanced to evaluate toxicity effect on the activated sludge process.

Benchmarking↗
PubMed2002

Genetic algorithms for the application of Activated Sludge Model No. 1.

The genetic algorithm (GA) has been integrated into the IWA ASM No. 1 to calibrate important stoichiometric and kinetic parameters. The evolutionary feature of GA was used to configure the multiple local optima as well as the global optimum. The objective function of optimization was designed to minimize the difference between estimated and measured effluent concentrations at the activated sludge system. Both steady state and dynamic data of the simulation benchmark were used for calibration using denitrification layout. Depending upon the confidence intervals and objective functions, the proposed method provided distributions of parameter space. Field data have been collected and applied to validate calibration capacity of GA. Dynamic calibration was suggested to capture periodic variations of inflow concentrations. Also, in order to verify this proposed method in real wastewater treatment plant, measured data sets for substrate concentrations were obtained from Haeundae wastewater treatment plant and used to estimate parameters in the dynamic system. The simulation results with calibrated parameters matched well with the observed concentrations of effluent COD.

Algorithms↗
PubMed2001

Self-assembly of one-dimensional coordination polymers from AgX (X = CF(3)SO(3)(-), ClO(4)(-), and NO(3)(-)) and 2-aminomethylpyridinedipropionitrile (2-AMPDPN).

Three novel supramolecules whose topologies depend on the counteranion, [Ag(2-AMPDPN)X] (X = CF(3)SO(3)(-) (1), ClO(4)(-) (2), and NO(3)(-) (3)), have been prepared by the self-assembly of AgX (X = CF(3)SO(3)(-), ClO(4)(-), and NO(3)(-)) with 2-aminomethylpyridinedipropionitrile (2-AMPDPN). The crystal structures reveal different packing arrangements of the one-dimensional infinite coordination polymers. Compound 1 is made up of ladder chains that are interlocked by cyano groups, while the polymeric chain of 2 is isomorphous to 1 except for the Ag-Ag interaction. Compound 3 consists of helical chains that are surrounded by nitrate. The adjacent helical chains are racemic. The structures of 1, 2, and 3 suggest the role that the counterions may play in the network construction.

Journal Article↗
PubMed2001

Identification of a structural motif of 23S rRNA interacting with 5S rRNA.

To identify RNA motifs interacting with 5S rRNA, a systematic evolution of ligands by exponential enrichment experiment was applied. Some of the resulting RNA aptamers contained a consensus sequence similar to the sequence in the loop region of helix 89 of 23S rRNA. We show that the synthetic helix 89 RNA motif indeed interacted with 5S rRNA and that the region around loop B of 5S rRNA was involved in this interaction. These results suggest the presence of a novel RNA-RNA interaction between 23S rRNA and 5S rRNA which may play an important role in the ribosome function.

Base Pairing↗
PubMed2001

p35 and p39 are essential for cyclin-dependent kinase 5 function during neurodevelopment.

Cyclin-dependent kinase 5 (Cdk5) plays a pivotal role in brain development and neuronal migration. Cdk5 is abundant in postmitotic, terminally differentiated neurons. The ability of Cdk5 to phosphorylate substrates is dependent on activation by its neuronal-specific activators p35 and p39. There exist striking differences in the phenotypic severity of Cdk5-deficient mice and p35-deficient mice. Cdk5-null mutants show a more severe disruption of lamination in the cerebral cortex, hippocampus, and cerebellum. In addition, Cdk5-null mice display perinatal lethality, whereas p35-null mice are viable. These discrepancies have been attributed to the function of other Cdk5 activators, such as p39. To understand the roles of p39 and p35, we created p39-null mice and p35/p39 compound-mutant mice. Interestingly, p39-null mice show no obvious detectable abnormalities, whereas p35(-/-)p39(-/-) double-null mutants are perinatal lethal. We show here that the p35(-/-)p39(-/-) mutants exhibit phenotypes identical to those of the Cdk5-null mutant mice. Other compound-mutant mice with intermediate phenotypes allow us to determine the distinct and redundant functions between p35 and p39. Our data strongly suggest that p35 and p39 are essential for Cdk5 activity during the development of the nervous system. Thus, p35 and p39 are likely to be the principal, if not the only, activators of Cdk5.

Animals↗
PubMed2001

Impact of fluorine-18 fluorodeoxyglucose positron emission tomography on patient management: first year's experience in a clinical center.

PURPOSE: To measure the impact of whole-body fluorodeoxyglucose (FDG) positron emission tomography (PET) on patient management during its first year of use in a community hospital. MATERIALS AND METHODS: First-year FDG-PET impact was determined from 463 referring physicians' evaluations of their patients' PET imaging results using two surveys. Survey 1 was given to all physicians referring patients to PET to discover whether PET changed patient management or had decision-making value in the patient's clinical algorithm. Survey 2 was given to one surgeon and one pulmonologist after therapy to determine how PET affected the surgical, chemotherapeutic, and/or radiotherapeutic treatment for the 53 cancer patients they referred. RESULTS: The 463 responses to survey 1 described 23 different PET indications. Lung (40%), head and neck (18%), and colorectal cancers (11%) were the three leading causes of referral. PET changed patient management/therapy in 45% of all patients referred and had inferential/decision-making value in another 44%. Overall, PET had some type of positive influence in 412 (89%) of the patients. Survey 2 provided a more detailed assessment of 53 referrals from two specialists. PET positively affected surgery in 31 patients (58%), prompted the addition of chemotherapy or radiation therapy in nine patients (17%), and eliminated chemotherapy or radiation therapy in four cases (8%). Overall, PET affected patient management/therapy in 70% of the cases and had some decision-making value in another 26%, for a combined PET impact on patient management of 96%. CONCLUSION: FDG-PET can be valuable for physicians in clinical practice. Its sensitivity and specificity in metabolic imaging, when combined with complementary anatomic imaging techniques, contribute significantly to the clinical treatment of cancer patients. In addition, the high accuracy of FDG-PET makes it a cost-effective radiologic procedure in the work-up of all suspected and/or recurrent cancer patients. Further research is needed to link this demonstrated impact on patient management to cost-effectiveness.

Fluorodeoxyglucose F18↗
PubMed2001

Comparison of selected retention models in reversed-phase liquid chromatography.

Retention models are usually compared by how well the model equation fits retention data for one solute taken over a range of mobile phase compositions. Even when retention data for multiple solutes are used, the quality of the fit is often judged by the statistical goodness-of-fit alone. This study compared four different RPLC retention models, encompassing three distinct mathematical forms. Each model was fit to the retention data of multiple solutes and the sets of best-fit parameters were examined in terms of the underlying physico-chemical assumptions of the models. Next, for the linear and quadratic models, some of the model parameters were calculated a priori and the rest of the model parameters were then obtained in subsequent fittings. The sets of best-fit parameters obtained in this manner were more consistent with the underlying assumptions of these models than were the sets of parameters obtained entirely through regressions to the experimental data. Thus, the extraction of parameters by fitting a model to the retention data of a single solute may result in unreliable values for those parameters, even in the case of a fit that would be considered good when judged by conventional statistical criteria. That is, although parameters extracted in such a fashion may be suitable for optimization or similar uses, they may not be suitable for determining the appropriateness of the underlying assumptions of retention models.

Chromatography, Liquid↗
PubMed2001

Modeling the effect of solvation on solute retention in reversed-phase liquid chromatography.

The retention of a homologous series of alkylbenzenes was determined on octyl and octadecyl reversed-phase columns in several polar organic liquids. Free energies of transfer were calculated by the SM5.0R classical solvation model for each organic liquid tested and for several alkanes. The relationships between the measured retention factors and the calculated free energies of transfer were then investigated. Although the natural logarithms of the retention factor and the calculated free energies of transfer were linearly correlated, the obtained free energies of transfer of the solutes did not completely explain the retention behavior of the solutes. Nonetheless, even in these pure organic liquids, the energetics of RPLC retention behaved very similarly to those of partitioning.

Chromatography, High Pressure Liquid↗
PubMed2001

Effect of divalent cations on the ATPase activity of Escherichia coli SecA.

It was found that Ca(2+) stimulates the intrinsic SecA ATPase activity in the absence as well as in the presence of liposome. On the other hand, Mg(2+), the general cofactor for ATPase, did not affect the intrinsic SecA ATPase but reduced the portion of ATPase activity enhanced by Ca(2+). The enhancement of SecA ATPase activity correlated well with the increase in 8-anilino-1-naphthalene-sulfonic acid binding of SecA, suggesting that increased exposure of hydrophobic residues stimulates the enzyme activity.

Adenosine Triphosphatases↗
PubMed2001

Inhibition of cytosolic phospholipase A2 by annexin I. Specific interaction model and mapping of the interaction site.

Annexins (ANXs) display regulatory functions in diverse cellular processes, including inflammation, immune suppression, and membrane fusion. However, the exact biological functions of ANXs still remain obscure. Inhibition of phospholipase A(2) (PLA(2)) by ANX-I, a 346-amino acid protein, has been observed in studies with various forms of PLA(2). "Substrate depletion" and "specific interaction" have been proposed for the mechanism of PLA(2) inhibition by ANX-I. Previously, we proposed a specific interaction model for inhibition of a 100-kDa porcine spleen cytosolic form of PLA(2) (cPLA(2)) by ANX-I (Kim, K. M., Kim, D. K., Park, Y. M., and Na, D. S. (1994) FEBS Lett. 343, 251-255). Herein, we present an analysis of the inhibition mechanism of cPLA(2) by ANX-I in detail using ANX-I and its deletion mutants. Deletion mutants were produced in Escherichia coli, and inhibition of cPLA(2) activity was determined. The deletion mutant ANX-I-(1-274), containing the N terminus to amino acid 274, exhibited no cPLA(2) inhibitory activity, whereas the deletion mutant ANX-I-(275-346), containing amino acid 275 to the C terminus, retained full activity. The protein-protein interaction between cPLA(2) and ANX-I was examined using the deletion mutants by immunoprecipitation and mammalian two-hybrid methods. Full-length ANX-I and ANX-I-(275-346) interacted with the calcium-dependent lipid-binding domain of cPLA(2). ANX-I-(1-274) did not interact with cPLA(2). Immunoprecipitation of A549 cell lysate with anti-ANX-I antibody resulted in coprecipitation of cPLA(2). These results are consistent with the specific interaction mechanism rather than the substrate depletion model. ANX-I may function as a negative regulator of cPLA(2) in cellular signal transduction.

Animals↗
PubMed2001

Differential effects of annexins I, II, III, and V on cytosolic phospholipase A2 activity: specific interaction model.

Annexins (ANXs) are a family of proteins with calcium-dependent phospholipid binding properties. Although inhibition of phospholipase A2 (PLA2) by ANX-I has been reported, the mechanism is still controversial. Previously we proposed a 'specific interaction' model for the mechanism of cytosolic PLA2 (cPLA2) inhibition by ANX-I [Kim et al., FEBS Lett. 343 (1994) 251-255]. Here we have studied the cPLA2 inhibition mechanism using ANX-I, N-terminally deleted ANX-I (DeltaANX-I), ANX-II, ANX-II(2)P11(2), ANX-III, and ANX-V. Under the conditions for the specific interaction model, ANX-I, DeltaANX-I, and ANX-II(2)P11(2) inhibited cPLA2, whereas inhibition by ANX-II and ANX-III was negligible. Inhibition by ANX-V was much smaller than that by ANX-I. The protein-protein interactions between cPLA2 and ANX-I, DeltaANX-I, and ANX-II(2)P11(2) were verified by immunoprecipitation. We can therefore conclude that inhibition of cPLA2 by specific interaction is not a general function of all ANXs, and is rather a specific function of ANX-I. The results are consistent with the specific interaction model.

Animals↗
PubMed2001

Expression of the human insulin gene in the gastric G cells of transgenic mice.

The goal of this study was to engineer gastrin-producing G cells of the gastric antrum to produce insulin. A pGas-Ins chimeric gene in which the gastrin promoter drives expression of the human insulin gene was constructed and was validated by transient transfection of GH4 and AGS cells. RT-PCR analysis and sequencing revealed three forms of differentially spliced insulin mRNA in GH4 cells transiently transfected by pGas-Ins. Gas-Ins transgenic mice were generated utilizing this chimeric gene. Northern blot analysis, in situ hybridization, and immunohistochemistry demonstrated expression of the human insulin gene specifically in antral G cells. Northern blot analysis demonstrated that the shortest of the insulin mRNA three forms is predominantly expressed in stomach tissue. RT-PCR analysis also showed expression of the transgene in colon, pancreas, and brain tissues that was undetectable by northern analysis. We conclude that gastrin promoter can be used for targeting expression of human insulin to antral G cells and that antral G cells can express human insulin. Further refining of the chimeric gene design is required to enhance expression.

Animals↗