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Biomedical subjects

C Y Park

Publications and source records attributed to C Y Park.

At least 19 recordsLinked to original sources
PubMed2006

Sweep optical frequency synthesizer with a distributed-Bragg-reflector laser injection locked by a single component of an optical frequency comb.

A sweep optical frequency synthesizer is demonstrated by using a frequency-stabilized optical frequency comb and injection-locked distributed-Bragg-reflector (DBR) laser diode. The injection-locked DBR laser acts as a single-frequency filter and, simultaneously, a high-gain amplifier of the optical frequency comb. The frequency instability of the heterodyne beat signal between two independently injection-locked DBR lasers is measured to be 2.3 x 10(-16) at 1 s averaging time. The output frequency of the sweep optical frequency synthesizer can be precisely tuned over 1 GHz, and a saturated absorption spectrum of the Cs D2 line at 852 nm is recorded by the injected DBR laser.

Journal Article↗
PubMed2006

A numerical study on the effect of side hole number and arrangement in venous cannulae.

Insertion of cannulae into vessels may apply non-physiological load and stress on blood cells, such that adenosine diphosphate may increase and result in hemolysis. Authors used the computational method to simulate the blood flow inside of the cannula. We limited the research to within the drainage cannulae. Nine different cannulae categorized by the number of side holes of 4, 12, and 20, and also categorized by the array type as staggered array, in-line array, and alternative in-line array were studied and compared to the cannulae with no side holes by using computational fluid dynamics. We evaluated the flow rate, the wall shear stress, and the shear rate, and compared them with one another to estimate the effect of the side holes. The flow rate is not proportional to the number of the side holes. However, larger number of side holes can reduce the mean shear rate.

Biomechanical Phenomena↗
PubMed2003

Successful allogeneic hematopoietic stem cell transplantation using triple agent immunosuppression in severe aplastic anemia patients.

Graft rejection in patients with severe aplastic anemia (SAA) following allogeneic hematopoietic stem cell transplantation (HSCT) is strongly associated with a large number of prior transfusions and with prolonged disease duration before transplant. We retrospectively analyzed the outcomes and the factor affecting these multitransfused SAA patients, who had received triple agent immunosuppression and high doses of stem cells to overcome rejection. In total, 113 patients with SAA who had a median 16 months (range 1-216) of disease duration were transplanted using HLA-matched sibling donors after conditioning with cyclophosphamide (CY), procarbazine (PCB), and ATG. Graft failure occurred in 16 of the eligible 113 patients, and with a median follow-up of 30 months (range, 1-80), probability of overall rejection was 15%. Specifically, the multitransfused patients who received high doses of stem cells with T-cell depletion showed the lowest rejection rate, 5.6%, compared with 30.3% in multitransfused patients with bone marrow stem cells alone (P=0.0310). Disease duration (P=0.0338) and the number of infused CD34+cells (P=0.0101) were associated with a high risk of graft rejection on multivariate analysis. ABO mismatch and the number of CD34+ cells were significant factors in the incidence of acute graft-versus-host-disease (GVHD). The incidence of chronic GVHD among patients with sustained engraftment was 13/109 (11.9%). With the same follow-up period, probability of disease-free survival for the entire group of patients at 6 years was 89% and the only factor associated with long-term survival was rejection (P=0.0241). These results suggest that allogeneic HSCT conditioned with triple agent immunosuppression, and specifically with high-dose stem cell return is probably an effective treatment for successful engraftment in SAA patients with a high risk of rejection.

ABO Blood-Group System↗
PubMed2003

AnyHeart: a single-piece heart-saving implantable artificial heart (BVAD)--monitoring and estimation.

AnyHeart is a single-piece, implantable biventricular assist device. This electromechanical BVAD has a moving-actuator mechanism. To monitor the status of AnyHeart from anywhere at any time, a portable personal digital assistant (PDA) monitor and web-based remote monitoring system were developed. The PDA local monitoring system has replaced bulky personal computer monitoring systems. The web-based remote monitoring system has several functions such as data collecting, storing, and posting through the internet. Basically, interventricular pressure (IVP) is a parameter indicating the filling level of the blood chambers of AnyHeart. The pump output can be estimated using IVP, which is acquired noninvasively from AnyHeart. With the proposed method, we can estimate the pump output with a small margin of error.

Computers, Handheld↗
PubMed2003

Estimation of coupled assist flows in a moving-actuator bi-ventricular assist device using interventricular pressure.

An assist flow estimation scheme for a moving-actuator biventricular assist device (MA-BVAD) using interventricular pressure (IVP) has been developed. The scheme uses a waveform feature parameter of IVP, peak IVP time (PIT), for estimation of the filling volumes of both left and right blood sacs simultaneously. In a regression analysis on data from an in vivo test in an 85 Kg male calf for 20 days, the PIT was found to have high correlation with the blood sac filling volume (R=0.883: left filling volume, R=0.967: right filling volume). A conceptual equation hypothesizing this correlation between PIT and filling volume was established based on the observation and the unknown parameters were identified using least squares parameter optimization. The estimation equation identified proved highly accurate (R=0.916 for left flow, R=0.970 for right flow). The accuracy of the estimation scheme promises very good practical applicability.

Animals↗
PubMed2002

Application of the moving-actuator type pump as a ventricular assist device: in vitro and in vivo studies.

A moving actuator type pump has been developed as a multifunctional Korean artificial heart (AnyHeart). The pump consists of a moving actuator as an energy converter, right and left sacs, polymer (or mechanical) valves, and a rigid polyurethane housing. The actuator containing a brushless DC motor moves back and forth on an epicyclical gear train to produce a pendular motion, which compresses both sacs alternately. Of its versatile functions of ventricular assist device and total artificial heart use, we have evaluated the system performance as a single or biventricular assist device through in vitro and in vivo experiments. Pump performance and anatomical feasibility were tested using various animals of different sizes. In the case of single ventricular assist device (VAD) use, one of the sacs remained empty and a mini-compliance chamber was attached to either an outflow or inflow port of the unused sac. The in vitro and in vivo studies show acceptable performance and pump behavior. Further extensive study is required to proceed to human application.

Animals↗
PubMed2001

Preferential loss of 5q14-21 in intestinal-type gastric cancer with DNA aneuploidy.

BACKGROUND: Little is known about the genetic changes associated with DNA ploidy in gastric cancer (GC). The aim of this study was to identify recurrent or specific chromosomal regions of DNA sequence copy number aberrations (DSCNAs) that might harbor genes associated with DNA aneuploidy in GC. METHODS: We analyzed DSCNAs with comparative genomic hybridization and DNA ploidy by laser scanning cytometry in 16 primary intestinal-type GCs. RESULTS: All GCs examined showed at least one DSCNA (loss or gain); eight were DNA diploid (DD) tumors and eight were DNA aneuploid (DA) tumors. The frequent (>30%) DSCNAs were loss of 5q14-21 and gains of 7p11-14, 8q, 20q, and Xq25-26. Recurrent amplifications (>10%) were detected at chromosomal regions 6p, 7p, and 13q. The overall number of DSCNAs was significantly greater in DA than in DD tumors (P = 0.006). Furthermore, the number of aberrations was clearly greater with 5q loss than without 5q loss (P = 0.002). Losses of 5q14-21, 9p21-pter, 16q, and 18q21-qter were preferentially detected in DA tumors. CONCLUSION: The present observations indicate that there is a close relationship between DSCNA and DNA ploidy in intestinal-type GC and that gene(s) at 5q14-21, 9p21-pter, 16q, and/or 18q21-qter may play important roles in acquisition of DNA aneuploidy.

Adult↗
PubMed2001

Clonorchis sinensis: molecular cloning and characterization of 28-kDa glutathione S-transferase.

A 28-kDa glutathione S-transferase (Cs28GST) was purified from a Clonorchis sinensis cytosolic fraction through anion-exchange and glutathione-affinity column chromatographies. A monoclonal antibody raised against Cs28GST reacted specifically to the C. sinensis antigen among trematode proteins. A putative peptide of 212 amino residues deduced from a cDNA clone appeared homologous with 28-kDa GST of trematodes, and its secondary structural elements predicted a GSH-binding site. Recombinant Cs28GST showed GST enzyme activity with CDNB substrate and was sensitive to the model inhibitors. The recombinant Cs28GST was antigenically indistinguishable from the native form and was recognized specifically by C. sinensis-infected human sera. The Cs28GST was localized in the tegument and underlying mesenchymal tissues. It is suggested that Cs28GST may play significant physiological roles against bioreactive molecules and be a useful reagent for serodiagnosis of clonorchiasis.

Amino Acid Sequence↗
PubMed2001

Broadcasting health programmes among audience and professionals in Korea: perceptions and needs.

Mass media has become an essential part of modern society, and it should be noted that mass media plays an important role in delivering information even in the area of health. This study was intended to investigate the perceptions of and needs for broadcasting health programmes among audience and related professionals in Korea, which will serve to help in the development of valuable health programmes. Data were collected through a series of self-administered questionnaire surveys conducted on two types of subjects sampled from residents in the areas around Seoul, Korea, and health or broadcasting professionals working on health programmes. There were some discrepancies in the perceptions of and needs for health programmes between audience and professionals, especially the main audience age group and image, needs for topics and mode of health programme. In conclusion, in order to enhance current health programmes which focus on aspects of diagnosis and treatment of diseases, the range of health programmes should be expanded to fulfill various needs.

Adult↗
PubMed2001

Assessing public understanding of the policy of separating dispensing and prescribing in Korea: a survey of college students.

We investigated the level of public understanding of the 'separation of dispensing and prescribing' health policy in Korea and its associated factors. A questionnaire survey was conducted upon 700 college students at four months after the introduction of the policy. The understanding level was measured using four question items describing the goal and motivation of the policy, and ten items describing its operational rules. For each item, respondents were asked to mark whether the description was true or false. While the goal and motivation of the policy was relatively well informed (mean understanding score: 69.58 out of 100), people did not have a good understanding of the operational details of the policy (mean score: 32.52). The results of regression analyses showed that personal interest and agreement with the need of the policy were the most significant factors affecting the understanding level (p < 0.01). It is concluded that, for other public policies in the future, policy makers in Korea need to develop more effective media communication strategies to effectively inform the public of the practical details of the policy.

Adult↗
PubMed2000

Activation of telomerase by silica in rat lung.

By measuring the activity of telomerase in a silica-instilled rat lung, the study found a significant increase in telomerase activity compared to that of the control. Pneumoconiosis displays the characteristics of fibroblast-proliferation and accumulation of collagen, which finally causes the pathologic changes of irreversible and progressive fibrosis of the lung. On the basis of the hypothesis that cellular proliferation may trigger telomerase-activity, the experiment was carried out with telomerase-activation in silicosis. Silica-instilled rat lungs showed increased activity of telomerase, which was measured by TRAP (telomeric repeat amplification protocol) assay, at the time of the 1st, 5th and 8th week after intratracheal instillation of silica in vivo. However, no activity was shown in silica-co-cultured fibroblast in vitro. By summarizing these results, the activity of telomerase is thought to be a very sensitive marker for the evaluation of pathogenicity, showing cellular immortalization in an experimental silicosis model.

Animals↗
PubMed2000

Identification of a calmodulin-regulated soybean Ca(2+)-ATPase (SCA1) that is located in the plasma membrane.

Ca(2)+-ATPases are key regulators of Ca(2+) ion efflux in all eukaryotes. Animal cells have two distinct families of Ca(2+) pumps, with calmodulin-stimulated pumps (type IIB pumps) found exclusively at the plasma membrane. In plants, no equivalent type IIB pump located at the plasma membrane has been identified at the molecular level, although related isoforms have been identified in non-plasma membrane locations. Here, we identify a plant cDNA, designated SCA1 (for soybean Ca(2+)-ATPase 1), that encodes Ca(2+)-ATPase and is located at the plasma membrane. The plasma membrane localization was determined by sucrose gradient and aqueous two-phase membrane fractionations and was confirmed by the localization of SCA1p tagged with a green fluorescent protein. The Ca(2+)-ATPase activity of the SCA1p was increased approximately sixfold by calmodulin (K(1/2) approximately 10 nM). Two calmodulin binding sequences were identified in the N-terminal domain. An N-terminal truncation mutant that deletes sequence through the two calmodulin binding sites was able to complement a yeast mutant (K616) that was deficient in two endogenous Ca(2+) pumps. Our results indicate that SCA1p is structurally distinct from the plasma membrane-localized Ca(2+) pump in animal cells, belonging instead to a novel family of plant type IIB pumps found in multiple subcellular locations. In plant cells from soybean, expression of this plasma membrane pump was highly and rapidly induced by salt (NaCl) stress and a fungal elicitor but not by osmotic stress.

Amino Acid Motifs↗
PubMed2000

Recent advances in particulate-induced pulmonary fibrosis; for the application of possible strategy experimentally and clinically.

Chronic interstitial lung diseases including pneumoconiosis have pathological characteristics which alter the lung structure and function consequent to the accumulation and activation of inflammatory cells in the lower respiratory tract. These activated cells usually secrete the inflammatory and fibrogenic mediators. Of the diffuse parenchymal lung diseases, the majority have no known etiology and idiopathic pulmonary fibrosis (IPF) is the diagnosis most frequently encountered by clinicians. Pathogenic similarities between pneumoconiosis and IPF provide a strong basis for hypothesizing that environmental agents may cause IPF. Many case-control studies have been published that provide further evidence for a number of associations between occupational and environmental exposures and IPF. Such reports support a strong evidence that IPF may be a heterogenous disorder associated with a number of environmental exposures. As a model of lung fibrosis, experimental pneumoconiosis is giving us a great information because crystalline silica is probably one of the most typical agent producing pulmonary fibrosis and the severity of its health effects and the widespread nature of exposure have been long recognized. Many papers provide evidence that particles have the potential to cause stimulation of phagocytes to release oxidants and such oxidative stress is believed to be a major factor in pulmonary inflammation followed by fibrotic change. Many kinds of cellular mediators are recognized as a implicating factor in this process including cell-to-cell interaction, enzymes, cytokines, arachidonic acid derivatives et al. Treatment of pneumoconiosis is an attractive and interesting topic. But, the mechanism of pathogenesis of pneumoconiosis is not thoroughly understood yet. Also, whether the process of fibrosis formation be retarded or not is questionable with some therapeutic trial. Therefore, a sensitive biomarker which is possible to estimate the pathological pathway in pneumoconiosis is needed. Our laboratory has studied particulate-induced pulmonary reaction for two decades consistently. This review will focus on signal transduction pathway involved in oxidative stress and some inhibitory agents with pleiotropic mechanism in pulmonary fibrosis. I will also introduce some data of animal studies with multidrug regimen as well.

Adrenal Cortex Hormones↗
PubMed2000

Retroviral-mediated IL-2 gene transfer into murine neuroblastoma.

We used retroviral-mediated gene transfer of the human interleukin (IL)-2 gene into murine neuroblastoma cells to investigate whether locally-secreted IL-2 is able to influence the generation of anti-tumor immune responses. Supernatant obtained from cultures of approximately 1 x 10(6) IL-2 gene-transduced, G-418 selected neuro-2a cells was assayed for human IL-2 production by ELISA kit. First, to estimate whether the local secretion of IL-2 from the genetically-modified tumor cells would affect their tumorigenicity in vivo, IL-2-secreting neuro-2a cells were s.c. injected into A/J mice and tumor growth was measured weekly. And to estimate whether IL-2 transfected neuroblastoma cells protect mice from tumor development after wild-type tumor cell challenge, IL-2-secreting neuro-2a cells were s.c. injected into A/J mice. Seven days after IL-2 gene-transfected neuroblastoma cell injection, unmodified neuro-2a cells were s.c. injected into the contralateral site of A/J mice and tumor growth was measured weekly. Finally, to estimate IL-2 effect on pre-established large tumor burdens, IL-2-secreting neuro-2a cells were s.c. injected into A/J mice with established tumor and its growth was measured weekly. The IL-2 gene-transduced neuro-2a clones secreted 120.25-177.3 IU of IL-2 per ml per 10(6) cells during 24 hr. None of the mice injected with IL-2-secreting neuro-2a cells developed tumors within 6 weeks, while all of the mice injected with wild-type neuro-2a cells developed tumors. Immunization of mice with IL-2 gene-transfected, irradiated neuro-2a cells protected these animals against a subsequent challenge with wild-type tumor cells. Finally, the size of large neuroblastomas decreased after IL-2-secreting neuro-2a cell injection into mice. Local secretion of IL-2 gene-transduced tumor cells abrogates their tumorigenicity and induces protective immunity and may inhibit the growth of neuroblastoma.

Animals↗
PubMed1999

Competitive binding of calmodulin isoforms to calmodulin-binding proteins: implication for the function of calmodulin isoforms in plants.

In plants, multiple calmodulin (CaM) isoforms exist in an organism which vary in their primary structures in as much as 32 residues out of their 148 amino acids. These CaM isoforms show differences in their expression patterns and/or target enzyme activation ability. To further understand the biological significance of CaM isoforms, we examined whether CaM isoforms act on specific regulatory targets. In gel overlay assays on various soybean tissue extracts, surprisingly, two soybean CaM isoforms (SCaM-1 and SCaM-4) did not show significant differences in their target binding protein profiles, although they exhibited minor differences in their relative target binding affinities. In addition, both SCaM isoforms not only effectively bound five known plant CaMBPs, but also showed competitive binding to these proteins. Finally, immunolocalization experiments with the SCaM proteins in sections of various tissues using specific antibodies revealed similar distribution patterns for the SCaM isoforms except for root tissues, which indicates that the SCaM isoforms are concomitantly expressed in most plant tissues. These results suggest that CaM isoforms may compete for binding to CaMBPs in vivo. This competitive nature of CaM isoforms may allow modulation of Ca(2+)/CaM signaling pathways by virtue of relative abundance and differential target activation potency.

Binding, Competitive↗
PubMed1999

The tyrosines in the bidentate motif of the env-sea oncoprotein are essential for cell transformation and are binding sites for Grb2 and the tyrosine phosphatase SHP-2.

The transforming gene product of the S13 avian erythroblastosis virus, the env-sea protein, is a member of the hepatocyte growth factor receptor family of tyrosine kinases comprising Met, Ron, and Sea. Like all three members of this family, the env-sea protein has a so-called bidentate motif (Y557INMAVTY564VNL) composed of two tandemly arranged tyrosines in the carboxyl terminus. To investigate whether the tyrosine residues in this motif are essential for the env-sea-mediated transformation, we generated tyrosine to phenylalanine mutations. Substitutions of both tyrosine residues resulted in complete loss of the transforming activity. In contrast, single mutations at either tyrosine did not inhibit transformation of Rat1 cells, and mutation of tyrosine 564 actually increased transformation of Rat 1 cells. To define signaling pathways activated by the env-sea protein, we looked for protein-protein interactions mediated by these tyrosine residues. We show that the bidentate motif is responsible for interaction with the adapter protein Grb2, phosphatidylinositol 3-kinase, and the tyrosine phosphatase SHP-2. Furthermore, we show that microinjected Src homology 2 domains from either Grb2 or SHP-2 blocked the transforming activity of the env-sea protein. Together, these results suggest that the tyrosines within the bidentate motif are essential for the env-sea transformation.

Adaptor Proteins, Signal Transducing↗