Biomedical subjects

H Choi

Publications and source records attributed to H Choi.

At least 19 recordsLinked to original sources

PubMed2006

Collective modes and f-wave pairing interactions in superfluid (3)He.

Precision measurements of collective mode frequencies in superfluid (3)He-B are sensitive to quasiparticle and f-wave pairing interactions. Measurements were performed at various pressures using interference of transverse sound in an acoustic cavity. We fit the measured collective mode frequencies, which depend on the strength of f-wave pairing and the Fermi liquid parameter F(2)(s), to theoretical predictions and discuss what implications these values have for observing new order parameter collective modes.

Journal Article↗

PubMed2006

Novel ADAMTS-13 mutations in an adult with delayed onset thrombotic thrombocytopenic purpura.

BACKGROUND: Thrombotic thrombocytopenic purpura (TTP) is associated with congenital and acquired deficiency of ADAMTS-13, a metalloprotease that cleaves von Willebrand factor (VWF) and reduces its adhesive activity. Mutations throughout the ADAMTS13 gene have been identified in congenital TTP patients, most of whom have initial episodes during infancy or in early childhood. PATIENTS AND METHODS: We report the case of an adult male who was diagnosed with idiopathic thrombocytopenic purpura at age 34, and with TTP 14 years later. The patient was compound heterozygous for an 18 bp in-frame deletion (C365del) in the disintegrin domain and a point mutation of R1060W in the seventh thrombospondin domain of the ADAMTS-13 gene. CONCLUSIONS: In vitro studies found that C365del and R1060W severely impair ADAMTS-13 synthesis in transfected Hela cells, whereas the deletion mutant also failed to cleave VWF under static and flow conditions.

ADAM Proteins↗

PubMed2006

Classification of partial seizure symptoms in genetic studies of the epilepsies.

OBJECTIVES: To develop standardized definitions for classification of partial seizure symptoms for use in genetic research on the epilepsies, and evaluate inter-rater reliability of classifications based on these definitions. METHODS: The authors developed the Partial Seizure Symptom Definitions (PSSD), which include standardized definitions of 41 partial seizure symptoms within the sensory, autonomic, aphasic, psychic, and motor categories. Based on these definitions, two epileptologists independently classified partial seizures in 75 individuals from 34 families selected because one person had ictal auditory symptoms or aphasia. The data used for classification consisted of standardized diagnostic interviews with subjects and family informants, and medical records obtained from treating neurologists. Agreement was assessed by kappa. RESULTS: Agreement between the two neurologists using the PSSD was "substantial" or "almost perfect" for most symptom categories. CONCLUSIONS: Use of standardized definitions for classification of partial seizure symptoms such as those in the Partial Seizure Symptom Definitions should improve reliability and accuracy in future genetic studies of the epilepsies.

Epilepsies, Partial↗

PubMed2006

An orally active cathepsin K inhibitor, furan-2-carboxylic acid, 1-{1-[4-fluoro-2-(2-oxo-pyrrolidin-1-yl)-phenyl]-3-oxo-piperidin-4-ylcarbamoyl}-cyclohexyl)-amide (OST-4077), inhibits osteoclast activity in vitro and bone loss in ovariectomized rats.

Human cathepsin K, a cysteine proteinase of the papain family, has been recognized as a potential drug target for the treatment of osteoporosis. The predominant expression of cathepsin K in osteoclasts has rendered the enzyme into a major target for the development of novel antiresorptive drugs. Now, we report the pharmacological properties of OST-4077 [furan-2-carboxylic acid (1-{1-[4-fluoro-2-(2-oxo-pyrrolidin-1-yl)-phenyl]-3-oxo-piperidin-4-ylcarbamoyl}-cyclohexyl)-amide] as a novel selective cathepsin K inhibitor. Human and rat cathepsin K were inhibited in vitro by OST-4077 with the IC50 values of 11 and 427 nM, respectively. OST-4077 suppressed bone resorption induced by rabbit osteoclasts (IC50, 37 nM) but did not affect bone mineralization or cellular alkaline phosphatase activity in MC3T3-E1 cells. Parathyroid hormone-induced bone resorption was inhibited in a dose-dependent manner in thyroparathyroidectomized rats gavaged with a single dose of OST-4077 (ED50, 69 mg/kg). When given orally twice daily for 4 weeks to 3-month-old ovariectomized (OVX) rats, OST-4077 dose-dependently prevented bone loss, as monitored by bone densitometry, ash content, and urinary excretion of deoxypyridinoline. No change in serum osteocalcin in the OVX rats by OST-4077 suggested that bone formation might not be affected by the agent. In summary, OST-4077 selectively inhibited bone resorbing activities of osteoclasts and prevented bone loss induced by estrogen deficiency but did not affect bone formation. OST-4077, an orally active selective human cathepsin K inhibitor, may have the therapeutic potential for the treatment of diseases characterized by excessive bone loss including osteoporosis.

Alkaline Phosphatase↗

PubMed2006

Surface specific heat of 3He and Andreev bound states.

High resolution measurements of the specific heat of liquid 3He in the presence of a silver surface have been performed at temperatures near the superfluid transition in the pressure range of 1-29 bar. The surface contribution to the heat capacity is identified with Andreev bound states of quasiparticles that have a range of half a coherence length.

Journal Article↗

PubMed2006

Risk assessment of human exposure to cypermethrin during treatment of mandarin fields.

The potential dermal and respiratory exposure assessment and risk assessment for applicator were performed with cypermethrin EC. The pesticide was applied on a mandarin field using a power sprayer. Gloves were used for the hand exposure assessment, mask for face, and dermal patches for the other parts of the body. Personal air monitor equipped with a XAD-2 resin was used for the respiratory exposure assessment. During the application of cypermethrin in the field, the rate of potential dermal exposure ranged from 28.1 to 58.8 mg/h. The major exposure parts were upper-arms (22.1-24.6%) and legs (thigh and shin, 28.3-29.2%) for females and thigh (21.0-46.9%) and hand (14.9-19.3%) for males. Females were exposed more than males. No exposure was detected from the respiratory monitoring. For risk assessment, the potential dermal exposure (PDE), the absorbable quantity of exposure (AQE), and the margin of safety (MOS) were calculated. Among those four risk assessments, MOS was < 1 in only trial I, which indicated any possibility of risk. However, in the others, the possibility of risk was little. Moreover, the safe work time ranged from 3.61 h to 9.69 h.

Air Pollutants, Occupational↗

PubMed2006

Physical phantom of typical Korean male for radiation protection purpose.

Dose distribution within a human body can be measured using physical anthropomorphic phantoms. In an effort to establish reference Korean physical model, the first Korean physical phantom of average Korean adult male was constructed using computed tomography (CT) images of a healthy volunteer. The body dimension of the subject was close to that of average Korean male. The source images were obtained using fusion positron emission tomography machine at Radiation Health Research Institute in Korea, and ported into rapid prototyping process. The physical phantom was composed of three tissue-equivalent materials: epoxy resin, urethane foam and polyurethane representing bone, lungs and soft tissues, respectively. The densities of the tissue-equivalent materials were close to those recommended by the International Commission on Radiation Units and measurements. To facilitate dose mapping, the phantom was sliced into 2 cm sections. Hole grids for thermoluminescence (TL) dosemeter chips were drilled. To verify the appropriateness of the physical phantom, organ doses of selected organs were measured for reference photon beam, and compared with those computed by tomographic model constructed from the same CT images. Absorbed doses converted from TL relative response showed good agreement within 7% with those calculated.

Body Burden↗

PubMed2006

Diagnostic yield of advanced colorectal neoplasia at colonoscopy, according to indications: an investigation from the Korean Association for the Study of Intestinal Diseases (KASID).

BACKGROUND AND STUDY AIMS: The factors that more accurately predict the detection of colorectal cancers and adenomas at colonoscopy are different. We conducted a prospective multicenter study to evaluate which indications were most closely associated with advanced colorectal neoplasm (CRN), including colorectal cancer, in a group of patients undergoing colonoscopy. PATIENTS AND METHODS: The 17 468 patients were enrolled in this study between July 2003 and March 2004, from 11 tertiary medical centers in Korea. They were recruited according to 11 itemized colonoscopic indications. The term "advanced adenoma" refers here to tubular adenomas of diameter of 11 mm or more, or to tubulovillous, villous, or severely dysplastic adenomas, irrespective of their size. Cancer was defined as the invasion of malignant cells beyond the muscularis mucosa. Advanced CRN was defined as advanced adenoma or invasive cancer. RESULTS: Advanced CRN was found in 1227/17 307 patients (1176 advanced adenomas plus 51 carcinomas, 7.1 %). According to univariate and multivariate analysis, the factors associated with advanced CRN included age >60 years (odds ratio (OR) 2.1, 95 % confidence interval (CI) 1.8 - 2.4, P < 0.0001), male gender (OR 2.1, 95 %CI 1.7 - 2.7, P < 0.0001), referral for colonoscopy from primary care physician (OR 3.1, 95 %CI 2.5 - 3.7, P < 0.0001), and several other indications (OR 1.8, 95 %CI 1.5 - 2.3, P < 0.001). The yield of colonoscopy for advanced CRN was lower (2.2 %) than expected in patients with iron-deficiency anemia (OR 0.5, 95 %CI 0.2 - 0.9, P = 0.03). CONCLUSIONS: Age, gender, and referral for colonoscopy from primary care physician constituted important independent predictors of advanced CRN in patients undergoing colonoscopy.

Adenoma↗

PubMed2006

Effects of 25-hydroxyvitamin D3 and manipulated dietary cation-anion difference on the tenderness of beef from cull native Korean cows.

In this study, we characterized the effects of 25-hydroxyvitamin D3 (25-OH D3) and manipulated dietary cation-anion difference (DCAD) on the performance, urine pH, serum constituents, carcass traits, tissue residual vitamin D and its metabolites, beef tenderness, and mRNA and protein concentrations of Ca-dependent proteinases in LM using 24 cull native Korean cows. The cows were divided into 3 groups of 8: control, 25-OH D3 supplemented (25-OH D3), and manipulated DCAD plus 25-OH D3 supplemented (DCAD+25-OH D3). Cows receiving 25-OH D3 or DCAD+25-OH D3 were dosed with 125 mg of 25-OH D3 6 d before slaughter. The manipulated DCAD (-10 mEq/100 g of DM) diet was fed from 20 to 6 d (14 d) before slaughter. The DCAD+25-OH D3 treatment decreased urine pH and increased serum Ca concentrations. Although the vitamin D concentrations in LM, liver, and kidney were not affected by 25-OH D3 or DCAD+25-OH D3, muscle tissue 25-OH D3 concentrations were increased by both regimens. Serum 25-OH D3 concentrations were increased by 25-OH D3 supplementation, and the increase was even greater for DCAD+25-OH D3. The same pattern was observed for serum 1,25- (OH)2 D3. However, the LM concentration of 1,25-(OH)2 D3 was less for DCAD+25-OH D3 than for control. Although Ca concentrations of LM increased numerically in response to 25-OH D3 supplementation, no statistical differences in Warner-Bratzler shear force or sensory traits of LM were detected. The LM of cows receiving 25-OH D3 with or without manipulated DCAD had greater concentrations of mu-calpain and m-calpain mRNA, whereas the reverse was observed for calpastatin mRNA. Expression of mu-calpain protein was increased relative to control by DCAD+25-OH D3. The amount of 25-OH D3 and manipulated DCAD administered to cull native Korean cows was insufficient to improve tenderness of beef by increasing muscle Ca concentration. However, DCAD+25-OH D3 induced greater expressions of mu-calpain protein as well as mRNA.

Animal Feed↗

PubMed2005

Platelet-derived VWF-cleaving metalloprotease ADAMTS-13.

The adhesion ligand von Willebrand factor (VWF) is synthesized and stored in vascular endothelial cells and megakaryocytes/platelets. As in endothelial cells, platelet VWF also contains ultra-large (UL) multimers that are hyperactive in aggregating platelets. ULVWF in platelet lysates of thrombin-stimulated platelets was only detected in the presence of EDTA, suggesting that ULVWF is cleaved by a divalent cation-dependent protease. A recent study shows that platelets contain the VWF-cleaving metalloprotease ADAMTS-13, but its activity remains unknown. In this study, we show that platelet lysates cleave endothelial cell-derived ULVWF under static and flow conditions. This activity is inhibited by EDTA and by an ADAMTS-13 antibody from the plasma of a patient with acquired TTP. ADAMTS-13 was detected in platelet lysates and on the platelet surface by four antibodies that bind to different domains of the metalloprotease. Expression of ADAMTS-13 on the platelet surface increases significantly upon platelet activation by the thrombin receptor-activating peptide, but not by ADP. These results demonstrate that platelets contain functionally active ADAMTS-13. This intrinsic activity may be physiologically important to prevent the sudden release of hyperactive ULVWF from platelets and serves as the second pool of ADAMTS-13 to encounter the increase in ULVWF release from endothelial cells.

ADAM Proteins↗

PubMed2005

Consensus meeting for the management of gastrointestinal stromal tumors. Report of the GIST Consensus Conference of 20-21 March 2004, under the auspices of ESMO.

BACKGROUND: The management of gastrointestinal stromal tumors (GIST) has evolved very rapidly in the last 4 years. The objectives of this international consensus meeting were to describe the optimal management procedures for patients with GIST in localized and advanced stages, as well as research issues for the future. MATERIALS AND METHODS: A panel of experts from six specialties, including pathology, molecular biology, imaging, surgery, medical oncology and methodologists for clinical practice guidelines from different European and extra European sarcoma societies were invited to a 2-day workshop. Several questions were selected by the organizing committee prior to the conference. Selected panelists reviewed the current levels of evidence for each point, and presented their conclusions during the meeting. These proposals were discussed, and consensus points were identified and categorized according to the Standard Options Recommandations (SOR) of the French Federation of Cancer Centers and National Comprehensive Cancer Network (NCCN). RESULTS: Thirty-two consensus points were identified, most from categories 2A of the NCCN and B2 of the SOR. Among these, the standard histological examination with immunohistochemical analysis using CD117, CD34, PS100, desmin and smooth muscle actin is considered standard. Molecular biology for the identification of KIT and PDGFRA mutation is an optional diagnostic procedure for GIST with negative CD117 staining, and otherwise is considered a research procedure. Complete tumor resection with negative tumor margins is the standard surgical treatment. Adjuvant imatinib after optimal tumor resection as well as neo-adjuvant imatinib remain experimental approaches to be performed within prospective clinical studies. Imatinib should be started at the date of diagnosis of metastatic relapse and given until development of intolerance or progressive disease. The optimal criteria for tumor response to imatinib remain to be delineated, and should include not only tumor size reduction or disease stabilization, but also reduction of tumor density (Hounsfield Units) on computed tomography and metabolic activity (i.e. reduction of FDG uptake on positron emission tomography). In a substantial proportion of patients, stable disease and even increase in tumor size may be associated with pathologic response to imatinib therapy, and available survival data indicate that the survival of these patients is similar to that of patients with conventional tumor response. Metastasis resection is an experimental procedure. CONCLUSIONS: Consensus points in clinical management of GIST as well as questions for future clinical trials were identified during this consensus conference on GIST management.

Benzamides↗

PubMed2005

Platelets adhered to endothelial cell-bound ultra-large von Willebrand factor strings support leukocyte tethering and rolling under high shear stress.

Leukocyte rolling on vascular endothelium is mediated by an interaction between P-selectin expressed on endothelial cells and P-selectin glycoprotein ligand-1 on leukocytes. This interaction reduces the velocity of leukocyte movements to allow subsequent firm adhesion and transmigration. However, the interaction has so far been observed only under low venous shear stress and cannot explain the accumulation of monocytes in atherosclerotic plaques found in arteries, where shear stress is much higher. We have previously shown that newly released ultra-large von Willebrand factor (ULVWF) forms extremely long string-like structures to which platelets tether. Here, we investigated whether platelets adhered to ULVWF strings are activated and form aggregates. We also determined whether activated platelets on ULVWF strings can support leukocyte tethering and rolling under high shear stresses. We found that platelets adhered to ULVWF expressed P-selectin and bound PAC-1, suggesting their rapid activation. We also found that leukocytes tethered to and rolled on these platelet-decorated ULVWF strings, but not directly on endothelial cells, under high shear stresses of 20 and 40 dyn/cm(2) in a P-selectin dependent manner. These results suggest that the endothelial cell-bound ULVWF provide an ideal matrix to aggregate platelets and recruit leukocytes to endothelial cells under high shear stress. The observed phenomenon delineates a mechanism for leukocytes to be tethered to arterial endothelial cells under high shear, providing a potential link between inflammation and thrombosis.

Adult↗

PubMed2005

Effects of propylene glycol on carcass traits and its related gene expression in Korean native steers.

The effects of propylene glycol (PEG) on performance, ruminal fermentation, blood glucose and insulin, carcass traits, and abundance of IGF-1 mRNA in LM and leptin mRNA in adipose tissue were examined in 20 Korean native steers, with 10 each in control and PEG-fed groups, respectively. Propylene glycol mixed with concentrate diet was provided daily at a rate of 2.5 mL/kg BW(0.75). Experimental animals were fed a concentrate diet to 1.8% of BW twice daily plus rice straw ad libitum during the 4-mo period before marketing. Daily DMI and ADG did not differ between control and PEG-fed steers. Steers receiving PEG displayed an increase (P = 0.044) in propionate concentration, whereas acetate concentration decreased (P = 0.032). Although blood glucose was not affected, serum insulin was increased (P = 0.047) by PEG feeding. Propylene glycol did not affect carcass weight, 13th-rib fat depth, marbling score, or lipid content of LM. The backfat of PEG-fed steers did not differ in leptin mRNA from control steers, whereas increased leptin mRNA was found in i.m. fat with PEG feeding. There was no treatment effect on the level of IGF-1 mRNA in the LM of the tested steers. These results indicate that the amount of PEG fed to steers was not sufficient to improve marbling score through enhanced ruminal propionate and insulin. The role of increased i.m. leptin mRNA level in PEG-fed steers remains to be further elucidated.

Adipose Tissue↗

PubMed2004

Caregiver's burden, depression and support as predictors of post-stroke depression: a cross-sectional survey.

To examine the effects of caregiver's burden, depression, and support on post-stroke depression (PSD), cross-sectional data were obtained from an epidemiologic survey of 225 stroke survivors and their caregivers living in Seoul, Korea. Multivariate analyses showed that, taking the clinical status of patients into account, caregiver's burden, depression and support were related to higher PSD. Perceived burden exerts adverse effects on PSD through its influence on the depression in caregivers. Hence, the care of stroke survivors that incorporates the care of caregivers is likely to reduce the risk of post-stroke depression in patients.

Activities of Daily Living↗

PubMed2004

Specific heat of disordered superfluid 3He.

The specific heat of superfluid 3He, disordered by a silica aerogel, is found to have a sharp discontinuity marking the thermodynamic transition to superfluidity at a temperature reduced from that of bulk 3He. The magnitude of the discontinuity is also suppressed. This disorder effect can be understood from the Ginzburg-Landau theory which takes into account elastic quasiparticle scattering suppressing both the transition temperature and the amplitude of the order parameter. We infer that the limiting temperature dependence of the specific heat is linear at low temperatures in the disordered superfluid state, consistent with predictions of gapless excitations everywhere on the Fermi surface.

Journal Article↗

PubMed2004

Knowledge of and attitude towards circumcision of adult Korean males by age.

AIM: Circumcision is widely practised in Korea, but little is known regarding the public's attitude towards circumcision. This study was designed to evaluate the knowledge and the general opinion of Korean adult males towards circumcision. METHODS: Fifteen hundred self-completion questionnaires were distributed to adult males in five decadal age groups ranging from 10 to 59 y old. Questions concerning opinions regarding the necessity, reasons, potential benefits and disadvantages of circumcision, as well as the role of peer pressure upon the decision to circumcise were included. Completed questionnaires were collected and analysed statistically. RESULTS: The achieved response rate was 62.7%. 73.1% believed that circumcision is necessary, while 7.1% believed it is not necessary. The principal reason for circumcision was to improve penile hygiene (77.9%). 68.7% did not prefer neonatal circumcision regardless of the respondent's age. The major reason was fear of pain (36.9%). Peer pressure was one of the most influential factors when deciding upon circumcision: 60.8% believed that they might be ridiculed by their peer group unless circumcised, and the younger the age of the respondent, the more frequently this opinion was held (p < 0.05). 62.7% thought that circumcision would prevent genital tract infection of the sexual partner. Respondents with older age tended to emphasize improved sexual potency (p < 0.05). CONCLUSIONS: This study indicates that common beliefs of adult males about circumcision in Korea are relatively homogeneous. Tailored education about circumcision is needed.

Adolescent↗

PubMed2004

Pigment-lightening effect of N,N'-dilinoleylcystamine on human melanoma cells.

BACKGROUND: Cystamine and linoleic acid have been reported to reduce melanin synthesis in vitro and in vivo. N,N'-dilinoleylcystamine (DLC) is a compound of cystamine and linoleic acid connected by an ester bond. OBJECTIVES: To investigate the effects of DLC on melanin synthesis using cultured human melanoma cells. METHODS: Levels of total melanin, eumelanin and phaeomelanin, tyrosinase protein and tyrosinase activity in situ were measured in HM3KO melanoma cells. Changes in degree of pigmentation were quantified by image analysis and compared with absorbance values. Tyrosinase from HM3KO cells was used to measure the direct effect of DLC on DOPA and DOPAchrome production. RESULTS: At concentrations of 1.4-14 micromol L-1, DLC reduced the pigmentation of HM3KO melanoma cells but did not affect cell growth. The visual decrease in pigmentation produced by DLC was more dramatic than the decrease in total melanin content as measured by absorbance at 500 nm. DLC treatment decreased eumelanin synthesis and increased phaeomelanin synthesis in HM3KO melanoma cells. An in situ tyrosinase assay showed that DLC inhibited tyrosinase activity, as well as the level of tyrosinase protein. CONCLUSIONS: These results suggest that DLC has pigment-lightening effects on HM3KO melanoma cells, produced by reducing the level of eumelanin while increasing the level of phaeomelanin.

Blotting, Western↗

PubMed2004

An affinity label for delta-opioid receptors derived from [D-Ala2]deltorphin I.

A series of potential affinity label derivatives of the amphibian opioid peptide [D-Ala2]deltorphin I were prepared by incorporation at the para position of Phe3 (in the 'message' sequence) or Phe5 (in the 'address' sequence) of an electrophilic group (i.e. isothiocyanate or bromoacetamide). The introduction of the electrophile was accomplished by incorporating Fmoc-Phe(p-NHAlloc) into the peptide, followed later in the synthesis by selective deprotection of the Alloc group and modification of the resulting amine. While para substitution decreased the delta-opioid receptor affinity, selected analogs retained nanomolar affinity for delta receptors. [D-Ala2,Phe(p-NCS)3]deltorphin I exhibited moderate affinity (IC50=83 nM) and high selectivity for delta receptors, while the corresponding amine and bromoacetamide derivatives showed pronounced decreases in delta-receptor affinity (80- and >1200-fold, respectively, compared with [D-Ala2]deltorphin I). In the 'address' sequence, the Phe(p-NH2)5 derivative showed the highest delta-receptor affinity (IC50=32 nM), while the Phe(p-NHCOCH2Br)5 and Phe(p-NCS)5 peptides displayed four- and tenfold lower delta-receptor affinities, respectively. [D-Ala2,Phe(p-NCS)3]deltorphin I exhibited wash-resistant inhibition of [3H][D-Pen2,D-Pen5]enkephalin (DPDPE) binding to delta receptors at a concentration of 80 nM. [D-Ala2, Phe(p-NCS)3]deltorphin I represents the first affinity label derivative of one of the potent and selective amphibian opioid peptides, and the first electrophilic affinity label derivative of an agonist containing the reactive functionality in the 'message' sequence of the peptide.

Affinity Labels↗