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Biomedical subjects

D Y Yoon

Publications and source records attributed to D Y Yoon.

34 records · Page 2Linked to original sources
PubMed1998

Antibodies to domains II and III of the IL-1 receptor accessory protein inhibit IL-1 beta activity but not binding: regulation of IL-1 responses is via type I receptor, not the accessory protein.

The IL-1R accessory protein (IL-1RAcP) plays a role in IL-1R signaling by forming a complex with IL-1RI bound to the IL-1 ligand. We identified four hydrophilic peptide regions of the extracellular IL-1RAcP that may be available for complex formation (peptide 1, 71-83 domain I; peptide 2, 204-211 domain II; peptide 3, 282-292 domain III; and peptide 4, 304-314 domain III). These peptides were synthesized, coupled to keyhole limpet hemocyanin, and used to produce rabbit antisera. Each affinity-purified antiserum showed specificity for the respective peptide without cross-reactivity. Anti-peptide 2, 3, and 4 recognized surface expression of IL-1RAcP on the Th2 D10S cells by FACS and inhibited IL-1-driven proliferation. Anti-peptide 4 recognized intact IL-1RAcP and soluble IL-1RAcP. Anti-IL-1RAcP-peptide 4, which targets the terminal segment of domain III, inhibited 80% of IL-1 beta-driven proliferation of D10S cells. However, these IL-1RAcP Abs had no effect on the activity of human or mouse IL-1 alpha. Whereas IL-1 beta down-regulated IL-1RI surface expression (p < 0.05), there was no change in the surface expression of IL-1RAcP. Moreover, murine IL-10 increased surface expression of IL-1RI, but did not affect expression of IL-1RAcP or the proliferation of D10S cells. Steady state levels of mRNA for IL-1RAcP and IL-1RI in D10S cells showed a similar pattern to that of surface expression of the respective receptors. We conclude that 1) blocking IL-1RAcP inhibits IL-1 signaling in D10S cells, 2) domains-II and III may be involved in complex formation with IL-1RI, 3) IL-1RAcP is not regulated as is IL-1RI in the same cells, and 4) IL-1 responsiveness is dependent on the expression of IL-1RI, not IL-1RAcP.

Animals↗
PubMed1998

Spontaneous and inducible cytokine responses in healthy humans receiving a single dose of IFN-alpha2b: increased production of interleukin-1 receptor antagonist and suppression of IL-1-induced IL-8.

The present study was to determine whether the administration of a single dose of interferon-alpha2B (IFN-alpha2B) to healthy humans affects endogenous (or basal level) or inducible cytokines in a whole blood, ex vivo culture. Twenty-four healthy volunteers received an s.c. injection of IFN-alpha2b (3 x 10(6)U), and 4 volunteers received the vehicle as placebo. The study was blinded. Blood was drawn before and 3, 6, 12, and 24 h after the injection and incubated in the presence or absence of lipopolysaccharide (LPS) or interleukin-1beta (IL-1beta). After 24 hs, the plasma was assayed for tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, IL-1beta, IL-1 receptor antagonist (IL-1Ra), and IL-8. Treatment with IFN-alpha2b was associated with a 4.8-fold increase in the endogenous production of IL-1Ra in cultured blood sustained over 24 hs. In contrast, no change in endogenous IL-1Ra production was detected in the controls. A significant suppression (75%, p < 0.001) of IL-1beta-induced IL-8 production 3 and 6 h after IFN-alpha2b compared with control subjects was observed. These effects were also observed when IFN-alpha2b was added directly to whole blood cultures in vitro. In contrast to IL-1 stimulation, LPS stimulation of blood from IFN-alpha2b-treated subjects resulted in enhanced IL-1beta and TNF-alpha production. These results suggest that a single dose of IFN-alpha2b induces an anti-inflammatory state for endogenous stimuli but a proinflammatory state for exogenous endotoxin.

Adult↗
PubMed1998

Glucocorticoid effects in the human placenta: evidence that dexamethasone-mediated inhibition of fibronectin expression in cytotrophoblasts involves a protein intermediate.

Oncofetal fibronectin is an extracellular matrix protein that is suggested to play an important role in regulating adherence at uterine-placental interfaces. The purpose of the present study was to elucidate a mechanism through which glucocorticoids (GCs) inhibit the synthesis of FN in human placenta as part of their matrix-suppressive action near parturition. We observed that treatment of cytotrophoblasts isolated from human term placentas for 48 h with 10(-7) mol/L dexamethasone (DEX) down-regulated levels of FN expression to 13-19% of control levels in immunoprecipitation, Northern blotting, and enzyme-linked immunosorbent assay experiments. Conversely, GC treatment increased FN expression in placental fibroblasts to 164-310% of control levels in Northern blotting and enzyme-linked immunosorbent assay procedures, suggesting that GC-mediated suppression of FN expression is specific to cytotrophoblasts. Results indicated that the DEX-mediated suppression of FN expression in cytotrophoblasts was not mediated through changes in the stability of FN messenger ribonucleic acid (mRNA). Run-on transcription assays using isolated nuclei suggested that GC treatment did not markedly affect transcription of the FN gene in cytotrophoblasts. To test whether the GC-mediated suppression of FN expression was mediated through a protein intermediate, levels of FN mRNA were examined by Northern blotting in cells treated for 48 h with and without 10(-7) mol/L DEX and cycloheximide (CHX; 125 ng/mL). We observed that CHX treatment increased FN expression in DEX-treated cells to 91% of control values. We noted that whereas the presence of 100-300 ng/mL CHX reversed the DEX-mediated inhibition of FN mRNA expression in cytotrophoblasts, it did not alter the overall rates of protein synthesis in DEX-treated and control cells. These data suggest that suppression of FN mRNA expression by GC in cytotrophoblasts requires de novo protein synthesis and is mediated through a short lived intermediate, the synthesis of which is inhibited at low concentrations of CHX. Thus, GC-induced protein intermediates may influence uterine-placental adherence by modulating levels of oncofetal FN at sites of uterine-placental contact.

Blotting, Northern↗
PubMed1998

Overview of interleukin-18: more than an interferon-gamma inducing factor.

Initially described in 1989 as interferon-gamma (IFN-gamma) inducing factor (IGIF), interleukin-18 (IL-18) is a novel pro-inflammatory cytokine that is clearly more than an inducer of IFN-gamma. The cytokine possesses several biological properties such as activation of nuclear factor-kappaB (NF-kappaB), Fas ligand expression, the induction of both CC and CXC chemokines, and increased production of competent human immunodeficiency virus. Most activities are due to a receptor complex that recruits the IL-1 receptor-activating kinase (IRAK), leading to translocation of NF-kappaB. This property and others support the concept that IL-18 is related to the IL-1 family. Indeed, one of the IL-18 receptor chains is the IL-1 receptor-related protein, a member of the IL-1R family. In addition, IL-18 is structurally similar to IL-1beta and like IL-1beta is first synthesized as a leaderless precursor requiring the IL-1beta converting enzyme for cleavage into an active molecule. The biology of IL-18 is reviewed in the overview and the implication for a role for this cytokine in disease is presented.

Animals↗
PubMed1997

Re-evaluation of optimal dose of contrast medium for vascular enhancement in CT of the head and neck.

Adequate contrast enhancement of major neck vessels is more important than that of a tumour itself in CT of most head and neck tumours because of differentiation from neck node metastases. Our purpose was to re-evaluate the dosage of contrast medium for adequate vascular enhancement in CT of the head and neck. In a blind prospective fashion, 60 patients with a variety of head and neck lesions were randomised into three equal groups receiving 0.75, 1.0, or 1.25 ml/kg of meglumine ioglycate, 300 mg/ml. Contrast medium was administered by injector at 2 ml/s. The scan time and interscan delay were each 1 s, and total scan time 50-180 s. The scan was started immediately after administration of two-thirds of the contrast medium. The degree of vascular enhancement was assessed visually and quantitatively. We visually scored the degree of vascular enhancement as excellent (4 points), good (3), fair (2) or poor (1). For quantitative study, after measuring the CT numbers of the common or internal carotid artery (CA), internal jugular vein (IJV) and adjacent muscle at three levels, were calculated mean vessel/muscle contrast ratios. The degree of enhancement of the CA and IJV tended to increase with dose of the contrast media, but no examination was rated as showing poor enhancement in any group. The mean visual assessment scores for 0.75, 1.0, and 1.25 ml/kg were 2.7, 2.9 and 3.1, respectively; the mean ICA/muscle contrast ratios were 1.58, 1.55 and 1.63, and those of IJV/ muscle 1.65, 1.59 and 1.59. There was no significant difference between visual and quantitative assessment in any group. The results suggest that 0.75 ml/kg of contrast medium appears sufficient for vascular opacification for head and neck lesions when the CT scan can be completed in about 120 s.

Adolescent↗
PubMed1997

Fluorescence polarization immunoassay of progesterone.

A homogeneous fluorescence polarization immunoassay (FPIA) was developed to measure levels of progesterone in urine using a TDx analyzer in photocheck mode (Abbott Labs). Two tracers of ethylenediamine fluorescein thiocarbamyl (EDF) were employed; one was synthesized from 11 alpha-hydroxyhemisuccinate progesterone (Prog-11OH-HS) and the other was synthesized from 3-(o-carboxymethyl)oxime progesterone (Prog-3CMO). Each derivative of progesterone was conjugated with bovine serum albumin and used as an immunogen which produced monoclonal antibody clone 15A (MAb 15A, anti-Prog-11OH-HS) and clone 2B7 (MAb 2B7, anti-Prog-3CMO), respectively. Different combinations of tracers and antibodies were investigated in the FPIA system. Similar sensitivity was observed when using the pair, MAb 2B7 and its homologous tracer, Prog-3CMO-EDF, or MAb 15A and its homologous tracer, Prog-11OH-HS-EDF. In this immunoassay, no separation step was required and the total time for an assay of 10 samples was approximately 7 min. The progesterone detection limit in a 10 microliters sample was 3 ng/ml. The cross-reactivity results indicate that the A-, B- and D-ring of a steroid are buried in the binding pocket of MAb 15A, while the C-ring faced outward, resulting in cross-reactivity with 11-alpha hydroxy progesterone. The A-, B- and C-ring of a steroid of MAb 2B7, in contrast, are buried deep in the pocket leaving the D-ring facing outward, resulting in some different degrees of cross-reactivity with C17 position substituted steroids.

Fluorescence Polarization Immunoassay↗
PubMed1995

Use of progesterone-3(O-carboxymethyl oxime)-horseradish peroxidase in a sensitive microtitre-plate EIA and its application to a visual membrane EIA of progesterone.

A simple method of visual membrane enzyme-immunoassay (EIA) for the detection of progesterone is described. When two types of progesterone-horseradish peroxidase (HRP) tracers were challenged for binding, in the presence of progesterone, to the monoclonal anti-progesterone antibody, 15A, coated on the microtitre plate, the HRP conjugated at the C-3 position (A-ring) of progesterone competed more effectively with progesterone to the binding site of the monoclonal antibody (mAb) than HRP conjugated at the C-11 position of the C-ring. By using this combination of mAb, 15A, and progesterone-3(O-carboxymethyloxime)-HRP (P-3CMO-HRP), we developed a visual membrane EIA system in which free progesterone in the sample could be quantified by the degree of color development. In this system, free progesterone competed with P-3CMO-HRP for binding sites of mAb immobilized on the nitrocellulose membrane. The stable grey color was formed on the surface of membrane for progesterone-negative and no color for progesterone-positive sample using 3,3'-diaminobenzidine (DAB) with Co2+ as an insoluble substrate solution. To examine whether tetramethylbenzidine (TMB) can substitute for DAB in membrane EIA, an experiment was conducted where TMB was used as an insoluble substrate.

3,3'-Diaminobenzidine↗
PubMed1995

Doppler sonography in experimentally induced acute renal failure in rabbits. Resistive index versus serum creatinine levels.

RATIONALE AND OBJECTIVES: The purpose of this study is to investigate the temporal relation between the change in the resistive index (RI) from renal Doppler sonography and that of serum creatinine values in the course of experimentally induced reversible acute renal failure (ARF) in rabbits. METHODS: Reversible ARF was induced in 10 New Zealand white rabbits by injecting a glycerol solution (6.0 mL/kg) into the thigh muscle. Doppler sonography was performed before injection, and 6, 12, and 24 hours, and 3, 5, 7, and 14 days after injection of glycerol. Blood samples for measuring serum creatinine levels were obtained in the same time sequence. Three rabbits, which died during the course of the experiment, were excluded from the study group. RESULTS: The RI elevated rapidly after glycerol injection, peaked at 12 hours, and then decreased to normal values by 7 days. Conversely, serum creatinine values were elevated and peaked at 1 day and then decreased to normal by 14 days. The change in the RI preceded the change in serum creatinine levels in the course of reversible ARF. There was a weak linear correlation between RI and serum creatinine levels, with a correlation coefficient of 0.33. CONCLUSION: Doppler sonography with measurement of resistive index may be useful in predicting the course of ARF.

Acute Kidney Injury↗
PubMed1993

Influence of the conjugation site on the specificity of monoclonal antibodies to progesterone and on the performance of direct enzyme immunoassay.

Monoclonal antibodies against progesterone conjugated to carrier protein through substituent on the A-ring (C3 position ) or the C-ring (C11 position) of progesterone were used in the enzyme immunoassay. Antibody specificities were determined by testing the ability of 11 represensitive steroids to displace labelled progesterone in a competitive enzyme immuno-assay (EIA) and a radioimmunoassay (RIA). Immunization with progesterone conjugated to BSA through substituent on the A-ring (C3) resulted in the formation of monoclonal antibody (mAb) which fairly specific for progesterone. While immunization with progesterone at the 11-position (C11) resulted in the mAbs which were very specific for progesterone. The best EIA system was developed by using mAb against progesterone-11 alpha -hemisuccinyl BSA and tracer of progesterone-3(O-carboxymethyl oxmine)-horseradish peroxidase. Our approach is to confirm the overall orientation of the steroid in the binding site. Immunobiochemical analysis of mAb suggested that the D-ring is substantially more buried in the binding pocket than the A-ring. Our assay was designed to use the reagent inactivating cholesterol binding globulin in serum so that the extraction of the hormone into organic solvent was unnecessary. Therefore, our assay system can detect directly and rapidly the progesterone level in serum within one hour.

Animals↗
PubMed1992

Solid-phase immunoassay using a flow cytometer: quantitative and qualitative determination of protein antigens and a hapten.

A fluoroimmunoassay employing a flow cytometer as the fluorescence-detecting device is described. Three kinds of antigens, murine immunoglobulin (Ig), human chorionic gonadotropin (hCG) and progesterone were chosen as examples of the assay using fluorescein-labeled antibodies. Cyanogen bromide-activated agarose beads were used as solid-phase supporters. The flow cytometric immunoassay was applied to both qualitative and quantitative analyses; determination of murine Ig isotypes, quantitative determination of Ig, hCG and a hapten, progesterone. This assay produced very reproducible and less-fluctuating data since thousands of particles in the assay were collected and processed to produce a single value for fluorescence intensities. Furthermore, the working range of the assay in terms of antigen concentration was much broader than that of enzyme immunoassay. Therefore, we believe that microparticles like agarose beads could be useful solid-phase supporters in immunoassay, and the flow cytometer could provide a reliable alternative to the fluorescence-detecting device in immunoassay.

Animals↗
PubMed1992

Retrieval of intravascular foreign bodies with the snare and catheter capture technique.

The authors report two cases of retrieval of iatrogenically placed intravascular metallic foreign bodies: a guide wire in the abdominal aorta and a guide-wire fragment in the inferior vena cava. The foreign bodies were retrieved with use of a new approach described as the "snare and catheter capture technique." This technique is useful with guide wires that are too stiff to safely remove doubled over.

Aorta, Abdominal↗
PubMedDate not supplied

Iatrogenic dissection of the celiac artery and its branches during transcatheter arterial embolization for hepatocellular carcinoma: outcome in 40 patients.

PURPOSE: To study the sequelae of iatrogenic dissection of the celiac axis and its branches in a large patient population. METHODS: We analyzed 40 patients with hepatocellular carcinoma (HCC) whose celiac artery or its branches were dissected during transcatheter arterial embolization (TAE) and underwent follow-up angiography within 2 months. RESULTS: The two most common sites of dissection were the celiac artery in 13 patients (32.5%) and the proper hepatic artery in 11 patients (27.5%). Follow-up angiography revealed complete recanalization in 32.5% (13/40), irregularity and narrowing of the lumen in 40% (16/40), and complete obstruction in 27.5% (11/40). Therefore, 72.5% (29/40) of the dissected arteries recanalized. Pseudoaneurysm formation of the dissected artery was observed in 32.5% (13/40). Subsequent TAE was possible via the dissected arteries in 79% (27/34) of patients in this series. CONCLUSION: Iatrogenic dissection of the celiac and proximal hepatic arteries heals spontaneously in the majority of patients, and in most instances allows subsequent TAE.

Adult↗
PubMedDate not supplied

MR findings of secondary hemochromatosis: transfusional vs erythropoietic.

OBJECTIVE: The aim of this study was to demonstrate the MR characteristics of secondary hemochromatosis (transfusional versus erythropoietic). MATERIALS AND METHODS: Magnetic resonance images of five patients with transfusional (n = 3) or erythropoietic (n = 2) hemochromatosis were reviewed. RESULTS: The liver of all patients had low signal intensity in all pulse sequences. The spleen had low signal intensity in all patients with transfusional iron overload, but normal signal intensity in erythropoietic hemochromatosis, which had similar MR findings to idiopathic hemochromatosis. However, the pancreas had variable signal intensity. CONCLUSION: On MRI the signal intensity of the spleen may allow distinction between transfusional and erythropoietic hemochromatosis.

Adult↗