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Biomedical subjects

M J Choi

Publications and source records attributed to M J Choi.

At least 55 records · Page 3Linked to original sources
PubMed1994

Adenosine deaminase and carcinoembryonic antigen in pericardial effusion diagnosis, especially in suspected tuberculous pericarditis.

BACKGROUND: Adenosine deaminase (ADA) and carcinoembryonic antigen (CEA) have been measured in pleural fluid to help distinguish malignant from benign effusions, especially in tuberculous pleurisy. We investigated ADA and CEA levels in patients with moderate to large pericardial effusions of different etiologies. METHODS AND RESULTS: We performed diagnostic and therapeutic pericardiostomy with drainage and biopsy. We measured ADA and CEA levels in the pericardial fluid in 26 patients with moderate to large pericardial effusion and 19 control patients. Patients were included in a prospective protocol from August 1991 to August 1993. Patients were grouped as follows: group 1, 9 patients with tuberculous pericarditis (TP) confirmed by bacteriologic culture or histology of pericardial biopsy; group 2, 5 patients with clinically strongly suspected TP; group 3, 12 patients with malignancy (8) and acute pericarditis (4); group 4, 19 control patients without pericardial disease. We treated patients with TP with isoniazid, rifampin, and either streptomycin or ethambutol for 12 months and pyrazinamide for 2 months. We observed for symptoms and signs of recurrent pericarditis or constrictive pericarditis on follow-up. In group 1 the ADA activity was significantly higher (101 +/- 14 U/L) than that in group 3 (22 +/- 5 U/L) or that in group 4 (17 +/- 2 U/L) (P < .05). There was no significant difference between ADA activity in group 1 (101 +/- 14 U/L) and that in group 2 (100 +/- 26 U/L). With a cutoff value for ADA activity of 40 U/L, sensitivity was 93% and specificity 97% in the diagnosis of TP. In benign diseases, the CEA level was significantly lower (1.0 +/- 0.3 ng/mL) than that in malignant diseases (135.1 +/- 79.7 ng/mL) (P < .05). With a cutoff value for CEA level of 5 ng/mL, sensitivity was 75% and specificity 100% in the diagnosis of malignant pericarditis. Follow-up study (mean, 12.9, 19.8, and 11.8 months in groups 1, 2, and 3, respectively, showed no symptoms or signs of constrictive pericarditis, except for 1 patient. CONCLUSIONS: Pericardial fluid ADA and CEA are useful for the differential diagnosis of pericardial effusion of various causes. They also have great value in early diagnosis of TP, particularly when the results of other clinical and laboratory tests are negative.

Adenosine Deaminase↗
PubMed1994

A visual membrane immunoassay for the detection of methamphetamine using an enzyme-labeled tracer derived from methamphetamine and amphetamine.

A visual membrane enzyme immunoassay is described for the measurement of methamphetamine in urine. To increase assay sensitivity, tracers with chemically similar structures were cross-checked with the antibodies to determine their influence on the antibody binding. Tracers of horseradish peroxidase-labeled methamphetamine (MA-HRP) and amphetamine (A-HRP) derivatives were prepared for this purpose. Significant differences in antibody specificity were found between the two tracers. Based on the results of this study, a pair of an antibody and a tracer was selected and a membrane enzyme immunoassay (EIA) was developed utilizing the competitive binding between methamphetamine and the drug-HRP tracer. UltraBind membrane (0.45 micron) was used as the solid matrix to which the antibody was attached. Using diaminobenzidine substrate with Co2+ ion, a stable grey color appeared on the surface of membrane for MA-negative urine samples. No color appeared for MA-positive urine with a cut-off level of 0.8 ppm.

Amphetamines↗
PubMed1993

The influence of fluid properties and pulse amplitude on bubble dynamics in the field of a shock wave lithotripter.

This study concerns the radial dynamics of a bubble driven by pulsed ultrasound of the type generated during extracorporeal shock wave lithotripsy. In particular, a numerical model has been used to examine the sensitivity of the bubble oscillations to changes in both the amplitude of the driving field and the physical conditions of the fluid surrounding the bubble: viscosity, surface tension, temperature and gas content. It is shown that, at high negative pressures (p- = 10 MPa) as in lithotripsy, the timing and amplitude of bubble collapses have a considerably reduced sensitivity to the initial bubble size and all fluid parameters, except gas content, compared with those expected in lower-amplitude fields (p- = 0.2 MPa). This study indicates that, in the lithotripsy fields, the differences in the viscosity, surface tension and temperature of body fluids and the initial bubble size will have little effect on bubble dynamics compared with those expected in water.

Humans↗
PubMed1993

Production and characterization of monoclonal antibody that simultaneously recognizes methamphetamine and its major metabolite.

A series of monoclonal antibodies (mAbs) that react with methamphetamine-bovine serum albumin (MA-BSA) were established by intrasplenic immunization method. Among established 36 clones, two typical mAbs, designated NK-1 and NK-2, were described. The inhibition assay of enzyme-linked immunosorbent assay (ELISA) analysis using methamphetamine analogs indicated that NK-1 showed considerable reactivity not only MA-BSA but also methamphetamine and its major metabolite, para-hydroxymethamphetamine (p-hydroxymethamphetamine). The cross-reactivity between NK-1 and the methamphetamine analogs with modified alkyl side chain, indicates that methyl groups of R5 and R7 in the methamphetamine molecules are important for the maximum affinity. The length of alkyl side chain on methamphetamine significantly affected the binding affinity of NK-1. The results may suggest that NK-1 will recognize not only methamphetamine but also the bridge part of the methamphetamine that binds the methamphetamine molecules to a carrier protein.

Animals↗
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

Acoustic emission and sonoluminescence due to cavitation at the beam focus of an electrohydraulic shock wave lithotripter.

The acoustic emission from cavitation in the field of an extracorporeal shock wave lithotripter has been studied using a lead zirconate titanate piezoceramic (PC4) hydrophone in the form of a 100-mm diameter focused bowl of 120-mm focal length. With this hydrophone directed at the beam focus of an electrohydraulic lithotripter radiating into water, it is possible to identify signals well above the noise level, at the 1-MHz resonance of the hydrophone, which originate at the beam focus. Light emission, attributed to sonoluminescence, is also shown to originate at the focal region of the lithotripter, and the signal obtained from a fast photomultiplier tube directed at the focus has similarities in structure and timing to the detected acoustic signals. The multiple shock emission resulting from a single discharge of an electrohydraulic source is shown to result in two separate bursts of cavitational activity separated by a period of 3-4 ms. The signal burst corresponding to the primary shock has a duration of about 600 microseconds with little noticeable structure. The signal burst associated with the secondary shock has a reproducible structure with two distinct peaks separated by about 200 microseconds depending on the shock amplitude. THe timing and structure of each burst is shown to be in reasonable agreement with the theoretical predictions made by Church (1989) based on the Gilmore model of bubble dynamics. In particular, it is shown that it is possible to obtain precise measurements of the time delay between the separate peaks within the signal burst detected following the secondary shock and this may, as predicted, provide a method of determining the size of bubbles remaining after the primary shock.

Acoustics↗
PubMed1992

pH-sensitive liposomes containing polymerized phosphatidylethanolamine and fatty acid.

With the ultimate aim of targeting cancer drugs to malignant tissues, liposomes containing polymeric phosphatidylethanolamine and a fatty acid were prepared. For this purpose diacetylenic phosphatidylethanolamine (DAPE), a phosphatidylethanolamine containing diacetylene, was synthesized. Liposomes containing DAPE, fatty acid, and either phosphatidylethanolamine (PE) or phosphatidylethanolamine-beta-oleoyl-gamma-palmitoyl (POPE) were then prepared. Polymerization of DAPE was effected by UV illumination. The polymeric liposomes so obtained were stable at physiological pH but became leaky below pH 6.5. Of various compositions studied, the greatest pH-sensitivity was found with liposomes composed of 35 mol% DAPE, 35 mol% POPE, and 30 mol% saturated fatty acid. The presence of blood plasma albumin decreased vesicle stability while apolipoprotein A-I (apo A-I) had the opposite effect and plasma as a whole had a slightly stabilizing effect.

Apolipoprotein A-I↗
PubMed1991

Theoretical predictions of the acoustic pressure generated by a shock wave lithotripter.

A one-dimensional frequency domain model is used to predict the temporal peak acoustic pressures developed near the beam focus during extracorporeal shock wave lithotripsy (ESWL). The model includes consideration of finite amplitude effects, attenuation, diffraction and dispersion, and results are presented for the case of an electrohydraulic source with the beam geometry of the Dornier HM3 lithotripter. Propagation in castor oil, water and tissue is examined. The model predicts that nonlinear effects enhance the peak positive pressure (p+) at the beam focus in 6 cm of tissue in a Dornier type lithotripter by a factor of about 3 above that which would be expected for linear propagation. The negative peak pressure (p-), conversely, is predicted to be depressed by a factor of about 0.7 below the linear theory prediction. The model also indicates the occurrence of excess absorption due to shock formation. This is shown, for a Dornier HM3 type lithotripter, to cause a reduction in the peak positive pressure gain and a broadening of the focal depth as the output of the source is increased. A threshold aperture pressure is identified for a source with the same beam geometry as the Dornier HM3 below which shock formation does not occur. In this region the pressure gain increases and the focal depth narrows as the source output increases. These effects are characteristic of current commercial piezoelectric and electromagnetic lithotripsy fields.

Humans↗
PubMed1991

Simple enzyme immunoassay for the simultaneous measurement of whole choriogonadotropin molecules and free beta-subunits in sera of women with abnormal pregnancies or tumors of the reproductive system.

A multiple enzyme immunoassay (multi-EIA) was developed to quantify whole-molecule human choriogonadotropin (w-hCG) and free hCG beta-subunits (hCG-beta) simultaneously. A clone of a specific monoclonal antibody was coupled to solid phase; two other clones of different monoclonal antibodies were conjugated to horseradish peroxidase (HRP; EC 1.11.1.7) and alkaline phosphatase (AP; EC 3.1.3.1), respectively. These two enzyme conjugates were mixed together to measure w-hCG or hCG-beta, depending on the selection of the enzyme substrate. To measure w-hCG and hCG-beta simultaneously, both enzyme substrates were used with the blended enzyme conjugates. The assay is simple and reproducible, and can be completed within 2 h with high specificity and sensitivity. We measured w-hCG and hCG-beta in the sera of women with abnormal pregnancies and in patients with tumors of the reproductive system, and observed different hCG-beta/w-hCG ratios in patients with various types of trophoblastic tumors.

Antibodies, Monoclonal↗
PubMed1989

Spontaneous maturation of follicular oocytes in Rana dybowskii in vitro: seasonal influences, progesterone production and involvement of cAMP.

Seasonal and hormonal influences regulating oocyte maturation (germinal vesicle breakdown, GVBD) in ovarian follicles of Rana dybowskii were investigated. During the early winter (Dec.-Jan.) GVBD occurred at a low incidence following in vitro culture of intact follicles. Addition of progesterone of frog pituitary homogenate (FPH) to such follicles induced oocyte maturation, whereas IBMX or forskolin inhibited hormone-induced oocyte maturation. The time course of spontaneous in vitro maturation varied markedly with the seasons and between animals. Follicles isolated from the ovaries in early February required 21-24 hours of culture to mature spontaneously, and addition of FPH or progesterone to the culture medium markedly accelerated the time course of GVBD. In contrast, follicles isolated in late February matured very rapidly (less than 6 hours), and FPH or progesterone were ineffective in accelerating the time course of GVBD. IBMX and forskolin separately or in combination stimulated follicular progesterone production, which resembled that seen following FPH stimulation. FPH addition to such follicles shifted the steroid peak to the left (accelerated) and increased the absolute amount of hormone detected in late-maturing follicles (50% GVBD, about 18 hours) but not in rapidly maturing follicles (50% GVBD, 3 hours). In contrast to other amphibians, a high incidence of spontaneous oocyte maturation occurred during in vitro culture. Essentially all animals exhibited spontaneous maturation during the normal breeding season, even those animals collected in the early winter and kept in artificial hibernation at 4 degrees C for extended periods.

Animals↗
PubMed1989

An experimental shock wave generator for lithotripsy studies.

An electrohydraulic shock wave generator has been constructed to facilitate investigation of the acoustic field generated during extracorporeal shock wave lithotripsy (ESWL). Pressure waveforms at the generator aperture and the beam focus, measured using a PVDF needle hydrophone, are compared with those from a commercial lithotripter, the Dornier HM3.

Acoustics↗
PubMedDate not supplied

Production and characterization of monoclonal antibodies specific to atrazine group compounds: effects of coating ligand structure on the variation of sensitivity and specificity.

Hybridoma cells were prepared by immunizing mice with carboxylic derivatives of atrazine conjugate to bovine serum albumin. After the screening of culture supernatant of hybridomas, five cell lines producing monoclonal antibodies were established and 1.8-5.3 ml of ascitic fluid per mouse was obtained from each cell line. The protein A affinity purification yielded 0.35-0.65 mg per ml of ascitic fluid from each cell line. The characterization studies in terms of sensitivity and specificity indicate that MAb 2F9 and MAb 4B9 showed the best responses with atrazine and its group of ametryne and cyanazine, using microtiter plate coated with simazine derivative of 6-amino hexanoic acid; no cross-reactivity was shown with simazine and cyanuric chloride.

Animals↗
PubMedDate not supplied

Effects of low-intensity ultrasound (LIUS) stimulation on human cartilage explants.

OBJECTIVE: To evaluate the effects of low-intensity ultrasound (LIUS) stimulation on the anabolic state of human cartilage from patients with osteoarthritis (OA). METHODS: Explant cultures of human OA cartilage were stimulated for 10 min every day for 7 consecutive days using continuous-wave sonication at a frequency of 1 MHz with spatial and temporal average intensities of 0 (control), 40, 200, 500, or 700 mW/cm2. The effects of LIUS on cell proliferation were evaluated by 3H-thymidine incorporation. Proteoglycan synthesis was evaluated by the incorporation of 35S-sulfate and by Safaranin O staining. Collagen synthesis was evaluated by 3H-proline incorporation and immunohistochemistry. RESULTS: At an intensity of 200 mW/cm2, LIUS treatment induced the expression of collagen type II and proteoglycan measured by the incorporation of radioactivity and specific staining of the cartilage explants. However, the expression decreased again at the higher intensities of 500 or 700 mW/cm2. Ultrasound had no stimulatory effect on cell proliferation at any intensity. CONCLUSION: LIUS has anabolic effects on human cartilage in explant cultures, indicating a potentially important method for the repair of osteoarthritic cartilage.

Aged↗
PubMedDate not supplied

Drug testing at the 10th Asian Games and 24th Seoul Olympic Games.

Drug testing (doping test) procedures in the 1986 10th Asian Olympic Games and 1988 24th Seoul Olympic Games are reported. The International Olympic Committee Medical Commission (IOC-MC) conducted its first doping tests at the 1968 Olympics in Grenoble. With the guidance of the International Olympic Committee (IOC), the Olympic Council of Asia (OCA) introduced doping tests at the 1986 10th Asian Olympic Games in Seoul, Korea, September 21st to October 5th, 1986. 585 samples were tested at the Doping Control Center, Korea Advanced Institute of Science and Technology (DCC/KAIST), for stimulants, narcotics, anabolic steroids, and beta-blockers by gas chromatography/mass spectrometry, high pressure liquid chromatography, and fluorescence polarization immunoassay. These tests covered about 100 different drugs and another 400 as metabolites in addition to pharmacologically related substances. For the Seoul Olympic Games from September 17 to October 2, 1988, the IOC-MC with the DCC/KAIST conducted doping tests on 1601 samples for stimulants, narcotics, beta-blockers, diuretics, and anabolic steroids using GC, HPLC, GC/MSD, GC/MS, LC/MS, and TDx.

Doping in Sports↗