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T W Chung

Publications and source records attributed to T W Chung.

At least 37 records · Page 2Linked to original sources
PubMed1997

Cloning of the human cDNA sequence encoding the NADH:ubiquinone oxidoreductase MLRQ subunit.

A cDNA clone encoding human NADH:ubiquinone oxidoreductase (complex I of mitochondrial respiratory chain) MLRQ subunit was isolated from human fetal liver cDNA library. The clone contained an open reading frame of 246 by which predicted a protein comprising 81 amino acids with a calculated molecular weight of 9,370 Da. The deduced amino acid sequence exhibited 95% homology (88% identity and 7% favored substitution) to that of bovine MLRQ subunit. Northern analysis revealed that the cDNA clone hybridized with a 0.7 kb mRNA species which was present in all tissues examined. The expression level of the 0.7 kb mRNA in heart, skeletal muscle, and brain was higher than in other organs. Human MLRQ cDNA could cross-hybridize with the genomic DNAs from various species.

Amino Acid Sequence↗
PubMed1997

Differential expression of ferritin heavy chain in THP-1 cells infected with Mycobacterium bovis BCG.

To identify the host genes induced or suppressed by infection of mycobacteria, the reverse transcriptase polymerase chain reaction (RT-PCR) and the differential display reverse transcriptase polymerase chain reaction (DD RT-PCR) methods were used. In this study, cDNAs complement to mRNA extracted from human peripheral monocyte derived naive THP-1 cells, THP-1 cells infected with live Mycobacterium bovis BCG, THP-1 cells treated with heat-killed BCG, and THP-1 cells incubated with IgG-coated glass-beads were compared on the sequencing gel. One (TG2-1) of the clones selected by DD RT-PCR is 446 bp long and is identical to human ferritin heavy (H) chain gene. Northern blot analysis confirmed that ferritin H chain gene has been markedly over-expressed in monocytic THP-1 cells incubated with live and dead M. bovis BCG. Differential display techniques of host genes whose expression levels were varied by infection of mycobacteria could provide information about the response of macrophages to mycobacterial infection.

Amino Acid Sequence↗
PubMed1997

Viscosity measurements for LEH suspended in different plasma expanders.

To investigate the possibility of hemodilution with oxygen carrying fluid, we measured the viscosity effects of LEH which was suspended in different weight percentage of plasma expanders for different shear rates. All of LEH/Plasma expander suspensions show shear thinning flow behavior, and the viscosity of those suspensions increase with increased the weight percentage of each expander in suspensions for a fixed shear rate. Compared the viscosity data to those of human blood at 40% of hematocrit, LEH/albumin suspensions contained with 4% to 8% of albumin are the most suitable, whereas LEH/dextran (Dex) suspensions contained with 6% Dex70c is the least favorable suspension media for LEH. In point of viscosity effects, hemodilution with LEH/albumin or LEH/0.9% oxypolygelatin (Gel) may be valuable for further testing their efficacy in animal model.

Animals↗
PubMed1996

Sequence analysis of the 5'-flanking region of the gene encoding human N-acetylglucosaminyltransferase III.

We have isolated and characterized the immediate (1651 bP) 5'-flanking region of the gene (GnT-III) encoding N-acetylglucosaminyltransferase III (GnT-III) from a human placental genomic library. Analysis of promoter elements shows a similarity to the 5'-flanking region of murine 1,4-galactosyltransferase. The sequence lacks obvious TATA elements and CCAAT boxes; however, putative regulatory sites, including 2 potential cAMP-response regulatory elements (CRE), 11 insulin-response element consensus sequences (IRE), 7 potential AP-2 binding sites, 2 SP1 consensus sequences (GC boxes) and 2 sequences similar to the half-palindromic glucocorticoid-responsive element (GRE), are present.

Amino Acid Sequence↗
PubMed1996

Knowledge and attitudes about smoking in medical students before and after a tobacco seminar.

A 3-hour seminar on tobacco was introduced to second year (pre-clinical) medical students in Hong Kong in 1994. The differences in knowledge and attitudes were measured by a self-administered and anonymous questionnaire with 14 items before the seminar (n = 145), and again 2 weeks after the seminar (n = 151). The students also completed an evaluation form at the end of the seminar. Before the seminar, the students were most deficient in their knowledge on the exact magnitude of the risks from smoking and on the risks from smoking relative to the risks from air pollution and asbestos. After the seminar, their knowledge increased significantly (P < 0.005). As for attitudes, in the pre-test 35% strongly agreed that tobacco advertising should be completely banned, and 50% did so in the post-test (P = 0.02). The corresponding figures for banning of all forms of tobacco promotion were 26% and 43% (P < 0.005). In the pre-test, one in four students strongly disagreed that doctor's advice to their patients to stop smoking is totally ineffective, with this proportion increasing to 70% in the post-test (P < 0.005). The majority of the students stated that the seminar was useful. The preclinical medical curriculum should, at the very least, include a tobacco seminar. Our survey shows that it is effective in improving students' knowledge and attitudes on tobacco control.

Adult↗
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

A rheological equation to express the relations among hemoglobin contents, hematocrits, and viscosity of hemosome.

The relations among hemoglobin contents, hematocrit and viscosity of hemosome at a fixed shear rate have been studied. These relations can be well fitted by a rheological equation with internal viscosity of hemosome, (Tk)h, as a parameter. Where, (Tk)h are correlated (r = 0.996) with logarithm of hemoglobin content of hemosome by an equation: (Tk)h = 0.315 ln (hemoglobin contents of hemosome) + 0.435. The correlation can serve as an alternative way to predict hemoglobin content of hemosome instead of Benesch's method. The results of this study serve as a reference to determine an optimal conditions for in vivo tests of hemosome.

Animals↗
PubMed1994

A model for analyzing the formation of thrombin in vessels.

A pseudo steady-state model is proposed to analyze the effects of a vessel-length, blood-flow velocities, and the concentration levels of Va/Xa/phospholipid complex on the formation of thrombin in an arterial vessel. The outlet concentrations of thrombin are calculated in either physiological or pathological coagulation process. Among those factors, blood-flow velocity is the most important factor which affects the amount of thrombin formation. The model and its results might be used as a reference for those who clinically manage coagulation problems of patients with severe sepsis.

Arterioles↗
PubMed1994

Rheological parameter alternations in blood may impair oxygen transported to the retina in type II diabetes (NIDDM).

Rheological properties of blood, retinal capillary blood flow velocity and oxygen transport efficiency (TE) were measured and calculated from 21 type II diabetic patients (NIDDM) and 19 normal subjects. The results showed that the diabetes group had increased plasma viscosity and blood viscosities (P < 0.05 or better) at all tested shear rates. For both shear rates (gamma) of 225 sec-1 and 450 sec-1, the diabetes group displayed increased internal viscosity of red cells (Tk) (P < 0.002 and P < 0.001, respectively) but lower values of TE (P < 0.001, both). A lower value of retinal capillary blood flow velocity (P < 0.005) was also noted. Upon further analysis of possible relations between Hct values and Tk of red cells, it was found that Hct values were linearly correlated with Tk for both shear rates of the diabetes group (gamma = 225 sec-1 and gamma = 450 sec-1; R = -0.63 and -0.65, n = 21 and 19, respectively, both P < 0.005); control group (gamma = 225 sec-1 and gamma = 450 sec-1; R = -0.84 and -0.82, respectively, n = 19, both P < 0.001) and all subjects (gamma = 225 sec-1 and gamma = 450 sec-1; R = -0.70 and -0.72, n = 40 and 38, respectively, both P < 0.001). The impaired rheological properties of blood and internal viscosity of red cells may result in both reduced capillary blood flow velocities and less oxygen transported to tissues. This may possibly contribute to the deterioration of retinopathy or microangiopathy in diabetic patients.

Blood Flow Velocity↗
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

Increased red cell rigidity might affect retinal capillary blood flow velocity and oxygen transport efficiency in type II diabetes.

Retinal capillary blood flow velocity, oxygen transport efficiency (TE) and rheological properties of the blood were measured from twenty-two type II diabetes patients and nineteen normal subjects. The results showed that diabetic patients had increased plasma viscosity (P < 0.01). Also, for both shear rates of 225 sec-1 and 450 sec-1, they had increased blood viscosity (P < 0.002, both), red cell rigidity (Tk) (P < 0.002 and P < 0.001, respectively), but lower values of TE (P < 0.001, both), and of retinal capillary blood flow velocity (P < 0.005). Furthermore, TE was linearly correlated with Tk for both shear rates of all subjects (r = -0.80, gamma = 225 sec-1, P < 0.001; r = -0.84, gamma = 450 sec-1, P < 0.001). The impaired rheological properties of blood and red cell rigidity might result in both reduced capillary blood flow velocity and lower values of TE, which then possibly contribute to the deterioration of retinopathy or microangiopathy in diabetic patients.

Adult↗
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↗
PubMed1991

Structural role of amino acids 99-110 in recombinant human erythropoietin.

Erythropoietin is the prime regulator of red blood cell production. Previous studies demonstrated that antipeptide antibodies to amino acids 99-119 and 111-129 bind to two non-overlapping domains and inhibit the hormone's action (Sytkowski, A.J. & Donahue, K. A. (1987) J. Biol. Chem. 262, 1161-1165). Oligonucleotide-directed mutagenesis now shows that amino acids 99-110 (domain 1) but not 119-129 (domain 2) are important to erythropoietin's structure and function. Mutagenesis of wild-type human erythropoietin cDNA was used to produce a series of mutant proteins with sequential deletion of three adjacent amino acids and insertion of the sequence Glu-Phe across the two domains. Transient expression in COS-7 cells revealed 2.0-kb transcripts encoded by all of the cDNAs. Domain 2 mutants exhibited specific biological activities similar to that of the wild type. In contrast, domain 1 mutants were not secreted. In vitro transcription and translation of the domain 1, domain 2 and wild-type cDNAs resulted in the isolation of 23.5-kDa and 32-kDa proteins in the absence or presence of pancreatic microsomes, respectively, consistent with efficient translation of all of the mutants and equivalent post-translational processing of each protein. The data suggest that mutation within domain 1 results in the intracellular biosynthesis of erythropoietins with altered structure, rendering them subject to rapid degradation. The bioassay of erythropoietins synthesized entirely in vitro demonstrated that domain 1 mutants were inactive, whereas both wild type and domain 2 mutant hormones exhibited biologic activity. The results are consistent with a critical role for amino acids 99-110 in the structure of human erythropoietin.

Amino Acid Sequence↗
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↗
PubMed1991

Survival factors in a canine septic shock model.

Physiological indicators of tissue perfusion in a canine septic shock model have been examined. An early death (ED) group and a combined late death and survivor group (LDS) were defined and the corresponding data compared. It was found that the LDS group had less reductions in mean systemic arterial pressure (P less than 0.05), transcutaneous oxygen pressure (P less than 0.05), and red blood cell deformability (P less than 0.001); a smaller increase in hematocrit (P less than 0.05); and a lower concentration of white blood cells (P less than 0.05), relative to the ED group, at 6 hr after an infusion of Escherichia coli organisms. These results suggest that dogs in the LDS group have better tissue perfusion than those in the early death ED group. Post-treatment of dogs with pentoxifylline did not improve survival time or enhance flow factors.

Animals↗
PubMed1975

Effect of lactate dehydrogenase isoenzymes on the coupled enzymatic assay for alanine aminotransferase activity.

We show an example of the importance of specifying the form of isoenzyme and source of indicator enzymes to be used in coupled enzymatic assays. When we compared H-4 (pig heart) and M-4 (rabbit muscle) isoenzymes of lactate dehydrogenase for their suitability as indicator enzymes in the assay for alanine aminotransferase activity, we found that about fourfold as much M-4 as H-4 was required in terms of lactate dehydrogenase activity to reflect accurately equivalent amounts of alanine aminotransferase activity. Moreover, the substrate specificities of the two isoenzymes differed quantitatively.

Alanine Transaminase↗