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Biomedical subjects

H K Chung

Publications and source records attributed to H K Chung.

At least 73 records · Page 4Linked to original sources
PubMed1994

Effects of combined cold and hyperbaric oxygen storage on free flap survival.

We have previously reported that hyberbaric oxygen (HBO) improved the survival rate of experimental free flaps. The purpose of this study was to evaluate the effects of combined hypothermia and HBO administered during storage on free flaps and on the xanthine oxidase system in rats. Epigastric skin flaps were stored cold for 48 and 72 hours either in room air or under HBO (2.9 atmospheres absolute, 100% oxygen) before free flap transfer. The success rates of free flaps were 80% (8/10) after 48 hours and 20% (2/10) after 72 hours of cold storage in room air. HBO produced no effect after 48 hours but significantly increased the success rate to 70% (7/10) after 72 hours of cold storage. Tissue hypoxanthine (plus xanthine) levels increased to 210% of normal after 48 hours of cold storage in room air and to 176% in HBO. Elevated hypoxanthine levels returned toward normal by 72 hours of cold storage in room air, while the increased levels remained under HBO. Xanthine oxidase activities significantly increased by 60 to 80% during 72 hours of room air storage. HBO treatment inhibited xanthine oxidase activity to 48% of normal by 72 hours of storage. Free flaps exhibited no significant alterations in GR and G6PDH activity after 48 hours of cold storage in room air or HBO. After 72 hours of cold storage, the room air control displayed a trend of decreasing GR activity and a significant 20% decrease in G6PDH activity, while HBO groups showed no significant alterations in both GR and G6PDH activity compared to normal. Protection of the antioxidative enzymes by hypothermia and inhibition of the xanthine oxidase activity by HBO appear to be one of the mechanisms of improved skin flap survival in free flaps.

Animals↗
PubMed1993

Biological exposure indices of organic solvents for Korean workers.

Biological exposure indices (BEIs) of toluene, perchloroethylene (PCE) and methyl ethyl ketone (MEK) for Korean workers were studied respectively. Exposure in workplace to organic solvents were measured by personal sampling. Blood toluene, blood PCE, urinary trichloroacetic acid and urinary MEK were determined by headspace GC. Urinary hippuric acid was determined by HPLC and corrected for creatinine. BEIs for Korean workers were calculated with the levels of the determinants corresponding to permissible exposure limits in Korea which were the same with TLV of ACGIH. Blood toluene level of 2.2 mg/l and urinary hippuric acid level of 1.7 g/g creatinine corresponded to exposure of 100 ppm toluene. Blood PCE concentration of 1.6 mg/l and urinary trichloroacetic acid concentration of 2.9 mg/l corresponded to exposure to 50 ppm PCE. Urinary MEK concentration of 1.4 mg/l corresponded to exposure to 200 ppm of MEK. In conclusion, BEIs for Korean workers determined in this study were different to ACGIH's BEI as urinary determinants were lower and blood determinants were higher than ACGIH's BEI.

Adult↗
PubMed1993

Radioimmunoscintigraphy of advanced gastrointestinal carcinomas employing I-131 labeled CEA-79 monoclonal antibody.

CEA-79 is a murine IgG2a type monoclonal antibody (MoAb) generated using purified CEA from culture supernatants of a human colon cancer cell line, LS174T. The association constant and immunoreactivity of the I-131 labeled CEA-79 ranged from 2.0 to 3.2 x 10(9) l/mole, and from 54 to 74%, respectively. The purpose of this study was to evaluate the feasibility of radioimmunoscintigraphy employing MoAb CEA-79 in patients with advanced gastrointestinal carcinomas. Two mgs of MoAb CEA-79 was labeled with 111 MBq (3 mCi) of I-131, and infused intravenously in 6 stomach cancer and 16 colon cancer patients. Out of 6 patients with stomach cancer, immunoscintigraphy was able to detect the tumors in 4 cases. However, immunoscintigraphy found out tumors in all patients with colon cancer. Moreover, 1 patient with stomach cancer and 2 patients with colon cancer showed increased uptake of MoAb in the tumor lesions despite normal serum levels of CEA. We could conclude that this antibody has a potential as a new imaging agent for the diagnosis of gastrointestinal carcinoma.

Adult↗
PubMed1992

Cloning and characterization of cDNAs coding for heavy and light chains of a monoclonal antibody specific for pre-S2 antigen of hepatitis B virus.

Binding specificity of a monoclonal antibody (mAb) (kappa, gamma 2b) H8 which can react with the pre-S2 peptide of hepatitis B virus (HBV) was determined by Western blot analyses. From the hybridoma cell line secreting mAb H8, poly(A)+ RNA was prepared and used as a template for cDNA synthesis and cloning. Full-length cDNAs coding for the heavy and kappa light chains of the mAb were cloned from the cDNA library and characterized by nucleotide (nt) sequence analyses and N-terminal amino acid sequencing. The sequence analyses revealed that both heavy and light chain-specific cDNAs are functional, and the variable regions of the heavy and light chains are members of mouse heavy chain subgroup III(c) and light chain group I, respectively. Comparison of the nt sequences with mouse immunoglobulin genes listed in the GenBank data base show that the cDNAs have not been previously reported. The cDNAs will be used for the construction of a therapeutic antibody for HBV infection.

Amino Acid Sequence↗
PubMed1992

Recombinant tissue plasminogen activator in acute myocardial infarction in the Chinese in Hong Kong.

Eighty-nine consecutive Chinese patients (69 males, 20 females) with acute myocardial infarction treated by 100 mg recombinant tissue plasminogen activator (7 intracoronarily, 82 intravenously) at 3.7 +/- 1.0 h after onset, and intravenous heparin or dipyridamole therapy started at 3 h, were studied prospectively. Their mean age was 59.6 +/- 10.6 yr. Forty-six patients (51.7%) had anterior and 39 patients (43.8%) had inferior infarcts. Clinical evidence of reperfusion were seen in 63 patients (70.8%), while new complications included hypotension (5.6%), heart failure (6.7%), cardiac arrhythmias (76.4%) majority of which are related to reperfusion and self-remitting, haematoma around vascular access sites (23.6%), melaena (3.3%) and cerebral infarction (2.2%). Maximal changes in coagulation profiles were seen at 3 h, including a decrease in fibrinogen by 64.2% and an increase in fibrin degradation products by 47 times. The changes in haemostatic variables were not related to body weight or bleeding complications. Nine patients (10.1%) had recurrence of angina and 6 patients (6.9%) died due to pump failure and reinfarction. Angiogram at 14 days confirmed TIMI 2 or 3 patency of infarct-related arteries in 63 out of 73 (86.3%) patients, with a mean global ejection fraction of 52.5 +/- 12.4%. Nearly all survivors could maintain class I-II functional status after discharge. The safety and promise of recombinant tissue plasminogen activator for acute myocardial infarction in the Chinese were confirmed.

Adult↗
PubMed1992

The impact of thrombolytic therapy on hospital mortality from acute myocardial infarction in the Chinese in Hong Kong.

Thrombolytic therapy using recombinant-tissue plasminogen activator, urokinase and streptokinase for acute myocardial infarction was instituted in the coronary care unit of the Prince of Wales Hospital in Hong Kong in 1988. To evaluate its impact on hospital mortality of acute myocardial infarction, the database of 465 patients (mean age 65.2 +/- 12.6 yr) admitted into the coronary care unit in the period between 1985-1990 was collected prospectively and their clinical course reviewed. Three hundred and thirty-five patients were males and 130 were females. Patients in the prethrombolytic era (1985-87) and the thrombolytic era (1988-90) were matched for age, proportion of females and clinical severity. One hundred and two patients (39.5%) received thrombolytic therapy. The overall hospital mortality (18.6%) in the thrombolytic era and that for each sex (18.2% in the males; 19.5% in the females) were significantly lower than those of prethrombolytic era (27.1%, 23.4% and 37.7%, respectively). No death was due to bleeding complication. The benefit of thrombolytic therapies in the Chinese was confirmed. More effort is needed to popularize this concept in the Chinese communities, to shorten the prehospital delay of patients and to extend its utilisation to the elderly patients.

Aged↗
PubMed1992

Recombinant tissue-plasminogen activator (rt-PA) in acute myocardial infarction in the Chinese in Hong Kong.

Eighty-nine consecutive Chinese patients (69 males, 20 females) with acute myocardial infarction treated by 100 mg recombinant tissue-plasminogen activator (rt-PA) (7 intracoronarily, 82 intravenously) at 3.7 +/- 1.0 hours after onset, and intravenous heparin or dipyridamole therapy started at 3 hours, were studied prospectively. Their mean age was 59.6 +/- 10.6 years. Forty-six patients (51.7%) had anterior and 39 patients (43.8%) had inferior infarcts. Clinical evidence of reperfusion was seen in 63 patients (72.8%), while new complications included hypotension (5.6%), heart failure (6.7%), cardiac arrhythmias (76.4%), hematoma around vascular access sites (23.6%), melena (2.2%) and cerebral infarction (2.2%). Maximal changes in coagulation profiles were seen at 3 hours, including a decrease in fibrinogen (by 64.2%), an increase in FDP by 11.7 times and D-dimers by 4.4 times. Nine patients (10.1%) had recurrence of angina and 6 patients (6.9%) died due to pump failure (5) and reinfarction (1). Angiogram at 14 days confirmed TIMI (2 or 3) patency of infarct related arteries in 62/81 (76.5%) patients, with a mean global ejection fraction of 52.5 +/- 12.4%. Nearly all survivors could maintain class I-II functional status after discharge. The safety and promises of rt-PA for acute myocardial infarction in the Chinese were confirmed.

Adult↗
PubMed1991

Vascularised osteocutaneous fibular transfer to the tibia.

We have reviewed 25 cases of vascularised osteocutaneous fibular transfers carried out between 1982 and 1988. The patients all had chronic osteomyelitis of the tibia, with extensive bone loss and associated soft tissue defects, following severely comminuted fractures. Union of the grafted bone could be seen in radiographs taken 3 to 4 months after operation. The results were generally satisfactory, but there were some complications.

Adult↗
PubMed1990

Purification and characterization of elongation factor G from bovine liver mitochondria.

The mitochondrial protein synthesis translocase elongation factor Gmt (EF-Gmt) from bovine liver has been purified to greater than 90% homogeneity by a combination of conventional gravity and high performance liquid chromatography. The purification scheme results in an approximate overall 14,000-fold purification with 2% total recovery of EF-Gmt activity. Gel filtration chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicate that the mitochondrial factor is a single polypeptide with a molecular weight of 80,000. EF-Gmt displays similar levels of activity on its homologous mitochondrial ribosomes and on Escherichia coli ribosomes. The mitochondrial translocase is sensitive to temperatures above 37 degrees C, but the factor is partially protected from heat inactivation in the presence of GTP or GDP. The activity of EF-Gmt is inhibited by treatment of the factor with N-ethylmaleimide. In contrast to all other translocases tested to date, EF-Gmt is completely resistant to the inhibiting effect of fusidic acid when tested on its homologous ribosomes. It displays weak sensitivity to this antibiotic when assayed in the presence of heterologous E. coli ribosomes.

Animals↗
PubMed1990

Molecular cloning and expression of a complementary DNA for inositol 1,4,5-trisphosphate 3-kinase.

A complementary DNA (cDNA) clone that encodes inositol 1,4,5-trisphosphate 3-kinase was isolated from a rat brain cDNA expression library with the use of monoclonal antibodies. This clone had an open reading frame that would direct the synthesis of a protein consisting of 449 amino acids and with a molecular mass of 49,853 daltons. The putative protein revealed a potential calmodulin-binding site and six regions with amino acid compositions (PEST regions) common to proteins that are susceptible to calpain. Expression of the cDNA in COS cells resulted in an approximately 150-fold increase in inositol 1,4,5-trisphosphate 3-kinase activity of these cells.

Amino Acid Sequence↗
PubMed1987

Purification of individual tRNAs using a monoclonal anti-AMP antibody affinity column.

A murine monoclonal anti-AMP antibody affinity matrix was used for isolation of individual species of amino acid transfer nucleic acids (tRNAs). The antibodies had been prepared using 5'-AMP covalently attached to bovine serum albumin as antigen and exhibited high affinity for 5'-AMP but greatly reduced affinity for 3'-AMP. Native uncharged tRNAs that terminate in a 5'-AMP group on the amino acid acceptor arm of the molecule bind tightly to the anti-AMP affinity matrix, whereas aminoacylated tRNAs are not retained. This allows separation of a particular tRNA species as its aminoacyl derivative from a complex mixture of uncharged tRNAs under very mild conditions.

Adenosine Monophosphate↗
PubMed1987

Purification of heat-labile enterotoxin from an enterotoxin from an enterotoxigenic Escherichia coli of human origin by monoclonal immunoaffinity chromatography.

Heat-labile enterotoxin (LT) was purified from an enterotoxigenic Escherichia coli 015H11 of human origin. The purification steps included French pressure cell disruption of the bacteria, salting-out, DEAE-Sephacel on chromatography. Application of this procedure resulted in a 95.1-fold purification of LT with a yield of 19.9% as determined by rabbit ileal loop assay. The final LT preparation showed only one protein-staining band on polyacrylamide gel electrophoresis, indicating that the purified LT was homogeneous.

Animals↗
PubMed1984

Conformation-specific monoclonal antibodies to glutamine synthetase in Escherichia coli.

Glutamine synthetase from Escherichia coli is composed of 12 identical subunits and exists in various forms: unadenylylated, adenylylated, divalent cation bound (taut), and divalent cation free (relaxed). The relaxed dodecamer readily dissociates into monomers upon exposure to 1 M urea or pH 8.0. Glutamine synthetase can be inactivated irreversibly by oxidizing a particular histidine residue or by incubating with methionine sulfoximine and ATP. In order to establish hybridoma monoclones that produce antibodies capable of differentiating between different conformers of glutamine synthetase, homogeneous antibodies produced from 7 clones (10-76-1, 48-76-1, 68-2-1, 57-142-2, 72-104-1, 68-3-2, 57-8-1) were characterized for their binding specificity and effects on glutamine synthetase activity. Two antibodies (10-76-1, 48-76-1) bind only to the monomeric form, two antibodies (57-142-2, 68-3-2) bind only to the dodecameric forms (taut or relaxed) and the three others (68-2-1, 72-104-1, 57-8-1) bind to both forms. At a low antibody concentration, 68-3-2 binds preferentially to taut glutamine synthetase over oxidized glutamine synthetase. None of the 7 antibodies differentiates between unadenylylated and adenylylated form. Nevertheless, the gamma-glutamyltransferase activities of the resulting antibody-glutamine synthetase complexes were influenced variably depending upon the state of adenylylation and the divalent cation.

Antibodies, Monoclonal↗
PubMed1984

Separation of glutamine synthetase species with different states of adenylylation by chromatography on monoclonal anti-AMP antibody affinity columns.

Glutamine synthetase [GS; L-glutamate:ammonia ligase (ADP-forming), EC 6.3.1.2] from Escherichia coli is composed of 12 identical subunits arranged in two superimposed hexagonal arrays. Therefore, partially adenylylated GS is a mixture of hybrid molecules containing different numbers (from 0 to 12) and distributions of adenylylated subunits. In an effort to separate these GS species into uniquely adenylylated molecular species, immunoadsorbants were prepared by covalent attachment of monoclonal antibodies, 72-76-1 (IgG2a and 37-2-1 (IgM), to Affi-Gel 10. The bound GS was eluted with AMP gradients. The results indicate that the IgG column and IgM column yield significantly different elution profiles; the column prepared with the IgG monoclonal antibody better resolves GS containing fewer than 3 adenylylated subunits per dodecamer, whereas the column prepared from the IgM monoclonal antibody better resolves the GS containing higher numbers (from 4 to 12) of adenylylated subunits. In addition, the results indicate that both the distribution and the number of adenylylated subunits are important factors in this separation.

Adenosine Monophosphate↗
PubMed1981

[Electrophoretic study on the changes of serum protein fractions in Korean women--the effects of age, oral contraceptive, and intrauterine contraceptive device (author's transl)].

The serum levels of total protein, albumin, and electrophoretic fractions from 610 Korean women, 21-50 years, were measured to determine their relation to age, and the effects of oral contraceptives (OCs) (Norinyl), and Lippes Loop IUD. In normal women, total protein and albumin concentrations significantly decreased with age. Alpha2 and gamma globulin concentrations were decreased after the age of 40, but the statistical significance was low. Significant decreases in total protein and albumin concentrations were observed in OC and IUD users, and rapid decrease in total protein was observed in OC users rather than in IUD users. Beta globulin was slightly increased in both groups, and gamma globulin was decreased in OC users. No significant changes in alpha1 and alpha2 globulin concentrations were noted in either group.

Age Factors↗