Biomedical subjects

C H Choi

Publications and source records attributed to C H Choi.

At least 37 records · Page 2Linked to original sources

PubMed2001

Reconstruction by biceps tendon rerouting for posterolateral rotatory instability of the knee: Modification of the Clancy technique.

We present a biceps rerouting technique for posterolateral rotatory instability using a modification of the biceps femoris tendon tenodesis of Clancy. The distinguishing features of this technique are the approach to the lateral femoral epicondyle through the interval between the iliotibial band and biceps femoris muscle, and fixation of the transferred biceps tendon at the isometric point. Reconstruction for posterolateral rotatory instability by modified biceps tendon rerouting can result in objectively and functionally acceptable knee function.

Bone Wires↗

PubMed2001

Functional properties of human nicotinic AChRs expressed by IMR-32 neuroblastoma cells resemble those of alpha3beta4 AChRs expressed in permanently transfected HEK cells.

We characterized the functional and molecular properties of nicotinic acetylcholine receptors (AChRs) expressed by IMR-32, a human neuroblastoma cell line, and compared them to human alpha3 AChRs expressed in stably transfected human embryonic kidney (HEK) cells. IMR-32 cells, like neurons of autonomic ganglia, have been shown to express alpha3, alpha5, alpha7, beta2, and beta4 AChR subunits. From these subunits, several types of alpha3 AChRs as well as homomeric alpha7 AChRs could be formed. However, as we show, the properties of functional AChRs in these cells overwhelmingly reflect alpha3beta4 AChRs. alpha7 AChR function was not detected, yet we estimate that there are 70% as many surface alpha7 AChRs in IMR-32 when compared with alpha3 AChRs. Agonist potencies (EC(50) values) followed the rank order of 1,1-dimethyl-4-phenylpiperazinium (DMPP; 16+/-1 microM) > nicotine (Nic; 48 +/- 7 microM) > or = cytisine (Cyt; 57 +/- 3 microM) = acetylcholine (ACh; 59 +/- 6 microM). All agonists exhibited efficacies of at least 80% relative to ACh. The currents showed strong inward rectification and desensitized at a rate of 3 s(-1) (300 microM ACh; -60 mV). Assays that used mAbs confirmed the predominance of alpha3- and beta4-containing AChRs in IMR-32 cells. Although 18% of total alpha3 AChRs contained beta2 subunits, no beta2 subunit was detected on the cell surface. Chronic Nic incubation increased the amount of total, but not surface alpha3beta2 AChRs in IMR-32 cells. Nic incubation and reduced culture temperature increased total and surface AChRs in alpha3beta2 transfected HEK cells. Characterization of various alpha3 AChRs expressed in HEK cell lines revealed that the functional properties of the alpha3beta4 cell line best matched those found for IMR-32 cells. The rank order of agonist potencies (EC(50) values) for this line was DMPP (14 +/- 1 microM) = Cyt (18 +/- 1 microM) > Nic (56 +/- 15 microM > ACh (79 +/- 8 microM). The efficacies of both Cyt and DMPP were approximately 80% when compared with ACh and the desensitization rate was 2 s(-1). These data show that even with the potential to express several human nicotinic AChR subtypes, the functional properties of AChRs expressed by IMR-32 are completely attributable to alpha3beta4 AChRs.

Acetylcholine↗

PubMed2001

Squamous cell carcinoma of the cornea.

In this paper, a case of corneal squamous cell carcinoma is reported. Invasive squamous cell carcinoma of the cornea is a rare disorder and has not been previously described in the Korean literature. In this case, the invasive squamous cell carcinoma of the cornea was treated by complete excision and cryotherapy. No evidence of metastasis or recurrence has been found since the procedure. Complete excision and adjunctive cryotherapy has become the treatment of choice because of the higher recurrence rate following a simple excision.

Aged↗

PubMed2000

Reactive oxygen species-specific mechanisms of drug resistance in paraquat-resistant acute myelogenous leukemia sublines.

Reactive oxygen species (ROS)-specific mechanisms of drug resistance were explored in paraquat (PQ)-resistant acute myelogenous leukemia cell (OCI/AML-2) sublines. For this, PQ-resistant AML sublines, AML-2/PQ100 and AML-2/PQ400, were selected in the presence of PQ concentrations of 100 microg/ml and 400 microg/ml, respectively. They showed a moderate level of cross resistance to cisplatin and doxorubicin. They were also slightly more resistant than the parental cell (AML-2/WT) to etoposide, camptothecin and daunorubicin. The resistance of PQ-resistant AML-2 sublines to cisplatin seemed to be due to increased amounts of metallothionein, which was not only supported by reversal of resistance to cisplatin by propargylglycin (an inhibitor of metallothionein synthesis) but also confirmed by Western blot analysis and reverse transcription-PCR assay. In addition, both AML-PQ100 and /PQ400 sublines showed increased activities of Cu-, Zn-containing superoxide dismutase (Cu,Zn-SOD) and Mn-containing superoxide dismutase (Mn-SOD), whereas AML-2/PQ400, but not AML-2/PQ100, showed increased glutathione S-transferase activity as compared to that of AML-2/WT. However, there was no difference in other ROS-related cellular antioxidants between AML-2/WT and its PQ-resistant sublines. Taken together, these results strongly suggest that increases in levels of metallothionein, glutathione S-transferase, Cu,Zn-SOD and Mn-SOD play important roles in protective mechanisms against toxicity of PQ or ROS in AML cells.

Alkynes↗

PubMed2000

Posterior tibial neuropathy by a Baker's cyst: case report.

Baker's cysts are rare cause of peripheral nerve entrapment and only a few cases of tibial nerve entrapment resulting from the popliteal cyst in the calf muscle have been reported in the literature. We present a case of rheumatoid arthritis complicated by a Baker's cyst with a tibial nerve entrapment. It is important to diagnose a Baker's cyst early and to differentiate it from thrombophlebitis, a popliteal aneurysm, tumor or muscle tear to effect optimal therapy and to obviate a potential neuropathy. Prompt recognition of these cases may save the patients unnecessary procedures and delay in treatment.

Arthritis, Rheumatoid↗

PubMed1999

Drug concentration-dependent expression of multidrug resistance-associated protein and P-glycoprotein in the doxorubicin-resistant acute myelogenous leukemia sublines.

The multidrug resistance of cancer cells can be mediated by an overexpression of the human MDR1 and MRP genes, which encode the transmembrane efflux pumps, the 170 kDa P-glycoprotein (Pgp) and the 190 kDa multidrug resistance-associated protein (MRP), respectively. In this study, we investigate which protein is preferentially overexpressed in the function of doxorubicin concentrations in the acute myelogenous leukemia cell line (OCI/AML-2). Multidrug-resistant AML-2 sublines were isolated in doxorubicin concentrations of 20, 100, 250, and 500 ng/ml. MRP was at first expressed at low concentrations of less than 5 x IC50 (100 ng/ml) of doxorubicin followed by the overexpression of Pgp with concentrations of more than 12.5 x IC50 (250 ng/ml) of doxorubicin. In addition, it appeared that increased amounts of MRP and its mRNA in AML-2/DX20 and /DX100 decreased gradually in both AML-2/DX250 and /DX500 overexpressing Pgp. In conclusion, it is thought that the overexpression of MRP or Pgp is dependent upon drug concentrations. It could be implicated that the overexpression of MRP might be negatively related to that of Pgp.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1999

Effect of DW2282 on the induction of methemoglobinemia, hypoglycemia or WBC count and hematological changes.

DW2282,(S)-(+)-4-phenyl-1-[1-(4-aminobenzoyl)-indoline-5-sulfonyl] -4,5-dihydro-2-imidazolone hydrochloride, is a new anticancer agent which is thought to exhibit a characteristic mechanism of action in the inhibition of tumor growth. In this study, we estimated the toxicities of DW2282 in mice. When mice were orally dosed for five consecutive days at the dosages of 50, 100 and 150 mg/kg, DW2282 did not induce methemoglobinemia and hypoglycemia at any of these doses. However, increased ALT and AST values were observed in the 150 mg/kg dosing group, and white blood cells (WBC) were significantly decreased at all doses. However, the changes in WBC count, ALT and AST immediately reversed after the cessation of drug administration. In addition, we found that DW2282 did not cause an increase in hemolysis in human blood. Taken together, these data suggested that DW2282 may have a relatively low level of toxicity, and that there may be a quick recovery from any toxicity it does produce.

Alanine Transaminase↗

PubMed1999

Troponin-I, myoglobin, and mass concentration of creatine kinase-MB in acute myocardial infarction.

Myoglobin, creatine kinase-MB (CKMB) mass concentration and troponin-I are newer biochemical markers for the diagnosis of acute myocardial infarction (AMI). We conducted a prospective study to formulate a model for the collective interpretation of these three markers in the diagnosis of AMI. Eighty-seven patients with AMI had serial serum samples taken to establish the time-frame sensitivity of individual markers. None of the markers had a good sensitivity within the first 4 h of infarction. Myoglobin and CKMB (mass) had sensitivities of 92.3% and 96.2%, respectively, at 4-8 h post infarct. CKMB (mass) and troponin-I had sensitivities >92% at 8-24 h. Troponin-I maintained sensitivity >93% until 72 h. A guideline was formulated based on the results. Our data suggest that troponin-I, myoglobin and CKMB (mass) yield satisfactory diagnostic sensitivity when used with reference to specific time frames. The combined use of these markers can provide valuable information for clinicians in managing AMI patients.

Adult↗

PubMed1999

One-week ranitidine bismuth citrate versus colloidal bismuth subcitrate-based anti-Helicobacter triple therapy: a prospective randomized controlled trial.

OBJECTIVE: The efficacy of 1 wk bismuth triple therapy is adversely influenced by the presence of metronidazole resistance. In vitro studies suggest that ranitidine bismuth citrate (RBC) plus metronidazole exhibit synergistic activity against metronidazole resistant strains of Helicobacter pylori (H. pylori). Whether this confers a superior clinical efficacy remains unproven. This study compared the efficacy of RBC-based triple therapy with bismuth triple therapy in eradication of H. pylori. METHODS: Patients with H. pylori-related ulcer disease or gastritis were randomized to receive either 400/mg of RBC twice daily plus 400/mg of metronidazole and 500/mg of tetracycline four times daily for 1 wk (RMT) or 120/mg of colloidal bismuth subcitrate, 400/mg of metronidazole, and 500/mg of tetracycline, all given four times daily for 1 wk (BMT). Metronidazole susceptibility was determined by the E-test and pretreatment resistance was defined as minimum inhibitory concentration > or = 32/mg/L. RESULTS: Of 100 consecutive patients randomized, two patients were lost to follow-up in each group. Forty-three of 85 (51%) H. pylori isolates were metronidazole resistant. Per-protocol cure rate for RMT and BMT was 40 of 41 (98%) and 37 of 44 (84%), respectively (p = 0.058). Intent-to-treat cure rate for RMT and BMT was 46 of 50 and 41 of 50, respectively (92% vs 82%, p = 0.23). A significantly higher eradication of metronidazole resistant H. pylori was observed in the RMT group (25 of 25, 100%) than in the BMT group (12 of 16, 75%), (p = 0.018). Side effects observed in the two treatment groups were comparable. CONCLUSIONS: One week of RBC triple therapy with metronidazole and tetracycline is an effective anti-Helicobacter therapy. This regimen is more appropriate in areas of high prevalence of metronidazole resistance.

Adolescent↗

PubMed1998

Immunomodulating activity of DW-116, a new quinolone antibiotic.

DW-116, (1-(5-fluoro-2-pyridyl)-6-fluoro-7-(4-methyl-1-piperazinyl)-1, 4-dihydro-4-oxoquinoline-3-carboxylic acid hydrochloride), is a new quinolone antibiotic with a broad antibacterial spectrum against G(+) and G(-) bacteria. DW-116 was evaluated for the immunomodulating activities, which is one of the efforts to investigate the mechanism of action related to the good in vivo antibacterial efficacy. The results of in vitro studies revealed there was no statistically significant increase in B and T lymphocyte proliferation. But the results of in vivo studies showed that the number of plaque forming cells (PFC), the amount of polyclonal antibodies and delayed-type hypersensitivity (DTH) were significantly increased after the repeat administration with 12 and 60 mg/kg of DW-116. Taken together, these results proposed that immunostimulating effect of DW-116 could be one of the action mechanisms for demonstrating in vivo antibacterial activities under these experimental conditions.

Adjuvants, Immunologic↗

PubMed1998

Influence of endothelin-1 on clonidine-induced cardiovascular effects in anesthetized rabbits.

This study was designed to investigate the effect of endothelin-1 (ET-1) on clonidine-induced cardiovascular effects in urethane-anesthetized rabbits and to clarify the mechanism of its action. Clonidine (5, 10, and 20 micrograms/kg) given into a femoral vein (i.v.) produced a marked dose-dependent fall in arterial blood pressure and heart rate, but intracerebroventricular (i.c.v.) clonidine (2, 4, and 8 micrograms/kg) induced a slight depressor effect and bradycardia. Intravenous clonidine-induced hypotension was significantly enhanced by pretreatment with ET-1 or sarafotoxin, but the bradycardia was not affected. Intracerebroventricular clonidine-induced depressor responses were greatly inhibited by sarafotoxin pretreatment but not by ET-1. Both i.v. and i.c.v. ET-1 and sarafotoxin elicited marked hypotensive responses, with a slight decrease in heart rate. The depressor action evoked by i.v. ET-1 and sarafotoxin was significantly inhibited by nitroprusside but not by phentolamine or sodium acetylsalicylate. Furthermore, the weak bradycardia induced by ET-1 or sarafotoxin was not influenced by pretreatment with phentolamine, nitroprusside, or sodium acetylsalicylate. Taken together, these experimental data suggest that ET-1 potentiates clonidine-induced hypotensive responses in the urethane-anesthetized rabbit through facilitation of nitric oxide release, which appears to be associated with endothelin receptors.

Adrenergic alpha-Agonists↗

PubMed1998

Toxicities of 166Holmium-chitosan in mice.

166Holmium (166Ho) is a radionuclide of rare earth chemical and is known to have antitumor activity. Several chemicals were complexed with 166Ho to facilitate the transport of this radionuclide to the site of action. In this study, 166Ho was complexed to chitosan (Chit) which decreases the distribution of Ho into other tissues when applied intrahepatically. To investigate the single dose toxicity, mice were administered intravenously with 1 mCi/kg body weight of 166Ho-Chit (DW-166HC), Chit or nothing. Organ weights, hematological and histopathological studies were performed in 6 animals per group at 1, 3 and 14 days after administration. In 166Ho-Chit treated animals, a slight decrease of erythrocyte number was observed at day 14 and increases of relative liver and lung weights were found at day 3. Although marked multiple necrotic foci in the white pulp and depletion of marginal zone in the spleen were noted at day 1, these findings were decreased in severity and fully recovered at day 3 and day 14, respectively. Slightly decreased kidney weights were observed both in Chit and in 166Ho-Chit treated groups without histological alterations. Thus it is suggested that most effects of 166Ho-Chit observed at an early stage after administration are limited to rapidly dividing cells and reversible within 14 days.

Animals↗

PubMed1997

Guanine-nucleotide binding and hydrolyzing kinetics of ORrab2, a rice small GTP-binding protein expressed in Escherichia coli.

The ORrab2 gene encodes a GTP-binding protein of 23.169 kDa. The deduced amino acid sequence shows that ORrab2 has the motifs conserved among small GTP-binding proteins in plants and that it shares sequence identity with Atrab2 (93.0%), Hrab2 (85.2%), Hrab4 (51.9%), Hrab1 (46.2%), YPT (40.7%), Hrab3B (40.0%), Hrab3A (38.1%), SEC4 (38.1%), Hrab5 (34.3%) and Hrab6 (32.4%). To analyze the biochemical properties of this protein, an ORrab2 cDNA was overexpressed in Escherichia coli and the protein purified by Ni2+-nitrilotriacetic acid agarose and hydroxyapatite column chromatography. The molecular mass of the protein bearing a His-tag is approximately 28.2 kDa. The guanine-nucleotide binding and hydrolyzing activity of ORrab2 increased with non-ionic C12E10 (polyoxyethylene 10-lauryl ether) and ionic Chaps detergent treatment. ORrab2 bound maximally 1.03 mol of [gamma-35S]GTP[S]/mol of protein with a Kd value of 56.83 nM. The ratios k(off GDP)/k(off GTP) of ORrab2 were 3.63 for the control, 3.7 in the presence of C12E10, and 3.83 with Chaps, indicating that ORrab2 has a higher affinity for GTP than GDP. The rate (k(cat)) of Pi release against [gamma-32P]GTP bound ORrab2 in a steady state and the rate of hydrolysis of [gamma-32P]GTP (kGTPase) were calculated to be 432 x 10(-4) +/- 8 x 10(-4) min(-1) and 172 x 10(-4) +/- 2 x 10(-4) min(-1), respectively, in the presence of 0.1% C12E10 and 1 mM MgSO4.

Amino Acid Sequence↗

PubMed1997

Biochemical characteristics of a rice (Oryza sativa L., IR36) G-protein alpha-subunit expressed in Escherichia coli.

A cDNA encoding the alpha-subunit of the heterotrimeric G-protein in rice (RGA1) was overexpressed in Escherichia coli and then isolated by Ni2+-nitrilotriacetic acid affinity chromatography. The molecular mass of RGA1 bearing a His tag was approx. 49 kDa. Immunoblot analysis using anti-RGA1 revealed that the RGA1 protein is most abundant in seedling leaves and least abundant in mature roots. It exists at particularly high levels in the immature embryo after pellicle extrusion. In addition, the RGA1 antiserum exhibited a difference in binding affinity for Galpha proteins from monocots (maize and rice) and dicots (Arabidopsis, pea, soya bean and tomato); whereas it cross-reacted with Galpha proteins of monocots, it did not with those of dicot plants. When bound to guanosine 5'-(gamma-thio)triphosphate (GTP[S]), the RGA1 protein was partially protected from tryptic proteolysis. In the presence of GTP[S], trypsin cleaved the RGA1 protein into four fragments 24, 14, 11 and 5 kDa in size. When RGA1 was bound to GDP, only the 5 kDa polypeptide was seen on SDS/PAGE after trypsin digestion. Photoaffinity labelling with [alpha-32P]GTP and a GTP[S]-binding assay revealed that RGA1 incorporated 32P and showed specific binding to a guanine nucleotide. Guanidine binding of RGA1 was affected by the concentration of MgCl2 (maximum at 2 mM). The rate of guanine nucleotide binding of RGA1 (kon,GTP[S]=0.0141+/-0.0014 min-1) and, at steady state, the kcat value for GTP hydrolysis (0.0075+/-0.0001 min-1) were very low even at 2 mM MgCl2. The binding affinity for the nucleotides examined was in the order GTP-S- >/= GTP > GDP > CTP > ATP >/= dTTP.

Affinity Labels↗

PubMed1997

Isolation and characterization of daunorubicin-resistant AML-2 sublines.

An attempt was made to isolate resistant sublines of acute myelogenous leukemia (OCI/ AML-2) cells by chronic exposure to gradually increasing concentrations of daunorubicin in order to determine the mechanism of its resistance to this drug. Four daunorubicin-resistant sublines, AML-2/D100, /D250, /D500, and /D1,000 were isolated. The values of relative resistance of each daunorubicin-resistant AML subline were about 3, 6, 18, and 23-fold, respectively, as compared to the AML-2 line with an IC50 of 5 nM. The daunorubicin-resistant AML-2 sublines also showed cross resistance to various anticancer drugs including another anthracycline doxorubicin, a Vinca alkaloid vincristine, and an epipodophyllotoxin etoposide. A functional assay using flow cytometry showed decreased accumulation of daunorubicin in these sublines as compared to that of AML-2, which was reversed by cyclosporin A or cyanide. The development of the ATP-dependent multidrug resistant phenotype was due to low to high levels of expression of P-glycoprotein (PGP). The major mechanisms of increased PGP appears to be associated with gene amplification. In addition, other mechanisms such as increased stability of protein or mRNA might be involved depending on the concentration of daunorubicin used for selection. However, a multidrug resistance-associated protein (MRP) was not involved in these resistant sublines. These daunorubicin-resistant AML-2 sublines could provide a useful model for the study of multidrug resistance mediated by PGP.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

A novel energy dependent mechanism reducing daunorubicin accumulation in acute myeloid leukemia.

Using cyclosporin A (CsA) to inhibit P-glycoprotein (P-gp) function we showed previously that there was a discordance between the ability of acute myeloid leukemic (AML) blast cells to accumulate daunorubicin and P-gp antigen expression (Xie et al, Leukemia 1995; 9:1882-1887). This discordance suggests that a CsA-sensitive drug efflux mechanism distinct from P-gp is expressed in many clinical samples. In the present study using the ATP depleting agents cyanide, azide, or dinitrophenol to inhibit energy dependent transport processes, we observed even larger increases in daunorubicin accumulation than were seen with CsA. Similar patterns were seen in a wide range of P-gp negative human cancer cell lines. Also the observed cyanide effect did not correlate with the expression of mRNA for multidrug resistance-associated protein (MRP), the only other member of the ABC family of membrane transporters that is known to be capable of effluxing daunorubicin. Thse results suggest that daunorubicin accumulation in many cases of AML is modulated by one or more novel energy-dependent processes that are distinct from P-gp or MRP. We speculate that this novel drug transport mechanism(s) may influence the response of AML patients to daunorubicin and other therapeutic agents.

ATP Binding Cassette Transporter, Subfamily B, Mem↗

PubMed1997

Prevention of heterotopic bone formation after total hip arthroplasty using 600 rad in single dose in high risk patient.

Nineteen patients received single-dose exposure to 600 rad delivered within 48 hours of total hip arthroplasty (THA) with shielding of the prosthesis region for the prevention of heterotopic ossification. The patients were considered at high risk for developing heterotopic ossification (HO) because of hypertropic osteoarthritis, post-traumatic osteoarthritis or the presence of previously-formed ectopic bone. The average follow-up period was 42 months (range, 37 months-48 months). At a follow-up study, all hips except one were classified as Brooker class 0. The single exception was classified as class I. All patients were asymptomatic at the last follow-up study and no component demonstrated subsidence or radiolucent line indicative of loosening. The authors concluded that 600 rad, single-fraction radiation therapy is cost effective, convenient and safe for the prevention of heterotopic ossification after total hip arthroplasty.

Adult↗

PubMed1997

Influence of pentobarbital-Na on stimulation-evoked catecholamine secretion in the perfused rat adrenal gland.

OBJECTIVES: The present study was attempted to investigate the effects of pentobarbital-Na, one of the barbiturates which are known to depress excitatory synaptic transmission in the central nervous system at concentrations similar to those required for the induction and maintenance of anesthesia, on catecholamines (CA) secretion evoked by cholinergic stimulation and membrane-depolarization from the isolated perfused rat adrenal gland, and to clarify the mechanism of its action. METHODS: Mature male Sprague-Dawley rats were anesthetized with thiopenal-Na (40 mg/kg, s.c.). The adrenal gland was isolated by the methods of Wakade. A cannula used for perfusion of the adrenal gland was inserted into the distal end of the renal vein. The adrenal gland was carefully removed from the animal and placed on a platform of a leucite chamber. RESULTS: The perfusion of pentobarbital-Na(30-300 uM) into an adrenal vein for 20 min produced relatively dose-dependent inhibition in CA secretion evoked by ACh(5.32 mM), DMPP(100 uM for 1 min), McN-A-343(200 uM for 2 min), Bay-K-8644(10 uM) and high potassium(56 mM), while it did not affect the CA secretion of cyclopiazonic acid(10 uM). Also, in the presence of thiopental-Na (100 uM), CA secretory responses evoked by ACh, DMPP, McN-A-343 and high K+ were markedly depressed. Moreover, in adrenal glands preloaded with ketamine(100 uM for 20 min), which is known to be a dissociative anesthetic, CA secretion evoked by ACh, DMPP, McN-A-343 and high K+ were significantly attenuated. CONCLUSION: Taken together, these experimental results suggest that pentobarbital-Na depresses CA release evoked by both cholinergic stimulation and membrane-depolarization from the isolated rat adrenal medulla and that this inhibitory activity may be due to the result of the direct inhibition of Ca++ influx into the chromaffin cells without any effect on the calcium mobilization from the intracellular store.

Acetylcholine↗