Nasopharyngectomy for recurrent high-grade mucoepidermoid carcinoma after radiation failure.
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Carcinoma, Mucoepidermoid↗
Biomedical subjects
E C Choi
Publications and source records attributed to E C Choi.
Feminist ethics in women's health.
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Cultural Diversity↗
Distribution of bacteria with the arylsulfate sulfotransferase activity.
This study is to predict the possible roles of the arylsulfate sulfotransferase (ASST) in the microorganism. At first we studied the spectrum of a distribution of the ASST enzyme through about 1,300 bacteria and the several selected strains were compared with Klebsiella K-36 previously reported in the level of DNA homology using the Southern blot method. From this study, we could predict that this enzyme would not exist in specific bacteria and it might not be a critical enzyme for the life of bacteria.
Arylsulfotransferase↗
Purification and characterization of Cop, a protein involved in the copy number control of plasmid pE194.
Cop protein has been overexpressed in Escherichia coli using a T7 RNA polymerase system. Purification to apparent homogeneity was achieved by the sequential chromatography on ion exchange, affinity chromatography, and reverse phase high performance liquid chromatography system. The molecular weight of the purified Cop was estimated as 6.1 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). But the molecular mass of the native state Cop was shown to be 19 kDa by an analytical high performance size exclusion chromatography, suggesting a trimer-like structure in 50 mM Tris-HCl buffer (pH 7.5) containing 100 mM NaCl. Cop protein was calculated to contain 39.1% alpha-helix, 16.8% beta-sheet, 17.4% turn, and 26.8% random structure. The DNA binding property of Cop protein expressed in E. coli was preserved during the expression and purification process. The isoelectric point of Cop was determined to be 9.0. The results of amino acid composition analysis and N-terminal amino acid sequencing of Cop showed that it has the same amino acid composition and N-terminal amino acid sequence as those deduced from its DNA sequence analysis, except for the partial removal of N-terminal methionine residue by methionyl-aminopeptidase in E. coli.
Amino Acid Sequence↗
Resistance mechanism of Acinetobacter spp. strains resistant to DW-116, a new quinolone.
DW-116 is a new fluoroquinolone antimicrobial agent with a broad spectrum. In order to elucidate the resistance mechanism to DW-116 in Acinetobacter spp. bacteria, total chromosomal DNA was isolated from 10 strains of Acinetobacter spp. resistant to DW-116. Quinolone resistance determinant region (QRDR) of DNA gyrase gene was amplified by PCR. The 345 bp nucleotide fragment yielded was inserted into pKF 3 which was used as the vector. Comparisons of the DNA sequences of 8 strains with that of the wild type strain revealed a Ser-83 to Leu mutation in mutants and all ten strains contained one silent mutation(T-->G) in QRDR. From Acinetobacter MB4-8 strain, DNA gyrase was isolated and purified, through no-vobiocin-sepharose, heparin-sepharose affinity column chromatography. The enzyme was composed of two subunits and the molecular mass of subunits A and B were 75.6 and 51.9 kDa, respectively. The supercoiling activity of the reconstituted DNA gyrase composed of subunit A from Acinetobacter MB4-8 and subunit B from E. coli was not inhibited by 128 micrograms/ml of ciprofloxacin. It might be said that one of the resistance mechanisms to DW-116 in A-cinetobacter MB4-8 was subunit A alteration of DNA gyrase.
Acinetobacter↗
Physicochemical properties of recombinant hepatitis B surface antigen expressed in mammalian cell (C127).
The physicochemical properties of recombinant hepatitis B surface antigen (r-HBsAg), which was expressed in C127 mammalian cell were studied. Using roller bottle culture in DMEM supplemented with fetal bovine serum, 10-15 mg/L of r-HBsAg was produced with about 31% of purification yield. The purity of r-HBsAg by HPLC was 99.8% and electron microscopic examination showed homogeneous spherical particle with 22 nm in diameter, a morphological characteristic of HBsAg. The density of r-HBsAg by CsCl density gradient method was 1.19 g/ml and the isoelectric point by Mono P HR 5/20 column was 4.6. The analysis of subunit protein pattern using SDS-PAGE followed by scanning densitometry gave 81.3% of S protein and 18.7% of pre-S protein. Fluorophore-assisted-carbohydrate-electrophoresis analysis showed the relative amount of carbohydrate to protein was 1.7% and its major component was N-acetyl glucosamine, which was about 39% of total carbohydrate. The relative amount of lipid to protein determined by vanillin phosphoric acid method was 32.5% and its major component was phospholipid, which was about 70% of total lipid. The physicochemical properties of C127 mammalian cell-derived r-HBsAg are similar to those of p-HBsAg, suggesting that the r-HBsAg can be used in developing a new preventive vaccine against hepatitis B.
Animals↗
Immunological properties of recombinant hepatitis B surface antigen expressed in mammalian cell (C127).
We examined the immunological properties of the recombinant hepatitis B surface antigen (r-HBsAg) which was expressed in mammalian cell (C127). The cross-immunity of r-HBsAg and plasma-derived hepatitis B surface antigen (p-HBsAg) were tested using Western blotting and ELISA with guinea pig polyclonal antibody and naturally infected human-derived antibody and the both antigens show the same results in their response pattern and intensity, which indicate they have a good cross-immunity. From the measurement of ED50 after formalin- or heat-inactivation, both r-HBsAg and p-HBsAg showed ED50 of 0.2-0.3 in formalin-inactivation, while r-HBsAg was 0.05-0.09 and p-HBsAg was 0.03-0.07 in heat-inactivation, which means heat-inactivation method is 3-4 times superior in immunogenicity. In the immunopersistency test performed in guinea pig for the period of 3 months with two different adjuvants, antibody titer was 34.2 with muramyl dipeptide adjuvant, which was 1.8 times greater than the antibody titer of 18.9 with AlPO4 adjuvant. The mutagenicity of r-HBsAg, examined by Ames test and micronucleus test, were all negative. In conclusion, r-HBsAg has the same cross-immunity with p-HBsAg, and heat-inactivation method and muramyl dipeptide adjuvant allow development of r-HBsAg vaccine with excellent immunogenicity.
Adjuvants, Immunologic↗
Inhibitory effects of Bifidobacterium spp. isolated from a healthy Korean on harmful enzymes of human intestinal microflora.
Five hundreds of bifidobacteria were isolated from a healthy Korean and the inhibitory effects of these isolated bacteria on harmful enzymes of human intestinal microflora were examined by cocultivation of the isolated bifidobacteria with E. coli or total human intestinal microflora. In comparison with the results of E. coli or intestinal microflora cultivation, Bifidobacterium breve K-110, B. breve K-111 and B. infantis K-525 effectively inhibited harmful enzymes (beta-glucuronidase and tryptophanase) of E. coli and lowered the pH of the culture media. Also they inhibited the harmful enzymes (beta-glucosidase, beta-glucuronidase, tryptophanase and urease) and ammonia production of intestinal microflora, and lowered pH of the culture media by increasing lactic acid bacteria of intestinal microflora. When these isolated bifidobacteria were administered on mice, fecal harmful enzymes were also inhibited. Among tested bifidobacteria, B. breve K-110 had the highest inhibitory effect of fecal harmful enzymes.
Animals↗
Resistance to macrolide-lincosamide-streptogramin B antibiotics is induced by 16 membered-ring macrolide antibiotics in Enterococcus faecalis 373.
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Anti-Bacterial Agents↗
In-vitro and in-vivo antibacterial activity of CFC-222, a new fluoroquinolone.
CFC-222 is a novel fluoroquinolone with potent and broad-spectrum antibacterial activity. The in-vitro and in-vivo activities of CFC-222 were compared with those of ciprofloxacin, ofloxacin, lomefloxacin and sparfloxacin. Against gram-positive bacteria such as Staphylococcus aureus (quinolone-susceptible and quinolone-resistant), Staphylococcus epidermidis, Streptococcus pneumoniae and Enterococcus faecalis, CFC-222 was more active than ciprofloxacin and similar to sparfloxacin. Against gram-negative bacteria, including Enterobacteriaceae, the in-vitro activity of CFC-222 was similar to that of sparfloxacin, but less than that of ciprofloxacin. However, it was less active than ciprofloxacin and sparfloxacin against Pseudomonas aeruginosa. In mouse systemic infection caused by S. aureus Smith or S. aureus TMS 33, CFC-222 demonstrated an activity similar to that of ciprofloxacin and sparfloxacin, but better than that of ofloxacin. The compound was more effective than ciprofloxacin and sparfloxacin in murine infection caused by Streptococcus pyogenes ATCC 8668. Against Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae infections, the efficacy of CFC-222 was similar to those of ciprofloxacin, ofloxacin and sparfloxacin. The activity of CFC-222 was similar to those of ciprofloxacin and sparfloxacin against P. aeruginosa MB4-16 in the same infection model. These results suggest that CFC-222 may be a promising therapeutic agent for the treatment of various bacterial infections.
Animals↗
Susceptibility of penicillin-susceptible and -resistant pneumococci to CFC-222, a new fluoroquinolone.
The in-vitro activity of 12 antibacterial agents against 98 clinical isolates of Streptococcus pneumoniae, including 54 penicillin-resistant strains, was determined by a standardized broth microdilution method. CFC-222, vancomycin and imipenem were the most active agents, with an MIC90 of 0.5 mg/L for the test strains. CFC-222 was 16-fold more potent than ciprofloxacin and ofloxacin against all strains tested, including both penicillin-susceptible and -resistant strains. The anti-pneumococcal activity of fluoroquinolones was not affected by penicillin susceptibility. These results indicate that CFC-222 is potentially useful for treating infection caused by penicillin-resistant strains of S. pneumoniae.
Anti-Infective Agents↗
Induction of ermAMR from a clinical strain of Enterococcus faecalis by 16-membered-ring macrolide antibiotics.
We cloned the MLSB resistance determinant by PCR from a clinical isolate of Enterococcus faecalis 373, which is induced more strongly by a 16-membered-ring macrolide, tylosin, than by erythromycin. To elucidate the molecular basis of resistance of E. faecalis 373, we analyzed the cloned gene, designated ermAMR, by site-directed mutagenesis and reporter gene assay. Our results showed that an arginine-to-cysteine change in the seventh codon of the putative leader peptide endowed tylosin with resistance inducibility and that TAAA duplication enabled the control region to express the downstream methylase gene at a drastically increased level.
Amino Acid Sequence↗
Overexpression of arylsulfate sulfotransferase as fusion protein with glutathione S-transferase.
A procedure has been developed for the overexpression and purification of milligram quantities of the Klebsiella K-36 arylsulfate sulfotransferase (ASST). The structural gene was amplified by means of a polymerase chain reaction (PCR) technique and inserted into the plasmid vector pGEX-3X. The plasmid pGEX-100, carrying the Klebsiella K-36 astA structural gene under the control of the Escherichia coli tac promoter, was transformed into the E. coli strain BL21 (DE3). The ASST was produced in E. coli as a fusion with glutathione S-transferase. Conditions for protein production, isolation on glutathione Sepharose 4B, and Xa cleavage to generate active ASST were developed. The purification yielded approximately 0.7 mg of pure enzyme per liter of bacterial culture. Kinetic analysis of the overexpressed enzyme indicated that it had kinetic properties almost the same as those of the enzyme purified from Klebsiella K-36 cells. The purification procedure was very rapid and is suitable for obtaining considerable amounts of enzyme at a relatively high yield compared with its purifying method from the culture of the Klebsiella K-36 strain.
Amino Acid Sequence↗
In-vitro and in-vivo activities of DW-116, a new fluoroquinolone.
DW-116 is a novel fluoroquinolone that was two- to four-fold more active than rufloxacin and less active than sparfloxacin, ciprofloxacin and ofloxacin against Gram-positive bacteria in vitro. Against Gram-positive and Gram-negative bacteria, the in-vivo activity of DW-116 was similar or slightly greater than that of rufloxacin and less than that of sparfloxacin, ciprofloxacin and ofloxacin. ED50 (50% effective dose) values for DW-116 did not correlate with in-vitro MICs.
Animals↗
In vitro and in vivo antibacterial efficacies of CFC-222, a new fluoroquinolone.
CFC-222 is a novel fluoroquinolone containing a C-7 bicyclic amine moiety with potent antibacterial activities against gram-positive, gram-negative, and anaerobic organisms. We compared the in vitro and in vivo activities of CFC-222 with those of ciprofloxacin, ofloxacin, and lomefloxacin. CFC-222 was more active than the other fluoroquinolones tested against gram-positive bacteria. CFC-222 was particularly active against Streptococcus pneumoniae (MIC at which 90% of isolates are inhibited [MIC90], 0.2 microg/ml), Staphylococcus aureus (MIC90, 0.2 microg/ml for ciprofloxacin-susceptible strains), and Enterococcus faecalis (MIC90, 0.39 microg/ml). Against Escherichia coli and other members of the family Enterobacteriaceae, CFC-222 was slightly less active than ciprofloxacin (MIC90s for E. coli, 0.1 and 0.025 microg/ml, respectively). The in vitro activity of CFC-222 was not influenced by inoculum size, medium composition, or the presence of horse serum. However, its activity was decreased significantly by a change in the pH of the medium from 7.0 to 6.0, as was the case for the other quinolones tested. The in vivo protective efficacy of CFC-222 by oral administration was greater than those of the other quinolones tested in a mouse model of intraperitoneally inoculated systemic infection caused by S. aureus. CFC-222 exhibited efficacy comparable to that of ciprofloxacin in the same model of infection caused by gram-negative organisms, such as E. coli and Klebsiella pneumoniae. In this infection model, CFC-222 was slightly less active than ciprofloxacin against Pseudomonas aeruginosa. These results suggest that CFC-222 may be a promising therapeutic agent in various bacterial infections.
Animals↗
Role of mRNA termination in regulation of ermK.
To study the role of mRNA termination in the regulation of ermK, we introduced mismatches into terminators by in vitro mutagenesis. In wild-type ermK, only truncated transcription products were detected in the absence of induction. In contrast, only the full-length transcript was synthesized in the terminator 1 and terminator 2 double mutants, even in the absence of erythromycin. These results indicate that the expression of ermK is primarily regulated by transcriptional attenuation rather than translational attenuation. We also tested the possible contribution of translational attenuation control to the regulation of ermK by constructing a triple mutant (terminator 1 plus terminator 2 plus the methylase Shine-Dalgarno region). A higher level of beta-galactosidase synthesis was seen in the triple mutant. Therefore, unlike with previously described attenuators, it can be concluded that both transcriptional and translational attenuation contribute to the regulation of ermK, although transcriptional attenuation plays a larger role.
Bacillus subtilis↗
Cloning and sequencing of the Klebsiella K-36 astA gene, encoding an arylsulfate sulfotransferase.
A gene-encoding arylsulfate sulfotransferase (ASST) was cloned from a Klebsiella K-36 genomic library. ASST transfers a sulfate group from phenolic sulfate esters to a phenolic acceptor substrate. The gene, designated astA, was subcloned into vector pGEM3Zf(-) and sequenced. Recombinant clone-harbouring astA was directly identified using a fluorescent product. The nucleotide sequencing revealed an open reading frame (ORF) of 2,082 bp encoding a protein of 694 amino acids with a secretory signal sequence. A protein of similar size was visualized after in vitro transcription and translation using a plasmid carrying the cloned 3.1-kb fragment as a template. The N-terminal amino acid sequence of the purified processed protein was found to be identical to that predicted from the gene sequence. When searching the database for astA nucleotide or its deduced amino acid sequence, no significant homology to any sequence was found.
Amino Acid Sequence↗
A contrast of mothering behaviors in women from Korea and the United States.
In both the United States and Korea, culture heavily influences a mother's behavior toward her infant. Differences between these two cultures are explored, based on the author's experiences and work in both environments. This comparison includes a number of points of departure. The American culture encourages autonomous and independent behaviors from infants, whereas in the Korean culture, mothers tend to view infants as passive and dependent. American mothering is individually fashioned and relies on the expertise of health care providers. Conversely, the Korean culture is highly ritualistic, so mothering is molded more by societal rules than by individual design, and professional advice is less sought for guidance than is folklore information. American mothers tend to rear their infants in a nuclear family setting, whereas Korean mothers rear their infants in an extended family or at least in a highly social environment. Implications for American nurses who provide perinatal care for Korean immigrant women are discussed.
Cross-Cultural Comparison↗