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Biomedical subjects

C Y Lee

Publications and source records attributed to C Y Lee.

At least 127 records · Page 7Linked to original sources
PubMed1999

Determination of organochlorine pesticide residues in foods using solid-phase extraction clean-up cartridges.

Fourteen organochlorine pesticide residues in fatty foods were determined using a simple and rapid procedure based on solid-phase extraction (SPE) clean-up cartridges with octadecyl (C18)-bonded porous silica, a tandem C18 and Florisil column, Alumina-N and Florisil. A Florisil cartridge eluted with 12 ml petroleum ether-ethyl ether (95 + 5) was the most efficient clean-up procedure capable of eliminating the matrix interference and satisfying the agreed acceptable recovery for the large numbers of organochlorine pesticides in nine kinds of foods having different fat contents. Average recoveries of organochlorine pesticides in shellfish, fish and meats ranged from 77 to 105%, 84 to 98% and 85 to 107%, respectively. In addition, analysis of a certified Standard Reference Material (SRM 1945) verified the satisfactory performance of Florisil clean-up cartridge. This SPE method not only yielded comparable results for nonfatty foods, but also provided a reliable separation and quantification of organochlorine pesticides for analyzing a large number of foods with a wide range of fat content.

Chromatography, Gas↗
PubMed1999

Immunogenicity and safety of standard-titer AIK-C measles vaccine in nine-month-old infants.

Because of the interference by maternal antibody before 1 year of age, the Schwarz strain of measles vaccine, which has been routinely used in Taiwan, must be given at 9 months and 15 months of age to ensure an optimal immune response. The AIK-C strain of measles vaccine has been reported to be highly immunogenic. This study evaluated the immunogenicity and safety of the AIK-C vaccine in 9-month-old Taiwanese infants. A total of 135 infants were recruited and were randomly assigned to receive either Schwarz vaccine (68 cases) or AIK-C vaccine (67 cases). Measles antibodies were assayed before and 1 month after the vaccination. Sixty-five (97%) infants who received the AIK-C vaccine seroconverted after the vaccination, whereas the seroconversion rate in those receiving the Schwarz vaccine was 77% (P = 0.001). The incidences of adverse reactions were comparable between the two groups. We conclude that even in 1990s, the failure rate of Schwarz vaccine in 9-month-old infants is still high. The AIK-C vaccine is more immunogenic in infants and its long-term immunogenicity and safety deserve further evaluation.

Antibodies, Viral↗
PubMed1999

Cytochrome P450 MA expression in insecticide-resistant German cockroaches (Dictyoptera: Blattellidae).

Cytochrome P450 monooxygenases are detoxification enzymes commonly involved in insecticide resistance by insects. Recently, an overexpressed form of this enzyme, P450 MA, was purified from an insecticide-resistant strain of German cockroach, Blattella germanica (L.), and polyclonal antisera (anti-P450 MA) was produced. To test hypotheses that the overexpressed condition of P450 MA has evolved in > 1 geographic location and that P450 MA might be involved in insecticide resistance to specific insecticides, investigations were conducted using 4 insecticide-resistant and 1 susceptible German cockroach strains. In western blots that used anti-P450 MA antiserum as a probe, substantial differences in expression of P450 MA were observed. Strains showing the highest P450 MA expression had both the highest tolerance to the organophosphate insecticide chlorpyrifos and cytochrome P450-mediated demethylation activity. Results support the hypothesis that cytochrome P450 MA is potentially overexpressed in insecticide-resistant populations on a global scale.

Animals↗
PubMed1999

Sequence analysis of VP1 and VP7 genes suggests occurrence of a reassortant of G2 rotavirus responsible for an epidemic of gastroenteritis.

G2 rotavirus was prevalent in a 1993 epidemic of acute gastroenteritis in Taiwan. In this study, the genetic relationship among G2 rotavirus strains was analysed. The VP7 genes were amplified and sequenced. Except for one strain isolated in 1981, the nucleotide sequences of the VP7 genes of most of the G2 rotaviruses were very similar (identity > 97%) and were closely related to that of a Japanese G2 reference strain, S2. The genetic relatedness of G2 rotaviruses was analysed further by RNA-RNA hybridization. The genomes of the major G2 strains of 1993 did not hybridize well with those of the G2 strains of previous seasons in RNA segments 1, 6 and 7. Partial nucleotide sequences of the VP1 gene were analysed and appeared to be similar among the major G2 strains from the same epidemic (identity > 98%), whereas the identity of the VP1 genes of the major G2 strains of the 1993 epidemic to those of previous seasons was only about 84%. Since the numbers of mutations accumulated in the VP1 and VP7 genes over a period of 10 years were comparable, the significant change in the VP1 genes of the major strains of the 1993 epidemic suggests that these G2 rotaviruses had evolved by genetic reassortment.

Amino Acid Sequence↗
PubMed1999

Functional analysis of the Staphylococcus aureus collagen adhesin B domain.

The Staphylococcus aureus collagen adhesin (CNA) occurs in at least four forms that differ in the number (one, two, three, or four) of B domains. The B domains contain 187 amino acids and are located between the domains that anchor CNA to the cell envelope and the ligand-binding A domain. To determine whether a B domain is required for functional expression of CNA, we cloned the 2B cna gene from S. aureus strain Phillips and then eliminated both B domains by overlapping PCR. The absence of a B domain did not affect processing of the collagen adhesin to the cell surface or the ability to bind collagen. Based on our recent demonstration that the capsule can mask CNA on the surface of S. aureus cells (A. F. Gillaspy et al., Infect. Immun. 66:3170-3178, 1998), we also investigated the possibility that multiple B domains can extend the ligand-binding A domain outward from the cell surface and thereby overcome the inhibitory effect of the capsule. Specifically, we cloned the naturally occurring 4B CNA variant from S. aureus UAMS-639 and, by successive elimination of B domains, generated 1, 2, and 3B variants that are isogenic with respect to the 4B clone. After introducing each variant into microencapsulated and heavily encapsulated strains of S. aureus and growing cells under conditions known to affect capsule production (e.g., growth on Columbia agar), we correlated capsule production with exposure of CNA on the cell surface and the ability to bind collagen. Under no circumstance was the masking effect of the capsule reduced by the presence of multiple B domains. These results indicate that the B domains do not extend the ligand-binding A domain outward in a fashion that can overcome the inhibition of collagen binding associated with capsule production.

Adhesins, Bacterial↗
PubMed1999

Promoter analysis of the cap8 operon, involved in type 8 capsular polysaccharide production in Staphylococcus aureus.

The production of type 8 capsular polysaccharide (CP8) in Staphylococcus aureus is regulated in response to a variety of environmental factors. The cap8 genes required for the CP8 production in strain Becker are transcribed as a single large transcript by a primary promoter located within a 0.45-kb region upstream of the first gene of the cap8 gene cluster. In this study, we analyzed the primary cap8 promoter region in detail. We determined the transcription initiation site of the primary transcript by primer extension and identified the potential promoter sequences. We found several inverted and direct repeats upstream of the promoter. Deletion analysis and site-directed mutagenesis showed that a 10-bp inverted repeat of one of the repeats was required for promoter activity. We showed that the distance but not the specific sequences between the inverted repeat and the promoter was critical to the promoter activity. However, insertion of a DNA sequence with two or four helix turns in this intervening region had a slight effect on promoter activity. To demonstrate the biological significance of the 10-bp inverted repeat, we constructed a strain with a mutation in the repeat in the S. aureus Becker chromosome and showed that the repeat affected CP8 production mostly at the transcriptional level. By gel mobility shift assay, we demonstrated that strain Becker produced at least one protein capable of specific binding to the 10-bp inverted repeat, indicating that the repeat serves as a positive regulatory protein binding site. In addition, reporter gene fusion analysis showed that the cap8 promoter activity was influenced by various growth media and affected most by yeast extract. Our results suggest that yeast extract may exert its profound inhibitory effect on cap8 gene expression through the 10-bp inverted repeat element.

Bacterial Capsules↗
PubMed1999

Bacteremia due to extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in a pediatric oncology ward: clinical features and identification of different plasmids carrying both SHV-5 and TEM-1 genes.

Thirteen patients who had 16 episodes of bacteremia were observed between 1993 and 1997 in a pediatric oncology ward with a high background isolation rate of cefotaxime- or aztreonam-resistant gram-negative bacteria. Four blood isolates were Escherichia coli and 12 were Klebsiella pneumoniae, and these isolates harbored extended-spectrum beta-lactamases (ESBLs). All episodes of bacteremia were nosocomial, all except one of the episodes occurred in neutropenic patients, and all patients were treated with piperacillin or ceftazidime with amikacin and cefazolin prior to the onset of bacteremia. Nine of 13 patients were receiving extended-spectrum beta-lactam treatment when the bacteremias caused by ESBL producers occurred. Molecular studies revealed that four K. pneumoniae SHV-2-producing isolates from 1994 were of the same clone. Other ESBL producers, including six that carried both TEM-1 and SHV-5, five that carried SHV-5, and one that carried SHV-2 alone, were unrelated. In conclusion, SHV-5 was present in 11 of the 16 isolates and coexisted with TEM-1 in 6 isolates. Acquisition of resistance genes probably occurred under antibiotic selection pressure. This study highlights the importance of routine checks for and detection of ESBL producers. Effective therapy against ESBL producers should be considered early for children who have malignancies and neutropenia and who are septic, despite treatment with a regimen that includes an extended-spectrum beta-lactam, in a clinical setting of an increased incidence of ESBL-producing bacteria.

Adolescent↗
PubMed1999

Pertussis toxin-induced lung edema. Role of manganese superoxide dismutase and protein kinase C.

The mechanism by which pertussis toxin (Ptx) causes lung edema is not clear. We investigated the role of pulmonary manganese superoxide dismutase (MnSOD) and protein kinase C (PKC) in Ptx-induced lung edema. We demonstrated that intraperitoneal injection of Ptx at a concentration of 5 microg/100 g body weight caused a similar degree of lung edema in 2 d, as measured by lung wet weight/dry weight ratio, in heterozygous MnSOD gene (Sod2)-knockout mice (Sod2(+/-)) and in their wild-type littermates (Sod2(+/+)). The level of lung MnSOD activity in Sod2(+/-) mice was approximately half that of Sod2(+/-) mice. Ptx had no effect on levels of lung MnSOD messenger RNA, immunoreactive protein, or enzyme activity in either Sod2(+/+) or Sod2(+/-) mice. Ptx also had no effect on lung copper-zinc SOD, catalase, and glutathione peroxidase activities in these mice. On the other hand, Ptx caused the activation of lung PKC, for example, by translocation of a 72-kD PKC isoform from the cytosolic fraction to the membrane fraction. Pretreatment of mice with bisindolylmaleimide, a PKC inhibitor, prevented both the Ptx-induced activation of PKC and lung edema. These data suggest that Ptx-induced lung edema in mice is, at least in part, due to the activation of lung PKC.

Animals↗
PubMed1999

Kinetics of enamel demineralization in vitro.

Previously, we reported that the rate (R) of hydroxyapatite dissolution in acetic, lactic, and phosphoric acid solutions is a function of the degree of saturation with respect to the dissolving mineral, DS (defined as the ratio of the mean ionic activity product for hydroxyapatite [Ca5OH(PO4)3] in solution to its solubility product constant), and the sum of the acid activities (sumBiH) in solution: R = K(1-DS)m(sumBiH)n. The present study was undertaken to explore the general validity of this model in describing the kinetics of enamel demineralization. Thin sections of human enamel were exposed to partially saturated 0.1 mol/L lactic acid solutions, at two different DS levels, and at pH values of 4.3 to 6.0. Thin sections of human enamel were also exposed to solutions with four different concentrations of acetic and lactic acids (pH 4.3) with three different DS values and, at one DS value, to solutions of propionic acid. Mineral loss was monitored by quantitative microradiography. In solutions with pH values of 4.3 and 5.0, "lesions" were formed with well-defined surface layers, whereas, in solutions with pH 6.0, "lesions" were produced with no apparent surface layers. The formation of relatively intact surface layers was consistent with predicted phase transformations. Rates of mineral loss were found to be inversely proportional to both the degree of saturation with respect to enamel mineral, DS(En), and the pH of the solution and increased with increased activities of each organic acid, consistent with the proposed model. However, at the same DS(En) and acid activity, rates of demineralization were the same in the acetic and propionic acid solutions, whereas rates of demineralization in lactic acid were greater. It is suggested that specific interactions of acid species with enamel mineral may modify the rate of enamel demineralization. These in vitro findings suggest that relatively small differences in DS(En) values found in plaque fluid may result in very significant differences in the rate of enamel demineralization in vivo.

Acetates↗
PubMed1999

An evaluation of the safety and immunogenicity of a five-component acellular pertussis, diphtheria, and tetanus toxoid vaccine (DTaP) when combined with a Haemophilus influenzae type b-tetanus toxoid conjugate vaccine (PRP-T) in Taiwanese infants.

OBJECTIVE: Immunologic interference particular to the Haemophilus influenzae type b (Hib) response has been observed with previous acellular pertussis-Hib combination vaccines. To test this hypothesis a clinical trial to assess the safety and immunogenicity of a five-component (pertussis toxoid [PT], filamentous hemagglutinin [FHA], pertactin [PRN], and fimbriae 2 and 3 [FIM]), pertussis vaccine combined with diphtheria and tetanus toxoids (DTaP) when given simultaneously with a lyophilized Hib-tetanus toxoid conjugate vaccine (PRP-T) in infants at 2, 4, 6, and 18 months of age was conducted. The study compared two methods of administration: both vaccines combined in a single syringe and administered as a single injection, or both vaccines administered concurrently but at separate sites of injection. METHODS: Healthy 2-month-old infants were enrolled at the National Taiwan University Hospital. DTaP, PRP-T, and oral poliomyelitis vaccine (OPV) were given at 2, 4, 6, and 18 months. Reaction information was collected by telephone 2 days after each vaccination. Serum was collected at 2, 6, 7, 18, and 19 months of age. RESULTS: One hundred thirty-five healthy infants were enrolled in Taiwan, of which 127 (94%) completed the 18-month booster: 68 received the combined vaccine and 67 the separate vaccines. All vaccines were well tolerated. No differences in rates of local and systemic reactions were seen between the two methods of administration. No serious adverse events were reported. Serologic responses were comparable between the groups. Pertussis responses (enzyme-liked immunoabsorbant assay units [EU]/mL) at 7 months were, for combined versus separate, PT (131 vs 105), FHA (116 vs 116), PRN (100 vs 77), and FIM (922 vs 702). At 19 months, pertussis results were, for combined versus separate, PT (216 vs 182), FHA (203 vs 200), PRN (263 vs 197), and FIM (892 vs 732). Only the 7-month PT response in the combined group was significantly higher (combined 131 EU/mL vs separate 105 EU/mL). After the third dose (age 6 months), all subjects achieved serologic serum antibody levels indicative of protection against Hib, diphtheria, tetanus, and poliovirus types 1, 2, and 3. In fact, 96% of children had anti-PRP levels indicative of protection (>/=0.15 microgram/mL) against Hib after only two doses. At 7 months, anti-PRP geometric mean titer values were 11.8 micrograms/mL in the combined group compared with 13.0 micrograms/mL in the separate group. The anti-PRP geometric mean titers after the 18-month booster were 58.5 micrograms/mL in the combined group versus 55.3 micrograms/mL in the separate group. CONCLUSION: The five-component DTaP vaccine may be combined with PRP-T vaccine without clinically significant immunologic interaction when given in a 2-, 4-, 6-, and 18-month schedule.

Diphtheria↗
PubMed1999

Source memory in Parkinson's disease.

Three experiments (ns = 14 per group) are reported which investigated the ability of Parkinson patients to remember the characteristics of conditions under which a memory was acquired. In Exp. 1, subjects were required to indicate for each item in a recognition memory test whether it was spoken by Experimenter 1 or by Experimenter 2 (external-external source memory). In Exp. 2, subjects had to indicate for each item whether it was generated by themselves or by the experimenter (internal-external source memory). In Exp. 3, subjects had to judge whether an item was generated by themselves in saying or in thinking (internal-internal source memory). We found that patients with Parkinson's disease were not impaired in the previous two kinds of source memory (Exp. 1 and 2) but were impaired in internal-internal source memory (Exp. 3) relative to the age-matched control groups. In addition, both groups' performance could be improved when given distinctive cues, i.e., perceptual cues in Exp. 1 and different-domain cues in Exp. 2. These results suggest that the availability of cues was critical for Parkinson's disease in source memory. Finally, the result of Exp. 2 also showed generation effects for patients with Parkinson's disease. The generation effect refers to better memory of information by people when they had to produce it, e.g., producing associates to a word, compared with memory of information given to them.

Adult↗
PubMed1999

An incidental case of human Heterophyes nocens infection diagnosed by sectional morphology in a biopsy specimen of the small intestine.

A case of human infection with Heterophyes nocens (Heterophyidae) was incidentally found in a biopsy specimen of the Meckel's diverticulum at the upper part of the small intestine. The patient was a 58-year-old man living in a rural area of Talsonggun, Kyongsangbuk-do. He had gastrointestinal symptoms such as epigastric pain, indigestion, and abdominal discomfort for 3 months, and severe diarrhea, abdominal pain, and vomiting for about 1 month before hospitalization. Endoscopy of the upper part of the small intestine revealed a Meckel's diverticulum, and it was excised and histopathologically examined. Three adult flukes were incidentally found sectioned in the mucosa, and they were identified as H. nocens. The patient had a history of eating raw mullets at a fish market in Pusan 6 months ago, and the mullets were presumed to be the source of infection. This case brings a considerable interest in that specific diagnosis of heterophyid infections could be done by sectional morphology of the worms.

Animals↗
PubMed1999

Immunogenicity of oral poliovirus vaccine in Taiwan.

Previous studies have shown that the immune response to trivalent oral poliovirus vaccine (OPV) varies widely from country to country. However, there has been no report on the immunogenicity of this vaccine in Taiwanese children. In this study, 98 children were followed up for 17 months to study the antibody responses following four doses of trivalent OPV. The results showed that, after two doses of vaccine, all children were protected against poliovirus type 1 and 2. All except two children also developed protective antibodies against poliovirus type 3. After three doses, the antibody levels in all subjects were above protective concentrations. The fourth dose, given at 18 months of age, further boosted the antibody titers. These findings show that the OPV currently used in Taiwan is highly immunogenic in Taiwanese children.

Antibodies, Viral↗
PubMed1999

Penicillin-nonsusceptible Streptococcus pneumoniae infections in children.

The emergence of penicillin-nonsusceptible Streptococcus pneumoniae (PNSSP) has brought a new clinical challenge. In Taiwan, reports of the prevalence and clinical features of PNSSP infections in children are limited. This study reviewed the resistance patterns of all clinical isolates of S. pneumoniae obtained from patients under 17 years of age from January 1993 through July 1998 in a medical center. Their clinical features and treatment responses were analyzed, with special attention paid to those patients with invasive PNSSP infections. Totally, 170 clinical isolates of S. pneumoniae were obtained from 168 patients aged under 17 years. Among those infections, there were 56 sinusitis (including 4 sinusitis with bacteremia), 44 pneumonia (including 23 pneumonia with bacteremia or empyema), 23 otitis media (including 5 otitis media with bacteremia), 9 simple bacteremia, 9 conjunctivitis, 8 meningitis, 4 peritonitis, 3 skin infections and the other 14 isolates were colonization. One hundred eleven isolates (65.3%) showed reduced penicillin susceptibility by the disk diffusion method. A trend of increasing percentiles of PRSP was noted: 27.3% (3/11) in 1993, 37.5% (9/24) in 1994, 55.5% (10/18) in 1995, 77.5% (31/40) in 1996, 66.0% (31/47) in 1997, and 87.1% (27/31) in 1998. Minimum inhibitory concentration (MIC) determinations by the E-test showed some of the isolates were intermediately resistant. Prior antibiotic usage was associated with a higher incidence of PNSSP infections. However, most children responded well to antimicrobial treatment.

Adolescent↗
PubMed1999

Anaesthesia Incident Monitoring Study in Hospital Kuala Lumpur--the second report.

Critical incident reporting is a useful quality improvement technique for reducing morbidity and mortality in anaesthesia. This study analyses 93 cases in Kuala Lumpur Hospital from July 1995 to January 1997. The main incidents during anaesthesia in this study were airway incidents. While human error was identified as the main factor contributing to the occurrence of adverse incidents. Critical incident monitoring plays an important role in identifying potential problems, which may lead to disaster. The findings from this report of the anaesthesia incident monitoring study continued to indicate the occurrence of similar problems seen in an earlier report. The identification of common incidents can be used to identify risk factors and minimise repetition of such incidents.

Adolescent↗
PubMed1998

Recombinant acyl-CoA:cholesterol acyltransferase-1 (ACAT-1) purified to essential homogeneity utilizes cholesterol in mixed micelles or in vesicles in a highly cooperative manner.

Acyl-coenzyme A:cholesterol acyltransferase (ACAT) is an integral membrane protein located in the endoplasmic reticulum. It catalyzes the formation of cholesteryl esters from cholesterol and long-chain fatty acyl coenzyme A. The first gene encoding the enzyme, designated as ACAT-1, was identified in 1993 through an expression cloning approach. We isolated a Chinese hamster ovary cell line that stably expresses the recombinant human ACAT-1 protein bearing an N-terminal hexahistidine tag. We purified this enzyme approximately 7000-fold from crude cell extracts by first solubilizing the cell membranes with the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate, then proceeding with an ACAT-1 monoclonal antibody affinity column and an immobilized metal affinity column. The final preparation is enzymologically active and migrates as a single band at 54 kDa on SDS-polyacrylamide gel electrophoresis. Pure ACAT-1 dispersed in mixed micelles containing sodium taurocholate, phosphatidylcholine, and cholesterol remains catalytically active. The cholesterol substrate saturation curves of the enzyme assayed either in mixed micelles or in reconstituted vesicles are both highly sigmoidal. The oleoyl-coenzyme A substrate saturation curves of the enzyme assayed under the same conditions are both hyperbolic. These results support the hypothesis that ACAT is an allosteric enzyme regulated by cholesterol.

Acyl Coenzyme A↗
PubMed1998

Synthesis and cytotoxicity of 2-acetyl-4,8-dihydrobenzodithiophene-4, 8-dione derivatives.

2-Acetyl-4,8-dihydrobenzo[1,2-b:4,5-b']dithiophene-4,8-dione (9) and 2-acetyl-4,8-dihydrobenzo[1,2-b:5,4-b']dithiophene-4,8-dione (19), together with 10 related mono- and disubstituted derivatives, were synthesized and evaluated in vitro by NCI against eight cancer types. All compounds showed significant activity against melanoma, HL-60 leukemia, NCI-H23 non-small-cell lung cancer, OVCAR-3 ovarian cancer, and MDA-MB-435 and MDA-N breast cancer cell lines. Compound 11, 2-(1'-acetoxyethyl)-4,8-dihydrobenzo[1,2-b:4,5-b']dithiophene-4, 8-dione, showed the highest overall potency (mean GI50 = 40 nM).

Animals↗