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Biomedical subjects

H Lee

Publications and source records attributed to H Lee.

At least 559 records · Page 31Linked to original sources
PubMed1995

Mutagenicity of particulates from the laboratory combustion of plastics.

Carcinogenic polycyclic aromatic hydrocarbons (PAHs) and nitropolycyclic aromatic hydrocarbons (nitro-PAHs) have been identified in airborne particulate organic matter extracts. The pollutant sources were generally contributed by motor vehicles and industrial activity. Massive quantities of urban solid wastes, containing plastic materials such as PVC, PET, PS, and PE, burnt in the open air in local garbage dumps are frequently found in developing countries. In this study, the smog particulates from the combustion of these synthetic polymers were produced in a laboratory combustion chamber. The mutagenicity of acetone extracts from the smog particulates was evaluated with Salmonella typhimurium TA98 and TA100 in the presence and absence of S9 mix. Four samples in TA98 exhibited higher mutagenicity than those in TA100. The greatest mutagenicity was observed from the extracts of particulates from combustion of PVC followed by that of PS, PET, and PE. To determine the major mutagenic compounds in these samples, mutagens were partially purified through TLC and their mutagenicity was monitored with TA98. 1-NP and DNPs in the above samples were also determined by HPLC. The amounts of 1-NP and DNPs generally corresponded with their mutagenicity. Higher levels of 1-NP and DNPs were generated from the combustion of PVC, PET, and PS. The combustion of synthetic polymer wastes might be responsible for the presence of high levels of 1-NP and DNPs in Taiwan urban air.

Air Pollutants↗
PubMed1995

Detection of antibodies to Trypanosoma cruzi among blood donors in the southwestern and western United States. I. Evaluation of the sensitivity and specificity of an enzyme immunoassay for detecting antibodies to T. cruzi.

BACKGROUND: Chagas' disease or American trypanosomiasis, caused by infection with Trypanosoma cruzi, is a significant health problem in Latin America. In the United States, transfusions of T. cruzi-contaminated blood from Latin American immigrants may represent the major source of Chagas' disease. STUDY DESIGN AND METHODS: A new enzyme immunoassay (EIA) for the detection of antibody to T. cruzi was evaluated in the sera of blood donors from the southwestern and western regions of the United States. Serum samples had been screened and were negative for all tests required. Specimens that were repeatedly reactive in the Chagas antibody EIA were analyzed for seroreactivity by a confirmatory EIA and by radioimmunoprecipitation assay. RESULTS: Fourteen of the 13,309 donor samples (0.105%) were confirmed as being positive for antibody to T. cruzi. The Chagas antibody EIA showed improved sensitivity over the Chagas IgG enzyme-linked immunosorbent assay and two indirect hemagglutination assays. The Chagas antibody EIA had a specificity of 99.98 percent with negative samples. The sensitivity of the Chagas antibody EIA was 100 percent (80/80) in xenodiagnosed specimens and 100 percent (50/50) in specimens positive by consensus (i.e., reactive in EIA, indirect hemagglutination assay, and immunofluorescence assays). CONCLUSION: This Chagas antibody EIA meets the need for accurate and rapid identification of seroreactive samples in low-prevalence or endemic populations.

Animals↗
PubMed1995

Human immunodeficiency virus type 1 infection: relationship of risk group and age to rate of progression to AIDS. Transfusion Safety Study Group.

Age differences among risk groups may account for rate differences in progression of human immunodeficiency virus type 1 (HIV-1) infection to AIDS. Institutions in 6 US cities used a common protocol to study infected homosexual blood donors, recipients of blood components, and factor VIII-treated hemophiliacs. Follow-up was every 6 months. Actuarial risk for AIDS 8 years after infection was 51% among blood recipients, 36% among homosexual donors, and 24% among hemophiliacs. Significant risk group differences were explained by age differences among cohorts (medians of 61, 29, and 22 years, respectively). When age was adjusted for and both CD4 cell value and zidovudine treatment were used as time-dependent covariates, homosexual donors had more rapid progression than the other groups. Omitting Kaposi's sarcoma as an AIDS-defining condition removed any significant differences among risk groups except CD4 cell count and age. Thus, major factors in AIDS progression are age-related.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Effects of Maillard reaction products on mutagen formation in boiled pork juice.

The three IQ (2-amino-3-methylimidazo[4,5-f]quinoline) compounds IQ, MeIQx (2-amino-3,4-dimethyl[4,5-f]quinoxaline) and MeIQ (2-amino-3,4-dimethylimidazo[4,5-f]quinoline) have been found in boiled pork juice. To determine which Maillard reaction products are important in the formation of IQ-type mutagens in boiled pork juice, six Maillard reaction products were separately added to the pork juice before reflux boiling and then the mutagenicity of each sample was examined with Salmonella typhimurium TA98 in the presence of S9 mix. The addition of four Maillard reaction products enhanced the mutagenicity of pork juice 1.2-2.9-fold after reflux boiling. The highest level of enhancement was observed with tetrahydrothiophene, followed by 2,3-dimethylpyrazine, 3-methylpyridine and 2-methylpyridine. However, the addition of 2-acetylpyrrole and imidazole greatly inhibited the mutagenicity of pork juice. To confirm which IQ-type mutagens were changed, four major mutagenic fractions were monitored after HPLC separation by their mutagenicity with Salmonella typhimurium TA98. By comparing the retention time of authentic IQ compounds from boiled pork juice with added tetrahydrothiophene or 2,3-dimethylpyrazine, we show that four major HPLC fractions have significantly increased mutagenicity compared with the same fractions in boiled pork juice alone. In contrast, the mutagenicity of these fractions was considerably reduced with the addition of imidazole or 2-acetylpyrrole to the pork juice before refluxing. The residual amounts of tetrahydrothiophene and 2,3-dimethylpyrazine added to the boiled pork juice after heating were measured by gas chromatography and found to be inversely correlated with the mutagenicity of the pork juice.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Recombinant and wild-type Pseudomonas aureofaciens strains introduced into soil microcosms: effect on decomposition of cellulose and straw.

The effect of a genetically engineered Pseudomonas aureofaciens (Ps3732RNL11) strain (GEM) and the parental wild-type (Ps3732RN) on decomposition of cellulose paper, straw and calico cloth was assessed after 18 weeks incubation in laboratory soil microcosms. Effect(s) of inoculum density (10(3), 10(5), and 10(8) cells/g dry soil) and single versus multiple bacterial inoculations were also investigated. Cellulose paper was completely decomposed after 18 weeks in all treatments. There were no significant differences (95% level), between treatments, in percentage decomposition of either straw or calico cloth. Recovery of the GEM at 18 weeks, using viable plating, was limited to treatments originally receiving 10(8) cells/g dry soil. Log 1.8 CFU/g dry soil were recovered from the single dose treatment while log 4.2 CFU/g dry soil were recovered from the multiple dose treatment. Biolog metabolic tests were used to determine if the GEM or parental wild-type had any effect on overall carbon utilization in soil. Results suggested they did not. Detection of the recombinant lacZY gene sequence in soil using PCR suggested the possibility of viable but nonculturable cells and/or persistence of chromosomal DNA.

Bacteria, Aerobic↗
PubMed1995

Ligase chain reaction for detection of Neisseria gonorrhoeae in urogenital swabs.

The ligase chain reaction (LCR) is an in vitro nucleic acid amplification technique that exponentially amplifies targeted DNA sequences. In a multicenter study, we evaluated the use of a 4-h LCR-based assay for the diagnosis of Neisseria gonorrhoeae infection of the cervix and male urethra. The LCR results were compared with those of culture for N. gonorrhoeae by using selective media. This assay amplifies target sequences within the N. gonorrhoeae opacity gene. Discordant LCR-positive and culture-negative specimens were further evaluated by testing by another LCR assay which used N. gonorrhoeae-specific pilin probe sets. A total of 1,539 female endocervical specimens and 808 male urethral swab specimens were evaluated in the study. An expanded "gold standard" was defined to include all culture-positive as well as culture-negative, confirmed LCR-positive specimens. After resolution of discrepant samples, the sensitivities of the N. gonorrhoeae LCR assays for the female and male specimens were 97.3 and 98.5%, respectively, with specificities of 99.6 and 99.8%, respectively. Resolved culture sensitivities were 83.9 and 96.5% for the female and male specimens, respectively. The LCR assay for gonorrhea is a rapid, highly sensitive nonculture method for detecting gonococcal infection of the cervix and male urethra.

Bacteriological Techniques↗
PubMed1995

Evaluation of ligase chain reaction for use with urine for identification of Neisseria gonorrhoeae in females attending a sexually transmitted disease clinic.

The high sensitivity of nucleic acid amplification tests such as ligase chain reaction (LCR) has the potential to simplify specimen collection for the microbiologic diagnosis of gonorrhea. We screened first-void urine specimens from 283 women attending a Birmingham, Ala., sexually transmitted disease (STD) clinic by using LCR and compared the results to those of cervical and urethral cultures for gonorrhea diagnosis. Fifty-three (18.7%) women had positive cervical cultures for gonorrhea, and 41 of the 53 (77%) also had positive urethral cultures. One additional patient had only a positive urethral culture (the cervical gonorrhea culture was negative). LCR testing of urine specimens for gonorrhea yielded positive results for 51 of 54 (94.4%) women with positive cervical or urethral cultures. Of 229 women with both urethral and cervical cultures negative for gonorrhea, 2 (0.8%) had positive urine LCR results as well. To resolve the discrepancies between urine LCR and culture results, LCR tests of simultaneously collected urethral and cervical swab specimens and LCR tests of the same urine specimens using different nucleotide primers were conducted. After evaluation of five discrepant results, the sensitivity, specificity, positive predictive value, and negative predictive value of LCR for the detection of gonorrhea in urine specimens were 94.6%, 100%, 100%, and 98.7%, respectively. We conclude that urine LCR testing for Neisseria gonorrhoeae is a practical alternative to culture for the detection of gonorrhea in women. Urine testing for STD diagnosis has the potential to simplify and expand the opportunities for STD screening and surveillance of women.

Ambulatory Care Facilities↗
PubMed1995

Detection of Chlamydia trachomatis infection in urine samples from men and women by ligase chain reaction.

The suitability of urine specimens from women and men for the detection of Chlamydia trachomatis infection by a ligase chain reaction (LCR)-based assay with plasmid primers was examined with a group of patients attending a sexually transmitted disease clinic in Amsterdam, The Netherlands. Cervical specimens from 15 of 237 (6.3%) women tested positive for C. trachomatis by cell culture. Of the 25 (10.5%) female urine samples that tested positive by the plasmid-LCR assay, 13 were obtained from cervical culture-positive women. Nine of the 12 plasmid-LCR-positive urine samples from cervical culture-negative women were confirmed to be positive by a second LCR assay with primers based on chromosomal DNA. Urethral specimens from 24 of 258 (9.3%) men were positive for C. trachomatis infection by cell culture. Of the 25 (9.7%) urine samples that tested positive by plasmid-LCR, 20 were from culture-positive men. All five of the LCR-positive urine samples from culture-negative men were confirmed to be positive by the LCR with chromosomal DNA primers. Relative to cell culture, testing by plasmid-LCR analysis of male urine samples had a sensitivity of 83.3% and a specificity of 97.9%; after resolution of discordant samples, these values were 86.2 and 100%, respectively. In the study with women, the sensitivities of plasmid-LCR analysis of cervical and urine specimens in comparison with cervical cell culture were 93.3 and 86.7%, respectively. After resolution of discrepant samples, the sensitivities of the plasmid-LCR test for cervical swabs and female urine samples were 96.3 and 92.6%, respectively. These results indicate that the plasmid-LCR-based assay is a very reliable, sensitive, convenient test for the detection of C. trachomatis infection in female and male urine specimens.

Bacteriological Techniques↗
PubMed1995

Screening urine samples by leukocyte esterase test and ligase chain reaction for chlamydial infections among asymptomatic men.

Urine samples from 358 asymptomatic males were screened for urethral inflammation by the leukocyte esterase (LE) test and for Chlamydia trachomatis by the ligase chain reaction (LCR). LE and LCR positivity rates were 7.5% (27 of 358 samples) and 2.8% (10 of 358 samples), respectively. Eight of the 10 LCR-positive samples were detected by the LE screening test. The urine LE prescreening test in combination with the LCR assay may be a reasonable approach for genitourinary chlamydial disease control.

Bacteriological Techniques↗
PubMed1995

The translation initiation factor eIF-4E binds to a common motif shared by the translation factor eIF-4 gamma and the translational repressors 4E-binding proteins.

Eukaryotic translation initiation factor 4E (eIF-4E), which possesses cap-binding activity, functions in the recruitment of mRNA to polysomes as part of a three-subunit complex, eIF-4F (cap-binding complex). eIF-4E is the least abundant of all translation initiation factors and a target of growth regulatory pathways. Recently, two human cDNAs encoding novel eIF-4E-binding proteins (4E-BPs) which function as repressors of cap-dependent translation have been cloned. Their interaction with eIF-4E is negatively regulated by phosphorylation in response to cell treatment with insulin or growth factors. The present study aimed to characterize the molecular interactions between eIF-4E and the other subunits of eIF-4F and to similarly characterize the molecular interactions between eIF-4E and the 4E-BPs. A 49-amino-acid region of eIF-4 gamma, located in the N-terminal side of the site of cleavage by Picornaviridae protease 2A, was found to be sufficient for interacting with eIF-4E. Analysis of deletion mutants in this region led to the identification of a 12-amino-acid sequence conserved between mammals and Saccharomyces cerevisiae that is critical for the interaction with eIF-4E. A similar motif is found in the amino acid sequence of the 4E-BPs, and point mutations in this motif abolish the interaction with eIF-4E. These results shed light on the mechanisms of eIF-4F assembly and on the translational regulation by insulin and growth factors.

Adaptor Proteins, Signal Transducing↗
PubMed1995

Survival of and lacZ expression in recombinant Pseudomonas strains introduced into river water microcosms.

The lacZY gene cassette inserted into the chromosome of Pseudomonas aeruginosa UG2Lr and Pseudomonas aureofaciens Ps3732RNL11 was used as a genetic marker to study the fate of the Pseudomonas strains in river water microcosms. Expression of the lacZ marker in UG2Lr and Ps3732RNL11 was detected in microcosms containing as few as 12 and 14 colony-forming units (cfu)/mL of river water, respectively, by fluorimetric measurement of the beta-galactosidase activity against 4-methylumbelliferyl-beta-D-galactoside as the substrate. The persistence of and lacZ expression in the pseudomonas strains were monitored in sterile and nonsterile river water in the presence and absence of added nutrients by dilution plating and fluorimetry, respectively. After incubation for 10 d at 10 degrees C, culturable populations of strain UG2Lr in sterile water samples, with and without nutrient added, decreased from an initial density of 1.5 x 10(4) to 1.7 x 10(3) and 4.6 x 10(3) cfu/mL, respectively. Despite similar numbers of UG2Lr cells in the two treatments, expression of the lacZ marker in the surviving cells of the nutrient-supplemented sample was 24 times higher than in the cells of the unamended sample. In nonsterile water samples, the density of UG2Lr declined to less than 6 cfu/mL in 30 d regardless of the nutrient conditions. A nutrient supplement increased the growth of the native bacterial population but did not enhance growth of and lacZ expression in the bacteria. Polymerase chain reaction analysis showed a decrease in amplification signal indicating a genuine decline in viable UG2Lr cell density in the water samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1995

Prevalence of diabetes and IGT in Yonchon County, South Korea.

OBJECTIVE: To determine the prevalence of diabetes and impaired glucose tolerance (IGT) in Yonchon County of South Korea and to investigate their associated factors. RESEARCH DESIGN AND METHODS: We performed a population-based cross-sectional study with random cluster sampling of residents > or = 30 years of age. Among the 3,804 residents sampled, a total of 2,520 participants had a standard 75-g oral glucose tolerance test and answered a detailed questionnaire. We also collected standard anthropometric data. RESULTS: If the data for participants in the age range of 30-64 years were adjusted to the standard world population, the prevalence of diabetes was 7.2% and the prevalence of IGT was 8.9%. It was observed that the significant factors associated with diabetes were waist-to-hip circumference ratio, serum triglyceride levels, age, systolic blood pressure, family history of diabetes, and locality. CONCLUSIONS: The prevalence of diabetes in Yonchon County was substantially higher than was previously suggested. The risk of diabetes increased with the increased central obesity and metabolic disturbances associated with insulin resistance.

Adult↗
PubMed1995

Two classes of structurally different antagonists display similar species preference for the human tachykinin neurokinin3 receptor.

Two classes of structurally different tachykinin neurokinin3 (NK3) antagonists were used to evaluate species difference in antagonist binding between human and rat NK3 receptors. In competition binding experiments with [125I-MePhe7]NKB as radioligand, PD 154740, PD 157672, SR 48968, and SR 142801 displayed lower Ki values for the human NK3 receptor (40 +/- 4, 12 +/- 1,350 +/- 50, and 0.40 +/- 0.05 nM, respectively) than for the rat NK3 receptor (2450 +/- 130, 288 +/- 25, > 10,000, and 11.0 +/- 0.5 nM, respectively). Data from in vitro functional assay showed similar species preference as observed with the competition binding assay. It was shown previously that substitution of only two amino acid residues in the rat receptor to their human counterparts could change the species selectivity of SR 48968, a weak NK3 antagonist. In the double-substituted rat mutant, all three antagonists (PD 154740, PD 157672, and SR 142801) displayed Ki values (76 +/- 8, 16 +/- 2, and 0.50 +/- 0.05 nM, respectively) very similar to the Ki values for the wild-type human NK3 receptor. Thus, in addition to their previously reported effects on SR 48968, these two amino acid residues are responsible for the species selectivity of these three additional NK3 antagonists. Because PD 154740 and PD 157672 are very different structurally from SR 48968 and SR 142801, our results indicate that the two identified residues may be involved in adopting a receptor conformation that favors the binding of NK3 antagonists that display species preference for the human NK3 receptor.

Animals↗
PubMed1995

Stage specific identification of the expression of GnRH mRNA and localization of the GnRH receptor in mature rat and adult human testis.

PURPOSE: To identify the expression of gonadotropin-releasing hormone (GnRH) messenger ribonuclueic acid (mRNA) and localize GnRH receptors in mature rat and adult human testes. MATERIALS AND METHODS: In situ hybridization and enzymatic receptor binding localization were performed. RESULTS: GnRH mRNA was expressed within the seminiferous tubules in both mature rat and adult human testis. In rats, expression of GnRH mRNA was identified in the Sertoli cells and spermatogenic cells of some seminiferous tubules, but the other tubules did not express any hybridization signal. In humans, expression of GnRH mRNA was identified only in some spermatogenic cells in some seminiferous tubules. The receptors for GnRH were localized to cells in the interstitial tissues of the testis, probably Leydig cells. CONCLUSION: The authors believe that the mature rat and adult human seminiferous tubular cells produce GnRH at the same specific stage of the spermatogenic cycle and that GnRH produced within seminiferous tubules, including Sertoli cells and spermatogenic cells, reacts with neighboring GnRH receptors in interstitial cells, including Leydig cells. The GnRH produced from the Sertoli cells in seminiferous tubules would react with GnRH receptors in interstitial cells as a paracrine hormone.

Adult↗
PubMed1995

Oxidation of the angiotensin II receptor antagonist losartan (DuP 753) in human liver microsomes. Role of cytochrome P4503A(4) in formation of the active metabolite EXP3174.

The oxidative metabolism of losartan (DuP 753), a novel angiotensin II receptor antagonist, by human liver microsomes and purified cytochrome P450 (P450) enzymes, was studied. The primary route of metabolism of losartan is by oxidation of the C5-hydroxymethyl to the carboxylic acid (EXP3174), which is an active metabolite of losartan. When microsomes prepared from different human liver samples were compared, EXP3174 formation activity was well correlated (r2 = 0.93) with nifedipine oxidation (a marker of P4503A4), but not with markers for other human liver P450s. Microsomal oxidation of losartan to EXP3174 was markedly inhibited by gestodene and ketoconazole, selective inhibitors of P4503A enzymes, but not by any of several other P450 inhibitors. Antibodies raised against P4503A4 could inhibit most of the oxidation of losartan to EXP3174 in a microsomal sample having high catalytic activity, but antibodies recognizing other P450s had no effect. The oxidation of losartan to EXP3174 was catalyzed by purified human liver microsomal P4503A4 and by purified bacterial recombinant P4503A4. These results provide evidence that P4503A4 (and possibly other P4503A enzymes) play a major role in the formation of an active metabolite EXP3174.

Angiotensin II↗