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T Ong

Publications and source records attributed to T Ong.

At least 55 records · Page 3Linked to original sources
PubMed1994

Induction of in vivo DNA adducts by 4 industrial by-products in the rat-lung-cell system.

Benz[a]anthracene (BA), dibenz[a,h]anthracene (DBA), dibenzo[a,i]pyrene (DBP), and dibenz[a,h]acridine (DBAC) are by-products found in many industrial wastes and emissions. Workers in the related occupational settings are potentially exposed to these substances through inhalation. In the present study, induction of DNA adducts in vivo by these chemicals was investigated using 32P-postlabeling analysis in the rat-lung-cell system. The potency of DNA-adduct inducing activity was also compared to that of two cytogenetic endpoints i.e., sister-chromatid exchange (SCE) and micronucleus formation. Via intratracheal instillation, male CD rats (6/group) were dosed 3 times with BA, DBA, DBP or DBAC in a 24-h interval. Lung cells were enzymatically separated and used to determine the frequency of DNA adducts, SCE and micronuclei. Results show that all 4 test compounds induced DNA adducts, SCEs, and micronuclei in the rat-lung cell in vivo and that the postlabeling DNA adduct assay detected genotoxic activity at lower dose levels than the two cytogenetic assays. These findings suggest that BA, DBA, DBP or DBAC are rat pulmonary genotoxicants and the DNA-adduct assay is more sensitive than SCE or micronucleus assays for detecting the pulmonary genotoxicity of these industrial PAHs in the in vivo rat-lung-cell system.

Acridines↗
PubMed1994

Mutagenicity of coal-dust and smokeless-tobacco extracts in Salmonella typhimurium strains with differing levels of O-acetyltransferase activities.

Epidemiological studies have indicated an increased incidence of gastric neoplasia in coal miners. Because smokeless tobacco use is prevalent in the mining industry, nitrites or other components of these products may be etiologically associated with these gastric neoplasms. In this study both nitrosated and non-nitrosated coal-dust (from West Virginia and New Mexico) as well as smokeless-tobacco (snuff and chewing tobacco) extracts were examined for the presence of aromatic amines and nitroarenes by comparing the activities of these extracts in the pre-incubation variant of the Ames assay. Salmonella strains with differing O-acetyltransferase activities (TA98 and YG1024) were utilized in this investigation. The results of the examination of the coal-dust extracts indicated positive activity only in the nitrosated extracts. Both nitrosated extracts elicited an increased number of revertants (2-4-fold) on YG1024 without S9 in comparison to TA98, suggesting the presence of nitroarenes in these extracts. Additionally, the nitrosated West Virginia coal extract showed higher levels of activity on YG1024 with S9, indicating the possible presence of aromatic amines in this complex mixture. The non-nitrosated smokeless-tobacco extracts showed activity only on YG1024 in the presence of S9, with the highest amount of activity occurring in the snuff sample. Except for the chewing-tobacco extract on TA98 without S9, positive activity was found in both nitrosated tobacco extracts on YG1024 and TA98. As with the coal extracts, the presence of nitroarenes was inferred for these nitrosated materials. A comparative study of the non-nitrosated snuff extract across 5 tester strains with varying sensitivities to aromatic amines and nitroarenes (TA98NR, TA98/1,8-DNP6, TA98, YG1021 and YG1024) indicated that aromatic amines were a probable source of the mutagenic activity. The curing process and/or the addition of certain flavorants are potential sources of the mutagenic aromatic amines suggested to be present in the non-nitrosated snuff extract. These findings are consistent with an etiologic role supplementary to the nitroso compounds for mutagenic nitroarenes and aromatic amines in the development of gastric neoplasia in coal miners.

Acetyltransferases↗
PubMed1994

In vitro genotoxicity studies of chrysotile asbestos fibers dispersed in simulated pulmonary surfactant.

Micronucleus (MN) formation and sister-chromatid exchange (SCE) assays were performed for asbestos in cultured Chinese hamster lung (V79) cells to determine the effect of surfactant treatment on the genotoxicity of two chrysotile asbestos samples of different fiber lengths. The cells were challenged in vitro with NIEHS intermediate- and short-length chrysotile fibers in both their native state and with surfactant pretreatment. For the surfactant pretreatment, the fibers were incubated in a simulated pulmonary surfactant which was prepared by ultrasonically dispersing dipalmitoyl lecithin (DPL), a primary component of pulmonary surfactant, in minimal essential medium (MEM). Chrysotile asbestos was ultrasonically mixed into the prepared surfactant dispersion or into MEM. V79 cells were exposed to DPL-treated intermediate-length chrysotile (TICA), intermediate-length chrysotile (ICA), DPL-treated short-length chrysotile (TSCA) or short-length chrysotile (SCA) fibers for 48 h. For each treatment, 2000 mononucleated cells were scored for MN formation, and 30 M2 metaphase cells were scored for SCE induction. The results showed that all samples, TICA, ICA, TSCA and SCA, caused significant elevation in the frequency of cells with micronuclei and of cells with two or more nuclei. The increase in micronucleus frequency was greatest in cells challenged with untreated intermediate-length fibers, and was greater for untreated than for DPL-treated short-length fibers. For the short-length fiber samples, DPL surfactant treatment decreased activity for multiple nucleus formation, while DPL treatment did not result in consistent changes in that activity for intermediate-length fibers. Results of SCE assays were either negative or inconclusive. Cells were more viable following TICA and TSCA than following ICA and SCA challenge as measured by cell counts after 48 h of incubation.

Animals↗
PubMed1994

Mutagenicity of mild gasification products in Salmonella typhimurium.

Mild gasification is a coal-conversion technology that is currently under development in order to help meet future energy needs. 7 products from this process were assayed for mutagenic activity in the pre-incubation variant of the Salmonella assay (Ames test) using both DMSO and Tween 80 as sample solvents. Significant mutagenic activity was detected only in the wide-boiling-point composite materials, and the amount of this activity was found to be dependent on the solvent utilized. The highest number of revertants detected were on TA98 and its O-acetyltransferase over-producing derivative, YG1024, in the presence of the S9 microsomal fraction. Aromatic amines were suggested as a possible source of the mutagenic activity elicited. An examination of the liquid and tar phases of one composite material (MG-120) indicated that the mutagenic activity was restricted to the tar phase.

Coal↗
PubMed1994

Genotoxicity of vanadium pentoxide in Chinese hamster V79 cells.

Workers in many mining and manufacturing industries are potentially exposed to vanadium. Inhalation of dust containing vanadium pentoxide (V2O5), a pentavalent compound of vanadium, has been reported to cause lung diseases. Information related to the genotoxicity and potential carcinogenicity of V2O5, however, is still limited. In this study, the effect of V2O5 on mitosis, sister-chromatid exchange (SCE), micronucleus formation (MN), and gene mutation in Chinese hamster V79 cells was determined. Cells were treated with varying concentrations of V2O5 for 24 h. The results showed that no significant increases in the frequencies of SCE or gene mutation occurred in V2O5-treated cultures. However, dose-related increases were noted for micronucleated cells in cultures exposed to this compound, and the number of binucleated cells in the presence of cytochalasin B was found to decrease with increasing V2O5 concentrations. Since the micronucleated cells induced by V2O5 contained kinetochore-positive micronuclei, their induction appears to be due to damage to the spindle apparatus. These results indicate that V2O5 is cytotoxic and aneuploidogenic to V79 cells.

Aneuploidy↗
PubMed1993

Induction of sister chromatid exchange in spleen and bone marrow cells of rats exposed by inhalation to different dose rates of ethylene oxide.

We investigated the effects of dose rate on the frequency of sister chromatid exchange (SCE) in bone marrow and spleen cells of rats exposed to ethylene oxide (EtO). Four groups (18/group) of male Fischer 344 rats were exposed to EtO by inhalation. The exposures consisted of 100 ppm for 6 hr/day, 300 ppm for 2 hr/day, 600 ppm for 1 hr/day, and clean air control. All EtO treated rats were given a total exposure dose of 600 ppm.hr daily, 5 days/week for 3, 6, or 9 months. Six rats per group were sacrificed at each time point, and SCEs were measured in cultured spleen and bone marrow cells. A statistically significant increase was found in SCEs in both bone marrow and spleen cells for all treated groups and at each time point when compared to the control, except at the 3-month exposure for the middle and high dose-rate groups in bone marrow cells. In the spleen, the increases in SCEs were similar among the three experimental groups. In bone marrow, the lowest dose rate (100 ppm) resulted in higher SCE frequencies than the medium and high dose-rate group after 3 and 6 month exposures. The overall frequencies of SCEs in the spleen cells were higher than in the bone marrow cells. The increase in SCE frequencies and decrease in the replicative index in spleen cells were also dependent on the duration of exposure. These results indicate that (1) EtO, by inhalation, can cause SCEs both in spleen and bone marrow cells of Fischer 344 rats, (2) spleen cells are more sensitive to EtO than bone marrow cells, and (3) in bone marrow cells the lowest dose-rate (longest) exposure causes more SCEs than the highest dose-rate (shortest) exposures.

Administration, Inhalation↗
PubMed1993

Is CD8 dependence a true reflection of TCR affinity for antigen?

Cytotoxic T lymphocytes (CTL) are generally specific for class I MHC proteins plus antigen and express CD8 co-receptor molecules. The effector function of some CTL can be blocked by antibodies to CD8 (CD8 dependent CTL), whereas that of others is resistant to blocking (CD8 independent CTL). This difference in sensitivity to antibody-mediated inhibition is assumed to reflect variations in affinity of particular TCR for antigen. However, we have found that a major difference between CD8 independent and CD8 dependent T cells lies in their sensitivity to stimulation, the former responding to lower concentrations of anti-CD3 antibody than the latter. Thus the contribution to cell signalling provided by the co-association of p56lck and CD8 is particularly relevant for CD8 dependent cells. These data challenge the notion that the affinity of an individual TCR for antigen is related to the sensitivity of a cell to inhibition by anti-CD8 antibodies. Furthermore we show that antibodies to co-receptor molecules have multiple distinct effects on T cell activation, only some of which may be related to T cell affinity.

Antigens↗
PubMed1992

Cytogenetic effects of vincristine sulfate and ethylene dibromide in human peripheral lymphocytes: micronucleus analysis.

Micronuclei kinetics and persistence in mononucleated and binucleated human peripheral lymphocytes following short-term (4 hr) and continuous (until harvest) in vitro exposure to vincristine sulfate (VS) and ethylene dibromide (EDB) were studied. Lymphocytes were exposed to chemicals for various doses and harvested at different culture times. Micronucleus frequencies were scored in both mononucleated and binucleated cells on the same slide. VS-treated cells showed a significantly higher incidence of micronucleus in both mononucleated and binucleated cells than controls (P less than 0.01). The cells treated continuously with VS produced comparatively higher frequencies of micronucleated cells than those treated for 4 hr. Highest micronuclei frequencies were observed 24 hr after chemical treatment in both mononucleated and binucleated cells and decreased later with time. However, the micronucleus frequencies remained significantly higher than the controls even in the cells harvested at 144 hr. VS induced a large number of micronucleated cells with multiple micronuclei. VS also caused a severe decrease in nuclear division due to cytotoxic effect. Lymphocytes treated with EDB for 4 hr and continuously showed a statistically higher incidence of micronuclei in binucleated cells compared to the controls (P less than 0.05), whereas in mononucleated cells higher micronucleus frequencies were observed only in cultures treated continuously. Continuous presence of EDB induced both dose- and time-dependent increase of micronuclei in both mono- and binucleated cells (P less than 0.05). EDB induced relatively few multiple micronucleated cells in comparison with VS. EDB did not affect nuclear divisions even with continuous treatment. High micronucleus frequencies observed at 144 hr harvest following 4 hr treatment of both EDB and VS suggest the persistence of DNA damage in cells. These studies suggest that micronuclei kinetics in human peripheral lymphocytes depends on the genotoxic potentially and cytotoxicity of a genotoxicant.

Cell Division↗
PubMed1992

Transplacental genotoxicity of triethylenemelamine, benzene, and vinblastine in mice.

Transplacental cytogenetic effects of triethylenemelamine (TEM), benzene, and vinblastine on maternal mice and their fetuses have been investigated using micronucleus and sister chromatid exchange (SCE) as genetic endpoints. CD-1 mice were treated on day 14 and 15 of gestation with TEM (0.125, 0.25, and 0.5 mg/kg), benzene (439,878, and 1,318 mg/kg), and vinblastine (0.5, 1, and 2 mg/kg) by intraperitoneal injection at 24 hr intervals, and sacrificed 40 hr after the first injection. Erythrocytic precursor cells in maternal bone marrow and fetal livers (2-4) from each pregnant mouse were used for the micronucleus and/or the SCE analyses. Significant dose-related increases in both micronuclei and SCE were found in maternal bone marrow and fetal liver following TEM treatment. Benzene at the highest dose (1,318 mg/kg) also caused a significant increase in micronuclei and SCE in both maternal bone marrow and fetal liver cells. The embryonic genotoxic effect of TEM was much higher than that of benzene for both genetic endpoints, and the frequency of micronuclei induced by benzene was higher in fetal liver than in maternal bone marrow cells. Vinblastine, a spindle poison, induced micronuclei but not SCE. Micronuclei induction by vinblastine was 7 fold greater in maternal bone marrow than in fetal liver cells. All three chemicals were cytotoxic in maternal bone marrow cells, but not in fetal liver cells except for TEM, which showed a weak cytotoxicity in fetal liver cells in the micronucleus assay. These results indicate that TEM, benzene, and vinblastine are transplacental genotoxicants in mice.

Animals↗
PubMed1992

Comparison of DNA adduct detection between two enhancement methods of the 32P-postlabelling assay in rat lung cells.

32P-Postlabeling analysis is a useful assay system for detecting the covalent binding of mutagens and/or carcinogens to DNA. The detection ability of this system has been tremendously enhanced by the incorporation of butanol extraction or nuclease P1 treatment into the experimental protocol. In this study, the sensitivity of adduct detection between these two enhancement methods was compared in vivo or in vitro with 2-aminoanthracene (2AA), 2,4,7-trinitro-9-fluorenone (TNF), and nitrosated coal dust extract (NCDE) using the lung cells of rats. For the in vivo assay, male CD rats were dosed 3 times via intratracheal instillation, whereas for the in vitro study, rat lungs cut into small pieces were treated with test substances for 16 h without exogenous activation. Although, under the conditions tested, both the butanol and the nuclease P1 methods detected DNA adducts caused by all 3 test agents in rat lung cells in vivo or in vitro, a higher adduct detecting ability was found with the butanol enhancement for 2AA and TNF, and with the nuclease P1 enhancement for NCDE. The results suggest that overall the butanol enhancement method is a more sensitive protocol. However, for detecting unknown adduct-forming chemicals, especially when they are present in complex mixtures, both enhancement methods may have to be used.

Animals↗
PubMed1992

Clastogenic and aneuploidogenic effects of cigarette smoke condensate, mitomycin C and vincristine sulfate.

Immunofluorescent staining of kinetochores in micronuclei (MN) of cytochalasin-B-blocked cells was used to distinguish between clastogenic and aneuploidogenic effects of cigarette smoke condensate (CSC), mitomycin C (MMC) and vincristine sulfate (VS) in Chinese hamster lung V79 cells by using an anti-kinetochore antibody. Within the base-line micronucleated cells (2%), 50 to 58% contained kinetochore-positive (KC+) MN. MMC induced a significantly higher number of MN compared to the controls (P < 0.01), and the majority of micronucleated cells (77% at 0.08 microgram/ml) contained kinetochore-negative (KC-)MN. In contrast, VS induced a large number of MN (P < 0.01) but most of the micronucleated cells contained KC+ MN (93% at 0.08 microgram/ml). Cigarette smoke condensate (CSC) induced both KC+ (P < 0.01) and KC-(P < 0.05) MN suggesting the presence of both clastogenic and aneuploidogenic agents. However, the higher frequency of KC+ than KC- micronucleated cells suggests a stronger aneuploidogenic effect of CSC.

Aneuploidy↗
PubMed1991

Genotoxicity of diesel-exhaust particles dispersed in simulated pulmonary surfactant.

Diesel-exhaust particles from two sources were dispersed in aqueous mixtures of dipalmitoyl phosphatidyl choline, a major component of pulmonary surfactant, and were tested for genotoxicity. Diesel samples from the same sources were extracted with dichloromethane and transferred into dimethyl sulfoxide and subjected to the same assays. Both types of extractions yielded similar results in both the Salmonella mutagenicity assay and the sister-chromatid exchange assay using V79 cells. After separation of the samples into supernatant and sediment fractions, the activity of both diesel samples was shown to reside exclusively in the supernatant fraction for the solvent-extracted samples, and exclusively in the sedimented fraction for surfactant dispersed samples. These findings indicate that genotoxic activity associated with diesel particles inhaled into the lung may be made bioavailable by virtue of the solubilization/dispersion properties of pulmonary surfactant components.

Air Pollutants↗
PubMed1991

Studies on three structurally related phenylenediamines with the mouse micronucleus assay system.

Three structurally related compounds, 4-chloro-o-phenylenediamine (COP), 4-nitro-o-phenylenediamine (NOP) and p-phenylenediamine dihydrochloride (PPD), are used in fur dyes, inks and hair coloring formulations. COP has been reported to be carcinogenic in both rats and mice. NOP and PPD are non-carcinogens, but have consistently tested positive in short-term in vitro genotoxicity assays. Studies were undertaken to evaluate their genotoxicity with the in vivo mouse bone-marrow micronucleus assay. Five CD-1 male mice per dose were injected i.p. with the compounds and sacrificed at intervals of 24, 48 and 72 h. 2000 cells were scored per animal to determine the frequency of micronucleated-polychromatic erythrocytes (MPCE). COP induced significant dose-related increases in MPCE over the 3 doses tested at each of the sampling intervals. The peak response occurred at 24 h. No response was observed in animals treated with PPD or NOP.

Animals↗
PubMed1991

Characterization of the in vitro unscheduled DNA synthesis assay in primary lung cells of the rat.

The in vitro unscheduled DNA synthesis (UDS) assay has been evaluated in rat primary lung cells with known genotoxicants. The autoradiographic method was employed to detect UDS in both alveolar macrophages and primary pulmonary cells. Data of a time course study revealed that a high radioactive labeling of DNA repair was achieved after a 16-h incubation with [3H]thymidine. Coupled with low serum (1%), hydroxyurea at the concentration of 20 mM inhibited regular DNA synthesis in primary lung cells in a satisfactory manner (81-88% inhibition). With this protocol, a dose-related increase in UDS was induced by N-methyl-N'-nitro-N-nitrosoguanidine and 2-aminoanthracene in both rat alveolar macrophages and primary lung cells. The results suggest that primary rat lung cells in culture possess DNA-repair ability and that the UDS assay may be useful for assessing the pulmonary genotoxic effect of chemicals in this cell system.

Animals↗
PubMed1990

Micronuclei assay in cytokinesis-blocked binucleated and conventional mononucleated methods in human peripheral lymphocytes.

Studies were performed to determine the genotoxic effect of cytochalasin-B (CYB) and to compare the efficacy of the cytokinesis-blocked binucleated cells (CB) for scoring micronuclei (MN) with the conventional mononuclear method, following treatment with mitomycin C and cyclophosphamide. The results show that 3-4 micrograms/ml of CYB induced maximum number of binucleated cells without any genotoxic effect and the frequency of MN in binucleated cells was higher than that in the mononucleated cells (P less than 0.05) but less than twofold. However, MN frequencies in binucleated cells were not equivalent to the frequencies of mononucleated cells, since MN in binucleated cells represent two nuclei. These results suggest that further study is required to consider CB method as a more reliable approach for scoring MN.

Adult↗
PubMed1990

Induction of morphological transformation by coal-dust extract in BALB/3T3 A31-1-13 cell line.

The transforming activity of coal dust extracts was studied using BALB/3T3 clone A31-1-13 cells. Coal-dust extracts, both nitrosated and nonnitrosated, induced cell transformation in a dose-response manner. However, the transformation frequency was higher with the nitrosated than with the nonnitrosated extract. All transformed cell lines derived from coal-dust extract-induced foci showed biological characteristics of neoplastic transformation such as loss of contact inhibition and anchorage-independent growth. These results appear to support a hypothesis of coal mine dust causation of gastric cancer in coal miners.

Animals↗
PubMed1990

Use of rat primary lung cells for studying genotoxicity with the sister-chromatid exchange and micronucleus assays.

Primary culture of lung cells from CD rats was established for pulmonary genotoxicity studies using two genetic endpoints, sister-chromatid exchange (SCE) and micronucleus formation (MN). In the cell isolation study, a combined enzyme separation of rat lungs with trypsin (1.3 mg/ml) plus collagenase (50 U/ml) gave the highest yield of viable and colony-forming cells. For the MN assay, the cytokinesis block induced by cytochalasin B (CYB) was employed to enumerate MN in binucleated (BN) cells. Treatment of primary lung cells with 2 micrograms CYB/ml for two days appeared to be optimal for scoring micronuclei in CYB-induced BN cells. By this procedure, mitomycin C (MMC), triethylenemelamine, and benzo[a]pyrene caused a dose-related increase in micronucleated BN cells in vitro without metabolic activation. In the SCE assay, maximum second-division metaphases were obtained after cells were incubated with bromodeoxyuridine for 48-54 h. After this incubation time, high frequencies of SCE induced by MMC and 3-methylcholanthrene after in vitro exposure (without S9 activation) or in vivo exposure were observed. The results indicate that rat primary lung cells can metabolize polycyclic aromatic hydrocarbons and that this lung cell system is potentially useful for the detection of pulmonary genotoxicants.

Animals↗