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Biomedical subjects

M S Legator

Publications and source records attributed to M S Legator.

At least 55 records · Page 3Linked to original sources
PubMed1989

Genotoxic effects of fly ash in bacteria, mammalian cells and animals.

The increasing use of fossil fuels has raised concerns about possible deleterious health effects of the final combustion product, fly ash. Seven ash samples from coal sources obtained from Battelle Columbus Laboratories were evaluated in the Salmonella/mammalian microsome mutagenicity assay to determine their mutagenic potential. While dimethyl sulfoxide extracts of five samples showed no mutagenicity, sample 102 caused an increase in the number of revertants per plate over controls in TA100 and TA98 with activation by liver homogenate (2-fold and 2.4-fold, respectively), and without (2-fold and 6-fold). This ash was thus evaluated in whole animal studies. Animals treated by inhalation or oral gavage were assayed for the presence of mutagens in the urine, micronuclei in polychromatic erythrocytes, and chromosomal aberrations in metaphase bone marrow cells. Those animals treated by inhalation were also examined for local damage in the lung. The assay for mutagens in the urine was negative as shown by the Ames assay with TA100 and TA98 and there was no increase in micronuclei or in metaphase aberrations. Histological sections from the animals treated by inhalation did not show the presence of particles, macrophage infiltrations and generalized lung damage. We tested the same fly ash with an in vitro cell transformation assay with the cell line Balb/c 3T3 subclone A31-1-13. Although there was not an increase in Type III foci, there was a dose-dependent increase of Type II foci in the treated cells over the controls. In one assay, there was approximately a 14-fold increase in Type II foci in the highest dose (2 mg/ml) compared to the solvent control. One other ash sample induced cell transformation without being markedly cytotoxic, while a third sample was highly toxic but did not induce transformation.

Animals↗
PubMed1989

The effect of 3-aminobenzamide on X-ray induction of chromosome aberrations in Down syndrome lymphocytes.

Human lymphocytes from normal and Down syndrome (DS) subjects were examined to determine the effect of 3-aminobenzamide (3AB) on X-ray-induced chromosome aberrations. Lymphocytes were treated with 150 or 300 rad of X-rays in the presence of 3 mM 3AB for various times after irradiation, and then the cells were analyzed for the presence of chromosome aberrations in mitotic cells. 3-Aminobenzamide had no effect on the frequency of chromosome aberrations produced by X-rays in G0 lymphocytes from normal subjects. In contrast, lymphocytes from DS patients displayed an increase in the frequency of chromosome aberrations as a result of treatment with X-rays in the presence of 3AB. These observations indicate that DS lymphocytes are more sensitive to the inhibition of poly(ADP)ribose synthetase than normal lymphocytes.

Benzamides↗
PubMed1989

Enhancement of benzene clastogenicity by praziquantel in mice.

Praziquantel (PQ) is a commonly used drug to treat patients with schistosomiasis. Previous studies using cells in vitro have shown that PQ can enhance the mutagenic activities of known mutagens. We have conducted a cytogenetic - urine metabolite study to determine the in vivo clastogenic and co-clastogenic potential of PQ with a ubiquitous environmental contaminant, benzene (BZ). 16 groups of adult male ICR mice (5 animals per group) were used. They were negative control, solvent controls (cremophore E1 3%, olive oil and combined), positive control (BZ 440 mg/kg b.w.) and 11 exposed groups. To test for clastogenicity of PQ, mice were treated orally with 100, 400, 800 and 1200 mg/kg b.w. PQ and sacrificed 30 h later for determination of micronuclei (MN) frequency in bone-marrow polychromatic erythrocytes (PCE). None of these PQ does induced an increase of MN frequency. On the other hand, BZ induced, as expected, a high frequency of MN (46.4 +/- 6.34/1000 PCE). The enhancement effect of PQ was tested in 7 groups of mice using 3 different protocols. Mice were treated with 440 mg/kg b.w. BZ and 1 h later with 0, 100, 200, 400, 800 and 1200 mg/kg b.w. PZ. In another group, 800 mg/kg PQ was administered at 3 h after BZ exposure. In the last group, PQ (800 mg/kg) was administered at 1 h prior to BZ exposure. Results from the first combined exposure group showed a significant PQ dose-dependent increase in the frequency of MN in PCE (p less than 0.05). The increase with the two high doses of praziquantel is significantly higher (p less than 0.05) than the MN frequencies in the benzene control and the expected value based on the additive effects of the two agents. Studies with other combined treatment groups showed that the induction of MN was highest when PQ was administered at 1 h before BZ exposure. Moreover, the presence of BZ metabolites (muconic acid, phenol, catechol and hydroquinone) in urine was studied in 6 of the combined treatment groups. This metabolite study revealed that PQ enhanced the metabolism of BZ towards the pathway to form muconaldehyde which is converted to muconic acid in urine. In conclusion, our study showed that PQ is not a clastogen but can enhance the clastogenic activity of BZ in vivo by shifting the metabolic pathways of BZ towards formation of muconaldehyde which may be responsible for the enhancement effect.

Animals↗
PubMed1989

Effect of dimethyl sulfoxide on the genotoxicity and metabolism of benzene in vivo.

The mechanism of the genotoxicity and metabolism of benzene (BZ) was investigated by using a free-radical scavenger, dimethyl sulfoxide (DMSO), to investigate the free radical mechanism in BZ metabolism. The presence of chromosomal breakage expressed as micronuclei (MN) in bone marrow polychromatic erythrocytes (PCE) and the presence of several BZ metabolites in the urine were monitored. Adult male ICR mice were exposed orally to DMSO after oral exposure to BZ (440 mg/kg b.w.). DMSO was administered either in different concentrations (1.25, 3.75 or 12.5% given at a volume of 0.01 ml/gm b.w.) or at different intervals after BZ exposure (1, 3 or 5 h). Each group consisted of five mice. It was found that the BZ-induced MN frequency was reduced by DMSO from 48.8 +/- 5.6 (SEM) to 2.6 +/- 0.7 per 1000 PCE when DMSO (12.5%) was administered at 1 h after BZ exposure (P less than 0.01), to 3.4 +/- 0.8 at 3 h (P less than 0.01) and to 36.2 +/- 12.1 at 5 h (P less than 0.01). The reduction of the clastogenic effect of BZ by DMSO was also dependent upon the DMSO doses. The MN frequency was significantly reduced from 48.8 +/- 5.6 to 29.4 +/- 10.9 with 1.25% DMSO (P less than 0.01) to 20 +/- 7.6 with 3.75% (P less than 0.01) and to 2.6 +/- 0.7 with 12.5% DMSO (P less than 0.01). The presence of different metabolites of BZ such as hydroquinone, catechol, trans-trans muconic acid (MA, the oxidized form of trans-trans muconaldehyde, ttM), and total and conjugated phenol was evaluated in the urine of the exposed mice using HPLC. Among these metabolites, the quantity of MA was found to have the closest positive correlation with the MN frequency (P less than 0.007). Phenol but not the other monitored metabolites was also positively correlated with MN frequency (P less than 0.03). Thus, our data show that the formation of genotoxic metabolites from BZ probably involves hydroxyl radicals and ttM as well as phenol are likely to be responsible for the clastogenic effect of benzene in vivo.

Aldehydes↗
PubMed1989

Aromatic amines and acetamides in Salmonella typhimurium TA98 and TA100: a quantitative structure-activity relation study.

The mutagenicity of a series of 19 aromatic amines had been previously measured in Salmonella typhimurium strains TA98 (frame-shift) and TA100 (base-pair) with the addition of S9 from Aroclor 1254-induced rat liver. A quantitative structure-activity relation (QSAR) study using multiple regression analysis points out the influence of three factors on mutagenicity: lipophilic character, position of the amine group, and whether it is free or acetylated, as expressed by log P and two indicator variables I1 and I2, respectively. The multiple regression equations explain 78 and 88% of the variance in log mutagenicity in TA98 and TA100, respectively. First of all, mutagenicity was shown to increase with lipophilicity. On the other hand, mutagenicity is reduced when the amine or acetamido position is ortho to the juncture because of steric hindrance in its biotransformation compared with a non-ortho isomer. It is decreased also by the acetylation of the amine group, probably because the acetyl group needs to be first split off prior to oxidation of the amine group to -NHOH.

Acetamides↗
PubMed1988

Persistence of micronuclei in peripheral blood normochromatic erythrocytes of subchronically benzene-treated male mice.

The kinetics of micronucleus (MN) induction and decline in blood normochromatic erythrocytes (NCE) of mice subchronically exposed to benzene was investigated during and after exposure. Swiss (ICR) male mice (10/group) were given 0.0, 36.6, 73.2, and 146.4 mg/kg body weight benzene by gavage daily for 14 days, except for days 5 and 10. The frequency of MN increased significantly (P less than .001) during benzene treatment as a function of both concentration and time. Eleven days after exposure the levels of MN were higher than those observed at the end of exposure. After an initial rapid decline in the frequency of MN from 11 to 18 days postexposure, the decline became linear with time through 60 days postexposure. Using linear regression analysis, the MN level in each treatment group was predicted to reach control levels by approximately 85 days post-treatment. Dose-dependent suppression and recovery of erythropoiesis, estimated by polychromatic erythrocyte frequency, were observed in the 1st and 2nd weeks of exposure, respectively. Red blood cell (RBC) production was markedly increased in the first 3 weeks after benzene treatment. At later times the rate of production of the RBC returned to normal and may account for the linear decline observed in MN frequency. This research indicates that the frequency of MN is dose and duration dependent, while the decline in MN frequency after the end of benzene exposure can be related to changes in the kinetics of erythropoiesis.

Analysis of Variance↗
PubMed1988

Induction of chromosome aberrations and mitotic arrest by cytomegalovirus in human cells.

Human cytomegalovirus (CMV) is potentially an effective but often overlooked genotoxic agent in humans. We report here evidence that indicates that infection by CMV can induce chromosome alterations and mitotic inhibition. The frequency of chromosome aberrations induced was dependent on the input multiplicity of infection (m.o.i.) for human lung fibroblasts (LU), but not for human peripheral blood lymphocytes (PBLs) when both cell types were infected at the GO phase of the cell cycle. The aberrations induced by CMV were mostly chromatid breaks and chromosome pulverizations that resembled prematurely condensed S-phase chromatin. Pulverized chromosomes were not observed in LU cells infected with virus stocks that had been rendered nonlytic by UV-irradiation at 24,000 ergs/mm2 or from infection of human lymphocytes. In LU cells infected with UV-irradiated CMV, the frequency of aberrations induced was inversely dependent on the extent of the exposure of the CMV stock to the UV-light. In permissive CMV infection of proliferating LU cells at 24 hr after subculture, a high percentage (greater than 40%) of the metaphase cells were arrested at their first metaphase and displayed severely condensed chromosomes when harvested 48 hr later. A significant increase (p less than 0.05) in the chromosome aberration frequency was also observed. Our study shows that CMV infection is genotoxic to host cells. The types and extent of damage are dependent on the viral genome expression and on the cell cycle stage of the cells at the time of infection. The possible mechanisms for induction of chromosome damage by CMV are discussed.

Cell Division↗
PubMed1988

Chromosomal radiosensitivity of Down syndrome lymphocytes at different stages of the cell cycle.

Down syndrome (DS) is one of the most common types of congenital anomalies. In addition to a wide spectrum of developmental abnormalities, DS patients are also highly sensitive to the induction of chromosomal aberrations when their GO lymphocytes are exposed to ionizing radiation. We conducted the present study to evaluate the effect of X-rays on proliferating lymphocytes from DS and normal individuals. We found that DS lymphocytes were significantly more sensitive to X-ray induction of chromosome aberrations than normal cells, when they were irradiated at the G0, G1 and S phases of the cell cycle. The S phase was the most radiosensitive phase and would lead to extensive cell killing, whereas the G1 phase seemed to be more prone to the induction of chromosome rearrangements that would potentially lead to serious long-term consequences.

Cell Cycle↗
PubMed1988

Biological effects in a chemical factory with mutagenic exposure. I. Cytogenetic and haematological parameters.

Analysis in two independent laboratories demonstrated no significant differences in chromosome aberrations or micronuclei in lymphocytes from peripheral blood between workers in a chemical factory (exposed to a mixture of chemicals, such as piperazine, low levels of ethylene oxide and formaldehyde, aromatic nitrogen compounds, and other aromatic compounds) compared to unexposed control subjects. The chemical workers had significantly higher counts of lymphocytes (3.57 vs. 2.82 X 10(9)/l; P less than 0.001), eosinophils (0.27 vs. 0.20 X 10(9)/l; P = 0.005), and basophils (0.06 vs. 0.05 X 10(9)/l; P = 0.01) than the controls. Twenty workers exposed to piperazine had higher total numbers of B-lymphocytes than control subjects.

Adult↗
PubMed1988

Genotoxic effects of a sub-acute low-level inhalation exposure to a mixture of carcinogenic chemicals.

A study was conducted using a combined testing protocol (CTP), to determine whether short-term biological end-points, singly or in combination, are sufficiently sensitive to identify damage induced by exposure to ambient levels of industrial chemicals. A small-scale inhalation set-up which is both economical and easy to assemble was designed. Mice were exposed to 4 concentrations of a custom-blend mixture of benzene, chloroprene, epichlorohydrin and xylene in a ratio of 2:2:1:2, respectively. The concentrations for benzene, chloroprene and xylene were 0, 0.1, 1.0 and 10 ppm each. Concentrations for epichlorohydrin were half those for the other components. Groups of 22 males and 22 female mice were exposed to each concentration of the mixture for 3 and 6 weeks. Selected biological end-points including urine mutagenesis, bone marrow cell aberrations and micronuclei, spleen lymphocyte aberrations and liver enzyme induction were monitored. The spleen lymphocyte aberrations and liver enzyme induction were the most sensitive end-points. The lymphocytes showed a significant induction of chromosome aberrations from exposure for 3 weeks to all 3 concentrations of the mixtures. After 6 weeks of exposure, significant induction of aberrations was observed after exposure to low and medium concentrations but not to the high concentration. This lack of response at the high concentration after 6 weeks exposure, appeared to correlate with a significant induction of glutathione S-transferase in the liver. Since this enzyme is known to detoxify 3 of the 4 chemicals in our mixture, it may indicate a detoxification mechanism after enzyme induction. The present study indicates that the CTP is sufficiently sensitive to identify toxicological effects after exposure to ambient levels of a gas mixture.

Administration, Inhalation↗
PubMed1988

Elevated frequencies of 6-thioguanine-resistant lymphocytes in multiple sclerosis patients treated with cyclophosphamide: a prospective study.

An autoradiographic assay for 6-thioguanine-resistant (TGr) lymphocytes was used to determine the frequency of in vivo derived variant T lymphocytes in peripheral blood from multiple sclerosis (MS) patients treated with monthly intravenous infusions of 750 mg/m2 of cyclophosphamide (CP). To analyze the time-course of response to CP, the MS patients were studied prospectively. Samples were obtained from the patients before the beginning of CP therapy, 4-5 times during the course of treatment, and, finally, 2 or 3 months after the completion of therapy. 2 weeks after the first CP infusion, the variant frequencies (Vfs) of the MS patients were significantly increased (p less than 0.05) above their pre-treatment values, but by 4 weeks following the first CP infusion the Vfs had fallen to normal or near-normal levels. After subsequent treatments, the frequencies of variant TGr cells were again higher than pre-treatment Vfs. However, within 7-13 weeks after the cessation of CP therapy, the Vfs of all subjects had returned to normal levels. The transient nature of the response indicates rapid in vivo selection against CP-induced TGr mutant cells. The mean pre-treatment Vf of the 4 MS patients who were cigarette smokers was 6.56 X 10(-6) which was significantly greater (p less than 0.05) than the mean Vf (1.52 X 10(-6) of the 4 MS patients who were non-smokers. The mean Vf from 8 assays of healthy non-smokers was 1.92 X 10(-6).

Autoradiography↗
PubMed1988

Development of a rodent lung macrophage chromosome aberration assay.

Lung macrophages are the first line of defense against inhaled xenobiotics. They are able to accumulate airborne particulates as well as having metabolic capability. They may thus be sensitive indicator cells for detecting inhalation exposure to environmental mutagens. Their usefulness as a short-term in vivo genotoxic assay has not, however, been adequately explored. We have systematically investigated the feasibility of developing a lung macrophage chromosome-aberration assay. It was found that with different types of spindle-binding chemicals (vinblastine and vincristine), and with improved harvesting procedures, an adequate number of metaphase cells can be collected from mice and Chinese hamsters. The chromosome aberration frequencies in macrophages from control mice and Chinese hamsters were found to be 1.2 +/- 2.3 and 0.75 +/- 2.2 per 100 cells respectively. These frequencies are within normal ranges for other somatic cells. After inhalation exposure to an occupational-exposure level of benzene (0, 0.1 and 1 ppm), significant dose-dependent induction of aberrations (1.2 +/- 2.3, 5.7 +/- 6.3 and 6.8 +/- 6.2 chromatid deletions per 100 cells resp.) were observed in the macrophages. Thus, these cells can be used as one of a battery of in vivo assays for inhalation exposure studies.

Animals↗
PubMed1988

Fluorescent body distribution in spermatozoa in the male with exclusively female offspring.

Fluorescent (F) body distribution was determined in a group of men who did not have a fertility problem, but rather had fathered exclusively female offspring. The study was designed to analyze spermatozoa for the frequency of zero F-body (X-bearing) and one F-body (Y-bearing) spermatozoa. Semen samples were separated (processed) for Y-bearing spermatozoa enrichment and reanalyzed for fluorescent body distribution. The study consisted of 50 control (10 males) samples (unprocessed), 35 preseparation (35 patients) samples (unprocessed), and 18 postseparation (18 patients) samples (processed). A significantly higher frequency (P less than 0.05) of zero F-body spermatozoa were observed in the preseparation samples when compared with the control samples. The presence of more spermatozoa without fluorescent body correlates with the occurrence of more female births.

Fathers↗
PubMed1987

Pyridine prevents the clastogenicity of benzene but not of benzo[a]pyrene or cyclophosphamide.

Pyridine has been shown to be a much more potent inhibitor than other solvents of the metabolism and therefore the clastogenicity of benzene. In this report, pyridine prevented benzene-derived micronucleus formation in the bone marrow of ICR Swiss mice at much lower levels than xylene did. Time-course experiments did not indicate any delay in the peak micronucleus response to benzene caused by either pyridine or xylene. Similar experiments using pyridine with benzo[a]pyrene and pyridine with cyclophosphamide indicated that the effect of pyridine was specific for benzene. Benzo[a]pyrene (150 mg/kg) was inhibited by pyridine only at levels of 100 mg/kg or more, compared to inhibition of benzene (440 or 880 mg/kg) by pyridine at levels of 5 mg/kg. Cyclophosphamide was not inhibited at any level, and micronucleus formation was increased at lower ratios of pyridine to cyclophosphamide. These results provide indirect conformation of the work by others indicating that benzene is activated in part by a cytochrome P450 isozyme different from those activating benzo[a] pyrene or cyclophosphamide. Since DBA/2 mice (AHH-non-inducible) are more sensitive to benzene than C57Bl/6 mice (AHH-inducible), single and multiple treatments with benzene were compared by micronucleus response in these two strains. DBA mice were more responsive in all cases. Pretreatment with methylcholanthrene caused a greater response to benzene in DBA/2 mice, suggesting that the cytochrome P450 isozyme involved is one of the forms induced by methylcholanthrene independent of the high-affinity Ah receptor. It is hypothesized that more efficient activation of benzene by the unique cytochrome P450 isozyme, perhaps combined with relatively less conjugation, may result in a greater sensitivity of the bone marrow versus the liver, and of DBA/2 versus C57Bl/6 mice.

Animals↗
PubMed1987

Induction of chromosome aberrations in lymphocytes of mice after subchronic exposure to benzene.

The induction of chromosome aberrations in lymphocytes of mice after subchronic exposure to benzene was investigated. 4 groups of 5 Swiss (ICR) male mice were given orally a solution of benzene every day for 14 days except days 5 and 10. The daily doses were 0, 36.6, 73.2 and 146.4 mg/kg. Mice were sacrificed on day 15, lymphocytes were obtained by perfusion of the spleen and the cells were cultured in RPMI 1640 medium. After 48 h of culture, cells were harvested for cytogenetic analysis. A significant dose-dependent increase in the frequency of cells with chromatid aberrations were found (p less than 0.001). A significant increase in polyploid cells were also observed (p less than or equal to 0.05). This study represents the first report on the induction of chromosome aberrations and polyploid cells in lymphocytes of mice after subchronic exposure to benzene. Such dual activity of benzene suggests that benzene may be responsible for more human health problems than currently estimated.

Animals↗
PubMed1987

Cyclophosphamide: effects of paternal exposure on the brain chemistry of the F1 progeny.

The effects of acute and chronic cyclophosphamide (CP) exposure to male rats on several neurotransmitter enzymes have been examined in various brain regions of the F1 progeny at 90 d old. The acute postmeiotic CP exposure to male rats induced significant biphasic changes in the choline acetyltransferase (ChAT) activity in various brain regions of F1 progeny; significant decreases in the cerebellar acetylcholinesterase (AChE) activity of the male (47%) and the female (14%) F1 progeny, and moderate decrease (26%) in the hippocampal AChE activity in the female F1 progeny; and a moderate increase (29%) in the temporo-cortical glutamic acid decarboxylase (GAD) activity of the female F1 rats. The chronic CP-exposed male rats resulted in a slight but significant decrease (16%) in the temporo-cortical ChAT activity in the female F1 progeny; a marked increase (51%) in the hypothalamic AChE activity in the male F1 progeny; and a marked decrease (32%) in cerebellar GAD activity and a slight increase (13%) in the striatal GAD activity in the female F1 progeny. These enzymatic changes in the adult brain of F1 progeny of CP-treated males may be associated with the behavioral abnormalities observed previously. Results suggest that these neurochemical parameters may be useful markers for analysis of the potential neurotoxicity of CP.

Acetylcholinesterase↗