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H Norppa

Publications and source records attributed to H Norppa.

17 recordsLinked to original sources
PubMed1992

Sister-chromatid exchanges induced by vinyl esters and respective carboxylic acids in cultured human lymphocytes.

Vinyl acetate--an efficient inducer of sister-chromatid exchanges (SCEs)--is known to be hydrolyzed in mammalian cells into acetic acid and acetaldehyde, the latter being the likely metabolite responsible for the SCE induction. As similar hydrolysis to acetaldehyde and to a carboxylic acid is also expected for other vinyl esters, five such compounds--vinyl formate, vinyl chloroformate, vinyl propionate, vinyl crotonate and vinyl-2-ethylhexanoate--and five carboxylic acids--formic acid, acetic acid, propionic acid, crotonic acid and 2-ethylhexanoic acid--were tested for their ability to induce SCEs in cultured (72 h) human lymphocytes with a 48-h treatment, starting at 24 h after culture initiation. Vinyl formate, vinyl propionate and vinyl crotonate induced a clear dose-dependent increase in the number of SCEs/cell at concentrations of 0.125-0.5 mM and vinyl chloroformate at 0.063-1 mM, i.e., at roughly the same concentration range as vinyl acetate and acetaldehyde. Vinyl-2-ethylhexanoate required slightly higher concentrations (0.25-4 mM) for SCE induction. All of the carboxylic acids tested also elevated SCEs, but only slightly. Formic acid and crotonic acid produced some SCE increase at a concentration of 10 mM, acetic acid at 5 and 10 mM and propionic acid at 2.5 mM. 2-Ethylhexanoic acid induced SCEs at a lower concentration range (0.63-2.5 mM) than the other acids. The positive concentrations of the first three carboxylic acids lowered the pH of the culture medium immediately after the treatment by 0.5-1.0 pH unit (lowest observed pH 6.53). The pH differences from the control cultures became smaller in measurements done 24 h and 48 h after the beginning of treatment. Propionic acid and 2-ethylhexanoic acid affected medium pH only slightly (maximum drop 0.2 pH units) at the concentrations that induced SCEs. The results lend support to the idea that the efficient SCE induction observed with the vinyl esters results from the formation of acetaldehyde, with carboxylic acids--with the possible exception of 2-ethylhexanoic acid--playing no significant role. The slight SCE induction obtained with the carboxylic acids cannot be explained by lowered pH alone.

Carboxylic Acids↗
PubMed1992

Induction of sister-chromatid exchanges by 2-aminofluorene in cultured human lymphocytes with and without erythrocytes.

2-Aminofluorene (2-AF), an indirect mutagen reported to be metabolically activated by erythrocytes in the Salmonella mutagenicity test, was studied for the induction of sister-chromatid exchanges (SCEs) in human lymphocytes in vitro with (whole-blood cultures) and without erythrocytes (isolated lymphocyte cultures). 2-AF (0.025-0.8 mM) was present in the cultures for the last 48 h of 72-h cultures. In both types of culture, SCEs increased in a dose-dependent manner, with a statistically significant elevation already at the lowest concentration of 2-AF tested and maximum responses of 2.4-fold (whole blood) and 2.1-fold (isolated lymphocytes), in comparison with mean SCEs/cell in control cultures, at 0.4 and 0.2 mM concentrations (respectively). Thus, the induction of SCEs by 2-AF was not dependent on the presence of erythrocytes. Styrene (2 mM), a positive control chemical known to require erythrocytes for efficient SCE induction in vitro, was shown to produce a 4.9-fold increase in SCEs in whole-blood cultures, but only a slight (1.3-fold) effect in isolated lymphocyte cultures. The results suggest that leukocytes, but not erythrocytes, are important in the metabolic activation of 2-AF in the human lymphocyte SCE assay.

Adult↗
PubMed1992

Mouse bone marrow micronucleus test using flow cytometry.

At present, the micronucleus test is the most popular short-term assay for the in vivo detection of clastogens or spindle poisons. As micronuclei are rare events, it has been argued that the conventional microscopical analysis based on 500-2000 cells per animal does not provide enough sensitivity. In addition, the manual scoring of micronuclei is time-consuming and tedious. As an attempt to solve these problems, an automated method for the analysis of micronuclei in mouse bone marrow erythrocytes was developed using flow cytometry. Femoral bone marrow cells, from mice treated with known in vivo clastogens [mitomycin C (MMC): 0.5, 1 or 2 mg/kg body weight intraperitoneally; benzene: 1000, 2000 or 4000 mg/kg body weight orally] or vehicles for the clastogens (physiological saline, olive oil; for control animals), were fixed with 1% glutaraldehyde, suspended in 70% ethanol for storing, stained with 4',6-diamidino-2-phenylindole (0.5 microgram/ml) and analyzed (50,000 cells per sample) in an EPICS V flow cytometer using a Coherent 5W UV laser at 150-200 mV. The frequency of micronucleated erythrocytes (MNEs) was calculated from the cytometer, by a computer program involving model fitting to normal Gaussian distribution. Correlations between MNE frequencies obtained by manual microscopic observations (1000-2000 cells per animal) and by the flow cytometric measurements were good for both group results (means of 4-5 mice; linear correlation coefficient r = 0.89-0.998) and individual data (r = 0.82-0.96). Repeated experiments with MMC showed good reproducibility for the flow cytometric scoring of micronuclei.

Algorithms↗
PubMed1992

Flow cytometric micronucleus test with mouse peripheral erythrocytes.

Flow cytometric (FC) analysis was applied to micronucleus test with mouse peripheral blood erythrocytes. The method is based on the measurement of peak fluorescence (PFL) of sphered glutaraldehyde-fixed erythrocytes before and after staining with 4',6-diamidino-2-phenylindole (DAPI), in an EPICS V flow cytometer. The frequency of micronucleated erythrocytes (MNEs) is calculated by a computer program comparing PFL data obtained with and without DAPI. To evaluate the method, male ddY mice were treated with 6-mercaptopurine and benzene and blood was collected from tail vein at intervals of 4-7 days. Both microscopic and FC analysis showed a steady increase in the incidence of MNEs, reaching a plateau when about a month had passed from the start of the treatments. The effects of benzo[a]pyrene, mitomycin C,N-ethyl-N-nitrosourea, bromodichloromethane and potassium chromate (VI) were also studied with both the manual and FC assay in samples collected a week after five weekly treatments. The percentages of MNEs obtained manually and by the FC measurements showed good correlation, the former three chemicals being positive and the latter two negative or, in the FC analysis, difficult to classify. Because of the high number of cells examined (50,000/animal), the FC analysis was probably more sensitive than the manual method where only 2000 cells were scored per animal. This was further suggested by (i) steady time responses, also for individual animals, in the FC results on 6-mercaptopurine and benzene, (ii) overall reduced inter-individual variation in the FC measurements, and (iii) detection of MNE induction by mitomycin C at a lower dose level with the FC than the manual analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Algorithms↗
PubMed1991

Single-strand breaks, chromosome aberrations, sister-chromatid exchanges, and micronuclei in blood lymphocytes of workers exposed to styrene during the production of reinforced plastics.

Chromosome aberrations (CA), micronuclei (MN, cytokinesis-block [CB] method), and sister-chromatid exchanges (SCE) were analysed in blood lymphocytes of 17 workers and 17 control subjects. The mean urinary mandelic acid level (average 9.4 mmol/l) and styrene glycol in blood (average 2.5 mumol/l) implied exposure to about 300 mg/m3 of styrene in the plant. The number of CA was significantly higher in non-smoking workers compared with nonsmoking controls. A significant correlation was observed between duration of exposure and individual CA level of all workers. No significant effects were observed in MN or SCE. Single-strand breaks (SSB) in DNA of isolated lymphocytes were studied in nine of the workers and eight of the controls by the DNA-unwinding technique. The results showed an increase in SSB among the exposed workers. The present findings support earlier reports on the increase of structural CA in blood lymphocytes of workers in the reinforced plastic industry, and also show that SSBs are elevated in such workers.

Chromosome Aberrations↗
PubMed1991

Induction of micronuclei and anaphase aberrations by cytochalasin B in human lymphocyte cultures.

The frequency of micronucleated cells in isolated 72-h human lymphocyte cultures treated with cytochalasin B (Cyt-B; 1.5-6 micrograms/ml for the last 28 h) was 9-21 times higher (mean 14.6 times) among multinucleate than binucleate cells. At 3 micrograms/ml, the concentration of Cyt-B originally recommended for the human lymphocyte micronucleus assay, the frequency of micronucleated multinucleate cells was 8.5%, while 0.7% of the binucleate cells had a micronucleus. Although no dose-dependent induction of micronuclei could be observed for either of the cell types, increase in the concentration of Cyt-B was associated with a decrease in the ratio of multinucleate to binucleate cells. Treatment with Cyt-B (1.5-12 micrograms/ml) increased the frequency of anaphase cells with aberrations, especially lagging chromatids. This finding was explained by a dose-dependent increase in multipolar (greater than or equal to 3 poles) divisions which had a high frequency of anaphase aberrations (39-53%), irrespective of the concentration of Cyt-B. Bipolar anaphases did not show a significant increase in aberrant cells, although a suggestive dependence on the concentration of Cyt-B was observed. The findings indicate that the high frequency of micronuclei in multinucleate lymphocytes produced by Cyt-B is due to mitotic errors arising when bi- (and multi-) nuclear cells divide. To avoid possible artifactually high micronucleus frequencies due to inclusion of cells that have divided greater than or equal to 2 times in the presence of Cyt-B, it is recommended that, in the human lymphocyte micronucleus assay using the cytokinesis-block method, the cell culture time is reduced to minimize the frequency of such cells and that only good preparations and regularly shaped binucleates are included in the analysis.

Adult↗
PubMed1991

1,3-Butadiene and its epoxides induce sister-chromatid exchanges in human lymphocytes in vitro.

Sister-chromatid exchanges (SCEs) were induced in human lymphocytes by 1,3-butadiene and its epoxides 3,4-epoxy-1-butene and 1,2:3,4-diepoxybutane. After a pulse treatment of 2 h, 1,3-butadiene produced a weak but reproducible increase in SCEs both with and without S9 mix. The response was similar in cultures of whole blood and of isolated lymphocytes. The 2 epoxide metabolites of butadiene, studied in whole-blood lymphocyte cultures without exogenous metabolic activation, were highly active SCE inducers. The lowest effective concentrations of butadiene, monoepoxybutene, and diepoxybutane were 2000 microM, 25 microM and 0.5 microM, respectively. A slight but dose-dependent increase in SCEs was also observed without an exogenous metabolic system after a 48-h treatment with 1,3-butadiene. Already the lowest concentration tested (500 microM) was effective. Again, the response was similar in cultures of whole blood and isolated lymphocytes, suggesting that the lymphocytes are capable of metabolically activating 1,3-butadiene.

Butadienes↗
PubMed1991

Determination of 6-thioguanine resistant lymphocytes in human blood by immunohistochemical antibromodeoxyuridine staining.

An immunohistochemical method for the determination of 6-thioguanine resistant (TGr) lymphocytes in human blood samples has been developed. The new technique is a modification of the autoradiographic assay and uses labelling of DNA synthesizing cells by bromodeoxyuridine (BrdU) instead of tritiated thymidine. The label is detected immunohistochemically by using a monoclonal antibody against BrdU in single-stranded DNA. Thawed cryopreserved isolated mononuclear cells are cultured with (TG cultures) and without (control cultures) TG for 40 h, the last 16 h with BrdU. The cells are harvested, fixed and put on microscopic slides; for the TG cultures, all material is used, while slides from the control culture are prepared at a dilution of 1:300. The immunohistochemical staining of the slides involves denaturation of DNA in formamide, incubation with anti-BrdU-DNA antibody, followed by a secondary antibody conjugated with peroxidase and staining with diaminobenzidine. Nuclei that have incorporated BrdU appear brown while all other material remains unstained. The number of all labelled nuclei is scored similarly in control and TG slides and the frequency of TGr lymphocytes is obtained by dividing the number of labelled nuclei in TG slides with that (multiplied by the dilution factor) in control slides. The anti-BrdU method will much simplify and speed up the microscopical evaluation of the TG variants and is very suitable for automation.

Bromodeoxyuridine↗
PubMed1991

Styrene revisited--exposure assessment and risk estimation in reinforced plastics industry.

A survey performed in 32 workshops in reinforced plastics industry showed the mean TWA 8 h concentration of styrene in personal air to be 43 ppm (range 5-182 ppm) among laminators and 11 ppm (range 1-133 ppm) among other workers. The biological measurement of urinary mandelic acid + phenylglyoxylic acid showed mean values of 2.4 mmol/l among laminators without respirators and 1.3 mmol/l when respirators were used. No effects of work related exposure were detected in the cytogenetic parameters, chromosome aberrations, sister chromatid exchanges or micronuclei analyzed in peripheral blood lymphocytes. Grading of the exposure on the basis of lamination method, years of exposure, daily laminating time, air styrene concentration and urinary mandelic acid among laminators, neither revealed any dose dependency.

Air Pollutants, Occupational↗
PubMed1989

Induction of chromosome aberrations and sister-chromatid exchanges by caprolactam in vitro.

Caprolactam (CAP) induced chromosome aberrations in whole-blood cultures of human lymphocytes at 50 mM without metabolic activation (24-h treatment) and at 200 mM in the presence of rat liver S9 mix (1-h treatment). CAP also produced a dose-dependent increase in polyploid cells, the effect being statistically significant at 25 and 50 mM without S9 mix and at 100 and 200 mM with S9 mix. Without metabolic activation, there was an increase in hypodiploid cells at 50 mM and hyperdiploid cells at 12.5 mM. In Chinese hamster ovary cells, CAP produced a marginal elevation of sister-chromatid exchanges at 125 mM in the presence of S9 mix (4-h treatment). The results show that CAP is able to induce cytogenetic changes in vitro at very high toxic concentrations.

Adult↗
PubMed1988

Evaluation of sister chromatid exchange as an indicator of sensitivity to N-ethyl-N-nitrosourea-induced carcinogenesis in rats.

Sister chromatid exchange (SCE) frequencies in peripheral lymphocytes are a frequently used endpoint to indicate exposures to genotoxins in groups of humans. The aim of this study was to ascertain, in an experimental design, whether or not SCE rates have any association with the risk of cancer at the individual level in rats exposed to a known carcinogen. Individual SCE rates were determined in three consecutive analyses in cultured blood lymphocytes of 50 adult male Wistar rats. Analyses were done before as well as 24 hr and 7 days after a single intraperitoneal administration of 0, 25, 50, or 75 mg/kg of N-ethyl-N-nitrosourea (ENU). The animals were followed until death; also, the relationship between SCEs and carcinogenic outcome, i.e., the presence or absence of tumors, and their latency period were examined. ENU significantly decreased the life expectancy of the rats. The tumor types most clearly associated with ENU treatment were various gliomas and thyroid-gland and testicular tumors. ENU induced a moderate (maximally 1.6-fold) increase in the mean frequency of SCEs/cell at both sampling times after treatment. The effect was somewhat more pronounced 1 day rather than 1 week after treatment. The mean SCE rates in rats with ENU-specific cancers or in animals with early or multiple tumors did not differ from those in animals that survived no less than 65 weeks or longer without developing tumors. In ENU-treated animals with tumors, no relationship was found between the mean SCE rate and survival time. It is concluded that in outbred Wistar rats the SCE response in cultured lymphocytes does not indicate individual susceptibility to the carcinogenic action of ENU. On a group basis, however, animals with high SCE rates were shown to have increased risk of cancer.

Animals↗
PubMed1988

Single-strand breaks in DNA of peripheral lymphocytes of styrene-exposed workers.

Single-strand breaks (SSB) were determined by means of the DNA unwinding technique in peripheral lymphocytes of styrene-exposed workers and referents. A slight increase in SSB was observed among exposed subjects in comparison with a control group of office workers. A correlation was found between SSB, the excretion of mandelic acid and the concentration of styrene glycol in blood. The present work suggests that the DNA unwinding technique can be used for screening workers exposed to genotoxic compounds.

DNA Damage↗
PubMed1987

Chromosome aberrations and sister-chromatid exchanges induced by technical grade toluene diisocyanate and methylenediphenyl diisocyanate in cultured human lymphocytes.

Technical-grade toluene diisocyanate (TDI; 80% 2,4-isomer and 20% 2,6-isomer) and 4,4'-methyl-enediphenyl diisocyanate (MDI; about 45% MDI, 25% 4,4'-methylenediphenyl triisocyanate and 30% unspecified compounds of higher molecular weight), used as hardeners in the production of polyurethane, induced chromosome aberrations after a 24 h treatment in the absence of metabolic activation in human whole-blood lymphocyte cultures, MDI at all doses tested (0.54-4.30 microliter/ml) and TDI (0.019-0.150 microliter/ml) at the highest two doses (0.075 and 0.150 microliter/ml). In the presence of rat liver S9 mix (1.5 h treatment), both mixtures significantly increased aberrations at only one of the doses used, MDI at the highest dose (4.30 microliter/ml) and TDI at the second highest dose (0.038 microliter/ml). MDI also marginally increased sister-chromatid exchanges at the highest dose available (2.17 microliter/ml) with and without (48 h treatment) S9 mix. On addition to culture medium, both TDI and MDI formed polymers, which were seen as small particles on the microscopic slides. At high doses the presence of these polymers made metaphase analysis impossible.

Animals↗
PubMed1979

Effects of styrene oxide on chromosome aberrations, sister chromatid exchange and hepatic drug biotransformation in chinese hamsters in vivo.

In vivo inhalation exposure to styrene oxide (25, 50, 75 and 100 ppm) for 2, 4 or 20 days (25 ppm only) had no effects on chromosomal aberration rates or sister chromatid exchange (SCE) frequencies (BrdU/labelling performed in vitro) in the bone marrow cells of Chinese hamsters. The only positive response in aberration frequency was obtained when styrene oxide was injected in lethal concentration (500 mg/kg body weight, i.p.) into the animal. One animal out of six showed slightly elevated SCE values after this high dose. The response of the hepatic drug metabolizing enzymes to styrene oxide exposure was found to be rather weak, which may be due to rather high activity of epoxide hydratase in Chinese hamsters as compared to e.g. mouse.

Animals↗