Search

20 individuals working organic chemistry and 11 theologians (referents) from the same university were investigated for frequencies of micronuclei in cultured lymphocytes. The chemists had been exposed for 3 to 36 (mean 12) years. No effect of the chemical exposure was found on the micronucleus frequencies. The lack of effect may be due to the improvement of the work environment in chemical laboratories.

Occupational high-dose exposure to metallic mercury can cause immune disturbances in sensitive individuals. Whether low-dose exposure to inorganic mercury from dental amalgam has this effect in humans is one of the issues related to the concept of oral galvanism and is supported by results of animal studies. This study explored some cellular immune factors (B- and T-lymphocytes, T4, T8, monocytes, neutrophilic, eosinophilic, and basophilic granulocytes, and large unstained cells) and some humoral immune factors (immunoglobulins IgG, IgG1, IgG2, IgG3, IgG4, IgA, IgM, IgE, albumin, alfa-1-antitrypsin, orosomucoid, haptoglobin, and antinuclear antibodies) in 41 healthy 15-y-old schoolchildren. The relationship between these factors and amalgam fillings and mercury concentrations in plasma (P-Hg) were investigated. A low, but significant correlation (r = 0.40, p.05) was found between the number of amalgam surfaces and the P-Hg values, which were low for both sexes (median value = 1.8 nmol/l). There was no significant influence of the number of amalgam surfaces or P-Hg on the immune factors tested, except random findings. The girls had significantly higher values of T8, IgG, and IgG1 than the boys.

Forty-five Swedish chimney sweeps and 49 controls were investigated with micronuclei stimulated by phytohemagglutinin and pokeweed mitogen and by analysis of lymphocyte subgroups and neutrophilic leukocytes. There was a statistically significant effect among sweeps with respect to both micronuclei variables and neutrophilic leukocytes. The effect on lymphocyte micronuclei was most prominent in pokeweed mitogen-stimulated cells, which may imply that the T4 lymphocytes were preferentially damaged by the occupational exposure.

For 26 chloralkali workers exposed to inorganic mercury and 26 age-matched, occupationally unexposed referents, the frequency and size distribution of micronuclei were determined in peripheral lymphocytes stimulated with either phytohemagglutinin or pokeweed mitogen. For the exposed workers the mean concentrations of mercury in urine, plasma, and erythrocytes were 16 nmol/mmol of creatinine, 48 nmol/l, and 78 nmol/l, respectively, and their mean exposure time was 10 years. Neither the frequency nor the size of micronuclei was significantly different in the two groups; nor were there any correlations to current mercury levels. However, in the exposed group, and with phytohemagglutinin as the mitogen, a statistically significant correlation between previous exposure to mercury (cumulative exposure or number of blood mercury peaks) and the frequency of micronuclei was found. This association was also present when the effects of age and smoking were allowed for, and it may indicate an accumulation of cytogenetic effects in T-lymphocytes.

Fifteen gasoline pump mechanics and 15 controls were investigated with the lymphocyte micronucleus assay and also with differential count of leukocytes in the peripheral blood. The lymphocytes were stimulated with phytohemagglutinin and pokeweed mitogen in parallel cultures. The pump mechanics had increased frequencies and sizes of micronuclei in the pokeweed mitogen-stimulated cultures but not in those stimulated with phytohemagglutinin. The difference in effect between the 2 mitogens is probably due to an increased sensitivity of the B-lymphocytes to mutagens. The leukocyte count was significantly higher in the gasoline-exposed group. The effect of the occupational exposure was probably caused by the benzene content of the gasoline. The time-weighted average for 8 h was around 1 mg/m3 of benzene, but there were peak levels of 20 mg/m3.

The metabolic origin of the ansa chain and chromophore of rifamycin S has been investigated by studying the incorporation of radioactive and 13C-enriched precursors. A simplified degradation scheme has been utilised to cleave chemically the radioactive antibiotic into constituent chromophore and ansa chain. Rifamycin S labelled with [3-14C]propionate and [Me-3H]methylmalonate have the same pattern of isotope distribution. Unlabelled propionate efficiently dilutes the incorporation of [Me-3H]methylmalonate but the reverse is not true. Although the results of [2-14C]malonate and [2-14C]acetate incorporation were inconclusive owing to randomisation, the proton-decoupled carbon magnetic resonance spectrum of rifamycin S biogenetically enriched with [2-13C]malonate revealed a specific incorporation into C-5 and C-18. We propose that the polyketide chain is formed by a linear condensation, in the appropriate sequence, of eight methylmalonates and two malonates with the subsequent esterification of the C-25 hydroxyl with acetate. Two precursors were found preferentially to label the chromophore: [3,4-14C2]glucose and [1-14C] glycerate. Out of the seven carbons in the chromophore not deriving from acetate or propionate only C-1 and C-10 appeared significantly enriched by [1-13C] glucose. This labelling pattern, coupled with the 14C incorporation data, suggests that the chromophore may derive from an intermediate of the common pathway of aromatic biosynthesis, before the level of shikimate.

Thirty-two male individuals exposed to isocyanates and amines during the production of plastic foams and 20 male referents were studied by cytogenetic methods (chromosomal aberrations, sister chromatid exchanges and micronuclei in lymphocytes) and by urinary mutagenic assays (thioether concentrations and mutagenic activity with Salmonella TA98 and E. Coli WP2 uvrA). The occupational exposure was monitored by measurements of toluene diisocyanate and N-methylmorpholine in work-room air. The levels were below the current Swedish hygienic standards. Although all parameters, except the sister chromatid exchanges, showed increased mean values for the exposed group compared to the referents, only the urinary thioether concentrations differed significantly. The study was, however, non-conclusive with regard to a genetic effect of the occupational exposure as measured by the cytogenetic parameters. This may be due to the low exposure level. In the micronuclei frequencies there was a significant effect of age. Smoking significantly affected the SCE frequencies, the thioether concentrations and the mutagenic activities in the Salmonella assay. There were statistically significant correlations between the urine specimens collected during one working day and the following morning with regard to the mutagenic activities in the Salmonella and E. coli assays, and in the thioether concentrations as well. The association between the different cytogenetic and urinary mutagenic assays were weak but there were several statistically significant correlation coefficients, indicating that the variables may have a common metabolic background.

For 20 glass-reinforced plastics workers exposed to styrene and 22 unexposed referents, the frequency and size distribution of micronuclei were determined for lymphocytes stimulated with phytohemagglutinin or pokeweed mitogen, and white blood cell counts were made. Furthermore, chromosome aberrations were scored for 11 of the exposed subjects and 15 of the referents. The mean level of styrene in the breathing zone of the workers was 56 mg/m3. Workers exposed to styrene did not show an increase in any of the cytogenetic end points studied when the effect of age and smoking was allowed for in a multiple regression analysis. A significant 30% increase in the number of peripheral monocytes was observed for the exposed workers. No correlations between the cytogenetic and hematological tests on one hand and the length of exposure time on the other could be detected.

Micronuclei were induced in vitro in human lymphocytes by mitomycin C, X-rays, vincristine, and colcemid and analyzed in cells with preserved cytoplasm. The micronucleus/cell nucleus ratio was measured. It was found that micronuclei induced by mitomycin C and X-rays were significantly smaller than those formed by vincristine and colcemid. Thus, in spite of the wide size span of human chromosomes, it could be shown that it is possible to differentiate between micronuclei formed by spindle-damaging agents (vincristine and colcemid) and those induced by agents directly damaging the chromosomes (mitomycin C and X-rays). Mitomycin C-induced micronuclei were smaller than those induced by X-rays, probably because the former agent preferentially produces chromatid fragments and the latter chromosome fragments.