Cytogenetic biomonitoring of a population of children allegedly exposed to environmental pollutants. Phase 2: Results of a three-year longitudinal study.

Our previous cytogenetic biomonitoring of a group of inhabitants in a village (Mellery, Belgium) where exposure to a mixture of toxic environmental pollutants, (probably originating from a neighbouring chemical waste disposal site) was suspected, showed that difference in the SCE and HFC bioassays was more pronounced for children. The results of follow-up study in 1992 confirmed this surprising conclusion by an even higher incidence. As very few studies have been performed on the levels of children's biomarkers, this group of exposed populations needed to be explored further. Do children residing in the vicinity of hazardous waste sites indeed represent a population at higher risk? In the present study, we compare the performance of various bioassays (SCE, HFC, SSB and MN) in extended exposed and reference children's groups. Simultaneously, in the exposed group, we followed variation in the lymphocyte SCE frequencies as a function of time. Reversibility of the latter biomarker was ascertained subsequent to a preliminary technical remediation of the disposal site. We compared these data with those obtained from a synchronous cross-sectional study on a group of children living near a similar chemical disposal site. The two exposed populations did not differ from the reference population regarding to the SCE and HFC mean levels. Comparisons of the mean levels of the two other biomarkers, SSB and MN, showed no difference between the Mellery exposed children and the reference group from Wavre whereas significant differences appeared when the Hensies group is compared either to the Mellery or to the Wavre reference group.

Cytogenetic monitoring of a village population potentially exposed to a low level of environmental pollutants. Phase 1:SCE analysis.

By analogy to the techniques applied for monitoring biological effects of exposure to genotoxic agents in occupational populations, we have carried out cytogenetic monitoring in a group of inhabitants of a village (Mellery, Belgium) suspected to have been exposed to a variety of toxic environmental pollutants. These pollutants probably originated from a neighboring chemical wastes site. A group of 51 environmentally exposed and 52 reference persons (including children) were examined for the frequency of sister-chromatid exchanges (SCE) in their peripheral blood lymphocytes. The technique was further refined by using a high frequency cells (HFC) analysis. Analysis of the reference subgroups showed a significant difference between non-smoking adults and children. The influence of tobacco was clear, too. In the exposed group, no significant differences could be demonstrated between either the smokers or the non-smokers or the children. Furthermore, not only were the mean frequencies of SCE higher than in the respective reference subgroups but comparison between the two groups also showed a higher number of individuals presenting a HFC level above the background in the exposed group. Surprisingly, the difference was more pronounced for the children. A follow-up of the same exposed population carried out 18 months later and after remediation of the atmospheric chemical release, the previously observed tendencies in the exposure parameter remained unmodified.

Increased sister chromatid exchange frequencies observed in a cohort of inhabitants of a village located at the boundary of an industrial dumping ground: phase I.

Since the mid-eighties, a sand pit located at the boundary of Mellery, a small village in Belgium, has been used as a dumping ground for industrial waste. After a particularly dry summer, many people complained of very foul smells coming from the dumping ground. An analysis of the environmental atmosphere detected alkanes and chlorinated saturated and unsaturated hydrocarbons in various concentrations. Consequently, the Belgian Ministry of the Environment requested additional measurements from the dumping site and the surrounding regions. Given the hazards and possible ill health effects associated with simultaneous exposure to low levels of many chemicals, biomarkers of personal exposure were measured in a representative group of people living in this village. The cytogenetic consequences of daily exposure to a mixture of genotoxicants were measured by the Sister Chromatid Exchange assay. The study included a group of 51 environmentally exposed persons (including 11 children) and 52 controls. A significant increase in Sister Chromatid Exchange frequency was detected among the inhabitants of the village compared to that of the control group, especially among the children living in Mellery as compared to the matched control children.

Isoelectric focusing applied to taxonomic differentiation of the Trichophyton mentagrophytes complex and the related Trichophyton interdigitale.

Somatic extracts from dermatophytes of the Trichophyton mentagrophytes complex and of Trichophyton interdigitale grown on trypticase soy broth were prepared for analytical isoelectric focusing in thin layer polyacrylamide gels over the pH range 4-6.5. A total of 44 strains were studied: 8 Arthroderma benhamiae (4 Americano-European and 4 African races), 4 Arthroderma vanbreuseghemii, 6 Trichophyton mentagrophytes and 26 Trichophyton interdigitale. Laser densitometric analysis revealed two outstanding clusters of profiles. The first one matched with the Arthroderma vanbreuseghemii profile and gathered all the Trichophyton interdigitale strains studied and 4 Trichophyton mentagrophytes. The second one corresponded to the Arthroderma benhamiae profile and gathered 2 Trichophyton mentagrophytes. This isoelectric focusing analysis suggests on one hand that Trichophyton interdigitale might be the anamorph species corresponding to the teleomorph Arthroderma vanbreuseghemii, and on the other hand that Trichophyton mentagrophytes might correspond to two teleomorph species, either Arthroderma vanbreuseghemii or Arthroderma benhamiae.

Ontogeny of mouse B lymphocytes and inactivation by antigen of early B lymphocytes.

Taking advantage of recent findings about membrane fluidity, we have studied and compared the biosynthetic capacities of fetal or neonatal mouse B (bone-marrow derived) lymphocytes (until 10 days after birth) and adult B lymphocytes. Although both early and adult lymphocytes can synthesize surface immunoglobulins, they have a different physiological behavior after interaction with a ligand (anti-immunoglobulin sera or antigen), either in vivo or in vitro. Fetal and neonatal lymphocytes bearing surface immunoglobulins do not reexpress their membrane receptors after capping and endocytosis promoted by anti-immunoglobulin sera. On the other hand, adult lymphocytes resynthesize completely their receptors after the same treatment. Furthermore, intrafetal injections of hemocyanin in pregnant mice lead to a striking decrease in the number of hemocyanin-binding cells. It seems plausible that this non-reexpression of surface immunoglobulins could be the first step in tolerance establishment.