Irena M. Grześ

Parental exposure to natural mixtures of POPs reduced embryo production and altered gene transcription in zebrafish embryos.

Determination of toxicity of complex mixtures has been proposed to be one of the most important challenges for modern toxicology. In this study we performed genome wide transcriptome profiling to assess potential toxicant induced changes in gene regulation in zebrafish embryos following parental exposure to two natural mixtures of persistent organic pollutants (POPs). The mixtures used were extracted from burbot (Lota lota) liver originating from two lakes (Lake Mjøsa and Lake Losna) belonging to the same freshwater system in Norway. The dominating groups of contaminants were polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane metabolites (DDTs). Because both mixtures used in the present study induced similar effects, it is likely that the same toxicants are involved. The Mjøsa mixture contains high levels of PBDEs while this group of pollutants is low in the Losna mixture. However, both mixtures contain substantial concentrations of PCB and DDT suggesting these contaminants as the predominant contributors to the toxicity observed. The observed effects included phenotypic traits, like embryo production and survival, and gene transcription changes corresponding with disease and biological functions such as cancer, reproductive system disease, cardiovascular disease, lipid and protein metabolism, small molecule biochemistry and cell cycle. The changes in gene transcription included genes regulated by HNF4A, insulin, LH, FSH and NF-κB which are known to be central regulators of endocrine signaling, metabolism, metabolic homeostasis, immune functions, cancer development and reproduction. The results suggest that relative low concentrations of the natural mixtures of POPs used in the present study might pose a threat to wild freshwater fish living in the lakes from which the POPs mixtures originated.

Cadmium regulation by Lasius niger: A contribution to understanding high metal levels in ants

Ants (Formicinae, Hymenoptera) are considered efficient accumulators of Zn and Cd. In this study the relationship between Cd concentrations in soil and in Lasius niger workers was assessed for 20 colonies located along a gradient of Cd pollution. As soil Cd concentration increased from 1 to 8 mg/kg, ant body Cd concentration increased rapidly to about 40 mg/kg, and remained stable at this level, through a progressive increase of soil Cd concentration from 8 to 21 mg/kg. The phase of rapid increase confirms the high ability of L. niger for Cd accumulation, while the stabilization of Cd body concentration indicates either increasing elimination rate or decreasing rate of uptake. Therefore it can be concluded that Lasius niger has a high ability to accumulate Cd, but simultaneously an ability for Cd regulation was detected.

Zinc and Cadmium Regulation Efficiency in Three Ant Species Originating from a Metal Pollution Gradient

Highly efficient accumulation of trace metals is often reported in ants, but their metal regulation strategies are poorly understood. This study examined the relationships between Zn and Cd total (tot) and water soluble (ws) concentrations in soil and in workers of three ant species collected along a metal-pollution gradient: Formica cunicularia, Lasius flavus and Myrmica rubra. Regression line comparisons showed the body loads of metals to depend strongly on the metal and the species. M. rubra showed the most efficient regulation of Zn, as its average Zn concentration and the regression slope were several times lower than for the other species. Although the species differed in their Cd levels, the slopes of the relationships between Cd concentration in soil and in ants did not differ between species (tot: pxa0=xa00.71, ws: pxa0=xa00.31). The very weak relationship for Cd found for all species suggests at least some active Cd regulation. These results can be explained in the context of tissue-specific metal accumulation. High Zn accumulation in mandibles and ovarioles may explain its high accumulation in F. cunicularia and L. flavus.

Zinc kinetics in the ant Myrmica rubra originating from a metal pollution gradient

Ants are efficient trace metal accumulators, but metal kinetics in ants has not been described. Workers of Myrmica rubra collected in seven meadows along a metal pollution gradient were exposed to dietary Zn (1000 mg kg(-1)) for a 80 day uptake period followed by 30 days of clean food. Zn concentrations in the ants from all study sites were found to have been maintained on a stable level, indicating very efficient Zn regulation. No proof of adaptation in terms of enhanced elimination or restricted accumulation of Zn was found. Nevertheless, the results illustrate the general kinetics of Zn in M. rubra, irrespective of the differences between sites.