No abstract

The seasonal and spatial fluctuations of heavy metals in the liver of the frog Rana ridibunda from a river in Western Ukraine were investigated. Liver weight was seen to increase from spring to summer/autumn, most probably as a result of accumulation of metabolites, especially fat and glycogen. The concentrations of the metals found in the liver of the frog was in the order: Fe>Cu approximately Zn>Mn>Cd. For most metals, the highest concentration was recorded in the frogs inhabiting the urban site. The highest level of Cu in the liver was observed in the spring, in the agricultural site, while the highest level of other metals was observed in the summer. The most probable explanation for the high concentration of Cu in the rural site was that in this wetland there were discharge effluents from fungicides with Cu in their formula. Compared to other metals, the bioavailability of Cu was approximately 1000 times higher. The high concentration of Fe rather reflects its fluctuation in the water. Despite its very low concentration in the water (below the limit of detection), Cd was detected in the liver of frogs inhabiting both sites. This is an indication that tissues accumulate Cd, despite the very low concentration detected in the water. This may be an indication of intermittent exposure of frogs to Cd and possibly of other heavy metals.

No abstract

The aim of this study was to compare environmental quality in two sites in western Ukraine-rural (R) and urbanized (U)-with the usage of the resident bivalve mollusk Anodonta cygnea. The study was realized during three seasons. The metal uptake and a set of biochemical markers were determined. For each season, Cd and metallothioneins (MTs) contents in the digestive gland and gills of the mollusc were higher at the U site, reflecting its chronic pollution. The oxidative stress in the mollusk was observed at the U site during spring and at the R site during summer and autumn according to the differences in Mn-superoxide dismutase and catalase activities, O (2) (*-) production, lipid peroxidation, and glutathione levels. The elevated vitellogenin-like protein levels in the hemolymph and the ethoxyresorufin-O-deethylase activity in the digestive gland in summer-autumn suggested pollutions by organic substances at the R site. The acetylcholinesterase activity was similar in both groups. The centroid grouping analysis of biomarkers and morphological and water indexes demonstrated the clear differentiation of general response in each group in spring and, at the R site, in summer and autumn but its similarity at the U site in summer and autumn.

There is a great concern about the decline of pollinators, and neonicotinoids emerging bee disorders are assumed to play a significant role. Since changes in learning ability has been observed in honey bees exposed to some acetylcholine esterase (AChE) inhibitors, we therefore, tested in vitro the effect of four neonicotinoids on purified eel AChE. AChE activity was inhibited in a concentration-dependent manner, and calculated IC values for thiamethoxam (IC = 414 μM) and clothianidin (IC = 160 μM) were found to be much higher compared to acetamiprid (IC = 75.2 μM) and thiacloprid (IC = 87.8 μM). The Lineweaver-Burk reciprocal plots for acetamiprid shows unchanged V and increased K values with inhibitor concentrations, while analysis of Michaelis-Menten plots shows predominantly competitive mechanism. The inhibition constant value (K = 24.3 μM) indicates strong binding of the acetamiprid complex to AChE. Finally, the four tested neonicotinoids are not a uniform group regarding their blocking ability. Our results suggest a previously not established, direct AChE blocking mechanism of neonicotinoids tested, thus the neuronal AChE enzyme is likely among the direct targets of the neonicotinoid insecticides. We conclude, that these AChE inhibitory effects may also contribute to toxic effects on the whole exposed animal.