Development of a toxicity test system using primary rat liver cells

Summary A model in vitro rat liver parenchymal cellular toxicity system employing cells obtained by the in situ collagenase perfusion technique has been developed to detect potential liver toxicants. The initial evaluation of this test system was accomplished using cadmium chloride, chromium chloride, cobalt chloride, mercuric chloride, nickelous chloride, sodium arsenite, sodium selenite, and ammonium vanadate. Linear regression analysis of the dose response curves was used to determine the effective concentration at which the viability was reduced to 50% (EC₅₀). The relative toxicity of the compounds was as follows: Cd>V=As>Se>Hg>Cr=Co>Ni. Since several of the compounds with very similar EC_50S had significantly different dose response slopes, an additional parameter, lowest effective concentration tested (LECT) was employed to assess the relative toxicity. The LECT was determined using the Williams test and the relative toxicity of the compounds was found to be Cd=Se>V>As=Hg>Co>Cr=Ni. The primary objective in developing this rat liver cellular toxicity test system was to employ an in vitro test system utilizing metabolically active primary cells from a potential target organ. This study demonstrates the utility of this test system in determining the relative liver cell toxicity of a series of inorganic agents of differing toxicity.     

Standardization of methods of analysis for heavy metals in sediments

In studies of heavy metals in sediments, there is a need for standardization of the procedures for sample collection and preservation, chemical analyses and presentation of results. The method and depth of sampling depend on the aim of the investigation and on local sediment conditions, such as consistency of the sediment, rate of sedimentation, diagnetic processes and bioturbation. Therefore no general recommendations can be given in this respect. During collection and preservation, contamination and loss of constituents ust be avoided. In sediments, the best means for estimating total contents of metals is digestion with HF, in combination with strong acids. Other methods include X-ray fluorescence and neutron activation analyses. The use of HF is considered objectionable by some laboratories. A reasonable alternative is aqua regia. Because variations in granular composition affect metal contents, it is advisable to use the fraction < 63 μm for the analysis. Chemical partition of sediments provides an insight into the source of metallic constituents, and their pathways to deposition areas. A three-step extraction procedure, in the sequence 0.1 M hydroxylamine-HCl, H₂O₂ 30% and HF, is proposed. Finally, attention is paid to the anthropogenic enrichment of metals in sediments. The establishment of base-line levels is discussed.     

Metabolic costs incurred by crayfish (Procambarus acutus) in a trace element-polluted habitat: further evidence of similar responses among diverse taxonomic groups

Recent studies of several vertebrates and an invertebrate have shown elevated standard metabolic rate (SMR) following chronic exposure to a mixture of trace elements in a contaminated habitat. In this study, we examined whether another invertebrate, a crayfish (Procambarus acutus), also experienced elevated SMR in response to the same contaminants. We compared SMR of individuals inhabiting the contaminated site with SMR of individuals from uncontaminated reference sites. We also examined SMR of individuals collected from the reference areas and exposed in the laboratory for 50 days to sediment and food derived from the contaminated site. Individuals collected from the contaminated site had elevated SMR compared to individuals collected from the unpolluted areas (25.1 vs. 19.2 J g^?1 day^?1). Individuals exposed to contaminated sediment and food in the laboratory experienced elevations in SMR compared to controls after 27 days of exposure (35.2 vs. 29.4 J g^?1 day^?1), but after 50 days of exposure, metabolic rate no longer differed between treatments. Growth of contaminant-exposed individuals was lower than growth of reference animals throughout the laboratory study. Elevated SMR associated with contaminant exposure may reflect energy-demanding mechanisms required to combat deleterious effects of contaminants. Our results support the prediction that increases in energy expenditure in the contaminated habitat would negatively influence production processes, such as growth. Results from this study in conjunction with observations from other species suggest that increased SMR is a common response among several taxa to the mixture of contaminants in the study site.     

Ectomycorrhizas: their role in forest ecosystems under the impact of acidifying pollutants

The physiologically active lateral rootlets of all main trees in temperate forests are colonised by ectomycorrhizal fungi, forming so-called ectomycorrhizas. These symbiotic organs are the sites of exchange of nutrients, mainly P and N, provided from the fungal partner, and C from the host. Emerging from the ectomycorrhizas, fungal hyphae exploit the soil for the mobilisation and absorption of water and nutrient elements. By doing so, they connect the tree roots intimately with the soil and provide anchorage. The deposition of acidifying pollutants into forest ecosystems is a potential threat to the health and vitality of forest trees because it leads to the acidification and eutrophication of forest soils. Pollutants are also a threat to the functioning of ectomycorrhizas. Increased N concentrations in the soil lead to enhanced fungal N uptake and storage, and to enhanced N transfer to the host plants, and therefore to higher plant biomass of above ground parts. In consequence, there is a decrease of C allocation to the plant roots. This in turn leads to reduced ectomycorrhization, and to reduced production of external mycelia and fruiting bodies. Soil acidification leads to enhanced availability of Al, heavy metals, and radionuclides in the soil, all of which can be toxic to plants and fungi. Reduced growth of roots and hyphae are amongst the first symptoms. In ectomycorrhizas, the hyphae of the fungal tissues contain vacuolar polyphosphates which have the ability to bind Al, heavy metals, radionuclides and N. These electronegative polymers of phosphates represent an effective storage and detoxifying mechanism which otherwise is lacking in roots. Therefore, ectomycorrhizas have the potential to increase the tolerance of trees to acidifying pollutants and to the increased availability in the soil of toxic elements.     

Interaction of metals with peroxidase--mediated luminol-enhanced, chemiluminescence (PLmCL).

The peroxidase-mediated luminol-enhanced chemiluminescence (PLmCL) method has been used to study the in vitro effect of contaminants such as heavy metals on the reactive oxygen species production by immunocytes. We were interested to know whether metals could directly affect peroxidase-mediated luminescence, taking horseradish peroxidase (HRP) as a model enzyme, since this could contribute to the inhibition of immunocyte LmCL. Copper inhibited PLmCL in a dose-dependent manner, while cadmium, iron, silver and lead only partly decreased the signal in the concentration range tested. In contrast, zinc enhanced the signal at high concentrations. Eventually, chromium, mercury and aluminium did not affect PLmCL. It is suggested that these effects reflect the ability of the metals to interact with the active site of the peroxidase. These results demonstrate that such interactions have to be considered when interpreting the effects of metals on immunocytes using the LmCL method.     

Serum selenium and gluthathione-peroxidase activities and their interaction with toxic metals in dialysis and renal transplantation patients

Selenium, aluminum, cadmium, and magnesium concentrations and gluthathione-peroxidase activities in sera of 35 healthy individuals, 30 renal transplants, and 30 hemodialysis patients were measured. Serum selenium, aluminum, and cadmium concentrations in both groups of patients were higher than the controls (p<0.001), whereas the serum gluthathione-peroxidase levels were lower (p<0.001). According to our results, it can be concluded that the patients receiving hemodialysis are subjected to more toxic elements than the transplantation patients. These findings imply that dietary selenium supplement may be suggested in renal failure for the detoxification of elements, such as cadmium and mercury. The essential trace element selenium takes part not only in the direct protection of endothelial cells against the accumulation of aggressive oxygen species, but also in the preventions of the toxic effects of cadmium or in the modulation of the active calcium transport.     

Seasonality of VAM infection in three populations of Agrostis capillaris (Gramineae) on soil with or without heavy metal enrichment

Three populations of the perennial grass Agrostis capillaris, growing on limestone derived clay with and without natural enrichment of the heavy metals cadmium, lead, and zinc, and on a sandy soil polluted by a metal smelter have been investigated with regard to the percentage and seasonality of infection with vesicular-arbuscular mycorrhizal (VAM) fungi and its impact on mineral nutrition.In all populations VAM infection was lowest during winter, and highest during late summer and autumn. The population at the metal smelter site was less infected by VAM fungi than both other populations. The concentration of mineral nutrients for the three populations was clearly related to the soil concentration, but hardly modified by the degree of VAM infection.     

Case studies of variations in suspended matter transport in small catchments

Changes of water and suspended sediment composition during three single flood events were investigated in two small catchments in the Mosel region. In addition to suspended sediment characteristics (turbidity, loss on ignition, density, chlorophyll content), several different nutrients and heavy metals were determined in the dissolved and particulate phase. The flood events investigated were characterized by a single peaked hydrograph. In contrast suspended sediment concentrations and the other parameters showed more complex behaviour. The transport of suspended sediment was not only controlled by discharge magnitude. In the course of a flood event different suspended sediment sources are activated. Using the chemograph and the timing of samples collected during the hydrograph these suspended sediment sources can be identified. In addition to the remobilization of sediment and channel erosion, inputs of suspended solids from a sewage plant, road discharge, topsoil and interflow could be identified.     

Heavy metals in the Dead Sea and their coprecipitation with halite

After a prolongued period of stratification (about 300 years) the Dead Sea overturned in 1979 and again in 1982. Its waters became saturated with respect to halite and the massive precipitation of halite which occurred in winter 1982/83 has been monitored. We followed the fate of the heavy metals during this period of physical and chemical changes.The concentrations of Zn, Cd, Pb and Cu in the Dead Sea waters have been measured by anodic stripping voltammetry (ASV) which provided sensitive measurement of these elements after a minimal pretreatment of the samples (dilution 1: 1 and acidification). In the meromictic lake (prior to 1979), the concentrations of all four elements were larger in the deep anoxic layers. With the onset of halite precipitation a decline in their concentrations was observed. Most dramatic was the decrease in Cd, which practically disappeared from the water column in 1985. The coprecipitation of heavy metals with halite — collected by sediment traps in 1983 — was examined, as well as that of older halite recovered from a sediment core. Although concentrations of heavy metals were somewhat larger in recent halite, all halite samples had the same coprecipitation pattern: the concentration of Pb was the largest, followed by Cd, and that of Cu was the smallest. The apparent distribution coefficient was larger for Cd than for Pb.We estimated the amount of Cd which may have accompanied the deposition of halite during 1983–1985; it is compatible with its observed disappearance from the water column in 1985. The amounts of Pb and of Zn which are missing from the Dead Sea of 1985 are much larger than can be accounted for by coprecipitation with halite. A possible explanation is that the formation of halite crystals may have enhanced settling of particulates which in turn, may have scavenged Pb and Zn from the Dead Sea waters. Cu seems to be much less affected by the physical and chemical events which occurred in the Dead Sea during 1976–1985.     

The water quality of the two Maarsseveen Lakes in relation to their hydrodynamics

The hydrodynamics of the two Maarsseveen Lakes are the main cause of the difference in water quality. The meso-oligotrophic Lake I is mainly supplied by groundwater and rainwater while the eutrophic Lake II is fed by water from the River Vecht. Both lakes, however, have a relative high concentration of Zn and Cd in their water system and sediment. The mean concentrations of Zn and Cd in the water system are even higher than in the River Vecht. Measurements of atmospheric deposition (dry and wet) illustrated high levels of Zn, Cd and Cu transported to this area. There are indications that three metallurgical industries located in this region are responsible for the high deposition of these metals in the lakes (PULLES, 1986).