Toxic Effects Of Heavy Metals Research Articles

The effect of lead on the eruption rates of incisor teeth in rats

The effects of lead on the continuously erupting rat incisors under normo-, hyper- and hypofunctional conditions were investigated. Left lower incisors of 20 rats were rendered unimpeded (hypofunctional) by cutting them out of occlusion every 2 days; the right lower incisors of these rats were considered hyperfunctional. Measurements on normally growing teeth (normofunctional) were carried out in a group of ten rats whose teeth were not cut but only marked every 2 days. On day 7 of the experiment, half of the rats from these two groups were given a single intraperitoneal injection of lead acetate (40 mg/kg), and the other half received sodium acetate (22 mg/kg). Another group of 15 rats was used to obtain blood samples for lead determination 1 h, and 10, 20, and 30 days after lead administration. Animals were killed on day 32. Hypofunctional incisors from lead-treated rats erupted more slowly than control ones ( P<0.05). These results show a previously unreported toxic effect of heavy metals.

Biomarkers and fluctuating asymmetry as indicators of pollution‐induced stress in two hole‐nesting passerines

Abstract1. The stress caused by air pollutants was studied at biochemical, morphological and ecological levels in the Pied Flycatcher, Ficedula hypoleuca, and Great Tit, Parus major, nestlings in 10 study sites along the pollution gradient of a copper smelter.2. First, stress was measured using four biomarkers from blood and liver: ethoxyresorufin O‐deethylase (EROD) enzyme, haemoglobin, stress protein Hsp70 and delta‐aminolevulinic acid dehydratase (ALA‐d) enzyme. Second, the amount of fluctuating asymmetry (FA) in the length of the 3rd primary and the outermost rectrix (in P. major) and the length and thickness of the tarsus were measured. These stress indicators were further examined in relation to the breeding performance of birds, i.e. the ecological response.3. EROD activity was increased in F. hypoleuca nestlings near the pollution source. In P. major, it was not related to the pollution gradient but correlated well with the proportion of starved nestlings, i.e. the nutritional stress during the nestling period. The variations in haemoglobin, Hsp70 and ALA‐d enzyme activity were not significantly related to pollution gradient.4. The tarsus length of F. hypoleuca nestlings and primary length of P. major nestlings showed increased asymmetry in the vicinity of the pollution source. Breeding success decreased towards the pollution source in both species.5. In F. hypoleuca, the pollution‐related stress was verified at all three target levels. In P. major, pollution‐related effects were found at morphological and ecological levels but not at the biochemical level, which suggests that direct toxic effect of heavy metals was not the main mechanism in this species.

Biochemical adaptation of the barley root cells to toxic substances. II. Effect of heavy metals on phosphohydrolase activity

We studied the effect of heavy metals such as Cu, Zn, Cd, and Pb on the activity of membrane-bound and soluble phosphohydrolases of barley root cell apoplast. The effect of heavy metals on the activity of acid phosphatase and acid nucleotidases proved to depend on the presence of calcium and magnesium ions in the incubation buffer, the condition and form of the enzymes, as well as the dose and moment of heavy metals addition. We propose changing the activity of acid phosphohydrolases in barley root cell apoplast as a possible mechanism of barley adaptation to the toxic effect of heavy metals.

Stress physiology of palm trees II. The effect of heavy metals and high irradiance on the photosynthesis of palm Trachycarpus fortunei

A study was carried out to analyse the individual and combined effects of heavy metal toxicity and high irradiance on the photosynthetic characteristics of young, fully expanded leaves of palm seedling Trachycarpus fortunei under laboratory conditions. Heavy metals were found to inhibit both the light and dark reactions of photosynthesis and the inhibition was more affected in the light than in the dark. Single photoinhibitory conditions caused a 60 % decrease in the electron transport activity after 120 min of light exposure which was completely reversible in the dark. In contrast, the combined effect of high light and heavy metal treatment resulted in a 90 % decrease in the activity, but no reversible recovery in the dark could be detected. This indicated that the simultaneous effect of these two stress factors led to irreversible damages of the photosynthetic machinery and as a consequence caused the general destruction of the plant.&#x0D; Abbreviations and symbols: Fo: initial chlorophyll fluorescence; Fm: maximum total fluorescence; Fv: variable fluorescence; AFi: intermediate level of fluorescence induction; PSII: photosystem 2.&#x0D;

Toxicity assays and bioconcentration of mercury in bacteria selected from marine environments.

Heavy metals released in marine environments are of increasing concern. Owing to the importance of the marine microbial communities, there have been numerous studies to predict and analyze the toxic effect of heavy metals on natural communities (Suedel et al.1994). Biological parameters such as growth rate, biomass measurement and specific enzymatic activities are currently used to evaluate toxic effects on bacterial populations (Montuelle et al. 1994).

Implication of the Midgut of the CentipedeLithobius forficatusin the Heavy Metal Detoxification Process

Ultrastructural and autometallographic investigations of the midgut of experimentally intoxicated centipedes,Lithobius forficatus, have been performed to investigate the functional role of the epithelial cells in the detoxification of heavy metals. Ultrastructural study demonstrated that nonessential metals such as cadmium and lead may cause intracellular changes, i.e., appearance of electron-dense granules with a spongelike aspect and increase in the number and the size of concentrically structured granules. The autometallographic procedure demonstrated that both types of granules are the main organelles of the midgut to accumulate heavy metals. The permanent storage of metals in granules is a mechanism used by centipedes to reduce the toxic effects of heavy metals assimilated in excess. Consequently, midgut epithelium works as an efficient barrier to prevent excesses of certain metals in the internal environment.

The adsorption of heavy metals in an acidogenic thermophilic anaerobic reactor

A two-phase, thermophilic anaerobic reactor was operated with a starch-based feed. Copper, zinc, nickel and lead (3 mM) were individually added to the feed each for a period of 30 h. The results were analysed to determine the extent of metal binding in the acidogenic, first-stage reactor and the degree of protection that this afforded to the traditionally more sensitive methanogenic phase. The results showed that zinc and nickel were not bound particularly well, that lead was bound very strongly and that copper had binding characteristics that were between these two extremes. When these findings were compared with an earlier study with a mesophilic sludge, zinc was shown to have a very different behaviour. A possible reason for this is given. An examination of the gas production by the methanogenic stage, in relation to the amount of metal reaching this stage, suggested that the phase separation did not offer any real protection from the toxic effects of heavy metals.

Evaluating Intracellular Signaling Pathways as Biomarkers for Environmental Contaminant Exposures

The number of biomarkers being evaluated as environmental indicators continues to increase even as proposed assessments expand in complexity. One key to a rational consolidation may lie in clearly identifying and characterizing those biochemical pathways shared among many biomarkers which are sensitive to environmental perturbation. Recent studies suggest that signal transduction pathways which are common to many cell types and species may provide multiple targets for the toxic effects of heavy metals. Such intracellular communication pathways might provide a useful framework for understanding hormetic effects and for predicting responses to complex contaminant mixtures. Preliminary in vitro experiments tested the effects of mercuric chloride (HgCl2) and cadmium chloride (CdCl2) on signal transduction in cells of the teleost immune system. Concentrations of inorganic mercury ≥ μM suppressed DNA synthesis and induced rapid influx of radiolabelled calcium within ten minutes as well as tyrosine phosphorylation of numerous cellular proteins within one minute. Lower concentrations (0.1 – 1 μM) of HgCl2 which activated cell growth also induced a slow rise over two minutes in intracellular calcium in cells loaded with the calcium indicator dye, fura-2, but did not produce detectable tyrosine phosphorylation of leukocyte proteins. Although CdCl2 >10 μM also suppressed DNA synthesis, this environmental metal failed to activate cell growth or to induce tyrosine kinase activity at any concentration tested. Future experiments will assess how cells which are exposed to both metals integrate these mixed signals. This approach may provide a means of predicting cellular responses to multiple contaminants over broad dose ranges

Zinc and Cadmium Effects on the Early Stages of Nodulation in White Clover

AbstractAddition of heavy metals to soils from sources such as biosolid application, smelter emissions, fertilizers, and the like may produce soil solution concentrations of Zn and Cd that can potentially restrict nodulation of legume crops such as white clover. To assess the effects of Zn and Cd on the early stages of nodulation of white clover, a solution culture study was conducted. Rhizobia [Rhizobium leguminosarum bv. trifolii] of a metal‐sensitive strain (USDA 2063) and a metal‐tolerant strain (USDA 2046) were inoculated into nutrient solution with white clover seedlings containing EGTA to buffer Zn2+ and Cd2+ activities. The calculated activities of Zn2+ were p = 8.00, 5.70, 5.25, and 5.00; the calculated activities of Cd2+ were p = 10.50, 9.50, 8.75, and 8.50. Phase‐contrast microscopy was used after staining roots with methylene blue to observe root hair infection at intervals of 1, 12, 24, 72, and 168 h. Few differences were observed between the sensitive and tolerant rhizobial strains. At the lowest Zn concentration, initial attachment of bacteria to root hairs was observed within 1 h. At the highest Zn concentration, attachment was not observed until 12 h. Also, at the highest Zn concentration, a delay was observed for up to 60 h and 4 d, respectively, for the first signs of root hair curling and infection thread formation. Shoot weight decreased with increasing Zn concentration. Few Cd‐induced effects on early stages of nodule development were observed. Cadmium was more toxic to plant growth than Zn. These results show that in addition to direct effects on the macro and microsymbiont, the process of nodulation is susceptible to the toxic effects of heavy metals.

Qualitative X-Ray Fluorescence Analysis of Emitted Aerosol Particles from Incineration Plants Sampled on Quartz Fibre Filters

The toxic effects of heavy metals in stack gases from industrial furnaces were taken into account in the emission limits of the German law 17. BImschV (17. Bundes-Immissionsschutzgesetz-Verordnung) from November 23, 1990. Results of the first manual stack emission samplings are presented. During the sampling period a new active carbon packed-bed reactor was installed for further cleaning of the stack gases. A reduction by a factor of 10 for most elements was observed. Because of their resistance to hot (150°C) and corrosive gases, quartz fibre filters were used for sampling the emitted aerosols. The aerosol-loaded filters were analysed using an X-lab XRF-spectrometer (Spectro A.I.) calibrated with laboratory-developed standard filters. In the future, a combined sampling and analysis system for continuous emission control, planned together with Spectro A.I. (Germany) with financial support of the German Federal Department of Education and Science (BMBF), will be used.

Effect of sewage sludge on nodulation and N2−fixation in alfalfa grown on calcareous loamy soils

AbstractThe influence of different rates of sludge applications to calcareous loamy soils of Saudi Arabia, on nodulation and symbiotic N2−fixation in alfalfa plants (Medicago sativa L.) was studied in a pot experiment. The effect of heavy metals accumulation in soil due to continuous irrigation of the test soil with sewage water was also investigated. Application of up to 80 g sludge per pot enhanced nodulation, nitrogenase activity, dry matter yield and N‐contents of alfalfa plants growing in loamy soils either previously irrigated with sewage water or well water. However, sludge applied at the rate of 160–200 g pot−1 inhibited the nodulation, N accumulation and dry matter yield of alfalfa. The response of alfalfa to sludge was dependent on the rhizobial strain used. Our results also showed that accumulation of heavy metals due to continuous irrigation of a calcareous sandy loam soil with sewage water, for more than 10 years, didn't inhibit N2−fixation in alfalfa plants, but enhanced it. Microelements in alfalfa plants increased with increase in the rate of sludge application. Although high rates of sludge application affected nodulation and N2−fixation of alfalfa, dry matter and the nitrogen contents of the plants were not highly affected. Therefore, the inhibitory effect of high rates of sludge was most probably due to the toxic effect of heavy metals on the microsymbiont rather than on the plants.

Accumulation of some heavy metals in various environments and organisms at Göksu Delta, Türkiye, 1991-1993.

Over the last three decades the aquatic ecosystems have been contaminated by persistent pollutants of agricultural and industrial origin. Experimental research on toxic effects of heavy metals in waterbirds with pollutions from agricultural areas specially seed treated with use of organomercurial fungicides in agriculture resulted in pollution of aquatic systems with Hg (Beefting and Neuweshuize 1986). Heavy metals have been documented to have adverse effects on the reproduction and survival of certain waterbirds in aquatic ecosystems (Sanders, 1984; Molueg et al 1984; Rico et al 1988; Burton 1990; Fox et al 1991).

Toxic effect of heavy metals on the activated sludge protozoan community

The acute toxicity of five heavy metals to the protozoan community inhabiting the activated sludge of a waste treatment plant, was determined on the basis of reduction in both cell density and species richness. The activated sludge mixed-liquor was treated with different concentrations of cadmium, copper, chromium (VI), lead, and zinc for a period of 24-h. The experimental results enabled to determine the relative toxicity of the tested metals, and indicated that the order of toxicity of the five metals to the studied microbial community was generally: Cd, Cu > Pb > Zn > Cr. For nine out of sixteen protozoan species constituting the studied community was possible to determine the 24-h median lethal concentration (24-h LC 50) for each tested metal. Large differences appeared in sensitivities of the nine species to the metals. Ciliated protozoa such as Chilodonella uncinata and Trochilia minuta showed the highest sensitivity to all the studied metals, while Opercularia coarctata and O. minima, were the most tolerant species.

Measurement of cell membrane toxicity by means of 2-deoxy-D-glucose.

AbstractThe membrane theory of toxicity (1) emanates from the fact that the plasma membrane is the first barrier met by a toxic agent on reaching the cell, and was first advanced to explain the toxic effects of heavy metals. The vital regulatory mechanisms inherent in the plasma membrane and its chemical composition make it susceptible to many toxic compounds (2). A toxic substance may cause structural alterations in the membrane by binding to or crosslinking proteins or by dissolving in the lipid matrix and thereby disturbing its order. The formation of functional holes in the membrane through the action of chemicals with detergent properties is common. Structural alterations often lead to specific functional changes, since the function of both integral and peripheral proteins are greatly influenced by their lipid environment. Furthermore, chemicals may induce toxic effects by direct interaction with functional proteins.KeywordsTissue Culture DishScintillation VialCell Membrane PermeabilityPerfusion ChamberNa2HPO4 12H2OThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Densities of microtime rodents along a pollution gradient from a copper-nickel smelter.

Population densities of microtine rodents were studied along an air pollution gradient in the Kola Peninsula, Russia, by long-term and short-term trapping. The study area is affected by high sulphur dioxide and heavy metal emissions from the Severonikel copper-nickel smelter in Monchegorsk. The density of Clethrionomys rufocanus, the most abundant vole species in the area, was lowest close to the smelter and increased with distance up to the farthest, less polluted trapping sites. Clethrionomys glareolus, C. rutilus and Lemmus lemmus were absent from the most severely damaged area and were also scarce at the moderately polluted area 28 km south of the smelter. Although the population of C. glareolus has previously been cyclic at the moderately polluted area, we were unable to demonstrate any regular cycle. The most likely explanation for the low number of microtine rodents in the damaged and moderately polluted areas in a decrease in the quantity of important food plants: epiphytic lichens for C. glareolus and possibly C. rutilus, mosses for L. lemmus and seed plants, especially Vaccinium myrtillus, for C. rufocanus. Close to the smelter, direct toxic effects of heavy metals may also reduce population densities. The results show that pollutants may change the relative proportions of microtine species.

Effects of cobalt on plants

Effects of cobalt on plants

Fetal Nephrotoxicity

Investigation of fetal nephrotoxicity by maternally administered nephrotoxins is hampered by many constraints, including the maternal effects of the nephrotoxin, the ability of the nephrotoxin to cross the placenta and the difficulties associated with direct fetal intervention. In the pouch young of the North American opossum, Didelphis virginiana, we describe the toxic effects of a heavy metal on the immature metanephric kidneys. Varying doses of uranyl nitrate, a heavy metal salt, were administered to opossum pups in the pouch approximately 20 days after birth and the kidneys were harvested 3 to 12 days later for histological analysis. Group 1 consisted of 4 untreated and 5 saline treated pups. Group 2 (9 pups) received 10 to 15 mg./kg. intraperitoneal uranyl nitrate. Group 3 (6 pups) were given a uranyl nitrate dose of 25 mg./kg. Group 4, the high dose group, received either 58 mg./kg. (3 pups) or 87 mg./kg. (3 pups) of intraperitoneal uranyl nitrate.Group 1 kidneys demonstrated no pathological changes except for some mild renal tubular vacuolization seen in the saline treated animals. In group 2 tubular dilatation and necrosis were present 3 days after treatment; tubular regeneration could be seen by day 7. In group 3 glomerular cystic changes, interstitial fibrosis and tubular regeneration were present by day 7. Some restoration of normal architecture occurred by day 12 with fibrosis apparent. Group 4 animals demonstrated much more pronounced cystic changes of glomeruli and tubules as early as day 5 with marked interstitial fibrosis and prominent tubular regeneration. By day 12 group 4 pups continued to demonstrate significant and severe glomerular and tubular cystic changes with marked interstitial fibrosis. Inflammation, although present in all groups (except control), was never prominent. This first description of the effect of heavy metal toxicity on the immature metanephric kidney could provide an insight into the mechanisms of disordered kidney growth.

Effects of toxic heavy metals (Cd, Pb) on growth and mineral nutrition of beech (Fagus sylvatica L.)

The beech (Fagus sylvatica L.) is the dominant tree in Middle Europe under many different ecological conditions. But like other tree species, it is suffering in the last ten years increasingly by air pollutants including heavy metals which have been deposited and accumulated for decades in many forest soils. Increasingly mobilized by acidification processes, these metals may have toxic effects on trees.

Biodegradation of Sewage Sludge: Toxic Effects of Heavy Metals

Investigates the fate and toxicity of continuous feeding with increasing dosage of heavy metal ions – Cu, Pb, Zn, Cr(VI) – on biogas production from anaerobic digestion of sewage sludge. The efficiency of the system (as measured by biogas production and volatile organic matter removal rate) was reduced for about 35 days before returning to a steady state with the toxicity ranking Cu &gt; Cr (VI) &gt; Pb &gt;Zn. Also looks at the effect of two “pulse” doses of the metals.

A model for the impact of soil solution Ca: Al ratio, soil moisture and temperature on tree base cation uptake

A model for tree base cation uptake has been developed, dependent on the soil solution concentration of Al3+, divalent base cations such as Ca2+, Mg2+ and H+ ions, modelled with a Mikaelis-Menten type of expression based on the molar BC∶Al ratio, where BC is the sum of the divalent non-toxic base cations Ca2+ and Mg2+. The expression has the form of counteracting adsorption isoterms for BC and Al to the tree root. The effect of toxic levels of Hg and Pb is incorporated into the model, using root adsorption as the mechanism, and parameterization against experimental data. The expression is modified with an expression accounting for the effect of heavy metal toxicity and soil water content. The dependence of the uptake rate on soil moisture content can be shown to have the form of a Freundlich adsorption isotherm for water. The available data indicate an activation energy of 47 kJ−1 mol for base cation uptake to trees. Data from the literature was used to estimate the rate coefficients and ion selectivity coefficients for typical coniferous and decideous trees in Sweden and Germany. The model indicates that Ca2+ and Mg2+ is effective in mitigating Al3+ toxicity to tree roots, and that increasing the Ca2++Mg2+ soil solution concentration has a promotive effect on base cation uptake. Above a certain limit base cation uptake becomes independent of the solution base cation concentration. This is consistent with field observations, and may be developed to become a tool for assessing the impact of soil chemistry changes on forest growth rate and health status. Field data from the Swedish Forest Survey indicate that uptake depend on the square root of the soil solution base cation availability originating from weathering and deposition input, which is consistent with the BC∶Al expression of the model.