Exposure-dose-response of Tellina deltoidalis to metal-contaminated estuarine sediments: 1. Cadmium spiked sediments

Cadmium is a ubiquitous environmental metal contaminant with an affinity for biological membranes; it can enter cells by facilitated transport and it binds therein to various biomolecules and affects membrane system function. The relationship between cadmium exposure, dose and response was investigated in the benthic, deposit feeding, marine bivalve Tellina deltoidalis, using 28 day microcosm spiked cadmium exposures. Tissue cadmium reached steady state with the exposure concentration. Half the accumulated cadmium was detoxified and with increased exposure more was converted into metal rich granules. Most biologically active cadmium was in the mitochondrial fraction, with up to 7320-fold cadmium increases in exposed organisms. Cadmium exposed T. deltoidalis generally had reduced glutathione peroxidase enzyme activity. An increase in total glutathione concentrations, due to a build up of oxidised glutathione, was indicated by the reduced to oxidised glutathione ratio. All cadmium exposed T. deltoidalis had reduced total antioxidant capacity that corresponded with increased lipid peroxidation, lysosomal destabilisation and micronuclei frequency. Clear exposure-dose-response relationships have been demonstrated for T. deltoidalis exposed to cadmium-spiked sediments, supporting this organism's suitability for laboratory or in situ evaluation of sediment cadmium toxicity.     

Cadmium induction of metallothionein synthesis in Mytilus galloprovincialis

1. The accumulation and subcellular distribution of cadmium and resulting induction of metallothionein has been studied in mussels, Mytilus galloprovincialis, exposed to 400 μg Cd 1⁻¹.2. Cadmium accumulated by mussels was primarily associated with metallothionein: a maximum four-fold increase in concentrations of the metal-binding protein (3 mg g⁻¹ to 12 mg g⁻¹) was observed after 30 days.3. Results for M. galloprovincialis confirm the importance of metallothionein in the detoxification of intracellular cadmium and indicate that induction rates are identical to those observed in the closely-related M. edulis.4. Intercomposition of data between these species may therefore be valid when employing metallothionein assays to determine sub-lethal response to cadmium contamination.     

The effect of cadmium ions and cadmium-metallothionein on the activities of phospholipid-synthesizing enzymes of rat liver microsomes in vitro

The effects of cadmium ions or cadmium-metallothionein on the activities of acyl-CoA:1acyl-sn-glycerol 3-phosphoric acid or 1-acyl-sn-glycero 3-phosphocholine acyltransferase of rat liver microsomes have been studied, in vitro. Cadmium ions were found to cause a noncompetitive type inhibition of these two acyltransferases. The K_i values were calculated, and found to be smallest (1.7 × 10^?5m) for palmitoyl-CoA and greatest (1.0 × 10^?4m) for linoleoyl-CoA, among the several fatty acyl-CoA's tested on the 1-acyl-sn-glycerol 3-phosphoric acid acyltransferases. With the 1-acyl-sn-glycero 3-phosphocholine acyltransferase, the K_i values were found to be smallest for the plamitoyl-CoA acyltransferase (3.8 × 10^?5m) and largest for thearachidonoyl-CoA acyltransferase (1.1 × 10^?4m). In contrast, mouse liver cadmium-metallothionein, including 4 mol of cadmium and 2 mol of zinc in one molecule of metallothionein, was not found to be inhibitory or rather stimulative on the above two acyltransferases at the same concentration of cadmium tested in the cadmium ion inhibitor experiments. The above results demonstrate that there is a strong and irreversible inhibition by cadmium ions on acyl-CoA acyltransferases, but that when cadmium acts on the enzyme in the form of a cadmium-metallothionein complex, the inhibition effect does not occur. These findings may reflect differing degrees of toxicity of these two types of cadmium compounds in mammalian tissues.     

Exposure of silver carp (Hypophthalmichthys molitrix) to environmentally relevant levels of cadmium: hematology, muscle physiology, and implications for stock enhancement in the Xiangjiang River (Hunan, China)

Cadmium is a non-essential metal with a wide distribution that has severe toxic effects on aquatic animals. Changes in hematology and muscle physiology were examined in silver carp (Hypophthalmichthys molitrix) exposed to environmentally relevant levels of cadmium (0.01 mg L^?1) for 96 h. Cadmium exposure induced significant increases in the red blood cell count, and in the plasma concentrations of cortisol, glucose, and lactate. This suggests that the dose of cadmium was sufficient to cause stress, possibly associated with impaired gas exchange at the gills. There were no changes in hemoglobin concentration or plasma protein concentration. Significant decreases in muscle energy fuels (ATP and glycogen), and increases in muscle lactate persisted until the end of the exposure period, respectively. The changes in muscle lactate and protein in silver carp differed from those observed in response to exposure of fish to cadmium and heavy metals in other studies. The study highlights the importance of selecting unpolluted release sites with suitable water conditions for the survival of newly released individuals for stock enhancement of the Xiangjiang River.     

Experimental studies on the cadmium accumulation in the cestode Moniezia expansa (Cestoda: Anoplocephalidae) and its final host (Ovis aries)

The tapeworm Moniezia expansa and naturally infected sheep were investigated with respect to their cadmium accumulation. Cadmium chloride (CdCl₂, 0.2 g) was added to 10 ml of distilled water and administered orally to the sheep every day for a period of 1 week. The cadmium content of M. expansa was lower than that in the liver tissues of sheep, although this difference was not significant. The highest mean cadmium concentrations were found in the liver of sheep infected with M. expansa (24.5 ± 11.5 mg kg⁻¹ dry weight). The mean cadmium concentration measured in M. expansa was 21.5 ± 19.2 mg kg⁻¹ dry weight, which was 31 and 1.5 times higher than levels determined in the muscle and kidney of the host, respectively, but 0.9 times lower than levels determined in the liver of host. Sheeps with M. expansa infection always had higher cadmium concentrations in the tissues (with the exception of the blood) than their uninfected conspecifics.     

Effects of acute exposure to cadmium (II) chloride and lead (II) chloride on the haematological profile of Oreochromis aureus (Steindachner)

1. Oreochromis aureus (Steindachner) was exposed to two concentrations of lead and cadmium for 24 hr and 1 week to assess the effects of these pollutants on haematological parameters.2. Plasma osmolality was found to be the most sensitive blood parameter, affected before other parameters changed.3. Cadmium appears to be more toxic to O. aureus than lead, having an adverse effect on blood parameters earlier than lead.4. In the earlier stages of toxicity cadmium appears to have a more pronounced effect on haemoglobin concentration than lead.5. Cadmium does not depress erythrocyte counts but lead does.     

Cadmium effects and accumulation in cultures ofProrocentrum micans (dinophyta)

Effects and accumulation of cadmium were studied in unialgal 10-1 batch-culture experiments with the dinoflagellateProrocentrum micans Ehrenberg. Tests were made using sterile filtered North Sea water enriched with nitrate and phosphate only in order to avoid disturbances by complex formation. Cadmium was added to the cultures in amounts of 100 to 0.13μg l⁻¹. In one series it was added at the start of the experiments and in a second one after a growth period of 1 week. Addition of only 1.2μg Cd l⁻¹ reduces multiplication rates and maximum cell densities of the algae. Not until 0.4μg Cd⁻¹ does growth correspond to that of the controls. Cadmium concentrations were measured, after filtration, in the culture medium and in the biomass by means of flameless AAS. The cadmium content in algae increased from 2.7μg g⁻¹ (dry weight) in controls to 500μg g⁻¹ (dry weight) in media containing 100μg Cd l⁻¹. Uptake occurred rapidly during the first few days of the experiments, slowed down somewhat during exponential growth stage, and increased during decay of the cultures. Cadmium content of culture media remained nearly constant (Series 1) or decreased only slowly during experimental time (Series 2). The highest concentration factor was measured in the controls. It decreased with increasing metal concentration in the medium and increased with experimental time. Structural modifications of the cells were visible after Lugol fixation only, indicating brittleness of the cell walls.P. micans has shown to be extremely sensitive to cadmium and to accumulate this metal.     

Low-salinity stress in the American lobster,Homarus americanus,after chronic sublethal exposure to cadmium: Biochemical effects

Lobsters(Homarus americanus) were exposed to cadmium (6μg l⁻¹, 30 days) in flowing seawater, then held for 7 days in aerated “clean ” seawater at either ambient (27 ‰) or low (17 ‰) salinity. Cadmium exposure alone (ambient salinity) induced a general elevation of enzyme activity (heart, antennal gland, and muscle MDH; heart LDH and GPI), despite the probability of some clearance of cadmium from body tissues during the “clean ” seawater holding period. Low-salinity alone (non-exposed lobsters) caused a decrease of enzyme activity (AAT, LDH, GPI, PK) in most tissues examined, except for tail muscle IDH, the activity of which was increased, and MDH, which was significantly elevated above ambient controls in all tissues except heart. Most low-salinity effects were observed in tail muscle, and most cadmium effects, in heart; low-salinity effects outnumbered cadmium stress by nine to four. In heart and tail muscle of cadmium-exposed lobsters held at low salinity, each of the two stresses apparently operated to nullify the other's effects. The most prominent single biochemical response to these sublethal stresses was the elevation of MDH activity. The ratio MDH: LDH gave the clearest indication of overall relative stress.     

Growth of mozambique tilapia (Oreochromis mossambicus Peters) chronically exposed to cadmium,naphthalene, and DDVP

The chronic effects of cadmium, naphthalene, and DDVP on the growth of Mozambique tilapia (Oreochromis mossambicus Peters) exposed to concentrations corresponding to 1/30 LC₅₀ for 24 h (cadmium and DDVP) and 1/15 LC₅₀ for 24 h (naphthalene) have been studied. The fish are kept in toxicant solutions for 60 days and then for 60 more days in clean water. It is found that the studied toxicants affect fish-growth indices to varying extents. Organic compounds have no significant effect on the linear and mass growth of tilapia. Cadmium most strongly suppresses tilapia growth, and the toxic effect of this metal is irreversible: all fish die after being transferred to clean water.     

Population level effects of cadmium and the insecticide imidacloprid to the parasitoid, Aphidius ervi after exposure through its host, the pea aphid, Acyrthosiphon pisum (Harris)

The objective of this study was to assess the influence of toxic substances with different modes of action on a two-species system: an aphid-specific parasitoid, Aphidius ervi Haliday, feeding on the pea aphid, Acyrthosiphon pisum (Harris). The instantaneous rate of population increase (r_i) was used as a measure of population level toxic effect in this study. The toxicants evaluated were imidacloprid, a nonpersistent neurotoxic insecticide, and cadmium, a chronic pollutant with a tendency to accumulate. We evaluated the effects of cadmium and imidacloprid on A. pisum and A. ervi because both toxicants can occur together in polluted areas where crops are grown. Cadmium (200 or 400 mg kg⁻¹ dry weight soil) and imidacloprid (4 or 40 g a.i. ha⁻¹) were applied to soil contained in plastic pots in which broad bean plants, Vicia faba L., were grown. Results of this study indicated that cadmium at the concentrations tested, reduced population growth rate of the pea aphid. Imidacloprid also reduced aphid growth rate, but only at the highest concentration tested (40 g a.i. ha⁻¹). Combinations of cadmium and imidacloprid had the greatest impact on aphid growth rate. Imidacloprid alone had no effect on population growth rate of the parasitoid. However, cadmium alone or in combination with imidacloprid had a negative impact on A. ervi by reducing population growth rate 77%. These results indicate that negative impacts on parasitoids may occur in areas where cadmium contamination is present and imidacloprid is used to control aphids.     

Cadmium Exposure and Incidence of Diabetes Mellitus - Results from the Malm? Diet and Cancer Study

Background

Cadmium is a pollutant with multiple adverse health effects: renal dysfunction, osteoporosis and fractures, cancer, and probably cardiovascular disease. Some studies have reported associations between cadmium and impaired fasting glucose and diabetes. However, this relationship is controversial and there is a lack of longitudinal studies.

Objectives

To examine prospectively whether cadmium in blood is associated with incidence of diabetes mellitus.

Methods

The study population consists of 4585 subjects without history of diabetes (aged 46 to 67 years, 60% women), who participated in the Malmö Diet and Cancer study during 1991–1994. Blood cadmium levels were estimated from hematocrit and cadmium concentrations in erythrocytes. Incident cases of diabetes were identified from national and local diabetes registers.

Results

Cadmium concentrations in blood were not associated with blood glucose and insulin levels at the baseline examination. However, cadmium was positively associated with HbA1c in former smokers and current smokers. During a mean follow-up of 15.2±4.2 years, 622 (299 men and 323 women) were diagnosed with new-onset of diabetes. The incidence of diabetes was not significantly associated with blood cadmium level at baseline, neither in men or women. The hazard ratio (4^th vs 1^st quartile) was 1.11 (95% confidence interval 0.82–1.49), when adjusted for potential confounders.

Conclusions

Elevated blood cadmium levels are not associated with increased incidence of diabetes. The positive association between HbA1c and blood cadmium levels has a likely explanation in mechanisms related to erythrocyte turnover and smoking.     

Changes in ultrastructure and cytochemistry of the agarophyte Gracilaria domingensis (Rhodophyta, Gracilariales) treated with cadmium

The agarophyte macroalgae Gracilaria domingensis (Kützing) Sonder ex Dickie is widely distributed along the Brazilian coast. While this species produces agarana, it is more important in the human diet. Therefore, the present study aimed to evaluate the biological effects of cadmium on its morphology and cellular organization. To accomplish this, the effects of cadmium in apical segments of G. domingensis were examined in vitro. Over a period of 16 days, the segments were cultivated and exposed to photosynthetically active radiation (PAR) at 80 μmol photons m^?2 s^?1, with cadmium treatments in doses of 100, 200 and 300 μM. The samples were processed for light, transmission and scanning electron microscopy. Histochemical analyses included Toluidine Blue for acidic polysaccharides, Coomassie Brilliant Blue for total protein, and Periodic Acidic Schiff for neutral polysaccharides. In all cadmium treatments, cytochemical analysis showed 1) metachromatic granulation in vacuole and lenticular thickness of the cell wall, 2) a higher concentration of cytoplasmic organelles, and 3) an increase in the number of floridean starch grains. Cadmium also caused changes in the ultrastructure of cortical and subcortical cells, including increased cell wall thickness and vacuole volume, as well as the destruction of chloroplast internal organization and increased number of plastoglobuli. In addition, treated plants showed a gradual increase in surface roughness, apparently the result of cadmium absorption. Taken together, these findings strongly suggested that cadmium negatively affects the agarophyte G. domingensis, posing a threat to the vitality of this plant species as a supplement in the human diet.     

Trace metal concentrations in two New Zealand talitrid amphipods: effects of gender and reproductive state and implications for biomonitoring

This is the first in-depth investigation of whether the gender or reproductive state of talitrid amphipods affects the bioaccumulation of trace metals. Concentrations of copper, zinc, and cadmium were measured in the beach flea Transorchestia chiliensis (Milne-Edwards) and the sand hopper Talorchestia quoyana (Milne-Edwards) (Amphipoda: Talitridae) from sites in and near the Avon-Heathcote Estuary, Christchurch, New Zealand. For T. chiliensis, the whole body trace metals concentrations (μg g⁻¹) were generally similar for nonbrooding, brooding, and brooding females that had the embryos removed. Where there were differences between female groups (3 out of 15 samples), concentrations in nonbrooding females were below those for brooding females. The trace metal concentrations of separated embryos did not follow those of their mothers. The body zinc concentration was similar for males and females. For copper and cadmium, body concentrations for females were higher than males at the two most contaminated sites. Cadmium body concentrations were similar between sites, and the lowest concentrations were from amphipods from one of the Estuary sites rather than the reference site. In T. quoyana, the trace metal concentrations in nonbrooding female and male sand hoppers were similar for copper and zinc, but cadmium concentrations were higher in nonbrooding females than in males. Copper and zinc concentrations within amphipod body tissues did not reflect those in the sediment or their food. The implications of these results are discussed in relation to previous studies and the use of beach fleas and sand hoppers as metal biomonitors. The beach flea T. chiliensis is recommended as a suitable trace metal biomonitor in New Zealand coastal waters with the potential to be affected by anthropogenic trace metal contamination.     

Impact of bio-fertilizers and different levels of cadmium on the growth,biochemical contents and lipid peroxidation of Plantago ovata Forsk

Plantago ovata Forsk. (isabgol) is a valuable medicinal plant; its seeds and shell have a significant role in pharmacy as a laxative compound. Increasing soil contamination with cadmium (Cd) is one of the major concerns and is responsible for toxic effects in plants. This investigation was aimed to analyze the role of biofertilizers in alleviation of cadmium stress, given at the rate of 0, 50, and 100 mg kg⁻¹ of soil. The plants of isabgol, were grown in pots with and without application of AM fungi and Azotobacter (alone and combination). Cadmium showed negative effect on growth and biochemical component whereas proline and MDA content increase with increasing cadmium concentration. Addition of bio-fertilizer showed better growth and higher pigment concentration under cadmium stress as compared to the control. The dual inoculation of AM fungi and Azotobacter was found to be the best in reduction of cadmium stress and promotion of growth parameters.     

Effect of heavy metals (Cu,Cd and Pb) on aspartate and alanine aminotransferase in Ruditapes philippinarum (Mollusca: Bivalvia)

The accumulation of cadmium, copper and lead and their effects on aspartate and alanine aminotransferases in digestive gland, gills, foot and soft body in the clam Ruditapes philippinarum were examined. The animals were exposed to different concentrations: Cd (200–600 μg·l⁻¹), Pb (350–700 μg·l⁻¹) and Cu (10–20 μg·l⁻¹) for 7 days. The highest concentrations were found in digestive gland for cadmium and copper, and in gills for lead, and the lowest values were observed in the foot. Aspartate aminotransferase activity (AST), in general, was not inhibited by cadmium, lead or copper during the exposure. Only in clams exposed to cadmium (600 μg·l⁻¹, 7 days) and copper (20 μg·l⁻¹, 5 days) were observed significant differences (P<0.05) in foot and gills, respectively, with respect to control. In the case of alanine aminotransferase activity (ALT), significant differences were observed for cadmium and lead in treated animals with respect to control. With regard to copper, a decrease in ALT was observed in gills and foot exposed to 20 μg·l⁻¹. A significant correlation (P<0.05) was observed between ALT and metal accumulation for cadmium, copper and lead in gills. In the case of soft body, only cadmium and lead showed a significant correlation. In summary, R. philippinarum can be considered a bioindicator species for cadmium and lead accumulation and ALT could be useful as biomarker of sublethal stress for these metals in soft tissues and gills. Only gills can be considered an adequate target tissue for copper.     

Low-level cadmium doses do not jeopardize the insulin secretion pathway of β-cell models until the onset of cell death

BackgroundCadmium is an inescapable environmental pollutant that permeates the food chain and has been debatably associated with diabetes in humans.Purpose and proceduresTo probe the specific impact of low-level cadmium exposure on insulin production, largely sub-cytotoxic (50–500 nM) concentrations of cadmium chloride challenged the INS-1 and MIN6 rodent models of pancreatic β-cells for the longest possible time, up to 4 days, before sub-culturing.Main findingsThe concentration of detectable oxidants, the pattern of the actin cytoskeleton, the translocation of β-catenin, the activity of protein phosphatases, calcium traffic, and the phosphorylation status of several key signaling nodes, such as AMP kinase and mitogen activated kinases including nuclear translocation of Extracellular signal-Regulated Kinase, were all insensitive to the applied very low cadmium doses. Accordingly, low-level cadmium exposure did not alter the insulin secretion ability, the functional hallmark of β-cells, before the onset of cell death.ConclusionsThese data define an operational toxicological threshold for these cellular models of β-cells that should be useful to address insulin secretion and the diabetogenic effects of chronic low-level cadmium exposure in animal models and in humans.     

Aerobic granulation with low strength wastewater at low aeration rate in A/O/A SBR reactor

The formation of aerobic granules with low organic loading synthetic wastewater (150-200 mg L⁻¹ of influent COD, acetate/propionate = 1/3) at low aeration rate (0.6 cm s⁻¹ of superficial gas velocity) had been investigated in the anaerobic/oxic/anoxic SBR. Aerobic granules with smooth surface and compact structure were successfully obtained after 50 days. However, these aerobic granules were unstable when the d(0.9) of granules increased to more than 1 mm. The results suggested that the aerobic granules with small diameter (smaller than 1000 μm) were more favorable for treating the low substrate loading wastewater at the low aeration rate. The cycle test revealed that most of the influent COD was removed at the anaerobic stage. The effluent concentrations of N-NH₄⁺ and P-PO₄³⁻ were lower than 1 mg L⁻¹, and the effluent concentration of nitrate gradually decreased with the granulation. Phosphate accumulating organisms were found to utilize O₂ or NO_x⁻ as electron acceptor for phosphorus removal in the study. Simultaneous nitrogen and phosphorus removal occurred inside the granules.     

Effect of cadmium on enzymatic digestion and sugar transport in the small intestine of rabbit

Cadmium compounds are found widely in our environment: for example, in food, water, soil, and ambient air. The most important exposure route of animals to cadmium in the general environment is via oral exposure. In oral cadmium intoxication, the immediate target organ is the gastrointestinal tract. The aim of the present work was to determine how cadmium acts on the intestinal absorption of sugars and on the sucrase activity through rabbit jejunum, after in vitro administration and/or oral administration of CdCl₂ in drinking water. Results obtained show that cadmium decreasesD-galactose accumulation in the jejunum tissue. This effect seems to be the result of an action mainly located on Na⁺-dependent sugar transport of the mucosal border of the intestinal epithelium, because cadmium seemnnot to modify the sugar diffusion across the intestinal epithelium. Cadmium has also been shown to inhibit the (Na⁺-K⁺)-ATPase activity of the enterocyte, which might explain the inhibition of theD-galactose Na⁺-dependent transport. Nevertheless, a direct action of the cadmium molecule on the Na⁺-dependent carrier cannot be discarded. Cadmium altered the sucrose activity when it was administered in the drinking water for 4 d.     

镉对一株深色有隔内生真菌生长、矿质营养与草酸分泌的影响

【背景】深色有隔内生真菌(dark septate endophyte,DSE)广泛定殖于镉(Cd)污染生境的植物根系,具有增强植物镉耐性的重要生态功能,但人们关于DSE对镉胁迫的生理响应的了解有限。【目的】研究一株DSE嗜鱼外瓶霉(Exophiala pisciphila)对镉胁迫的矿质营养与低分子量有机酸分泌的响应。【方法】采用液体培养法,研究不同浓度(0、25、50、100、200、400 mg/L)镉胁迫对DSE菌丝生长、矿质元素(氮、磷、钾、硫、镁、铁、钙)与镉含量、草酸分泌的影响。【结果】随着镉胁迫浓度增加,菌丝生物量显著下降,降幅为22.8%−90.6%,菌丝的氮、钾和铁含量分别减少26.0%−52.8%、53.8%−92.9%和12.8%−34.3%,而磷、镁和钙含量分别增加15.4%−111.4%、20.4%−31.4%和35.1%−62.5%,硫含量在100 mg/L镉胁迫时增加25.1%。镉胁迫还导致培养液pH值下降,草酸浓度及单位菌丝草酸分泌量显著增加。相关分析发现,菌丝镉含量与硫呈显著负相关(P<0.05),与菌丝钾含量呈极显著负相关(P<0.01),与草酸分泌量呈极显著正相关(P<0.01)。【结论】镉胁迫显著抑制DSE的生长,改变矿质元素的吸收,促进草酸分泌。     

The effect of 20-hydroxyecdysone and protein on granule formation in the in vitro cultured fat body of Drosophila

The larval fat body of Drosophila melanogaster when cultured in a medium containing 20-hydroxyecdysone and foetal calf serum produces protein granules in the cytoplasm in a region-specific manner similar to that found in vivo. If ecdysteroid is omitted from this medium, the tissue continues to produce the granules at the same time, in the same region-specific manner, but in lower amounts. Only the high molecular weight fraction of the calf serum has the granule-inducing effect. Bovine serum albumin, herring protamine and bovine haemoglobin will also induce the granules to form. The degree of granule formation is directly proportional to the concentration of protein in the medium. Protein-free medium produces no granules, and protein concentrations in the medium above 3 mg/ml produce no further increase in granule formation. Although the medium containing foetal calf serum and 20-hydroxyecdysone induces more granule formation than medium containing only serum, the extent of granule formation does not differ at concentrations of hormone above 10^?6 M with any given concentration of serum. A minimal amount of serum (3.75%) permits measuring the effects of 20-hydroxyecdysone at concentrations below 10^?6 M. At this serum level the inducing effects of the hormone could be detected at concentrations of 10^?7 M.