Respiratory impairment in crustaceans and molluscs due to exposure to heavy metals

1. We have assessed, using current literature, the respiratory consequences of water-borne heavy metal exposure in crustaceans and molluscs.2. We suggest that in lethal and sub-lethal concentrations the essential metals Cu and Zn act on the respiratory system primarily by disrupting gill function which results in the development of internal hypoxia, although reparation can be accomplished even at “high” sub-lethal concentrations.3. The more toxic xenobiotes such as Hg (and perhaps to a lesser extent Cd) may interfere with the respiratory system at every level of organisation including cellular respiration itself.     

Trace metals in edible marine molluscs and crustaceans from Lebanon

Samples of the edible tissue of cephalopod molluscs (cuttlefish, squid, octopus) and crustaceans (lobster, shrimp) collected off the coast of Lebanon were found to concentrate similar levels of cadmium, copper, nickel, and chromium. Lead and zinc were highest in the cephalopods and iron was highest in the crustaceans.The molluscs collected from Beirut had higher levels of many metals than those taken from the other locations. The Beirut octopus had higher lead, cadmium, copper, iron, and chromium. Lead, cadmium, and copper were also highest in the Beirut cuttlefish while iron and zinc were elevated. The crustaceans from Beirut showed no strong tendency to concentrate higher metal levels, except for the Beirut lobster which had higher copper than the other samples.In the cuttlefish, the analysis of bone showed generally higher cadmium, zinc, nickel, and chromium but lower copper and iron than the muscle. However, at Beirut, the bone samples had much higher iron. Levels of most metals in the exoskeletons of the lobster and shrimp were quite similar to those in the muscle tissue with the exception of iron in the lobster which was highest in the exoskeleton, and zinc in both crustaceans, which was more highly concentrated in the muscle.     

Developmental inhibition and reproductive potential impairment in Musca domestica L. by heavy metals

Post embryonic development and adult emergence of housefly, M. domestica L. was adversely affected in varying degrees on exposure of larvae to 6 different heavy metals. Of these, salts of mercury, aluminium and cadmium exhibited significant reduction in normal adult emergence. High decline in reproductive potential in terms of female fecundity and egg hatchability was also observed in the F1 progenies of treated larvae. The results are discussed in light of heavy pollution of environment by such contaminants.     

混合暴露条件下近江牡蛎对重金属的积累与释放特征

选择近江牡蛎作为试验生物,研究了混合暴露条件下8种重金属在近江牡蛎体内的积累和释放特征.结果表明: 近江牡蛎对重金属Pb、Cu、Ni、Cd、Cr和Hg有很强的累积能力,可较好地指示溶液中的重金属浓度水平,但对重金属Zn和As的积累能力很小,不能真实反映溶液中重金属Zn和As含量的变化水平.在随后35 d的释放阶段,8种重金属在近江牡蛎体内的含量没有明显变化,表明近江牡蛎对重金属的释放能力较差.双箱动力学模型可较好地反映混合暴露条件下近江牡蛎对重金属的积累特征,但不适合对其释放特征进行描述.     

Endocrine disruption in crustaceans due to pollutants: a review

The main endocrine-regulated processes of crustaceans have been reviewed in relation to the effects of endocrine-disrupting compounds (EDCs). Molting has been shown to be inhibited by several organic pollutants, such as xenoestrogens and related compounds, as well as by some pesticides. Most of these disrupters are thought to interfere with ecdysone at target tissues, although only for a few has this action been demonstrated in vitro. The heavy metal cadmium appears to inhibit some ecdysone secretion. Juvenoid compounds have also been shown to inhibit molting, likely by interfering with the stimulatory effect of methyl farnesoate. A molt-promoting effect of emamectin benzoate, a pesticide, has also been reported. As for reproduction, a variety of organic compounds, including xenoestrogens, juvenoids and ecdysteroids, has produced abnormal development of male and female secondary sexual characters, as well as alteration of the sex ratio. Cadmium and copper have been shown to interfere with hormones that stimulate reproduction, such as methyl farnesoate, as well as with secretion of the gonad inhibiting hormone, therefore affecting, for example, ovarian growth. Several heavy metals were able to produce hyperglycemia in crustaceans during short times of exposure; while a hypoglycemic response was noted after longer exposures, due to inhibition of secretion of the crustacean hyperglycemic hormone. The ecological relevance of EDCs on crustaceans is discussed, mainly in relation to the identification of useful biomarkers and sentinel species. New experimental approaches are also proposed.     

Embryopathies due to spermatozoal impairment in Xenopus laevis.

An in vitro test system, involving gametes of Xenopus laevis has been used to study the effect of antifertility agents upon spermatozoa as manifest in developing embryos. Exposure to either the isomeric forms of dimethylmyleran, methyl methanesulphonate or gamma-radiation led to development of a range of embryopathies, whereas treatment with steroidal drugs or the rodent epididymal chemosterilants alpha-chlorohydrin and trimethylphosphate was compatible with production of apparently normal offspring.     

Neurotoxic and general effects of combined subchronic exposure of rats to insecticides and heavy metals

Three different insecticides: dimethoate, cypermethrin and amitraz were given, alone or combined with the heavy metals Pb, Hg and Cd, to male Wistar rats per os for 12 weeks from their 4th week of life. After the treatment period, the left hemisphere of the rats was exposed in urethane anaesthesia, and spontaneous and evoked cortical activity was recorded from the primary sensory areas. The effects of dimethoate on the spontaneous activity, and of dimethoate and amitraz on the evoked responses, were increased by the metal combination treatment, whereby the metals alone had no effect on the spontaneous and mild effect on the evoked activity. Finally, the animals were dissected, organ weights measured, and relative organ weights calculated. The weight gain of all treated groups was significantly retarded compared to the control. Several organ weights were also significantly reduced, mainly in groups receiving insecticide plus metal treatment. The toxic interactions observed in this work indicate that combined human exposure to environmental pesticide residues and heavy metals may have unexpectedly severe effects.     

Anaerobic metabolism of bivalve molluscs during exposure to air

The anaerobic metabolism of Mytilus edulis, Cardium edule, Scrobicularia plana and Macoma balthica was investigated. On exposure to the atmosphere, all of these species were found to be able to utilise ¹⁴CO₂. This suggests that these species gape during exposure to the atmosphere. A comparative study on the pattern of ¹⁴C incorporation suggests that there is a similarity between M. edulis and S. plana in the extent of the utilization of the succinate pathway during exposure to air. However C. edule and M. balthica were also similar in the extent of utilizing the succinate pathway, even though there were significant species differences between the similar animals. It is suggested that exposure in S. plana represents a stressful situation and that this species might react to this stress by utilizing the succinate pathway. A higher incorporation of radiocarbon into alanine by M. balthica could be due to high activity of the enzymes that control the reactions leading to production of radioactive pyruvate.     

Impact of heavy metals on the trophic activity of daphnia depending on feeding conditions and age of crustaceans

This paper studies how exposure conditions affect the trophic activity of Daphnia crustaceans and their sensitivity to heavy metals. To register the trophic activity of crustaceans, the change in intensity of the zero level of rapid fluorescence in chlorella alga utilized as feed is used. The optimal conditions (stocking density, age of test organisms, feeding schedule, and exposure time) are determined under which a high level of the trophic activity and sensitivity of crustaceans to pollution are registered. An experimental design is suggested in which crustaceans are first exposed to a toxicant and then a suspension of the alga is introduced into a cultivation medium.     

Prevalence of exposure of heavy metals and their impact on health consequences

Even in the current era of growing technology, the concentration of heavy metals present in drinking water is still not within the recommended limits as set by the regulatory authorities in different countries of the world. Drinking water contaminated with heavy metals namely; arsenic, cadmium, nickel, mercury, chromium, zinc, and lead is becoming a major health concern for public and health care professionals. Occupational exposure to heavy metals is known to occur by the utilization of these metals in various industrial processes and/or contents including color pigments and alloys. However, the predominant source resulting in measurable human exposure to heavy metals is the consumption of contaminated drinking water and the resulting health issues may include cardiovascular disorders, neuronal damage, renal injuries, and risk of cancer and diabetes. The general mechanism involved in heavy metal‐induced toxicity is recognized to be the production of reactive oxygen species resulting oxidative damage and health related adverse effects. Thus utilization of heavy metal‐contaminated water is resulting in high morbidity and mortality rates all over the world. Thereby, feeling the need to raise the concerns about contribution of different heavy metals in various health related issues, this article has discussed the global contamination of drinking water with heavy metals to assess the health hazards associated with consumption of heavy metal‐contaminated water. A relationship between exposure limits and ultimate responses produced as well as the major organs affected have been reviewed. Acute and chronic poisoning symptoms and mechanisms responsible for such toxicities have also been discussed.     

Biliary bilirubin in rats and exposure to metals

After cannulation the bile duct of unexposed rats, changes in bilirubin concentration in the samples of bile collected were observed. During the first hour after the cannulation the bilirubin concentration decreased remaining constant until about the 3.-4. hour and then continuously increased upto the 24. hour when the experiment ended. The final concentration was about 4 fold higher than between the 1.-4. hour after the cannulation. This could explain a large variation in values reported by various authors. This fact significantly complicated the studies on effect of exposure to heavy metal salts on changes of bilirubin concentration in bile and relationship among bilirubin concentrations in the bile fractions 1, 2 and 3. In the bile of unexposed rats comparable bilirubin concentrations were found in the bile fractions 1 and 2. The preliminary experiment with HgCl2 application to rats revealed that in the fraction 3 might be a higher bilirubin concentration than in the fractions 1 and 2, the latter ones being lower than in the bile of unexposed rats. The hypothesis was suggested that the bile fraction 3 was composed from yellow pigments liberated from compounds forming the fractions 1 and 2 with additional amount of pigments originated during disturbed protoporphyrin biosynthesis of their degradation by the metals.     

Morpho-functional alterations in lymphocytes and erythrocytes of Japanese quail due to prolonged in vivo exposure to heavy metal complexes

BackgroundLead and cadmium are significant environmental pollutants that cause pathophysiological responses in many organs. Heavy metal absorption into many tissues is very fast due to a pronounced affinity for metallothioneins.MethodJapanese quail were exposed to different concentrations of metals (cadmium 0.20 mg/L and lead 0.25 and 0.50 mg/L) for 20 days. Erythrocytes (normal and hemolyzed) and lymphocytes (normal and altered) were monitored in this study. The analysis observed the percentage of normal and altered cells, as well as erythrocyte surface area. Cell counts were analyzed using light microscopy, while surface area and cytological changes in cells and nuclei were analyzed using licensed software.ResultsDifferent concentrations of metals have caused erythrocyte hemolysis as well as structural and morphological alterations in lymphocytes. Destruction of cell and nucleus membrane, changes in cell size, erythrocyte denucleation and reduced erythrocyte surface area were observed. Cadmium has caused erythrocyte hemolysis (29.30 %) and lymphocyte damage (92.10 %). Higher doses of lead resulted in greater damage to lymphocytes (63 %). Also, treatment with higher dose of lead produced a higher percentage of hemolyzed erythrocytes (19.20 %) in comparison to lower dose (9.90 %).ConclusionThe toxicity of heavy metals leads to reduced maturation of the blast, which causes the appearance of immature cells in peripheral circulation and severe destruction of blood cell membranes. Erythrocyte hemolysis can lead to anemia, while lymphocyte damage can lead to lymphocytopenia.     

Physiological strain due to load carrying in heavy footwear.

To determine the effects of wearing heavy footwear on physiological responses five male and five female subjects were measured while walking on a treadmill (4, 5.25, and 6.5 km.h-1) with different external loads (barefooted, combat boots, and waist pack). While walking without an external load the oxygen uptake, as a percentage of maximal oxygen uptake (%VO2max) of the men increased from 25% VO2max at 4 km.h-1 to 31% VO2max at 5.25 km.h-1 and to 42% VO2max at 6.5 km.h-1. The women had a significantly higher oxygen uptake of 30%, 40%, and 55% VO2max, respectively. In the most strenuous condition, walking at 6.5 km.h-1 with combat boots and waist pack (12 kg), the oxygen uptake for the men and women amounted to 53% and 75% VO2max, respectively. The heart rate showed a similar response to the oxygen uptake, the women having a heart rate which was 15-40 beats.min-1 higher than that of the men, depending on the experimental condition. The perceived exertion was shown to be greatly dependent on the oxygen uptake. From the results a regression formula was calculated predicting the oxygen uptake depending on the mass of the footwear, walking speed and body mass. It was concluded that the mass of footwear resulted in an increase in the energy expenditure which was a factor 1.9-4.7 times greater than that of a kilogram of body mass, depending on sex and walking speed.     

Bacterial sorption of heavy metals.

Four bacteria, Bacillus cereus, B. subtilis, Escherichia coli, and Pseudomonas aeruginosa, were examined for the ability to remove Ag+, Cd2+, Cu2+, and La3+ from solution by batch equilibration methods. Cd and Cu sorption over the concentration range 0.001 to 1 mM was described by Freundlich isotherms. At 1 mM concentrations of both Cd2+ and Cu2+, P. aeruginosa and B. cereus were the most and least efficient at metal removal, respectively. Freundlich K constants indicated that E. coli was most efficient at Cd2+ removal and B. subtilis removed the most Cu2+. Removal of Ag+ from solution by bacteria was very efficient; an average of 89% of the total Ag+ was removed from the 1 mM solution, while only 12, 29, and 27% of the total Cd2+, Cu2+, and La3+, respectively, were sorbed from 1 mM solutions. Electron microscopy indicated that La3+ accumulated at the cell surface as needlelike, crystalline precipitates. Silver precipitated as discrete colloidal aggregates at the cell surface and occasionally in the cytoplasm. Neither Cd2+ nor Cu2+ provided enough electron scattering to identify the location of sorption. The affinity series for bacterial removal of these metals decreased in the order Ag greater than La greater than Cu greater than Cd. The results indicate that bacterial cells are capable of binding large quantities of different metals. Adsorption equations may be useful for describing bacterium-metal interactions with metals such as Cd and Cu; however, this approach may not be adequate when precipitation of metals occurs.     

Respiratory disease in industry due to B. subtilis enzyme preparations

Detergent industry workers are known to become sensitized to enzyme preparations added to the products. In a Canadian plant about 25% of 644 employees exposed to airborne commercial B. subtilis enzyme preparations became sensitized. Skin tests with a number of antigens, including purified enzyme preparations, illustrated differences from person to person in the components to which there was sensitization. The presence of respiratory symptoms related to the industrial exposure was reported much more commonly among sensitized workers. Among employees obliged to miss work, FEV₁ values after 24 months were considerably higher than those obtained during the time of initial difficulties. Blood eosinophilia was observed in sensitized workers. Serum IgG antibodies to the enzyme preparations were demonstrable in most sensitized individuals but did not provide a reliable index of sensitization or of the symptomatic state.     

Resistance to and uptake of heavy metals in mushrooms

Resistance levels to heavy metals in 21 mushrooms obtained mainly from Japan, but also from Thailand, were tested. The mushrooms were 7 Pleurotus species, 2 Pycnoporus and Pholiota species and one each of Agrocybe, Cryptoporus, Coriolus, Inonotus, Lampteromyces, Grifola, Flammulina, Lyophyllum, Agaricus, and Polyporus species. The Pleurotus species strains showed higher resistance to the heavy metals, copper, cadmium, zinc, nickel, cobalt, mercury than the other species. Pleurotus ostreatus exhibited the highest resistance to all these heavy metals. Pholiota species, Flammulina veltipes, Lyophyllum ulmarium, Agaricus bisporus and Polyporus arcularius were rather sensitive to all the metals tested. The accumulation of copper, zinc and cadmium in Pleurotus ostreatus was studied. The uptake of heavy metals into the mycelia of P. ostreatus increased proportionally to an increasing concentration of these metals in the medium.