Correlation of cadmium-induced nephropathy and the metabolism of endogenous copper and zinc in rats

Female Wistar rats were injected (sc) every second day for 8 weeks with Cd (0.25 mg/kg) as CdCl2. After only a 2-week exposure, when cadmium (Cd) concentration in liver was about 13 micrograms/g, ultrastructural examinations revealed some irregular ergastoplasm systems and significant proliferation of smooth endoplasmic reticulum in the hepatocyte ultrastructure. The increase in Zn content occurred simultaneously with the increase in Cd concentration in the liver (Zn to Cd ratio was 1:1). In the kidneys after a 3-week exposure, when Cd concentration was 7 micrograms/g, the concentration of endogenous Cu increased. At the same time the urinary excretion of that metal was considerably higher than that of the control group. In the kidneys after a 4-week exposure, when Cd concentration in this organ exceeded 10 micrograms/g tissue, injured brush border microvilli and swollen mitochondria in the proximal convoluted tubular cells were seen. In renal corpuscules, fusion between the podocyte pedicles was also found. The changes in renal cortex ultrastructure became more pronounced when Cd concentration in kidney was increasing. Necrotic changes in the examined organ were observed when Cd concentration increased to about 30 micrograms/g tissue. The critical concentration in renal cortex of about 200 micrograms/g tissue should be revised. The present margin of safety with regard to risk of renal effects is small.     

Interactions of silver, cadmium, and copper accumulation in green mussels (Perna viridis)

Metal interaction is vital for assessing the use of aquatic organisms in monitoring metal contamination. The present study examined the interactions between Ag and Cd accumulation and between Ag and Cu accumulation in the green mussel (Perna viridis). Accumulation of Ag and Cd in the whole tissue of green mussels exposed to 5 microg/L of Ag and 20 microg/L of Cd for two weeks was independent; however, interaction was observed at the subcellular level. Approximately 25% of Ag shifted from the insoluble fraction (IF) to the metallothionein-like protein in the presence of Cd, which probably resulted from the competition of Cd on IF in the Ag-Cd coexposure. On the other hand, coexposure of the mussels to Ag (5 microg/L) and Cu (30 microg/L) for two weeks increased the Ag and Cu concentrations in the tissue synergistically (two- to fivefold), but Ag and Cu subcellular distributions were similar in the coexposed and the singly exposed mussels. Exposure to Ag alone increased the dietary uptake of Ag by 30%, but the effect was reduced in the presence of Cd. No interaction, however, was observed between uptake rates of metals from the dissolved phase. To conclude, a significant interaction was observed for total Ag and Cu accumulation, but not for total Ag and Cd accumulation, in the mussels. Metal interaction is more likely to be observed at the subcellular level than at the whole-tissue level.     

Immunomodulation the Marine Green Mussel Perna viridis Exposed to Sub-Lethal Concentrations of Cu and Hg

Environmental pollution is a growing concern and, more importantly, pollution of the aquatic ecosystem is alarming. Marine pollution may be one of the reasons for disease incidence in marine organisms, which is caused due to adverse effects of pollutants on the immune system. Bivalves are commonly used as bio-indicators of marine pollution, and immunomodulation due to toxicants is one of the important bio-markers used. Perna viridis too have been used as a bio-indicator, but this study is, to our knowledge, a first report on immunomodulation produced by metals, in P. viridis. Animals were exposed to copper and mercury at their sub-lethal concentrations of 20 μg L⁻¹ and 10 μg L⁻¹, respectively. Immune parameters including phenoloxidase, reactive oxygen species generation, and phagocytosis were monitored. The study period was for 25 days (chronic long-term exposure) and objectives established whether metals produced immunomodulation and to understand the effects of long-term exposure on immunomodulation. Results showed that both metals adversely affected immune parameters studied and, interestingly, there appears to be some level of recovery (depuration) from the toxic effects of metals.     

Modeling of cadmium bioaccumulation in two populations of the green mussel Perna viridis

This study attempted to quantify differences in Cd biokinetics from two populations of green mussels (Perna viridis) from two sites (eastern and western) in Hong Kong with contrasting hydrological conditions. Body Cd concentrations were modeled using a simple biokinetic model coupled with measurements of dissolved Cd concentrations at each site. Mussels collected from the western site had three to six times higher Cd tissue concentration than the eastern population collected during two seasons (summer wet and winter dry), but the salinity was only lower in the western site during the summer. More Cd was distributed in the metallothionein-like and heat-sensitive proteins in the western population than the eastern population, and Cd predominantly was distributed in the insoluble fraction during summer. The Cd uptake rate constant from the dissolved phase was higher in the western population during summer due to a much lower salinity, but was comparable during winter. Dietary uptake of Cd was similar in both populations, and assimilation was lower from ingested radiolabeled seston than from diatoms. Efflux of Cd remained comparable between the two populations from two seasons (0.02-0.03 /d). Kinetic modeling demonstrates that the faster influx of Cd from aqueous phase caused the higher body Cd concentrations in the western population. The predicted Cd concentrations in mussels were comparable to those observed in the field. Our study highlights differences in Cd accumulation kinetics in different populations of mussels likely caused by the different physical environments.     

Metal and oxygen uptake in the green mussel Perna viridis under different metabolic conditions

Coupled respirometric and radiotracer techniques were applied to simultaneously measure the rates of oxygen and metal uptake in the green mussel Perna viridis. This was performed under different metabolic conditions by varying the ambient oxygen partial pressure (P(O2)), temperature, air exposure, and body size. When the mussels were tested under different hypoxic and anoxic conditions, Cd and Zn uptake decreased with decreasing P(O2), accompanied by a decrease in the ventilation activity of mussels. Significant reduction in metal uptake was observed at a P(O2) level of 3 kPa. Under anoxic conditions, the uptake of Cd and Zn was 1.6 to 2.7 times and 2.8 times, respectively, lower than those measured under normoxia. In contrast, both the absorption efficiencies of Cd and Zn and the oxygen extraction efficiency increased significantly with decreasing P(O2). There were significant correlations between the rates of Cd/Zn and O2 uptake by the mussels when quantified under various P(O2) levels. The uptake of Cd and Zn was temperature dependent and increased with temperature over a range of 15 to 30 degrees C. Significant correlations between the rates of Cd/Zn and O2 uptake were also found in the temperature experiments. With reimmersion of mussels after aerial exposure, the mussels experienced an apparent O2 debt. Metal uptake also increased within the first 15 min followed by gradual recovery to the control levels. Similarly, the quantified uptake rates of Zn were significantly correlated with the O2 uptake in experiments with different sizes of mussels. These results strongly suggest that Cd and Zn uptake are coupled with oxygen uptake in the mussels; thus, physiological processes need to be considered in studying metal accumulation.     

The synthesis in vivo of proteins in various tissues in chickens adapted to intermittent feeding

1. Protein synthesis was estimated in vivo in breast (superficial pectoral) and tibia (gastrocnemius) muscles, liver, kidney, pancreas, crop, duodenum, jejunum and ileum, using L-[U-14C]lysine injection. The effect on incorporation of [14C]lysine 1 and 2 h after injection was examined in five chickens adapted or not adapted to intermittent feeding. 2. Incorporation of [14C]lysine into tissue decreased in magnitude in the following descending order: pancreas greater than jejunum, duodenum greater than ileum, crop, liver greater than kidney greater than tibia, breast muscle and blood plasma. 3. The incorporation of [14C]lysine into muscle protein was higher in chicks after 24 h of refeeding than after 24 h of food deprivation. These differences were higher in adapted than in non-adapted birds. On days of refeeding the rate of incorporation exceeded that found in chickens fed ad lib. 4. Bound 14C from lysine in the intestinal segments was less than in control birds after food deprivation and greater after refeeding in non-adapted chicks only. 5. A negative relation was observed between bound and free 14C in muscles and in other tissues. 6. Short- and long-term adaptations to feeding regimens are discussed.     

Benzo[a]pyrene absorption and exposure pathways in the green mussel Perna viridis

The absorption efficiency (AE) of benzo[a]pyrene (BaP), a representative polycyclic aromatic hydrocarbon compound, in the green mussel Perna viridis was measured under different biological and food conditions (body size, food quantity, and food species). Uptake of BaP from the aqueous phase by different species of phytoplankton and green mussels was also experimentally quantified. A bioenergetic-based kinetic model was then used to separate the exposure pathways of BaP accumulation in the green mussels. Our results demonstrated that the AE of BaP in the green mussels ranged between 17 and 47%. Body size did not significantly affect the AE of BaP in the mussels. The AEs increased with a decrease in food availability, largely as a result of lengthening the gut passage of chemicals. The AEs differed by up to 2.3 times (17-39%) among the different food diets tested (four phytoplankton diets and one sediment diet). The BaP associated with the sediment was assimilated least efficiently. The difference in gut passage also appeared to account partially for the difference in AEs observed among different food types. No correlation between the AE and the distribution of BaP in the cytoplasm of phytoplankton cells was found. The concentration factor of BaP measured in four different marine phytoplankton species was in the range of 10(4)-5 x 10(4) (L/kg). The calculated uptake rate constant of BaP in the green mussels was 6.37 L/g/d, and the efficiency of absorption of BaP from the aqueous phase was 6.6 to 8.8%. The model calculation indicated that under most circumstances, >56% of BaP in mussels can indeed be derived from the uptake from the aqueous phase. However, the relative importance of aqueous and dietary exposure can be affected by the variation of AE, mussel's ingestion rate, and concentration of BaP in ingested food particles.     

Stimulation of bile-pancreatic zinc, protein and carboxypeptidase secretion in response to various proteins in the rat

The objective of this study was to determine the rate of bile-pancreatic secretion of zinc, protein and carboxypeptidase (CP) in response to three different dietary proteins, egg white (EW), soy protein isolate (SPI) and casein. The infusion of protein into the duodenum stimulated a significant increase in the secretion rate of zinc, protein and CP in bile-pancreatic juice. There was a high degree of correlation between the concentration of zinc and enzyme activity (CPA and CPB) in bile-pancreatic juice indicating that zinc in bile-pancreatic juice is associated with CP activity. The average secretion rate of zinc, protein and CP during the 1-h period after infusion of protein was significantly greater after SPI infusion than after casein. The bile-pancreatic secretion rate of protein, zinc and CPB in response to EW infusion was consistently intermediate between SPI and casein and did not differ statistically from either. Only CPA secretion rate was significantly greater after EW than after casein. Differences in protein digestibility appear to account for the greater pancreatic response to SPI, and this factor may be important in understanding the effect of protein source on zinc bioavailability.     

Prevention of cadmium-induced sterility by zinc in the male rat

The potential of zinc (Zn) to antagonize the adverse effects of cadmium (Cd) on the male reproductive processes was studied. A significant reduction in the weights of the testis and epididymis, the testicular sperm population and oligospermia to azoospermia in the epididymis was recorded in rats treated once s.c. with 2 mg/kg Cd and sacrificed 20 days later. This was accompanied by a significantly reduced serum T and a loss of fertility. Administration of a single s.c. injection of Zn (80 mg/kg) did not alter significantly any of the reproductive parameters studied. On the other hand, Zn given $\text{1}\text{2}$ to 2 h after Cd resulted in partial recovery. Organ weights and sperm population in these groups were maintained and the fertility rate was 67% and 50% at 5 and 20 days as compared to 67% and 0% at corresponding period in Cd-exposed males. The protective effect diminished when Zn was given more than 2 h after Cd exposure. The most effective regimen of Zn therapy was an administration of a total dose of 80 mg/kg Zn given in 3 injections (15 mg/kg before, 50 mg/kg at the time and 15 mg/kg 2 h after Cd). The results provide evidence that Zn, if given before or within 2 h of Cd exposure, is capable of at least partially reversing its deleterious effects on spermatogenesis, steroidogenesis and fertility of the male rat.     

Cholesterol contents of various tissues of chickens with exogenous or endogenous hypercholesteremia.

Cholesterol contents of 16 different tissues were determined in 12 normal roosters, 12 roosters with diet-induced, exogenous hypercholesteremia, 10 actively laying hens with minimal endogenous hypercholesteremia, and 12 nonlaying hens with hereditable extreme hyperlipidemia. The tissue cholesterol contents of the normal roosters were strikingly similar to that of the corresponding tissues of the mammals except for a low cholesterol content of the brain in chickens. The hypercholesteremia in the roosters fed a 2% cholesterol diet for 2 months was associated with an increase of cholesterol content in all tissues except the brain, muscle, and adipose tissue. The actively laying hens, on the other hand, had a decreased cholesterol content in most tissues, despite the persistence of a minimal hypercholesteremia for 18 months and significant aortic cholesterol accumulation with mild atherosclerosis. The nonlaying hens developed extreme hypercholesteremia and severe atherosclerosis but only a moderately expanded cholesterol pool in most tissues. The results indicated a remarkable difference in tissue response to diet-induced exogenous hypercholesteremia and endogenous hyperlipidemia associated with laying activity in chickens and the propensity of their aortas to accumulate excessive cholesterol in the presence of either endogenous or exogenous hyperlipidemia.     

Antioxidant responses and bioaccumulation in green-lipped mussels (Perna viridis) under acute tributyltin chloride exposure

Green-lipped mussels (Perna viridis) were exposed to waterborne tributyltin chloride (TBTCl) at different concentrations (0.2, 0.4 and 0.8 μg L⁻¹) for up to 72 h. Accumulated TBTCl in Perna viridis correlated linearly with the exposure concentrations of 0.2 μg L⁻¹(R² = 0.772), 0.4 μg L⁻¹(R² = 0.952), and 0.8 μg L⁻¹(R² = 0.909). The results of superoxide dismutase (SOD), glutathione peroxidase (GPx) and malondialdehyde (MDA) all decreased in gill tissues after 24 h of exposure, but the hepatic SOD and the hepatic GPx showed either little or no effect on exposure of TBTCl solutions. Analysis using the Spearman rank correlation coefficient showed the hepatic GPx activity appeared to have a significant negative correlativity (R_s = −0.42) with the exposed TBTCl concentrations, and the hepatic MDA was significantly negatively correlated (R_s = −0.33) with the tissue TBTCl concentrations. Conversely, a significant positive correlation (R_s = 0.60) was shown between the gill MDA contents and exposure time. This study illustrates oxyradical scavenger GPx best correlated with stress level of pollutants among the various antioxidant parameters.     

Nutritional composition of three estuarine bivalve mussels,Perna viridis,Donax cuneatus and Meretrix meretrix

The present study determined the nutrient composition of three bivalve mussels. The biochemical constituents (protein, carbohydrate, lipid and vitamins), minerals (iron, copper, zinc, calcium, magnesium, and manganese) and carbon, nitrogen and calorific values were evaluated. There was a high degree of variation in biochemical constituents and mineral components among the tested mussels. Perna viridis exhibited good nutritional composition when compared with Donax cuneatus and Meretrix meretrix. The results of this study showed that the samples possessed appreciable quantities of all the dietary elements tested, which could make them partial or complete substitutes for conventional seafood.     

Nutritional composition of three estuarine bivalve mussels, Perna viridis, Donax cuneatus and Meretrix meretrix

The present study determined the nutrient composition of three bivalve mussels. The biochemical constituents (protein, carbohydrate, lipid and vitamins), minerals (iron, copper, zinc, calcium, magnesium, and manganese) and carbon, nitrogen and calorific values were evaluated. There was a high degree of variation in biochemical constituents and mineral components among the tested mussels. Perna viridis exhibited good nutritional composition when compared with Donax cuneatus and Meretrix meretrix. The results of this study showed that the samples possessed appreciable quantities of all the dietary elements tested, which could make them partial or complete substitutes for conventional seafood.     

Iron, copper and zinc metabolism of rats fed various levels and types of tea

The effects of tea and components in tea on mineral metabolism were investigated in a series of studies. In studies A and B weanling rats were fed diets containing various levels (0, 0.35, 1.17 or 3.50%) of a commercially prepared instant tea and diets containing 0 or 1.17% catechin. In study C anemic rats were fed diets containing 0 or 2.31% desiccated green or black tea infusions for 23 d. In study D rats were fed a diet containing 2.31% desiccated black tea infusions for 16 d, were fed the tea-containing diet in a single meal labeled with 59Fe or were given black tea infusions as their sole fluids. Rats fed diets containing 2.31% green or black tea or given fluid tea had elevated hematocrits but experienced minimal changes in tissue iron levels or in iron absorption; this is counter to conclusions from studies in which iron absorption was monitored indirectly. Ingestion of instant or black tea consistently elevated liver copper levels; this may be part of the mechanism by which hematological variables were affected. Although the green tea contained significant amounts of aluminum, rats fed the tea did not accumulate aluminum in their bones.     

Micronucleus induction in gill cells of green-lipped mussels (Perna viridis) exposed to mixtures of polycyclic aromatic hydrocarbons and chlorinated pesticides

Different groups of green-lipped mussels (Perna viridis) were exposed to the same net amount of a genotoxicant mixture of four polycyclic aromatic hydrocarbons ([PAHs]; anthracene, fluoranthene, pyrene, and benzo[a]pyrene) and four organochlorine pesticides ([OCs]; alpha-hexachlorocyclohexane (HCH), aldrin, dieldrin, and p,p'-DDT) for four weeks under different regimes that simulated various scenarios of fluctuating toxicant levels in the marine environment. Micronucleus (MN) formation in gill cells was studied at the end of each week. Micronucleus frequencies increased with continual addition of genotoxicants, and did not diminish significantly under conditions of either gradually decreasing concentrations or cessation of exposure for one to two weeks, suggesting that the MN response may persist over relatively long exposure periods. An almost two-fold higher mean MN frequency was recorded in a chronic exposure group than in an acute group that had received the same net nominal dose of genotoxicants, indicating that chronic exposure may lead to a greater genotoxic impact than acute exposure. The results suggested that in field studies, MN response should be monitored at multiple time points in order to elucidate the effects of potentially fluctuating toxicant levels. Finally, MN formation was positively correlated with both nominal contaminant levels and tissue levels of the genotoxicants. These findings suggest that MN responses can be a sensitive indicator of exposure to relatively low levels of genotoxicants and that MN response in mussel gill cells can be a stable biomarker of genotoxicity.     

Uptake and depuration of paralytic shellfish toxins in the green-lipped mussel, Perna viridis: a dynamic model

Uptake and depuration of paralytic shellfish toxins in the green-lipped mussel, Perna viridis, were investigated by exposing the mussels to dinoflagellates (Alexandrium tamarense, ACTI01) under laboratory conditions for 8 d, then depurating them in clean seawater for 14 d. First-order linear differential equations were set up for five tissue compartments: Viscera, gill, hepatopancreas, adductor muscle, and foot. The solutions to these equations were used to fit the experimental data. We then estimated the parameters governing the model, which depend on the elimination rate from each compartment and the transfer coefficient between compartments. An assumption of the model is that the gills transport the dinoflagellates directly to the mouth and then to the viscera, where the ingested cells are broken down, releasing the toxins. The toxins absorbed are transferred to other tissues. During the uptake phase, the transfer coefficients from viscera to gill, hepatopancreas, adductor muscle, and foot were 0.03, 0.24, 0.01, and 0.004 per day, respectively. During the depuration phase, the transfer coefficients were 0.01, 0, 0.01, and 0.003 per day, respectively. In terms of the anatomical distribution of N-sulfocarbamoyl-11-hydroxysulfate (C2) toxins in various tissues, viscera and hepatopancreas contained the highest percentages (47-74% and 8-41%, respectively). Together, these two tissue compartments accounted for 71 to 96% of all C2 toxins present. The biokinetic model allows a quantitative prediction of C2 toxins in whole ussel as well as individual tissue compartments based on the density estimates and toxin load of dinoflagellate cells in the surrounding waters over time.     

Crystalline style and tissue redistribution in Perna viridis as indicators of Cu and Pb bioavailabilities and contamination in coastal waters

The concentrations of Cu, Pb, and Zn in the crystalline style (CS) and in the remaining soft tissues (ST) of the green-lipped mussel Perna viridis from 10 geographical sites along the coastal waters off peninsular Malaysia were determined. The CS, compared with the remaining ST, accumulated higher levels of Cu in both contaminated and uncontaminated samples, indicating that the style has a higher affinity for the essential Cu to bind with metallothioneins. The similar pattern of Cu accumulation in the different ST of mussels collected from clean and Cu-contaminated sites indicated that the detoxification capacity of the metallothioneins had not been overloaded. For Pb, higher levels of the metal in the CS than in the remaining ST were found only in mussels collected from a contaminated site at Kg. Pasir Puteh. This indicated a tissue redistribution of Pb due to its binding to metallothioneins for Pb detoxification and the potential of the CS as an indicator organ of Pb bioavailability and contamination. For Zn, the above two phenomena were not found since no obvious patterns were observed (lower levels of Zn in the CS than in the remaining ST) in contaminated and uncontaminated samples due to the mechanism of partial regulation. Generally, all the different STs studied (foot, mantle, gonad, CS, gill, muscle, and byssus) are good biomonitoring tissues for Cu and Pb bioavailabilities and contamination. Among these organs, the CS was found to be the best organ for biomonitoring Cu. The present data also suggest the use of the tissue redistribution of Pb in P. viridis as an indicator of Pb bioavailability and contamination in coastal waters.