Effect of dietary inclusion of goat milk on the bioavailability of zinc and selenium in rats

The effects of dietary inclusion of freeze-dried goat and cow milk on the utilization of zinc and selenium, and on the metabolic fate of zinc, were studied in transected (control) and resected rats (resection of 50% of the distal small intestine). Intestinal resection reduced the apparent digestibility coefficient and zinc retention in the cow milk diet, whereas these biological indices were similar in transected (control) and resected rats with standard (without milk) and goat milk diets. The apparent digestibility coefficient and retention of selenium were not affected by intestinal resection in the animals fed with the three diets studied. In transected (control) and resected rats, the apparent digestibility coefficient and retention of zinc and selenium were higher for the goat milk diet than for the other two diets. Zinc deposits in the organs, expressed as microg/g dry weight were in order of decreasing concentrations: femur, testes, sternum, liver, kidney, heart, spleen, longissimus dorsi muscle and brain. Deposits were greatest with the goat milk diet, followed by the standard diet and were lowest for the rats given the cow milk diet, both for transected (control) and resected animals. We conclude that consumption of the goat milk diet produces a greater bioavailability of zinc and selenium and a greater deposit of zinc in key organs, for both the transected (control) and the resected rats, with respect to the standard diet and the cow milk diet.

Glycomacropeptide and alpha-lactalbumin supplementation of infant formula affects growth and nutritional status in infant rhesus monkeys

BACKGROUND

Advances in dairy technology make it possible to enrich infant formula with specific bovine milk components that may enhance nutrient status. Glycomacropeptide, a carbohydrate-rich casein peptide, may increase absorption of calcium, iron, or zinc. alpha-Lactalbumin, a major breast-milk protein, may contribute to a balanced amino acid pattern and increase calcium and zinc absorption.

OBJECTIVE

We determined the effects of glycomacropeptide- and alpha-lactalbumin-supplemented infant formula on growth; trace mineral status; iron, zinc, and calcium absorption; and plasma amino acid, blood urea nitrogen, and plasma insulin concentrations.

DESIGN

Infant rhesus monkeys (n = 5 infants per group) were breastfed or fed control or alpha-lactalbumin- or glycomacropeptide-supplemented formula from birth to 4 mo of age. Hematologic measures and growth were assessed monthly. Mineral absorption was measured with radioisotopes and whole body counting.

RESULTS

Infants fed glycomacropeptide had higher food intake than did other formula-fed infants. Infants fed glycomacropeptide or control formula had higher hematocrit values than did infants that were breastfed or fed alpha-lactalbumin. Infants fed glycomacropeptide or control formula had higher plasma zinc and zinc absorption than did breastfed infants. Where differences were observed, breastfed infants and infants fed alpha-lactalbumin had similar plasma essential amino acid and insulin profiles, which were different from those of infants fed glycomacropeptide or control formula.

CONCLUSIONS

Glycomacropeptide- or alpha-lactalbumin-supplemented formula has no adverse effects on nutritional status in infant monkeys. Glycomacropeptide supplementation increases zinc absorption, which may permit the reduction of formula zinc concentrations, and alpha-lactalbumin supplementation promotes a plasma amino acid pattern similar to that of breastfed infant monkeys.

Accumulation and elimination of cadmium and zinc in the Asian periwinkle Littorina brevicula

To elucidate the differences between the detoxification mechanisms of essential metal (Zn) and non-essential metal (Cd) in Littorina brevicula that is highly resistant to a wide range of heavy metal concentrations, Asian periwinkles were exposed to Cd (400 microg/L), Zn (3000 microg/L) and a mixture of both metals. We examined metal accumulation, elimination and subcellular distribution for binding to proteins. The metal concentration in L. brevicula increased gradually with exposure time (up to 70 days), following which accumulated levels reached saturation point. The accumulated Zn content was increased in the presence of Cd, while Cd uptake was decreased when Zn was present. During the depuration period (42 days), Cd was not removed from periwinkles, while Zn was eliminated in a rate of 2.19 microg Zn g(-1) day(-1). This elimination rate was particularly high on exposure to the metal mixture (3.80 microg Zn g(-1) day(-1)). Subcellular distribution studies on Cd and Zn revealed that most Cd (80%) was bound to cytosolic ligand, while more than 75% Zn was distributed in the membrane (insoluble) fraction. An additional difference in sequestering of metal in the cytosol was noted between Cd and Zn; most Cd in the cytosol was bound to metallothionein-like cadmium binding protein, MBP-1 (9.8 kDa), while the profile for Zn distribution revealed the presence of four Zn-binding ligand peaks, specifically, HMW (60 kDa), MBP-1 (9.8 kDa), MBP-2 (5 kDa) and LMW (<1 kDa). Our data confirm that metallothionein-like cadmium binding protein, MBP-1, has the same affinity for Zn, while MBP-2 displays comparatively higher affinity for Zn than Cd.

Root growth and metal uptake in four grasses grown on zinc-contaminated soils

Depth and area of rooting are important to long-term survival of plants on metal-contaminated, steep-slope soils. We evaluated shoot and root growth and metal uptake of four cool-season grasses grown on a high-Zn soil in a greenhouse. A mixture of biosolids, fly ash, and burnt lime was placed either directly over a Zn-contaminated soil or over a clean, fine-grained topsoil and then the Zn-contaminated soil; the control was the clean topsoil. The grasses were 'Reliant' hard fescue (Festuca brevipila R. Tracey), 'Oahe' intermediate wheatgrass [Elytrigia intermedia (Host) Nevski subsp. intermedia], 'Ruebens' Canada bluegrass (Poa compressa L.), and 'K-31' tall fescue (Festuca arundinacea Schreb.). Root growth in the clean soil and biosolids corresponded to the characteristic rooting ability of each species, while rooting into the Zn-contaminated soil was related to the species' tolerance to Zn. While wheatgrass and tall fescue had the strongest root growth in the surface layers (0-5 cm) of clean soil or biosolids, wheatgrass roots were at least two times more dense than those of the other grasses in the second layer (5-27 cm) of Zn-contaminated soil. When grown over Zn-contaminated soil in the second layer, hard fescue (with 422 mg/kg Zn) was the only species not to have phytotoxic levels of Zn in shoots; tall fescue had the highest Zn uptake (1553 mg/kg). Thus, the best long-term survivors in high-Zn soils should be wheatgrass, due to its ability to root deeply into Zn-contaminated soils, and hard fescue, with its ability to effectively exclude toxic Zn uptake.

Intestinal zinc uptake in two marine teleosts, squirrelfish (Holocentrus adscensionis) and gulf toadfish (Opsanus beta)

Zinc is a vital micronutrient, yet as an environmental toxicant it can be deleterious to aquatic organisms such as fish. Consequently, the study of zinc uptake mechanisms is essential for understanding nutrition, toxicity, and metabolism of this metal. Intestinal zinc uptake was studied in two marine teleosts, using both in vitro (in vitro perfusion and intestinal sacs) and in vivo techniques (in situ bolus). Female squirrelfish (Holocentrus adscensionis) exhibited significantly increased epithelial zinc uptake associated with enhanced hepatic zinc accumulation. This confirms this zinc-hyperaccumulating teleost as a potential model of zinc absorption. Intestinal zinc uptake in the gulf toadfish (Opsanus beta) was biphasic with respect to zinc concentration (0.3-500 microM), exhibiting both saturable and passive uptake components. In both species, the passage of zinc into the postintestinal compartment was highly dependent on technique. Decreased proportions of postintestinal zinc in vivo, coupled with concentration-dependent distribution of zinc accumulation, suggested mechanisms may act to control the movement of zinc into the circulation. In addition, the results of this study were used to reinterpret previous findings of zinc uptake in freshwater fish and allowed a critique of techniques used to study intestinal metal uptake.

Zinc inhibition of cellular energy production: implications for mitochondria and neurodegeneration

An increasing body of evidence suggests that high intracellular free zinc promotes neuronal death by inhibiting cellular energy production. A number of targets have been postulated, including complexes of the mitochondrial electron transport chain, components of the tricarboxylic acid cycle, and enzymes of glycolysis. Consequences of cellular zinc overload may include increased cellular reactive oxygen species (ROS) production, loss of mitochondrial membrane potential, and reduced cellular ATP levels. Additionally, zinc toxicity might involve zinc uptake by mitochondria and zinc induction of mitochondrial permeability transition. The present review discusses these processes with special emphasis on their potential involvement in brain injury.

Trace mineral bioavailability in ruminants

Absorption of selenium and copper is much lower in ruminants than in nonruminants. The low absorption of these minerals in ruminants is due to modifications that occur in the rumen environment. Selenium bioavailability is reduced by high dietary sulfur and the presence of cyanogenetic glycosides in certain legumes. Feeding organic selenium from selenomethionine or selenized yeast results in much higher tissue and milk selenium concentrations than are obtained with selenite. High dietary molybdenum in combination with moderate to high dietary sulfur results in formation of thiomolybdates in the rumen. Thiomolybdates greatly reduce copper absorption, and certain thiomolybdate species can be absorbed and interfere systemically with copper metabolism. Independent of molybdenum, high dietary sulfur reduces copper absorption perhaps via formation of copper sulfide. High dietary iron also reduces copper bioavailability. Dietary factors that affect bioavailability of zinc in ruminants are not well defined. Phytate does not affect zinc absorption in ruminants because microbial phytase in the rumen degrades phytate. Manganese is very poorly absorbed in ruminants, and limited research suggests that high dietary calcium and phosphorus may reduce manganese absorption.

The key role of metallothioneins in the bivalve Corbicula fluminea during the depuration phase, after in situ exposure to Cd and Zn

An experimental study of the role of metallothioneins (MTs) in Cd and Zn depuration processes in the freshwater bivalve Corbicula fluminea was conducted after in situ exposure on the river Lot (France). Specimens of adult C. fluminea were first transplanted from a lacustrine reference site to a polymetallic polluted station (Bouillac, (B)) for a 42-days' exposure period from September to November 1996. They were then depurated after transfer to the laboratory, and were sub-sampled periodically until May 1997. During the first phase, MT concentrations measured with the Mercury-Saturation Assay were induced for a factor of 3.5 compared with time 0, whereas metal uptake showed accumulation factors of 17 and 4 for Cd and Zn, respectively. During the depuration phase, Cd and Zn concentrations decreased by 18 and 70%, respectively, giving estimated biological half-lives of 500 and 40 days. During the same period, MT concentrations decreased by 37% after transfer under unpolluted conditions, especially between 0 and 3 days, suggesting that MTs play a predominant role in Cd depuration. The quantity of Cd sequestered by the MT fraction, after size-exclusion liquid chromatography, represents on average 40% of the total Cd bioaccumulated in the soft body of the molluscs, compared with only 4-9% for total accumulated Zn. This essential metal was principally bound to low molecular weight proteins, which represented 20% of total Zn. Furthermore, it was observed that MTs had a key role in Cd remanence in the bivalves, and it was also reported that other proteins or small peptides were involved in the depuration of Zn.

The uptake of Cd, Cr, and Zn by the macroalga Enteromorpha crinita and subsequent transfer to the marine herbivorous rabbitfish, Siganus canaliculatus

Marine macroalgae can appreciably accumulate metals out of seawater and are the principle food source for marine herbivorous fish, thus playing an important role in introducing metals into marine food webs. There have been few experimental studies on metal transfer from macroalgae up the trophic chain. In this study, we examined the assimilation efficiencies (AEs) of Cd, Cr, and Zn in the rabbitfish, Siganus canaliculatus, which feeds on the macroalga Enteromorpha crinita. The influences of metal concentration and nutrient conditions in the macroalga, and starvation on the assimilation of metals in fish were investigated. The macroalgae were radiolabeled by direct exposure to radiotracers in the dissolved phase. The uptake of metals in the macroalgae proceeded linearly and was directly proportional to the metal concentration in the ambient seawater. Ammonium and nitrate enrichment significantly increased the accumulation of Cd by the macroalgae, whereas Cr accumulation was not influenced by nutrient enrichment. The metal concentrations in the macroalgae did not have any effect on metal assimilation in the rabbitfish. The measured AEs of the metals were generally higher in starved rabbitfish than in fed fish, probably as a result of the prolonged retention of metals in the gut of fish. Rabbitfish fed macroalgae that had been previously exposed to ammonium or nitrate addition decreased their assimilation of Cd and Zn, but not Cr. Phosphate enrichment did not have any significant effect on metal AE in the rabbitfish. Our study demonstrated that marine herbivorous fish can appreciably assimilate trace metals from marine macroalgae and that trophic transfer should be considered as a source for metal accumulation in fish. Nutrient condition and starvation do have considerable effects on the AEs of Cd and Zn in rabbitfish that are fed macroalgae.

Accumulation of lead, zinc, and cadmium in a wild population of Clethrionomys glareolus from an abandoned lead mine

Lead, zinc, and cadmium were determined in a range of tissues from wild populations of bank voles (Clethrionomys glareolus) trapped on an abandoned metalliferous mine site and a reference site. Estimated dietary intakes indicated that animals were exposed to elevated levels of all three metals at the mine site, and this was generally reflected in metal residues in body tissues. Lead concentrations were significantly higher in all tissues of animals from the mine compared to the reference site, while Cd was higher only in the kidney. There was evidence of age-accumulation (using total body weight as an index of age) of Cd in both the liver and kidney of mine site animals but no evidence of such accumulation of lead in bone. In contrast to Cd and Pb, Zn was lower in the tissues of mine site animals compared to the reference site. Based on critical tissue concentrations, the ecotoxicological risk to a wild population of bank voles (Clethrionomys glareolus), associated with total substrate levels of 1 microg g(-1) dry weight Cd and 700 microg g(-1) dry weight Zn at this mine site is negligible, but that associated with 4000 microg g(-1) dry weight Pb may be considered significant.

Applying foraminiferal stratigraphy as a biomarker for heavy metal contamination and mining impact in a fiord in West Greenland

Sulphidic mine waste disposed in marine environments constitutes an environmental risk to aquatic life due to potential uptake and accumulation of heavy metals in biota. Fiord sediments near the former Black Angel Mine in West Greenland are contaminated by lead and zinc as a result of submarine tailings disposal in 1973-1990. In 1999 cores were taken up to 10 km away from the disposal area. Analyses include heavy metals, radiochemical dating (210Pb) and high-resolution foraminiferal stratigraphy. The mining operation resulted in significant changes in the assemblage composition. In addition, up to 20% of the Melonis barleeanus population found in sediment deposited during nearby tailings disposal was deformed compared to a natural background of less than 5%. Throughout cores representing the last 100 years of sedimentation, the total numbers and frequency of morphological abnormalities among M. barleeanus revealed some correlation with heavy metals concentrations (up to r2 = 79%). We conclude that abnormalities among foraminifera may represent a useful biomarker for evaluating trends in the biological impact resulting of submarine tailings disposal as well as long-term environmental impact and subsequent recovery.

Effects of mining activities on heavy metal concentrations in water, sediment, and macroinvertebrates in different reaches of the Pilcomayo River, South America

From 1997 until 1999 the extent and the ecological effects of zinc, copper, lead, and cadmium pollution were studied in different reaches of the South American Pilcomayo River. A comparison of metal concentrations in water, sediment, and chironomid larvae, as well as the diversity of macroinvertebrate species, was made between sites near the origin of the Pilcomayo River, with hardly any mining activities, sites in the Potosí region, with intensive mining, and sites located 500 km or further downstream of Potosí, in the Chaco plain. Samples were also collected in an unpolluted river (Cachi Mayu River) and in the Tarapaya River, which is strongly contaminated by mine tailings (1000 tons a day). The upper parts of the Pilcomayo River are strongly affected by the release of mine tailings from the Potosí mines where mean concentrations of lead, cadmium, copper, and zinc in water, filtered water, sediment, and chironomid larvae were up to a thousand times higher than the local background levels. The diversity of the benthic macroinvertebrate community was strongly reduced in the contaminated parts; 97% of the benthic macroinvertebrates consisted of chironomid larvae. The degree of contamination in the lower reaches of the river, however, was fairly low because of sedimentation processes and the strong dilution of mine tailings with enormous amounts of clean sediment from erosion processes. Analysis of sediment cores from the Ibibobo floodplain, however, reveal an increase of the heavy metal concentrations in the lower reaches since the introduction of the contaminating flotation process in the mine industry in 1985.

Sustained release of human growth hormone from microcapsules prepared by a solvent evaporation technique

Biodegradable microcapsules for sustained release of recombinant human growth hormone (rhGH) were prepared by a solid-in-oil-in-water (S/O/W) emulsion solvent evaporation technique using lyophilized protein microparticles. The minimum mean particle size of rhGH in S/O dispersions was 2.8-3.0 microm when ammonium acetate was added at molar ratios of 10-20 times against rhGH. High entrapment of rhGH in microcapsules was achieved by incorporating rhGH powder with a smaller particle size obtained by lyophilizing with ammonium acetate. As the particle size of rhGH decreased, the in vivo initial release decreased, while subsequent serum levels of rhGH in sustained release phase were higher. Addition of zinc oxide to microcapsules resulted in higher serum levels than those prepared without zinc oxide, suggesting a stabilizing effect of zinc oxide after subcutaneous injection into rats. The release profile of rhGH from microcapsules was controllable by selecting the proper copoly(DL-lactic/glycolic)acid (PLGA) with L/G ratio and molecular weight. Utilization of rhGH powder with a smaller particle size obtained by lyophilizing with ammonium acetate is essential for preparation of microcapsules with high entrapment and well-controlled sustained release profile with small initial release.

Activity of glutathione S-transferase in Spodoptera exigua larvae exposed to cadmium and zinc in two subsequent generations

The aim of our study was to establish changes in activity of important in detoxification enzyme-glutathione S-transferase (GST): in alimentary tract, fat body and Malpighian tubules of Spodoptera exigua larvae being under cadmium and zinc exposure through the first as well as the second generation. There was registered enhancement of the enzyme activity in the fat body and the Malpighian tubules caused by zinc as well as its decrease in the Malpighian tubules under cadmium action. Amounts of metals in the alimentary tract were either several times higher than in the diet ingested by larvae or than in the fat body. Metal concentration in the fat body correlated with the level of the enzyme activity (positive correlation for zinc and negative for cadmium). The effect of metal action differentiated dependently on time exposition.

Cadmium interaction with microalgal cells, cyanobacterial cells, and seaweeds; toxicology and biotechnological potential for wastewater treatment

The accumulation of cadmium (Cd) by Tetraselmis chuii and Spirulina maxima was studied with dead and growing cells. Results indicated that the 2 microorganisms accumulated Cd by 2 different means according to the mechanisms involved-metabolism-dependent or metabolism-independent sorption. The mechanism involved in Cd accumulation on Tetraselmis chuii was restricted to surface phenomena, while in Spirulina maxima, Cd was accumulated on different layers of the cyanobacterium surface. In order to select a suitable immobilization support for the cells, several seaweeds were tested. Two types of seaweed were selected for experiments, using a small continuous pilot unit: Sargassum sp., a strong Cd adsorber, and Ulva sp., a poor one. The column reactors of the continuous system were filled with the algal supports and covered with dense microbial biofilms of Tetraselmis chuii or Spirulina maxima. The results obtained proved the success of the association between living microbial cells and dead seaweeds for operation of the continuous system.

Failure of the biotic ligand and free-ion activity models to explain zinc bioaccumulation by Chlorella kesslerii

Zinc accumulation by Chlorella kesslerii (Chlorophycee) was studied for [Zn2+] ranging from 4 pM to 1 mM. A first-order uptake flux as predicted by the free ion activity model (FIAM) and the biotic ligand model (BLM) was not observed. Furthermore, when algae were preconditioned in slightly limiting (10 pM) versus optimal (1 nM) free zinc concentrations, the internalization flux increased and was nearly constant over the range of [Zn2+] examined. This observation was attributed to the synthesis of membrane-bound zinc transporters. Neither solution Zn chemistry nor surface-bound Zn was a good predictor of Zn uptake fluxes. Several hypotheses were examined to explain the failure of the steady-state uptake models. Although zinc excretion and a Zn diffusion limitation were observed, neither result could explain the majority of observed deviation from the models. Bioaccumulation experiments performed with inhibitors (vanadate and carbonyl cyanide m-chlorophenylhydrazone [CCCP]) demonstrated clearly that zinc transport is an energy-dependent process in Chlorella kesslerii. The presence of an active transport signifies that Zn uptake may function independently of the electrochemical Zn gradient and that, in some cases, both uptake fluxes and receptor-bound Zn may be independent of solution chemistry.

Effects of dissolved metals and other hydrominerals on in vivo intestinal zinc uptake in freshwater rainbow trout

For aquatic organisms, zinc is both an essential nutrient and an environmental contaminant. The intestine is potentially the most important route of zinc absorption, yet little is known regarding this uptake pathway for zinc in fish. A recently developed in vivo perfusion system was used to investigate the effect of luminal composition upon intestinal zinc uptake in freshwater rainbow trout (Oncorhynchus mykiss). Perfusate cadmium and copper had specific, yet distinct, antagonistic effects upon lumen to tissue zinc movement. Copper significantly reduced the proportion of zinc taken up from the perfusate, and concomitantly limited the passage of zinc into the circulation and beyond. Conversely, cadmium decreased subepithelial zinc accumulation, with rates falling to 29 nmol g(-1) h(-1) from the control (zinc alone) values of 53 nmol g(-1) h(-1). Calcium had a similar action to copper, also reducing post-intestinal zinc accumulation from 0.06 to 0.02 nmol g(-1) h(-1), an effect attributed to interactions between calcium and the zinc uptake pathway. In addition to these effects, luminal composition also had a marked influence upon epithelial response to zinc. Calcium, copper and magnesium all greatly reduced zinc-induced mucus secretion. Cadmium, a toxic metal, significantly increased mucus secretion. It is proposed that these modifications were related to the essentiality of each element, and their potential mechanisms of uptake. Despite changes at the epithelium, the post-epithelial accumulation of zinc was dependent mainly upon the nature of the competing cation. Intestinal saline ion substitution experiments suggested a potential link of potassium ion efflux to zinc uptake. The effect of pH buffering of luminal solutions was also investigated.

Aerobic granules: a novel zinc biosorbent

AIMS

Aerobic granules are aggregates with a compact and porous microbial structure. In view of the potential use of aerobic granules as biosorbents for Zn(II) removal from industrial wastewater, this study investigated the effects of initial Zn(II) and aerobic granule concentrations on the kinetics of Zn(II) biosorption on the aerobic granule surface.

METHODS AND RESULTS

Acetate-fed aerobic granules with a mean diameter of 1.0 mm were used as biosorbents. Results showed that the kinetics of Zn(II) biosorption on the aerobic granule surface were related to both initial Zn(II) and granule concentrations. It was found that the real driving force for Zn(II) biosorption on the aerobic granule surface could be described by the ratio of initial Zn(II) concentration (Co) to initial granule concentration (Xo), rather than individual Co or Xo. The Co/Xo ratio provides a unified basis for interpretation of the biosorption data obtained under different initial conditions. The maximum biosorption capacity of Zn(II) by aerobic granules was 270 mg g(-1).

CONCLUSIONS

It appears that the aerobic granule can be used as an effective biosorbent for efficient removal of Zn(II) or other types of heavy metals from industrial wastewater.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study could lead to the development of a novel granular biosorbent for the removal of heavy metals from wastewater. A simple and compact aerobic granule-based biosorber could be expected.

Inter-population differences in Cd, Cr, Se, and Zn accumulation by the green mussel Perna viridis acclimated at different salinities

Trace metal (Cd, Cr, Se, and Zn) uptake from the dissolved phase, assimilation efficiency from the dietary phase, and metal body burden, as well as the clearance rate, apparent water permeability and gill surface area were measured in the green mussel Perna viridis collected from two contrasting salinity sites in Hong Kong coastal waters with following acclimation in the laboratory at different salinities. The concentrations of metals were 1.2-6.4x greater in mussels collected from the low salinity site, i.e. Tai O, as compared with Tap Mun (high salinity) mussels. Influx of Cd and Zn from the dissolved phase increased with decreased salinity. Furthermore, Cr(VI) and Se (selenite) influx were also affected by decreased salinity, in particular below 17 psu, suggesting that speciation was not the only factor to effect metal uptake. Long-term acclimation to different salinity also had an effect on metal uptake. Mussels collected from Tap Mun (high salinity) accumulated metals 1.2-2.2x faster than mussels from Tai O (low salinity) at intermediate and high experimental salinities >17 psu. Metal assimilation efficiencies were unaffected by salinity variation, but gut passage times were significantly longer at low (10 psu) salinities, indicating some effect of lowered salinity on mussels gut physiology. Gill surface area, which was similar in both populations of mussels, and filtration rate, which was generally similar or higher in those groups with low metal uptake, could not explain the inter-population difference in metal accumulation. Although there was no significant difference, due to high inter-individual variability, the apparent water permeability of the Tap Mun population was on average about 1.6x greater compared with Tai O mussels, and may partially account for the difference in metal uptake between these two populations acclimated at salinity >17 psu. Thus, the effect of salinity on metal uptake is dependent on metal biogeochemistry as well as a range of physiological responses. There was a clear effect of acclimation to lowered salinity on metal uptake, which may have important implications for metal accumulation modelling, biomonitoring, and toxicity studies.

Biosorption of metal ions with Penicillium chrysogenum

Biosorption of metal ions with Penicillium chrysogenum mycelium is described in this article. Alkaline pretreatment was used to remove proteins and nucleic acids from cells, and this treatment increased the adsorption capacities, for Cr3+ from 18.6 mg g(-1) to 27.2 mg g(-1), for Ni2+ from 13.2 mg g(-1) to 19.2 mg g(-1), for Zn2+ from 6.8 mg g(-1) to 24.5 mg g(-1). The adsorption of metal ions was strongly pH dependent. The mycelium could be used for large-scale removal of Cr3+ from tannery wastewater. The results show that this inexpensive mycelium adsorbent has potential in industry because of its high adsorption capacity. The main chelating sites are amino groups (-NH2) of chitosan in the mycelium. A new model is established, which describes the relation of adsorption of metal ions on pH according to amino group chelating with metal ions and H+. The relative errors of simulation for Cu2+, Ni2+, Zn2+, and Cr3+ are 4.66%, 5.45%,11.55%, and 1.69%, respectively.

Comparison of metal accumulation in mussels at different local and global scales

Cadmium and zinc uptake from the dissolved phase, assimilation efficiency (AE) from the dietary phase, and body burden as well as clearance rate were measured in green mussels, Perna viridis, and blue mussels Mytilus edulis, M. galloprovincialis and Mytilus trossulus. Perna viridis was collected from four sites differentially enriched with trace metals in Hong Kong and blue mussels were collected from different climatic zones, i.e., subarctic and temperate, to allow comparisons with the more tropical green mussels. Despite similar shell length, the dry weight of mussels varied significantly between sites and species and this had a large effect on Cd and Zn accumulation, clearance rate, and metal body burden. All data were, therefore, weight adjusted to allow comparison without this confounding factor. Trace-metal body concentrations were significantly different between sites, and P. viridis collected from Tsing Yi, Hong Kong, had the highest levels of all measured metals when compared with other Hong Kong sites. There was, however, no relationship between the degree of metal enrichment and the Cd and Zn uptake (both from dissolved and particulate sources) and clearance rates. Furthermore, Cd and Zn uptake (dissolved and particulate) and clearance rate varied little between species or climatic zones of collection. Thus, over the range of body trace-metal concentrations measured and between mussel species over large geographical distances and climatic zones, the uptake rates, AEs, and clearance rates are similar when measured under the same laboratory conditions after body-size correction. When other factors such as salinity are also corrected, biomonitoring data from different areas and even utilizing different mussel species may be directly comparable. This study therefore provides important evidence in support of Mussel Watch Programs.

A field study conducted at Kidston Gold Mine, to evaluate the impact of arsenic and zinc from mine tailing to grazing cattle

The grazing trial at Kidston Gold Mine, North Queensland, was aimed specifically to assess the uptake of metals from the tailing and the potential for unacceptable contamination of saleable meat. Further aims included estimating metal dose rates and identifying potential exposure pathways including plant uptake of heavy metals, mine tailings adhered to plants and direct ingestion of mine tailing. It was found that of the 11 metals analysed (As, Zn, Co, Cd, Cr, Sn, Pb, Sb, Hg, Se and Ni) in the animal's liver, muscle and blood during the 8-month trial period, only accumulation of arsenic and zinc occurred. A risk assessment including these two metals was conducted to determine the potential for chronic metal toxicity and long-term contamination, using the estimates of metal dose rate. It was concluded that no toxicity or long-term contamination in cattle was likely at this site. Management procedures were therefore not required at this site; however, the results highlight percent ground cover and standing dry matter (DM) as important factors in decreasing metal exposure from direct ingestion of tailings and dust adhered to plants.

Effects of breed (Angus vs Simmental) and copper and zinc source on mineral status of steers fed high dietary iron

Forty-four Angus (n = 24) and Simmental (n = 20) steers, averaging 301 kg initially, were used to determine the effects of breed and Cu and Zn source (SO4 or proteinate (Prot) form) on Cu and Zn status of steers fed high dietary iron (Fe). Steers were stratified by weight within breed and randomly assigned to treatments. Treatments consisted of: 1) CuSO4 + ZnSO4 ,2) CuSO4 + ZnProt, 3) CuProt + ZnSO4, and 4) CuProt + ZnProt. Copper and Zn sources were added to provide 5 mg Cu and 25 mg supplemental Zn/kg DM. All steers were individually fed a corn silage-based diet supplemented with 1,000 mg Fe (from FeSO4)/kg DM. Liver biopsy samples were obtained at the beginning and end of the 149-d study. Serum samples were collected initially and at 28-d intervals for determination of ceruloplasmin activity and Zn and Cu concentrations. Copper and Zn source did not affect performance, serum or liver Cu and Zn concentrations, or ceruloplasmin activity. Copper status decreased (P < 0.01) in all steers with time, and increasing the level of supplemental Cu from 5 to 10 mg/kg DM on d 84 did not prevent further drops in serum Cu and ceruloplasmin. Simmental steers had lower (P < 0.05) serum and liver Cu concentrations, and serum ceruloplasmin activity throughout the study. These results indicate that neither CuSO4 nor CuProt were effective at the supplemental concentrations evaluated in alleviating the adverse effect of high Fe on Cu status. Simmental steers had lower Cu status than Angus, suggesting a higher Cu requirement.

The effect of humic acid on the uptake of mercury(II), cadmium(II), and zinc(II) by Chinook salmon (Oncorhynchus tshawytscha) eggs

The Chinook salmon (Oncorhynchus tshawytscha) is endangered or threatened in several of its ranges. The uptake of metals by Chinook salmon eggs and how humic acid (HA) affects the uptake is a subject of interest. Humic acid (0, 0.001, 0.01, and 0.05g/l) reduces the uptake of the metal ions Hg(II), Cd(II), and Zn(II), (1.0 microM) by eggs. HA is more effective in reducing the uptake of Hg than that of Cd or Zn. At [HA] = 0.001 g/L Hg uptake is reduced by 44% compared to no HA, while Cd and Zn uptakes are slightly or not reduced. Once the metals are taken up by the eggs, Hg migrates more slowly from the chorion to the yolk than either Zn or Cd. In experiments in which the metal contents of the chorion and yolk were measured at up to 24 h and five days after uptake, the order of migration was Cd > Zn > Hg. This observation is important when discussing the effects of metals on biological processes in the yolk because when Hg is taken up by eggs, a smaller percentage reaches the yolk than does Cd and Zn.