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R Blust

Publications and source records attributed to R Blust.

At least 37 records · Page 2Linked to original sources
PubMed2001

A mechanistic model for the uptake of waterborne strontium in the common carp (Cyprinus carpio L.).

The release of radioactive strontium to the environment is of concern due to the strong accumulation of this calcium resembling element in the bone and other tissues. To predict the effects of changes in environmental conditions on the uptake of Sr2+ and Ca2+ by freshwater fish, a Michaelis-Menten type model is introduced that accounts for the effects of chemical speciation, hydrogen ion activity, and metal ion competition. The uptake kinetics were characterized in vivo from short-term exposure experiments using the common carp (Cyprinus carpio) as the model organism. Fish were exposed to a wide range of waterborne Sr2+ (0.2-10,000 microM) and Ca2+ (10-10,000 microM) concentrations and water pH (5.0-8.5). Strontium uptake by the whole body of fish increased with increasing Sr2+ activity, displaying saturation kinetics, but decreased significantly with increasing Ca2+ and H+ activities in the water. Likewise, calcium uptake by the fish decreased with increasing Sr2+ and H+ activities in the water. The model fitted to the pooled data explains 97.5% of the variation in Sr2+ uptake and 86% in Ca2+ uptake over the wide range of exposure conditions and reveals that Sr2+ and Ca2+ inhibit each other completely competitively, while H+ inhibits the uptake of both metal ions in a partially noncompetitive way. This model can be used as a mechanistic tool to predict the uptake of these metals in carp under variable conditions.

Animals↗
PubMed2001

Accumulation of metals in the tissues of three spined stickelback (Gasterosteus aculeatus) from natural fresh waters.

Three spined sticklebacks (Gasterosteus aculeatus) were sampled from five different watercourses in Flanders (Belgium). Concentrations of cadmium, lead, copper, and zinc were measured in water, sediment, food, and fish tissues. Considered as food was the taxonomic groups of macroinvertebrates predominately present in the stomach of the sticklebacks at the different sites. Analyzed tissues were gill, liver, and muscle. To determine the relative importance of the different uptake routes, multiple linear regression models were constructed. Accumulated metal levels in the tissues were related to metal levels in sediment, water, and food. Generally, the amount of variation in accumulated metal levels that could be explained by these models was limited, with coefficients of determination not exceeding 0.57. Cadmium levels in the three tissues were solely related to levels in invertebrates. The same was true for copper in liver. In the other cases the tissue levels could be related only to sediment and/or water levels. Depending on the metal, levels were highest in gill or in liver. In all cases lowest metal levels were measured in muscle.

Animals↗
PubMed2001

Stress responses and changes in protein metabolism in carp Cyprinus carpio during cadmium exposure.

Stress responses and changes in protein metabolism were studied in common carp Cyprinus carpio exposed to 0, 0.8, 4, and 20 microM cadmium (Cd) over a 29-day period. Blood and other tissue samples were taken after 4 and 29 days of exposure. The highest Cd concentration proved to be lethal to the fish, resulting in 100% mortality after 21 days of exposure. Cd accumulated in the tissues in the following order: kidney>liver>gills. Blood hematocrit, blood hemoglobin, plasma glucose, plasma lactate, and tissue total protein contents were not significantly altered. The concentrations of Cd and zinc (Zn) binding metallothioneins ((Cd, Zn)-MTs) were in the following order=liver>kidney>gills. An increase in (Cd, Zn)-MTs was observed at all exposure concentrations at days 4 and 29 in kidney and at Day 29 in gills. No significant changes in (Cd, Zn)-MT contents were found in liver. The concentrations of free amino acids and the activities of proteases were increased at Day 4 in gills, liver, and kidney of carp exposed to 4 and 20 microM Cd, and in gills and kidney at Day 29 in carp exposed to 4 microM Cd. The observed increases in the activities of aspartate aminotransferase and alanine aminotransferase suggest that the observed proteolysis is intended to increase the role of proteins in the energy production during Cd stress. However, this increased activity of both aminotransferases was not found in gills during exposure to the lethal Cd concentration, indicating that Cd may also cause an inhibitory effect on the activity of these enzymes above a certain level.

Alanine Transaminase↗
PubMed2001

Esterase variation in the periwinkle Littorina littorea, along the western and eastern Scheldt estuarium.

Variation in esterase expression (EST) has been investigated in 360 specimens of the periwinkle Littorina littorea collected at nine sites along the polluted western Scheldt and the relatively clean eastern Scheldt estuary. Mean number of EST bands differed among the sites, while a Dice similarity based multi-dimensional scaling along with a minimum spanning tree procedure, revealed an estuary based structuring, clustering the most polluted and least saline like sites together. The underlying factors and mechanisms (i.e. selection, regulation) which are responsible for this structuring remain to be determined.

Animals↗
PubMed2001

Intersex and sterility in the periwinkle Littorina littorea (Mollusca: Gastropoda) along the Western Scheldt estuary, The Netherlands.

In this study we present the results of an intersex survey of Littorina littorea along the heavily polluted Western Scheldt estuary (the Netherlands), and record for the first time the intersex phenomenon in L. littorea from Dutch waters. Intersex differed significantly between localities and was the highest in the vicinity of the harbours of Antwerp and Vlissingen, as reflected by the I

Animals↗
PubMed2001

Heavy metal levels in the sediments of four Dar es Salaam mangroves. Accumulation in, and effect on the morphology of the periwinkle, Littoraria scabra (Mollusca: Gastropoda).

Heavy metals were determined in the soft tissue and shells of the littorinid, Littoraria scabra, and in the sediments of four mangrove areas along the Dar es Salaam coastline where L. scabra was collected. Several metals accumulate, preferentially in the animals' soft body parts, but do not seem to affect the shell morphology of this species. Sediment-metal levels, measured in the direct vicinity of Dar es Salaam have increased dramatically over the last decade. Nonetheless, these levels are still lower compared to metal-sediment levels reported in polluted European and American estuaries. Soft-tissue metal levels detected in L. scabra are, nevertheless, with the exception of Cr and Zn, comparable to metal levels reported in other gastropod species.

Animals↗
PubMed2001

Bioavailability of Cd to the common carp, Cyprinus carpio, in the presence of humic acid.

The uptake of cadmium by the common carp, Cyprinus carpio, was studied in chemically defined freshwater in the absence and presence of commercial humic acid. This was done to evaluate whether the cadmium uptake by carp in the presence of humic acid was related to the ambient Cd2+ -ion activity or whether the complexed metal also contributed to the uptake. Uptake of Cd during a 3-h period of exposure was used as a measure of the biological availability of the metal. The uptake rate data for Cd in total fish and gills obtained in the absence (control) and presence (treatment) of humic acid were analyzed using a Michaelis-Menten model for mediated transport. The Michaelis-Menten parameters KM and Vmax obtained in the control and the treatment experiment were compared for each of the two investigated carp compartments (total fish and gills). The model parameter estimates for Cd uptake by total carp in the treatment experiment (KM = 0.41 +/- 0.11 micromol l(-1); Vmax = 0.66 +/- 0.13 micromol kg(-1) h(-1)) were not significantly different from the model parameters in the control experiment (KM = 0.34+/-0.06 micromol l(-1); Vmax = 0.58+/-0.07 micromol kg(-1) h(-1)) on the basis of Welch's approximate t-test. Similarly, the Michaelis-Menten model parameter estimates for Cd uptake by carp gills in the treatment experiment (KM = 0.15 +/- 0.06 micromol l(-1); Vmax = 5.14 +/- 1.07 micromol kg(-1) h(-1)) were not significantly different from the model parameters derived from the control experiment (KM =0.27 +/- 0.09 micromol l(-1); Vmax = 7.63+/-1.38 micromol kg(-1) h(-1)). This indicated that the Cd uptake rate by total carp and in carp gills in the presence of commercial humic acid followed the measured variations in Cd2+ -ion activity as predicted by the control experiment.

Animals↗
PubMed2001

Dynamics of (Cd,Zn)-metallothioneins in gills, liver and kidney of common carp Cyprinus carpio during cadmium exposure.

Cadmium concentrations, (Cd,Zn)-metallothionein (MT) concentrations, MT synthesis and the relative amounts of cadmium bound to (Cd,Zn)-MTs were determined in gills, liver and kidney of common carp Cyprinus carpio exposed to 0, 0.5 microM (0.06 mg.l(-1)), 2.5 microM (0.28 mg.l(-1)) and 7 microM (0.79 mg.l(-1)) Cd for up to 29 days. Cadmium accumulation was in the order kidney > liver > gills. Control levels of hepatic (Cd,Zn)-MT were four times higher compared to those of gills and kidney. No increases in (Cd,Zn)-MT concentrations were observed in liver during the exposure period. In comparison with control carp, (Cd,Zn)-MT concentrations increased up to 4.5 times in kidney and two times in gills. In both these organs, (Cd,Zn)-MT concentrations were linearly related with cadmium tissue levels and with the de novo synthesis of MTs. Hepatic cadmium was almost completely bound to (Cd,Zn)-MT, while percentages of non-MT-bound cadmium were at least 40% in gills and 25% in kidney. This corresponded with a total saturation of (Cd,Zn)-MT by cadmium in kidney and a saturation of approximately 50 and 60% in gills and liver, respectively. The final order of non-MT-bound cadmium was kidney > gills > liver. Our results indicate that cadmium exposure causes toxic effects, which cannot be correlated with the accumulated levels of the metal in tissues. Although cadmium clearly leads to the de novo synthesis of MT and higher (Cd,Zn)-MT concentrations, the role of this protein in the detoxification process is clearly organ-specific and its synthesis does not keep track with cadmium accumulation.

Animals↗
PubMed2001

Effect of temperature on the uptake of waterborne strontium in the common carp, Cyprinus carpio (L.).

The effect of temperature on the uptake kinetics of strontium (Sr) in the common carp (Cyprinus carpio) was studied in vivo, exposing pre-acclimated fish to a wide range of Sr concentrations in water (Sr(total)=0.2-10,000 microM; Ca(total)=348 microM) at 10, 20, 25 and 30 degrees C. Sr uptake rates were determined in the whole body, gills and blood of the fish after an exposure period of 3 h and were analyzed as a function of the free-ion activity of Sr and Ca in water. The uptake of Sr(2+) by the whole body, gills and blood increased with temperature and showed saturation kinetics with the increase of Sr(2+) activity. Analyzing the observed uptake rates with a Michaelis-Menten type model showed that the kinetic parameters (J(max), K(m) and K(i)) for both Sr(2+) and its analogue Ca(2+) are temperature dependent. Thermodynamic analysis of the temperature effects indicates that the Arrhenius activation energies (E(a)) required for Sr(2+) uptake (91.9 kJ mol(-1)) and Ca(2+) uptake (105.9 kJ mol(-1)) in the whole body of carp were constant over the temperature range 10-25 degrees C and showed a break in the Arrhenius plots above this temperature. The Arrhenius plot for the Sr(2+) uptake in blood was similar to that for the whole body uptake with an E(a) of 98.1 kJ mol(-1). However, the E(a) for Sr(2+) uptake in gills was much smaller and constant (58.1 kJ mol(-1)) over the temperature range of 10-30 degrees C. For a temperature change from 10 to 25 degrees C, the Q(10) for Sr(2+) uptake in whole fish, gills and blood were 3.71, 2.29 and 4.05, respectively. Compared with Ca(2+) uptake, Sr(2+) uptake appears to require a lower activation energy for transport across the solution body interface in carp. The similar pattern of Arrhenius plots and magnitude of activation energies for Sr(2+) uptake both in blood and whole fish suggest that the uptake into the blood across the basolateral membrane is the rate-limiting energy barrier and hence dictates the overall uptake rate of Sr(2+) in whole fish.

Animals↗
PubMed2001

Cadmium-binding to transferrin in the plasma of the common carp Cyprinus carpio.

In this study, it was investigated by autoradiography with radioactive cadmium after Western blotting of two-dimensional electrophoresis gels, to which proteins cadmium is mainly bound in plasma of common carp Cyprinus carpio. The obtained results demonstrate that in carp plasma, cadmium is primarily bound to two high molecular weight proteins. Relative small amounts are bound to a protein with M(r) approximately 60000. The other metal-binding protein, with M(r) approximately 70000 and pI approximately 6.7 was identified as transferrin. The conditional equilibrium constants for the binding of cadmium ions to the two metal-binding sites of this protein were calculated as logK(1)=5.40+/-0.12 and logK(2)=4.66+/-0.21, which are comparable to those of human transferrin under the same experimental conditions. Transport of cadmium in plasma of carp was found to be different from that of brown trout Salmo trutta and man, where cadmium is mainly bound to albumin and transferrin. The prominent binding of cadmium to transferrin can be explained by the absence or at least the very low concentrations in which albumin is present in carp plasma.

Animals↗
PubMed2001

Morphological and metabolic changes in common carp, Cyprinus carpio, during short-term copper exposure: interactions between Cu2+ and plasma cortisol elevation.

The effects of increased endogenous cortisol levels were compared with those of sublethal copper exposure in the freshwater common carp, Cyprinus carpio. Fish were exposed to either increased levels of endogenous cortisol (200 ng/ml) or sublethal copper (1.9 microM) alone or were pretreated by elevating plasma cortisol levels prior to copper exposure to assess whether interactions between both treatments occurred. Effects induced by increased cortisol levels included increased Na+/K(+)-adenosine triphosphate (ATPase) activity and increased plasma Na+ and plasma osmolarity, while copper exposure induced anaerobic metabolism, gill damage, decreasing Na+/K(+)-ATPase activity, decreasing plasma ion levels, and blood thickening. Pretreatment of copper-exposed fish with cortisol partially protected these fish by reducing the copper-induced decrease in Na+/K(+)-ATPase activity. Overall, the results obtained in this study argue against a major role for cortisol as an intermediate for the toxic effects of copper.

Animals↗
PubMed2000

Heavy metal accumulation in the periwinkle Littorina littorea, along a pollution gradient in the Scheldt estuary.

Inductively coupled plasma atomic emission spectrophotometry (ICP-AES) was used to determine heavy metal concentrations in the shells and soft tissues of the periwinkle Littorina littorea, collected at seven sites along the Scheldt estuary. Several metals accumulate in the animals soft body parts, and are related to the seawards decreasing pollution gradient. No clear correlation with a previously detected shell size patterning could be established.

Animals↗
PubMed2000

Effects of pH on cadmium and zinc uptake by the midge larvae Chironomus riparius.

We studied the effect of pH on the uptake of cadmium and zinc by fourth instar larvae of the midge Chironomus riparius within the pH range 5.5-10.0, using chemically defined solutions. The effect of prior acclimation on metal uptake was examined for four pH levels, i.e. pH 5.5, 7.0, 8.0 and 9.5. At least three factors were important in determining the effect of pH on the cadmium and zinc uptake by midge larvae. The effect of pH on metal uptake is the combined result of changes in free metal ion activity, changes in pH of exposure and changes in pH of acclimation, the latter representing a physiological effect. Within each acclimation group metal uptake in larvae increased with increasing pH of exposure in the range 5.5-9.0 but decreased between pH 9.0 and 10.0. Taking into account the decreased free metal ion activity, metal uptake was still high at pH 10.0. A possible explanation for this is that an increase in pH alters the metal uptake process by decreasing the protonation of the binding sites. That is, the biological availability of the free metal ion increases with increasing pH. Among the different pH exposure groups, acclimation had a positive effect up to pH 9.0 but a negative effect between 9.0 and 10.0. Two different uptake models were applied to describe the observed variation in metal uptake. With a non-linear, semi-empirical model, the integration of the different pH effects for the pooled data described no more than 38% of the total variation in cadmium uptake and 36% of the total variation in zinc uptake by midge larvae. When the model was fitted to the uptake data of larvae acclimated to the exposure conditions, 78 and 69% respectively of the variation was described. The second model, a biological ligand model, was not able to discriminate between effects of pH in acclimated and non-acclimated exposure groups. Only for the data of larvae acclimated to the exposure conditions the model could describe a significant amount of the observed variation in metal uptake, R(2) values being comparable to those of the first model. The remaining high undescribed variation could be ascribed to the high natural variation in metal uptake by midge larvae.

Journal Article↗
PubMed2000

Can excrement and feathers of nestling songbirds be used as biomonitors for heavy metal pollution?

Although birds have been frequently used as indicators of heavy metal pollution, few studies have examined pollutant levels in nestling passerines. In this paper we determined the levels of two essential (zinc and copper) and three nonessential heavy metals (lead, cadmium, and arsenic) in the excrement and feathers of great (Parus major) and blue tit (Parus caeruleus) nestlings at a polluted site (near a metallurgic factory) and a reference site (4 km farther east). The excrement of both great and blue tit nestlings contained significantly higher concentrations of arsenic, cadmium, copper, and lead at the polluted site. Zinc concentrations did not differ significantly between sites for both species. The feathers of great and blue tit nestlings accumulated significantly higher concentrations of lead at the polluted site than at the reference site. Zinc levels in the feathers of great tit nestlings were significantly higher at the reference site than at the polluted site. For all other elements considered, concentrations did not differ significantly between the two sites. There were no interspecific differences in metal levels between great and blue tits in both excrement and feathers. There was a significant positive correlation between the lead concentration in the excrement and feathers for both great and blue tits. We therefore conclude that excrement of great and blue tit nestlings can be used as a biomonitor for heavy metals (lead, cadmium, arsenic, and copper), whereas feathers appear only to be suitable as a biomonitor for lead pollution.

Animals↗
PubMed1999

Great and blue tits as indicators of heavy metal contamination in terrestrial ecosystems.

Although there are abundant data on heavy metal contamination in the feathers of seabird species and birds of prey, relatively few studies have addressed the use of passerine birds as indicators of point-source contamination. Concentrations of three essential elements (Al, Zn, and Cu) and two toxic metals (Cd and Pb) were determined in the outer tail feathers of great and blue tits (Parus major and Parus caeruleus), two small insectivorous passerines, at a presumed polluted site (in an urban area close to household waste incinerators) and at a reference site (in a nature reserve). For the great tit, both Cd and Cu levels were significantly higher at the polluted site than in the nature reserve. For the blue tit, Cd, Pb, and Cu levels were significantly higher at the polluted site than at the reference site. There were striking differences in metal levels between blue and great tits inhabiting the same polluted site: lead, zinc, and copper were significantly higher in the smaller blue tit than in the great tit. We suggest that tit (Parus) species, which have been important models in behavioral and ecological research, may be very useful as biomonitors for local contamination.

Animals↗
PubMed1997

Water household of the common carp, Cyprinus carpio, when submitted to an osmotic challenge, as determined by diffusion-weighted magnetic resonance imaging at 7 T.

In vivo diffusion-weighted magnetic resonance imaging (MRI) was used to determine the effects of an osmotic challenge (1% NaCl) to a freshwater fish, the common carp (Cyprinus carpio). The imaged region covered organs such as the swimbladder, the liver, the kidney, the intestine, the spinal cord, and muscle tissue. A striking difference between salt-treated and control fish was found in the liver. The apparent diffusion coefficient value of livers from control fish was (0.39 +/- 0.16) 10(-9) m2/s and of salt-treated fish was (1.23 +/- 0.14) 10(-9) m2/s, which points to an increase in extracellular water content. These results were partially confirmed by a decrease in dry/wet weight ratio of the liver tissue. We also found increased levels of stress proteins in liver tissue. The Q factor of the applied radiofrequency coil dropped dramatically when we performed experiments with salt-exposed fish, indicating an increased conductivity resulting from the increased ion concentration and osmolarity of the fish. The data on plasma osmolarity of salt-exposed fish confirm a significant osmolarity increase upon salt exposure (from 334 to 430 mOsm/kg) and exceeded the osmolarity of the salt water (324 mOsm/kg), indicating that carp tend to cope with an increased salinity by increasing the internal osmolarity (hyperosmotic regulation). These data demonstrate that diffusion-weighted MRI might be a useful and noninvasive tool in the study of osmotic challenges of aquatic organisms.

Animals↗
PubMed1997

Effects of sublethal copper exposure on copper accumulation, food consumption, growth, energy stores, and nucleic acid content in common carp.

Juvenile common carp were exposed for 28 days to three different sublethal copper concentrations (0.20 microM, 0.55 microM, and 0.80 microM). Food consumption was monitored on a daily basis during the exposure period, while growth, copper accumulation, energy stores, and nucleic acid contents were assessed weekly. Copper exposure to 0. 80 microM affected both growth and feeding behavior in common carp. At 0.55 microM, growth was affected despite normal food consumption. Even at the lowest copper concentration (0.20 microM), metabolic demand for the fish increased, challenging the carp with an increased demand for food. Copper accumulation mainly occurred in the liver, reaching an equilibrium between uptake and excretion after 1 month of exposure. Substantial biochemical changes were observed at the two highest copper exposure concentrations, but the correlation between growth rate and RNA:DNA ratio was poor considering the substantial differences in growth rate. The use of the RNA:DNA ratio as a sensitive biomarker is questioned.

Animals↗