Biomedical subjects

R Blust

Publications and source records attributed to R Blust.

47 records · Page 3Linked to original sources

PubMed1997

Relationships between river sediment characteristics and trace metal concentrations in tubificid worms and chironomid larvae.

Surficial sediments, midge larvae (Chironomidae, Diptera) and tubificid worms (Tubificidae, Oligochaeta) were collected at 65 sampling sites located in four different river basins in Flanders (Belgium). Concentrations of the trace metals Cu, Zn, Cd and Pb were measured in organisms and sediments by atomic absorption spectrophotometry. Sediments were subjected to a simultaneous extraction scheme to identify trace metal partitioning among various geochemical phases. Three geochemical characteristics of the sediment were analysed; Total Organic Carbon (TOC), Fe oxides and Mn oxides. Non-linear regression models were constructed to determine the relative importance of the different sediment factors contributing to the variation in metal accumulation by the tubificid worms and chironomids. Generally, the amount of variation that could be explained by these models was limited, with coefficients of determination ranging from 0.05 to 0.66. In most cases, metal levels in organisms were positively related to the easily reducible and reducible metal fractions, and negatively related to the TOC and Fe sediment content. The correlations between metal concentrations in tubificid worms and chrinomid larvae were also rather poor, with coefficients of determinations ranging from 0.01 to 0.52. This indicates that understanding the chemistry of the environment does not suffice to predict the concentrations in organisms. Differences in the structural and functional organisation of the organisms, which among others determine the route of exposure, are at least equally important causes of variability in metal availability and accumulation.

Journal Article↗

PubMed1996

Effect of temperature on cadmium and zinc uptake by the midge larvae Chironomus riparius.

The effect of temperature (5 to 25 degrees C) was studied on the uptake of cadmium and zinc by larvae of the midge Chironomus riparius, using artificial chemically defined solutions. The influence of prior acclimation of midge larvae at five temperatures on metal uptake was examined. At all acclimation temperatures metal uptake in organisms increased with increasing exposure temperature. Among the different temperature exposure groups the effect of temperature acclimation on metal uptake is rather variable and a general pattern can not be distinguished. The integration of the different temperature effects explains 69% of the total variation in cadmium uptake and 68% of the total variation in zinc uptake by midge larvae. The factor that accounts for respiration explained 59% of the cadmium uptake and 60% of the zinc uptake by midge larvae. The apparent activation energies for larval metal uptake are much higher than the activation energy for the free diffusion of the cadmium or zinc ion but close to the activation energy for respiration, showing that metal uptake by midge larvae is largely controlled by active physiological rather than by passive diffusional processes.

Animals↗

PubMed1996

Evaluation of effluent toxicity and ambient toxicity in a polluted lowland river.

The impact of an industrial effluent containing high loads of calcium, cadmium, lead chloride and sulphate, on a river ecosystem was assessed using a combination of an effluent toxicity test, an ambient toxicity test and an ecological survey. Only this combination of techniques made it possible to discriminate between the effects of the discharge and those of the background pollution. Each of the individual techniques detected essential effects which the other failed to reveal. With the physical and chemical measurements, important increases of several components were measured at all sampling sites downstream of the discharge. With the ecological survey, however, no large changes in water quality could be determined at the sampling sites, due to the high degree of pollution present upstream of the discharge. Reproduction of Daphnia magna, exposed to sublethal effluent dilutions, was followed over two generations. The offspring of the first generation were shown to have an increased sensitivity to the effluent, compared to the first generation that was born from previously unexposed mothers. Besides the toxicity of the effluent, the acute and chronic toxicity of its main component, CaCl(2), was also determined. The results of the CaCl(2)-tests and toxicity data from literature for the suspected toxicants were transformed to Toxic Units (TU). Using the sum of the TUs we investigated the possibility of predicting effluent toxicity to Daphnia magna. Effluent toxicity was under-estimated by calculating the sum of the TUs of the individual components. Dilution of the effluent to a level at which the measured toxicant concentrations comply with European regulations still showed significant effects on Daphnia reproduction.

Journal Article↗

PubMed1996

Central monoaminergic responses to salinity and temperature rises in common carp

Juvenile common carp, Cyprinus carpio, were exposed to increased levels of salinity (1 % NaCl) at 25 °C and 30 °C. Levels of the monoamine neurotransmitters dopamine (DA) and serotonin (5-HT) and their metabolites dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid were determined in different brain parts. Whereas the elevated temperature only resulted in higher levels of the metabolites, increased salinity caused increased levels of DA and 5-HT as well. Increased levels appeared after the first day of exposure and most effects were further enhanced after 1 week in 1 % NaCl. Increases in DA and 5-HT levels were most pronounced in the hypothalamus, which is the major integrative centre controlling the release of hormones. Thus, one possible role of these changes in neurotransmitter metabolism could be to control the release of prolactin and cortisol, two major hormones involved in the regulation of ion homeostasis in teleosts.

Journal Article↗

PubMed1995

Sequential determination of a combined gamma/beta and pure beta-emitter by gamma and liquid scintillation counting: application to the transport of metals across fish gills.

A combined gamma scintillation/liquid scintillation technique for the sequential determination of two radioactive tracers is described. The method was developed using a combined gamma/beta-emitter (57Co) and a pure beta-emitter (45Ca). First, the 57Co radioactivity was determined by counting the samples in a gamma scintillation analyzer in the energy region 80-165 keV. Next, the samples were counted in a liquid scintillation analyzer. Only one energy region was used to count both isotopes to maximize the counting efficiencies. From the difference between quenched and unquenched beta-spectra, the counting region was set from 0 to 256 keV. The counting efficiency was related to a quench-indicating parameter (tSIE) for both nuclides by fitting a rectangular hyperbola to the quench data. By subtracting the 57Co counts from the observed counts in the total window, 45Ca dpm values were obtained. It is shown that the method presented gives reliable and consistent results. The recoveries of both isotopes are independent of the quench level in a large tSIE range, although five times more radioactivity is required for 45Ca than for 57Co to obtain accurate and reproducible results. The method has been used to study mechanisms of metal transport across biological interfaces.

Animals↗

PubMed1986

Hemoglobin heterogeneity and the oxygen affinity of the hemolysate of some Victoria cichlids.

The hemoglobin patterns of ten cichlid species from Lake Victoria were characterized by polyacrylamide gel electrophoresis. In all tested species the hemoglobin bands display the same electrophoretic mobility. Oxygen equilibria of the purified hemoglobin solution of five species were determined under standardized conditions (pH 7.4 at 20 degrees C). The analysed hemolysates have a relatively high oxygen affinity and for all the tested species the Hill coefficient approached unity. The effect of temperature on the oxygen affinity of Haplochormis "velvet black" hemolysate was determined at 20, 25, 30 and 35 degrees C. The obtained results (delta H value-68 kJ/mol) at pH 8.2 is comparable with earlier published results for other African and South American Cichlidae. The Bohr effect (phi = delta log P50/delta pH = -0.18 between pH 6.6-7.4 at 25 degrees C) proved to be lower than so far reported in other Cichlidae.

Animals↗

PubMed1986

Temperature and pH effects on the total white muscle LDH of Oreochromis niloticus (Pisces: Cichlidae).

The total lactate dehydrogenase enzyme activity of white muscle from O. niloticus shows positive thermal modulation. There is a tendency towards conservation of binding capacity for substrate at physiologically changing pH conditions. Inhibition by excess pyruvate is influenced by temperature and pH, but this phenomenon is not considered to be important in anaerobic glycolysis.

Animals↗

PubMed1985

The oxygen uptake of Sarotherodon niloticus L. and the oxygen binding properties of its blood and hemolysate (Pisces: Cichlidae).

The oxygen consumption of Sarotherodon niloticus L. was found to decline below a critical oxygen concentration of about 2 mg O2/l. An important influence of CO2 on the oxygen affinity of whole blood was observed at all temperatures between 20 and 35 degrees C for gas mixtures containing 5.6% CO2. Purified hemolysate showed extremely high oxygen affinities (p50 = 1.08 mmHg at pH 8.2 and 20 degrees C). Low cooperativity was observed at all temperatures from 20 to 35 degrees C, and pH values between 6.5 and 8.2. The Bohr effect proved to be important at pH values lower than pH 7.5 (phi = delta log P50/delta pH = -0.58 between pH 6.5 and 7.0 at 35 degrees C). The oxygen affinities show high thermal sensitivity without a marked pH influence (delta H value for overall oxygenation at pH was -71.7 kJ/mol). The obtained results are interpreted as adaptations to diurnal variations in ambient temperature and oxygen availability.

Animals↗

PubMed1984

The structure of Artemia sp. haemoglobin. Cleavage of the native molecules into functional units by limited subtilisin digestion.

Limited subtilisin digestion of the high-Mr haemoglobin of the crustacean Artemia sp. results in a series of fragments that are multiples of Mr 16000. Properties such as amino acid composition, iron content, absorption and c.d. spectra of the 16000-Mr functional units strongly resemble those of the intact haemoglobin molecules. The 16000-Mr functional units can bind O2 in a non-co-operative way. They thus represent the structural units from which the globin chains are built up.

Amino Acids↗

PubMedDate not supplied

The energy metabolism of common carp (Cyprinus carpio) when exposed to salt stress: an increase in energy expenditure or effects of starvation?

Stenohaline common carp (Cyprinus carpio) were chronically exposed to the two main osmoregulatory ions, Na+ and Cl-, at levels close to their isoosmotic value for 28 d (171 mM NaCl; 324 mosm kg-1; 10 per thousand). The aim of this study was to assess whether or not the disturbed ion and osmoregulation affected the energy demand and the energy stores of the exposed fish. Salt exposure reduced food intake by 70% and had adverse effects on growth and survival. Although food consumption decreased and growth was seriously affected, routine oxygen consumption of the exposed fish did not drop, indicating a reallocation of energy expenditure from growth toward other processes. A stress-induced increase in plasma glucose was observed. As a result of low food intake, lower levels of protein were used for fuel. Protein use itself was probably replaced by the use of carbohydrates. These effects were confirmed by the depletion of both muscle and liver glycogen stores during the experimental period. We conclude that, besides the effects of reduced feeding, stress induced extra energy requirements leading to the depletion of energy stores.

Adaptation, Physiological↗

PubMedDate not supplied

Effect of salinity on the swimming velocity of the water flea Daphnia magna.

The swimming velocity of the water flea Daphnia magna is dependent on its body size. Therefore, environmental factors that influence growth also influence swimming velocity. This study examined whether exposure to increased salinity reduces swimming velocity only through its effect on body size or whether it also reduces size-specific swimming velocity. Initially, size-specific swimming velocity decreased in a salinity-dependent way. Thereafter, swimming velocities gradually returned to their expected values in all treatments. This acclimation coincided with considerable mortality in the highest-salinity treatment, indicating that daphnids in this treatment either acclimated or died. The initial decrease in size-specific swimming velocity could not be explained by decreased uptake of food. Thus, the results indicate that salinity temporarily impaired physiology. The experiment illustrates how size effects can be accounted for in swimming-velocity analysis and how size-specific swimming-velocity analysis can be used as a non-invasive method to detect stress-induced deviations from normal physiology.

Adaptation, Physiological↗