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Biomedical subjects

C R Janssen

Publications and source records attributed to C R Janssen.

52 records · Page 3Linked to original sources
PubMed2001

Test designs to assess the influence of soil characteristics on the toxicity of copper and lead to the oligochaete Enchytraeus albidus.

Statistical test designs were used to identify and quantify the soil parameters important for determining the ecotoxicological effects of copper and lead to the potworm Enchytraeus albidus. The application of a Fractional Factorial Design revealed that the acute toxicity of copper and lead to E. albidus can vary over more than two orders of magnitude depending on the physico-chemical characteristics of the (artificial) soils. The differences in metal ecotoxicity were mainly determined by pH and organic matter content or cation exchange capacity (CEC). Using a Central Composite Design, models were developed describing the ecotoxicity of copper and lead to E. albidus as a function of these parameters. To validate the developed response surface models, two field soils and the standard artificial soil prescribed by OECD were spiked with copper and lead and the acute toxicity to E. albidus was assessed. These validation experiments confirmed that the toxicity of copper and lead could be predicted using information on the total metal concentration, the pH and the CEC of the soil with toxicity decreasing with increasing pH and CEC.

Animals↗
PubMed2001

Cadmium toxicity for terrestrial invertebrates: taking soil parameters affecting bioavailability into account.

Acute and chronic ecotoxicity tests with cadmium were conducted with the earthworm Eisenia fetida, the potworm Enchytraeus albidus and the springtail Folsomia candida. To assess the influence of the soil type on cadmium bioavailability, these tests were carried out in a standard artificial soil, in a sandy and a loamy field soil. It was not possible to evaluate the influence of soil parameters on the bioavailability on the basis of the experiments that were conducted in only three different soil types, therefore, literature data were also included. However, even in the same standard artificial soils, toxicity data in the literature for Eisenia fetida and Folsomia candida varied considerably. Consequently, no models could be developed that allow a normalization of the ecotoxicity of cadmium to parameters controlling bioavailability. In contrast to zinc, effect concentrations of cadmium for terrestrial invertebrates were always much higher than background concentrations. As the effect of aging on the bioavailability of cadmium was never taken into account, because toxicity experiments were always carried out in freshly spiked soilds, these effect concentrations may even be regarded as conservative. Furthermore, the zinc-cadmium ratio in soils is usually so high that the risk of zinc ecotoxicity for terrestrial invertebrates will usually be much greater in comparison to cadmium ecotoxicity.

Animals↗
PubMed2001

Modeling zinc toxicity for terrestrial invertebrates.

Acute and chronic ecotoxicity tests with zinc were performed with the earthworm Eisenia fetida, the potworm Enchytraeus albidus, and the springtail Folsomia candida. To assess the influence of the soil type on zinc toxicity for these soil invertebrates, these tests were carried out in a standard artificial soil, a sandy and a loamy field soil. Based on the results of this experimental work and data taken from literature, models were developed relating the ecotoxicity of zinc to the most important parameters controlling bioavailability: pH and cation exchange capacity. Models were developed for E. fetida and F. candida using the regression technique partial least squares projection to latent structures (PLS). Acute as well as chronic toxicity data of both organisms could be normalized on the basis of the pH and the cation exchange capacity of the test soils. For other terrestrial invertebrates, not enough data were available to develop reliable models.

Animals↗
PubMed2001

Multigeneration zinc acclimation and tolerance in Daphnia magna: implications for water-quality guidelines and ecological risk assessment.

Development of zinc tolerance is described for the cladoceran Daphnia magna Straus. Zinc tolerance (i.e., toxicity and deficiency) was monitored during successive generations of D. magna acclimated to different zinc concentrations. Survival, reproduction, carapax length measurements, and cellular energy allocation assessments were used as test endpoints. Special attention was paid to the consequences of zinc deficiency. The zinc acclimation concentration clearly influenced the overall fitness of the organism. After several generations of acclimation, an optimal concentration curve was observed, with an optimum zinc concentration between 300 and 450 microg/L. Zinc deficiency resulted in a lower zinc tolerance, a higher coefficient of variation for brood size, and an increased pH sensitivity. These results clearly indicate that (background) zinc concentrations present in test and culture media have to be considered in the evaluation of toxicity test results, especially when the toxicity data are used for water-quality guideline derivation and/or ecological risk assessment. Culture and test media containing very little or no zinc do not provide a basis for useful ecotoxicological data.

Adaptation, Physiological↗
PubMed2001

Zinc and cadmium body burdens in terrestrial oligochaetes: use and significance in environmental risk assessment.

Uptake and elimination kinetics of zinc and cadmium were studied in the oligochaetes Enchytraeus albidus and Eisenia fetida. Even at the highest exposure concentrations where E. fetida survived, the internal zinc concentration was still regulated to a constant level. Enchytraeus albidus could not regulate the internal zinc concentration as well, and the body burden increased after exposure to high zinc concentrations. After transfer to clean soil, the internal zinc concentration dropped back to the control level within a few weeks. For both species, internal cadmium concentrations did not reach equilibrium during the uptake experiments. The internal concentrations causing 50% reduction in cocoon production for E. fetida exposed to cadmium varied between different soil types, indicating that no fixed critical body burdens exist. For both zinc and cadmium, bioaccumulation factors decreased with increasing soil metal concentrations. Bioaccumulation factors may therefore be poor indicators of environmental risk. Their dependence on the total soil concentration makes bioaccumulation factors also unsuitable for assessing the influence of soil characteristics on the bioavailability of metals in contaminated field soils. For the same reason, uptake rate constants are probably not suited for this purpose.

Animals↗
PubMed2001

Toxicity identification of metals: development of toxicity identification fingerprints.

The ecotoxicological and chemical response of five metals (Cd, Cr, Cu, Ni, and Zn) to selective fractionation techniques was assessed using the organism Daphnia magna. The metals Cu and Zn revealed similar toxicity patterns, showing an increased toxicity when lowering the pH, a marked reduction in toxicity after addition of ethylenediaminetetraacetic acid (EDTA). Similar toxicity reductions were obtained by passing the metal solutions over ion exchangers, activated charcoal, and filtration/solid-phase extraction units at neutral and basic pHs. The discrimination between Cu- and Zn-toxicity occurred in the oxidant reduction test, i.e., Zn toxicity was not affected by the addition of Na2S2O3, while Cu toxicity was strongly reduced. A second cluster was formed by Cd and Ni. The toxicity of both metals markedly decreased in the EDTA, ion exchangers, activated charcoal, filtration, and solid-phase extraction tests at high pHs. Discrimination between the toxicity of both metals was accomplished with the graduated pH test, in which a pH-independent toxicity response was found for Ni while the toxicity of Cd increased at lower pHs. Compared with the other metals, a very distinct toxicity pattern for Cr was observed. From the applied fractionation techniques, only the graduated pH and the anion resin tests resulted in a marked change in Cr toxicity. The produced toxicity patterns for each individual metal could therefore be used as fingerprints (i.e., toxicity identification fingerprints) in order to identify the toxicity caused by individual metals for D. magna.

Algorithms↗
PubMed2001

Comparative sensitivity of embryo-larval toxicity assays with African catfish (Clarias gariepinus) and zebra fish (Danio rerio).

Embryo-larval toxicity tests with the African catfish (Clarias gariepinus) were conducted with five chemicals (Cr, Cd, Zn, NaPCP and malathion) and three environmental samples. The sensitivity of the 5-day assay was compared to that of the 12-day embryo-larval toxicity tests with the zebra fish (Danio rerio). The ratios of the C. gariepinus and D. rerio LC50 values ranged from 0.4 for Cr to 8.9 for Zn. The ratios of subchronic values ranged from 0.25 for NaPCP to 3.1 for Cd indicating a more comparable sensitivity of the two species. For the three sediment pore waters, the ratios were 0.6, 1.1, and 2.4 and the subchronic values were identical for the two species. The results suggest that, considering the short-test duration and its sensitivity, the 5-day embryo-larval tests with C. gariepinus may be a potential alternative for short-term embryo-larval toxicity testing with fish.

Animals↗
PubMed2000

Development of methods for evaluating toxicity to freshwater ecosystems.

This article presents a summary of a collaborative research program involving five European research groups, that was partly funded by the European Commission under its Environmental Research Program. The objective of the program was to develop aquatic toxicity tests that could be used to obtain data for inclusion at Level 2 of the Risk Evaluation Scheme for the Notification of Substances as required by the 7th Amendment to EC Directive 79/831/EEC. Currently only a very limited number of test methods have been described that can be used for this purpose and these are based on an even smaller number of test species. Tests based upon algae (Chlamydomonas reinhardi, Scenedesmus subspicatus, and Euglena gracilis), protozoa (Tetrahymena pyriformis), rotifera (Brachionus calyciflorus), crustacea (Gammarus pulex), and diptera (Chironomus riparius) were developed. The tests encompassed a range of end points and were evaluated against four reference chemicals: lindane, 3, 4-dichloroaniline (DCA), atrazine, and copper. The capacity of the tests to identify concentrations that are chronically toxic in the field was addressed by comparing the effects threshold concentrations determined in the laboratory tests with those determined for similar and/or related species and end points in stream and pond mesocosm studies. The lowest no-observed-effect concentrations (NOEC), EC(x), or LC(x) values obtained for lindane, atrazine, and copper were comparable with the lowest values obtained in the mesocosms. The lowest chronic NOEC determined for DCA using the laboratory tests was approximately 200 times higher than the lowest NOEC in the mesocosms.

Aniline Compounds↗
PubMed2000

Derivation of predicted No-effect concentrations for lindane, 3, 4-dichloroaniline, atrazine, and copper.

Environmental risk assessment is a key feature of regulations controlling the placing of new, and the maintenance of existing, chemicals products in the market place. For example, European Commission Directive 93/67/EC on Risk Assessment for New Notified Substances and Commission Regulation (EC) No. 1488/94 on Risk Assessment for Existing Substances requires that risk assessments be carried out for new and existing substances in the European Community. The process of environmental risk assessment seeks to determine the balance of probability of species and communities being damaged by chemical releases. The process relies upon a valid estimation of a predicted environmental concentration (PEC) in relevant environmental compartments and a predicted no effect concentration (PNEC) below which the organisms present in that compartment are unlikely to be significantly affected. If the PEC exceeds the PNEC there is a potential for damaging effects to occur. This article focuses on the determination of PNECs for risk assessment. Methods for determining a PNEC described in OECD Monograph 26 (1989, Report of the OECD Workshop on Ecological Effect Assessment, Paris, France, have been applied to data derived for the four chemicals lindane, 3,4-dichloroaniline, atrazine, and copper in a series of collaborative research projects funded by the European Commission.

Aniline Compounds↗
PubMed2000

Angle matching in intravascular elastography.

Intravascular elastography is a new technique to obtain mechanical properties of the vessel wall and plaque. Mechanical information of vascular tissue is important for characterisation of different plaque components, detection of plaque vulnerability and thus choosing the proper interventional technique. The feasibility of the technique is investigated using phantoms and diseased human arteries. These studies demonstrated that elastography reveals information that is unavailable or inconclusive from the echogram alone. The technique is based on the principle that tissue strain is directly related to its mechanical properties. In intravascular elastography, the tissue is compressed using different intravascular pressures. The strain is determined using cross-correlation techniques of the radio frequency (r.f.) signals. Reliable strain estimates are only obtained when signals of corresponding tissue are correlated. Owing to catheter motion, off-centre position and non-uniform rotation of the intravascular transducer, the r.f. traces at low and at high pressure may be misaligned. Four algorithms are tested to track the corresponding ultrasound signals. Three methods (l1norm, l2norm and cross-correlation) are applied on the r.f. signal and one (l1norm) on the envelope (speckle tracking). Simulations are performed to obtain a data set with a priori knowledge of the scattering particles positions in the tissue at high and low pressure. Different positions of the catheter in the lumen, compression levels of the material and signal-to-noise ratios (SNRs) are investigated. Finally, these findings are corroborated with a phantom experiment in a water tank. From the simulations, it can be concluded that the speckle tracking algorithm has the best performance, under all circumstances. The performance decreases with larger eccentricity of the catheter and larger compression of the material. The SNR is only of minor influence. The speckle tracking algorithm has also the best performance in the phantom experiment. The performance of the speckle tracking algorithm is better than the three r.f.-based algorithms. For intravascular elastography, implementation of this method may improve the quality of the elastogram.

Algorithms↗
PubMed1997

Morphological abnormalities in African catfish (Clarias gariepinus) larvae exposed to malathion.

Newly hatched larvae of Clarias gariepinus were exposed to malathion concentrations ranging from 0.3 mg/l to 5.0 mg/l. Their development was observed through five days posthatch, i.e., the stage in which the vertebral elements are not yet present and the notochord is the only functional body axis. A significant higher proportion of C. gariepinus larvae with deformed notochord and pericardial edema was detected at 2.5 mg/l malathion and higher. The results suggested that (1) deformed notochord was the result of the uncontrolled contractions of the body musculature due to malathion toxicity and (2) the vertebral deformities observed in the fish which have been exposed to malathion from the notochord-stage onwards were the result of a deformed notochord instead of the deformation of the vertebral elements themselves.

Abnormalities, Drug-Induced↗
PubMed1994

Ecotoxicological studies with the freshwater rotifer Brachionus calyciflorus. IV. Rotifer behavior as a sensitive and rapid sublethal test criterion.

The swimming behavior of the freshwater rotifer Brachionus calyciflorus exposed to copper (Cu), pentachlorophenol (PCP), 3,4-dichloroaniline (DCA), and lindane, for periods ranging from 5 min to 5 hr, was examined. A swimming behavior test is described which is based on the rotifers' movement rates as they swim over a grid. For all four toxicants a clear dose-response was observed, with the swimming activity decreasing with increasing toxicant concentrations. For Cu the EC50's, the concentration that reduced the swimming activity to 50% of that of the control value, sharply decreased from 0.22 mg/liter after an exposure of 5 min to 0.068, 0.038, and 0.014 mg/liter after exposures of 30, 60, and 300 min, respectively. PCP affected the rotifers' swimming behavior more gradually, with EC50's decreasing from 7.0 mg/liter after an exposure of 5 min to 5.9, 5.4, and 1.5 mg/liter after 30, 60, and 300 min, respectively. A similar pattern was found for DCA with EC50's ranging from 193 to 45.5 mg/liter for the 5-min and 3-hr exposures, respectively. Exposed to lindane however, B. calyciflorus swimming activity exhibited a different response, and the EC50's gradually increased from 13.7 mg/liter after an exposure of 5 min to significantly higher values of 16.4 and 18.5 mg/liter after periods of 1 and 5 hr, respectively. The results of the swimming activity assays were compared to those of acute and chronic toxicity tests performed with the same test species. The potential use and relevance of this behavioral test criterion were evaluated and discussed.

Aniline Compounds↗
PubMed1993

Ecotoxicological studies with the freshwater rotifer Brachionus calyciflorus. III. The effects of chemicals on the feeding behavior.

The effect of short-term exposure to xenobiotics on the feeding behavior of the freshwater rotifer Brachionus calyciflorus was studied. The filtration and ingestion rates of this rotifer decreased after an exposure of 5 hr to sublethal concentrations of copper, pentachlorophenolate, 3,4-dichloroaniline, and lindane. The effective concentrations at which feeding rate was reduced to 50% of that in controls (EC50) for the respective chemicals are 0.032, 1.85, 41.2, and 8.5 mg/liter. The potential use of feeding behavior as test criterion for toxicity screening tests with aquatic invertebrates is discussed.

Aniline Compounds↗