Insolubility of Cr2O3 in Bioaccessibility Tests Points to Requirement for a New Human Oral Reference Dose for Trivalent Chromium

Bioaccessibility measurements have the potential to improve the accuracy of risk assessments and reduce the potential costs of remediation when they reveal that the solubility of chemicals in a matrix (e.g., soil) differs markedly from that in the critical toxicity study (i.e., the key study from which a toxicological or toxicity reference value is derived). We aimed to apply this approach to a brownfield site contaminated with chromium, and found that the speciation was Cr^III, using a combination of alkaline digestion/diphenylcarbazide complexation and X-ray absorption near edge structure analysis. The bioaccessibility of Cr₂O₃, the compound on which a reference dose for Cr^III is based, was substantially lower (<0.1%) than that of the Cr^III in the soils, which was a maximum of 9%, giving relative bioaccessibility values of 13,000% in soil. This shows that the reference dose is based on essentially an insoluble compound, and thus we suggest that other compounds be considered for toxicity testing and derivation of reference dose. Two possibilities are CrCl₃·6H₂O and KCr(SO₄)₂·12H₂O, which have been used for derivation of ecological toxicity reference values and are soluble at a range of dosing levels in our bioaccessibility tests.     

Haematological and biochemical reference intervals for farmed channel catfish

The reference intervals for biochemical variables and red blood cell indices of healthy intensively bred channel catfish Ictalurus punctatus were determined. The blood variables were determined using standardized clinical methods. The reference intervals (25th and 75th percentiles) were established using a non-parametric method. Reference intervals for plasma glucose, serum total protein, sodium, potassium, calcium, magnesium, chloride concentration, primary and secondary red blood cell indices were established. The haematological and biochemical reference intervals established may allow important clinical decisions about channel catfish.     

The nature and role of learning in the orientation and migratory behavior of fishes

Synopsis Fish migration may be viewed as the product of two processes; the selection and tracking of optimal environmental conditions through time and space, and the use of predictive information about environmental structure to bias movements towards a goal. The establishment and maintenance of directional bias is based on the interaction of experience and instinct. The preoccupation of much fish orientation research with innate fixed patterns of behavior on one hand and hydrodynamics on the other has led us to underestimate the possibility that orientation is a flexible process relying on developmental sequences, calibration of the motor-sensory interaction based on experience and the learning of environmental pattern. Evidence illustrating how experience and learning may influence the direction of movement and how the goal is recognized is presented according to two general categories: (a) imprinting and early experience and (b), spatial learning, including the social transmission of migratory routes and directions. In the first category, the olfactory hypothesis of salmon homing is briefly reviewed and new data presented describing olfactory imprinting in Atlantic salmon,Salmo salar. In the second category, evidence is presented demonstrating the modifiability of sun-compass orientation and the ability of some fish species to learn the spatial distribution of landmarks. The role of social transmission in the migration of coral reef fishes is reviewed. The possible role of these learning phenomena in the formation of familiar area maps, route-based and location-based navigation and the critical distance factor is considered. The relationship between life history and the nature of learning in migratory orientation is discussed     

Effects of early adult experience on host selection in insects: Some experimental and theoretical results

A field experiment with Drosophila melanogasterrevealed that when flies encounter a particular food type soon after emergence, the probability of their subsequently being attracted to such a resource is increased. In this experiment, the length of time flies experienced their postemergence environments was under the control of the flies themselves. The experiment thus realistically mimicked one form of experiential effect that may be important in nature. A theoretical model is developed which shows that enhanced adult preferences for the types of resources fed on as larvae can substantially increase the degree of host-based genetic subdivision within a polyphagous population.     

Determination of mercury in human serum and packed blood cells by neutron activation analysis

A method is described for the determination of mercury in human blood serum and packed blood cells employing neutron activation analysis. Great attention was devoted to the collection and manipulation of the samples. The accuracy and precision of the method were tested by analyzing biological reference materials and by comparing the concentrations measured in a number of serum samples to those obtained by another, independent technique (cold vapor atomic absorption spectrometry) in the same samples. The article reports the levels measured in blood serum and packed blood cells samples from 15 adult volunteers, as well as the figures determined in a “second-generation” biological reference material (freeze-dried human serum), prepared and conditioned at the University of Ghent.     

A new microcomputer-controlled neutron activation and analysis system

A microcomputer-controlled irradiation and measurement system and a microprocessor-controlled sample changer have been installed at the SLOWPOKE-2 Facility at the Royal Military College of Canada (RMC). These systems can provide the gamut of instrumental neutron activation analysis (INAA) techniques for the analyst. Custom software has been created for system control, data acquisition, and off-line spectral analysis using programs that incorporate Gaussian peak-fitting methods of analysis. The design and use of the equipment is discussed, and the performance is illustrated with results obtained from the analysis of marine sediment and biological reference materials.     

Plasma and erythrocyte manganese concentrations

This study was carried out to assess manganese (Mn) status after an acute episode of myocardial infarction. Plasma and erythrocyte Mn concentrations were measured from admission to hospital to day 15 postadmission in 21 patients suffering from acute myocardial infarction and in three control groups. The determination of Mn in these biological fluids was performed by electrothermal atomic absorption spectrometry. Plasma Mn was higher (p<0.01) and erythrocyte Mn was similar in the acute myocardial infarction group compared to healthy age-matched control group. Plasma and erythrocyte Mn remained unchanged during the 2 wk after acute myocardial infarction and were not correlated to enzyme activities. A decrease of erythrocyte Mn with age, expressed in nmol/L, was noted (p<0.02). These results suggest that plasma and erythrocyte Mn do not provide an indication of myocardial damage. Nonetheless, Mn status in elderly merits further attention.     

Evaluation of housekeeping genes as references for quantitative real-time PCR analysis of European eel,Anguilla anguilla

Eels are important aquaculture species for which an increasing number of reference genes are being identified and applied. In this study, five housekeeping genes [RPL7 (ribosomal protein L7), 18 S (18 S ribosomal RNA), EF1A (elongation factor 1α), ACTB (β-actin) and GAPDH (glyceraldehyde-3-phosphate dehydrogenase)] were chosen to evaluate their reliability as reference genes for quantitative real-time PCR (qPCR) for the study of Anguilla anguilla. The expression of the selected genes in different eel tissues was determined using qPCR at different growth stages or upon challenge by Anguillid herpesvirus (AngHV), and the expression levels of these genes were then compared and evaluated using the geNorm and NormFinder algorithms. Then, RefFinder was used to comprehensively rank the examined housekeeping genes. Interestingly, the expression of the evaluated housekeeping genes exhibited tissue-dependent and treatment-dependent variations. In different growth periods A. anguilla tissues, the most stable genes were the following: ACTB in mucus; 18 S in skin and kidney; RPL7 in muscle, gill, intestine and brain; EF1A in heart and liver; and GAPDH in spleen. In contrast, in AngHV-challenged A. anguilla tissues, the most stable genes were the following: 18 S in mucus; RPL7 in skin, gill, heart, spleen, kidney and intestine; EF1A in muscle and liver; and ACTB in brain. Further comparison analysis indicated that the expression of RPL7 and EF1A was stable in multiple A. anguilla tissues in different growth periods and in eels challenged by AngHV. Nonetheless, the expression level of GAPDH in eel tissues was lower, and it was unstable in several tissues. These results indicated that the selection of reference genes for qPCR analysis in A. anguilla should be made in accordance with experimental parameters, and both RPL7 and EF1A could be used as reference genes for qPCR study of A. anguilla at different growth stages or upon challenge by AngHV. The reference genes identified in this study could improve the accuracy of qPCR data and facilitate further studies aimed at understanding the biology of eels.