Disinfection of Sparus aurata eggs with glutaraldehyde

This study was conducted to determine suitable conditions fordisinfecting eggs of gilthead sea bream (Sparus aurata)with glutaraldehyde. Effects of the developmental stage (4–8 cells,morula, blastopore closure or heart beating), of the concentration (C = 200,300or 400 ppm) and of the duration of the glutaraldehyde treatment (T= 2 to 10 min) were investigated. Before the blastopore closurestage, egg manipulation and treatment induced mortality. After this stage, thetoxicity of the glutaraldehyde treatment was negligible if the value of theproduct C × T was less than 1000. Above this value, the percentage ofhatching and of normal larvae decreased and the percentage of imprisoned larvaeincreased. Toxic effects of glutaraldehyde varied according to the egg qualityat the time of the treatment. It was concluded that 200 ppmglutaraldehyde for 4 min, at the blastopore closure stage or attheheart beating stage, were acceptable conditions for disinfecting gilthead seabream eggs at 18 °C.     

Disinfection of Sparus aurata eggs with glutaraldehyde

This study was conducted to determine suitable conditions fordisinfecting eggs of gilthead sea bream (Sparus aurata)with glutaraldehyde. Effects of the developmental stage (4–8 cells,morula, blastopore closure or heart beating), of the concentration (C = 200,300or 400 ppm) and of the duration of the glutaraldehyde treatment (T= 2 to 10 min) were investigated. Before the blastopore closurestage, egg manipulation and treatment induced mortality. After this stage, thetoxicity of the glutaraldehyde treatment was negligible if the value of theproduct C × T was less than 1000. Above this value, the percentage ofhatching and of normal larvae decreased and the percentage of imprisoned larvaeincreased. Toxic effects of glutaraldehyde varied according to the egg qualityat the time of the treatment. It was concluded that 200 ppmglutaraldehyde for 4 min, at the blastopore closure stage or attheheart beating stage, were acceptable conditions for disinfecting gilthead seabream eggs at 18 °C.     

Off-axis crustal thickness across and along the east pacific rise within the MELT area

Wide-angle seismic data along the Mantle Electromagnetic and Tomography (MELT) arrays show that the thickness of 0.5- to 1. 5-million-year-old crust of the Nazca Plate is not resolvably different from that of the Pacific Plate, despite an asymmetry in depth and gravity across this portion of the East Pacific Rise. Crustal thickness on similarly aged crust on the Nazca plate near a magmatically robust part of the East Pacific Rise at 17 degrees15'S is slightly thinner (5.1 to 5.7 kilometers) than at the 15 degrees55'S overlapping spreading center (5.8 to 6.3 kilometers). This small north-south off-axis crustal thickness difference may reflect along-axis temporal variations in magma supply, whereas the across-axis asymmetry in depth and gravity must be caused by density variations in the underlying mantle.     

Rat immunoglobulins

Five immunoglobulin isotypes (or classes) have been identified in the human as well as in the rat species. The homologies between the human and the rat immunoglobulin classes have been well defined with the help of the monoclonal immunoglobulins produced by the LOU immunocytomas (plasmocytomas,myeloma tumours). The LOU rat immunocytomas model, the physicochemical and the biological properties of the rat immunoglobulins are described in this review.     

Distribution of bacteria in a continuous-flow nitrification column

Nutrient solution containing (NH₄)₂SO₄ was supplied at a constant rate to Nitrosomonas europaea and Nitrobacter agilis growing in a column packed with glass beads. Conversion of NH₄⁺ to NO₂^? and NO₃^? was incomplete indicating that growth of the bacteria was not nutrient limited. After 7 months the column was dismantled and the arrangement of the bacteria on the beads examined using a scanning electron microscope. Nitrifying bacteria were found only in the upper regions of the column. They occurred most commonly in monolayers, less commonly in layers of about 20 cells and rarely in piles of about 100 cells in depth. Further down the column the glass beads were covered in a layer of slime and no bacteria were seen. This suggests that growth of the nitrifiers was neither controlled by diffusion of metabolites through a microbial film nor limited by competition between the bacteria for space on the surface of the glass beads.     

Dynamics of nitrification in a continuous flow system

Ammonium sulphate was added at constant rates to a column containing a mixture of glass beads and marble chips inoculated with the nitrifying bacteria, Nitrosomonas europaea and Nitrobacter agilis. Changing the rate of NH₄⁺ addition caused nitrite and nitrate concentrations in the outflow to stabilize at characteristic steady state values after brief transition periods. The steady state concentrations were inversely related to the flow rate. The transition phases were characterized by overshoots in the concentrations of nitrite and nitrate when the flow was reduced and a smooth monotonic change to the new steady state values when it was increased. Three mathematical models were developed based on several simplifying assumptions and tested with the data. The best fit was obtained when it was assumed that growth of the organisms could be described by a modification of the Verhulst-Pearl logistic equation.     

A brief history of the prevention of infectious diseases by immunisations

Infectious diseases have always been a terrible scourge for humans. The appearance of these plagues, as they were called without distinction, was generally connected to various conditions: asters, climatic changes or religious reasons. The concept of contagious, and then infectious, diseases came slowly. Variolation, i.e. transmission of ‘virulent’ matter to induce a natural disease and the immunity against it, was brought from Constantinople to England by Lady Montague, in 1721. This ‘variolation’ technique was also often performed in veterinary medicine against diseases like sheep-pox or pleuropneumonia. As ‘vaccination’ is the term generally accepted for ‘immunisation’, variolation can be the word designating such a technique. The second period of the history of immunisation began, in 1880, with the studies of Pasteur and his collaborators. A great number of bacterial vaccines were developed: dead, live but attenuated or only parts of pathogens. The viruses were produced in animals, then in eggs and at last, in tissue cultures. Second generation vaccines appeared with genetic engineering: recombinant vaccines, vector vaccines, nucleic acids vaccines, and markers vaccines, among others. These novel technologies can permit the development of new ones and improve the quality of the vaccines already existing.     

A methodological approach for ecotoxicological characterization of non-hazardous sediments for their beneficial reuse

Purpose

In France, the beneficial reuse of sediments is conditioned upon a demonstration of environmental acceptability for each scenario. Such evidence has to be provided in application of the NF EN 12920 +A1 standard methodologies. Before the application of risk assessment methodology, the HP14 hazard property must be measured using specific bioassays. However, sediments may have ecotoxicological impacts despite a non-hazardous classification. The application of a battery of bioassays sensitive to non-hazardous sediments could allow to select sediments before choosing the beneficial reuse option.

Materials and methods

First, HP14 methodologies were applied on the studied sediments. These sediments had to be managed on shore according to French legislation. Then, following recommendations from a previous study, other ecotoxicological tests and modified ecotoxicological tests from HP14 methodology were selected. Ostracods mortality and growth tests were selected as a complement because its sensitivity to sediment ecotoxicity is known. To take into account the effects of extraction method and liquid/solid ratio on ecotoxicological impact of sediments, ecotoxicological tests have been applied to percolates. They have been obtained from up-flow percolation tests following the standard NF EN 14405. For each percolate, the rotifer clones reproduction test and the ostracod mortality and growth tests were performed.

Results and discussion

Contaminant analyses of sediments studied reveal differences in contamination between non-hazardous sediments. The majority of ecotoxicological tests carried out in the HP14 test batteries do not differentiate between non-hazardous sediments with low ecotoxicity. However, inhibition of rotifer reproduction and inhibition of plant germination and growth tests can be used. Among the complementary bioassays performed, the ostracods growth inhibition and multigenerational Daphnia reproduction inhibition tests are especially sensitive. Bioassays performed on percolates reveal low ecotoxicities that were not detected with conventional bioassays. For these tests, maximum ecotoxicities are observed on the first percolates for most of the tested sediments, and ecotoxicity effects decrease with the increase in the liquid/solid ratio.

Conclusions

The results enable us to propose a bioassay battery able to highlight the intrinsic toxicity of non-hazardous sediments. This is achieved through bioassays and using up-flow percolation columns to detect low ecotoxicity. This battery can be integrated into the SEDIMATERIAUX approach to ensure the choice of the beneficial reuse option for such sediment. As some of the proposed bioassays remain unsuitable for marine sediments, future studies will adapt the methodology to the presence of marine salts.

     

Population size does not influence mitochondrial genetic diversity in animals

Within-species genetic diversity is thought to reflect population size, history, ecology, and ability to adapt. Using a comprehensive collection of polymorphism data sets covering approximately 3000 animal species, we show that the widely used mitochondrial DNA (mtDNA) marker does not reflect species abundance or ecology: mtDNA diversity is not higher in invertebrates than in vertebrates, in marine than in terrestrial species, or in small than in large organisms. Nuclear loci, in contrast, fit these intuitive expectations. The unexpected mitochondrial diversity distribution is explained by recurrent adaptive evolution, challenging the neutral theory of molecular evolution and questioning the relevance of mtDNA in biodiversity and conservation studies.