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[en] This paper reports on the bioaccumulation factor as well as the residence time of tritium in marine organisms such as tilapia fish (Tilapia mossambica) and oyster (Crassostrea iredalei) reared under laboratory conditions. The organisms were submerged in aquarium water containing tritium with specific activity of 1.0 nCi/ml. The samples were analyzed for tissue-free water tritium (TFWT) by freeze drying and for tissue-bound tritium (TBT) by combustion methods. Tritiated water collected was assayed using the liquid scintillation counting technique. (author)
[en] Complete text of publication follows. In contrast to thermally processed foods, irradiation is a cold treatment both to reduce microbiological contamination and to increase the shelf-life of raw seafood. According to the list of States' authorizations molluscs can be irradiated in a range of 0.5 / 3 kGy only in authorized countries (e.g. UK, Belgium and Czech Republic). Therefore the aim of this study is to identify, at different dose levels (0.5, 1, 1.5, 2, 3 kGy), irradiated oysters, clams and mussels using luminescence materials from different sites (shells and pulps) and to determine sample sensitivity for previous screening result confirmation. A total number of 10 samples for each species were analyzed by both procedures: screening and calibrated PSL. Samples were irradiated using a low energy X-ray irradiator (RS-2400, Radsource Inc.) with the following operational settings: 150 kV and 45 mA. Whole pulps were simply dispensed into a clean Petri-dish whereas shells powder required to be fixed as a thick layer with silicone grease. Results obtained showed that screening analysis can be used to identify correctly all irradiated and non irradiated samples. Particularly untreated sample exhibited a sensitivity index from 2 to 4 order of magnitude greater than the exposed sample one, while for exposed specimen calibrated PSL signals, after re-irradiation at defined dose, were of the same order of the first measurement (initial PSL counts). In conclusion mineral debris contaminating pulps and biocarbonates from shells can be considered reliable radioinduced markers and PSL techniques can be easily applied for rapid and simple analysis to identify irradiated molluscs in official controls.
[en] The study was conducted to evaluate the molluscicidal activity of E. rheedii methanol bark extract against P. canaliculata and to screen for phytochemical compounds of E. rheedii bark extracts. The golden apple snails with size range of 20 - 40 mm were treated with four different concentrations of E. rheedii (1000, 5000, 10000 and 20000 ppm) and paddy-field water mix with 50 % methanol serving as the control treatment. The molluscicidal effects of the extract were evaluated after 24, 48 and 72 hours. The results of the study showed that high treatment concentrations (10000 and 20000 ppm) recorded the highest mortality rate (100 %) while low concentrations (1000 ppm) showed the lowest mortality rate (27 %). However, no mortality was recorded in the control treatment. The molluscicides activity with LC50 is 1,611 ppm and LC90 is 4,266 ppm and could be attributed to the presence of saponin in the bark extracts. E. rheedii bark extract provides a great potential for developing green pesticides to control P. canaliculata. Nevertheless, further research is needed to determine its biochemical mechanism. (author)
[en] The biokinetics of cadmium were investigated under different environmental conditions in mussel (M. galloprovincialis) using sup(115m)Cd as tracer. The accumulation experiment was followed from water for 34 days and observed concentration factor 68 was obtained. On the other hand, it is observed that between the concentrations used in the experiment, the accumulation increased proportionally with the stable cadmium concentration in water. During depuration, more than one compartment has been observed on the loss curves carried out under different temperature and salinity. The results showed that mussels under 22-10C lost cadmium more rapidly at the beginning compared with the ones under 15-10C, which were kept in the same salinity, 0.21%. At the same time, the loss rates were found significantly different under different salinities. For example, the biological half-lives were 407.6 and 866.2 at the salinities 0.21% and 0.7% S respectively. The loss rate of cadmium was also followed under field condition. It is concluded that the results obtained in the field and the laboratory cannot be comparable; for example, the biological half-lives for the slow components in these two experiments were 350 and 612 days respectively. The relative distribution of cadmium in different organs and tissues are examined, it is observed that cadmium both after accumulation and loss periods, is localized in stomach hepatopancreas, gills and mantle. At the end of the accumulation experiment the highest relative percentage of cadmium was 30% in stomach, 22.7% in hepatopancreas. Likely at the end of loss periods the highest percentages of retained cadmium were 42% in stomach and 32% in hepatopancreas. (author)
[en] The saxitoxin s are bio toxins belonging to the family of toxins of the type PSP. They are paralysing toxins secreted by marine micro-organisms, phytoplankton, called Alexandrium. They constitute a risk for the human health in the event of their consumption in contaminated food. The acceptable maximum limit of these bio toxins in molluscs and shellfish is fixed to 800 μg /kg of meat of molluscs or shellfish. It proves, thus, that it is essential to develop and validate analytical methods for the level monitoring of contamination of the marine resources by these species in order to found a program of their monitoring and to guarantee an acceptable level of the food safety of the products available on the national and international markets. The present work allowed the validation of the quantification method of these toxins which is based on the use of the Receptor Binding Assay (RBA) with liquid scintillation nuclear technique detection using tritium as radiotracer and while proceeding by the different statistical tests of validation (Standard Nf XP T 90-210). The field of linearity ranged from 0 to 20 n M and the limit of detection was found to be 1 n M. The validation of this method will allow the reinforcement of the analytical means of analysis of marine bi toxins type SXT and to set up, in the near future, a monitoring and surveillance routine program for these bio toxins at the national, regional and African scales. (Author)