Zinc, copper, cadmium, and lead concentrations in water, sediment, and Anadara senilis in a tropical estuary.

Spatial and seasonal contaminations of zinc, copper, cadmium, and lead were assessed simultaneously in water, sediment, and in the bivalve Arca senilis from the Milliardaires Bay (Cote d'Ivoire) between February and October 2008. The metal load in sediments doubled from the dry season to the rainy season. On the contrary, metal concentrations in waters decreased significantly from the dry season to the rainy season. Zn and Pb concentrations in A. senilis showed similar seasonal variation with sediments. On the other hand, A. senilis regulated Cu concentrations by eliminating about twelve times the concentration accumulated during the dry season. Apparent Zn, Cu, Cd, and Pb concentration gradients were observed, but no significant differences between stations for sediment, water, and A. senilis. Concentrations in sediment increased from stations close to Abidjan Harbor towards farther stations, while concentrations in A. senilis showed a reverse gradient. The distribution gradient of A. senilis indicates pollution from local sources, but a transplant experiment is needed to better understand the observed spatial trend. Zn and Cu concentrations may pose little risk to human health and the environment, but they are the highest on the regional scale. On the contrary, Cd and Pb concentrations in A. senilis exceeded the maximum allowable limits set by the European Commission. Complementary studies including chemical speciation should be considered to provide a more accurate assessment of the risk of heavy metals to the environment.

Estimating poultry aspergillosis prevalence and diagnostic accuracy of histopathological and mycological culture in Côte d'Ivoire using Bayesian latent class analysis.

This study aimed to estimate the prevalence of poultry aspergillosis and evaluate the accuracy of histopathology (test under evaluation) and mycological culture (an imperfect reference test). Farms raising layer and breeder or broiler birds, with suspected aspergillosis cases, clinical or subclinical, were eligible and visited for sampling. After necropsy, histopathology and mycological culture examinations were conducted by two evaluators. A Bayesian latent class model was used to estimate the accuracy of histopathology when compared to the imperfect reference test, mycological culture. A total of 142 chicken farms, 96 laying and breeding hen farms, and 46 broiler farms were used for the study. True aspergillosis median prevalence was estimated at 63.7% (95% credibility intervals, CrI: 53.8%, 73.0%) in layers and breeders and at 65.2% (95% CrI: 50.2%, 78.3%) in the broiler farms' population. The median diagnostic sensitivity of histopathology and culture were estimated at, respectively, 98.8% (95% CrI: 94.6%, 100.0%) and 90.4% (95% CrI: 83.6%, 95.3%). Tests' diagnostic specificity was estimated at, respectively, 97.3% (95% CrI: 87.7%, 99.9%) and 95.7% (95% CrI: 91.8%, 98.2%). Both tests had very high and comparable positive predictive values, but, in a population where disease prevalence was 25%, histopathology had a higher negative predictive value than culture.

Characterization of aspartate transcarbamylase activity from gonads of the soft shell clam, Mya arenaria.

Aspartate transcarbamylase (ATCase, EC 2.1.3.2) has been shown to be a good index of the reproductive cycle in marine molluscs. However, this enzyme has never been studied in the soft shell clam Mya arenaria. The characteristics of gonadal ATCase of the soft shell clam, Mya arenaria were therefore determined since we need powerful tools to assess the degree of effects of endocrine disruptors in this species at risk. Enzyme kinetic values observed at pH 8.3 were significantly lower than those measured at pH 9.4. The optimal conditions for the enzyme assays were reached in the presence of a 10 mM of substrate concentration and at pH 9.2 for 60 min at 37 degrees C. We have found that the enzyme was heat sensitive, markedly activated by DMSO and DMF, but no effect was observed with ethanol, ATP or CTP. However, clam ATCase activity was partly inhibited by the addition of CuSO(4) and PHMB to the medium, an inhibition that could be attributed to the presence of SH sites in cysteine residues localized in the catalytic site of this enzyme. All these results will be very useful in the near future to study the gametogenetic process of Mya arenaria, since little is known about the factors that control the physiological process of reproduction in this bivalve of ecological and economic importance. Studies of variations of the activity of aspartate transcarbamylase will also be useful as a potential biomarker to evaluate the disruption of gametogenesis in clams exposed to endocrine disruptors in situ.

Sexual maturation and related changes in aspartate transcarbamylase activity of gonad tissues in the soft shell clam (Mya arenaria).

The information on the relation between the gonadal aspartate transcarbamylase (ACTase) activity and the sexual maturation in molluscs is very fragmentary and is still absent in Mya arenaria. The determination of ATCase activity, energy reserves levels and maturation stages were done in gonads of clams. Results showed that the seasonal cycle of storage and utilization of energy reserves in gonads of clams are linked to the bimodal reproduction well known in this bivalve. ATCase activity was high in clams at development and ripe stages, while this activity was low for individuals found in indifferent, spawning or spent stages. This difference can be explained by the fact that during gonad development, gonadal synthetic activity increased following the mitotic events associated to the reproductive cycle. The results presented in this paper have confirmed the link between ATCase activity and gametogenesis in M. arenaria. Further work should be realized in order to assess if ATCase activity could be considered as a potential biomarker to evaluate the disruption of sexual maturation in clams collected in sites such as the St. Lawrence estuary.