Polychlorinated Biphenyls and Biotransformation Enzymes in Three Species of Sea Turtles from the Baja California Peninsula of Mexico

Concentrations of polychlorinated biphenyls (PCBs) as well as the expression patterns of cytochrome P450 (CYP) enzymes and glutathione-S-transferase (GST) activities were measured in livers of loggerhead (Caretta caretta), green (Chelonia mydas), and olive ridley (Lepidocheyls olivacea) sea turtles from the Baja California peninsula of Mexico. The mean concentrations of total PCBs were 18.1, 10.5, and 15.2 ng/g wet weight (ww) respectively for the three species and PCB 153 was the dominant congener in all samples. Total PCB concentrations were dominated by penta- and hexa-chlorinated biphenyls. The mean estimated TEQs were 42.8, 22.9, and 10.4 pg/g (ww) for loggerhead, green, and olive ridley, respectively, and more than 70% was accounted for by non-ortho PCBs. Western blots revealed the presence of hepatic microsomal proteins that cross-reacted with anti-CYP2K1 and anti-CYP3A27 antibodies but not with anti-CYP1A antibody. There were no significant differences in GST activities between species. Grouping congeners based on structure–activity relationships for CYP isoenzymes suggested limited activity of CYP1A contribution to PCB biotransformation in sea turtles. These results suggest potential accumulation of PCBs that are CYP1A substrates and provide evidence for biotransformation capacity, which differs from known animal models, highlighting the need for further studies in reptiles, particularly those threatened with extinction

Response of the Pacific oyster Crassostrea gigas to hypoxia exposure under experimental conditions.

International audienceThe molecular response to hypoxia stress in aquatic invertebrates remains relatively unknown. In this study, we investigated the response of the Pacific oyster Crassostrea gigas to hypoxia under experimental conditions and focused on the analysis of the differential expression patterns of specific genes associated with hypoxia response. A suppression subtractive hybridization method was used to identify specific hypoxia up- and downregulated genes, in gills, mantle and digestive gland, after 7-10 days and 24 days of exposure. This method revealed 616 different sequences corresponding to 12 major physiological functions. The expression of eight potentially regulated genes was analysed by RT-PCR in different tissues at different sampling times over the time course of hypoxia. These genes are implicated in different physiological pathways such as respiration (carbonic anhydrase), carbohydrate metabolism (glycogen phosphorylase), lipid metabolism (delta-9 desaturase), oxidative metabolism and the immune system (glutathione peroxidase), protein regulation (BTF3, transcription factor), nucleic acid regulation (myc homologue), metal sequestration (putative metallothionein) and stress response (heat shock protein 70). Stress proteins (metallothioneins and heat shock proteins) were also quantified. This study contributes to the characterization of many potential genetic markers that could be used in future environmental monitoring, and could lead to explore new mechanisms of stress tolerance in marine mollusc species

High anoxia tolerance in the subterranean salamander Proteus anguinus without oxidative stress nor activation of antioxidant defenses during reoxygenation

The present study describes a high anoxia tolerance in an amphibian at high temperature. Indeed, the subterranean salamander Proteus anguinus survived 12 h under anoxia at 12°C. Surprisingly, such experimental conditions did not affect P. anguinus oxidative status while muscles and liver antioxidant enzymes activities decreased under 8 h anoxia and only return to basal level during reoxygenation. To test if such adaptation is common in Urodels, equivalent experimentations have been conducted on another newt: the stream-dwelling Calotriton asper. This latter species exhibited only 1.5 h survival under anoxia in spite of higher antioxidant enzymes activities than P. anguinus. Furthermore, aerobic recovery after 1 h anoxia induced a 30% increase of oxidative damage partly explained by SOD and CAT activities that did not return to control values during reoxygenation, demonstrating a lower capacity to counteract ROS overproduction than P. anguinus. In addition, uncoupling protein (UCP) transcript was for the first time detected, partly sequenced and quantified in amphibian muscles and liver. UCP may be considered as a ROS production attenuator by mediating a discharge of the proton gradient generated by the respiratory chain. The putative role of UCP in post-anoxic oxidative status of both species is discussed