Evaluating the ecological impact of an oil spill is a complex issue requiring coherently articulated examination of the sequence of interactions that link the cell, where contaminants exert their effects, to the ecosystem, where interactions with human activities arise. This sequence of interactions traverses the frontiers between scientific disciplines (chemistry, toxicology, physiology, and fisheries ecology). Using the common sole (Solea solea L.) as a model species for the coastal habitats polluted by the "Erika" oil spill, our research project attempted to define indices of functional integrity that characterised the consequences of fuel exposure at the different biological levels. The coupling of field observations with experimental laboratory work revealed how functional alterations which are readily observable within individuals and their organs are progressively obscured as investigation progresses towards more complex organisational levels. Some of the approaches and indices are proposed as instruments for evaluating the impact of contamination by hydrocarbons.

We used three inbred rat strains known for significant differences in the activity and reactivity of their hypothalamic-pituitary-adrenal (HPA) axis to stress [Fischer 344 (F344), Brown Norway (BN) and Lewis (Lew) rats] to search for a strain difference in the paradoxical increase in running activity induced by food restriction and to explore the role of the HPA axis in this behaviour. Rats were randomly assigned to either an ad lib sedentary group (AL), a control wheel activity group (ACT), a food restriction-induced hyperactivity group (FR-ACT) group (1.5 h/day ad lib food, 22.5 h/day ad lib wheel access) or a pair-fed group (FR). The BN and Lew rats reached the 25% body weight-loss criterion of FR-ACT (strain effect: F(2,132) = 45.58, P < 10-6) faster than the F344 strain due to higher food restriction-induced running activity (strain effect: F(2,65) = 17.43, P = 0.00001). FR and FR-ACT decreased thymus weight (marker of integrated HPA axis activation) in all strains. In Lew and BN strains, FR-ACT induced a further decrement on thymus weight compared to their FR group. Prefeeding corticosterone levels (15.00 h) increased during the study in BN and Lew FR-ACT rats, but not in F344. Total wheel turns were correlated to both final adipose weight (r = -0.49, P = 0.002) and thymus weight decrement (r = 0.59, P = 0.0001), emphasizing the relationship between fat mass and HPA axis activation in excessive running activity. Increased running in conditions of food restriction and HPA axis activation may be linked at the level of the central nervous system. However, the involvement of corticotrophin-releasing hormone, agouti-related peptide or cocaine- and amphetamine-regulated transcript in behavioural disturbances of FR-ACT rats was excluded (in situ hybridization). We propose that corticosterone may be the link between initial low levels of fat mass and/or rate of fat mass loss (peripheral energy stores) and increased wheel activity, favouring fueling through lipolysis and proteolysis and reinforcing the self starvation via reward mechanisms, thus establishing a deleterious vicious cycle.

The current results demonstrate that postconditioning hypothermia was associated with increased survival duration during experimental sepsis. Whether the observed benefits on survival duration are due to potential impacts on energy metabolism or to an anti-inflammatory effect of hypothermia requires further investigation.

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