Hydrostatic pressure and cellular respiration: are the values observed post-decompression representative of the reality under pressure?

International audienceThe goal of this article was to assess whether a pressure change can constitute a bias of interpretation of pressure effects on pressure-acclimatized fishes. This work consisted first in a study of the recompression effects of mitochondrial extracts from eels pressure-acclimatized; and then in a study of red muscle fibre compression/decompression. The first experimental series shows a decrease of mitochondrial performances after recompression when compared with the decompressed group. It is concluded that recompression does not allow to get rid of decompression effects. This is confirmed by the second experimental series which show that a decompression induces a stronger reduction of MO2 than the previous compression

Branchial structure and hydromineral equilibrium in juvenile turbot (Scophthalmus maximus) exposed to heavy fuel oil.

International audienceThis study is an attempt to go further in the comprehension of the effects of heavy fuel oil in the context of an accidental oil spill at sea. It focuses on the link between morphological and functional impacts of realistic doses of the dissolved fraction of a heavy fuel oil on fish gills. Juvenile turbot, Scophthalmus maximus were exposed to the dissolved fraction of a heavy fuel oil for 5 days and then placed 30 days in clean sea water for recovery. During the contamination period, the concentration of the 16 US EPA priority poly-aromatic hydrocarbons showed small variations around a mean value of 321.0 ± 9.1 ng l⁻¹ (mean ± SEM). The contamination induced a 64% increase in hepatic cytochrome P 450 1A (Western blot analysis). Osmolality, [Na⁺] and [Cl⁻] rapidly and significantly increased (by 14, 23 and 28% respectively) and slowly decreased to normal levels during the recovery period. At the same time, branchial histology showed decreases in the number of mucocytes (by 30%) and of chloride cells (by 95%) in the interlamellar epithelium. Therefore, it is suggested that the osmotic imbalance observed after the 5 days of exposure to the dissolved fraction of the heavy fuel oil is the consequence of the structural alteration of the gills i.e, the strong reduction of ionocyte numbers

Effect of training frequency on endothelium-dependent vasorelaxation in rats.

International audienceBACKGROUND: Moderate physical activity enhances endothelium-dependent vasorelaxation. Whether the frequency of exercise affects endothelial function is unclear. The purpose of this study was to investigate the effects of various frequencies of training on endothelium-dependent vasorelaxation. DESIGN: Male Wistar rats were trained for 8 weeks on a treadmill at various frequencies [1 (Ex1), 3 (Ex3) or 5 days/week (Ex5)] and compared with age-matched sedentary animals (SED). A control group allowed us to assess endothelial function before the exercise protocol. Rings of thoracic aorta were precontracted with phenylephrine. RESULTS: Endothelium-independent relaxation elicited by sodium nitroprusside was similar in all groups. The maximal response elicited by acetylcholine (ACh) was not different between groups, whereas pD2 values (-logEC50, EC50 being the concentration of ACh that elicited 50% of the maximal response) significantly correlated with frequency of training. nitro-L-arginine methyl ester (L-NAME) reduced the relaxation elicited by 10(-7) mol/l ACh or higher in control and all trained groups, and by 10(-6) mol/l ACh or higher in SED group. Indomethacin inhibited the vasodilating response to 10(-7) mol/l ACh or higher in control, SED and Ex1 groups, and to 10(-8) mol/l or more in Ex3 and Ex5 animals. Tetraethylammonium attenuated the response to 10(-6) mol/l ACh or higher in control and SED groups and to 10(-7) mol/l or more in all trained animals. CONCLUSION: This data suggest that decreased ACh-induced vasorelaxation after physical inactivity may result from impairment of endothelial nitric oxide synthase, prostacyclin and endothelium-derived hyperpolarizing factor pathways. This effect is prevented by training in a frequency-dependent manner

Diving under a Microscope-A New Simple and Versatile In Vitro Diving Device for Fluorescence and Confocal Microscopy Allowing the Controls of Hydrostatic Pressure, Gas Pressures, and Kinetics of Gas Saturation.

International audienceHow underwater diving effects the function of the arterial wall and the activities of endothelial cells is the focus of recent studies on decompression sickness. Here we describe an in vitro diving system constructed to achieve real-time monitoring of cell activity during simulated dives under fluorescent microscopy and confocal microscopy. A 1-mL chamber with sapphire windows on both sides and located on the stage of an inverted microscope was built to allow in vitro diving simulation of isolated cells or arteries in which activities during diving are monitored in real-time via fluorescent microscopy and confocal microscopy. Speed of compression and decompression can range from 20 to 2000 kPa/min, allowing systemic pressure to range up to 6500 kPa. Diving temperature is controlled at 37°C. During air dive simulation oxygen partial pressure is optically monitored. Perfusion speed can range from 0.05 to 10 mL/min. The system can support physiological viability of in vitro samples for real-time monitoring of cellular activity during diving. It allows regulations of pressure, speeds of compression and decompression, temperature, gas saturation, and perfusion speed. It will be a valuable tool for hyperbaric research

Evaluation of chromosomal damage by flow cytometry in turbot (Scophthalmus maximus L.) exposed to fuel oil.

International audienceFlatfishes, turbots (Scophthalmus maximus), were injected intraperitoneally with two doses of fuel oil number 2. Biliary metabolites were evaluated by fixed fluorescence to verify the efficiency of intoxication. Ethoxyresorufin-O-deethylase (EROD) activity was compared with chromosomal damage measured by flow cytometry. The analysis of biliary metabolites showed a good dose-response relation and constitutes a clear reference for the subsequent measurements. Comparing flow cytometry and EROD results, a shorter delay of response for EROD activity was obtained, but chromosomal damage was significant only after one week. The persistence of the EROD response was shorter, while the genotoxic signal still persisted after one month. The measurement of chromosomal damage allowed a good differentiation between the two tested doses. In the case of EROD activity, the results were less clear. The results suggest that within a few weeks after exposure to fuel oil number 2, the measurements of chromosomal damage by flow cytometry can be used to detect a dose-dependent genotoxic response in fish

Impacts of mixtures of herbicides on molecular and physiological responses of the European flounder Platichthys flesus

International audienceThe widespread use of pesticides results in a growing contamination of the aquatic environment. The effects of (1) a simple mixture of a glyphosate-based formulation and AMPA (Aminomethylphosphonic acid -- a primary metabolite of glyphosate) and of (2) a more complex mixture of herbicides (glyphosate/AMPA/mecoprop/acetochlor/2,4D) were explored on the molecular and physiological responses of the European flounder Platichthys flesus, considering a long-term and environmentally realistic contamination. Molecular responses were identified using suppression subtractive hybridization on liver samples: the level of gene transcription was significantly different between contaminated fishes vs control ones for 532 sequences, after a 62-day contamination. Among them, 222 sequences were identified by homology with data-based sequences; they encoded several metabolic pathways including: methionine and lipid metabolism, immunity, protein regulation, coagulation and energetic metabolism. Expression pattern of nine transcripts in the liver was confirmed by real-time PCR. The molecular study underlined that potential markers of liver injury were expressed for both mixtures, in particular betaine homocysteine methyl transferase and chemotaxin. Physiological responses were analysed considering blood parameters and condition factor; after the two months contamination period; no significant physiological difference was detected between contaminated and control fish

Modelling and Simulating Complex Systems in Biology: introducing NetBioDyn: A Pedagogical and Intuitive Agent-Based Software

International audienceModelling and teaching complex biological systems is a difficult process. Multi-Agent Based Simulations (MABS) have proved to be an appropriate approach both in research and education when dealing with such systems including emergent, self-organizing phenomena. This chapter presents NetBioDyn, an original software aimed at biologists (students, teachers, researchers) to easily build and simulate complex biological mechanisms observed in multicellular and molecular systems. Thanks to its specific graphical user interface guided by the multi-agent paradigm, this software does not need any prerequisite in computer programming. It thus allows users to create in a simple way bottom-up models where unexpected behaviours can emerge from many interacting entities. This multi-platform software has been used in middle schools, high schools and universities since 2010. A qualitative survey is also presented, showing its ability to adapt to a wide and heterogeneous audience. The Java executable and the source code are available online at http://virtulab.univ-brest.fr

Can selenium‐enriched spirulina supplementation ameliorate sepsis outcomes in selenium‐deficient animals?

In intensive care units, sepsis is the first cause of death. In this pathology, inflammation and oxidative status play a crucial role in patient outcomes. Interestingly, 92% of septic patients exhibit low selenium plasma concentrations (a component of antioxidant enzymes). Moreover, Spirulina platensis, a blue-green algae, demonstrated anti-inflammatory effects. In this context, the main purpose of our study was to analyze the effect of a selenium-enriched spirulina after a selenium deficiency on sepsis outcome in rats. Sixty-four rats were fed 12 weeks with a selenium-deficient food. After 8 weeks, rats were supplemented (via drinking water) for 4 weeks with sodium selenite (Se), spirulina (Spi), or selenium-enriched spirulina (SeSp). Sepsis was then induced by cecal ligature and puncture, and survival duration was observed. The plasma selenium concentration was measured by ICPMS. Expression of GPx1 and GPx3 mRNA was measured by RT-PCR. Blood parameters (lactates and HCO3− concentrations, pH, PO2, and PCO2) were analyzed at 0, 1, and 2 h as well as inflammatory cytokines (IL-6, TNF-α, IL-10). Sodium selenite and SeSP supplementations restored plasma selenium concentration prior to sepsis. The survival duration of SeSP septic rats was significantly lower than that of selenium-supplemented ones. Gpx1 mRNA was increased after a selenium-enriched spirulina supplementation while Gpx3 mRNA levels remained unchanged. Furthermore, sodium selenite prevented sepsis-induced acidosis. Our results show that on a basis of a Se deficiency, selenium-enriched spirulina supplementations significantly worsen sepsis outcome when compared to Se supplementation. Furthermore, Se supplementation but not selenium-enriched spirulina supplementation decreased inflammation and restored acid–base equilibrium after a sepsis induction

Effect of splenectomy on platelet activation and decompression sickness outcome in a rat model of decompression.

International audienceSplenic platelets have been recognized to have a greater prothrombotic potential than others platelets. We studied whether platelets released by splenic contraction could influence the severity and outcome of decompression sickness (DCS) and bubble-induced platelet activation. Sixteen, male Sprague-Dawley rats were randomly assigned to either a control or a splenectomized group. Both groups were compressed to 1,000 kPa (90 metres' sea water) for 45 min while breathing air before staged decompression (5 min at 200 kPa, 5 min at 160 kPa and 10 min at 130 kPa). The onset time of DCS symptoms and of death were recorded during a 60-min observation period post dive. Parameters measured were platelet factor 4 (PF4) for platelet activation, thiobarbituric acid reactive substances (TBARS) for oxidative stress status and Von Willebrand factor (VWf) for endothelial activation. There were no differences between the groups in DCS outcome or in PF4, TBARS and VWf concentrations. These results do not support that the spleen and its exchangeable platelet pool is involved in DCS pathogenesis in a rat model, invalidating the hypothesis that increased decompression-induced platelet aggregation could be influenced by splenic contraction and then play a role in DCS outcome