Are yellow eels from Lake Balaton able to cope with high pressure encountered during migration to the Sargasso sea? The case of energy metabolism

Eels from Lake Balaton are unique because they do not undergo the silvering process and do not migrate. The question is whether these eels, despite such particularities, retain their ability to cope with migration constraints, usually high pressure. To ascertain this, eels were exposed for 3 days to 10.1 MPa of hydrostatic pressure (HP) and the effects of this on aerobic metabolism were evaluated by measuring oxygen consumption (MO2), Cytochrome Oxydase activity (COX) and energetic nucleotide contents in red and white muscles. The results show that Balaton eels survive HP. However, 3 days under pressure induces an alteration in aerobic metabolism. Moreover, when only muscle fibres are exposed to HP, there is a significant decrease in maximal aerobic capacities (-20%). The results are discussed in terms of the ability of these eels to migrate, bearing in mind that this activity represents a high percentage of maximal aerobic capacity when compared with other populations

Pressure effects on membrane-based functions and energy metabolism: a review

This review will consider the effects of hydrostatic pressure on some cellular functions related to membrane- localized processes. After a general survey of experimental evidence showing the wide variety of membrane- linked mechanisms that are perturbed by changes in hydrostatic pressure, it will focus on the pressure-sensitivity of the processes involved in ionic and osmotic regulation in crabs and fish, including membrane-localized ATPases and oxidative metabolism. The results of long-term exposure (30 days) of freshwater eels Anguilla anguilla at 101 ATA of hydrostatic pressure clearly indicate Na+ balance impairment at the tissue level (muscle and gill). That impairment occurs at the same time as a new state of energetic metabolism which results from adjustments of intertissue coupling of anaerobic and aerobic metabolisms. Considering its life cycle, however, Anguilla can reasonably be considered as ‘preadapted’ to pressure. Experiments conducted on the crab Eriocheir sinensis, which normally never encounters high levels of pressure, show that physiological processes involved in hydromineral balance control are outstandingly resistant to pressure. Disturbances in hydromineral balance and energetic metabolism are rapidly corrected and adjusted to a new state of activity

Androgen-dependent stimulation of brain dopaminergic systems in the female European eel (Anguilla anguilla).

Dopamine (DA), a neurotransmitter present in all vertebrates, is involved in processes such as motor function, learning and behavior, sensory activities, and neuroendocrine control of pituitary hormone release. In the female eel, we analyzed how gonadal steroids regulate brain expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of DA. TH mRNA levels were assayed by quantitative real-time RT-PCR. TH-positive nuclei were also localized by in situ hybridization (ISH) and immunohistochemistry, and the location of TH nuclei that project to the pituitary was determined using 1,1'-dioctadecyl-3,3,3',3'-tetramethylindicarbocyanine perchlorate retrograde tracing. Chronic in vivo treatment with testosterone increased TH mRNA specifically in the periglomerular area of the olfactory bulbs and in the nucleus preopticus anteroventralis (NPOav). NPOav was labeled with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindicarbocyanine perchlorate, showing that this nucleus is hypophysiotropic in the eel. The nonaromatizable 5alpha-dihydrotestosterone gave identical results in both areas, whereas 17beta-estradiol had no stimulatory effect, showing that the observed stimulatory effects of testosterone were androgen dependent. In teleosts, DA neurons originating from the NPOav directly inhibit gonadotropic function, and our results indicate an androgen-dependent, positive feedback on this neuroendocrine control in the eel. In mammals, DA interneurons in the olfactory bulbs are involved in the enhancement of olfactory sensitivity and discrimination. Our results in the European eel suggest an androgen-dependent stimulation of olfactory processing, a sensory function believed to be important in eel navigation during its reproductive migration toward the oceanic spawning grounds. To our knowledge, this is the first evidence from any vertebrate of an androgen-dependent effect on DAergic activity in the olfactory bulbs, providing a new basis for understanding the regulation by gonadal steroids of central DAergic systems in vertebrates

Thrombin modifies growth, proliferation and apoptosis of human colon organoids: a protease-activated receptor 1- and protease-activated receptor 4-dependent mechanism

International audienceExperimental Approach: Crypts were isolated from human colonic resections and cultured for 6 days, forming human colon organoids. Cultured organoids were exposed to 10 and 50 mU·mL−1 of thrombin, in the presence or not of protease‐activated receptor (PAR) antagonists. Organoid morphology, metabolism, proliferation and apoptosis were followed.Key Results: Thrombin favoured organoid maturation leading to a decreased number of immature cystic structures and a concomitant increased number of larger structures releasing cell debris and apoptotic cells. The size of budding structures, metabolic activity and proliferation were significantly reduced in organoid cultures exposed to thrombin, while apoptosis was dramatically increased. Both PAR1 and PAR4 antagonists inhibited apoptosis regardless of thrombin doses. Thrombin‐induced inhibition of proliferation and metabolic activity were reversed by PAR4 antagonist for thrombin's lowest dose and by PAR1 antagonist for thrombin's highest dose.Conclusions and Implications: Overall, our data suggest that the presence of thrombin in the vicinity of human colon epithelial cells favours their maturation at the expense of their regenerative capacities. Our data point to thrombin and its two receptors PAR1 and PAR4 as potential molecular targets for epithelial repair therapies

Pressure resistance of aerobic metabolism in eels from different water environments.

International audienceEels from different locations were tested comparing their energetic capacities to migrate by studying muscle (red and white) aerobic metabolism. As the migratory activity corresponds to a lengthy swimming activity at depth, their pressure resistance was evaluated by considering fish response to compression, mitochondrial respiration measured under pressure (101 ATA) and cytochrome c oxidase after 3 days under pressure. The results show that only fish from two of the sites have the metabolic capacities to cope with the high pressure encountered during migration

Glycolytic fluxes in European silver eel, Anguilla anguilla: sex differences and temperature sensitivity.

International audienceEuropean silver eels migrate 6000 km to their supposed spawning area in the Sargasso sea. As the eel is fasting, this intense swimming activity is realised only with fat stores, involving mainly red muscle i.e. aerobic metabolism. However, eel migration is performed at depth and thus in cold water, both being known to induce changes in muscle energy metabolism. During migration, white and red muscles can operate together or separately in order to counteract the eventual effects of low temperatures and/or high pressures. We have studied the temperature sensitivity (5, 15, and 25 degrees C) of aerobic and anaerobic metabolism in both sexes. At the same temperature, migrating eels have a higher basal glycolytic flux. Moreover, there are temperature and sex effects: anaerobic glycolysis (JB) is more sensitive to cold water whereas aerobic (JA) is more affected by warm. Males, which are less sensitive to cold water, also have higher aerobic fluxes than females. As depth corresponds to low temperature, the possibility that males migrate more deeply than females is discussed. In an ecophysiological context, it is interesting to suppose that males and female eels migrate at different depths in order to optimize their energy utilization by aerobic and / or anaerobic pathways

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

Improvement in the efficiency of oxidative phosphorylation in the freshwater eel acclimated to 10.1 MPa hydrostatic pressure.

International audiencePrevious studies have suggested that the efficiency of oxidative phosphorylation in the freshwater eel (Anguilla anguilla) is increased after acclimation to high hydrostatic pressure. Analysis at atmospheric pressure of the respiratory chain complexes showed that, after 21 days at 10.1 MPa, the activity of complex II was decreased to approximately 50 % (P<0.01) of the control value and that cytochrome c oxidase (complex IV) activity was significantly increased to 149 % of the control value (P<0.05). ADP/O ratios calculated from mitochondrial respiration measurements were significantly increased after acclimation to high hydrostatic pressure (2.87 versus 2.52, P<0.001) when measured in the presence of pyruvate plus malate at atmospheric pressure. These results clearly show an increased oxidative phosphorylation efficiency in response to high-pressure acclimation

Material classification from imprecise chemical composition : probabilistic vs possibilistic approach

International audienceIn this paper we propose a method of explainable material classification from imprecise chemical compositions. The problem of classification from imprecise data is addressed with a fuzzy decision tree whose terms are learned by a clustering algorithm. We deduce fuzzy rules from the tree, which will provide a justification of the result of the classification. Two opposed approaches are compared : the probabilistic approach and the possibilistic approach

Vers la classification de matériaux à partir de compositions chimiques incertaines

I.S.B.N. : 9782364936140National audienceIn this paper, a study about the classification of materials from their chemical composition is realized. The used method relies on a fuzzy decision tree and focuses on handling the uncertainty of the data by a technique we will explain. The complete algorithm is tested on simulated data sets, in the expectation of real data.Dans cet article, une étude sur la classification de matériaux à partir de leur composition chimique est réalisée. La méthode utilisée se base sur un arbre de décision flou et l'accent est mis sur la gestion de l'incertitude des données, qui fait l'objet d'un traitement particulier que nous exposerons. L'algorithme complet est testé sur des jeux de données simulés, dans l'attente de données réelles