Zebrafish: A model animal for analyzing the impact of environmental pollutants on muscle and brain mitochondrial bioenergetics.
Mercury, anthropogenic release of uranium (U), and nanoparticles constitute hazardous environmental pollutants able to accumulate along the aquatic food chain with severe risk for animal and human health. The impact of such pollutants on living organisms has been up to now approached by classical toxicology in which huge doses of toxic compounds, environmentally irrelevant, are displayed through routes that never occur in the lifespan of organisms (for instance injecting a bolus of mercury to an animal although the main route is through prey and fish eating). We wanted to address the effect of such pollutants on the muscle and brain mitochondrial bioenergetics under realistic conditions, at unprecedented low doses, using an aquatic model animal, the zebrafish Danio rerio. We developed an original method to measure brain mitochondrial respiration: a single brain was put in 1.5mL conical tube containing a respiratory buffer. Brains were gently homogenized by 13 strokes with a conical plastic pestle, and the homogenates were immediately used for respiration measurements. Skinned muscle fibers were prepared by saponin permeabilization. Zebrafish were contaminated with food containing 13μg of methylmercury (MeHg)/g, an environmentally relevant dose. In permeabilized muscle fibers, we observed a strong inhibition of both state 3 mitochondrial respiration and cytochrome c oxidase activity after 49 days of MeHg exposure. We measured a dramatic decrease in the rate of ATP release by skinned muscle fibers. Contrarily to muscles, brain mitochondrial respiration was not modified by MeHg exposure although brain accumulated twice as much MeHg than muscles. When zebrafish were exposed to 30μg/L of waterborne U, the basal mitochondrial respiratory control ratio was decreased in muscles after 28 days of exposure. This was due to an increase of the inner mitochondrial membrane permeability. The impact of a daily ration of food containing gold nanoparticles of two sizes (12 and 50nm) was investigated at a very low dose for 60 days (40ng gold/fish/day). Mitochondrial dysfunctions appeared in brain and muscle for both tested sizes. In conclusion, at low environmental doses, dietary or waterborne heavy metals impinged on zebrafish tissue mitochondrial respiration. Due to its incredible simplicity avoiding tedious and time-consuming mitochondria isolation, our one-pot method allowing brain respiratory analysis should give colleagues the incentive to use zebrafish brain as a model in bioenergetics. This article is part of a Directed Issue entitled: Bioenergetic dysfunction, adaptation and therapy.
(International Journal of Biochemistry and Cell Biology. vol. 45, n° 1357-2725, pp. 16-22, 13/04/2026)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IBGC, UB, CNRS
Long term effects of polycyclic aromatic hydrocarbons on zebrafish behavioral and reproduction responses
(13/04/2026)
BE, IFREMER, UB, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LRHLR, HGS, IFREMER, LPGP, INRA, Biosit : Biologie - Santé - Innovation Technologique
A note about the critical bandwidth for a kernel density estimator with the uniform kernel
Among available bandwidths for kernel density estimators, the critical bandwidth is a data-driven one, which satisfies a constraint on the number of modes of the estimated density. When using a random bandwidth, it is of particular interest to show that it goes toward 0 in probability when the sample size goes to infinity. Such a property is important to prove satisfying asymptotic results about the corresponding kernel density estimator. It is shown here that this property is not true for the uniform kernel.
(17/12/2012)
IMB, UB, Bordeaux INP, CNRS, CQFD, IMB, UB, Bordeaux INP, CNRS, Inria, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LMBA, UBS, UBO EPE, CNRS
High-resolution architecture of a polygonal fault interval inferred from geomodel applied to 3D seismic data from the Gjallar Ridge, Vøring Basin, Offshore Norway
3D seismic data located in the Gjallar Ridge (Vøring Basin, offshore Norway) reveals a closely-spaced polygonal fault system affecting more than 800 m of homogeneous mud-dominated Quaternary and Tertiary sequences. As some faults reach the modern seafloor, they represent an active polygonal fault system at present day. Even if the processes remain unclear and are still under debate, it is generally agreed that the initiation of polygonal faults is the result of shallow burial dewatering of fine-grained unconsolidated sediments by volumetric compaction. 3D seismic data are commonly interpreted by propagating horizons automatically and by picking faults manually. However, in the case of polygonal fault intervals, this approach is time consuming due to the huge number of faults and because automatic propagation can be misleading. In this study, we applied a new technique of 3D seismic interpretation based on a sequential stratigraphy analysis, using the new PaleoScan© software (Eliis Company). It allowed us to build a 3D geological model computing more than 300 horizons within the faulted intervals. We then used the coherency attribute, depicting anomalies in the shape of seismic waveform like faults, in order to constrain a possible link between fault distribution and stratigraphic levels. Our approach allows fault throws to be calculated in milliseconds on any polygonal fault plane. The result shows that fault segments have been reactivated by dip-linkage. Distribution of faults depends on mechanical units, intervals characterized by different petrophysical properties, which are independent from lithological and diagenetic changes. According to these results, we propose a model showing the evolution of polygonal fault intervals in which faulting stages are separated by a quiescence phase during burial. A first tier of polygonal faults is initiated at a specific depth, according to the Cam-clay model. Then, following a period of quiescence during which mud-rich sediments continued to accumulate, new fault segments are initiated above the first mechanical unit and within this undeformed interval. New nucleated faults then connect downward to pre-existing underlying polygonal fault system, thus progressively increasing the thickness of the faulted interval.
(Marine Geology. vol. 332-334, n° 0025-3227, pp. 134-161, 01/12/2012)
UAG, INSU - CNRS, UM, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, NOC, Géosciences Montpellier, UAG, INSU - CNRS, UM, CNRS, UiO, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS
Early mid-Holocene SST variability and surface-ocean water balance in the southwest Pacific
[1] We present early mid-Holocene records of Sr/Ca,δ18O and δ18Osw from marine archives collected in Vanuatu: two Porites sp. corals (6.7–6.5 ka BP) and a Tridacna maxima giant clam (6.2–6.0 ka BP). Sr/Ca, δ18O, and δ18Osw were used as proxies for sea surface temperature (SST) and sea surface salinity (SSS). The fossil geochemical records were compared to modern Porites sp. and T. maxima records. Reconstructed mean SSTs from the two fossil Porites sp.and from the modern coral are similar, implying that the Western Pacific Warm Pool (WPWP)' southern edge had reached its modern location by 6.7–6.5 ka BP. The post-glacial SST rise in the Southwest Pacific was thus completed by the early mid-Holocene. The two early mid-Holocene corals and the giant clam recorded saltier conditions than modern related to 1) a decoupling between the precipitation regime and the SPCZ due to a northerly position of this climatic feature and 2) an increase of the moisture transport to the extra-tropics, driven by a strengthened or extended Hadley cell. The longest δ18O coral profile displays an El Niño Southern Oscillation (ENSO) signal reduced by 20–30% compared to the period 1928–1992, in concordance with the reduced ENSO variability observed in the Pacific area during the first half of the Holocene. However, the decoupling between the SPCZ and the precipitation regime may have also contributed to the weak ENSO signal recorded in the early mid-Holocene coral δ18O profile.
(Paleoceanography. vol. 27, n° 0883-8305, 01/12/2012)
PALEOPROXUS, LOCEAN, IPSL, ENS-PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LEGOS, IRD, UT3, Comue de Toulouse, INSU - CNRS, CNES, CNRS, LOCEAN, IPSL, ENS-PSL, PSL, UVSQ, UPMC, CEA, INSU - CNRS, X, IP Paris, CNES, CNRS, MNHN, IRD, UPMC, INSU - CNRS, CNRS
In situ study of short-term variations of redox species chemistry in intertidal permeable sediments of the Arcachon lagoon
(Hydrobiologia. vol. 699, n° 0018-8158, pp. 69-84, 01/12/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LPG-ANGERS, LPG, UA, UN UFR ST, UN, INSU - CNRS, CNRS
Seagrass burial by dredged sediments: Benthic community alteration, secondary production loss, biotic index reaction and recovery possibility
In 2005, dredging activities in Arcachon Bay (France) led in burying 320,000m(2) of Zostera noltii intertidal seagrass. Recovery by macrobenthos and seagrass was monitored. Six months after works, seagrass was absent and macrobenthos drastically different from surrounding vegetated stations. Rapidly and due to sediment dispersal, disposal area was divided into a sandflat with a specific benthic community which maintained its difference until the end of the survey (2010), and a mudflat where associated fauna became similar to those in adjacent seagrass. Macrobenthic community needs 3years to recover while seagrass needs 5years to recover in the station impacted by mud. The secondary production loss due to works was low. In this naturally carbon enriched system, univariate biotic indices did not perform well to detect seagrass destruction and recovery. Multivariate index MISS gave more relevant conclusions and a simplified version was tested with success, at this local scale.
(Marine Pollution Bulletin. vol. 64, n° 0025-326X, pp. 2340-2350, 01/11/2012)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Accounting for Rough Bed Friction Factors of Mud Beds as a Result of Biological Activity in Erosion Experiments
(Journal of Hydraulic Engineering. vol. 138, n° 0733-9429, pp. 979-984, 01/11/2012)
LECOB, OOB, UPMC, CNRS, UPMC, CNRS, BOREA, UNICAEN, NU, MNHN, IRD, SU, CNRS, UA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFREMER
Antarctic temperature changes during the last millennium: evaluation of simulations and reconstructions
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a b s t r a c t Temperature changes in Antarctica over the last millennium are investigated using proxy records, a set of simulations driven by natural and anthropogenic forcings and one simulation with data assimilation. Over Antarctica, a long term cooling trend in annual mean is simulated during the period 1000e1850. The main contributor to this cooling trend is the volcanic forcing, astronomical forcing playing a dominant role at seasonal timescale. Since 1850, all the models produce an Antarctic warming in response to the increase in greenhouse gas concentrations. We present a composite of Antarctic temperature, calculated by averaging seven temperature records derived from isotope measurements in ice cores. This simple approach is supported by the coherency displayed between model results at these data grid points and Antarctic mean temperature. The composite shows a weak multi-centennial cooling trend during the pre-industrial period and a warming after 1850 that is broadly consistent with model results. In both data and simulations, large regional variations are superimposed on this common signal, at decadal to centennial timescales. The model results appear spatially more consistent than ice core records. We conclude that more records are needed to resolve the complex spatial distribution of Antarctic temperature variations during the last millennium.
(Quaternary Science Reviews. vol. 55, n° 0277-3791, pp. 75-90, 01/11/2012)
TECLIM, ELI, UCLouvain, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, GLACCIOS, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, BAS, NERC, AWI, LAL, UP11, IN2P3, CNRS, UvA, ACE-CRC, UGent
Evaluating Southern Ocean sea-ice for the Last Glacial Maximum and pre-industrial climates: PMIP-2 models and data evidence
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: a b s t r a c t Sea ice is recognized as an important factor controlling climate conditions at high latitudes. It has a major impact in controlling the ocean to atmosphere exchanges (e.g. for CO 2) as well as surface oceanic conditions and deep water formation in the high latitude oceans. Being at the interface of two major components of the climate system, sea ice is useful to evaluate and intercompare different climate models. We here analyze the results of eight coupled climate models (from which seven are from the PMIP-2 database) against available reconstructions for winter and summer sea ice extent around Antarctica. To evaluate the ability of models in representing different climate states, we compare their results for both the pre-industrial and the Last Glacial Maximum (LGM). We find that models generally have identical seasonal ranges for the two climate states analyzed, which is not supported by data inferences. Indeed, data indicate that the LGM seasonality was enhanced compared to the pre-industrial. The shape of the sea ice distribution is also different in models (circular around the Antarctic continent) and in reconstructions (oval-shaped distribution; similar to modern sea ice distribution). We show that models underestimating the sea ice extent for the pre-industrial are also underestimating the Last Glacial Maximum extent. Our results thus point to difficulties for climate models in representing the sea-ice dynamics in the Southern Ocean.
(Quaternary Science Reviews. vol. 56, n° 0277-3791, pp. 99-106, 01/11/2012)
LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UvA