Temporal patterns in dolphin foraging activity in the Mediterranean Sea: insights from vocalisations recorded during the ACCOBAMS Survey Initiative

Marine organisms continually adapt their physiology and behaviour to temporal variations in their environment, resulting in diurnal rhythmic behaviour, particularly when foraging. In delphinids, these rhythms can be studied by recording echolocation clicks, which can provide indicators of foraging activity. The foraging rhythms of delphinids and their relationship to temporal parameters are poorly documented and most studies so far have used moored passive acoustic systems. The present study provides, for the first time, information on the activity rhythms of delphinids investigated in relation with temporal variables at a basin scale from a moving platform, in the western and central Mediterranean Sea. We used passive acoustic recordings collected by hydrophones towed along transect lines during the ACCOBAMS Survey Initiative in the summer 2018. We extracted variables that may influence daily and monthly rhythms, including time of day, lunar cycle, lunar illumination and sea state and fitted generalised additive models. The nycthemeral and lunar cycles were the two main factors influencing dolphin activity rhythms. Echolocation activity was predominant at night, with a maximum of 0.026 acoustic events per minute at 21:00/22:00 compared to as few as 0.0007 events per minute at 11:00. These events were also more frequent during the third quarter of the moon; 0.033 acoustic events on day 22 of the lunar cycle as opposed to 0.0008 on day 8 of the lunar cycle, corresponding to the first quarter of the moon. Variations in the echolocation activity of delphinids in the Mediterranean Sea could reflect variation in their foraging effort and be related to prey density, composition, accessibility and catchability within dolphin foraging depth range. These results should also improve interpretation of passive acoustic monitoring data

Archives et sciences sociales

Séminaire collectif sous la responsabilité d’Éric Brian, Jean Jamin, directeurs d’étudesMorgane Labbé, Pap Ndiaye, maîtres de conférencesVincent Duclert, professeur agrégé Expériences III La première séance de l’année a porté sur le rôle et l’importance des archives dans l’édition. Animée par Vincent Duclert et Jean Jamin, elle a donné successivement la parole à Jacques Revel qui a longtemps co-dirigé la collection « Archives » de Julliard/Gallimard, puis à Hugues Pradier qui dirige actuellem..

Multiparametric radiobiological assays show that variation of X-ray energy strongly impacts relative biological effectiveness: comparison between 220 kV and 4 MV

International audienceBased on classic clonogenic assay, it is accepted by the scientific community that, whatever the energy, the relative biological effectiveness of X-rays is equal to 1. However, although X-ray beams are widely used in diagnosis, interventional medicine and radiotherapy, comparisons of their energies are scarce. We therefore assessed in vitro the effects of low- and high-energy X-rays using Human umbilical vein endothelial cells (HUVECs) by performing clonogenic assay, measuring viability/mortality, counting γ-H2AX foci, studying cell proliferation and cellular senescence by flow cytometry and by performing gene analysis on custom arrays. Taken together, excepted for γ-H2AX foci counts, these experiments systematically show more adverse effects of high energy X-rays, while the relative biological effectiveness of photons is around 1, whatever the quality of the X-ray beam. These results strongly suggest that multiparametric analysis should be considered in support of clonogenic assay

Superplasticity in Fine Grain Ti-6Al-4V Alloy: Mechanical Behavior and Microstructural Evolution

Titanium Ti-6Al-4V alloys are known to exhibit interesting superplastic properties for different conditions of temperature and strain rate, depending on the initial grain size. Even if superplasticity is generally explained in terms of grain boundary sliding (GBS) accompanied by several accommodation mechanisms, it appears that the micromechanisms of superplasticity are still controversial especially at the grain scale and even more at lower scale. These micromechanisms, involving microstructural evolution, depend also on the SPF conditions (temperature, strain rate and initial microstructure). In this study, the flow stress in the Ti-6Al-4V alloy is investigated for different strain rate and for temperature in the range of the α/β transformation. The preferred orientation evolution of alpha phase grains for different percentage of deformation is studied for a non-optimal SPF regime (920°C-10-4 s-1) in order to highlight the microstructural evolution and so the deformation mechanisms involved. For that, mechanical interrupted test combined with Scanning Electron Microscopy (SEM) and Electron Back Scatter Diffraction (EBSD) are used

Tau seeds from Alzheimer's disease brains trigger tau spread in macaques while oligomeric-Aβ mediates pathology maturation

INTRODUCTION: The “prion-like” features of Alzheimer's disease (AD) tauopathy and its relationship with amyloid-β (Aβ) have never been experimentally studied in primates phylogenetically close to humans. METHODS: We injected 17 macaques in the entorhinal cortex with nanograms of seeding-competent tau aggregates purified from AD brains or control extracts from aged-matched healthy brains, with or without intracerebroventricular co-injections of oligomeric-Aβ. RESULTS: Pathological tau injection increased cerebrospinal fluid (CSF) p-tau181 concentration after 18 months. Tau pathology spreads from the entorhinal cortex to the hippocampal trisynaptic loop and the cingulate cortex, resuming the experimental progression of Braak stage I to IV. Many AD-related molecular networks were impacted by tau seeds injections regardless of Aβ injections in proteomic analyses. However, we found mature neurofibrillary tangles, increased CSF total-tau concentration, and pre- and postsynaptic degeneration only in Aβ co-injected macaques. DISCUSSION: Oligomeric-Aβ mediates the maturation of tau pathology and its neuronal toxicity in macaques but not its initial spreading. Highlights: This study supports the “prion-like” properties of misfolded tau extracted from AD brains. This study empirically validates the Braak staging in an anthropomorphic brain. This study highlights the role of oligomeric Aβ in driving the maturation and toxicity of tau pathology. This work establishes a novel animal model of early sporadic AD that is closer to the human pathology

Type 1 interferons and Foxo1 down-regulation play a key role in age-related T-cell exhaustion in mice

Foxo family transcription factors are critically involved in multiple processes, such as metabolism, quiescence, cell survival and cell differentiation. Although continuous, high activity of Foxo transcription factors extends the life span of some species, the involvement of Foxo proteins in mammalian aging remains to be determined. Here, we show that Foxo1 is down-regulated with age in mouse T cells. This down-regulation of Foxo1 in T cells may contribute to the disruption of naive T-cell homeostasis with age, leading to an increase in the number of memory T cells. Foxo1 down-regulation is also associated with the up-regulation of co-inhibitory receptors by memory T cells and exhaustion in aged mice. Using adoptive transfer experiments, we show that the age-dependent down-regulation of Foxo1 in T cells is mediated by T-cell-extrinsic cues, including type 1 interferons. Taken together, our data suggest that type 1 interferon-induced Foxo1 down-regulation is likely to contribute significantly to T-cell dysfunction in aged mice

Development of the neurons controlling fertility in humans: new insights from 3D imaging and transparent fetal brains

Fertility in mammals is controlled by hypothalamic neurons that secrete gonadotropin-releasing hormone (GnRH). These neurons differentiate in the olfactory placodes during embryogenesis and migrate from the nose to the hypothalamus before birth. Information regarding this process in humans is sparse. Here, we adapted new tissue-clearing and whole-mount immunohistochemical techniques to entire human embryos/fetuses to meticulously study this system during the first trimester of gestation in the largest series of human fetuses examined to date. Combining these cutting-edge techniques with conventional immunohistochemistry, we provide the first chronological and quantitative analysis of GnRH neuron origins, differentiation and migration, as well as a 3D atlas of their distribution in the fetal brain. We reveal not only that the number of GnRH-immunoreactive neurons in humans is significantly higher than previously thought, but that GnRH cells migrate into several extrahypothalamic brain regions in addition to the hypothalamus. Their presence in these areas raises the possibility that GnRH has non-reproductive roles, creating new avenues for research on GnRH functions in cognitive, behavioral and physiological processes

A functional network of highly pure enteric neurons in a dish

The enteric nervous system (ENS) is the intrinsic nervous system that innervates the entire digestive tract and regulates major digestive functions. Recent evidence has shown that functions of the ENS critically rely on enteric neuronal connectivity; however, experimental models to decipher the underlying mechanisms are limited. Compared to the central nervous system, for which pure neuronal cultures have been developed for decades and are recognized as a reference in the field of neuroscience, an equivalent model for enteric neurons is lacking. In this study, we developed a novel model of highly pure rat embryonic enteric neurons with dense and functional synaptic networks. The methodology is simple and relatively fast. We characterized enteric neurons using immunohistochemical, morphological, and electrophysiological approaches. In particular, we demonstrated the applicability of this culture model to multi-electrode array technology as a new approach for monitoring enteric neuronal network activity. This in vitro model of highly pure enteric neurons represents a valuable new tool for better understanding the mechanisms involved in the establishment and maintenance of enteric neuron synaptic connectivity and functional networks

Distribution patterns of marine megafauna density in the Mediterranean Sea assessed through the ACCOBAMS Survey Initiative (ASI)

The ACCOBAMS Survey Initiative (ASI) is the first synoptic large-scale survey of the entire ACCOBAMS Area and as such it plays a key role in filling the current gaps in our biological and ecological knowledge of large vertebrate species occurring in the region. Data gathered during the ASI were analyzed in a distance sampling surface-modelling framework to assess the summer distribution, densities and patterns, as well as to investigate the correlates of these parameters, for large vertebrate species and taxa in the Mediterranean Basin. Static and dynamic explanatory variables, including water depth (m), distance to depth contours (km), distance to canyons and seabed slope (km), sea surface temperature (°C), mixed layer depth (m) and levels of chlorophyll-a (mg/l), were considered to predict density and compute its variance spatially at a resolution of 10x10 km. A strong longitudinal gradient from low densities in the east to high densities in the west is shared by most taxa. In addition, several taxa also showed a less marked latitudinal gradient varying in direction according to species, and finally, a few of them exhibited patchy distributions

Dominant ACO2 mutations are a frequent cause of isolated optic atrophy.

Biallelic mutations in ACO2, encoding the mitochondrial aconitase 2, have been identified in individuals with neurodegenerative syndromes, including infantile cerebellar retinal degeneration and recessive optic neuropathies (locus OPA9). By screening European cohorts of individuals with genetically unsolved inherited optic neuropathies, we identified 61 cases harbouring variants in ACO2, among whom 50 carried dominant mutations, emphasizing for the first time the important contribution of ACO2 monoallelic pathogenic variants to dominant optic atrophy. Analysis of the ophthalmological and clinical data revealed that recessive cases are affected more severely than dominant cases, while not significantly earlier. In addition, 27% of the recessive cases and 11% of the dominant cases manifested with extraocular features in addition to optic atrophy. In silico analyses of ACO2 variants predicted their deleterious impacts on ACO2 biophysical properties. Skin derived fibroblasts from patients harbouring dominant and recessive ACO2 mutations revealed a reduction of ACO2 abundance and enzymatic activity, and the impairment of the mitochondrial respiration using citrate and pyruvate as substrates, while the addition of other Krebs cycle intermediates restored a normal respiration, suggesting a possible short-cut adaptation of the tricarboxylic citric acid cycle. Analysis of the mitochondrial genome abundance disclosed a significant reduction of the mitochondrial DNA amount in all ACO2 fibroblasts. Overall, our data position ACO2 as the third most frequently mutated gene in autosomal inherited optic neuropathies, after OPA1 and WFS1, and emphasize the crucial involvement of the first steps of the Krebs cycle in the maintenance and survival of retinal ganglion cells