Multiple-scale neuroendocrine signals connect brain and pituitary hormone rhythms

International audienceSignificance The hypothalamo–pituitary axis controls a wide range of homeostatic processes, including growth, stress, and reproduction. Despite this fact, the hypothalamic neuron firing patterns that lead to slowly evolving pituitary hormone rhythms remain enigmatic. Here, we used in vivo amperometric recordings in freely behaving mice to investigate how tuberoinfundibular neurons release dopamine (DA) at the median eminence (ME) to control pituitary prolactin secretion. Using this approach, we show that DA release occurs as multiple locally generated and time-scaled secretory events, which are integrated over a range of minutes across the ME. These results provide a broad physiological mechanism for the dialogue that occurs between the brain and pituitary to dictate hormone rhythms over multiple timescales, from ultradian to seasonal

Influence of lactate and acetate removal on the microbiota of French fresh pork sausages

International audienceThe microbiota of fresh French pork sausages were characterised in five batches of comminuted pork meat that were equally divided into two formulations either containing the acid-based preservatives lactate and acetate, or no preservatives. Conventional microbiological analysis and high-throughput 16S rDNA amplicon sequencing methods were performed on meat batches packed under modified atmosphere (70% oxygen and 30% carbon dioxide) during chilled storage. In addition, meat pH and colour, and gas composition of the packages were monitored until the end of the shelf-life. During storage, the population of mesophilic and lactic acid bacteria increased from 4 log CFU/g to 8 log CFU/g after 15 days of chilled storage, both with and without preservatives. Despite similar changes of the physical and chemical parameters, such as pH and package gas composition, spoilage was delayed in the meat containing the preservatives, suggesting that lactate and acetate are effective against spoilage. Metagenetic analysis showed that at the end of the shelf-life, the species distribution differed between both the formulations and the batches. Lactic acid bacteria were shown to dominate both with and without preservatives; however, samples containing no preservatives were characterised by the presence of an increased population of Brochothrix spp. and Pseudomonas spp. whereas, Leuconostoc mesenteroides/pseudomesenteroides and Lactobacillus curvatus/graminis were more abundant in the meat with preservatives

40Ar/39Ar Temporal Framework for the Alleret Maar Lacustrine Sequence (French Massif-Central): Volcanological and Paleoclimatic Implications

International audienc

Modulation of the Tyrosine Kinase Receptor Ret/Glial Cell-Derived Neurotrophic Factor (GDNF) Signaling: A New Player in Reproduction Induced Anterior Pituitary Plasticity?

International audienc

La séquence lacustre du maar d’Alleret (Massif Central, France) : téphrochronologie et évolution paléoenvironnementale en Europe occidentale au début du Pléistocène moyen

Le maar d’Alleret (Massif Central, France) contient une séquence lacustre couvrant les stades isotopiques marins (SIM) 17 à 15. La partie étudiée, comprise entre 40,5 et 24,25 m de profondeur, enregistre la présence de téphras du Mont Dore (phase Sancy) qui permettent d’établir une téphrochronologie à partir de datations 40Ar/39Ar laser comprises entre 683 ± 5 et 718 ± 6 ka. Les analyses géochimiques et minéralogiques de ces téphras montrent une mésostase vitreuse à composition trachytique à rhyolitique. Des analyses sédimentologiques (granulométrie laser, susceptibilité magnétique, carbone et azote total) permettent de proposer une reconstitution des dynamiques morphosédimentaires et de comprendre la géodynamique externe dans le bassin versant pendant la phase lacustre. Une étude palynologique complète cette étude et apporte des informations sur la dynamique de la végétation autour du maar. Dans la partie inférieure de la séquence, le développement successif de forêts riparienne, caducifoliée, puis montagnarde est caractéristique d’un interglaciaire, attribué au SIM 17. Cet interglaciaire est suivi par une phase glaciaire corrélée au stade SIM 16. Le début de cette période glaciaire montre dans la séquence d’Alleret une grande variabilité cyclique, avec la présence de trois cycles stade/interstade. La comparaison avec les données paléoenvironnementales issues de forages glaciels, marins et continentaux montrent une bonne adéquation avec le cadre chronostratigraphique de cette partie de la séquence d’Alleret et confirme le remarquable intérêt des maars du Massif Central comme enregistreurs des variations climatiques et environnementales en milieu continental au cours du Quaternaire.The Alleret maar (Massif Central, France) is filled by a lacustrine sequence covering the marine isotopic stages (MIS) 17 to 15. In the studied part located between 24.25 and 40.5 m deep, the record of tephras from the Mont Dore (Sancy phase) allows us to establish a tephrochronology based on 40Ar/39Ar laser dating with ages between 683 ± 5 and 718 ± 6 ka. The geochemical and mineralogical analyses of these tephras show a trachytic to rhyolitic glass composition. Sedimentological analyses (laser grain-size, magnetic susceptibility, total carbon and nitrogen) allow us to propose a reconstruction of the morphosedimentary dynamics and to understand the external geodynamics in the watershed during the lacustrine phase. Palynological study achieves to reconstruct vegetation changes around the Alleret maar. In the lower part of the sequence, the succession of riparian, deciduous, and finally coniferous mountanous forests is representative of an interglacial period, which is attributed to the MIS 17. This interglacial is followed by the MIS 16 glacial period, which shows in the Alleret sequence a great cyclic variability with the presence of three stadial/interstadial cycles. Comparisons with ice, marine, and continental palaeoenvironmental and climatic records show a good agreement with the chronostratigraphical framework of this part of the Alleret sequence. Consequently, it confirms the great interest for the maars of the French Massif Central as markers of the environmental evolution and climate changes in continental domain during the Quaternary

Phylogenetic and Ecological Analysis of Novel Marine Stramenopiles

Culture-independent molecular analyses of open-sea microorganisms have revealed the existence and apparent abundance of novel eukaryotic lineages, opening new avenues for phylogenetic, evolutionary, and ecological research. Novel marine stramenopiles, identified by 18S ribosomal DNA sequences within the basal part of the stramenopile radiation but unrelated to any previously known group, constituted one of the most important novel lineages in these open-sea samples. Here we carry out a comparative analysis of novel stramenopiles, including new sequences from coastal genetic libraries presented here and sequences from recent reports from the open ocean and marine anoxic sites. Novel stramenopiles were found in all major habitats, generally accounting for a significant proportion of clones in genetic libraries. Phylogenetic analyses indicated the existence of 12 independent clusters. Some of these were restricted to anoxic or deep-sea environments, but the majority were typical components of coastal and open-sea waters. We specifically identified four clusters that were well represented in most marine surface waters (together they accounted for 74% of the novel stramenopile clones) and are the obvious targets for future research. Many sequences were retrieved from geographically distant regions, indicating that some organisms were cosmopolitan. Our study expands our knowledge on the phylogenetic diversity and distribution of novel marine stramenopiles and confirms that they are fundamental members of the marine eukaryotic picoplankton

Effects of dietary electrolyte balance and calcium supply on mineral and acid−base status of piglets fed a diversified diet

International audienceDietary electrolyte balance (dEB) is known to affect acid−base status and mineral metabolism, but is rarely considered in diet formulation for pigs. Yet, the use of a wide variety of local feedstuffs in Europe contributes to lowering the dEB and increasing the fibre content. Hence, mineral requirements may be modified and skeletal health affected. Therefore, the effects of a lower dEB and a higher dietary Ca level on acid−base balance and mineral status were assessed in young pigs fed a diversified diet. A total of twenty-four weaned pigs were fed a control moderate-dEB diet (C) or a diversified moderate-dEB (D), low-dEB (D-A) or low-dEB supplemented with Ca (D-CA) diet. Growth performance, venous blood gas and chemistry, urine pH, mineral balance and femur characteristics were determined. With an equivalent dEB compared with the C diet, the D diet caused an acidification of the urine and increased the excretion of P as a result of a higher dietary content of S. Low-grade metabolic acidosis occurred in piglets fed the D-A diet with changes at systemic and urine levels. A higher excretion of ammonia and P in urine was observed and some bone characteristics tended to be negatively affected. Ca supplementation partially counteracted the effects of low-grade acidosis. Urine excretion of P and ammonia was alleviated and bone characteristics improved. In conclusion, a higher Ca supply must be considered in more diversified diets to counteract the risk of evolving towards low-grade metabolic acidosis which can negatively affect bone

La séquence lacustre du maar d’Alleret (Massif Central, France) : téphrochronologie et évolution paléoenvironnementale en Europe occidentale au début du Pléistocène moyen

International audienceThe Alleret maar (Massif Central, France) is filled by a lacustrine sequence covering the marine isotopic stages (MIS) 17 to 15. In the studied part located between 24.25 and 40.5 m depth, the record of tephras from the Mont Dore (Sancy phase) allows us to establish a tephrochronology based on 40 Ar/ 39 Ar laser dating with ages between 683 ± 5 and 718 ± 6 ka. The geochemical and mineralogical analyses of these tephras show a trachytic to rhyolitic glass composition. Sedimentological analyses (laser grain-size, magnetic susceptibility, total carbon and nitrogen) allow us to propose a reconstruction of the morphosedimentary dynamics and to understand the external geodynamics in the watershed during the lacustrine phase. Palynological study achieves to reconstruct vegetation changes around the Alleret maar. In the lower part of the sequence, the succession of riparian, deciduous, and finally coniferous mountanous forests is representative of an interglacial period, which is attributed to the MIS 17. This interglacial is followed by the MIS 16 glacial period, which shows in the Alleret sequence a great cyclic variability with the presence of three stadial/interstadial cycles. Comparisons with ice, marine, and continental palaeoenvironmental and climatic records show a good agreement with the chronostratigraphical framework of this part of the Alleret sequence. Consequently, it confirms the great interest for the maars of the French Massif Central as markers of the environmental evolution and climate changes in continental domain during the Quaternary.Le maar d'Alleret (Massif central, France) contient une séquence lacustre couvrant les stades isotopiques marins (SIM) 17 à 15. La partie étudiée, comprise entre 40,5 et 24,25 m de profondeur, enregistre la présence de téphras du Mont Dore (phase Sancy) qui permettent d'établir une téphrochronologie à partir de datations 40 Ar/ 39 Ar laser comprises entre 683 ± 5 et 718 ± 6 ka. Les analyses géochimiques et minéralogiques de ces téphras montrent une mésostase vitreuse à composition trachytique à rhyolitique. Des analyses sédimentologiques (granulométrie laser, susceptibilité magnétique, carbone et azote total) permettent de proposer une reconstitution des dynamiques morphosédimentaires et de comprendre la géodynamique externe dans le bassin versant pendant la phase lacustre. Une étude palynologique complète cette étude et apporte des informations sur la dynamique de la végétation autour du maar. Dans la partie inférieure de la séquence, le développement successif de forêts riparienne, caducifoliée, puis montagnarde est caractéristique d'un interglaciaire, attribué au SIM 17. Cet interglaciaire est suivi par une phase glaciaire corrélée au stade SIM 16. Le début de cette période glaciaire montre dans la séquence d'Alleret une grande variabilité cyclique, avec la présence de trois cycles stade/interstade. La comparaison avec les données paléoenvironnementales issues de forages glaciels, marins et conti-nentaux montrent une bonne adéquation avec le cadre chronostratigraphique de cette partie de la séquence d'Alleret et confirme le remarquable intérêt des maars du Massif central comme enregistreurs des variations climatiques et environnementales en milieu continental au cours du Quaternaire

Assessment of lactotroph axis functionality in mice: longitudinal monitoring of PRL secretion by ultrasensitive-ELISA

The pattern of PRL secretion depend on the physiological state. Due to insufficient detection sensitivity of existing assays, the precise description of these patterns in mice is lacking. We described an ultrasensitive ELISA assay that can detect mouse PRL in small fractions of whole blood, allowing longitudinal studies of PRL secretion profiles in freely moving mice. Over a 24h period, males displayed no oscillation in PRL levels while virgin and lactating females showed large pulses. Peaks of PRL secretion reached 30–40ng/mL in lactating female mice, and rarely exceeded 10ng/mL in virgin females. These pulses of PRL in lactating females were associated to suckling. The return of pups after an experimental 12h weaning induced a pulse of PRL release, reaching 100ng/mL. This approach also enabled us to assess the inhibitory tone from hypothalamic dopamine neurons on PRL secretion. We used a dopamine D2 receptor antagonist to relieve pituitary lactotrophs from the tuberoinfundibular dopaminergic (TIDA) inhibitory tone, and demonstrate a D2-induced PRL rise that can be used to evaluate both the secretory capacity of lactotrophs and the magnitude of the inhibitory tone on pituitary PRL release. We demonstrate that whilst lactotroph function is altered to enhance chronic PRL output, their secretory response to acute stimulus is not modified during lactation, and that chronic hyperprolactinemia is linked to a lower inhibitory tone. The combination of a sensitive PRL ELISA and administration of D2 receptor antagonist provide a unique opportunity to investigate the function and plasticity of the lactotroph axis in freely moving mice