Between-group competition elicits within-group cooperation in children

Aggressive interactions between groups are frequent in human societies and can bear significant fitness costs and benefits (e.g. death or access to resources). During between-group competitive interactions, more cohesive groups (i.e. groups formed by individuals who cooperate in group defence) should out-perform less cohesive groups, other factors being equal (e.g. group size). The cost/benefit of between-group competition are thought to have driven correlated evolution of traits that favour between-group aggression and within-group cooperation (e.g. parochial altruism). Our aim was to analyse whether the proximate relationship between between-group competition and within-group cooperation is found in 3–10 years old children and the developmental trajectory of such a relationship. We used a large cohort of children (n = 120) and tested whether simulated between-group competition increased within-group cooperation (i.e. how much of a resource children were giving to their group companions) in two experiments. We found greater within-group cooperation when groups of four children were competing with other groups then in the control condition (no between-group competition). Within-group cooperation increased with age. Our study suggests that parochial altruism and in-group/out-group biases emerge early during the course of human development

Anthropogenic perturbations of the silicon cycle at the global scale: Key role of the land-ocean transition

International audienceSilicon (Si), in the form of dissolved silicate (DSi), is a key nutrient in marine and continental ecosystems. DSi is taken up by organisms to produce structural elements (e.g., shells and phytoliths) composed of amorphous biogenic silica (bSiO(2)). A global mass balance model of the biologically active part of the modern Si cycle is derived on the basis of a systematic review of existing data regarding terrestrial and oceanic production fluxes, reservoir sizes, and residence times for DSi and bSiO(2). The model demonstrates the high sensitivity of biogeochemical Si cycling in the coastal zone to anthropogenic pressures, such as river damming and global temperature rise. As a result, further significant changes in the production and recycling of bSiO(2) in the coastal zone are to be expected over the course of this century

Influence of grafting density and distribution on material properties using well-defined alkyl functional poly(styrene-co-maleic anhydride) architectures synthesized by RAFT

Poly(styrene-co-maleic anhydride) copolymers (PSMA) with controlled number and distribution of maleic anhydride (MAnh) units were synthesized by reversible addition–fragmentation chain transfer polymerization using chain-transfer agents (CTA) suitable for industrial scale processes. Linear- and star-shaped alternating PSMA polymers were prepared in a single-step synthesis, while a one-pot sequential chain-extension strategy was utilized to prepare diblock, multiblock, and multisite copolymer architectures. A library of grafted PSMAs with controlled density and distribution of side chains was achieved by the subsequent grafting of long aliphatic alcohol chains (C22) to the MAnh units. The influence of structure, composition, and long alkyl chain addition on PSMAs behavior in solution was studied with triple-detection size exclusion chromatography, while their thermal properties were examined by thermogravimetric analysis and differential scanning calorimetry. Overall, the side chain density and distribution did not impact the polymer conformations in solution (random coil); however, an effect on the molecular size (Rh) and structure density (intrinsic viscosity) were observed. The materials density was shown to be dependent on polymer architectures as lower intrinsic viscosity was observed for the star copolymer. All the materials had similar degradation points (400 °C), while the rate of degradation showed a dependence on the MAnh content and polymeric architecture. Ultimately, the grafting of long aliphatic side chains (crystalline) onto the PSMA backbone, even at low density, was shown to drastically change the microphase ordering, as all the grafted copolymers became semicrystalline. The difference of the crystallization temperature between low density multisite materials (Tc ≈ 8 °C) and the high density alternating material (Tc ≈ 40 °C) highlights the major importance of controlling copolymer composition and structure to tune material properties

Tuning the structure, stability and responsivity of polymeric arsenical nanoparticles using polythiol cross-linkers

The use of organic arsenicals in polymer chemistry and biomaterials science is limited despite the distinctive and versatile chemistry of arsenic. The interchangeable oxidation states of arsenic and the subsequent changes in chemical properties make it a promising candidate for redox-responsive materials. Thus, reversible addition–fragmentation chain transfer (RAFT) polymerization has been employed for the first time to synthesize thermoresponsive organic arsenical containing block copolymers. The polymers undergo simultaneous self-assembly and cross-linking, via the organic arsenical pendant groups, under reductive conditions (to reduce As(V) to As(III)) in the presence of polythiol reagents as cross-linkers. The formation of As–S bonds stabilizes the nanoparticles formed (Dh = 19–29 nm) and enables the stability and responsivity to oxidative stress of the particles, in aqueous and model biological solutions, to be tuned as a function of the number of thiols in the cross-linker or the [SH]/[As] stoichiometric ratio. The parent block copolymers and nanoparticles are nontoxic in vitro, and the tunable responsivity of these nanoparticles and the (bio)chemical activity of organic arsenical reagents could be advantageous for targeted drug delivery and the other bio(nano)medical applications. To the best our knowledge, this is the first time that arsenic–thiolate (As–S) bonding has been employed for stimuli-responsive cross-linking of polymeric nanoparticles

Imatinib Mesylate Exerts Anti-Proliferative Effects on Osteosarcoma Cells and Inhibits the Tumour Growth in Immunocompetent Murine Models

Osteosarcoma is the most common primary malignant bone tumour characterized by osteoid production and/or osteolytic lesions of bone. A lack of response to chemotherapeutic treatments shows the importance of exploring new therapeutic methods. Imatinib mesylate (Gleevec, Novartis Pharma), a tyrosine kinase inhibitor, was originally developed for the treatment of chronic myeloid leukemia. Several studies revealed that imatinib mesylate inhibits osteoclast differentiation through the M-CSFR pathway and activates osteoblast differentiation through PDGFR pathway, two key cells involved in the vicious cycle controlling the tumour development. The present study investigated the in vitro effects of imatinib mesylate on the proliferation, apoptosis, cell cycle, and migration ability of five osteosarcoma cell lines (human: MG-63, HOS; rat: OSRGA; mice: MOS-J, POS-1). Imatinib mesylate was also assessed as a curative and preventive treatment in two syngenic osteosarcoma models: MOS-J (mixed osteoblastic/osteolytic osteosarcoma) and POS-1 (undifferentiated osteosarcoma). Imatinib mesylate exhibited a dose-dependent anti-proliferative effect in all cell lines studied. The drug induced a G0/G1 cell cycle arrest in most cell lines, except for POS-1 and HOS cells that were blocked in the S phase. In addition, imatinib mesylate induced cell death and strongly inhibited osteosarcoma cell migration. In the MOS-J osteosarcoma model, oral administration of imatinib mesylate significantly inhibited the tumour development in both preventive and curative approaches. A phospho-receptor tyrosine kinase array kit revealed that PDGFRα, among 7 other receptors (PDFGFRβ, Axl, RYK, EGFR, EphA2 and 10, IGF1R), appears as one of the main molecular targets for imatinib mesylate. In the light of the present study and the literature, it would be particularly interesting to revisit therapeutic evaluation of imatinib mesylate in osteosarcoma according to the tyrosine-kinase receptor status of patients

Role of small Rhizaria and diatoms in the pelagic silica production of the Sourther Ocean

We examined biogenic silica production and elementary composition (biogenic Si, particulate organic carbon and particulate organic nitrogen) of Rhizaria and diatoms in the upper 200 m along a transect in the Southwest Pacific sector of the Southern Ocean during austral summer (January–February 2019). From incubations using the 32Si radioisotope, silicic acid uptake rates were measured at 15 stations distributed in the Polar Front Zone, the Southern Antarctic Circumpolar Current and the Ross Sea Gyre. Rhizaria cells are heavily silicified (up to 7.6 nmol Si cell−1), displaying higher biogenic Si content than similar size specimens found in other areas of the global ocean, suggesting a higher degree of silicification of these organisms in the silicic acid rich Southern Ocean. Despite their high biogenic Si and carbon content, the Si/C molar ratio (average of 0.05 ± 0.03) is quite low compared to that of diatoms and relatively constant regardless of the environmental conditions. The direct measurements of Rhizaria's biogenic Si production (0.8–36.8 μmol Si m−2 d−1) are of the same order of magnitude than previous indirect estimations, confirming the importance of the Southern Ocean for the global Rhizaria silica production. However, diatoms largely dominated the biogenic Si standing stock and production of the euphotic layer, with low rhizarians' abundances and biogenic Si production (no more than 1%). In this manuscript, we discuss the Antarctic paradox of Rhizaria, that is, the potential high accumulation rates of biogenic Si due to Rhizaria in siliceous sediments despite their low production rates in surface waters.Versión del editor3,38

Aberrant survival of hippocampal Cajal-Retzius cells leads to memory deficits, gamma rhythmopathies and susceptibility to seizures in adult mice

Cajal-Retzius cells (CRs) are transient neurons, disappearing almost completely in the postnatal neocortex by programmed cell death (PCD), with a percentage surviving up to adulthood in the hippocampus. Here, we evaluate CR’s role in the establishment of adult neuronal and cognitive function using a mouse model preventing Bax-dependent PCD. CRs abnormal survival resulted in impairment of hippocampus-dependent memory, associated in vivo with attenuated theta oscillations and enhanced gamma activity in the dorsal CA1. At the cellular level, we observed transient changes in the number of NPY cells and altered CA1 pyramidal cell spine density. At the synaptic level, these changes translated into enhanced inhibitory currents in hippocampal pyramidal cells. Finally, adult mutants displayed an increased susceptibility to lethal tonic-clonic seizures in a kainate model of epilepsy. Our data reveal that aberrant survival of a small proportion of postnatal hippocampal CRs results in cognitive deficits and epilepsy-prone phenotypes in adulthood.We thank Dr. P. Billuart for critical reading of the manuscript and suggestions during the course of the study, the NeuroImag platform at the IPNP and SFR Necker Imaging and histology platforms at the Imagine Institute for help with acquisition, the animal house facility (LEAT) and Animalliance for animal care. We are grateful to N. Ramezanidoraki and P. Billuart for initiating the first MEA experiment as well as members of the Pierani’s lab for technical support and helpful discussions.We thank Ann Kennedy for mouse profile (Zenodo, 2020) doi:10.5281/zenodo.3925921and for the mouse scheme in Fig. 3a, French Ministry of Research (BioSPc Doctoral school) (M.R.), Fondation pour la recherche médicale, FDT20201201037 (M.R.), Centre national de la recherche scientifique (CNRS) (A.P.), Agence Nationale de la Recherche, ANR-15-CE16-0003-01, ANR-19-CE16-0017-03 and ANR20-CE16-0001-01 (A.P.), Fondation pour la recherche médicale, Équipe FRM DEQ20130326521 and EQU201903007836) (A.P.), Agence Nationale de la Recherche under “Investissements d’avenir” program, ANR10-IAHU-01) (Imagine Institute), Fondation pour la recherche médicale (F.O.), AGEMED-INSERM (F.O.), NRJ for Neuroscience (F.O.), European Research Council (Consolidator grant #683154) (N. Rouach), European Research Council (Starting Grant #678250) (N. Rebola), Agence Nationale de la Recherche ANR-21-CE16-0020 and ANR-20-CE16-0009 (N. Rebola), and ANR-21-NEU2-0007-01 Eranet-Neuron ROSSINI project (A.P. and L.M.d.l.P.)

Short-Term Enrichment Makes Male Rats More Attractive, More Defensive and Alters Hypothalamic Neurons

Innate behaviors are shaped by contingencies built during evolutionary history. On the other hand, environmental stimuli play a significant role in shaping behavior. In particular, a short period of environmental enrichment can enhance cognitive behavior, modify effects of stress on learned behaviors and induce brain plasticity. It is unclear if modulation by environment can extend to innate behaviors which are preserved by intense selection pressure. In the present report we investigate this issue by studying effects of relatively short (14-days) environmental enrichment on two prominent innate behaviors in rats, avoidance of predator odors and ability of males to attract mates. We show that enrichment has strong effects on both the innate behaviors: a) enriched males were more avoidant of a predator odor than non-enriched controls, and had a greater rise in corticosterone levels in response to the odor; and b) had higher testosterone levels and were more attractive to females. Additionally, we demonstrate decrease in dendritic length of neurons of ventrolateral nucleus of hypothalamus, important for reproductive mate-choice and increase in the same in dorsomedial nucleus, important for defensive behavior. Thus, behavioral and hormonal observations provide evidence that a short period of environmental manipulation can alter innate behaviors, providing a good example of gene-environment interaction