Inter-Brain Synchronization during Social Interaction

During social interaction, both participants are continuously active, each modifying their own actions in response to the continuously changing actions of the partner. This continuous mutual adaptation results in interactional synchrony to which both members contribute. Freely exchanging the role of imitator and model is a well-framed example of interactional synchrony resulting from a mutual behavioral negotiation. How the participants'' brain activity underlies this process is currently a question that hyperscanning recordings allow us to explore. In particular, it remains largely unknown to what extent oscillatory synchronization could emerge between two brains during social interaction. To explore this issue, 18 participants paired as 9 dyads were recorded with dual-video and dual-EEG setups while they were engaged in spontaneous imitation of hand movements. We measured interactional synchrony and the turn-taking between model and imitator. We discovered by the use of nonlinear techniques that states of interactional synchrony correlate with the emergence of an interbrain synchronizing network in the alpha-mu band between the right centroparietal regions. These regions have been suggested to play a pivotal role in social interaction. Here, they acted symmetrically as key functional hubs in the interindividual brainweb. Additionally, neural synchronization became asymmetrical in the higher frequency bands possibly reflecting a top-down modulation of the roles of model and imitator in the ongoing interaction.     

The C-biogeochemistry of a Midwestern USA agricultural impoundment in context: Lake Decatur in the intensively managed landscape critical zone observatory

The damming of rivers has created hotspots for organic carbon sequestration and methane production on a global scale as the reservoirs intercept fluvial suspended and dissolved loads. To better understand how the C-biogeochemistry of a reservoir responds to watershed processes and evolves over time, Lake Decatur, located in the Intensively Managed Landscape Critical Zone Observatory (IML-CZO) was studied. Solid phase analyses (% organic C, C/N, δ¹³C, δ¹⁵N) of soils and sediments sampled from stream bank exposures, river suspensions, and the lake bottom were conducted to characterize organic C (OC) sources throughout the sedimentary system. Agriculturally-driven soil erosion rapidly altered lake bathymetry causing an evolution of sedimentary and OC deposition patterns, which in turn shaped where and when methane production occurred. A positive correlation between OC accumulation rate and porewater dissolved inorganic C (DIC) δ¹³C profiles indicates that methane generation is strongly influenced by OC burial rate. The sources of the lake bed particulate organic C (POC) have also evolved over time. Drowned vegetation and/or shoreline inputs were dominant initially in areas adjacent to the original river channel but were rapidly overwhelmed by the deposition of sediments derived from eroded agricultural soils. Eutrophication of the lake followed with the onset of heavy fertilizer application post-1960. This succession of sources is expected to be commonplace for reservoirs greater than?~?50–60 years old in agricultural settings because of the relative timing of tillage and fertilizer practices. The ¹³C/¹²C ratios of methane from Lake Decatur were more depleted in ¹³C than what is commonly expected for freshwater sedimentary environments. The ¹³C-depletion suggests that CO₂-reduction is the dominant methanogenic pathway rather than the anticipated acetate dissimilation process. The isotopic observations reveal that commonly held assumptions about methane production and its C-isotopic signature in freshwater systems are over-simplified and not strictly applicable to this system.     

Muscle-derived expression of the chemokine CXCL1 attenuates diet-induced obesity and improves fatty acid oxidation in the muscle

Serum levels and muscle expression of the chemokine CXCL1 increase markedly in response to exercise in mice. Because several studies have established muscle-derived factors as important contributors of metabolic effects of exercise, this study aimed at investigating the effect of increased expression of muscle-derived CXCL1 on systemic and intramuscular metabolic parameters, with focus on fatty acid oxidation and oxidative metabolism in skeletal muscle. By overexpression of CXCL1 in the tibialis cranialis muscle in mice, significant elevations in muscle and serum CXCL1 within a physiological range were obtained. At 3 mo of high-fat feeding, visceral and subcutaneous fat mass were 32.4 (P < 0.01) and 22.4% (P < 0.05) lower, respectively, in CXCL1-overexpressing mice compared with control mice. Also, chow-fed CXCL-transfected mice had 35.4% (P < 0.05) lower visceral fat mass and 33.4% (P < 0.05) lower subcutaneous fat mass compared with chow-fed control mice. These reductions in accumulation of adipose tissue were accompanied by improved glucose tolerance and insulin sensitivity. Furthermore, in CXCL1-transfected muscles, muscular ex vivo fatty acid oxidation was significantly enhanced compared with control muscles (chow fed: 2.2-fold, P < 0.05; high-fat fed: 2-fold, P < 0.05) and also showed increased expression levels of major fatty acid oxidation genes (CD36, CPT I, and HADH). Finally, CXCL1 expression was associated with increased muscle mRNA expression of VEGF and CD31, suggesting a role for CXCL1 in muscle angiogenesis. In conclusion, our data show that overexpression of CXCL1 within a physiological range attenuates diet-induced obesity, likely mediated through a CXCL1-induced improvement of fatty acid oxidation and oxidative capacity in skeletal muscle tissue.     

Source-sink imbalance increases with growth temperature in the spring geophyte Erythronium americanum

Spring geophytes produce larger storage organs and present delayed leaf senescence under lower growth temperature. Bulb and leaf carbon metabolism were investigated in Erythronium americanum to identify some of the mechanisms that permit this improved growth at low temperature. Plants were grown under three day/night temperature regimes: 18/14 °C, 12/8 °C, and 8/6 °C. Starch accumulated more slowly in the bulb at lower temperatures probably due to the combination of lower net photosynthetic rate and activation of a 'futile cycle' of sucrose synthesis and degradation. Furthermore, bulb cell maturation was delayed at lower temperatures, potentially due to the delayed activation of sucrose synthase leading to a greater sink capacity. Faster starch accumulation and the smaller sink capacity that developed at higher temperatures led to early starch saturation of the bulb. Thereafter, soluble sugars started to accumulate in both leaf and bulb, most probably inducing decreases in fructose-1,6-bisphosphatase activity, triose-phosphate utilization in the leaf, and the induction of leaf senescence. Longer leaf life span and larger bulbs at lower temperature appear to be due to an improved equilibrium between carbon fixation capacity and sink strength, thereby allowing the plant to sustain growth for a longer period of time before feedback inhibition induces leaf senescence.     

Molecular evidence for the coexistence of two sibling species in Pylaiella littoralis (Ectocarpales,Phaeophyceae) along the Brittany coast

The great phenotypic variability and the lack of diagnostic characters in the genus Pylaiella render the systematic study of this genus problematic. In this study, we investigated the diversity of Pylaiella littoralis along the Brittany (France) coast using a DNA barcoding multilocus approach with mitochondrial (cox1, nad1, and atp9) and chloroplastic (rbcL and atpB) markers associated with a population genetics approach using 10 microsatellite markers. In addition, spatio‐temporal sampling was conducted along the Brittany coast. We sampled 140 individuals from four sites located between Saint‐Malo and Concarneau (380 km) from April to October. Mitochondrial sequence data revealed the occurrence of two sibling species, with a minimum of 2.4% divergence between them. Microsatellite genotypic data congruently revealed two well‐supported clusters matching the two mitochondrial clades of Pylaiella. Although gene flow is limited between species, occurrence of genetic admixtures in some populations suggested that reproductive isolation is not complete. Our study highlighted the complementarity of barcoding and population genetics approaches to shed light on the evolutionary processes that lead to speciation.     

Temporal variations and spatial patterns in saline and waterlogged peat fields: 1. Survival and growth of salt marsh graminoids

A cutover bog contaminated with seawater in New Brunswick, Canada remained barren 5 years after peat extraction operations ceased despite the proximity of natural seed sources. The aim of the study was to identify abiotic stresses impeding plant establishment and test transplanting of salt-tolerant wetland plants. The site consisted of long cambered rectangular fields that sloped down (2%) to the drainage ditches on both sides. Across this slope, zones were delineated based on moisture gradient as: Up-areas (drier), Mid-areas (moist) and Low-areas (wet). Juncus balticus was transplanted to these zones in August 2004 whereas Spartina pectinata was reintroduced in June 2005. Plant material was collected from nearby marshes. Survival of J. balticus in August 2005 was poorest at the Low-areas probably because of the early season flooded conditions of that zone. S. pectinata survival in June 2006 was good in all zones having better adaptation to early season waterlogged conditions. Early season waterlogged conditions resulted from a perched water table (May–June) and were alleviated only upon the complete thaw of the frozen peat layer on 8 July. Thereafter, important changes in peat characteristics occurred: lowered water table depths that increased redox potentials, decreased moisture content (θ) that increased dry bulk density (ρ), and increased electrical conductivity (EC) that decreased pH. Waterlogged conditions were of greater magnitude and duration at the Low-areas but salinity levels were highest in the Up-areas and Mid-areas. We conclude that local conditions of waterlogging (especially in the Low-areas) and high salinity and low pH (notably in the Up- and Mid-areas) favoured the survival of S. pectinata in all areas and J. balticus in Up- and Mid-areas only.     

Isolating samples in the chamber of a steam-formaldehyde sterilizer

The construction and use of an electrically operated closure device, together with a control system, for securing samples from a non-inflammable atmosphere is described. An outline of the device for use with a low temperature steam-formaldehyde (LTSF) sterilizer is given.     

Purification of the neurite outgrowth promoting fragment of mouse laminin.

A method for isolation of the neurite outgrowth promoting fragment of mouse laminin (fragment 8) is described in this paper. Besides producing excellent yields, this method was shown to be fast and practical, since it is based on a single step which consists in an ion exchange chromatography of elastase digested laminin.     

Identification of nitrogen-fixing enterobacteria from living Sassafras (Atherosperma moschatum Labill.) trees

Nitrogen-fixing enterobacteria (Enterobacter agglomerans and Citrobacter freundii) were commonly found associated with the microflora of stained Sassafras (Atherosperma moschatum Labill.) in forests of SE Tasmania. However, their populations never exceeded 3× 10⁴ cells g⁻¹ dry wood and comprised at most 3% of the total bacterial flora. Bacterial colonization of the wood appeared to coincide with that by non-hymenocetous fungi: bacteria were never isolated in significant numbers from wood not infected with fungi. The contribution of the N₂-fixing flora to the N economy of the habitat is considered to be negligible.     

Effects of <Emphasis Type="Italic">crp</Emphasis> deletion in <Emphasis Type="Italic">Salmonella enterica</Emphasis> serotype Gallinarum

Background  

Salmonella enterica serotype Gallinarum (S. Gallinarum) remains an important pathogen of poultry, especially in developing countries. There is a need to develop effective and safe vaccines. In the current study, the effect of crp deletion was investigated with respect to virulence and biochemical properties and the possible use of a deletion mutant as vaccine candidate was preliminarily tested.