Neural correlate of memory enhancement during physical exercise

It has been shown that physical exercise is beneficial for cognition, however, the neuronal mechanism underpinning this process is not yet clear. Therefore, we investigated the correlation of brain activity during physical exercise with memory performance. Eighteen participants were asked to memorise a set of stimuli. Subsequently they either cycled on an exercise bike for 30 minutes while their EEG was recorded, or sat on the exercise bike and watched a documentary for 30 minutes. After a 1.5 hour retention interval, they were asked to perform an old/new recognition task. In addition to improvement in memory performance (exercise 71.11% vs. rest 66.67%, p=0.02), the theta band activity of the DLPFC was correlated with the enhanced performance (r=-0.48, p=0.04)

Influence of carbonation on the low-temperature consolidation by Spark Plasma Sintering of carbonated calcium phosphate bioceramics

Calcium phosphates (CaP) such as biomimetic nanocrystalline apatite or amorphous calcium phosphate are hydrated bioactive compounds particularly suitable for bone repair applications due to their similarity with bone mineral. However, their consolidation in ceramic parts deserves special attention as they are thermodynamically metastable and can decompose into less bioactive phases upon heating. Adapted strategies are needed to obtain bulk bioceramics. Spark Plasma Sintering (SPS) has been shown to allow cold sintering of such compounds at temperatures like 150 °C while preserving the hydrated character and nanosized dimensions of the precursor powders. To this date, however, the role of the degree of carbonation of these precursors on the densification of CO3-bearing CaP compounds via SPS has not been explored despite the natural carbonation of bone. In this work, several carbonated CaP hydrated compounds were prepared and consolidated by SPS and the characteristics of the obtained ceramics was scrutinized with respect to the starting powders. Two carbonation routes were carried out: via volume carbonation during powder synthesis or via subsequent surface ion exchange. All samples tested led to apatitic compounds after SPS, including amorphous CaP. We show that the degree of carbonation negatively affects the densification rate and propose possible hypotheses explaining this behavior. Evolution in the nature of the carbonate sites (apatitic A-, B-types and labile surface carbonates) before and after SPS is also noticed and commented. The consolidation of such compounds is however proven possible, and gives rise to bone-like apatitic compounds with great potential as bioactive resorbable ceramics for bone regeneration

Consolidation of bone-like apatite bioceramics by spark plasma sintering of amorphous carbonated calcium phosphate at very low temperature

Various carbonated calcium phosphate powders were synthesized by aqueous precipitation and ceramics consolidation by spark plasma sintering (SPS) at very low temperature was investigated. The objective was to preserve low crystallinity and avoid material decarbonation. SPS at low temperature only leads to little or no sintering when crystallized powders are used. Amorphous powders are required. In this case, consolidation occurs at temperatures below 150°C. It is accompanied by crystallization of the amorphous phase into calcium-deficient carbonated apatite Ca10-x-y(PO4)6-x-y(HPO4)x(CO3)y(OH)2-x-y-2z(CO3)z. The resulting ceramics are microporous and highly cohesive with good mechanical properties (flexural strength=18MPa). The sintering mechanism, called “crystal fusion”, is based on solid state diffusion of chemical species at the grain boundary and crystal growth within the amorphous particles. These bioceramics that mimic the composition of the bone mineral are expected to have a higher bioreactivity than well crystallized carbonated hydroxyapatite ceramics obtained by conventional sintering

The effects of different protocols of physical exercise and rest on long-term memory

Whilst there are many studies comparing the different effects of exercise on long-term memory, these typically adopt varying intensities, durations, and behavioural measures. Furthermore, few studies provide direct comparisons between exercise and different types of rest. Therefore, by providing a standardised methodological design, this study will ascertain the most effective intensity and protocol of exercise for the modulation of long-term memory, whilst directly comparing it to different types rest. This was achieved using the same old/new recognition memory test and an 80-90 min retention interval. Three experiments were performed (total N=59), each with a three-armed crossover design measuring the extent to which physical exercise and wakeful rest can influence long-term memory performance. In Experiment 1, the effects of continuous moderate intensity exercise (65-75% HRmax), passive rest (no cognitive engagement) and active rest (cognitively engaged) were explored. In Experiment 2, continuous moderate intensity exercise was compared to a type of high-intensity interval training (HIIT) and passive rest. Experiment 3 observed the effects of low- (55-65% HRmax), moderate- and high-intensity (75-85% HRmax) continuous exercise. Across the three experiments moderate intensity exercise had the greatest positive impact on memory performance. Although not significant, HIIT was more effective than passive-rest, and passive rest was more effective than active rest. Our findings suggest that it is not necessary to physically overexert oneself in order to achieve observable improvements to long-term memory. By also investigating wakeful rest, we reaffirmed the importance of the cognitive engagement during consolidation for the formation of long-term memories

Substrate specificity and regioselectivity of fungal AA9 lytic polysaccharide monooxygenases secreted by Podospora anserina

International audienceBackground: The understanding of enzymatic polysaccharide degradation has progressed intensely in the past few years with the identification of a new class of fungal-secreted enzymes, the lytic polysaccharide monooxygenases (LPMOs) that enhance cellulose conversion. In the fungal kingdom, saprotrophic fungi display a high number of genes encoding LPMOs from family AA9 but the functional relevance of this redundancy is not fully understood. Results: In this study, we investigated a set of AA9 LPMOs identified in the secretomes of the coprophilous ascomycete Podospora anserina, a biomass degrader of recalcitrant substrates. Their activity was assayed on cellulose in synergy with the cellobiose dehydrogenase from the same organism. We showed that the total release of oxidized oligosaccharides from cellulose was higher for PaLPMO9A, PaLPMO9E, and PaLPMO9H that harbored a carbohydrate-binding module from the family CBM1. Investigation of their regioselective mode of action revealed that PaLPMO9A and PaLPMO9H oxidatively cleaved at both C1 and C4 positions while PaLPMO9E released only C1-oxidized products. Rapid cleavage of cellulose was observed using PaLPMO9H that was the most versatile in terms of substrate specificity as it also displayed activity on cello-oligosaccharides and beta-(1,4)-linked hemicellulose polysaccharides (e.g., xyloglucan, glucomannan). Conclusions: This study provides insights into the mode of cleavage and substrate specificities of fungal AA9 LPMOs that will facilitate their application for the development of future biorefineries

Determinants of participation in colonoscopic screening by siblings of colorectal cancer patients in France

International audienceBACKGROUND: Targeted colonosocopic screening is recommended for first-degree relatives of colorectal cancer patients diagnosed before the age of 60 and offers the possibility of reducing morbidity and mortality, but participation remains too low. The objective of this study was to determine in a French population the factors that affect siblings' participation in screening, notably those relating to the individuals, their medical care, their family and their social network. METHODS: A cross sectional survey was conducted in siblings of index patients having undergone surgery for colorectal cancer between 1999 and 2002 in two French counties. Siblings were contacted during 2007 and 2008 through the index patient. The factors affecting participation in colonoscopic screening were studied by logistic regression taking into account family cluster effect. RESULTS: 172 siblings of 74 index cases were included. The declared rate of undergoing at least one colonoscopy among siblings was 66%; 95%CI 59-73%. Five variables were independently associated with colonoscopic screening: perceiving fewer barriers to screening (OR = 3.2; 95%CI 1.2-8.5), having received the recommendation to undergo screening from a physician (OR = 4.9; 1.7-13.7), perceiving centres practising colonoscopy as more accessible (OR = 3.2, 1.3-7.8), having discussed screening with all siblings (OR = 3.9; 1.6-9.6) and being a member of an association (OR = 2.6; 1.0-6.6). CONCLUSIONS: The factors independently associated with participation in CRC screening by an individual at increased risk belonged to each of four dimensions relating to his individual psychosocial characteristics, to his relationship with a physician, within the family and social environment. The relevance of these results to clinical practice may help to improve compliance to recommendations in a global preventive strategy including all stages of the information pathway from the physician to the index patient and his relatives

Increasing frailty is associated with higher prevalence and reduced recognition of delirium in older hospitalised inpatients: results of a multi-centre study

Purpose: Delirium is a neuropsychiatric disorder delineated by an acute change in cognition, attention, and consciousness. It is common, particularly in older adults, but poorly recognised. Frailty is the accumulation of deficits conferring an increased risk of adverse outcomes. We set out to determine how severity of frailty, as measured using the CFS, affected delirium rates, and recognition in hospitalised older people in the United Kingdom. Methods: Adults over 65 years were included in an observational multi-centre audit across UK hospitals, two prospective rounds, and one retrospective note review. Clinical Frailty Scale (CFS), delirium status, and 30-day outcomes were recorded. Results: The overall prevalence of delirium was 16.3% (483). Patients with delirium were more frail than patients without delirium (median CFS 6 vs 4). The risk of delirium was greater with increasing frailty [OR 2.9 (1.8–4.6) in CFS 4 vs 1–3; OR 12.4 (6.2–24.5) in CFS 8 vs 1–3]. Higher CFS was associated with reduced recognition of delirium (OR of 0.7 (0.3–1.9) in CFS 4 compared to 0.2 (0.1–0.7) in CFS 8). These risks were both independent of age and dementia. Conclusion: We have demonstrated an incremental increase in risk of delirium with increasing frailty. This has important clinical implications, suggesting that frailty may provide a more nuanced measure of vulnerability to delirium and poor outcomes. However, the most frail patients are least likely to have their delirium diagnosed and there is a significant lack of research into the underlying pathophysiology of both of these common geriatric syndromes

Simple modelling of radar backscattering coefficient over a bare soil : variation with incidence angle, frequency and polarization

International audienc

Test d'un modèle simple de rétrodiffusion radar du sol nu avec un modèle simplifié et un modèle analytique

International audienc

De l'arbre à la forêt : singularité et généralisation dans les modèles physiques

Dans tout problème de science et en particulier ceux qui impliquent une modélisation de phénomènes physiques à l'aide d'un ensemble d'équations mathématiques, la question de passer du singulier au général est centrale. L'exemple développé ici est celui de la modélisation du signal électromagnétique d'une forêt afin d'exploiter des images satellitaires pour diverses applications. Pour interpréter le signal reçu, le physicien utilise donc un modèle mathématique qui résume le savoir en cours sur la formation du signal en fonction des caractéristiques de la forêt. La discipline produit énormément de travaux de modélisation qui utilisent des données sur les arbres et les descriptions de l'arbre sont souvent traitées comme secondaires par rapport à la construction de l'appareil mathématique. Or, la description de l'arbre qui va produire le fichier d'entrée du modèle est fondamentale pour le calcul du résultat. Il semble que cette description est traitée comme une non-question de recherche peut-être parce que c'est un objet naturel et non une création de la technologie, ou parce qu'il s'agit d'un objet mesurable par des moyens simples, qu'il est immédiatement accessible (contrairement à la description de l'ADN par exemple). Bref, un arbre : ça crève les yeux... Or, nous montrons ici que l'arbre du physicien est une création totalement nouvelle et originale et que c'est le résultat d’un travail complexe d'élaboration au même titre que l'établissement des équations qui composent le modèle mathématique