Introduced freshwater blenny influences the diet and body condition of the invasive dice snake in Lake Geneva

Non-indigenous species can have strong impacts on biodiversity by affecting trophic relationships in their new environments. The piscivorous dice snake (Natrix tessellata) has been introduced to Geneva Lake, western Switzerland, where the endangered viperine snake (Natrix maura) is native. Local, dramatic declines in the viperine snake population might be associated with the appearance of the dice snake through dietary overlap between these 2 species, which mainly feed on bullhead (Cottus gobio). In response to this decline, a control program for dice snake was implemented in 2007 to reduce numbers of this introduced snake. In 2010, a new species of fish, the freshwater blenny (Salaria fluviatilis), which shares the same habitat as the bullhead, was introduced into Lake Geneva and has since reached high densities. We determined the impact of freshwater blenny on diet composition and body condition of dice snakes. In addition, we tested for effects of the control program on the body condition of dice snakes and viperine snakes. We collected 294 dice snakes between 2007 and 2013. Based on morphology and a genetic marker (cytochrome b gene), we determined the ®sh species contained in these snakes' stomachs. We found a drastic switch in dice snake diet following the arrival of freshwater blenny, as consumption of bullhead declined by 68% and was replaced by the blenny. In addition, the body condition of dice snakes increased significantly after the arrival of freshwater blenny. The body condition of both snake species was positively correlated with the number of dice snakes removed from the study area. This finding has important implications concerning the conservation of the endangered viperine snake, and suggests that the control program of dice snakes should be continued.

Validity of impedance-based equations for the prediction of total body water as measured by deuterium dilution in African women.

BACKGROUND: Little information is available on the validity of simple and indirect body-composition methods in non-Western populations. Equations for predicting body composition are population-specific, and body composition differs between blacks and whites. OBJECTIVE: We tested the hypothesis that the validity of equations for predicting total body water (TBW) from bioelectrical impedance analysis measurements is likely to depend on the racial background of the group from which the equations were derived. DESIGN: The hypothesis was tested by comparing, in 36 African women, TBW values measured by deuterium dilution with those predicted by 23 equations developed in white, African American, or African subjects. These cross-validations in our African sample were also compared, whenever possible, with results from other studies in black subjects. RESULTS: Errors in predicting TBW showed acceptable values (1.3-1.9 kg) in all cases, whereas a large range of bias (0.2-6.1 kg) was observed independently of the ethnic origin of the sample from which the equations were derived. Three equations (2 from whites and 1 from blacks) showed nonsignificant bias and could be used in Africans. In all other cases, we observed either an overestimation or underestimation of TBW with variable bias values, regardless of racial background, yielding no clear trend for validity as a function of ethnic origin. CONCLUSIONS: The findings of this cross-validation study emphasize the need for further fundamental research to explore the causes of the poor validity of TBW prediction equations across populations rather than the need to develop new prediction equations for use in Africa.

Análisis de rendimiento de aplicaciones paralelas de memoria compartida: problema N-body

Este trabajo analiza el rendimiento de cuatro nodos de cómputo multiprocesador de memoria compartida para resolver el problema N-body. Se paraleliza el algoritmo serie, y se codifica usando el lenguaje C extendido con OpenMP. El resultado son dos variantes que obedecen a dos criterios de optimización diferentes: minimizar los requisitos de memoria y minimizar el volumen de cómputo. Posteriormente, se realiza un proceso de análisis de las prestaciones del programa sobre los nodos de cómputo. Se modela el rendimiento de las variantes secuenciales y paralelas de la aplicación, y de los nodos de cómputo; se instrumentan y ejecutan los programas para obtener resultados en forma de varias métricas; finalmente se muestran e interpretan los resultados, proporcionando claves que explican ineficiencias y cuellos de botella en el rendimiento y posibles líneas de mejora. La experiencia de este estudio concreto ha permitido esbozar una incipiente metodología de análisis de rendimiento, identificación de problemas y sintonización de algoritmos a nodos de cómputo multiprocesador de memoria compartida.

Is the coiled body involved in nucleolar functions?

Coiled bodies (CBs) are structural constituents observed in nuclei of most eukaryotic cells. They usually occur in the nucleoplasm as well as in contact with the nucleolar surface. In this work we studied the hepatocyte nuclei of hibernating dormice in order to investigate possible modifications of CBs along the seasonal cycle. CBs were abundant during hibernation and rapidly disappeared upon arousal from hibernation. Moreover, CBs were frequently found to be integrated into the nucleolar body. Immunocytochemical analyses showed that CBs contain nucleoplasmic as well as nucleolar RNA-processing factors, suggesting an "ambiguous" role for this organelle in the nuclear functions.

Maximal Physiological Parameters during Partial Body-Weight Support Treadmill Testing.

PURPOSE: This study investigated maximal cardiometabolic response while running in a lower body positive pressure treadmill (antigravity treadmill (AG)), which reduces body weight (BW) and impact. The AG is used in rehabilitation of injuries but could have potential for high-speed running, if workload is maximally elevated. METHODS: Fourteen trained (nine male) runners (age 27 ± 5 yr; 10-km personal best, 38.1 ± 1.1 min) completed a treadmill incremental test (CON) to measure aerobic capacity and heart rate (V˙O2max and HRmax). They completed four identical tests (48 h apart, randomized order) on the AG at BW of 100%, 95%, 90%, and 85% (AG100 to AG85). Stride length and rate were measured at peak velocities (Vpeak). RESULTS: V˙O2max (mL·kg·min) was similar across all conditions (men: CON = 66.6 (3.0), AG100 = 65.6 (3.8), AG95 = 65.0 (5.4), AG90 = 65.6 (4.5), and AG85 = 65.0 (4.8); women: CON = 63.0 (4.6), AG100 = 61.4 (4.3), AG95 = 60.7 (4.8), AG90 = 61.4 (3.3), and AG85 = 62.8 (3.9)). Similar results were found for HRmax, except for AG85 in men and AG100 and AG90 in women, which were lower than CON. Vpeak (km·h) in men was 19.7 (0.9) in CON, which was lower than every other condition: AG100 = 21.0 (1.9) (P < 0.05), AG95 = 21.4 (1.8) (P < 0.01), AG90 = 22.3 (2.1) (P < 0.01), and AG85 = 22.6 (1.6) (P < 0.001). In women, Vpeak (km·h) was similar between CON (17.8 (1.1) ) and AG100 (19.3 (1.0)) but higher at AG95 = 19.5 (0.4) (P < 0.05), AG90 = 19.5 (0.8) (P < 0.05), and AG85 = 21.2 (0.9) (P < 0.01). CONCLUSIONS: The AG can be used at maximal exercise intensities at BW of 85% to 95%, reaching faster running speeds than normally feasible. The AG could be used for overspeed running programs at the highest metabolic response levels.

Subjective cognitive decline in patients with mild cognitive impairment and healthy older adults: association with personality traits.

AIM: In normal aging, subjective cognitive decline (SCD) might reflect personality traits or affective states rather than objective cognitive decline. However, little is known on the correlates of SCD in mild cognitive impairment (MCI). The present study investigates SCD in MCI patients and healthy older adults, and explores the association of SCD with personality traits, affective states, behavioral and psychological symptoms (BPS), and episodic memory in patients with MCI as compared with healthy older adults. METHODS: A total of 55 patients with MCI and 84 healthy older adults were recruited. Standard instruments were used to evaluate SCD, episodic memory, BPS and affective states. Premorbid and current personality traits were assessed by proxies using the NEO Personality Inventory Revised. RESULTS: Patients with MCI generally reported SCD more often than healthy older adults. SCD was positively associated with depressive symptoms in both groups. With regard to personality, no significant relationship was found in the healthy older group, whereas agreeableness was significantly negatively related to SCD in the MCI group. No significant association was found between SCD and episodic memory. CONCLUSIONS: SCD is more prevalent in patients with MCI than in the healthy elderly, but it does not reflect an objective cognitive impairment. SCD rather echoes depressive symptoms in both patients with MCI and healthy subjects. The negative association of SCD with agreeableness observed in patients with MCI could indicate that MCI patients scoring high on the agreeableness trait would not report SCD in order to prevent their relatives worrying about their increasing cognitive difficulties.

The behavioral relevance and top-down susceptibility of early, low level multisensory interactions in humans

Abstract (English)General backgroundMultisensory stimuli are easier to recognize, can improve learning and a processed faster compared to unisensory ones. As such, the ability an organism has to extract and synthesize relevant sensory inputs across multiple sensory modalities shapes his perception of and interaction with the environment. A major question in the scientific field is how the brain extracts and fuses relevant information to create a unified perceptual representation (but also how it segregates unrelated information). This fusion between the senses has been termed "multisensory integration", a notion that derives from seminal animal single-cell studies performed in the superior colliculus, a subcortical structure shown to create a multisensory output differing from the sum of its unisensory inputs. At the cortical level, integration of multisensory information is traditionally deferred to higher classical associative cortical regions within the frontal, temporal and parietal lobes, after extensive processing within the sensory-specific and segregated pathways. However, many anatomical, electrophysiological and neuroimaging findings now speak for multisensory convergence and interactions as a distributed process beginning much earlier than previously appreciated and within the initial stages of sensory processing.The work presented in this thesis is aimed at studying the neural basis and mechanisms of how the human brain combines sensory information between the senses of hearing and touch. Early latency non-linear auditory-somatosensory neural response interactions have been repeatedly observed in humans and non-human primates. Whether these early, low-level interactions are directly influencing behavioral outcomes remains an open question as they have been observed under diverse experimental circumstances such as anesthesia, passive stimulation, as well as speeded reaction time tasks. Under laboratory settings, it has been demonstrated that simple reaction times to auditory-somatosensory stimuli are facilitated over their unisensory counterparts both when delivered to the same spatial location or not, suggesting that audi- tory-somatosensory integration must occur in cerebral regions with large-scale spatial representations. However experiments that required the spatial processing of the stimuli have observed effects limited to spatially aligned conditions or varying depending on which body part was stimulated. Whether those divergences stem from task requirements and/or the need for spatial processing has not been firmly established.Hypotheses and experimental resultsIn a first study, we hypothesized that auditory-somatosensory early non-linear multisensory neural response interactions are relevant to behavior. Performing a median split according to reaction time of a subset of behavioral and electroencephalographic data, we found that the earliest non-linear multisensory interactions measured within the EEG signal (i.e. between 40-83ms post-stimulus onset) were specific to fast reaction times indicating a direct correlation of early neural response interactions and behavior.In a second study, we hypothesized that the relevance of spatial information for task performance has an impact on behavioral measures of auditory-somatosensory integration. Across two psychophysical experiments we show that facilitated detection occurs even when attending to spatial information, with no modulation according to spatial alignment of the stimuli. On the other hand, discrimination performance with probes, quantified using sensitivity (d'), is impaired following multisensory trials in general and significantly more so following misaligned multisensory trials.In a third study, we hypothesized that behavioral improvements might vary depending which body part is stimulated. Preliminary results suggest a possible dissociation between behavioral improvements andERPs. RTs to multisensory stimuli were modulated by space only in the case when somatosensory stimuli were delivered to the neck whereas multisensory ERPs were modulated by spatial alignment for both types of somatosensory stimuli.ConclusionThis thesis provides insight into the functional role played by early, low-level multisensory interac-tions. Combining psychophysics and electrical neuroimaging techniques we demonstrate the behavioral re-levance of early and low-level interactions in the normal human system. Moreover, we show that these early interactions are hermetic to top-down influences on spatial processing suggesting their occurrence within cerebral regions having access to large-scale spatial representations. We finally highlight specific interactions between auditory space and somatosensory stimulation on different body parts. Gaining an in-depth understanding of how multisensory integration normally operates is of central importance as it will ultimately permit us to consider how the impaired brain could benefit from rehabilitation with multisensory stimula-Abstract (French)Background théoriqueDes stimuli multisensoriels sont plus faciles à reconnaître, peuvent améliorer l'apprentissage et sont traités plus rapidement comparé à des stimuli unisensoriels. Ainsi, la capacité qu'un organisme possède à extraire et à synthétiser avec ses différentes modalités sensorielles des inputs sensoriels pertinents, façonne sa perception et son interaction avec l'environnement. Une question majeure dans le domaine scientifique est comment le cerveau parvient à extraire et à fusionner des stimuli pour créer une représentation percep- tuelle cohérente (mais aussi comment il isole les stimuli sans rapport). Cette fusion entre les sens est appelée "intégration multisensorielle", une notion qui provient de travaux effectués dans le colliculus supérieur chez l'animal, une structure sous-corticale possédant des neurones produisant une sortie multisensorielle différant de la somme des entrées unisensorielles. Traditionnellement, l'intégration d'informations multisen- sorielles au niveau cortical est considérée comme se produisant tardivement dans les aires associatives supérieures dans les lobes frontaux, temporaux et pariétaux, suite à un traitement extensif au sein de régions unisensorielles primaires. Cependant, plusieurs découvertes anatomiques, électrophysiologiques et de neuroimageries remettent en question ce postulat, suggérant l'existence d'une convergence et d'interactions multisensorielles précoces.Les travaux présentés dans cette thèse sont destinés à mieux comprendre les bases neuronales et les mécanismes impliqués dans la combinaison d'informations sensorielles entre les sens de l'audition et du toucher chez l'homme. Des interactions neuronales non-linéaires précoces audio-somatosensorielles ont été observées à maintes reprises chez l'homme et le singe dans des circonstances aussi variées que sous anes- thésie, avec stimulation passive, et lors de tâches nécessitant un comportement (une détection simple de stimuli, par exemple). Ainsi, le rôle fonctionnel joué par ces interactions à une étape du traitement de l'information si précoce demeure une question ouverte. Il a également été démontré que les temps de réaction en réponse à des stimuli audio-somatosensoriels sont facilités par rapport à leurs homologues unisensoriels indépendamment de leur position spatiale. Ce résultat suggère que l'intégration audio- somatosensorielle se produit dans des régions cérébrales possédant des représentations spatiales à large échelle. Cependant, des expériences qui ont exigé un traitement spatial des stimuli ont produits des effets limités à des conditions où les stimuli multisensoriels étaient, alignés dans l'espace ou encore comme pouvant varier selon la partie de corps stimulée. Il n'a pas été établi à ce jour si ces divergences pourraient être dues aux contraintes liées à la tâche et/ou à la nécessité d'un traitement de l'information spatiale.Hypothèse et résultats expérimentauxDans une première étude, nous avons émis l'hypothèse que les interactions audio- somatosensorielles précoces sont pertinentes pour le comportement. En effectuant un partage des temps de réaction par rapport à la médiane d'un sous-ensemble de données comportementales et électroencépha- lographiques, nous avons constaté que les interactions multisensorielles qui se produisent à des latences précoces (entre 40-83ms) sont spécifique aux temps de réaction rapides indiquant une corrélation directe entre ces interactions neuronales précoces et le comportement.Dans une deuxième étude, nous avons émis l'hypothèse que si l'information spatiale devient perti-nente pour la tâche, elle pourrait exercer une influence sur des mesures comportementales de l'intégration audio-somatosensorielles. Dans deux expériences psychophysiques, nous montrons que même si les participants prêtent attention à l'information spatiale, une facilitation de la détection se produit et ce toujours indépendamment de la configuration spatiale des stimuli. Cependant, la performance de discrimination, quantifiée à l'aide d'un index de sensibilité (d') est altérée suite aux essais multisensoriels en général et de manière plus significative pour les essais multisensoriels non-alignés dans l'espace.Dans une troisième étude, nous avons émis l'hypothèse que des améliorations comportementales pourraient différer selon la partie du corps qui est stimulée (la main vs. la nuque). Des résultats préliminaires suggèrent une dissociation possible entre une facilitation comportementale et les potentiels évoqués. Les temps de réactions étaient influencés par la configuration spatiale uniquement dans le cas ou les stimuli somatosensoriels étaient sur la nuque alors que les potentiels évoqués étaient modulés par l'alignement spatial pour les deux types de stimuli somatosensorielles.ConclusionCette thèse apporte des éléments nouveaux concernant le rôle fonctionnel joué par les interactions multisensorielles précoces de bas niveau. En combinant la psychophysique et la neuroimagerie électrique, nous démontrons la pertinence comportementale des ces interactions dans le système humain normal. Par ailleurs, nous montrons que ces interactions précoces sont hermétiques aux influences dites «top-down» sur le traitement spatial suggérant leur occurrence dans des régions cérébrales ayant accès à des représentations spatiales de grande échelle. Nous soulignons enfin des interactions spécifiques entre l'espace auditif et la stimulation somatosensorielle sur différentes parties du corps. Approfondir la connaissance concernant les bases neuronales et les mécanismes impliqués dans l'intégration multisensorielle dans le système normale est d'une importance centrale car elle permettra d'examiner et de mieux comprendre comment le cerveau déficient pourrait bénéficier d'une réhabilitation avec la stimulation multisensorielle.

Les préférences alimentaires sont-elles influencées par l'index de masse corporelle, l'âge, le sexe ou le tabac [Are food preferences affected by body mass index, age, sex or tobacco?].

In recent decades the percentage of energy derived from dietary fat has increased. The aim of this study was to explore the relationship between food taste preferences, BMI, age, gender and smoking habits. A computerized questionnaire using a hedonic scale (range 0 to 8) to quantify the liking for sweet and savoury, lean and fat foods, was filled by 233 adults: 171 normal weight (131 women, 40 men) and 62 overweight subjects (BMI > 25 kg/m2 42 women, 20 men). The majority of the subjects had a general preference for savoury lean food irrespective of their BMI or gender. Similarly, preference for sweet lean food was not influenced by the magnitude of the BMI. In contrast, overweight subjects had a preference for sweet fat food (p = 0.05) as well as for savoury fat food (p < 0.05). At any age or BMI, men preferred sweet fat food (p < 0.01). This was not the case for women. Overweight men over forty preferred savoury fat food, in contrast to overweight women of the same age (p < 0.01). The same difference existed between normal weight smokers and non-smokers. This study demonstrates that fat food preference plays a potential role in the development of obesity.

Body dissatisfaction on top of depressive mood among adolescent with severe dysmenorrhea

Purpose: Dysmenorrhea is the leading cause of recurrent short-term school absenteeism among adolescent girls. Yet, studies of menstrual symptoms in the light of adolescent psychological background seldom appear in the recent literature. This study aims to determine whether adolescent girls with severe dysmenorrhea (SD) have different body perception on top of poorer psychological health. Methods: We analyzed data from the Swiss Multicentre Adolescent Survey on Health (SMASH 2002) among a nationally representative sample of adolescents (n = 7548; 3340 females) aged 16 to 20 years attending post-mandatory education. Dysmenorrhea was defined as presence of abdominal or back pain during menstruation on the last 12 months. The severity of dysmenorrhea was defined according to the impact on daily activity and was assessed by 3 questions on the way menstruations interfere with daily life: 1) "You feel well and have normal activities", 2)"you must stay at home" and 3) "you feel restricted in your school or professional activities". Studied variables were: depressive symptoms, suicidal attempt, sexual abuse, health perception in general, body satisfaction, desire to modify body shape, and disordered eating behavior (DEB) with restrictive or bulimic tendency. Controlling variables included socio-economic status (SES) as measured by both parent's level of education, gynecological age (age-age at menarche), academic track (student/apprentice) and age. Results: 12.4% (95% CI: 11.0-14) declared severe dysmenorrhea, 74.2% (95% CI: 71.8-76.5) mild to moderate dysmenorrhea and 13,4% (95% CI: 11.5-15.5) had no dysmenorrhea. Compared to their peers, controlling for confounding variables, subjects with SD were more numerous to report depressive symptoms (AOR: 1.73; 95% CI: 1.39-2.15), to feel in poor health (AOR: 1.44; 95% CI: 1.14-1.81). Moreover, the proportion of those reporting dissatisfaction with their body appearance was higher (AOR: 1.48; 95% CI: 1.00-2.18). Conclusion: Patients with SD not only show a different profile than their peers in terms of their mental health and health perception, but also a distinct relation to their body. Therefore clinicians should pay particular attention to patients with SD and offer them a global evaluation keeping in mind what can be associated with SD.

Dose-dependent positive association between cigarette smoking, abdominal obesity and body fat: cross-sectional data from a population-based survey.

ABSTRACT: BACKGROUND: Although smokers tend to have a lower body-mass index than non-smokers, smoking may favour abdominal body fat accumulation. To our knowledge, no population-based studies have assessed the relationship between smoking and body fat composition. We assessed the association between cigarette smoking and waist circumference, body fat, and body-mass index. METHODS: Height, weight, and waist circumference were measured among 6,123 Caucasians (ages 35-75) from a cross-sectional population-based study in Switzerland. Abdominal obesity was defined as waist circumference>=102 cm for men and >=88 cm for women. Body fat (percent total body weight) was measured by electrical bioimpedance. Age- and sex-specific body fat cut-offs were used to define excess body fat. Cigarettes smoked per day were assessed by self-administered questionnaire. Age-adjusted means and odds ratios were calculated using linear and logistic regression. RESULTS: Current smokers (29% of men and 24% of women) had lower mean waist circumference, body fat percentage, and body-mass index compared with non-smokers. Age-adjusted mean waist circumference and body fat increased with cigarettes smoked per day among smokers. The association between cigarettes smoked per day and body-mass index was non-significant. Compared with light smokers, the adjusted odds ratio (OR) for abdominal obesity in men was 1.28 (0.78-2.10) for moderate smokers and 1.94 (1.15-3.27) for heavy smokers (P=0.03 for trend), and 1.07 (0.72-1.58) and 2.15 (1.26-3.64) in female moderate and heavy smokers, respectively (P<0.01 for trend). Compared with light smokers, the OR for excess body fat in men was 1.05 (95% CI: 0.58-1.92) for moderate smokers and 1.15 (0.60-2.20) for heavy smokers (P=0.75 for trend) and 1.34 (0.89-2.00) and 2.11 (1.25-3.57), respectively in women (P=0.07 for trend). CONCLUSION: Among smokers, cigarettes smoked per day were positively associated with central fat accumulation, particularly in women.

Pluralité des corps. 1. Les corps de La medicine [Multifaceted body. I. The bodies of medicine].

Le corps humain est l'objet privilégié d'action de la médecine, mais aussi réalité vécue, image, symbole, représentation et l'objet d'interprétation et de théorisation. Tous ces éléments constitutifs du corps influencent la façon dont la médecine le traite. Dans cette série de trois articles, nous abordons le corps sous différentes perspectives : médicale (1), phénoménologique (2), psychosomatique et socio-anthropologique (3). Ce premier article traite des représentations du corps en médecine, dont nous décrivons quatre types distincts, qui renvoient à autant de démarches scientifiques spécifiques et de formes de légitimité clinique : le corps-objet de l'anatomie, le corps-machine de la physiologie, le corps cybernétique de la biologie et le corps statistique de l'épidémiologie. The human body is the object upon which medicine is acting, but also lived reality, image, symbol, representation and the object of elaboration and theory. All these elements which constitute the body influence the way medicine is treating it. In this series of three articles, we address the human body from various perspectives: medical (1), phenomenological (2), psychosomatic and socio-anthropological (3). This first article discusses four distinct types of representation of the body within medicine, each related to a specific epistemology and shaping a distinct kind of clinical legitimacy: the body-object of anatomy, the body-machine of physiology, the cybernetic body of biology, the statistical body of epidemiology.

Destruction of invariant curves in the restricted circular planar three body problem using comparison of action

"Vegeu el resum a l'inici del document del fitxer adjunt."

Epistasis and maternal effects in experimental adaptation to chronic nutritional stress in Drosophila.

Based on ecological and metabolic arguments, some authors predict that adaptation to novel, harsh environments should involve alleles showing negative (diminishing return) epistasis and/or that it should be mediated in part by evolution of maternal effects. Although the first prediction has been supported in microbes, there has been little experimental support for either prediction in multicellular eukaryotes. Here we use a line-cross design to study the genetic architecture of adaptation to chronic larval malnutrition in a population of Drosophila melanogaster that evolved on an extremely nutrient-poor larval food for 84 generations. We assayed three fitness-related traits (developmental rate, adult female weight and egg-to-adult viability) under the malnutrition conditions in 14 crosses between this selected population and a nonadapted control population originally derived from the same base population. All traits showed a pattern of negative epistasis between alleles improving performance under malnutrition. Furthermore, evolutionary changes in maternal traits accounted for half of the 68% increase in viability and for the whole of 8% reduction in adult female body weight in the selected population (relative to unselected controls). These results thus support both of the above predictions and point to the importance of nonadditive effects in adaptive microevolution.

Early antibiotic administration affects the gut barrier function and the immune response to oral antigen in suckling rats

Abstract: The increasingly high hygienic standards characterizing westernized societies correlate with an increasingly high prevalence of allergic disease. Initially based on these observations, the hygiene hypothesis postulates that reduced microbial stimulation during infancy impairs the immune system development and increases the risk of allergy. Moreover, there is increasing evidence that the crosstalk existing between the intestine and the resident microbiota is crucial for gut homeostasis. In particular, bacterial colonization of the gut affects the integrity of the gut barrier and stimulates the development of the gut associated immune tissue, both phenomena being essential for the immune system to mount a controlled response to food antigens. Therefore, alterations in the microbial colonization process, by compromising the barrier homeostasis, may increase the risk of food allergy. In this context, antibiotic treatment, frequently prescribed during infancy, affects gut colonization by bacteria. However, little is known about the impact of alterations in the colonization process on the maturation of the gut barrier and on the immunological response to oral antigens. The objective of this work was to determine the impact of a commercial antibiotic preparation employed in pediatric settings on the gut barrier status at the critical period of the suckling/weaning transition and to evaluate the physiological consequences of this treatment in terms of immune response to food antigens. We established an antibiotic-treated suckling rat model relevant to the pediatric population in terms of type, dose and route of administration of the antibiotic and of changes in the patterns of microbial colonization. Oral tolerance to a novel luminal antigen (ovalbumin) was impaired when the antigen was introduced during antibiotic treatment. These results paralleled to alterations in the intestinal permeability to macromolecules and reduced intestinal expression of genes coding for the major histocomptatibility complex II molecules, which suggest a reduced capacity of antigen handling and presentation in the intestine of the antibiotic-treated animals. In addition, low luminal IgA levels and reduced intestinal expression of genes coding for antimicrobial proteins suggest that protection against pathogens was reduced under antibiotic treatment. In conclusion, we observed in suckling rats that treatment with abroad-spectrum antibiotic commonly used in pediatric practices reduced the capacity of the immune system to develop tolerance. The impact of the antibiotic treatment on the immune response to the antigen-was likely mediated by the alterations of the gut microbiota, through impairment in the mechanisms of antigen handling and presentation. This work reinforces the body of data supporting a key role of the intestinal microbiota modulating the risk of allergy development and leads us to propose that the introduction of new food antigens should be avoided during antibiotic treatment in infants. Résumé: L'augmentation du niveau d'hygiène caractérisant les sociétés occidentales semble être fortement corrélée avec l'augmentation des cas d'allergie dans ces pays. De cette observation est née l'hypothèse qu'une diminution des stimuli microbiens pendant l'enfance modifie le développement du système immunitaire augmentant ainsi le risque d'allergie. En ce sens, un nombre croissant de données indiquent que les interactions existant entre l'intestin et les bactéries résidantes sont cruciales pour l'équilibre du système. En effet, la présence de bactéries dans l'intestin affecte l'intégrité de sa fonction de barrière et stimule le développement du système immunitaire intestinal. Ces deux paramètres étant essentiels à la mise en place d'une réponse contrôlée vis à vis d'un antigène reçu oralement, toute modification du processus naturel de colonisation compromettant l'équilibre intestinal pourrait augmenter le risque d'allergie. Les traitements aux antibiotiques, fréquemment prescrits en pédiatrie, modifient de façon conséquente le processus de colonisation bactérienne. Cependant peu de données existent concernant l'impact d'une altération du processus de colonisation sur la maturation de la barrière intestinale et de la réponse immunitaire dirigée contre un antigène. L'objectif de ce travail était de déterminer l'impact d'un antibiotique commercial et employé en pédiatrie sur l'état de la barrière intestinale au moment critique du sevrage et d'évaluer les conséquences physiologiques d'un tel traitement sur la réponse immune à un antigène alimentaire. Nous avons mis en place un modèle de rats allaités, traités à l'antibiotique, le plus proche possible des pratiques pédiatriques, en terme de nature, dose et voie d'administration de l'antibiotique. Nous avons constaté que l'établissement de la tolérance orale à un nouvel antigène (l'ovalbumine) est altéré quand celui-ci est donné pour la première fois au cours du traitement antibiotique. Ces résultats coïncident avec une diminution de la perméabilité intestinale aux macromolécules, ainsi qu'avec une diminution de l'expression des gènes codant pour les molécules du complexe majeur d'histocomptatibilité de classe II, suggérant une modification de l'apprêtement et de la présentation de l'antigène au niveau intestinal chez les rats traités à l'antibiotique. De plus, un faible taux d'IgA et une diminution de l'expression des gènes codant pour des protéines antimicrobiennes, observés après l'administration d'antibiotique, laissent à penser que la protection contre un pathogène est diminuée lors d'un traitement antibiotique. En conclusion, nous avons observé qu'un traitement antibiotique à large spectre d'activité, couramment utilisé en pédiatrie, réduit la capacité d'induction de la tolérance orale chez le rat allaité. L'impact du traitement antibiotique sur la réponse immune semble induite par l'altération de la flore intestinale via son effet sur les mécanismes d'apprêtement et de présentation de l'antigène. Ce travail renforce l'ensemble des données existantes qui accorde à la flore intestinale un rôle clef dans la modulation du risque de développement d'allergie et nous amène à recommander d'éviter l'introduction d'un nouvel aliment lorsqu'un enfant est traité aux antibiotiques.

Adiposity indicators and blood pressure in children: nothing beyond body mass index?

Obesity is a major risk factor for elevated blood pressure in children. For instance, in a school-based study of 5207 children aged 10-12 years, the prevalence of hypertension, which is sustained elevated blood pressure over several visits, was 1.5%, 3.9% and 17.5% in normal weight, overweight and obese children, respectively. High body mass index (BMI) is commonly used to define overweight and obesity. However, because BMI is merely a proxy for adiposity, there is a longstanding debate about its performance to predict elevated blood pressure (or any other health conditions associated with adiposity) and whether other adiposity indicators, such as waist circumference, waist-to-hip ratio or hip circumference, should not be preferred... In this study, 7.4% of boys and 6.4% of girls had elevated blood pressure. The adiposity indicators were highly correlated to each other, apart from weight, waist-to-hip ratio and skinfold thickness z-scores. All indicators were associated with blood pressure. The ability to identify children with elevated blood pressure, assessed by the area under the receiver operating curve (AUC) statistic, was superior for BMI, body adiposity index and waist-to-height ratio z-scores compared with other indicators. BMI z-scores had a slightly higher AUC than other indicators. The authors concluded that BMIz-scores could be a better predictor of elevated blood pressure in children than other adiposity indicators.