Modelos de variables latentes en patrones de alimentación y actividad física en niños/adolescentes: una revisión sistemática / Models of latent variables used for eating and physical activity patterns in children/ adolescents: a systematic review

Introducción. Debido a la poca evidencia sobre el modelamiento de los patrones de alimentación y actividad física (AF), basado en variables latentes, el presente estudio de revisión pretende describir las técnicas estadísticas aplicadas para modelar estos patrones en niños y adolescentes y valorar su calidad metodológica. Materiales y métodos. La búsqueda se realizó en bases de datos electrónicas (Science Direct, PubMed, SCOPUS, Web of science y Cochrane) con las palabras "diet", 'physical activity', children y 'latent variable'. Se incluyeron artículos que utilizaron modelos estadísticos basados en variables latentes para analizar patrones de alimentación y AF en niños y adolescentes sanos, publicados entre 2014­2019, en inglés o español. Resultados. Entre los 27 artículos seleccionados, el Modelo de Ecuaciones Estructurales (MEE) fue el más utilizado (77,78%); seguido del Modelo de Perfil Latente (7,41%), mientras, el restante, 14,81% aplican el Modelo del Factor Común, Modelo Ecológico y el Modelo de Regresión Logística Multinivel. El MEE fue aplicado a 12 de los 16 artículos con enfoque de AF, y en 7 de los 9 artículos con enfoque de Alimentación. El 48,15% de los estudios sí justificaba el uso del modelo, y el 37,04% poseen una calidad "Excelente" (cumplen el 85% o más de los ítems de STROBE). Conclusiones. El MEE fue el más utilizado para abstraer los patrones de AF y alimentación en niños y adolescentes, sin embargo, solo la mitad de los artículos justifica su pertinencia. Las guías de reporte de estudios deberían evaluar la calidad metodológica de los modelos estadísticos aplicados(AU)

Introduction. Due to the limited evidence on the modeling of eating and physical activity (PA) patterns based on latent variables, the present review study aims to describe the statistical techniques applied to model these patterns in children and adolescents and to assess their methodological quality. Materials and methods. The search was performed in electronic databases (Science Direct, PubMed, SCOPUS, Web of science and Cochrane) with the words 'diet', 'physical activity', children and 'latent variable'. We included articles that used statistical models based on latent variables to analyze diet and PA patterns in healthy children and adolescents, published between 2014-2019, in English or Spanish. Results. Among the 27 selected articles, the Structural Equation Model (SEM) was the most used (77.78%); followed by the Latent Profile Model (7.41%), while, the remaining 14.81% applied the Common Factor Model, Ecological Model and Multilevel Logistic Regression Model. The SEM was applied to 12 of the 16 articles with PA approach, and in 7 of the 9 articles with eating approach. The 48.15% of studies did justify the use of the model, and 37.04% were classified as "Excellent" quality (meet 85% or more of the STROBE items). Conclusions. The SEM was the most commonly used to model the PA and eating patterns in children and adolescents, however, only half of the articles justify their relevance. Study reporting guidelines should evaluate the methodological quality of the statistical models applied(AU)

Unhealthy food consumption among Ecuadorian children: A cross-sectional study in the context of the school food regulation / Consumo de alimentos poco saludables en niños ecuatorianos: estudio transversal en el contexto del reglamento de alimentación escolar

Introduction. The intake of energy-dense unhealthy food at school could influence the overall energy intake of children. Objective: To characterize the patterns of buying a snack at school and to analyze the association of these patterns with the source of the school snack (brought from home or bought at school) and screen time. Materials and methods: A cross-sectional study was conducted from October 2018 until May 2019 among school children (9 to 12-year-olds) from Cuenca-Ecuador. Intake of energy-dense unhealthy food groups, the source of the school snack, and screen time were assessed using questionnaires. Multiple correspondence analysis was used to identify intake patterns of unhealthy food groups, and logistic regression to assess the association between intake of energy-dense unhealthy food groups (FG) with the school snack source. Results: Among 1,028 children recruited 63%, 42%, 30% and 22% of the children reported consuming sweets/confiture, savory snacks, fast food, and pastry products, respectively, at least two days per week. Around 39% of the children were classified as "Frequent consumers of energy-dense unhealthy FG". Buying the snack at school was associated with a more frequent intake of sweets/confiture (OR=1.56, CI 95% =1.05-2.32) and fast food (OR=2.01, CI 95% =1.15-3.50) during the week, as well as with being classified in the "frequent consumer of energy-dense unhealthy FG" (OR=1.99, 95% CI=1.40-2.82). Conclusions: Ecuadorian children still consume prohibited unhealthy foods at school. These results reinforce the importance of evaluating, monitoring, and adapting strategies to promote a balanced diet(AU)

Introducción. La ingesta de alimentos poco saludables con alto contenido energético en la escuela podría influir en la ingesta energética total de los niños. Objetivo: Caracterizar los patrones de compra de snacks en el colegio y analizar la asociación de estos patrones con la procedencia del snack escolar (de la casa o comprada en el colegio) y el tiempo de pantalla. Materiales y métodos: Se realizó un estudio transversal (octubre 2018-mayo 2019) en escolares (9-12 años) Cuenca- Ecuador. La ingesta de grupos de alimentos (FG) no saludables altos en energía, la fuente del snack escolar y el tiempo de pantalla se evaluaron mediante cuestionarios. Se utilizó análisis de correspondencias múltiples para identificar patrones de ingesta de FG poco saludables y la regresión logística para evaluar asociación entre la ingesta FG no saludables con la fuente del snack escolar. Resultados: En 1.028 niños 63%, 42%, 30% y 22% declararon consumir dulces/golosinas, aperitivos salados, comida rápida y productos de pastelería, respectivamente, al menos dos/días/ semana. Un 39% fueron clasificados como "Consumidores frecuentes de FG poco saludables de alta densidad energética". La compra de los snacks en el colegio se asoció con una ingesta más frecuente de dulces/golosinas (OR=1,56; IC95%=1,05-2,32) y comida rápida (OR=2,01; IC95%=1,15-3,50) durante la semana y con la clasificación en el grupo" consumidores frecuentes de FG poco saludables de alta densidad energética" (OR=1,99; IC95%=1,40- 2,82). Conclusiones: Los niños ecuatorianos aún consumen alimentos no saludables prohibidos en la escuela. Estos resultados refuerzan la importancia de evaluar, monitorear y adaptar estrategias para promover una dieta balanceada(AU)

The CopA2-Type P1B-Type ATPase CcoI Serves as Central Hub for cbb 3-Type Cytochrome Oxidase Biogenesis.

Copper (Cu)-transporting P1B-type ATPases are ubiquitous metal transporters and crucial for maintaining Cu homeostasis in all domains of life. In bacteria, the P1B-type ATPase CopA is required for Cu-detoxification and exports excess Cu(I) in an ATP-dependent reaction from the cytosol into the periplasm. CopA is a member of the CopA1-type ATPase family and has been biochemically and structurally characterized in detail. In contrast, less is known about members of the CopA2-type ATPase family, which are predicted to transport Cu(I) into the periplasm for cuproprotein maturation. One example is CcoI, which is required for the maturation of cbb 3-type cytochrome oxidase (cbb 3-Cox) in different species. Here, we reconstituted purified CcoI of Rhodobacter capsulatus into liposomes and determined Cu transport using solid-supported membrane electrophysiology. The data demonstrate ATP-dependent Cu(I) translocation by CcoI, while no transport is observed in the presence of a non-hydrolysable ATP analog. CcoI contains two cytosolically exposed N-terminal metal binding sites (N-MBSs), which are both important, but not essential for Cu delivery to cbb 3-Cox. CcoI and cbb 3-Cox activity assays in the presence of different Cu concentrations suggest that the glutaredoxin-like N-MBS1 is primarily involved in regulating the ATPase activity of CcoI, while the CopZ-like N-MBS2 is involved in Cu(I) acquisition. The interaction of CcoI with periplasmic Cu chaperones was analyzed by genetically fusing CcoI to the chaperone SenC. The CcoI-SenC fusion protein was fully functional in vivo and sufficient to provide Cu for cbb 3-Cox maturation. In summary, our data demonstrate that CcoI provides the link between the cytosolic and periplasmic Cu chaperone networks during cbb 3-Cox assembly.

Auditory Processing Disorder Test Battery in European Portuguese-Development and Normative Data for Pediatric Population.

There is an increasing need for state-of-the-art Central Auditory Processing assessment for Portuguese native speakers, applicable as early as possible. As a contribution to answering this need, this paper presents a new battery for Central Auditory Processing assessment for European Portuguese applicable to children aged 5 and above, named BAPA-PE, providing information regarding test selection and development. The battery consists of six behavioral tests: Staggered Spondaic Words (SSW) for European Portuguese, Filtered Speech, Speech in Noise, Detection Interval in Noise, Duration, and Frequency Pattern. The normative data for children aged 5 to 12 are also reported. A sample was obtained of 217 subjects without ear pathology and with typical development. Each age group was composed of at least 30 children. All children were evaluated using pure tone audiometry, speech audiometry, impedance, and otoacoustic emissions. Normative scores are reported for each of the six auditory processing tests. The assessment is applicable to young children (aged 5 and 6). The statistical analyses showed significant effects in scores of Age for all tests and of Ear for several tests. The main result from the work presented, the Auditory Processing Assessment Battery-European Portuguese (BAPA-PE), is available for clinical use with normative data. This battery is a new tool for behaviorism assessment of European Portuguese speakers with suspected central auditory pathology and for monitoring the results of auditory training.

Nature relatedness as a potential factor to promote physical activity and reduce sedentary behavior in Ecuadorian children.

BACKGROUND: Nature relatedness can be associated with health-related outcomes. This study aims to evaluate the associations of nature relatedness with physical activity and sedentary behavior. METHODS: A cross-sectional study involving 9-12 year old children living in Cuenca, Ecuador, was conducted between October 2018 and March 2019. Questionnaires were used to evaluate physical activity (PAQ-C), out-of-school sedentary behavior, nature relatedness and wellbeing. Associations of nature relatedness with physical activity, and sedentary behavior were evaluated using linear regression models or tobit regressions adjusted by age, sex, school type, wellbeing, and body mass index z-score. RESULTS: A total of 1028 children were surveyed (average age:10.4±1.22 years, 52% female.). Nature relatedness was positively associated with physical activity (ß = 0.07; CI 95%: 0.05-0.09; p < 0.001) and non-screen-related sedentary leisure (ß = 3.77 minutes; CI 95%: 0.76-6.68; p < 0.05); it was negatively associated with screen time (ß = -5.59 minutes; CI 95%: -10.53-0.65; p < 0.05). CONCLUSIONS: Findings suggest that nature relatedness is associated with physical activity and some sedentary behaviors among Ecuadorian school-age children. The promotion of nature relatedness has the potential to improve health.

School-based interventions modestly increase physical activity and cardiorespiratory fitness but are least effective for youth who need them most: an individual participant pooled analysis of 20 controlled trials.

OBJECTIVES: To determine if subpopulations of students benefit equally from school-based physical activity interventions in terms of cardiorespiratory fitness and physical activity. To examine if physical activity intensity mediates improvements in cardiorespiratory fitness. DESIGN: Pooled analysis of individual participant data from controlled trials that assessed the impact of school-based physical activity interventions on cardiorespiratory fitness and device-measured physical activity. PARTICIPANTS: Data for 6621 children and adolescents aged 4-18 years from 20 trials were included. MAIN OUTCOME MEASURES: Peak oxygen consumption (VO2Peak mL/kg/min) and minutes of moderate and vigorous physical activity. RESULTS: Interventions modestly improved students' cardiorespiratory fitness by 0.47 mL/kg/min (95% CI 0.33 to 0.61), but the effects were not distributed equally across subpopulations. Girls and older students benefited less than boys and younger students, respectively. Students with lower levels of initial fitness, and those with higher levels of baseline physical activity benefitted more than those who were initially fitter and less active, respectively. Interventions had a modest positive effect on physical activity with approximately one additional minute per day of both moderate and vigorous physical activity. Changes in vigorous, but not moderate intensity, physical activity explained a small amount (~5%) of the intervention effect on cardiorespiratory fitness. CONCLUSIONS: Future interventions should include targeted strategies to address the needs of girls and older students. Interventions may also be improved by promoting more vigorous intensity physical activity. Interventions could mitigate declining youth cardiorespiratory fitness, increase physical activity and promote cardiovascular health if they can be delivered equitably and their effects sustained at the population level.

The Cofactors of Nitrogenases.

In biological nitrogen fixation, the enzyme nitrogenase mediates the reductive cleavage of the stable triple bond of gaseous N2at ambient conditions, driven by the hydrolysis of ATP, to yield bioavailable ammonium (NH4+). At the core of nitrogenase is a complex, ironsulfur based cofactor that in most variants of the enzyme contains an additional, apical heterometal (Mo or V), an organic homocitrate ligand coordinated to this heterometal, and a unique, interstitial carbide. Recent years have witnessed fundamental advances in our understanding of the atomic and electronic structure of the nitrogenase cofactor. Spectroscopic studies have succeeded in trapping and identifying reaction intermediates and several inhibitor- or intermediate- bound structures of the cofactors were characterized by high-resolution X-ray crystallography. Here we summarize the current state of understanding of the cofactors of the nitrogenase enzymes, their interplay in electron transfer and in the six-electron reduction of nitrogen to ammonium and the actual theoretical and experimental conclusion on how this challenging chemistry is achieved.

Prevalence and risk factors for asthma, rhinitis, eczema, and atopy among preschool children in an Andean city.

BACKGROUND: Limited data are available on prevalence and associated risk factors for atopy and allergic diseases from high-altitude urban settings in Latin America. OBJECTIVE: To estimate the prevalence of atopy, asthma, rhinitis, and eczema, and associations with relevant risk factors in preschool children in the Andean city of Cuenca. METHODS: A cross-sectional study was undertaken using a representative sample of 535 children aged 3-5 years attending 30 nursery schools in the city of Cuenca, Ecuador. Data on allergic diseases and risk factors were collected by parental questionnaire. Atopy was measured by skin prick test (SPT) reactivity to a panel of relevant aeroallergens. Associations between risk factors and the prevalence of atopy and allergic diseases were estimated using multivariable logistic regression. RESULTS: Asthma symptoms were reported for 18% of children, rhinitis for 48%, and eczema for 28%, while SPT reactivity was present in 33%. Population fractions of asthma, rhinitis, and eczema attributable to SPT were 3.4%, 7.9%, and 2.9%, respectively. In multivariable models, an increased risk of asthma was observed among children with a maternal history of rhinitis (OR 1.85); rhinitis was significantly increased in children of high compared to low socioeconomic level (OR 2.09), among children with a maternal history of rhinitis (OR 2.29) or paternal history of eczema (OR 2.07), but reduced among children attending daycare (OR 0.64); eczema was associated with a paternal history of eczema (OR 3.73), and SPT was associated with having a dog inside the house (OR 1.67). CONCLUSIONS: A high prevalence of asthma, rhinitis, and eczema symptoms were observed among preschool children in a high-altitude Andean setting. Despite a high prevalence of atopy, only a small fraction of symptoms was associated with atopy. Parental history of allergic diseases was the most consistent risk factor for symptoms in preschool children.

Correction: Prevalence and risk factors for asthma, rhinitis, eczema, and atopy among preschool children in an Andean city.

[This corrects the article DOI: 10.1371/journal.pone.0234633.].

Global analysis of complex PELDOR time traces.

Pulsed electron-electron double resonance (PELDOR, alternatively called DEER for double electron-electron resonance) pulse sequences allow for the detection of echo decay curves that are modulated by dipole-dipole-coupling frequencies of interacting electron spins. With increasing distance between them, the echo decay needs to be monitored over a progressively extended time period. However, since the echo intensity typically falls off exponentially with increasing time, this might be problematic with respect to the minimum signal-to-noise ratio required for a sound data analysis. In this contribution we present the new PELDOR analysis tool GloPel (Global analysis of PELDOR data), an open-source Python-based application, that allows to extract improved-quality distance distributions from PELDOR data for which no ideal signal-to-noise ratio can be achieved for a very long observation window. By using Tikhonov regularization, GloPel allows for the simultaneous analysis of two time traces acquired for a sample in two different observation time windows, thus taking advantage of both, the typically high signal-to-noise ratio of the time trace acquired at early times of the echo decay, and the best possible background function fitted for the decay at later times, which is in most cases superimposed with considerable noise. In this way, short distances are not overseen in the higher noise of the longer time traces while long distances are not artificially shortened by limiting the observation time window of the experiment. Following our suggested data acquisition procedure, a significant reduction of the measurement time may also be achieved.

The Critical E4 State of Nitrogenase Catalysis.

The reaction catalyzed by the nitrogenase enzyme involves breaking the stable triple bond of the dinitrogen molecule and is consequently considered among the most challenging reactions in biology. While many aspects regarding its atomic mechanism remain to be elucidated, a kinetic scheme established by David Lowe and Roger Thorneley has remained a gold standard for functional studies of the enzyme for more than 30 years. Recent three-dimensional structures of ligand-bound states of molybdenum- and vanadium-dependent nitrogenases have revealed the actual site of substrate binding on the large active site cofactors of this class of enzymes. The binding mode of an inhibitor and a reaction intermediate further substantiate a hypothesis by Seefeldt, Hoffman, and Dean that the activation of N2 is made possible by a reductive elimination of H2 that leaves the cofactor in a super-reduced state that can bind and reduce the inert N2 molecule. Here we discuss the immediate implications of the structurally observed mode of binding of small molecules to the enzyme with respect to the early stages of the Thorneley-Lowe mechanism of nitrogenase. Four consecutive single-electron reductions give rise to two bridging hydrides at the cluster surface that can recombine to eliminate H2 and enable the reduced cluster to bind its substrate in a bridging mode.

A bound reaction intermediate sheds light on the mechanism of nitrogenase.

Reduction of N2 by nitrogenases occurs at an organometallic iron cofactor that commonly also contains either molybdenum or vanadium. The well-characterized resting state of the cofactor does not bind substrate, so its mode of action remains enigmatic. Carbon monoxide was recently found to replace a bridging sulfide, but the mechanistic relevance was unclear. Here we report the structural analysis of vanadium nitrogenase with a bound intermediate, interpreted as a µ2-bridging, protonated nitrogen that implies the site and mode of substrate binding to the cofactor. Binding results in a flip of amino acid glutamine 176, which hydrogen-bonds the ligand and creates a holding position for the displaced sulfide. The intermediate likely represents state E6 or E7 of the Thorneley-Lowe model and provides clues to the remainder of the catalytic cycle.

Signaling ammonium across membranes through an ammonium sensor histidine kinase.

Sensing and uptake of external ammonium is essential for anaerobic ammonium-oxidizing (anammox) bacteria, and is typically the domain of the ubiquitous Amt/Rh ammonium transporters. Here, we report on the structure and function of an ammonium sensor/transducer from the anammox bacterium "Candidatus Kuenenia stuttgartiensis" that combines a membrane-integral ammonium transporter domain with a fused histidine kinase. It contains a high-affinity ammonium binding site not present in assimilatory Amt proteins. The levels of phosphorylated histidine in the kinase are coupled to the presence of ammonium, as conformational changes during signal recognition by the Amt module are transduced internally to modulate the kinase activity. The structural analysis of this ammonium sensor by X-ray crystallography and small-angle X-ray-scattering reveals a flexible, bipartite system that recruits a large uptake transporter as a sensory module and modulates its functionality to achieve a mechanistic coupling to a kinase domain in order to trigger downstream signaling events.

A school-based intervention improved dietary intake outcomes and reduced waist circumference in adolescents: a cluster randomized controlled trial.

BACKGROUND: In Ecuador, adolescents' food intake does not comply with guidelines for a healthy diet. Together with abdominal obesity adolescent's inadequate diets are risk factors for non-communicable diseases. We report the effectiveness of a school-based intervention on the dietary intake and waist circumference among Ecuadorian adolescents. METHODS: A pair-matched cluster randomized controlled trial including 1430 adolescents (12-14 years old) was conducted. The program aimed at improving the nutritional value of dietary intake, physical activity (primary outcomes), body mass index, waist circumference and blood pressure (secondary outcomes). This paper reports: (i) the effect on fruit and vegetable intake, added sugar intake, unhealthy snacking (consumption of unhealthy food items that are not in line with the dietary guidelines eaten during snack time; i.e. table sugar, sweets, salty snacks, fast food, soft drinks and packaged food), breakfast intake and waist circumference; and, (ii) dose and reach of the intervention. Dietary outcomes were estimated by means of two 24-h recall at baseline, after the first 17-months (stage one) and after the last 11-months (stage two) of implementation. Dose and reach were evaluated using field notes and attendance forms. Educational toolkits and healthy eating workshops with parents and food kiosks staff in the schools were implemented in two different stages. The overall effect was assessed using linear mixed models and regression spline mixed effect models were applied to evaluate the effect after each stage. RESULTS: Data from 1046 adolescents in 20 schools were analyzed. Participants from the intervention group consumed lower quantities of unhealthy snacks (-23.32 g; 95% CI: -45.25,-1.37) and less added sugar (-5.66 g; 95% CI: -9.63,-1.65) at the end of the trial. Daily fruit and vegetable intake decreased in both the intervention and control groups compared to baseline, albeit this decrease was 23.88 g (95% CI: 7.36, 40.40) lower in the intervention group. Waist circumference (-0.84 cm; 95% CI: -1.68, 0.28) was lower in the intervention group at the end of the program; the effect was mainly observed at stage one. Dose and reach were also higher at stage one. CONCLUSIONS: The trial had positive effects on risk factors for non-communicable diseases, i.e. decreased consumption of unhealthy snacks. The program strategies must be implemented at the national level through collaboration between the academia and policy makers to assure impact at larger scale. TRIAL REGISTRATION: ClinicalTrial.gov-NCT01004367 .

Secondary Structure Determination by Means of ATR-FTIR Spectroscopy.

Specialized infrared spectroscopic techniques have been developed that allow studying the secondary structure of membrane proteins and the influence of crucial parameters like lipid content and detergent. Here, we focus on an ATR-FTIR spectroscopic study of Af-Amt1 and the influence of LDAO/glycerol on its structural integrity. Our results clearly indicate that infrared spectroscopy can be used to identify the adapted sample conditions.

The flavinyl transferase ApbE of Pseudomonas stutzeri matures the NosR protein required for nitrous oxide reduction.

The copper-containing enzyme nitrous oxide reductase (N2OR) catalyzes the transformation of nitrous oxide (N2O) to dinitrogen (N2) in microbial denitrification. Several accessory factors are essential for assembling the two copper sites CuA and CuZ, and for maintaining the activity. In particular, the deletion of either the transmembrane iron-sulfur flavoprotein NosR or the periplasmic protein NosX, a member of the ApbE family, abolishes N2O respiration. Here we demonstrate through biochemical and structural studies that the ApbE protein from Pseudomonas stutzeri, where the nosX gene is absent, is a monomeric FAD-binding protein that can serve as the flavin donor for NosR maturation via covalent flavinylation of a threonine residue. The flavin transfer reaction proceeds both in vivo and in vitro to generate post-translationally modified NosR with covalently bound FMN. Only FAD can act as substrate and the reaction requires a divalent cation, preferably Mg2+ that was also present in the crystal structure. In addition, the reaction is species-specific to a certain extent.

Production and isolation of vanadium nitrogenase from Azotobacter vinelandii by molybdenum depletion.

The alternative, vanadium-dependent nitrogenase is employed by Azotobacter vinelandii for the fixation of atmospheric N2 under conditions of molybdenum starvation. While overall similar in architecture and functionality to the common Mo-nitrogenase, the V-dependent enzyme exhibits a series of unique features that on one hand are of high interest for biotechnological applications. As its catalytic properties differ from Mo-nitrogenase, it may on the other hand also provide invaluable clues regarding the molecular mechanism of biological nitrogen fixation that remains scarcely understood to date. Earlier studies on vanadium nitrogenase were almost exclusively based on a ΔnifHDK strain of A. vinelandii, later also in a version with a hexahistidine affinity tag on the enzyme. As structural analyses remained unsuccessful with such preparations we have developed protocols to isolate unmodified vanadium nitrogenase from molybdenum-depleted, actively nitrogen-fixing A. vinelandii wild-type cells. The procedure provides pure protein at high yields whose spectroscopic properties strongly resemble data presented earlier. Analytical size-exclusion chromatography shows this preparation to be a VnfD2K2G2 heterohexamer.

Two years of school-based intervention program could improve the physical fitness among Ecuadorian adolescents at health risk: subgroups analysis from a cluster-randomized trial.

BACKGROUND: Adolescents with overweight and poor physical fitness have an increased likelihood of developing cardiovascular diseases during adulthood. In Ecuador, a health promotion program improved the muscular strength and speed-agility, and reduced the decline of the moderate-to-vigorous physical activity of adolescents after 28 months. We performed a sub-group analysis to assess the differential effect of this intervention in overweight and low-fit adolescents. METHODS: We performed a cluster-randomized pair matched trial in schools located in Cuenca-Ecuador. In total 20 schools (clusters) were pair matched, and 1440 adolescents of grade 8 and 9 (mean age of 12.3 and 13.3 years respectively) participated in the trial. For the purposes of the subgroup analysis, the adolescents were classified into groups according to their weight status (body mass index) and aerobic capacity (scores in the 20 m shuttle run and FITNESSGRAM standards) at baseline. Primary outcomes included physical fitness (vertical jump, speed shuttle run) and physical activity (proportion of students achieving over 60 min of moderate-to-vigorous physical activity/day). For these primary outcomes, we stratified analysis by weight (underweight, normal BMI and overweight/obese) and fitness (fit and low fitness) groups. Mixed linear regression models were used to assess the intervention effect. RESULTS: The prevalence of overweight/obesity, underweight and poor physical fitness was 20.3 %, 5.8 % and 84.8 % respectively. A higher intervention effect was observed for speed shuttle run in overweight (ß = -1.85 s, P = 0.04) adolescents compared to underweight (ß = -1.66 s, P = 0.5) or normal weight (ß = -0.35 s, P = 0.6) peers. The intervention effect on vertical jump was higher in adolescents with poor physical fitness (ß = 3.71 cm, P = 0.005) compared to their fit peers (ß = 1.28 cm, P = 0.4). The proportion of students achieving over 60 min of moderate-to-vigorous physical activity/day was not significantly different according to weight or fitness status. CONCLUSION: Comprehensive school-based interventions that aim to improve diet and physical activity could improve speed and strength aspects of physical fitness in low-fit and overweight/obese adolescents. TRIAL REGISTRATION: Clinicaltrials.gov identifier NCT01004367 . Registered October 28, 2009.

Nitrogenase FeMoco investigated by spatially resolved anomalous dispersion refinement.

The [Mo:7Fe:9S:C] iron-molybdenum cofactor (FeMoco) of nitrogenase is the largest known metal cluster and catalyses the 6-electron reduction of dinitrogen to ammonium in biological nitrogen fixation. Only recently its atomic structure was clarified, while its reactivity and electronic structure remain under debate. Here we show that for its resting S=3/2 state the common iron oxidation state assignments must be reconsidered. By a spatially resolved refinement of the anomalous scattering contributions of the 7 Fe atoms of FeMoco, we conclude that three irons (Fe1/3/7) are more reduced than the other four (Fe2/4/5/6). Our data are in agreement with the recently revised oxidation state assignment for the molybdenum ion, providing the first spatially resolved picture of the resting-state electron distribution within FeMoco. This might provide the long-sought experimental basis for a generally accepted theoretical description of the cluster that is in line with available spectroscopic and functional data.