Genetic code on the dyadic plane

We introduce the simple parametrization for the space of codons (triples of nucleotides) by 8\times 8 table. This table (which we call the dyadic plane) possesses the natural 2-adic ultrametric. We show that after this parametrization the genetic code will be a locally constant map of the simple form. The local constancy of this map will describe degeneracy of the genetic code. The map of the genetic code defines 2-adic ultrametric on the space of amino acids. We show that hydrophobic amino acids will be clustered in two balls with respect to this ultrametric. Therefore the introduced parametrization of space of codons exhibits the hidden regularity of the genetic code.Comment: Some gap in the construction was fixe

Coupling theory for counterion distributions based in Tsallis statistics

It is well known that the Poisson-Boltzmann (PB) equation yields the exact counterion density around charged objects in the weak coupling limit. In this paper we generalize the PB approach to account for coupling of arbitrary strength by making use of Tsallis q-exponential distributions. Both the weak coupling and the strong coupling limits are reproduced. For arbitrary coupling we also provide simple analytical expressions which are compared to recent Monte Carlo simulations by A. G. Moreira and R. R. Netz [Europhys. Lett. 52 (2000) 705]. Excellent agreement with these is obtained.Comment: 17 pages, 2 figures, 1 table. Final version, accepted for publication in Physica

In vivo measurements of muscle specific tension in adults and children

This article is available open access through the publisher’s website at the link below. Copyright @ 2009 The Authors.To better understand the effects of pubertal maturation on the contractile properties of skeletal muscle in vivo, the present study investigated whether there are any differences in the specific tension of the quadriceps muscle in 20 adults and 20 prepubertal children of both sexes. Specific tension was calculated as the ratio between the quadriceps tendon force and the sum of the physiological cross-sectional area (PCSA) multiplied by the cosine of the angle of pennation of each head within the quadriceps muscle. The maximal quadriceps tendon force was calculated from the knee extension maximal voluntary contraction (MVC) by accounting for EMG-based estimates of antagonist co-activation, incomplete quadriceps activation using the interpolation twitch technique and magnetic resonance imaging (MRI)-based measurements of the patellar tendon moment arm. The PCSA was calculated as the muscle volume, measured from MRI scans, divided by optimal fascicle length, measured from ultrasound images during MVC at the estimated angle of peak quadriceps muscle force. It was found that the quadriceps tendon force and PCSA of men (11.4 kN, 214 cm2) were significantly greater than those of the women (8.7 kN, 152 cm2; P 0.05) between groups: men, 55 ± 11 N cm−2; women, 57.3 ± 13 N cm−2; boys, 54 ± 14 N cm−2; and girls, 59.8 ± 15 N cm−2. These findings indicate that the increased muscle strength with maturation is not due to an increase in the specific tension of muscle; instead, it can be attributed to increases in muscle size, moment arm length and voluntary activation level

Association of physical activity with muscular strength and fat free mass in adolescents; The HELENA Study

Objective: To analyze the association of objectively assessed physical activity (PA) with muscular strength and fat free mass in adolescents, and to determine whether meeting the current PA recommendations is associated with higher levels of muscular strength and fat free mass. Subjects/Methods: The present cross-sectional study comprised 363 Spanish adolescents (180 females) aged 12.5-17.5 years. PA was assessed by accelerometry and expressed as average PA (counts/min), and min/day of inactive, light, moderate, vigorous and moderate to vigorous PA (MVPA). MVPA was dichotomized into <60 min/day and ≥60. Upper body muscular strength was measured with the handgrip strength test, and lower body muscular strength was measured with the standing broad jump, squat jump, counter movement jump and Abalakov tests. Fat free mass was measured by DXA. Results: We observed positive associations between vigorous PA and all the lower body muscular strength tests except for the counter movement jump in males. PA was not associated with fat free mass in both males and females. Male adolescents engaged in at least 60 min/day MVPA performed better in the standing broad jump test. Conclusions: The findings of the present study suggest that only vigorous PA is associated with muscular strength, particularly lower-body muscular strength in male adolescents

El estatus socioeconómico influencia la condición física en adolescentes europeos : el estudio HELENA

Introduction: The influence of socioeconomic status on health-related fitness is not clear. Aim: To examine the influence of socioeconomic status on health-related fitness in adolescents. Methods: A total of 3,259 adolescents (15.0 ± 1.3 y) from the Healthy Lifestyle in Europe by Nutrition in Ado- lescence Cross-Sectional Study (HELENA-CSS) partici- pated in the study. Socioeconomic status was assessed by the family affluence scale (FAS). Speed-agility, muscular strength and cardiorespiratory fitness were assessed. Covariates included total body fat, physical activity and pubertal status. Results: Adolescents with high FAS had significantly higher fitness levels than their peers of lower FAS cate- gories except for speed-agility and handgrip in boys. Overall, the associations observed presented a medium to large effect size. Conclusion: These results suggest that socioeconomic status is positively associated with physical fitness in European adolescents independently of total body fat and habitual physical activityIntroducción: La influencia del estatus socioeconómico sobre la condición física en relación con la salud no está clara. Objetivo: Examinar la influencia del estatus socioeconómico sobre la condición física en relación con la salud en adolescentes. Metodología: Un total de 3259 adolescentes (15,0 ± 1,3 años) del “Healthy Lifestyle in Europe by Nutrition in Adolescence Cross-Sectional Study” (HELENA-CSS) participaron en el estudio. El estatus socioeconómico fue medido con una escala de riqueza familiar “family affluence scale (FAS)”. Se midieron velocidad-agilidad, fuerza muscular y capacidad aeróbica. Las covariables incluidas fueron grasa corporal total, actividad física y estadio madurativo. Resultados: Los adolescentes con alto FAS tuvieron significativamente mayores niveles de condición física que aquellos con bajo FAS exceptuando los tests de velocidad-agilidad y fuerza de prensión manual en chicos. En general, las asociaciones observadas presentaron un efecto del tamaño de la muestra (effect size) entre medio y largo. Conclusión: Estos resultados sugieren que el estatus socioeconómico esta positivamente asociado con la condición física en adolescentes Europeos independientemente de la grasa corporal total y el nivel de actividad física

Association of heart rate and blood pressure among European adolescents with usual food consumption: the HELENA study

Background and aim: In adults, there is some evidence that improving diet reduces blood pressure (BP) and the subsequent risk of cardiovascular diseases (CVDs). However, studies that analyse this association in adolescents are still scarce. The objective of the present study was to examine the associations between heart rate, systolic (SBP), diastolic (DBP) and mean arterial blood pressure (MAP) among European adolescents and usual intake of vegetables, fruits, dairy products, meat, fish, high-sugar foods and savoury snacks. Methods and results: In total, 2283 adolescents from the HELENA-study (12.5-17.5 years old; 1253 girls) were included. Dietary intake was assessed using two computerized 24-hour dietary recalls. Age, sex, body mass index, maternal educational level, physical activity and Tanner stage were considered as confounders. Associations were examined by mixed model analysis stratified by sex. Tests for trend were assessed by tertiles of intake while controlling for the aforementioned confounders. Dairy products and fish intake were negatively associated with BP and heart rate. Significant decreasing trends were observed for heart rate and BP across tertiles of dairy products, fish intake and high-sugar foods intake (p < 0.05). Significant increasing trends were observed for SBP and MAP across tertiles of savoury snack intake (p < 0.05). Conclusion: Significant but small inverse associations between fish and dairy products consumption with blood pressure and heart rate have been found in European adolescents. Dietary intervention studies are needed to explore these associations in the context of the modification of several risk factors for the prevention of cardiovascular diseases

Valores de referencia para leptina, cortisol, insulina y glucosa entre los adolescentes europeos y su asociación con adiposidad: Estudio Helena

Background and Objective: Adequate concentrations of leptin, cortisol, and insulin are important for a suitable metabolism and development during adolescence. These hormones jointly with glucose play a major role in fat metabolism and development of childhood obesity. Our main objective was to quantify biomarkers as leptin, cortisol, insulin and glucose status in European adolescents to contribute to establish reference ranges. Methods: A representative sample of 927 adolescents (45% males, 14.9±1.2 years for the overall population) from ten European cities of the HELENA study was used to obtain fasting blood samples for these biomarkers. The percentile distributions were computed by sex and age and percentiles were associated with BMI classification. Results: Serum leptin concentration in adolescents varied significantly according to BMI, sex and age (all p<0.001). Cortisol presented a tendency to increase with age, both for females and males, while insulin and glucose were stable with age. Leptin and insulin were highest in obese adolescents (p<0.001), whilst cortisol and glucose did not vary with BMI. Percentiles 5, 25, 50, 75 and 95, 26.70 and 65.33 ng/ml for leptin; 5.00, 8.11, 11.14, 15.00 and 24.51 μg/dl for cortisol and 3.65, 6.15, 8.52, 11.90 and 20.53 μlU/ml for insulin. Conclusions: In adolescents, leptin, cortisol, insulin and glucose concentrations are differently affected by age, sex and BMI. Establishment of reference ranges (percentiles) of these biomarkers would be of great interest when pediatricians have to assess the trend of an adolescent to develop obesity years after.Objetivo: Concentraciones adecuadas de leptina, cortisol e insulina son importantes para un metabolismo normal durante la adolescencia, puesto que valores alterados de estas hormonas, junto con la glucosa, se asocian con el desarrollo de la obesidad infantil. Nuestro principal objetivo fue cuantificar estos marcadores en adolescentes europeos con el fin de establecer rangos de referencia. Métodos: Muestras de sangre procedentes de 927 adolescentes en ayunas (14,9 ± 1,2 años, 45% varones, estudio HELENA), fueron analizadas para cuantificar la leptina, cortisol, insulina y glucosa. Las distribuciones de percentiles se determinaron teniendo en cuenta el sexo y la edad. También se estudió la asociación entre percentiles y la clasificación del IMC. Resultados: La concentración de leptina en suero variaba significativamente con el IMC, el sexo y la edad (todos p<0,001). El cortisol presentó una tendencia a aumentar con la edad, tanto para varones como mujeres, mientras que la insulina y la glucosa eran estables con la edad. La leptina y la insulina fueron más altas en los adolescentes obesos (p <0,001), mientras que el cortisol y glucosa no variaron con el IMC. Los percentiles 5, 25, 50, 75 y 95, para los valores de hormonas fueron, respectivamente: 1.27, 4.06, 11.54, 26.70 y 65.33 ng/ml para la leptina; 5.00, 8.11, 11.14, 15.00 y 24.51 μg/dl para el cortisol y 3.65, 6.15, 8.52, 11.90 y 20.53 μlU/ml de insulina.The HELENA study has taken place with the financial support of the European Community Sixth RTD Framework Programme (Contract FOODCT- 2005-007034). This study was also supported by a grant from the Spanish Ministry of Science and Innovation AGL2007-29784-E

Influence of sex, age, pubertal maturation and body mass index on circulating white blood cell counts in healthy European adolescents—the HELENA study

Percentiles 10th, 25th, 50th, 75th and 90th are presented for circulating white blood cells (WBC), neutrophils, lymphocytes, monocytes, eosinophils and basophils in healthy European adolescents (12.5–17.5 years, n = 405, 48.9 % boys), considering age, sex, puberty and body mass index (BMI). CD3+ (mature T cells), CD4+ (T helper), CD8+ (T cytotoxic), CD16+56+ (natural killer), CD19+ (B cells), CD3+CD45RA+, CD4+CD45RA+, CD8+CD45RA+ (naïve), CD3+CD45RO+, CD4+CD45RO+ and CD8+CD45RO+ (memory) lymphocytes were also analysed by immunophenotyping. Girls presented higher WBC, neutrophil, CD3+CD45RO+ and CD4+CD45RO+ cell counts and CD3+/CD19+ ratio, and lower CD3+CD45RA+ and CD4+CD45RA+ counts than boys. Age was associated with higher neutrophil counts and CD3+/CD19+, and lower CD19+ counts; in boys, with lower CD3+CD45RA+, CD4+CD45RA+ and CD8+CD45RA+ counts as well; in girls, with higher WBC, CD3+CD45RO+ and CD4+CD45RO+ counts. Pubertal maturation in boys was associated with lower WBC and lymphocyte counts; in girls, with higher basophil, CD3+CD45RO+ and CD4+CD45RO+ values. BMI was associated with higher WBC counts; in boys, also with higher lymphocyte counts; in girls, with higher neutrophil, CD4+, CD3+CD45RO+ and CD4+CD45RO+ counts. Conclusion: Our study provides normative values for circulating immune cells in adolescents, highlighting the importance of considering sex, age, pubertal maturation and BMI when establishing reference ranges for WBC in paediatric populations

Impact of physical activity and cardiovascular fitness on total homocysteine concentrations in European adolescents : The HELENA Study

We examined the association of physical activity (PA), cardiovascular fi tness (CVF) and fatness with total homocysteine (tHcy) concentrations in European adolescents. The present study comprised 713 European adolescents aged 14.81.2 y (females 55.3%) from the multicenter HELENA cross-sectional study. PA was assessed through accelerometry, CVF by the 20-m shuttle run test, and body fat by skinfold thicknesses with the Slaughter equation. Plasma folate, cobalamin, and tHcy concentrations were measured. To examine the association of tHcy with PA, CVF, and fatness after controlling for a set of confounders including age, maturity, folate, cobalamin, creatinine, smoking, supplement use, and methylenetetrahydrofolate reductase 677 genotype (CC 47%, CT 43%, TT 10%), bivariate correlations followed by multiple regression models were performed. In the bivariate correlation analysis, tHcy concentrations were slightly negatively correlated (p0.05) with CVF in females (measured both by stages: r 0.118 and by VO2max: r 0.102) and positively with body mass index (r 0.100). However, daily time spent with moderate and vigorous PA showed a weak positive association with tHcy in females (p0.05). tHcy concentrations showed a tendency to decrease with increasing CVF and increase with increasing BMI in female European adolescents. However, tHcy concentrations were positively associated with moderate and vigorous PA in female European adolescents

Relationship between self-reported dietary intake and physical activity levels among adolescents: The HELENA study

Background Evidence suggests possible synergetic effects of multiple lifestyle behaviors on health risks like obesity and other health outcomes. Therefore it is important to investigate associations between dietary and physical activity behavior, the two most important lifestyle behaviors influencing our energy balance and body composition. The objective of the present study is to describe the relationship between energy, nutrient and food intake and the physical activity level among a large group of European adolescents. Methods The study comprised a total of 2176 adolescents (46.2% male) from ten European cities participating in the HELENA (Healthy Lifestyle in Europe by Nutrition in Adolescence) study. Dietary intake and physical activity were assessed using validated 24-h dietary recalls and self-reported questionnaires respectively. Analyses of covariance (ANCOVA) were used to compare the energy and nutrient intake and the food consumption between groups of adolescents with different physical activity levels (1st to 3rd tertile). Results In both sexes no differences were found in energy intake between the levels of physical activity. The most active males showed a higher intake of polysaccharides, protein, water and vitamin C and a lower intake of saccharides compared to less active males. Females with the highest physical activity level consumed more polysaccharides compared to their least active peers. Male and female adolescents with the highest physical activity levels, consumed more fruit and milk products and less cheese compared to the least active adolescents. The most active males showed higher intakes of vegetables and meat, fish, eggs, meat substitutes and vegetarian products compared to the least active ones. The least active males reported the highest consumption of grain products and potatoes. Within the female group, significantly lower intakes of bread and cereal products and spreads were found for those reporting to spend most time in moderate to vigorous physical activity. The consumption of foods from the remaining food groups, did not differ between the physical activity levels in both sexes. Conclusion It can be concluded that dietary habits diverge between adolescents with different self-reported physical activity levels. For some food groups a difference in intake could be found, which were reflected in differences in some nutrient intakes. It can also be concluded that physically active adolescents are not always inclined to eat healthier diets than their less active peers.The HELENA study took place with the financial support of the European Community Sixth RTD Framework Programme (Contract FOOD-CT: 2005-007034). This work was also partially supported by the European Union, in the framework of the Public Health Programme (ALPHA project, Ref: 2006120), the Swedish Council for Working Life and Social Research (FAS), the Spanish Ministry of Education (EX-2007-1124, and EX-2008-0641), and the Spanish Ministry of Health, Maternal, Child Health and Development Network (number RD08/0072) (JPRL, LAM)