416 research outputs found

    Body composition in Nepalese children using isotope dilution: the production of ethnic-specific calibration equations and an exploration of methodological issues.

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    Background. Body composition is important as a marker of both current and future health. Bioelectrical impedance (BIA) is a simple and accurate method for estimating body composition, but requires population-specific calibration equations. Objectives. (1) To generate population specific calibration equations to predict lean mass (LM) from BIA in Nepalese children aged 7-9 years. (2) To explore methodological changes that may extend the range and improve accuracy. Methods. BIA measurements were obtained from 102 Nepalese children (52 girls) using the Tanita BC-418. Isotope dilution with deuterium oxide was used to measure total body water and to estimate LM. Prediction equations for estimating LM from BIA data were developed using linear regression, and estimates were compared with those obtained from the Tanita system. We assessed the effects of flexing the arms of children to extend the range of coverage towards lower weights. We also estimated potential error if the number of children included in the study was reduced. Findings. Prediction equations were generated, incorporating height, impedance index, weight and sex as predictors (R (2) 93%). The Tanita system tended to under-estimate LM, with a mean error of 2.2%, but extending up to 25.8%. Flexing the arms to 90° increased the lower weight range, but produced a small error that was not significant when applied to children <16 kg (p 0.42). Reducing the number of children increased the error at the tails of the weight distribution. Conclusions. Population-specific isotope calibration of BIA for Nepalese children has high accuracy. Arm position is important and can be used to extend the range of low weight covered. Smaller samples reduce resource requirements, but leads to large errors at the tails of the weight distribution

    Blood pressure and the capacity-load model in 8-year-old children from Nepal: Testing the contributions of kidney size and intergenerational effects.

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    OBJECTIVES: Growth patterns in early life are increasingly linked with subsequent cardio-metabolic risk, but the underlying mechanisms require elucidation. We have developed a theoretical model of blood pressure, treating it as a function of homeostatic metabolic capacity, and antagonistic metabolic load. We sought to differentiate prenatal and postnatal components of metabolic capacity, and to identify intergenerational contributions to offspring capacity and load. METHODS: We followed up at 8 years a cohort of children originally recruited into a randomized trial of maternal micronutrient supplementation in pregnancy. Maternal anthropometry was measured at recruitment. Offspring anthropometry was measured at birth, 2 years and 8 years. Offspring blood pressure, kidney size, and body composition were measured at 8 years. Regression analysis was used to investigate potential associations of maternal phenotype, birth phenotype, and current body composition with kidney size and blood pressure. RESULTS: Blood pressure was positively associated with body fat, but negatively associated with birth weight and relative leg length. Kidney size was positively associated with birth weight but not with relative leg length. Adjusting for adiposity, blood pressure was independently negatively associated with birth weight, relative leg length, and kidney length. Maternal height and BMI predicted offspring size at birth and at 8 years, but not blood pressure. CONCLUSIONS: Our data provide support for the capacity-load model of blood pressure in Nepalese children. Fetal and postnatal growth and kidney dimensions all contribute to metabolic capacity. Maternal phenotype contributed to offspring capacity and load, but these associations did not propagate to blood pressure. Am. J. Hum. Biol., 2016. © 2016 The Authors American Journal of Human Biology Published by Wiley Periodicals, Inc

    Effects of shrimp-farm effluents on the food web structure in subtropical coastal lagoons

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    Received 4 October 2010, Revised 24 March 2011, Accepted 29 March 2011, Available online 19 April 2011Although numerous studies have reported the negative effects of shrimp aquaculture on water quality, little is known about the ecological effects of these practices in coastal lagoons and near-shore marine habitats. The impact of shrimp-farm effluents on the food webs of an impacted subtropical coastal lagoon in the Gulf of California was evaluated through measurements of isotopic (δ13C, δ15N) signatures in sediments, plants and animals, and compared with the results of a near-pristine reference site. Degradation was manifested in a strong reduction on fish diversity at the perturbed site. δ13C signatures provided ambiguous evidence of degradation while δ15N was a better descriptor of shrimp-farm effluent impact on coastal lagoon food webs. The site receiving nutrient-rich discharges showed significant enrichment of δ15N (≈ 5‰) in sediments, macroalgae, benthic algae, filterfeeders and omnivorous feeders, resulting in qualitative differences in foodweb structure between both lagoons. The food web in the perturbed site was sustained by sediment detritus and dominated by opportunistic species. The lowest influence on δ15N signatures by aquaculture discharges recorded in the upper trophic levels could be explained by the shift in the composition of biotic communities, and associated feeding strategies. While alterations in resource availability do not affect directly food chain length, trophic linkages between food web compartments can be reduced as a result of shrimp farm impacts. Our study demonstrates that nutrient-enriched discharges from shrimp-farm aquaculture generate changes in the availability of food sources, which reduce biodiversity and alter structural and functional food web characteristics.This research was supported by the Mexican Secretary of Natural Resources and Environment (SEMARNAT-CONACYT; contract SEMAR-NAT-2002-C01-0147) and by the Spanish Ministry of Environment (Organismo Autónomo Parques Nacionales; contracts 2008/001 DECA-MERON and 81/2005 CARBONDA.Peer reviewe

    Pre-service teachers’ beliefs about language teaching and learning: a longitudinal study

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    This paper contains the description of a research project that was carried out in the Bachelor of Arts in English Language Teaching program at a Mexican university. The study was longitudinal and it tracked fourteen students for four semesters of the eight semester program. The aim was to identify pre-service teachers’ beliefs about English language teaching and learning at different stages of instruction while they were taking the teaching practice courses in the program. The instruments employed were questionnaires and semi-structured interviews. The results demonstrated that students made links between theory and practice creating some changes in previous beliefs. The study revealed an increase of awareness and a better understanding of the complex processes involved in teaching and learning. En este artículo se describe una investigación que se llevó a cabo en el programa de Licenciatura en Enseñanza del Inglés de una universidad mexicana. El estudio fue longitudinal, el cual siguió la trayectoria de catorce estudiantes de la licenciatura durante cuatro de los ocho semestres del programa académico. El propósito fue identificar las creencias de estos maestros principiantes, quienes cursabansus clases de práctica docente del programa, acerca de la enseñanza y el aprendizaje del inglés en diferentes etapas de sus estudios. Los instrumentos utilizados fueron cuestionarios y entrevistas semiestructuradas. Los resultados demostraron que los estudiantes articularon la teoría con la práctica, lo cual incidió en sus creencias anteriores. El estudio también reveló que comprendieron mejor los complejos procesos involucrados en la enseñanza y el aprendizaje

    Bioelectrical impedance vector analysis as an indicator of malnutrition in children under five years with and without pneumonia in Mchinji District, Malawi: An exploratory mixed-methods analysis [version 1; peer review: awaiting peer review]

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    Background: Bioelectrical impedance vector analysis (BIVA) is a non-invasive assessment of body composition and cellular health, which may improve the assessment of nutritional status in sick children. We explored the reliability, clinical utility, and acceptability of BIVA, as an indicator of nutritional status for children under five years with and without pneumonia, in Malawi. Methods: We conducted a parallel convergent mixed-methods exploratory study in Mchinji District Hospital, Malawi, in 2017. We planned to recruit a convenience sample of children aged 0-59 months with clinical pneumonia, and without an acute illness. Children had duplicate anthropometric and BIVA measurements taken. BIVA measurements of phase angle (PA) were taken of the whole body, and trunk and arm segments. Reliability was assessed by comparing the variability in the two measures, and clinical utility by estimating the association between anthropometry and PA using linear regression. Focus group discussions with healthcare workers who had not previously used BIVA instrumentation were conducted to explore acceptability. Results: A total of 52 children (24 with pneumonia and 28 healthy) were analysed. The reliability of sequential PA measurements was lower than anthropometric measurements, but trunk and arm segments performed better. The largest associations with PA were a negative relationship with weight-for-age z-score (WAZ) and PA in children with pneumonia in the trunk segment, and a positive association with WAZ in the full body measurement in healthy children. Healthcare workers in focus group discussions expressed trust in BIVA technology and that it would enable more accurate diagnosis of malnutrition; however, they raised concerns about the sustainability and necessary resources to implement BIVA. Conclusions: While healthcare workers were positive towards BIVA as a novel technology, implementation challenges should be expected. The differential direction of association between anthropometry and PA for children with pneumonia warrants further investigation

    Ecological factors related to the widespread distribution of sylvatic Rhodnius ecuadoriensis populations in southern Ecuador

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    <p>Abstract</p> <p>Background</p> <p>Chagas disease transmission risk is a function of the presence of triatomines in domestic habitats. <it>Rhodnius ecuadoriensis </it>is one of the main vectors implicated in transmission of <it>Trypanosoma cruzi </it>in Ecuador. This triatomine species is present in domestic, peridomestic and sylvatic habitats in the country. To determine the distribution of sylvatic populations of <it>R. ecuadoriensis </it>and the factors related to this distribution, triatomine searches were conducted between 2005 and 2009 in southern Ecuador.</p> <p>Methods</p> <p>Manual triatomine searches were conducted by skilled bug collectors in 23 communities. Sylvatic searched sites were selected by a) directed sampling, where microhabitats were selected by the searchers and b) random sampling, where sampling points where randomly generated. Domiciliary triatomine searches were conducted using the one man-hour method. Natural trypanosome infection was determined by microscopic examination and PCR. Generalized linear models were used to test the effect of environmental factors on the presence of sylvatic triatomines.</p> <p>Results</p> <p>In total, 1,923 sylvatic individuals were collected representing a sampling effort of 751 man-hours. Collected sylvatic triatomines were associated with mammal and bird nests. The 1,219 sampled nests presented an infestation index of 11.9%, a crowding of 13 bugs per infested nest, and a colonization of 80% of the nests. Triatomine abundance was significantly higher in squirrel (<it>Sciurus stramineus</it>) nests located above five meters from ground level and close to the houses. In addition, 8.5% of the 820 examined houses in the same localities were infested with triatomines. There was a significant correlation between <it>R. ecuadoriensis </it>infestation rates found in sylvatic and synanthropic environments within communities (<it>p </it>= 0.012). Parasitological analysis revealed that 64.7% and 15.7% of the sylvatic bugs examined (n = 300) were infected with <it>Trypanosoma cruzi </it>and <it>T. rangeli </it>respectively, and 8% of the bugs presented mixed infections.</p> <p>Conclusions</p> <p>The wide distribution of sylvatic <it>R. ecuadoriensis </it>populations may jeopardize the effectiveness of control campaigns conducted to eliminate domestic populations of this species. Also, the high <it>T. cruzi </it>infection rates found in sylvatic <it>R. ecuadoriensis </it>populations in southern Ecuador could constitute a risk for house re-infestation and persistent long-term Chagas disease transmission in the region.</p

    Limitations of selective deltamethrin application for triatomine control in central coastal Ecuador

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    <p>Abstract</p> <p>Background</p> <p>This year-long study evaluated the effectiveness of a strategy involving selective deltamethrin spraying and community education for control of Chagas disease vectors in domestic units located in rural communities of coastal Ecuador.</p> <p>Results</p> <p>Surveys for triatomines revealed peridomestic infestation with <it>Rhodnius ecuadoriensis </it>and <it>Panstrongylus howardi</it>, with infestation indices remaining high during the study (13%, 17%, and 10%, at initial, 6-month, and 12-month visits, respectively), which indicates a limitation of this strategy for triatomine population control. Infestation was found 6 and 12 months after spraying with deltamethrin. In addition, a large number of previously vector-free domestic units also were found infested at the 6- and 12-month surveys, which indicates new infestations by sylvatic triatomines. The predominance of young nymphs and adults suggests new infestation events, likely from sylvatic foci. In addition, infection with <it>Trypanosoma cruzi </it>was found in 65%, 21% and 29% at initial, 6-month and 12-month visits, respectively. All parasites isolated (n = 20) were identified as TcI.</p> <p>Conclusion</p> <p>New vector control strategies need to be devised and evaluated for reduction of <it>T. cruzi </it>transmission in this region.</p
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