The coefficient of cyclic variation: a novel statistic to measure the magnitude of cyclic variation.

BACKGROUND: PERIODIC OR CYCLIC DATA OF KNOWN PERIODICITY ARE FREQUENTLY ENCOUNTERED IN EPIDEMIOLOGICAL AND BIOMEDICAL RESEARCH: for instance, seasonality provides a useful experiment of nature while diurnal rhythms play an important role in endocrine secretion. There is, however, little consensus on how to analysis these data and less still on how to measure association or effect size for the often complex patterns seen. RESULTS: A simple statistic, readily derived from Fourier regression models, provides a readily-understood measure cyclic variation in a wide variety of situations. CONCLUSION: The coefficient of cyclic variation or similar statistics derived from the variance of a Fourier series could provide a universal means of summarising the magnitude of periodic variation

Alkaline Hydrolyzable-Nitrogen, Seeding Date, and Clay-Fixed Ammonium as Potential Indicators of Rice Response to Nitrogen Fertilization in Arkansas

Several potential indicators of rice (Oryza sativa L.) response to nitrogen (N) fertilization include the soil\u3c&rsquos\u3es alkaline hydrolyzable\u3c&minus\u3eN (AH\u3c&minus\u3eN) concentration, seeding date, and the soil\u3c&rsquos\u3es clay\u3c&minus\u3efixed NH4\u3c&ndash\u3eN content. Three studies were conducted to: (1) correlate AH\u3c&minus\u3eN, determined using Illinois Soil Nitrogen Test (ISNT) or Nitrogen Soil Test for Rice (N\u3c&minus\u3eSTaR), to plant parameters of interest and develop a fertilizer N rate calibration curve capable of predicting the 95% relative grain yield (RGY) fertilizer N rate for rice grown on clayey soils; (2) evaluate the influence of seeding date and N fertilization on rice plant growth and grain yield; and (3) evaluate the plant\u3c&minus\u3eavailable portion of clay\u3c&minus\u3efixed NH4\u3c&ndash\u3eN using N\u3c&minus\u3eSTaR and quantify total clay\u3c&minus\u3efixed NH4\u3c&ndash\u3eN using dry combustion. Alkaline hydrolyzable\u3c&minus\u3eN, quantified using ISNT or N\u3c&minus\u3eSTaR in the first study, explained 83% of the variability in calibration based on a 0 to 30\u3c&minus\u3ecm sampling depth. The second study revealed that grain yield exhibited a tendency to be greater for rice seeded in April or May compared to June seeding dates in Arkansas. Results of the third study indicated a low percentage (4\u3c&ndash\u3e6%) of total clay fixed NH4\u3c&ndash\u3eN was predicted to be plant\u3c&minus\u3eavailable NH4\u3c&ndash\u3eN based on N\u3c&minus\u3eSTaR. Fertilizer N rate recommendations based on the ISNT or N\u3c&minus\u3eSTaR soil test methods evaluated in the first study revealed the potential of soil\u3c&minus\u3ebased tests to improve economic, agronomic, and environmental aspects of rice produced on clayey soils. Seeding date selection can influence rice grain yield which may in turn influence fertilizer N management. However, the fertilizer N rate required to maximize grain yield when seeding date was delayed remained unclear following completion of the second study and continued research is required to identify the influence of seeding date on the yield\u3c&minus\u3emaximizing, fertilizer N rate for rice grown in Arkansas. The recovery of clay\u3c&minus\u3efixed NH4\u3c&ndash\u3eN by N\u3c&minus\u3eSTaR indicated a portion of total clay\u3c&minus\u3efixed NH4\u3c&ndash\u3eN was expected to be available for plant uptake. However, additional research is required to verify the low recovery of clay\u3c&minus\u3efixed NH4\u3c&ndash\u3eN and the influence of clay\u3c&minus\u3efixed NH4\u3c&ndash\u3eN on the quantity of AH\u3c&minus\u3eN determined by N\u3c&minus\u3eSTaR

Growth faltering in low-income countries.

Meta-analysis of growth data from over 50 low and low-middle income countries shows a consistent pattern of stunting and poor weight gain from about 3 months of age and persisting until at least 5 years. Children tend not to be wasted because their short stature offsets their underweight, leading to a rather adequately proportioned appearance. This frequently conceals the true levels of malnutrition in communities. At the macro-environmental level such growth faltering is due to the combined effects of poverty, food insecurity, low-dietary diversity, a highly infectious environment, poor washing facilities and poor understanding of the principles of nutrition and hygiene. These tend to be ameliorated as communities pass through the demographic transition with improved incomes and education. Because such changes will take generations to achieve, the global health community continues to search for effective interim solutions. Disappointingly, apart from intensive feeding programmes aimed at rehabilitating severely malnourished children, there are few examples of very successful nutrition interventions. This emphasizes the need for a better understanding of the etiology of growth failure. This paper uses anthropometric data collected over 6 decades in subsistence-farming communities from rural Gambia to illustrate the typical key features of growth faltering. Arising from this analysis, and from gaps in the published literature, the following issues are highlighted as still requiring a better resolution: (1) the pre-natal and inter-generational influences on growth failure; (2) the ontogeny of the infant immune system; (3) the exact nature of the precipitating insults that initiate gastroenteropathy; (4) the effects of both enteric and systemic infections on the hormonal regulation of growth; (5) interactions between macro- and micro-nutrient deficiencies and infections in causing growth failure, and (6) the role of the microbiome in modulating dietary influences on health and growth

Gastric Emptying Rate of Young Cyclists by Magnetic Resonance Imaging: Three Case Studies

Gastric emptying rate during exercise has been documented in adult athletes, but not in younger athletes because of the utilization of invasive techniques. However, magnetic resonance imaging (MRI) is a noninvasive alternative. The aim of this study was to pilot the sequencing of MRI to a typical fluid intake strategy, in order to assess the viability of the procedure. Therefore, we compared the gastric emptying rate of water and a carbohydrate drink in three well-trained 17-year-old cyclists using MRI. Each participant cycled 4 bouts of 15 minutes each at moderate intensity followed by a ∼15-minute time trial. Water or carbohydrate drinks were distributed in amounts of 200–250 mL. After an initial baseline MRI scan, cyclists ingested the first drink, cycled 15 minutes, followed by an MRI scan to assess remaining gastric volume. This feeding-exercise-scanning protocol was repeated thereafter. Relative to the initial volume at the start of the time trial, 69% and 72% of water and carbohydrate emptied during the time trial. MRI appears to be a feasible technique to assess gastric emptying rates in youth cyclists

Maternal protein-energy supplementation does not affect adolescent blood pressure in The Gambia.

BACKGROUND: Birthweight, and by inference maternal nutrition during pregnancy, is thought to be an important determinant of offspring blood pressure but the evidence base for this in humans is lacking data from randomized controlled trials. METHODS: The offspring from a maternal prenatal protein-energy supplementation trial were enrolled into a follow-up study of chronic disease risk factors including blood pressure. Subjects were 11-17 years of age and blood pressure was measured in triplicate using an automated monitor (Omron 705IT). One-thousand two-hundred sixty seven individuals (71% of potential participants) were included in the analysis. RESULTS: There was no difference in blood pressure between those whose mothers had consumed protein-energy biscuits during pregnancy and those whose mothers had consumed the same supplement post-partum. For systolic blood pressure the intention-to-treat regression coefficient was 0.46 (95% CI: -1.12, 2.04). Mean systolic blood pressure for control children was 110.2 (SD +/- 9.3) mmHg and for intervention children was 110.8 (SD +/- 8.8) mmHg. Mean diastolic blood pressure for control children was 64.7 (SD +/- 7.7) mmHg and for intervention children was 64.6 (SD +/- 7.6) mmHg. CONCLUSIONS: We have found no association between maternal prenatal protein-energy supplementation and offspring blood pressure in adolescence amongst rural Gambians. We found some evidence to suggest that offspring body composition may interact with the effect of maternal supplementation on blood pressure

Growth faltering in rural Gambian children after four decades of interventions: a retrospective cohort study

Background Growth faltering remains common in children in sub-Saharan Africa and is associated with substantial morbidity and mortality. Due to a very slow decline in the prevalence of stunting, the total number of children with stunting continues to rise in sub-Saharan Africa. Identifi cation of eff ective interventions remains a challenge. Methods We analysed the eff ect of 36 years of intensive health interventions on growth in infants and young children from three rural Gambian villages. Routine growth data from birth to age 2 years were available for 3659 children between 1976 and 2012. Z scores for weight-for-age, length-for-age, weight-for-length, mid-upper-arm circumference, and head circumference were calculated using the WHO 2006 growth standards. Seasonal patterns of mean Z scores were obtained by Fourier regression. We additionally defi ned growth faltering as fall in Z score between 3 months and 21 months of age. Findings We noted secular improvements in all postnatal growth parameters (except weight-for-length), accompanied by declines over time in seasonal variability. The proportion of children with underweight or stunting at 2 years of age halved during four decades of the study period, from 38·7% (95% CI 33·5–44·0) for underweight and 57·1% (51·9–62·4) for stunting. However, despite unprecedented levels of intervention, postnatal growth faltering persisted, leading to poor nutritional status at 24 months (length-for-age Z score –1·36, 95% CI –1·44 to –1·27, weight-for-age Z score –1·20, –1·28 to –1·11, and head circumference Z score –0·51, –0·59 to –0·43). The prevalence of stunting and underweight remained unacceptably high (30·0%, 95% CI 27·0–33·0, for stunting and 22·1%, 19·4 to 24·8, for underweight). Interpretation A combination of nutrition-sensitive and nutrition-specifi c interventions has achieved a halving of undernutrition rates, but despite these intensive interventions substantial growth faltering remains. We need to understand the missing contributors to growth faltering to guide development of new interventions

Changes in women’s facial skin color over the ovulatory cycle are not detectable by the human visual system

Human ovulation is not advertised, as it is in several primate species, by conspicuous sexual swellings. However, there is increasing evidence that the attractiveness of women’s body odor, voice, and facial appearance peak during the fertile phase of their ovulatory cycle. Cycle effects on facial attractiveness may be underpinned by changes in facial skin color, but it is not clear if skin color varies cyclically in humans or if any changes are detectable. To test these questions we photographed women daily for at least one cycle. Changes in facial skin redness and luminance were then quantified by mapping the digital images to human long, medium, and shortwave visual receptors. We find cyclic variation in skin redness, but not luminance. Redness decreases rapidly after menstrual onset, increases in the days before ovulation, and remains high through the luteal phase. However, we also show that this variation is unlikely to be detectable by the human visual system. We conclude that changes in skin color are not responsible for the effects of the ovulatory cycle on women’s attractiveness

Progressive influence of body mass index-associated genetic markers in rural Gambians.

BACKGROUND: In populations of European ancestry, the genetic contribution to body mass index (BMI) increases with age during childhood but then declines during adulthood, possibly due to the cumulative effects of environmental factors. How the effects of genetic factors on BMI change with age in other populations is unknown. SUBJECTS AND METHODS: In a rural Gambian population (N=2535), we used a combined allele risk score, comprising genotypes at 28 'Caucasian adult BMI-associated' single nucleotide polymorphisms (SNPs), as a marker of the genetic influence on body composition, and related this to internally-standardised z-scores for birthweight (zBW), weight-for-height (zWT-HT), weight-for-age (zWT), height-for-age (zHT), and zBMI cross-sectionally and longitudinally. RESULTS: Cross-sectionally, the genetic score was positively associated with adult zWT (0.018±0.009 per allele, p=0.034, N=1426) and zWT-HT (0.025±0.009, p=0.006), but not with size at birth or childhood zWT-HT (0.008±0.005, p=0.11, N=2211). The effect of the genetic score on zWT-HT strengthened linearly with age from birth through to late adulthood (age interaction term: 0.0083 z-scores/allele/year; 95% CI 0.0048 to 0.0118, p=0.0000032). CONCLUSIONS: Genetic variants for obesity in populations of European ancestry have direct relevance to bodyweight in nutritionally deprived African settings. In such settings, genetic obesity susceptibility appears to regulate change in weight status throughout the life course, which provides insight into its potential physiological role

RBC barcoding allows for the study of erythrocyte population dynamics and P. falciparum merozoite invasion.

Plasmodium falciparum invasion of host erythrocytes is essential for the propagation of the blood stage of malaria infection. Additionally, the brief extracellular merozoite stage of P. falciparum represents one of the rare windows during which the parasite is directly exposed to the host immune response. Therefore, efficient invasion of the host erythrocyte is necessary not only for productive host erythrocyte infection, but also for evasion of the immune response. Host traits, such as hemoglobinopathies and differential expression of erythrocyte invasion ligands, can protect individuals from malaria by impeding parasite erythrocyte invasion. Here we combine RBC barcoding with flow cytometry to study P. falciparum invasion. This novel high-throughput method allows for the (i) direct comparison of P. falciparum invasion into different erythrocyte populations and (ii) assessment of the impact of changing erythrocyte population dynamics on P. falciparum invasion

Influence of intergenerational in utero parental energy and nutrient restriction on offspring growth in rural Gambia.

The prenatal environment can alter an individual's developmental trajectory with long-lasting effects on health. Animal models demonstrate that the impact of the early life environment extends to subsequent generations, but there is a paucity of data from human populations on intergenerational transmission of environmentally induced phenotypes. Here we investigated the association of parental exposure to energy and nutrient restriction in utero on their children's growth in rural Gambia. In a Gambian cohort with infants born between 1972 and 2011, we used multiple regression to test whether parental season of birth predicted offspring birth weight (n = 2097) or length (n = 1172), height-for-age z score (HAZ), weight-for-height z score (WHZ), and weight-for-age z score (WAZ) at 2 yr of age (n = 923). We found that maternal exposure to seasonal energy restriction in utero was associated with reduced offspring birth length (crude:-4.2 mm, P = 0.005; adjusted: -4.0 mm, P = 0.02). In contrast, paternal birth season predicted offspring HAZ at 24 mo (crude: -0.21, P = 0.005; adjusted: -0.22, P = 0.004) but had no discernible impact at birth. Our results indicate that periods of nutritional restriction in a parent's fetal life can have intergenerational consequences in human populations. Fetal growth appears to be under matriline influence, and postnatal growth appears to be under patriline intergenerational influences.-Eriksen, K. G., Radford, E. J., Silver, M. J., Fulford, A. J. C., Wegmüller, R., Prentice, A. M. Influence of intergenerational in utero parental energy and nutrient restriction on offspring growth in rural Gambia