Stable carbon and nitrogen isotope enrichment in primate tissues

Isotopic studies of wild primates have used a wide range of tissues to infer diet and model the foraging ecologies of extinct species. The use of mismatched tissues for such comparisons can be problematic because differences in amino acid compositions can lead to small isotopic differences between tissues. Additionally, physiological and dietary differences among primate species could lead to variable offsets between apatite carbonate and collagen. To improve our understanding of the isotopic chemistry of primates, we explored the apparent enrichment (ε*) between bone collagen and muscle, collagen and fur or hair keratin, muscle and keratin, and collagen and bone carbonate across the primate order. We found that the mean ε* values of proteinaceous tissues were small (≤1‰), and uncorrelated with body size or phylogenetic relatedness. Additionally, ε* values did not vary by habitat, sex, age, or manner of death. The mean ε* value between bone carbonate and collagen (5.6 ± 1.2‰) was consistent with values reported for omnivorous mammals consuming monoisotopic diets. These primate-specific apparent enrichment values will be a valuable tool for cross-species comparisons. Additionally, they will facilitate dietary comparisons between living and fossil primates

Behavioral modeling of human choices reveals dissociable effects of physical effort and temporal delay on reward devaluation

There has been considerable interest from the fields of biology, economics, psychology, and ecology about how decision costs decrease the value of rewarding outcomes. For example, formal descriptions of how reward value changes with increasing temporal delays allow for quantifying individual decision preferences, as in animal species populating different habitats, or normal and clinical human populations. Strikingly, it remains largely unclear how humans evaluate rewards when these are tied to energetic costs, despite the surge of interest in the neural basis of effort-guided decision-making and the prevalence of disorders showing a diminished willingness to exert effort (e.g., depression). One common assumption is that effort discounts reward in a similar way to delay. Here we challenge this assumption by formally comparing competing hypotheses about effort and delay discounting. We used a design specifically optimized to compare discounting behavior for both effort and delay over a wide range of decision costs (Experiment 1). We then additionally characterized the profile of effort discounting free of model assumptions (Experiment 2). Contrary to previous reports, in both experiments effort costs devalued reward in a manner opposite to delay, with small devaluations for lower efforts, and progressively larger devaluations for higher effort-levels (concave shape). Bayesian model comparison confirmed that delay-choices were best predicted by a hyperbolic model, with the largest reward devaluations occurring at shorter delays. In contrast, an altogether different relationship was observed for effort-choices, which were best described by a model of inverse sigmoidal shape that is initially concave. Our results provide a novel characterization of human effort discounting behavior and its first dissociation from delay discounting. This enables accurate modelling of cost-benefit decisions, a prerequisite for the investigation of the neural underpinnings of effort-guided choice and for understanding the deficits in clinical disorders characterized by behavioral inactivity

Potential for non-combustible nicotine products to reduce socioeconomic inequalities in smoking: a systematic review and synthesis of best available evidence

While some experts have emphasised the potential for e-cigarettes to facilitate cessation among smokers with low socioeconomic status (SES), there is limited evidence of their likely equity impact. We assessed the potential for electronic cigarettes and other non-combustible nicotine-containing products (NCNPs) to reduce inequalities in smoking by systematically reviewing evidence on their use by SES in countries at stage IV of the cigarette epidemic

Examining the cost effectiveness of interventions to promote the physical health of people with mental health problems: a systematic review

Recently attention has begun to focus not only on assessing the effectiveness of interventions to tackle mental health problems, but also on measures to prevent physical co-morbidity. Individuals with mental health problems are at significantly increased risk of chronic physical health problems, such as cardiovascular disease or diabetes, as well as reduced life expectancy. The excess costs of co-morbid physical and mental health problems are substantial. Potentially, measures to reduce the risk of co-morbid physical health problems may represent excellent value for money

Associations between infant feeding and the size, tempo and velocity of infant weight gain:SITAR analysis of the Gemini twin birth cohort

Objective:Infant growth trajectories, in terms of size, tempo and velocity, may program lifelong obesity risk. Timing of breastfeeding cessation and weaning are both implicated in rapid infant growth; we examined the association of both simultaneously with a range of growth parameters.Design:Longitudinal population-based twin birth cohortSubjects:The Gemini cohort provided data on 4680 UK infants with a median of 10 (IQR 8-15) weight measurements between birth and a median of 6.5 months. Age at breastfeeding cessation and weaning were reported by parents at mean age 8.2 months (s.d. 2.2, range 4-20). Growth trajectories were modelled using SITAR to generate three descriptors of individual growth relative to the average trajectory: size (grams), tempo (weeks, indicating the timing of the peak growth rate), and velocity (% difference from average, reflecting mean growth rate). Complex-samples general linear models adjusting for family clustering and confounders examined associations between infant feeding and SITAR parameters.Results:Longer breastfeeding (> 4 months vs. never) was independently associated with lower growth velocity by 6.8% (s.e.m. 1.3%), and delayed growth tempo by 1.0 (s.e. 0.2 weeks), but not with smaller size. Later weaning ( 6 months vs.<4 months) was independently associated with lower growth velocity by 4.9% (s.e.m. 1.1%) and smaller size by 102 g (s.e.m. 25 g).Conclusions:Infants breastfed for longer grew slower for longer after birth (later peak growth rate) but were no different in size, while infants weaned later grew slower overall and were smaller but the timing of peak growth did not differ. Slower trajectories with a delayed peak in growth may have beneficial implications for programming later obesity risk. Replication in cohorts with longer follow-up, alternative confounding structures or randomised controlled trials are required to confirm the long-term effects and directionality, and to rule out residual confounding.International Journal of Obesity accepted article peview online, 11 April 2014. doi:10.1038/ijo.2014.61