Objectives Roux-en-Y gastric bypass (RYGB) has greater efficacy for weight loss in obese patients than gastric banding (BAND) surgery. We hypothesise that this may result from different effects on ...food hedonics via physiological changes secondary to distinct gut anatomy manipulations. Design We used functional MRI, eating behaviour and hormonal phenotyping to compare body mass index (BMI)-matched unoperated controls and patients after RYGB and BAND surgery for obesity. Results Obese patients after RYGB had lower brain-hedonic responses to food than patients after BAND surgery. RYGB patients had lower activation than BAND patients in brain reward systems, particularly to high-calorie foods, including the orbitofrontal cortex, amygdala, caudate nucleus, nucleus accumbens and hippocampus. This was associated with lower palatability and appeal of high-calorie foods and healthier eating behaviour, including less fat intake, in RYGB compared with BAND patients and/or BMI-matched unoperated controls. These differences were not explicable by differences in hunger or psychological traits between the surgical groups, but anorexigenic plasma gut hormones (GLP-1 and PYY), plasma bile acids and symptoms of dumping syndrome were increased in RYGB patients. Conclusions The identification of these differences in food hedonic responses as a result of altered gut anatomy/physiology provides a novel explanation for the more favourable long-term weight loss seen after RYGB than after BAND surgery, highlighting the importance of the gut–brain axis in the control of reward-based eating behaviour.
Background: Ghrelin, which is a stomach-derived hormone, increases with fasting and energy restriction and may influence eating behaviors through brain hedonic reward-cognitive systems. Therefore, ...changes in plasma ghrelin might mediate counter-regulatory responses to a negative energy balance through changes in food hedonics.Objective: We investigated whether ghrelin administration (exogenous hyperghrelinemia) mimics effects of fasting (endogenous hyperghrelinemia) on the hedonic response and activation of brain-reward systems to food.Design: In a crossover design, 22 healthy, nonobese adults (17 men) underwent a functional magnetic resonance imaging (fMRI) food-picture evaluation task after a 16-h overnight fast (Fasted-Saline) or after eating breakfast 95 min before scanning (730 kcal, 14% protein, 31% fat, and 55% carbohydrate) and receiving a saline (Fed-Saline) or acyl ghrelin (Fed-Ghrelin) subcutaneous injection before scanning. One male subject was excluded from the fMRI analysis because of excess head motion, which left 21 subjects with brain-activation data.Results: Compared with the Fed-Saline visit, both ghrelin administration to fed subjects (Fed-Ghrelin) and fasting (Fasted-Saline) significantly increased the appeal of high-energy foods and associated orbitofrontal cortex activation. Both fasting and ghrelin administration also increased hippocampus activation to high-energy- and low-energy-food pictures. These similar effects of endogenous and exogenous hyperghrelinemia were not explicable by consistent changes in glucose, insulin, peptide YY, and glucagon-like peptide-1. Neither ghrelin administration nor fasting had any significant effect on nucleus accumbens, caudate, anterior insula, or amygdala activation during the food-evaluation task or on auditory, motor, or visual cortex activation during a control task.Conclusions: Ghrelin administration and fasting have similar acute stimulatory effects on hedonic responses and the activation of corticolimbic reward-cognitive systems during food evaluations. Similar effects of recurrent or chronic hyperghrelinemia on an anticipatory food reward may contribute to the negative impact of skipping breakfast on dietary habits and body weight and the long-term failure of energy restriction for weight loss.
Aim: To investigate how putative barriers, forest refugia, and ecological gradients across the lower Guineo-Congolian rain forest shape genetic and phenotypic divergence in the leaf-folding frog ...Afrixalus paradorsalis, and examine the role of adjacent land bridge and sky-islands in diversification. Location: The Lower Guineo-Congolian Forest, the Cameroonian Volcanic Line (CVL), and Bioko Island, Central Africa. Taxon: Afrixalus paradorsalis (Family: Hyperoliidae), an African leaf-folding frog. Methods: We used molecular and phenotypic data to investigate diversity and divergence among the A. paradorsalis species complex distributed across lowland rain forests, a land bridge island, and mountains in Central Africa. We examined the coincidence of population boundaries, landscape features, divergence times, and spatial patterns of connectivity and diversity, and subsequently performed demographic modelling using genome-wide SNP variation to distinguish among divergence mechanisms in mainland (riverine barriers, forest refugia, ecological gradients) and land bridge island populations (vicariance, Overwater dispersal). Results: We detected four genetically distinct allopatric populations corresponding to Bioko Island, the CVL, and two lowland rain forest populations split by the Sanaga River. Although lowland populations are phenotypically indistinguishable, pronounced body size evolution occurs at high elevation, and the timing of the formation of the high elevation population coincides with mountain uplift in the CVL. Spatial analyses and demographic modelling revealed population divergence across mainland Lower Guinea is best explained by forest refugia rather than riverine barriers or ecological gradients, and that the Bioko Island population divergence is best explained by vicariance (marine incursion) rather than overseas dispersal. Main conclusions: We provide growing support for the important role of forest refugia in driving intraspecific divergences in the Guineo-Congolian rain forest. In A. paradorsalis, sky-islands in the CVL have resulted in greater genetic and phenotypic divergences than marine incursions of the land bridge Bioko Island, highlighting important differences in patterns of island-driven diversification in Lower Guinea.
Nutritional state (e.g. fasted vs. fed) and different food stimuli (e.g. high‐calorie vs. low‐calorie, or appetizing vs. bland foods) are both recognized to change activity in brain reward systems. ...Using functional magnetic resonance imaging, we have studied the interaction between nutritional state and different food stimuli on brain food reward systems. We examined how blood oxygen level‐dependent activity within a priori regions of interest varied while viewing pictures of high‐calorie and low‐calorie foods. Pictures of non‐food household objects were included as control stimuli. During scanning, subjects rated the appeal of each picture. Twenty non‐obese healthy adults body mass index 22.1 ± 0.5 kg/m2 (mean ± SEM), age range 19–35 years, 10 male were scanned on two separate mornings between 11:00 and 12:00 h, once after eating a filling breakfast (‘fed’: 1.6 ± 0.1 h since breakfast), and once after an overnight fast but skipping breakfast (‘fasted’: 15.9 ± 0.3 h since supper) in a randomized cross‐over design. Fasting selectively increased activation to pictures of high‐calorie over low‐calorie foods in the ventral striatum, amygdala, anterior insula, and medial and lateral orbitofrontal cortex (OFC). Furthermore, fasting enhanced the subjective appeal of high‐calorie more than low‐calorie foods, and the change in appeal bias towards high‐calorie foods was positively correlated with medial and lateral OFC activation. These results demonstrate an interaction between homeostatic and hedonic aspects of feeding behaviour, with fasting biasing brain reward systems towards high‐calorie foods.
Theory predicts that sexually dimorphic traits under strong sexual selection, particularly those involved with intersexual signaling, can accelerate speciation and produce bursts of diversification. ...Sexual dichromatism (sexual dimorphism in color) is widely used as a proxy for sexual selection and is associated with rapid diversification in several animal groups, yet studies using phylogenetic comparative methods to explicitly test for an association between sexual dichromatism and diversification have produced conflicting results. Sexual dichromatism is rare in frogs, but it is both striking and prevalent in African reed frogs, a major component of the diverse frog radiation termed Afrobatrachia. In contrast to most other vertebrates, reed frogs display female-biased dichromatism in which females undergo color transformation, often resulting in more ornate coloration in females than in males. We produce a robust phylogeny of Afrobatrachia to investigate the evolutionary origins of sexual dichromatism in this radiation and examine whether the presence of dichromatism is associated with increased rates of net diversification. We find that sexual dichromatism evolved once within hyperoliids and was followed by numerous independent reversals to monochromatism. We detect significant diversification rate heterogeneity in Afrobatrachia and find that sexually dichromatic lineages have double the average net diversification rate of monochromatic lineages. By conducting trait simulations on our empirical phylogeny, we demonstrate that our inference of trait-dependent diversification is robust. Although sexual dichromatism in hyperoliid frogs is linked to their rapid diversification and supports macroevolutionary predictions of speciation by sexual selection, the function of dichromatism in reed frogs remains unclear. We propose that reed frogs are a compelling system for studying the roles of natural and sexual selection on the evolution of sexual dichromatism across micro- and macroevolutionary timescales.
To compare a 'bypass-surgery-first' with a 'balloon-angioplasty-first' revascularisation strategy in patients with severe limb ischaemia (SLI) due to infrainguinal disease requiring immediate/early ...revascularisation.
A stratified randomised controlled trial. A Delphi consensus study of vascular surgeons' and interventional radiologists' views on SLI treatment was performed before the trial.
Twenty-seven UK hospitals.
Patients presenting with SLI as the result of infrainguinal atherosclerosis and who, in the opinion of the responsible consultant vascular surgeon and interventional radiologist, required and were suitable for both surgery and angioplasty.
Patients were randomised to either 'bypass-surgery-first' or 'balloon-angioplasty-first' revascularisation strategies.
The primary end point was amputation-free survival (AFS); secondary end points were overall survival (OS), health-related quality of life (HRQoL) and cost-effective use of hospital resources.
AFS at 1 and 3 years was not significantly different for surgery and angioplasty. Interim analysis showed that surgery was associated with significantly lower immediate failure, higher 30-day morbidity and lower 12-month reintervention rates than angioplasty; 30-day mortality was similar. Beyond 2 years from randomisation, hazard ratios (HRs) were significantly reduced for both AFS (adjusted HR 0.37; 95% CI 0.17 to 0.77; p = 0.008) and OS (HR 0.34; 95% CI 0.17 to 0.71; p = 0.004) for surgery relative to angioplasty. By 2008 all but four patients had been followed for 3 years, some for over 7 years: 250 (56%) were dead, 168 (38%) were alive without amputation and 30 (7%) were alive with amputation. Considering the follow-up period as a whole, AFS and OS did not differ between treatments but for patients surviving beyond 2 years from randomisation, bypass was associated with reduced HRs for AFS (HR 0.85; 95% CI 0.50 to 1.07; p = 0.108) and OS (HR 0.61; 95% CI 0.50 to 0.75; p = 0.009), equating to an increase in restricted mean OS of 7.3 months (p = 0.02) and AFS of 5.9 months (p = 0.06) during the subsequent follow-up period. Vein bypasses and angioplasties performed better than prosthetic bypasses. HRQoL was non-significantly better in the surgery group; amputation was associated with a significant reduction in HRQoL. Over the first year, hospital costs for bypass were significantly higher (difference 5420 pounds; 95% CI 1547 pounds to 9294 pounds) than for angioplasty. However, by 3 and at 7 years the differences in cost between the two strategies were no longer significant. Patients randomised to surgery lived, on average, 29 days longer at an additional average cost of 2310 pounds. A 36-month perspective showed not significantly different mean quality-adjusted life times for angioplasty and surgery. The Delphi study revealed substantial disagreement between and among surgeons and radiologists on the appropriateness of bypass surgery or balloon angioplasty.
The findings of our study suggest that in patients with SLI due to infrainguinal disease the decision whether to perform bypass surgery or balloon angioplasty first appears to depend upon anticipated life expectancy. Patients expected to live less than 2 years should usually be offered balloon angioplasty first as it is associated with less morbidity and cost, and such patients are unlikely to enjoy the longer-term benefits of surgery. By contrast, those patients expected to live beyond 2 years should usually be offered bypass surgery first, especially where a vein is available as a conduit. Many patients who could not undergo a vein bypass would probably have been better served by a first attempt at balloon angioplasty than prosthetic bypass. The failure rate of angioplasty in SLI is high (c. 25%) and patients who underwent bypass after failed angioplasty fared significantly worse than those who underwent surgery as their first procedure. The interests of a significant proportion of BASIL patients may have been best served by primary amputation followed by high-quality rehabilitation. Further research is required to confirm or refute the BASIL findings and recommendations; validate the BASIL survival prediction model in a separate cohort of patients with SLI; examine the clinical and cost-effectiveness of new endovascular techniques and devices; and compare revascularisation with primary amputation and with best medical and nursing care in those SLI patients with the poorest survival prospects.
Current Controlled Trials ISRCTN45398889.
We present Dark Energy Spectroscopic Instrument (DESI) observations of the inner halo of M31, which reveal the kinematics of a recent merger—a galactic immigration event—in exquisite detail. Of the ...11,416 sources studied in 3.75 hr of on-sky exposure time, 7438 are M31 sources with well-measured radial velocities. The observations reveal intricate coherent kinematic structure in the positions and velocities of individual stars: streams, wedges, and chevrons. While hints of coherent structures have been previously detected in M31, this is the first time they have been seen with such detail and clarity in a galaxy beyond the Milky Way. We find clear kinematic evidence for shell structures in the Giant Stellar Stream, the Northeast Shelf, and Western Shelf regions. The kinematics are remarkably similar to the predictions of dynamical models constructed to explain the spatial morphology of the inner halo. The results are consistent with the interpretation that much of the substructure in the inner halo of M31 is produced by a single galactic immigration event 1–2 Gyr ago. Significant numbers of metal-rich stars (Fe/H > − 0.5) are present in all of the detected substructures, suggesting that the immigrating galaxy had an extended star formation history. We also investigate the ability of the shells and Giant Stellar Stream to constrain the gravitational potential of M31, and estimate the mass within a projected radius of 125 kpc to be (log10) (MNEW) (<125 kpc)/(Mꙩ) =(11.80+0.12 −0.10 ). The results herald a new era in our ability to study stars on a galactic scale and the immigration histories of galaxies.
The spread of marine pests is occurring at record rates due to globalisation and increasing trade. Environmental DNA (eDNA) is an emerging tool for pest surveillance, allowing for the detection of ...genetic material shed by organisms into the environment. However, factors influencing the spatial and temporal detection limits of eDNA in marine environments are poorly understood. In this study we use eDNA assays to assess the invasive ranges of two marine pests in south-eastern Australia, the kelp Undaria pinnatifida and the seastar Asterias amurensis. We explored the temporal and spatial detection limits of eDNA under different oceanographic conditions by combining estimates of eDNA decay with biophysical modelling. Positive eDNA detections at several new locations indicate the invasive range of both pest species is likely to be wider than currently assumed. Environmental DNA decay rates were similar for both species, with a decay rate constant of 0.035 h−1 for U. pinnatifida, and a decay rate constant of 0.041 h−1 for A. amurensis, resulting in a 57–73% decrease in eDNA concentrations in the first 24 h and decaying beyond the limits of detection after 3–4 days. Biophysical models informed by eDNA decay profiles indicate passive transport of eDNA up to a maximum of 10 to 20 km from its source, with a ~90–95% reduction in eDNA concentration within 1–3 km from the source, depending on local oceanography. These models suggest eDNA signals are likely to be highly localised, even in complex marine environments. This was confirmed with spatially replicated eDNA sampling around an established U. pinnatifida population indicating detection limits of ~750 m from the source. This study highlights the value of eDNA methods for marine pest surveillance and provides a much-needed description of the spatio-temporal detection limits of eDNA under different oceanographic conditions.
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•eDNA surveys, decay trials and biophysical models are used to assess the geographic range of two invasive species.•eDNA surveys indicate the invasive ranges of the two species are much wider than previously reported.•eDNA for both invasive species decayed rapidly in the first 24 h.•Biophysical models show eDNA signals are highly localised, even in complex marine environments.•Marine pest surveillance and monitoring is expected to be greatly assisted by eDNA technologies.
Secondary sympatry amongst sister lineages is strongly associated with genetic and ecological divergence. This pattern suggests that for closely related species to coexist in secondary sympatry, they ...must accumulate differences in traits that mediate ecological and/or reproductive isolation. Here, we characterized inter‐ and intraspecific divergence in three giant tree frog species whose distributions stretch across West and Central Africa. Using genome‐wide single‐nucleotide polymorphism data, we demonstrated that species‐level divergence coincides temporally and geographically with a period of large‐scale forest fragmentation during the late Pliocene. Our environmental niche models further supported a dynamic history of climatic suitability and stability, and indicated that all three species occupy distinct environmental niches. We found modest morphological differentiation amongst the species with significant divergence in tympanum diameter and male advertisement call. In addition, we confirmed that two species occur in secondary sympatry in Central Africa but found no evidence of hybridization. These patterns support the hypothesis that cycles of genetic exchange and isolation across West and Central Africa have contributed to globally significant biodiversity. Furthermore, divergence in both ecology and reproductive traits appear to have played important roles in maintaining distinct lineages. At the intraspecific level, we found that climatic refugia, precipitation gradients, marine incursions, and potentially riverine barriers generated phylogeographic structure throughout the Pleistocene and into the Holocene. Further studies examining phenotypic divergence and secondary contact amongst these geographically structured populations may demonstrate how smaller scale and more recent biogeographic barriers contribute to regional diversification.
La sympatrie secondaire parmi les espèces sœurs est fortement associée à la divergence génétique et écologique. Ce modèle suggère que pour que des espèces étroitement liées coexistent en sympatrie secondaire, elles doivent accumuler des différences dans les traits qui contribuent à l'isolement écologique ou reproductif. Ici, nous avons caractérisé la divergence inter‐ et intra‐spécifique chez trois espèces de grenouilles arboricoles géantes dont les distributions s'étendent à travers l'Afrique de l'Ouest et Centrale. Avec des données génétiques, nous avons démontré que la divergence au niveau des espèces coïncide temporellement et géographiquement avec une période de fragmentation forestière à la fin du Pliocène. Nos modèles de niches environnementales ont soutenu une histoire dynamique de stabilité climatique, et ont indiqué que les trois espèces occupent des niches environnementales distinctes. Nous avons trouvé une différenciation morphologique modeste parmi les trois espèces mais une divergence significative dans le diamètre du tympan et les cris des mâles. De plus, nous avons confirmé que deux espèces sont présentes en sympatrie secondaire en Afrique Centrale mais n'avons trouvé aucune preuve d'hybridation. Ces résultats soutiennent l'hypothèse que les cycles d'échange génétique et d'isolement à travers l'Afrique de l'Ouest et Centrale ont contribué à une profonde concentration de biodiversité dans la région. De plus, la divergence des traits écologiques et reproducteurs semble avoir joué un rôle important dans le maintien de lignées distinctes. Au niveau intra‐spécifique, nous avons constaté que les refuges climatiques, les gradients de précipitation, les incursions marines et potentiellement les barrières fluviales ont généré une structure phylogéographique pendant le Pléistocène et jusqu'à l'Holocène. Des études examinant la divergence phénotypique et le contact secondaire entre ces populations géographiquement structurées pourraient démontrer comment des barrières biogéographiques à échelle plus petite et plus récentes contribuent à la diversification régionale.
see also the Perspective by Bryan C. Carstens and Shelby P. Moshier
Aim
Species with wide distributions spanning the African Guinean and Congolian rain forests are often composed of genetically distinct populations or cryptic species with geographic distributions ...that mirror the locations of the remaining forest habitats. We used phylogeographic inference and demographic model testing to evaluate diversification models in a widespread rain forest species, the African foam‐nest treefrog Chiromantis rufescens.
Location
Guinean and Congolian rain forests, West and Central Africa.
Taxon
Chiromantis rufescens.
Methods
We collected mitochondrial DNA (mtDNA) and single‐nucleotide polymorphism (SNP) data for 130 samples of C. rufescens. After estimating population structure and inferring species trees using coalescent methods, we tested demographic models to evaluate alternative population divergence histories that varied with respect to gene flow, population size change and periods of isolation and secondary contact. Species distribution models were used to identify the regions of climatic stability that could have served as forest refugia since the last interglacial.
Results
Population structure within C. rufescens resembles the major biogeographic regions of the Guinean and Congolian forests. Coalescent‐based phylogenetic analyses provide strong support for an early divergence between the western Upper Guinean forest and the remaining populations. Demographic inferences support diversification models with gene flow and population size changes even in cases where contemporary populations are currently allopatric, which provides support for forest refugia and barrier models. Species distribution models suggest that forest refugia were available for each of the populations throughout the Pleistocene.
Main conclusions
Considering historical demography is essential for understanding population diversification, especially in complex landscapes such as those found in the Guineo–Congolian forest. Population demographic inferences help connect the patterns of genetic variation to diversification model predictions. The diversification history of C. rufescens was shaped by a variety of processes, including vicariance from river barriers, forest fragmentation and adaptive evolution along environmental gradients.
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