Mating Patterns and Post-Mating Isolation in Three Cryptic Species of the Engystomops Petersi Species Complex

Determining the extent of reproductive isolation in cryptic species with dynamic geographic ranges can yield important insights into the processes that generate and maintain genetic divergence in the absence of severe geographic barriers. We studied mating patterns, propensity to hybridize in nature and subsequent fertilization rates, as well as survival and development of hybrid F1 offspring for three nominal species of the Engystomops petersi species complex in Yasuní National Park, Ecuador. We found at least two species in four out of six locations sampled, and 14.3% of the wild pairs genotyped were mixed-species (heterospecific) crosses. We also found reduced fertilization rates in hybrid crosses between E. petersi females and E. “magnus” males, and between E. “magnus” females and E. “selva” males but not in the reciprocal crosses, suggesting asymmetric reproductive isolation for these species. Larval development times decreased in F1 hybrid crosses compared to same species (conspecific) crosses, but we did not find significant reduction in larval survival or early metamorph survival. Our results show evidence of post-mating isolation for at least two hybrid crosses of the cryptic species we studied. The general decrease in fertilization rates in heterospecific crosses suggests that sexual selection and reinforcement might have not only contributed to the pattern of call variation and behavioral isolation we see between species today, but they may also contribute to further signal divergence and behavioral evolution, especially in locations where hybridization is common and fertilization success is diminished

Mating Patterns and Post-Mating Isolation in Three Cryptic Species of the Engystomops Petersi Species Complex

Determining the extent of reproductive isolation in cryptic species with dynamic geographic ranges can yield important insights into the processes that generate and maintain genetic divergence in the absence of severe geographic barriers. We studied mating patterns, propensity to hybridize in nature and subsequent fertilization rates, as well as survival and development of hybrid F1 offspring for three nominal species of the Engystomops petersi species complex in Yasuní National Park, Ecuador. We found at least two species in four out of six locations sampled, and 14.3% of the wild pairs genotyped were mixed-species (heterospecific) crosses. We also found reduced fertilization rates in hybrid crosses between E. petersi females and E. “magnus” males, and between E. “magnus” females and E. “selva” males but not in the reciprocal crosses, suggesting asymmetric reproductive isolation for these species. Larval development times decreased in F1 hybrid crosses compared to same species (conspecific) crosses, but we did not find significant reduction in larval survival or early metamorph survival. Our results show evidence of post-mating isolation for at least two hybrid crosses of the cryptic species we studied. The general decrease in fertilization rates in heterospecific crosses suggests that sexual selection and reinforcement might have not only contributed to the pattern of call variation and behavioral isolation we see between species today, but they may also contribute to further signal divergence and behavioral evolution, especially in locations where hybridization is common and fertilization success is diminished

The Health Impacts of Eviction: Evidence from the National Longitudinal Study of Adolescent to Adult Health

Eviction represents an urgent social and economic issue in the United States, with nearly two million evictions occurring annually in the U.S. Still, the population health impacts of evictions, as well as the pathways linking eviction to health, are not well documented or understood, particularly among young adults. Using nationally-representative, longitudinal data from the National Longitudinal Study of Adolescent to Adult Health (1994-2008) (n=9,029), the present study uses a combination of analytic methods—including prospective lagged dependent variable regression models, inverse probabilities of treatment weighting, longitudinal first difference models, causal mediation techniques—to comprehensively assess whether and how evictions relate to depressive risk and self-rated health across early adulthood, paying particular attention to the stress-related pathways linking eviction and health. Results provide robust evidence of positive longitudinal associations between eviction and depressive risk, in particular. In the prospective regression models, young adults who experienced recent eviction had more depressive symptoms and worse self-rated health than those who were not evicted, net a host of background characteristics. Using treatment weighting techniques, results showed that young adults who experienced eviction had more depressive symptoms than those who were not evicted (5.921 vs. 4.998 depressive symptoms, p=0.003). Perceived social stress mediated nearly 18 percent of the associations between eviction and the depressive symptoms (p\u3c0.001). In the first difference models, young people who experienced eviction between survey waves experienced greater increases in depressive symptoms over time compared to those who were not evicted, net of changes in other indicators of socioeconomic status and residential instability. Taken together, our results suggest that the recent surges in evictions in the U.S. serve as a potent threat to population health during the emerging adult period, with especially devastating consequences for low-income individuals and communities of color

A heparin binding synthetic peptide from human HIP / RPL29 fails to specifically differentiate between anticoagulantly active and inactive species of heparin

Despite extensive progress in determining structures within heparin and heparan sulfate (Hp/HS) and the discovery of numerous proteinaceous binding partners for Hp/HS so far; the only detailed characterization of a specific protein-glycosaminoglycan interaction is antithrombin III (ATIII) binding to a Hp pentasaccharide containing a unique 3-O-sulfated glucosamine residue. Previously, it was reported from our laboratories that a 16 amino acid synthetic peptide derived from the C-terminus of human HIP/RPL29 (HIP peptide-1) enriched for ATIII-dependent anticoagulant activity, presumably by specifically binding the ATIII pentasaccharide. Herein, we demonstrate that HIP peptide-1 cannot enrich ATIII-dependent anticoagulant activity from a starting pool of porcine intestinal mucosa Hp through a bio-specific interaction. However, a HIP peptide-1 column can be used to enrich for anticoagulantly active Hp from a diverse pool of glycosaminoglycans known as Hp byproducts by a mechanism of nonspecific charge interactions. Thus, HIP peptide-1 cannot recognize Hp via bio-specific interactions but binds glycosaminoglycans by non-specific charge interactions

A Leucine-enriched Diet Enhances Overload-induced Growth and Markers of Protein Synthesis in Aged Rat Skeletal Muscle

Introduction: The hypertrophic response to overload in fast-twitch skeletal muscle is impaired in aged humans and rats, and impaired protein synthesis pathway activation is hypothesized to be a contributing factor. Muscle growth occurs when protein synthesis exceeds protein degradation. Dietary supplementation of the essential amino acid leucine has been shown to enhance protein synthesis in both young and aged skeletal muscle. Leucine acts in part by activating mammalian target of rapamycin (mTOR; a key upstream regulator of protein synthesis pathways) as well as by attenuating the activation of 5\u27-AMP-activated protein kinase (AMPK; a negative regulator of mTOR and protein synthesis). During the aging process, AMPK Thr172 phosphorylation (and thus its activation) is increased, purportedly inhibiting gains in muscle mass and strength. Although dietary leucine supplementation has been shown to enhance strength gains in response to resistance training in young humans, the potential for leucine supplementation to enhance overload-induced muscle hypertrophy in aged humans or animal models has not been examined. Thus, the aim of this study was to determine whether dietary leucine supplementation can enhance markers of protein synthesis and rescue hypertrophy in overloaded fast-twitch skeletal muscles of aged rats to levels comparable to their younger counterparts. It was hypothesized that dietary leucine supplementation during 7 days of fast-twitch plantaris muscle overload would enhance plantaris muscle hypertrophy in aged rats to levels observed in young adult rats not receiving leucine. It was also hypothesized that dietary leucine supplementation during the overload period would suppress AMPK phosphorylation and enhance markers of protein synthesis [70 kDa ribosomal protein S6 kinase (p70S6k), ribosomal protein S6 (rpS6), and eukaryotic elongation factor 2 (eEF2)] in the overloaded fast-twitch plantaris muscles of the aged rats to levels observed in young adult rats not receiving leucine. Methods: Young adult (8 mo.) and old (33 mo.) male Fisher 344 x Brown Norway F1 Hybrid (FBN) rats underwent a 1-week unilateral overload of the fast-twitch plantaris muscles via tenotomy of the synergistic gastrocnemius muscle. Within each age group, animals were matched for body weight and separated into either a dietary leucine supplementation group (normal rat chow supplemented by an additional 5% leucine content in place of 5% of the carbohydrate content; n = 7/age group) or placebo group (normal rat chow; n = 6/age group). The leucine groups started the leucine-enriched diet 2 days prior to, and throughout, the overload intervention. All animals had ad libitum access to water and chow during the entire experiment; no differences in daily calorie consumption were observed between the placebo vs. leucine groups within each age group. At the end of the overload period, sham-operated and overloaded plantaris muscles were harvested and analyzed via western blotting for the phosphorylations of AMPK, p70S6k, rpS6, and eEF2. A 2x2x2 ANOVA with repeated measures was used for analyses of the effects of age, dietary intervention, and overload (the repeated measure) on muscle hypertrophy. A 2x2 ANOVA was used to measure the percent changes in hypertrophy and western blot analyses. Post-hoc comparisons were accomplished via a Fisher\u27s Least Significant Difference test, with statistical significance being set at p ≤ 0.05. Results: Dietary leucine enrichment significantly (p ≤ 0.05) enhanced overload-induced fast-twitch plantaris muscle hypertrophy in old, but not in young adult, animals. A similar effect was also observed in the slow-twitch soleus muscles, but western blotting analyses are only presented for the fast-twitch plantaris muscles. Sham and overloaded plantaris muscle AMPK phosphorylation (Thr172) was significantly higher in aged animals receiving normal chow compared to young adult animals; however, leucine supplementation in old animals reduced this AMPK phosphorylation to levels similar to young adult animals. Phospho-p70S6k (Thr389) and phospho-rpS6 (Ser235/Ser236) were significantly lower in old vs. young overloaded muscles under placebo conditions, but leucine partially restored both p70S6k and rpS6 phosphorylations in old overloaded muscles to that of young adult overloaded muscles. Overload significantly increased total eEF2 content and decreased inhibitory eEF2 phosphorylation (Thr56; normalized to total eEF2) in young adult muscles regardless of leucine supplementation. Total eEF2 content was unaffected by overload in old placebo muscles, but leucine supplementation in old animals non-significantly (p = 0.09) restored the overload-induced increase in total eEF2 content. Muscle eEF2 phosphorylation was unaffected by overload or leucine supplementation in old animals. Discussion: These novel findings indicate that a leucine-enriched diet may potentially enhance overload-induced growth of aged fast-twitch muscle, in part by enhancing pathways known to stimulate protein synthesis. This is in accord with previous findings of leucine’s stimulating effect on protein synthesis in both young adult and aged skeletal muscle under resting conditions. The fact that leucine supplementation enhanced overload-induced hypertrophy only in the old (and not the young) animals may reflect the high growth stimulus of the chronic overload model. That is, the balance of protein synthesis/degradation rates under such a large chronic growth stimulus may not be the limiting factor in young animals, in which muscle growth is not impaired (i.e., synthesis/degradation rates may reach futile levels, and another factor such as sarcomere assembly may be limiting). However, the impaired balance of protein synthesis/degradation rates may be the limiting factor to growth in aged muscle, and leucine may correct this imbalance to restore muscle growth to levels observed in young animals

A Leucine-enriched Diet Enhances Overload-induced Growth and Suppresses Markers of Protein Degradation in Aged Rat Skeletal Muscle

Introduction: The hypertrophic response to overload in fast-twitch skeletal muscle is impaired in aged humans and rats, and upregulation of protein degradation pathways are hypothesized to be a contributing factor. Muscle growth occurs when protein synthesis is greater than protein degradation. Dietary supplementation of the essential amino acid leucine has been shown to reduce protein degradation in both young and aged skeletal muscle. Specifically, leucine acts in part by attenuating 5\u27-AMP-activated protein kinase (AMPK) activation as well as the translocation of the forkhead box transcription factor 3A (FoxO3, known to promote transcription of mRNAs encoding degradation pathway proteins) to the nucleus. Akt (a promoter of muscle growth) prevents translocation of FoxO3 into the nucleus by phosphorylating FoxO3 phosphorylation at Ser318/321. However, AMPK, inhibits Akt\u27s phosphorylation of FoxO3, allowing it to enter the nucleus and increase transcription of protein degradation pathway genes encoding ubiquitin ligase proteins such as muscle RING finger 1 (MuRF1) and muscle atrophy F-box (MAFbx, or Atrogin-1). During the aging process, AMPK Thr172 phosphorylation (and thus its activation) is increased, purportedly inhibiting gains in muscle mass and strength. Although dietary leucine supplementation has been shown to enhance strength gians in response to resistance training in young humans, the potential for leucine supplementation to enhance overload-induced muscle hypertrophy in aged humans or animal models has not been examined. Thus, the aim of this study was to determine whether dietary leucine supplementation can attenuate markers of protein degradation and rescue hypertrophy during overload in the fast-twitch skeletal muscles of aged rats to levels comparable to their younger counterparts. It was hypothesized that dietary leucine supplementation during 7 days of fast-twitch plantaris muscle overload would enhance plantaris muscle hypertrophy in aged rats to levels observed in young adult rats not receiving leucine. It was also hypothesized that dietary leucine supplementation during the overload period would alter markers of protein degradation (enhance FoxO3 phosphorylation and reduce the levels of AMPK phosphorylation, Atrogin-1 protein content, and MuRF1 protein content) in the overloaded fast-twitch plantaris muscles of the aged rats to levels observed in young adult rats not receiving leucine. Methods: Young adult (8 mo.) and old (33 mo.) male Fisher 344 x Brown Norway F1 Hybrid (FBN) rats underwent a 1-week unilateral overload of the fast-twitch plantaris muscles via tenotomy of the synergistic gastrocnemius muscle. Within each age group, animals were matched for body weight and separated into either a dietary leucine supplementation group (normal rat chow supplemented by an additional 5% leucine content in place of 5% of the carbohydrate content; n = 7/age group) or placebo group (normal rat chow; n = 6/age group). The leucine groups started the leucine-enriched diet 2 days prior to, and throughout, the overload intervention. All animals had ad libitum access to water and chow during the entire experiment; no differences in daily calorie consumption were observed between the placebo vs. leucine groups within each age group. At the end of the overload period, sham-operated and overloaded plantaris muscles were harvested and analyzed via western blotting for the phosphorylations of AMPK and FoxO3 as well as total levels of Atrogin-1 and MuRF1. A 2x2x2 ANOVA with repeated measures was used for analyses of the effects of age, dietary intervention, and overload (the repeated measure) on muscle hypertrophy. A 2x2 ANOVA was used to measure the percent changes in hypertrophy and western blot analyses. Post-hoc comparisons were accomplished via a Fisher\u27s Least Significant Difference test, with statistical significance being set at p ≤ 0.05. Results: Dietary leucine enrichment significantly (p ≤ 0.05) enhanced overload-induced fast-twitch plantaris muscle hypertrophy in old, but not in young adult, animals. A similar effect was also observed in the slow-twitch soleus muscles, but western blotting analyses are only presented for the fast-twitch plantaris muscles. Sham and overloaded plantaris muscle AMPK phosphorylation was significantly higher in aged animals receiving normal chow compared to young adult animals; however, leucine supplementation in old animals reduced this AMPK phosphorylation to levels similar to young adult animals. Compared to placebo, leucine also non-significantly (p = 0.07) enhanced FoxO3 phosphorylation in the overloaded muscles of both young adult and old animals (thus theoretically reducing FoxO3 translocation to the nucleus). Accordingly, leucine also non-significantly (p = 0.07) reversed the overload-induced increase (from a 22.8% increase to a 17.0% decrease) in Atrogin-1 content in aged muscles and non-significantly (p = 0.14) enhanced the overload-induced decrease in MuRF1 content in the muscles of both age groups. Discussion: These novel findings indicate that a leucine-enriched diet may potentially enhance overload-induced growth of aged fast-twitch muscle, in part by suppressing pathways known to stimulate protein degradation. This is in accord with previous findings of leucine’s suppressive effect on protein degradation in both young adult and aged skeletal muscle under resting conditions. The fact that leucine supplementation enhanced overload-induced hypertrophy only in the old (and not the young) animals may reflect the high growth stimulus of the chronic overload model. That is, the balance of protein synthesis/degradation rates under such a large chronic growth stimulus may not be the limiting factor in young animals, in which muscle growth is not impaired (i.e., synthesis/degradation rates may reach futile levels, and another factor such as sarcomere assembly may be limiting). However, the impaired balance of protein synthesis/degradation rates may be the limiting factor to growth in aged muscle, and leucine may correct this imbalance to restore muscle growth to levels observed in young animals

Numerical Analysis of a Pulse Detonation Cross Flow Heat Load Experiment

A comparison between experimentally measured and numerically simulated, time-averaged, point heat transfer rates in a pulse detonation (PDE) engine is presented. The comparison includes measurements and calculations for heat transfer to a cylinder in crossflow and to the tube wall itself using a novel spool design. Measurements are obtained at several locations and under several operating conditions. The measured and computed results are shown to be in substantial agreement, thereby validating the modeling approach. The model, which is based in computational fluid dynamics (CFD) is then used to interpret the results. A preheating of the incoming fuel charge is predicted, which results in increased volumetric flow and subsequent overfilling. The effect is validated with additional measurements

The European Climate Research Alliance (ECRA): collaboration from bottom-up

The European Climate Research Alliance (ECRA) is an association of leading European research institutions in the field of climate research (http://www.ecra-climate.eu/, last access: 6 December 2018). ECRA is a bottom-up initiative and helps to facilitate the development of climate change research, combining the capacities of national research institutions, and inducing closer ties between existing national research initiatives, projects and infrastructures. ECRA works as an open platform to bring together climate researchers, providing excellent scientific expertise for policy makers and of societal relevance. The ECRA Board consists of representatives of ECRA partners and decides on governance, scientific priorities, and organisational matters. Currently organized into four Collaborative Programmes, climate scientists share their knowledge, experience and expertise to identify the most important research requirements for the future, thus developing a foresight approach. The CPs cover the topics: (1) Arctic variability and change, (2) Sea level changes and coastal impacts, (3) Changes in the hydrological cycle and (4) High impact events. The CP activities are planned in workshops and participation is open to all interested scientists from the relevant research fields. In particular, young researchers are actively encouraged to join the network. Each CP develops its joint research priorities for shaping European research into the future. Because scientific themes are interconnected, the four Collaborative Programmes interact with each other, e.g. through the organization of common workshops or joint applications. In addition, the Collaborative Programme leads attend the Board meetings. The different formats of ECRA meetings range from scientific workshops to briefing events and side events at conferences to involve different groups of interests. This facilitates the interaction of scientists, various stakeholder groups and politicians. A biennial open ECRA General Assembly that is organised in Brussels represents an umbrella event and acts as a platform for discussion and contact with stakeholders. This event is an excellent opportunity to jointly discuss research priorities of high societal relevance

Comparison of Numerically Simulated and Experimentally Measured Performance of a Rotating Detonation Engine

A quasi-two-dimensional, computational fluid dynamic (CFD) simulation of a rotating detonation engine (RDE) is described. The simulation operates in the detonation frame of reference and utilizes a relatively coarse grid such that only the essential primary flow field structure is captured. This construction and other simplifications yield rapidly converging, steady solutions. Viscous effects, and heat transfer effects are modeled using source terms. The effects of potential inlet flow reversals are modeled using boundary conditions. Results from the simulation are compared to measured data from an experimental RDE rig with a converging-diverging nozzle added. The comparison is favorable for the two operating points examined. The utility of the code as a performance optimization tool and a diagnostic tool are discussed

Multihospital Infection Prevention Collaborative: Informatics Challenges and Strategies to Prevent MRSA

We formed a collaborative to spread effective MRSA prevention strategies. We conducted a two-phase, multisite, quasi-experimental study of seven hospital systems (11 hospitals) in IN, MT, ME and Ontario, Canada over six years. Patients with prior MRSA were identified at admission using regional health information exchange data. We developed a system to return an alert message indicating a prior history of MRSA, directed to infection preventionists and admissions. Alerts indicated the prior anatomic site, and the originating institution. The combined approach of training and coaching, implementation of MRSA registries, notifying hospitals on admission of previously infected or colonized patients, and change strategies was effective in reducing MRSA infections over 80%. Further research and development of electronic surveillance tools is needed to better integrate the varied data source and support preventing MRSA infections. Our study supports the importance of hospitals collaborating to share data and implement effective strategies to prevent MRSA