Tropical forests are approaching critical temperature thresholds.

The critical temperature beyond which photosynthetic machinery in tropical trees begins to fail averages approximately 46.7 °C (Tcrit)1. However, it remains unclear whether leaf temperatures experienced by tropical vegetation approach this threshold or soon will under climate change. Here we found that pantropical canopy temperatures independently triangulated from individual leaf thermocouples, pyrgeometers and remote sensing (ECOSTRESS) have midday peak temperatures of approximately 34 °C during dry periods, with a long high-temperature tail that can exceed 40 °C. Leaf thermocouple data from multiple sites across the tropics suggest that even within pixels of moderate temperatures, upper canopy leaves exceed Tcrit 0.01% of the time. Furthermore, upper canopy leaf warming experiments (+2, 3 and 4 °C in Brazil, Puerto Rico and Australia, respectively) increased leaf temperatures non-linearly, with peak leaf temperatures exceeding Tcrit 1.3% of the time (11% for more than 43.5 °C, and 0.3% for more than 49.9 °C). Using an empirical model incorporating these dynamics (validated with warming experiment data), we found that tropical forests can withstand up to a 3.9 ± 0.5 °C increase in air temperatures before a potential tipping point in metabolic function, but remaining uncertainty in the plasticity and range of Tcrit in tropical trees and the effect of leaf death on tree death could drastically change this prediction. The 4.0 °C estimate is within the 'worst-case scenario' (representative concentration pathway (RCP) 8.5) of climate change predictions2 for tropical forests and therefore it is still within our power to decide (for example, by not taking the RCP 6.0 or 8.5 route) the fate of these critical realms of carbon, water and biodiversity3,4.

Toward a coordinated understanding of hydro-biogeochemical root functions in tropical forests for application in vegetation models.

Tropical forest root characteristics and resource acquisition strategies are underrepresented in vegetation and global models, hampering the prediction of forest-climate feedbacks for these carbon-rich ecosystems. Lowland tropical forests often have globally unique combinations of high taxonomic and functional biodiversity, rainfall seasonality, and strongly weathered infertile soils, giving rise to distinct patterns in root traits and functions compared with higher latitude ecosystems. We provide a roadmap for integrating recent advances in our understanding of tropical forest belowground function into vegetation models, focusing on water and nutrient acquisition. We offer comparisons of recent advances in empirical and model understanding of root characteristics that represent important functional processes in tropical forests. We focus on: (1) fine-root strategies for soil resource exploration, (2) coupling and trade-offs in fine-root water vs nutrient acquisition, and (3) aboveground-belowground linkages in plant resource acquisition and use. We suggest avenues for representing these extremely diverse plant communities in computationally manageable and ecologically meaningful groups in models for linked aboveground-belowground hydro-nutrient functions. Tropical forests are undergoing warming, shifting rainfall regimes, and exacerbation of soil nutrient scarcity caused by elevated atmospheric CO2. The accurate model representation of tropical forest functions is crucial for understanding the interactions of this biome with the climate.

Las características de las raíces de los bosques tropicales y las estrategias de adquisición de recursos están subrepresentadas en modelos de vegetación, lo que dificulta la predicción del efecto de cambio de clima para estos ecosistemas ricos en carbono. Los bosques tropicales a menudo tienen combinaciones únicas a nivel mundial de alta biodiversidad taxonómica y funcional, estacionalidad de precipitación, y suelos infértiles, dando lugar a patrones distintos en los rasgos y funciones de las raíces en comparación con los ecosistemas de latitudes más altas. Integramos los avances recientes en nuestra comprensión de la función subterránea de los bosques tropicales en modelos de vegetación, centrándonos en la adquisición de agua y nutrientes. Ofrecemos comparaciones de avances recientes en la comprensión empírica y de modelos de las características de las raíces que representan procesos funcionales importantes en los bosques tropicales. Nos centramos en: (1) estrategias de raíces finas para adquisición de recursos del suelo, (2) acoplamiento y compensaciones entre adquisición del agua y de nutrientes, y (3) vínculos entre funciones sobre tierra y debajo del superficie en bosques tropicales. Sugerimos vías para representar estas comunidades de plantas extremadamente diversas en grupos computacionalmente manejables y ecológicamente significativos en modelos. Los bosques tropicales se están calentando, tienen cambios en los regímenes de lluvias, y tienen una exacerbación de la escasez de nutrientes del suelo causada por el elevado CO2 atmosférico. La representación precisa de las funciones de los bosques tropicales en modelos es crucial para comprender las interacciones de este bioma con el clima.

Thermography captures the differential sensitivity of dryland functional types to changes in rainfall event timing and magnitude.

Drylands of the southwestern United States are rapidly warming, and rainfall is becoming less frequent and more intense, with major yet poorly understood implications for ecosystem structure and function. Thermography-based estimates of plant temperature can be integrated with air temperature to infer changes in plant physiology and response to climate change. However, very few studies have evaluated plant temperature dynamics at high spatiotemporal resolution in rainfall pulse-driven dryland ecosystems. We address this gap by incorporating high-frequency thermal imaging into a field-based precipitation manipulation experiment in a semi-arid grassland to investigate the impacts of rainfall temporal repackaging. All other factors held constant, we found that fewer/larger precipitation events led to cooler plant temperatures (1.4°C) compared to that of many/smaller precipitation events. Perennials, in particular, were 2.5°C cooler than annuals under the fewest/largest treatment. We show these patterns were driven by: increased and consistent soil moisture availability in the deeper soil layers in the fewest/largest treatment; and deeper roots of perennials providing access to deeper plant available water. Our findings highlight the potential for high spatiotemporal resolution thermography to quantify the differential sensitivity of plant functional groups to soil water availability. Detecting these sensitivities is vital to understanding the ecohydrological implications of hydroclimate change.

Environment and shipping drive environmental DNA beta-diversity among commercial ports.

The spread of nonindigenous species by shipping is a large and growing global problem that harms coastal ecosystems and economies and may blur coastal biogeographical patterns. This study coupled eukaryotic environmental DNA (eDNA) metabarcoding with dissimilarity regression to test the hypothesis that ship-borne species spread homogenizes port communities. We first collected and metabarcoded water samples from ports in Europe, Asia, Australia and the Americas. We then calculated community dissimilarities between port pairs and tested for effects of environmental dissimilarity, biogeographical region and four alternative measures of ship-borne species transport risk. We predicted that higher shipping between ports would decrease community dissimilarity, that the effect of shipping would be small compared to that of environment dissimilarity and shared biogeography, and that more complex shipping risk metrics (which account for ballast water and stepping-stone spread) would perform better. Consistent with our hypotheses, community dissimilarities increased significantly with environmental dissimilarity and, to a lesser extent, decreased with ship-borne species transport risks, particularly if the ports had similar environments and stepping-stone risks were considered. Unexpectedly, we found no clear effect of shared biogeography, and that risk metrics incorporating estimates of ballast discharge did not offer more explanatory power than simpler traffic-based risks. Overall, we found that shipping homogenizes eukaryotic communities between ports in predictable ways, which could inform improvements in invasive species policy and management. We demonstrated the usefulness of eDNA metabarcoding and dissimilarity regression for disentangling the drivers of large-scale biodiversity patterns. We conclude by outlining logistical considerations and recommendations for future studies using this approach.

Global patterns of drought recovery.

Drought, a recurring phenomenon with major impacts on both human and natural systems, is the most widespread climatic extreme that negatively affects the land carbon sink. Although twentieth-century trends in drought regimes are ambiguous, across many regions more frequent and severe droughts are expected in the twenty-first century. Recovery time-how long an ecosystem requires to revert to its pre-drought functional state-is a critical metric of drought impact. Yet the factors influencing drought recovery and its spatiotemporal patterns at the global scale are largely unknown. Here we analyse three independent datasets of gross primary productivity and show that, across diverse ecosystems, drought recovery times are strongly associated with climate and carbon cycle dynamics, with biodiversity and CO2 fertilization as secondary factors. Our analysis also provides two key insights into the spatiotemporal patterns of drought recovery time: first, that recovery is longest in the tropics and high northern latitudes (both vulnerable areas of Earth's climate system) and second, that drought impacts (assessed using the area of ecosystems actively recovering and time to recovery) have increased over the twentieth century. If droughts become more frequent, as expected, the time between droughts may become shorter than drought recovery time, leading to permanently damaged ecosystems and widespread degradation of the land carbon sink.

Blood oxidative stress biomarkers in women: influence of oral contraception, exercise, and N-acetylcysteine.

PURPOSE: To compare physiological responses to submaximal cycling and sprint cycling performance in women using oral contraceptives (WomenOC) and naturally cycling women (WomenNC) and to determine whether N-acetylcysteine (NAC) supplementation mediates these responses. METHODS: Twenty recreationally trained women completed five exercise trials (i.e., an incremental cycling test, a familiarisation trial, a baseline performance trial and two double-blind crossover intervention trials). During the intervention trials participants supplemented with NAC or a placebo 1 h before exercise. Cardiopulmonary parameters and blood biochemistry were assessed during 40 min of fixed-intensity cycling at 105% of gas-exchange threshold and after 1-km cycling time-trial. RESULTS: WomenOC had higher ventilation (ß [95% CI] = 0.07 L·min-1 [0.01, 0.14]), malondialdehydes (ß = 12.00 mmol·L-1 [6.82, 17.17]) and C-reactive protein (1.53 mg·L-1 [0.76, 2.30]), whereas glutathione peroxidase was lower (ß =  22.62 mU·mL-1 [- 41.32, - 3.91]) compared to WomenNC during fixed-intensity cycling. Plasma thiols were higher at all timepoints after NAC ingestion compared to placebo, irrespective of group (all p < 0.001; d = 1.45 to 2.34). For WomenNC but not WomenOC, the exercise-induced increase in malondialdehyde observed in the placebo trial was blunted after NAC ingestion, with lower values at 40 min (p = 0.018; d = 0.73). NAC did not affect cycling time-trial performance. CONCLUSIONS: Blood biomarkers relating to oxidative stress and inflammation are elevated in WomenOC during exercise. There may be an increased strain on the endogenous antioxidant system during exercise, since NAC supplementation in WomenOC did not dampen the exercise-induced increase in malondialdehyde. Future investigations should explore the impact of elevated oxidative stress on exercise adaptations or recovery from exercise in WomenOC.

Characteristics and outcomes of acute COVID-19 infection in paediatric and young adult patients with underlying cardiac disease.

OBJECTIVE: To describe outcomes of acute coronavirus disease 2019 in paediatric and young adult patients with underlying cardiac disease and evaluate the association between cardiac risk factors and hospitalisation. STUDY DESIGN: We conducted a retrospective single-institution review of patients with known cardiac disease and positive severe acute respiratory syndrome coronavirus 2 RT-PCR from 1 March, 2020 to 30 November, 2020. Extracardiac comorbidities and cardiac risk factors were compared between those admitted for coronavirus disease 2019 illness and the rest of the cohort using univariate analysis. RESULTS: Forty-two patients with a mean age of 7.7 ± 6.7 years were identified. Six were 18 years of age or more with the oldest being 22 years of age. Seventy-six percent were Hispanic. The most common cardiac diagnoses were repaired cyanotic (n = 7, 16.6%) and palliated single ventricle (n = 7, 16.6%) congenital heart disease. Fourteen patients (33.3%) had underlying syndromes or chromosomal anomalies, nine (21%) had chronic pulmonary disease and eight (19%) were immunosuppressed. Nineteen patients (47.6%) reported no symptoms. Sixteen (38.1%) reported only mild symptoms. Six patients (14.3%) were admitted to the hospital for acute coronavirus disease 2019 illness. Noncardiac comorbidities were associated with an increased risk of hospitalisation (p = 0.02), particularly chronic pulmonary disease (p = 0.01) and baseline supplemental oxygen requirement (p = 0.007). None of the single ventricle patients who tested positive required admission. CONCLUSIONS: Hospitalisations for coronavirus disease 2019 were rare among children and young adults with underlying cardiac disease. Extracardiac comorbidities like pulmonary disease were associated with increased risk of hospitalisation while cardiac risk factors were not.

Mitochondrial dysfunction in placental trophoblast cells experiencing gestational diabetes mellitus.

KEY POINTS: Mitochondrial dysfunction is known to occur in diabetic phenotypes including type 1 and 2 diabetes mellitus. The incidence of gestational diabetes mellitus (GDM) is increasing and defined as the onset of a diabetic phenotype during pregnancy. The role of placental mitochondria in the aetiology of GDM remains unclear and is an emerging area of research. Differing mitochondrial morphologies within the placenta may influence the pathogenesis of the disorder. This study observed mitochondrial dysfunction in GDM placenta when assessing whole tissue. Upon further investigation into mitochondrial isolates from the cytotrophoblast and syncytiotrophoblast, mitochondrial dysfunction appears exaggerated in syncytiotrophoblast. Assessing mitochondrial populations individually enabled the determination of differences between cell lineages of the placenta and established varying levels of mitochondrial dysfunction in GDM, in some instances establishing significance in pathways previously inconclusive or confounded when assessing whole tissue. This research lays the foundation for future work into mitochondrial dysfunction in the placenta and the role it may play in the aetiology of GDM. ABSTRACT: Mitochondrial dysfunction has been associated with diabetic phenotypes, yet the involvement of placental mitochondria in gestational diabetes mellitus (GDM) remains inconclusive. This is in part complicated by the different mitochondrial subpopulations present in the two major trophoblast cell lineages of the placenta. To better elucidate the role of mitochondria in this pathology, this study examined key aspects of mitochondrial function in placentas from healthy pregnancies and those complicated by GDM in both whole tissue and isolated mitochondria. Mitochondrial content, citrate synthase activity, reactive oxygen species production and gene expression regulating metabolic, hormonal and antioxidant control was examined in placental tissue, before examining functional differences between mitochondrial isolates from cytotrophoblast (Cyto-Mito) and syncytiotrophoblast (Syncytio-Mito). Our study observed evidence of mitochondrial dysfunction across multiple pathways when assessing whole placental tissue from GDM pregnancies compared with healthy controls. Furthermore, by examining isolated mitochondria from the cytotrophoblast and syncytiotrophoblast cell lineages of the placenta we established that although both mitochondrial populations were dysfunctional, they were differentially impacted. These data highlight the need to consider changes in mitochondrial subpopulations at the feto-maternal interface when studying pregnancy pathologies.

Root-derived inputs are major contributors to soil carbon in temperate forests, but vary by mycorrhizal type.

Roots promote the formation of slow-cycling soil carbon (C), yet we have a limited understanding of the magnitude and controls on this flux. We hypothesised arbuscular mycorrhizal (AM)- and ectomycorrhizal (ECM)-associated trees would exhibit differences in root-derived C accumulation in the soil, and that much of this C would be transferred into mineral-associated pools. We installed δ13 C-enriched ingrowth cores across mycorrhizal gradients in six Eastern U.S. forests (n = 54 plots). Overall, root-derived C was 54% greater in AM versus ECM-dominated plots. This resulted in nearly twice as much root-derived C in putatively slow-cycling mineral-associated pools in AM compared to ECM plots. Given that our estimates of root-derived inputs were often equal to or greater than leaf litter inputs, our results suggest that variation in root-derived soil C accumulation due to tree mycorrhizal dominance may be a key control of soil C dynamics in forests.

Integrating the evidence for a terrestrial carbon sink caused by increasing atmospheric CO2.

Atmospheric carbon dioxide concentration ([CO2 ]) is increasing, which increases leaf-scale photosynthesis and intrinsic water-use efficiency. These direct responses have the potential to increase plant growth, vegetation biomass, and soil organic matter; transferring carbon from the atmosphere into terrestrial ecosystems (a carbon sink). A substantial global terrestrial carbon sink would slow the rate of [CO2 ] increase and thus climate change. However, ecosystem CO2 responses are complex or confounded by concurrent changes in multiple agents of global change and evidence for a [CO2 ]-driven terrestrial carbon sink can appear contradictory. Here we synthesize theory and broad, multidisciplinary evidence for the effects of increasing [CO2 ] (iCO2 ) on the global terrestrial carbon sink. Evidence suggests a substantial increase in global photosynthesis since pre-industrial times. Established theory, supported by experiments, indicates that iCO2 is likely responsible for about half of the increase. Global carbon budgeting, atmospheric data, and forest inventories indicate a historical carbon sink, and these apparent iCO2 responses are high in comparison to experiments and predictions from theory. Plant mortality and soil carbon iCO2 responses are highly uncertain. In conclusion, a range of evidence supports a positive terrestrial carbon sink in response to iCO2 , albeit with uncertain magnitude and strong suggestion of a role for additional agents of global change.

Circulating trace elements for the prediction of preeclampsia and small for gestational age babies.

INTRODUCTION: Poor gestational outcomes due to placental insufficiency can have lifelong consequences for mother and child. OBJECTIVE: There is a need for better methods of diagnosis, and elemental metabolomics may provide a means to determine the risk of gestational disorders. METHODS: This study used blood plasma samples collected at 36 weeks' gestation from women who later developed preeclampsia (n = 38), or small-for-gestational age babies (n = 91), along with matched controls (n = 193). Multi-element analysis was conducted by inductively coupled plasma mass spectrometer (ICP-MS), allowing simultaneous measurement of 28 elements. RESULTS: Women who later developed PE, exhibited significantly increased concentrations of K, Rb and Ba. For SGA pregnancies, there was a significant increase in Cu and a decrease in As concentrations. Despite significant differences in single elements, the elemental profile of groups indicated no clustering of control, PE, or SGA samples. Positive predicative values correctly identified approximately 60% of SGA and 70% of PE samples. CONCLUSION: This is the first-time elemental metabolomics has been used to predict SGA and PE at 36 weeks. Though significant changes were identified, routine clinical use may be limited but may contribute to a multi marker test. Future analysis should include other biomarkers, metabolic data or clinical measurements made throughout gestation.

Beyond ecosystem modeling: A roadmap to community cyberinfrastructure for ecological data-model integration.

In an era of rapid global change, our ability to understand and predict Earth's natural systems is lagging behind our ability to monitor and measure changes in the biosphere. Bottlenecks to informing models with observations have reduced our capacity to fully exploit the growing volume and variety of available data. Here, we take a critical look at the information infrastructure that connects ecosystem modeling and measurement efforts, and propose a roadmap to community cyberinfrastructure development that can reduce the divisions between empirical research and modeling and accelerate the pace of discovery. A new era of data-model integration requires investment in accessible, scalable, and transparent tools that integrate the expertise of the whole community, including both modelers and empiricists. This roadmap focuses on five key opportunities for community tools: the underlying foundations of community cyberinfrastructure; data ingest; calibration of models to data; model-data benchmarking; and data assimilation and ecological forecasting. This community-driven approach is a key to meeting the pressing needs of science and society in the 21st century.

Temporal changes in blood oxidative stress biomarkers across the menstrual cycle and with oral contraceptive use in active women.

PURPOSE: To examine the temporal changes in blood oxidative stress biomarkers in recreationally-trained women that were naturally-cycling (WomenNC) or using oral contraceptives (WomenOC) across one month. METHODS: Blood samples were acquired at three timepoints of the menstrual cycle (1: early-follicular, 2: late-follicular and 3: mid-luteal) and oral contraceptive packet (1: InactiveOC, 2: Mid-activeOC and 3: Late-activeOC) for determination of estradiol, progesterone, oxidative stress, C-reactive protein (CRP) and other cardiometabolic biomarkers in plasma and serum. RESULTS: There was a Group by Time effect on estradiol (p < 0.001, partial η2 = 0.64) and progesterone (p < 0.001, partial η2 = 0.77). Malondialdehyde, lipid hydroperoxides and CRP concentrations were higher in WomenOC during Late-activeOC compared to InactiveOC (+ 96%, + 23% and + 104%, respectively, p < 0.05). However, there were no changes in these biomarkers across the menstrual cycle in WomenNC (p > 0.05). At all timepoints (i.e., 1, 2 and 3), WomenOC had elevated lipid hydroperoxides (+ 28, + 48% and + 50%) and CRP (+ 71%, + 117% and + 130%) compared to WomenNC (p < 0.05, partial η2 > 0.25). There was no Group by Time effect on non-enzymatic antioxidants or glutathione peroxidase; however, glutathione peroxidase was lower in WomenOC, i.e., main effect of group (p < 0.05, partial η2 > 0.20). CONCLUSION: These findings demonstrate that WomenOC not only have higher oxidative stress and CRP than WomenNC, but also a transient increase across one month of habitual oral contraceptive use. Since changes in oxidative stress and CRP often relate to training stress and recovery, these outcomes may have implications to workload monitoring practices in female athletes.

Mitochondrial transformations in the aging human placenta.

Mitochondria play a key role in homeostasis and are central to one of the leading hypotheses of aging, the free radical theory. Mitochondria function as a reticulated network, constantly adapting to the cellular environment through fusion (joining), biogenesis (formation of new mitochondria), and fission (separation). This adaptive response is particularly important in response to oxidative stress, cellular damage, and aging, when mitochondria are selectively removed through mitophagy, a mitochondrial equivalent of autophagy. During this complex process, mitochondria influence surrounding cell biology and organelles through the release of signaling molecules. Given that the human placenta is a unique organ having a transient and somewhat defined life span of ∼280 days, any adaption or dysfunction associated with mitochondrial physiology as a result of aging will have a dramatic impact on the health and function of both the placenta and the fetus. Additionally, a defective placenta during gestation, resulting in reduced fetal growth, has been shown to influence the development of chronic disease in later life. In this review we focus on the mitochondrial adaptions and transformations that accompany gestational length and share similarities with age-related diseases. In addition, we discuss the role of such changes in regulating placental function throughout gestation, the etiology of gestational complications, and the development of chronic diseases later in life.

Global vegetation biomass production efficiency constrained by models and observations.

Plants use only a fraction of their photosynthetically derived carbon for biomass production (BP). The biomass production efficiency (BPE), defined as the ratio of BP to photosynthesis, and its variation across and within vegetation types is poorly understood, which hinders our capacity to accurately estimate carbon turnover times and carbon sinks. Here, we present a new global estimation of BPE obtained by combining field measurements from 113 sites with 14 carbon cycle models. Our best estimate of global BPE is 0.41 ± 0.05, excluding cropland. The largest BPE is found in boreal forests (0.48 ± 0.06) and the lowest in tropical forests (0.40 ± 0.04). Carbon cycle models overestimate BPE, although models with carbon-nitrogen interactions tend to be more realistic. Using observation-based estimates of global photosynthesis, we quantify the global BP of non-cropland ecosystems of 41 ± 6 Pg C/year. This flux is less than net primary production as it does not contain carbon allocated to symbionts, used for exudates or volatile carbon compound emissions to the atmosphere. Our study reveals a positive bias of 24 ± 11% in the model-estimated BP (10 of 14 models). When correcting models for this bias while leaving modeled carbon turnover times unchanged, we found that the global ecosystem carbon storage change during the last century is decreased by 67% (or 58 Pg C).

Placental mitochondria and reactive oxygen species in the physiology and pathophysiology of pregnancy.

Mitochondria are central to cell function. The placenta forms the interface between maternal and fetal systems, and placental mitochondria have critical roles in maintaining pregnancy. The placenta is unusual in having two adjacent cell layers (cytotrophoblasts and the syncytiotrophoblast) with vastly different mitochondria that have distinct functions in health and disease. Mitochondria both produce the majority of reactive oxygen species (ROS), and are sensitive to ROS. ROS are important in allowing cells to sense their environment through mitochondrial-centred signalling, and this signalling also helps cells/tissues adapt to changing environments. However, excessive ROS are damaging, and increased ROS levels are associated with pregnancy complications, including the important disorders preeclampsia and gestational diabetes mellitus. Here we review the function of placental mitochondria in healthy pregnancy, and also in pregnancy complications. Placental mitochondria are critical to cell function, and mitochondrial damage is a feature of pregnancy complications. However, the responsiveness of mitochondria to ROS signalling may be central to placental adaptations that mitigate damage, and placental mitochondria are an attractive target for the development of therapeutics to improve pregnancy outcomes.

Maternal selenium deficiency during pregnancy in mice increases thyroid hormone concentrations, alters placental function and reduces fetal growth.

KEY POINTS: Inappropriate intake of key micronutrients in pregnancy is known to alter maternal endocrine status, impair placental development and induce fetal growth restriction. Selenium is an essential micronutrient required for the function of approximately 25 important proteins. However, the specific effects of selenium deficiency during pregnancy on maternal, placental and fetal outcomes are poorly understood. The present study demonstrates that maternal selenium deficiency increases maternal triiodothyronine and tetraiodothyronine concentrations, reduces fetal blood glucose concentrations, and induces fetal growth restriction. Placental expression of key selenium-dependent thyroid hormone converting enzymes were reduced, whereas the expression of key placental nutrient transporters was dysregulated. Selenium deficiency had minimal impact on selenium-dependent anti-oxidants but increased placental copper concentrations and expression of superoxide dismutase 1. These results highlight the idea that selenium deficiency during pregnancy may contribute to thyroid dysfunction, causing reduced fetal growth, that may precede programmed disease outcomes in offspring. ABSTRACT: Selenium is a trace element fundamental to diverse homeostatic processes, including anti-oxidant regulation and thyroid hormone metabolism. Selenium deficiency in pregnancy is common and increases the risk of pregnancy complications including fetal growth restriction. Although altered placental formation may contribute to these poor outcomes, the mechanism by which selenium deficiency contributes to complications in pregnancy is poorly understood. Female C57BL/6 mice were randomly allocated to control (>190 µg kg-1 , n = 8) or low selenium (<50 µg kg-1 , n = 8) diets 4 weeks prior to mating and throughout gestation. Pregnant mice were killed at embryonic day 18.5 followed by collection of maternal and fetal tissue. Maternal and fetal plasma thyroid hormone concentrations were analysed, as was placental expression of key selenoproteins involved in thyroid metabolism and anti-oxidant defences. Selenium deficiency increased plasma tetraiodothyronine and triiodothyronine concentrations. This was associated with a reduction in placental expression of key selenodependent deiodinases, DIO2 and DIO3. Placental expression of selenium-dependent anti-oxidants was unaffected by selenium deficiency. Selenium deficiency reduced fetal glucose concentrations, leading to reduced fetal weight. Placental glycogen content was increased within the placenta, as was Slc2a3 mRNA expression. This is the first study to demonstrate that selenium deficiency may reduce fetal weight through increased maternal thyroid hormone concentrations, impaired placental thyroid hormone metabolism and dysregulated placental nutrient transporter expression. The study suggests that the magnitude of selenium deficiency commonly reported in pregnant women may be sufficient to impair thyroid metabolism but not placental anti-oxidant concentrations.

Assessing regional drought impacts on vegetation and evapotranspiration: a case study in Guanacaste, Costa Rica.

This research investigates ecological responses to drought by developing a conceptual framework of vegetation response and investigating how multiple measures of drought can improve regional drought monitoring. We apply this approach to a case study of a recent drought in Guanacaste, Costa Rica. First, we assess drought severity with the Standard Precipitation Index (SPI) based on a 64-yr precipitation record derived from a combination of Global Precipitation Climatology Center data and satellite observations from Tropical Rainfall Measuring Mission and Global Precipitation Measurement. Then, we examine spatial patterns of precipitation, vegetation greenness, evapotranspiration (ET), potential evapotranspiration (PET), and evaporative stress index (ESI) during the drought years of 2013, 2014, and 2015 relative to a baseline period (2002-2012). We compute wet season (May-October) anomalies for precipitation at 0.25° spatial resolution, normalized difference vegetation index (NDVI) at 30-m spatial resolution, and ET, PET and ESI derived with the Priestley-Taylor Jet Propulsion Laboratory (PT-JPL) model at 1-km spatial resolution. We assess patterns of landscape response across years and land cover types including three kinds of forest (deciduous, old growth, and secondary), grassland, and cropland. Results show that rainfall in Guanacaste reached an all-time low in 2015 over a 64-yr record (wet season SPI = -3.46), resulting in NDVI declines. However, ET and ESI did not show significant anomalies relative to a baseline, drought-free period. Forests in the region exhibited lower water stress compared to grasslands and had smaller declines, and even some increases, in NDVI and ET during the drought period. This work highlights the value of using multiple measures to assess ecosystem responses to drought. It also suggests that agricultural land management has an opportunity to integrate these findings by emulating some of the characteristics of drought-resilient ecosystems in managed systems.

Warm spring reduced carbon cycle impact of the 2012 US summer drought.

The global terrestrial carbon sink offsets one-third of the world's fossil fuel emissions, but the strength of this sink is highly sensitive to large-scale extreme events. In 2012, the contiguous United States experienced exceptionally warm temperatures and the most severe drought since the Dust Bowl era of the 1930s, resulting in substantial economic damage. It is crucial to understand the dynamics of such events because warmer temperatures and a higher prevalence of drought are projected in a changing climate. Here, we combine an extensive network of direct ecosystem flux measurements with satellite remote sensing and atmospheric inverse modeling to quantify the impact of the warmer spring and summer drought on biosphere-atmosphere carbon and water exchange in 2012. We consistently find that earlier vegetation activity increased spring carbon uptake and compensated for the reduced uptake during the summer drought, which mitigated the impact on net annual carbon uptake. The early phenological development in the Eastern Temperate Forests played a major role for the continental-scale carbon balance in 2012. The warm spring also depleted soil water resources earlier, and thus exacerbated water limitations during summer. Our results show that the detrimental effects of severe summer drought on ecosystem carbon storage can be mitigated by warming-induced increases in spring carbon uptake. However, the results also suggest that the positive carbon cycle effect of warm spring enhances water limitations and can increase summer heating through biosphere-atmosphere feedbacks.

Happiness and physical activity levels of first year medical students studying in Cyprus: a cross-sectional survey.

BACKGROUND: Levels of physical activity and happiness may impact the health and performance of future doctors. The specific relationship between physical activity and happiness among first year medical students is unclear. The purpose of this study was to investigate these variables and how they relate within first year, graduate entry Bachelor of Medicine, Bachelor of Surgery students studying in Cyprus. METHODS: Self-administered questionnaires were provided for all first year medical students at the St. George's University of London medical programme delivered by the University of Nicosia Medical School in Cyprus. Physical activity was assessed using the International Physical Activity Questionnaire Short Form and happiness was assessed using the Short Depression Happiness Scale. Surveys were completed by 79 of the 120 students (median age of 24 years). Happiness and continuous measures of physical activity amounts were investigated using spearman's rank-order correlation. Mann-Whitney U Tests were used to make further comparisons between the physical activity levels across happy and depressed groups and gender, as well as to compare the levels of happiness reported by each gender. RESULTS: High levels of physical activity were evident in 60.8% of students. Results suggested depression among 15.2% of students. A positive correlation was observed between happiness and amount of vigorous intensity physical activity among female students (p < 0.05), but not males. Happy females performed more vigorous physical activity than depressed females (p < 0.05). The total amount of physical activity performed, as well as level of happiness, did not significantly differ between genders. CONCLUSIONS: A relationship exists between physical activity and happiness among female first year medical students. The intensity of physical activity may play an important role within this group. There appears to be relatively high levels of physical activity and low levels of depression among male and female first year medical students studying in Cyprus. This study provides new knowledge regarding relationships between happiness and physical activity among first year medical students, and is also the first characterization of happiness and physical activity habits among students in Cyprus. This may help to inform future policies aimed at promoting health and wellness within student communities.