1,286 research outputs found

    Seasonal differences in leaf-level physiology give lianas a competitive advantage over trees in a tropical seasonal forest

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    Lianas are an important component of most tropical forests, where they vary in abundance from high in seasonal forests to low in aseasonal forests. We tested the hypothesis that the physiological ability of lianas to fix carbon (and thus grow) during seasonal drought may confer a distinct advantage in seasonal tropical forests, which may explain pan-tropical liana distributions. We compared a range of leaf-level physiological attributes of 18 co-occurring liana and 16 tree species during the wet and dry seasons in a tropical seasonal forest in Xishuangbanna, China. We found that, during the wet season, lianas had significantly higher CO2 assimilation per unit mass (Amass), nitrogen concentration (Nmass), and δ13C values, and lower leaf mass per unit area (LMA) than trees, indicating that lianas have higher assimilation rates per unit leaf mass and higher integrated water-use efficiency (WUE), but lower leaf structural investments. Seasonal variation in CO2 assimilation per unit area (Aarea), phosphorus concentration per unit mass (Pmass), and photosynthetic N-use efficiency (PNUE), however, was significantly lower in lianas than in trees. For instance, mean tree Aarea decreased by 30.1% from wet to dry season, compared with only 12.8% for lianas. In contrast, from the wet to dry season mean liana δ13C increased four times more than tree δ13C, with no reduction in PNUE, whereas trees had a significant reduction in PNUE. Lianas had higher Amass than trees throughout the year, regardless of season. Collectively, our findings indicate that lianas fix more carbon and use water and nitrogen more efficiently than trees, particularly during seasonal drought, which may confer a competitive advantage to lianas during the dry season, and thus may explain their high relative abundance in seasonal tropical forests

    Modifying Effects of the HFE Polymorphisms on the Association between Lead Burden and Cognitive Decline

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    Background: As iron and lead promote oxidative damage, and hemochromatosis (HFE) gene polymorphisms increase body iron burden, HFE variant alleles may modify the lead burden and cognitive decline relationship. Objective: Our goal was to assess the modifying effects of HFE variants on the lead burden and cognitive decline relation in older adults. Methods: We measured tibia and patella lead using K-X-ray fluorescence (1991–1999) among participants of the Normative Aging Study, a longitudinal study of community-dwelling men from greater Boston. We assessed cognitive function with the Mini-Mental State Examination (MMSE) twice (1993–1998 and 1995–2000) and genotyped participants for HFE polymorphisms. We estimated the adjusted mean differences in lead-associated annual cognitive decline across HFE genotype groups (n = 358). Results: Higher tibia lead was associated with steeper cognitive decline among participants with at least one HFE variant allele compared with men with only wild-type alleles (p interaction = 0.03), such that a 15 μg/g increase in tibia lead was associated with a 0.2 point annual decrement in MMSE score among HFE variant allele carriers. This difference in scores among men with at least one variant allele was comparable to the difference in baseline MMSE scores that we observed among men who were 4 years apart in age. Moreover, the deleterious association between tibia lead and cognitive decline appeared progressively worse in participants with increasingly more copies of HFE variant alleles (p-trend = 0.008). Results for patella lead were similar. Conclusion: Our findings suggest that HFE polymorphisms greatly enhance susceptibility to lead-related cognitive impairment in a pattern consistent with allelelic dose

    Transgenic avidin maize is resistant to storage insect pests

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    Avidin is a glycoprotein found in chicken egg white, that sequesters the vitamin biotin. Here we show that when present in maize at levels of ≥100 p.p.m., avidin is toxic to and prevents development of insects that damage grains during storage. Insect toxicity is caused by a biotin deficiency, as shown by prevention of toxicity with biotin supplementation. The avidin maize is not, however, toxic to mice when administered as the sole component of their diet for 21 days. These data suggest that avidin expression in food or feed grain crops can be used as a biopesticide against a spectrum of stored-product insect pests

    Effects of Particulate Matter on Genomic DNA Methylation Content and iNOS Promoter Methylation

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    BACKGROUND: Altered patterns of gene expression mediate the effects of particulate matter (PM) on human health, but mechanisms through which PM modifies gene expression are largely undetermined. OBJECTIVES: We aimed at identifying short- and long-term effects of PM exposure on DNA methylation, a major genomic mechanism of gene expression control, in workers in an electric furnace steel plant with well-characterized exposure to PM with aerodynamic diameters < 10 microm (PM(10)). METHODS: We measured global genomic DNA methylation content estimated in Alu and long interspersed nuclear element-1 (LINE-1) repeated elements, and promoter DNA methylation of iNOS (inducible nitric oxide synthase), a gene suppressed by DNA methylation and induced by PM exposure in blood leukocytes. Quantitative DNA methylation analysis was performed through bisulfite PCR pyrosequencing on blood DNA obtained from 63 workers on the first day of a work week (baseline, after 2 days off work) and after 3 days of work (postexposure). Individual PM(10) exposure was between 73.4 and 1,220 microg/m(3). RESULTS: Global methylation content estimated in Alu and LINE-1 repeated elements did not show changes in postexposure measures compared with baseline. PM(10) exposure levels were negatively associated with methylation in both Alu [beta = -0.19 \%5-methylcytosine (\%5mC); p = 0.04] and LINE-1 [beta = -0.34 \%5mC; p = 0.04], likely reflecting long-term PM(10) effects. iNOS promoter DNA methylation was significantly lower in postexposure blood samples compared with baseline (difference = -0.61 \%5mC; p = 0.02). CONCLUSIONS: We observed changes in global and gene specific methylation that should be further characterized in future investigations on the effects of PM

    Alpha-particle-induced complex chromosome exchanges transmitted through extra-thymic lymphopoiesis in vitro show evidence of emerging genomic instability

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    Human exposure to high-linear energy transfer α-particles includes environmental (e.g. radon gas and its decay progeny), medical (e.g. radiopharmaceuticals) and occupational (nuclear industry) sources. The associated health risks of α-particle exposure for lung cancer are well documented however the risk estimates for leukaemia remain uncertain. To further our understanding of α-particle effects in target cells for leukaemogenesis and also to seek general markers of individual exposure to α-particles, this study assessed the transmission of chromosomal damage initially-induced in human haemopoietic stem and progenitor cells after exposure to high-LET α-particles. Cells surviving exposure were differentiated into mature T-cells by extra-thymic T-cell differentiation in vitro. Multiplex fluorescence in situ hybridisation (M-FISH) analysis of naïve T-cell populations showed the occurrence of stable (clonal) complex chromosome aberrations consistent with those that are characteristically induced in spherical cells by the traversal of a single α-particle track. Additionally, complex chromosome exchanges were observed in the progeny of irradiated mature T-cell populations. In addition to this, newly arising de novo chromosome aberrations were detected in cells which possessed clonal markers of α-particle exposure and also in cells which did not show any evidence of previous exposure, suggesting ongoing genomic instability in these populations. Our findings support the usefulness and reliability of employing complex chromosome exchanges as indicators of past or ongoing exposure to high-LET radiation and demonstrate the potential applicability to evaluate health risks associated with α-particle exposure.This work was supported by the Department of Health, UK. Contract RRX95 (RMA NSDTG)

    Fab glycosylation of immunoglobulin G does not associate with improvement of rheumatoid arthritis during pregnancy

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    Background: Changes in immunoglobulin G (IgG) constant domain (Fc) glycosylation are associated with changes in rheumatoid arthritis (RA) disease activity in response to pregnancy. Here, we sought to determine whether the same holds true for variable domain (Fab) glycosylation. Methods: IgGs were captured from RA and control sera obtained before (RA only), during and after pregnancy, followed by Fc and Fab separation, glycan release, and mass spectrometric detection. In parallel,

    Lead Exposure and Behavior among Young Children in Chennai, India

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    Background: Lead exposure has long been associated with deficits in IQ among children. However, few studies have assessed the impact of lead on specific domains of behavior and cognition. Objective: We evaluated the associations between lead and different domains of neurobehavior and their relative sensitivity to lead. Methods: We determined blood lead levels using a LeadCare instrument in 756 children 3–7 years of age attending pre- and elementary schools in Chennai, India. Anxiety, social problems, inattention, hyperactivity, and attention deficit hyperactivity disorder (ADHD), as well as executive function were assessed in children by their schoolteachers using Conners’ Teacher Rating Scales-39, Conners’ ADHD/Diagnostic and Statistical Manual for Mental Disorders, 4th Edition Scales (CADS), and the Behavior Rating Inventory of Executive Function questionnaires, with higher scores denoting worse behavior. Analyses were carried out using multivariate generalized estimating equations with comparisons of outcome Z-scores to assess the relative strengths of the associations between log-blood lead and the different domains of behavior. Results: Mean blood lead level was 11.4 ± 5.3 μg/dL. Blood lead was associated with higher anxiety (β = 0.27, p = 0.01), social problems (β = 0.20, p = 0.02), and higher scores in the ADHD index (β = 0.17; p = 0.05). The effect estimate was highest for global executive function (β = 0.42; p < 0.001). Conclusions: Higher blood lead levels in this population of young children is associated with increased risk of neurobehavioral deficits and ADHD, with executive function and attention being particularly vulnerable domains to the effects of lead

    Event-related alpha suppression in response to facial motion

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    This article has been made available through the Brunel Open Access Publishing Fund.While biological motion refers to both face and body movements, little is known about the visual perception of facial motion. We therefore examined alpha wave suppression as a reduction in power is thought to reflect visual activity, in addition to attentional reorienting and memory processes. Nineteen neurologically healthy adults were tested on their ability to discriminate between successive facial motion captures. These animations exhibited both rigid and non-rigid facial motion, as well as speech expressions. The structural and surface appearance of these facial animations did not differ, thus participants decisions were based solely on differences in facial movements. Upright, orientation-inverted and luminance-inverted facial stimuli were compared. At occipital and parieto-occipital regions, upright facial motion evoked a transient increase in alpha which was then followed by a significant reduction. This finding is discussed in terms of neural efficiency, gating mechanisms and neural synchronization. Moreover, there was no difference in the amount of alpha suppression evoked by each facial stimulus at occipital regions, suggesting early visual processing remains unaffected by manipulation paradigms. However, upright facial motion evoked greater suppression at parieto-occipital sites, and did so in the shortest latency. Increased activity within this region may reflect higher attentional reorienting to natural facial motion but also involvement of areas associated with the visual control of body effectors. © 2014 Girges et al
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