Association of Accelerometry-Measured Physical Activity and Cardiovascular Events in Mobility-Limited Older Adults: The LIFE (Lifestyle Interventions and Independence for Elders) Study.

BACKGROUND:Data are sparse regarding the value of physical activity (PA) surveillance among older adults-particularly among those with mobility limitations. The objective of this study was to examine longitudinal associations between objectively measured daily PA and the incidence of cardiovascular events among older adults in the LIFE (Lifestyle Interventions and Independence for Elders) study. METHODS AND RESULTS:Cardiovascular events were adjudicated based on medical records review, and cardiovascular risk factors were controlled for in the analysis. Home-based activity data were collected by hip-worn accelerometers at baseline and at 6, 12, and 24 months postrandomization to either a physical activity or health education intervention. LIFE study participants (n=1590; age 78.9±5.2 [SD] years; 67.2% women) at baseline had an 11% lower incidence of experiencing a subsequent cardiovascular event per 500 steps taken per day based on activity data (hazard ratio, 0.89; 95% confidence interval, 0.84-0.96; P=0.001). At baseline, every 30 minutes spent performing activities ≥500 counts per minute (hazard ratio, 0.75; confidence interval, 0.65-0.89 [P=0.001]) were also associated with a lower incidence of cardiovascular events. Throughout follow-up (6, 12, and 24 months), both the number of steps per day (per 500 steps; hazard ratio, 0.90, confidence interval, 0.85-0.96 [P=0.001]) and duration of activity ≥500 counts per minute (per 30 minutes; hazard ratio, 0.76; confidence interval, 0.63-0.90 [P=0.002]) were significantly associated with lower cardiovascular event rates. CONCLUSIONS:Objective measurements of physical activity via accelerometry were associated with cardiovascular events among older adults with limited mobility (summary score >10 on the Short Physical Performance Battery) both using baseline and longitudinal data. CLINICAL TRIAL REGISTRATION:URL: http://www.clinicaltrials.gov. Unique identifier: NCT01072500

Food webs: reconciling the structure and function of biodiversity

The global biodiversity crisis concerns not only unprecedented loss of species within communities, but also related consequences for ecosystem function. Community ecology focuses on patterns of species richness and community composition, whereas ecosystem ecology focuses on fluxes of energy and materials. Food webs provide a quantitative framework to combine these approaches and unify the study of biodiversity and ecosystem function. We summarise the progression of food-web ecology and the challenges in using the food-web approach. We identify five areas of research where these advances can continue, and be applied to global challenges. Finally, we describe what data are needed in the next generation of food-web studies to reconcile the structure and function of biodiversity.No Full Tex

Instrumentation et modélisation distribuée de la vague verte de Champs-sur-Marne : premiers résultats

International audienc

Investigation of retention and transfer properties of green roofs: the Green Wave of Champs-sur-Marne (France)

International audienceOne of the main performances of green roofs is to reduce and/or delay urban runoff during the strong rainfall events.The substrate retention capacity and transfer properties is often described by the water retention and hydraulicconductivity curves. This work presents comparison between measured and different theoretical characteristicscurves, as well as determination of more reliable fractal based substrate model.Firstly, samples of organic volcanic substrate from wavy-form green roof of Champs-sur-Marne (France), calledthe Green Wave, were taken for detailed laboratory investigation. In order to simultaneously determine waterretention and hydraulic conductivity curves of this unconventional substrate, special device based on tensiometryand axis translation technique has been designed (Stanic et al, 2018). Then different (semi-)empirical and fractalbased theoretical curves were compared with results obtained in laboratory in order to determine the model thatrealistically describes green roof substrate’s characteristics curves. Models based on (multi-)fractal theory areproved to be able to describe characteristics curves by calibrating several physically based parameters. It wasshown that these models are able to fit better with water retention and hydraulic conductivity curves of the greenroof substrate than the common (semi-)empirical models.At the end we discuss why this kind of approach is very helpful for giving insight into the accuracy of theoreticalcurves in general, regarding both substrate characteristics curves. Also it gives an idea about the most realistictheoretical model, which is a very useful indicator for users and developers of rainfall-runoff models in widercontext. Indeed, taking into account the most accurate option to describe substrate characteristics curves will resultin more reliable runoff estimations

Fatal Epileptic Seizures in Mice Having Compromised Glutathione and Ascorbic Acid Biosynthesis

Reduced glutathione (GSH) and ascorbic acid (AA) are the two most abundant low-molecular-weight antioxidants in mammalian tissues. GclmKO knockout mice lack the gene encoding the modifier subunit of the rate-limiting enzyme in GSH biosynthesis; GclmKO mice exhibit 10–40% of normal tissue GSH levels and show no overt phenotype. GuloKO knockout mice, lacking a functional Gulo gene encoding L-gulono-γ-lactone oxidase, cannot synthesize AA and depend on dietary ascorbic acid for survival. To elucidate functional crosstalk between GSH and AA in vivo, we generated the GclmKO/GuloKO double-knockout (DKO) mouse. DKO mice exhibited spontaneous epileptic seizures, proceeding to death between postnatal day (PND)14 and PND23. Histologically, DKO mice displayed neuronal loss and glial proliferation in the neocortex and hippocampus. Epileptic seizures and brain pathology in young DKO mice could be prevented with AA supplementation in drinking water (1 g/L). Remarkably, in AA-rescued adult DKO mice, the removal of AA supplementation for 2–3 weeks resulted in similar, but more severe, neocortex and hippocampal pathology and seizures, with death occurring between 12 and 21 days later. These results provide direct evidence for an indispensable, yet underappreciated, role for the interplay between GSH and AA in normal brain function and neuronal health. We speculate that the functional crosstalk between GSH and AA plays an important role in regulating glutamatergic neurotransmission and in protecting against excitotoxicity-induced brain damage

Fatal Epileptic Seizures in Mice Having Compromised Glutathione and Ascorbic Acid Biosynthesis

Reduced glutathione (GSH) and ascorbic acid (AA) are the two most abundant low-molecular-weight antioxidants in mammalian tissues. GclmKO knockout mice lack the gene encoding the modifier subunit of the rate-limiting enzyme in GSH biosynthesis; GclmKO mice exhibit 10–40% of normal tissue GSH levels and show no overt phenotype. GuloKO knockout mice, lacking a functional Gulo gene encoding L-gulono-γ-lactone oxidase, cannot synthesize AA and depend on dietary ascorbic acid for survival. To elucidate functional crosstalk between GSH and AA in vivo, we generated the GclmKO/GuloKO double-knockout (DKO) mouse. DKO mice exhibited spontaneous epileptic seizures, proceeding to death between postnatal day (PND)14 and PND23. Histologically, DKO mice displayed neuronal loss and glial proliferation in the neocortex and hippocampus. Epileptic seizures and brain pathology in young DKO mice could be prevented with AA supplementation in drinking water (1 g/L). Remarkably, in AA-rescued adult DKO mice, the removal of AA supplementation for 2–3 weeks resulted in similar, but more severe, neocortex and hippocampal pathology and seizures, with death occurring between 12 and 21 days later. These results provide direct evidence for an indispensable, yet underappreciated, role for the interplay between GSH and AA in normal brain function and neuronal health. We speculate that the functional crosstalk between GSH and AA plays an important role in regulating glutamatergic neurotransmission and in protecting against excitotoxicity-induced brain damage

Glutathione-Deficient Mice Are Susceptible to TCDD-Induced Hepatocellular Toxicity but Resistant to Steatosis

2,3,7,8-Tetrachlorodibenzo-<i>p</i>-dioxin (TCDD) generates both hepatocellular injury and steatosis, processes that involve oxidative stress. Herein, we evaluated the role of the antioxidant glutathione (GSH) in TCDD-induced hepatotoxicity. Glutamate-cysteine ligase (GCL), comprising catalytic (GCLC) and modifier (GCLM) subunits, is rate limiting in de novo GSH biosynthesis; GCLM maintains GSH homeostasis by optimizing the catalytic efficiency of GCL holoenzyme. <i>Gclm­(−/−)</i> transgenic mice exhibit 10–20% of normal tissue GSH levels. <i>Gclm­(−/−)</i> and <i>Gclm­(+/+)</i> wild-type (WT) female mice received TCDD for 3 consecutive days and were then examined 21 days later. As compared with WT littermates, <i>Gclm­(−/−)</i> mice were more sensitive to TCDD-induced hepatocellular toxicity, exhibiting lower reduction potentials for GSH, lower ATP levels, and elevated levels of plasma glutamic oxaloacetic transaminase (GOT) and γ-glutamyl transferase (GGT). However, the histopathology showed that TCDD-mediated steatosis, which occurs in WT mice, was absent in <i>Gclm­(−/−)</i> mice. This finding was consistent with cDNA microarray expression analysis, revealing striking deficiencies in lipid biosynthesis pathways in <i>Gclm­(−/−)</i> mice; qrt-PCR analysis confirmed that <i>Gclm­(−/−)</i> mice are deficient in expression of several lipid metabolism genes including <i>Srebp2</i>, <i>Elovl6</i>, <i>Fasn, Scd1/2</i>, <i>Ppargc1a</i>, and <i>Ppara</i>. We suggest that whereas GSH protects against TCDD-mediated hepatocellular damage, GSH deficiency confers resistance to TCDD-induced steatosis due to impaired lipid metabolism