Utility of peak torque and rate of torque development characteristics to identify walking performance ability in older women

Objectives:It is unclear whether peak torque and rate of torque development (RTD) measurements can characterize functional differences in older adults according to their performance on a six-minute walk test. This study aimed to examine the efficacy of isometric peak torque and RTD characteristics of the knee extensors to differentiate between functional status in older women who are able (higher functioning) versus those who are unable (lower functioning) to walk 550 m in six minutes.Methods:Ten higher functioning (67±4 years) and 10 lower functioning (68±4 years) older women performed three isometric knee extension maximal voluntary contractions followed by a six-minute walk test. Peak torque and early (RTD100), late (RTD200), and maximum (Peak RTD) RTD measurements were obtained from each contraction.Results:The higher functioning group exhibited greater peak torque, Peak RTD, RTD100, and RTD200 compared to the lower functioning group (P≤0.011), with larger differences occurring for RTD characteristics (39.9-54.9%) than peak torque (20.3%). Multiple regression analysis indicated that RTD200 was the single best predictor of the distance covered during the six-minute walk test (R²=0.437, P=0.002).Conclusions:These findings suggest that knee extensor muscle strength, and in particular RTD, may be an effective discriminator and predictor of walking performance ability in older women.     

Using C4 photosynthesis to increase the yield of rice-rationale and feasibility

90% of the world's rice is grown and consumed in Asia, with each hectare of rice-producing land providing food for 27 people. By 2050, because of population growth and increasing urbanisation, each remaining hectare will have to feed at least 43 people. This means that yields must be increased by at least 50% over the next 40 years to prevent mass malnutrition for the 700 million Asians that currently rely on rice for more than 60% of their daily calorific intake. Since predictive models suggest that yield increases of this magnitude can only be achieved by improving photosynthesis, and because evolution has increased photosynthetic efficiency by 50% in the form of the C4 pathway, one solution is to generate C4 rice. However, this is an ambitious goal that requires proof of concept before any major investment of time and money. Here, we discuss approaches that should allow proof of concept to be tested.     

Environmental and Biotic Controls over Aboveground Biomass Throughout a Tropical Rain Forest

The environmental and biotic factors affecting spatial variation in canopy three-dimensional (3-D) structure and aboveground tree biomass (AGB) are poorly understood in tropical rain forests. We combined field measurements and airborne light detection and ranging (lidar) to quantify 3-D structure and AGB across a 5,016 ha rain forest reserve on the northeastern flank of Mauna Kea volcano, Hawaii Island. We compared AGB among native stands dominated by Metrosideros polymorpha found along a 600–1800 m elevation/climate gradient, and on three substrate-age classes of 5, 20, and 65 kyr. We also analyzed how alien tree invasion, canopy species dominance and topographic relief influence AGB levels. Canopy vertical profiles derived from lidar measurements were strong predictors (r ² = 0.78) of AGB across sites and species. Mean AGB ranged from 48 to 363 Mg ha⁻¹ in native forest stands. Increasing elevation corresponded to a 53–84% decrease in AGB levels, depending upon substrate age. Holding climate constant, changes in substrate age from 5 to 65 kyr corresponded to a 23–53% decline in biomass. Invasion by Psidium cattleianum and Ficus rubiginosa trees resulted in a 19–38% decrease in AGB, with these carbon losses mediated by substrate age. In contrast, the spread of former plantation tree species Fraxinus uhdei corresponded to a 7- to 10-fold increase in biomass. The effects of topographic relief at both local and regional scales were evident in the AGB maps, with poorly drained terrain harboring 76% lower biomass than forests on well-drained relief. Our results quantify the absolute and relative importance of environmental factors controlling spatial variation in tree biomass across a rain forest landscape, and highlight the rapid changes in carbon storage incurred following biological invasion. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Author Contributions  GPA and RFH conceived of or designed the study. GPA, RFH, TAV, DEK, and TKB performed research and analyzed data. GPA, RFH, DEK, and TKB contributed new methods or models. GPA wrote the article.     

Multi-Country Evaluation of the Sensitivity and Specificity of Two Commercially-Available NS1 ELISA Assays for Dengue Diagnosis

Background

Early diagnosis of dengue can assist patient triage and management and prevent unnecessary treatments and interventions. Commercially available assays that detect the dengue virus protein NS1 in the plasma/serum of patients offers the possibility of early and rapid diagnosis.

Methodology/Principal Findings

The sensitivity and specificity of the Pan-E Dengue Early ELISA and the Platelia™ Dengue NS1 Ag assays were compared against a reference diagnosis in 1385 patients in 6 countries in Asia and the Americas. Platelia was more sensitive (66%) than Pan-E (52%) in confirmed dengue cases. Sensitivity varied by geographic region, with both assays generally being more sensitive in patients from SE Asia than the Americas. Both kits were more sensitive for specimens collected within the first few days of illness onset relative to later time points. Pan-E and Platelia were both 100% specific in febrile patients without evidence of acute dengue. In patients with other confirmed diagnoses and healthy blood donors, Platelia was more specific (100%) than Pan-E (90%). For Platelia, when either the NS1 test or the IgM test on the acute sample was positive, the sensitivity versus the reference result was 82% in samples collected in the first four days of fever. NS1 sensitivity was not associated to disease severity (DF or DHF) in the Platelia test, whereas a trend for higher sensitivity in DHF cases was seen in the Pan-E test (however combined with lower overall sensitivity).

Conclusions/Significance

Collectively, this multi-country study suggests that the best performing NS1 assay (Platelia) had moderate sensitivity (median 64%, range 34–76%) and high specificity (100%) for the diagnosis of dengue. The poor sensitivity of the evaluated assays in some geographical regions suggests further assessments are needed. The combination of NS1 and IgM detection in samples collected in the first few days of fever increased the overall dengue diagnostic sensitivity.     

Neuronal Platelet-Activating Factor Receptor Signal Transduction Involves a Pertussis Toxin-Sensitive G-Protein

In most nonneural systems, platelet-activating factor (PAF) receptor effects are mediated by G-proteins that are often pertussis toxin-sensitive. The activation of pertussis toxin-sensitive G-proteins linked to PAF receptors results in the mobilization of intracellular calcium, at least in part, through the second messenger inositol triphosphate. We have sought to determine if a pertussis toxin-sensitive G-protein is involved in the PAF receptor-mediated phenomena of growth cone collapse and of synaptic enhancement in primary neuronal culture. Using infrared differential interference contrast microscopy and patch-clamp recording techniques, pertussis toxin, but not the inactive B oligomer of the toxin, was found to block both the growth cone collapse and the enhanced synaptic release of excitatory transmitter induced by a nonhydrolyzable PAF receptor agonist, making it likely that G_o, G_q, or G_i is the G-protein transducer of PAF receptors in primary neurons. We believe that PAF acts directly on neuronal receptors, which are linked to pertussis toxin-sensitive G-proteins, on the tips of developing neurites, and on presynaptic nerve terminals, leading to growth cone collapse and enhanced synaptic release of transmitter.