Summary
Sedentary behaviour has emerged as a unique determinant of health in adults. Studies in children and adolescents have been less consistent. We reviewed the evidence to determine if the total ...volume and patterns (i.e. breaks and bouts) of objectively measured sedentary behaviour were associated with adverse health outcomes in young people, independent of moderate‐intensity to vigorous‐intensity physical activity. Four electronic databases (EMBASE MEDLINE, Ovid EMBASE, PubMed and Scopus) were searched (up to 12 November 2015) to retrieve studies among 2‐ to 18‐year‐olds, which used cross‐sectional, longitudinal or experimental designs, and examined associations with health outcomes (adiposity, cardio‐metabolic, fitness, respiratory, bone/musculoskeletal, psychosocial, cognition/academic achievement, gross motor development and other outcomes). Based on 88 eligible observational studies, level of evidence grading and quantitative meta‐analyses indicated that there is limited available evidence that the total volume or patterns of sedentary behaviour are associated with health in children and adolescents when accounting for moderate‐intensity to vigorous‐intensity physical activity or focusing on studies with low risk of bias. Quality evidence from studies with robust designs and methods, objective measures of sitting, examining associations for various health outcomes, is needed to better understand if the overall volume or patterns of sedentary behaviour are independent determinants of health in children and adolescents.
In the lowermost layer of the atmosphere—the troposphere—ozone is an important source of the hydroxyl radical, an oxidant that breaks down most pollutants and some greenhouse gases. High ...concentrations of tropospheric ozone are toxic, however, and have a detrimental effect on human health and ecosystem productivity. Moreover, tropospheric ozone itself acts as an effective greenhouse gas. Much of the present tropospheric ozone burden is a consequence of anthropogenic emissions of ozone precursors resulting in widespread increases in ozone concentrations since the late 1800s. At present, east Asia has the fastest-growing ozone precursor emissions. Much of the springtime east Asian pollution is exported eastwards towards western North America. Despite evidence that the exported Asian pollution produces ozone, no previous study has found a significant increase in free tropospheric ozone concentrations above the western USA since measurements began in the late 1970s. Here we compile springtime ozone measurements from many different platforms across western North America. We show a strong increase in springtime ozone mixing ratios during 1995–2008 and we have some additional evidence that a similar rate of increase in ozone mixing ratio has occurred since 1984. We find that the rate of increase in ozone mixing ratio is greatest when measurements are more heavily influenced by direct transport from Asia. Our result agrees with previous modelling studies, which indicate that global ozone concentrations should be increasing during the early part of the twenty-first century as a result of increasing precursor emissions, especially at northern mid-latitudes, with western North America being particularly sensitive to rising Asian emissions. We suggest that the observed increase in springtime background ozone mixing ratio may hinder the USA’s compliance with its ozone air quality standard.
The barrier to curing HIV-1 is thought to reside primarily in CD4+ T cells containing silent proviruses. To characterize these latently infected cells, we studied the integration profile of HIV-1 in ...viremic progressors, individuals receiving antiretroviral therapy, and viremic controllers. Clonally expanded T cells represented the majority of all integrations and increased during therapy. However, none of the 75 expanded T cell clones assayed contained intact virus. In contrast, the cells bearing single integration events decreased in frequency over time on therapy, and the surviving cells were enriched for HIV-1 integration in silent regions of the genome. Finally, there was a strong preference for integration into, or in close proximity to, Alu repeats, which were also enriched in local hotspots for integration. The data indicate that dividing clonally expanded T cells contain defective proviruses and that the replication-competent reservoir is primarily found in CD4+ T cells that remain relatively quiescent.
Display omitted
•Integration sequencing identifies clonally expanded and single HIV-1 integrations in human subjects•Large clonal families of HIV-1+ cells are likely not part of the latent reservoir•HIV-1 integrates near or into a 30 bp INT-motif found in Alu repeats
HIV-1-infected CD4+ T cells that undergo clonal expansion are able to proliferate because their proviruses are defective. Conversely, the replication-competent reservoir is likely found in the subset of CD4+ T cells that carry unique integrations and remain quiescent.
Caspases are the primary drivers of apoptotic cell death, cleaving cellular proteins that are critical for dismantling the dying cell. Initially translated as inactive zymogenic precursors, caspases ...are activated in response to a variety of cell death stimuli. In addition to factors required for their direct activation (e.g., dimerizing adaptor proteins in the case of initiator caspases that lie at the apex of apoptotic signaling cascades), caspases are regulated by a variety of cellular factors in a myriad of physiological and pathological settings. For example, caspases may be modified posttranslationally (e.g., by phosphorylation or ubiquitylation) or through interaction of modulatory factors with either the zymogenic or active form of a caspase, altering its activation and/or activity. These regulatory events may inhibit or enhance enzymatic activity or may affect activity toward particular cellular substrates. Finally, there is emerging literature to suggest that caspases can participate in a variety of cellular processes unrelated to apoptotic cell death. In these settings, it is particularly important that caspases are maintained under stringent control to avoid inadvertent cell death. It is likely that continued examination of these processes will reveal new mechanisms of caspase regulation with implications well beyond control of apoptotic cell death.
Concern is growing about the effects of urbanization on air pollution and health. Nitrogen dioxide (NO2) released primarily from combustion processes, such as traffic, is a short-lived atmospheric ...pollutant that serves as an air-quality indicator and is itself a health concern. We derive a global distribution of ground-level NO2 concentrations from tropospheric NO2 columns retrieved from the Ozone Monitoring Instrument (OMI). Local scaling factors from a three-dimensional chemistry-transport model (GEOS-Chem) are used to relate the OMI NO2 columns to ground-level concentrations. The OMI-derived surface NO2 data are significantly correlated (r = 0.69) with in situ surface measurements. We examine how the OMI-derived ground-level NO2 concentrations, OMI NO2 columns, and bottom-up NO x emission inventories relate to urban population. Emission hot spots, such as power plants, are excluded to focus on urban relationships. The correlation of surface NO2 with population is significant for the three countries and one continent examined here: United States (r = 0.71), Europe (r = 0.67), China (r = 0.69), and India (r = 0.59). Urban NO2 pollution, like other urban properties, is a power law scaling function of the population size: NO2 concentration increases proportional to population raised to an exponent. The value of the exponent varies by region from 0.36 for India to 0.66 for China, reflecting regional differences in industrial development and per capita emissions. It has been generally established that energy efficiency increases and, therefore, per capita NO x emissions decrease with urban population; here, we show how outdoor ambient NO2 concentrations depend upon urban population in different global regions.
Concern about whether the social–ecological processes that provide for human wellbeing can be sustained has given rise to sustainable development as a broad social goal. As a dynamic force for ...change, entrepreneurship is increasingly expected to contribute to this goal. This article reports on the results of an intensive empirical study investigating the organization design expertise necessary for sustainability-driven entrepreneurs to succeed in a competitive market context. Results reveal five principles of organization design that diverge in important ways from the conventional principles of entrepreneurship, suggesting the expertise required for venture success differs depending on entrepreneurial values and motives.
Grassroots initiatives for change rely on people with limited power, limited resources and limited ability to influence others. From this position, people acting from the bottom up can change their ...own actions, seek to influence others around them and seek to change the social structures that they inhabit. These acts are invariably conceived, initiated and enacted within communities, and there is an emerging interest from practitioner, policy and academic circles in the importance of community as a space for realising pro-environmental change. In this paper, we ask what role grassroots initiatives can have in creating low-carbon communities. Using a theoretical framework from work on community-based practice change initiatives, we discuss the interplay between grassroots action and community capacity. We then present two cases of grassroots low-carbon community initiatives in light of this theoretical work. We conclude by discussing key themes emerging from the cases, including the potential for grassroots initiatives to build community capacity for low-carbon practices, and the importance of locally crafted solutions according to the structures specific to place.
PDF
