Ocean processes at the Antarctic continental slope

The Antarctic continental shelves and slopes occupy relatively small areas, but, nevertheless, are important for global climate, biogeochemical cycling and ecosystem functioning. Processes of water mass transformation through sea ice formation/melting and ocean-atmosphere interaction are key to the formation of deep and bottom waters as well as determining the heat flux beneath ice shelves. Climate models, however, struggle to capture these physical processes and are unable to reproduce water mass properties of the region. Dynamics at the continental slope are key for correctly modelling climate, yet their small spatial scale presents challenges both for ocean modelling and for observational studies. Cross-slope exchange processes are also vital for the flux of nutrients such as iron from the continental shelf into the mixed layer of the Southern Ocean. An © 2014 The Authors

Potential Direct and Indirect Effects of Climate Change on a Shallow Natural Lake Fish Assemblage

Much uncertainty exists around how fish communities in shallow lakes will respond to climate change. In this study, we modelled the effects of increased water temperatures on consumption and growth rates of two piscivores (northern pike [Esox lucius] and largemouth bass [Micropterus salmoides]) and examined relative effects of consumption by these predators on two prey species (bluegill [Lepomis macrochirus] and yellow perch [Perca flavescens]). Bioenergetics models were used to simulate the effects of climate change on growth and food consumption using predicted 2040 and 2060 temperatures in a shallow Nebraska Sandhill lake, USA. The patterns and magnitude of daily and cumulative consumption during the growing season (April–October) were generally similar between the two predators. However, growth of northern pike was always reduced (–3 to –45% change) compared to largemouth bass that experienced subtle changes (4 to –6% change) in weight by the end of the growing season. Assuming similar population size structure and numbers of predators in 2040–2060, future consumption of bluegill and yellow perch by northern pike and largemouth bass will likely increase (range: 3–24%), necessitating greater prey biomass to meet future energy demands. The timing of increased predator consumption will likely shift towards spring and fall (compared to summer), when prey species may not be available in the quantities required. Our findings suggest that increased water temperatures may affect species at the edge of their native range (i.e. northern pike) and a potential mismatch between predator and prey could exist

Identification of Salmonella enterica Serovar Dublin-Specific Sequences by Subtractive Hybridization and Analysis of Their Role in Intestinal Colonization and Systemic Translocation in Cattle

Salmonella enterica serovar Dublin is a host-restricted serovar associated with typhoidal disease in cattle. In contrast, the fowl-associated serovar S. enterica serovar Gallinarum is avirulent in calves, yet it invades ileal mucosa and induces enteritis at levels comparable to those induced by S. enterica serovar Dublin. Suppression subtractive hybridization was employed to identify S. enterica serovar Dublin strain SD3246 genes absent from S. enterica serovar Gallinarum strain SG9. Forty-one S. enterica serovar Dublin fragments were cloned and sequenced. Among these, 24 mobile-element-associated genes were identified, and 12 clones exhibited similarity with sequences of known or predicted function in other serovars. Three S. enterica serovar Dublin-specific regions were homologous to regions from the genome of Enterobacter sp. strain 638. Sequencing of fragments adjacent to these three sequences revealed the presence of a 21-kb genomic island, designated S. enterica serovar Dublin island 1 (SDI-1). PCR analysis and Southern blotting showed that SDI-1 is highly conserved within S. enterica serovar Dublin isolates but rarely found in other serovars. To probe the role of genes identified by subtractive hybridization in vivo, 24 signature-tagged S. enterica serovar Dublin SD3246 mutants lacking loci not present in Salmonella serovar Gallinarum SG9 were created and screened by oral challenge of cattle. Though attenuation of tagged SG9 and SD3246 Salmonella pathogenicity island-1 (SPI-1) and SPI-2 mutant strains was detected, no obvious defects of these 24 mutants were detected. Subsequently, a DeltaSDI-1 mutant was found to exhibit weak but significant attenuation compared with the parent strain in coinfection of calves. SDI-1 mutation did not impair invasion, intramacrophage survival, or virulence in mice, implying that SDI-1 does not influence fitness per se and may act in a host-specific manner

Promoting Physical Activity in Middle School Girls: Trial of Activity for Adolescent Girls

Background - Physical activity is important for weight control and good health; however, activity levels decline in the adolescent years, particularly in girls. Design - Group randomized controlled trial. Setting/participants - Middle school girls with English-speaking skills and no conditions to prevent participation in physical activity in 36 schools in six geographically diverse areas of the United States. Random, cross-sectional samples were drawn within schools: 6th graders in 2003 (n=1721) and 8th graders in 2005 (n=3504) and 2006 (n=3502). Intervention - A 2-year study-directed intervention (fall 2003 to spring 2005) targeted schools, community agencies, and girls to increase opportunities, support, and incentives for increased physical activity. Components included programs linking schools and community agencies, physical education, health education, and social marketing. A third-year intervention used school and community personnel to direct intervention activities. Main outcome measures - The primary outcome, daily MET-weighted minutes of moderate-to-vigorous physical activity (MET-weighted MVPA), was assessed using accelerometry. Percent body fat was assessed using anthropometry. Results - After the staff-directed intervention (pre-stated primary outcome), there were no differences (mean=-0.4, 95% CI=-8.2 to 7.4) in adjusted MET-weighted MVPA between 8th-grade girls in schools assigned to intervention or control. Following the Program Champion-directed intervention, girls in intervention schools were more physically active than girls in control schools (mean difference 10.9 MET-weighted minutes of MVPA, 95% CI=0.52-21.2). This difference is about 1.6 minutes of daily MVPA or 80 kcal per week. There were no differences in fitness or percent body fat at either 8th-grade timepoint. Conclusion - A school-based, community-linked intervention modestly improved physical activity in girls

Human intestinal tissue tropism of intimin epsilon O103 Escherichia coli

Human intestinal in vitro organ culture was used to assess the tissue tropism of human isolates of Escherichia coli O103:H2 and O103:H- that express intimin F. Both strains showed tropism for follicle associated epithelium and limited adhesion to other regions of the small and large intestine. This is similar to the tissue tropism shown by intimin gamma enterohaemorrhagic (EHEC) O157:H7, but distinct from that of intimin a enteropathogenic (EPEC) O127:H6. (C) 2002 Federation of European Microbiological Societies. Published by Elsevier Science B.V. All rights reserve

Objectively Assessed Associations between Physical Activity and Body Composition in Middle-School Girls: The Trial of Activity for Adolescent Girls

Declining levels of physical activity probably contribute to the increasing prevalence of overweight in US youth. In this study, the authors examined cross-sectional and longitudinal associations between physical activity and body composition in sixth- and eighth-grade girls. In 2003, girls were recruited from six US states as part of the Trial of Activity for Adolescent Girls. Physical activity was measured using 6 days of accelerometry, and percentage of body fat was calculated using an age- and ethnicity-specific prediction equation. Sixth-grade girls with an average of 12.8 minutes of moderate-to-vigorous physical activity (MVPA) per day (15th percentile) were 2.3 times (95% confidence interval: 1.52, 3.44) more likely to be overweight than girls with 34.7 minutes of MVPA per day (85th percentile), and their percent body fat was 2.64 percentage points greater (95% confidence interval: 1.79, 3.50). Longitudinal analyses showed that percent body fat increased 0.28 percentage points less in girls with a 6.2-minute increase in MVPA than in girls with 4.5-minute decrease (85th and 15th percentiles of change). Associations between MVPA in sixth grade and incidence of overweight in eighth grade were not detected. More population-based research using objective physical activity and body composition measurements is needed to make evidence-based physical activity recommendations for US youth

Hydrocarbons Are Essential for Optimal Cell Size, Division, and Growth of Cyanobacteria.

Cyanobacteria are intricately organized, incorporating an array of internal thylakoid membranes, the site of photosynthesis, into cells no larger than other bacteria. They also synthesize C15-C19 alkanes and alkenes, which results in substantial production of hydrocarbons in the environment. All sequenced cyanobacteria encode hydrocarbon biosynthesis pathways, suggesting an important, undefined physiological role for these compounds. Here, we demonstrate that hydrocarbon-deficient mutants of $\textit{Synechocystis }$ sp. PCC 7002 and $\textit{Synechocystis }$ sp. PCC 6803 exhibit significant phenotypic differences from wild type, including enlarged cell size, reduced growth, and increased division defects. Photosynthetic rates were similar between strains, although a minor reduction in energy transfer between the soluble light harvesting phycobilisome complex and membrane-bound photosystems was observed. Hydrocarbons were shown to accumulate in thylakoid and cytoplasmic membranes. Modeling of membranes suggests these compounds aggregate in the center of the lipid bilayer, potentially promoting membrane flexibility and facilitating curvature. In vivo measurements confirmed that $\textit{Synechocystis }$ sp. PCC 7002 mutants lacking hydrocarbons exhibit reduced thylakoid membrane curvature compared to wild type. We propose that hydrocarbons may have a role in inducing the flexibility in membranes required for optimal cell division, size, and growth, and efficient association of soluble and membrane bound proteins. The recent identification of C15-C17 alkanes and alkenes in microalgal species suggests hydrocarbons may serve a similar function in a broad range of photosynthetic organisms.T.L. was supported by BBSRC Research Grant BB/J016985/1 to C.W.M. D.J.L-S. was supported by the Environmental Services Association Education Trust. L.L.B was supported by a BBSRC Doctoral Training Grant (BB/F017464/1)

Detection of solar-like oscillations from Kepler photometry of the open cluster NGC 6819

Asteroseismology of stars in clusters has been a long-sought goal because the assumption of a common age, distance and initial chemical composition allows strong tests of the theory of stellar evolution. We report results from the first 34 days of science data from the Kepler Mission for the open cluster NGC 6819 -- one of four clusters in the field of view. We obtain the first clear detections of solar-like oscillations in the cluster red giants and are able to measure the large frequency separation and the frequency of maximum oscillation power. We find that the asteroseismic parameters allow us to test cluster-membership of the stars, and even with the limited seismic data in hand, we can already identify four possible non-members despite their having a better than 80% membership probability from radial velocity measurements. We are also able to determine the oscillation amplitudes for stars that span about two orders of magnitude in luminosity and find good agreement with the prediction that oscillation amplitudes scale as the luminosity to the power of 0.7. These early results demonstrate the unique potential of asteroseismology of the stellar clusters observed by Kepler.Comment: 5 pages, 4 figures, accepted by ApJ (Lett.

Microglia contribute to circuit defects in Mecp2 null mice independent of microglia-specific loss of Mecp2 expression

Microglia, the resident CNS macrophages, have been implicated in the pathogenesis of Rett Syndrome (RTT), an X-linked neurodevelopmental disorder. However, the mechanism by which microglia contribute to the disorder is unclear and recent data suggest that microglia do not play a causative role. Here, we use the retinogeniculate system to determine if and how microglia contribute to pathogenesis in a RTT mouse model, the Mecp2 null mouse (Mecp2tm1.1Bird/y). We demonstrate that microglia contribute to pathogenesis by excessively engulfing, thereby eliminating, presynaptic inputs at end stages of disease (≥P56 Mecp2 null mice) concomitant with synapse loss. Furthermore, loss or gain of Mecp2 expression specifically in microglia (Cx3cr1CreER;Mecp2fl/yor Cx3cr1CreER; Mecp2LSL/y) had little effect on excessive engulfment, synapse loss, or phenotypic abnormalities. Taken together, our data suggest that microglia contribute to end stages of disease by dismantling neural circuits rendered vulnerable by loss of Mecp2 in other CNS cell types. DOI: http://dx.doi.org/10.7554/eLife.15224.00