Development and validation of a chemostat gut model to study both planktonic and biofilm modes of growth of Clostridium difficile and human microbiota

Copyright: 2014 Crowther et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.The human gastrointestinal tract harbours a complex microbial community which exist in planktonic and sessile form. The degree to which composition and function of faecal and mucosal microbiota differ remains unclear. We describe the development and characterisation of an in vitro human gut model, which can be used to facilitate the formation and longitudinal analysis of mature mixed species biofilms. This enables the investigation of the role of biofilms in Clostridium difficile infection (CDI). A well established and validated human gut model of simulated CDI was adapted to incorporate glass rods that create a solid-gaseous-liquid interface for biofilm formation. The continuous chemostat model was inoculated with a pooled human faecal emulsion and controlled to mimic colonic conditions in vivo. Planktonic and sessile bacterial populations were enumerated for up to 46 days. Biofilm consistently formed macroscopic structures on all glass rods over extended periods of time, providing a framework to sample and analyse biofilm structures independently. Whilst variation in biofilm biomass is evident between rods, populations of sessile bacterial groups (log10 cfu/g of biofilm) remain relatively consistent between rods at each sampling point. All bacterial groups enumerated within the planktonic communities were also present within biofilm structures. The planktonic mode of growth of C. difficile and gut microbiota closely reflected observations within the original gut model. However, distinct differences were observed in the behaviour of sessile and planktonic C. difficile populations, with C. difficile spores preferentially persisting within biofilm structures. The redesigned biofilm chemostat model has been validated for reproducible and consistent formation of mixed species intestinal biofilms. This model can be utilised for the analysis of sessile mixed species communities longitudinally, potentially providing information of the role of biofilms in CDI.Peer reviewe

Breaking of ergodicity and long relaxation times in systems with long-range interactions

The thermodynamic and dynamical properties of an Ising model with both short range and long range, mean field like, interactions are studied within the microcanonical ensemble. It is found that the relaxation time of thermodynamically unstable states diverges logarithmically with system size. This is in contrast with the case of short range interactions where this time is finite. Moreover, at sufficiently low energies, gaps in the magnetization interval may develop to which no microscopic configuration corresponds. As a result, in local microcanonical dynamics the system cannot move across the gap, leading to breaking of ergodicity even in finite systems. These are general features of systems with long range interactions and are expected to be valid even when the interaction is slowly decaying with distance.Comment: 4 pages, 5 figure

The Murmur of the Sleeping Black Hole: Detection of Nuclear Ultraviolet Variability in LINER Galaxies

LINER nuclei, which are present in many nearby galactic bulges, may be the manifestation of low-rate or low-radiative-efficiency accretion onto supermassive central black holes. However, it has been unclear whether the compact UV nuclear sources present in many LINERs are clusters of massive stars, rather than being directly related to the accretion process. We have used HST to monitor the UV variability of a sample of 17 galaxies with LINER nuclei and compact nuclear UV sources. Fifteen of the 17 galaxies were observed more than once, with two to five epochs per galaxy, spanning up to a year. We detect significant variability in most of the sample, with peak-to-peak amplitudes from a few percent to 50%. In most cases, correlated variations are seen in two independent bands (F250W and F330W). Comparison to previous UV measurements indicates, for many objects, long-term variations by factors of a few over decade timescales. Variability is detected in LINERs with and without detected compact radio cores, in LINERs that have broad H-alpha wings detected in their optical spectra (``LINER 1's''), and in those that do not (``LINER 2s''). This variability demonstrates the existence of a non-stellar component in the UV continuum of all types, and sets a lower limit to the luminosity of this component. We note a trend in the UV color (F250W/F330W) with spectral type - LINER 1s tend to be bluer than LINER 2s. This trend may indicate a link between the shape of the nonstellar continuum and the presence or the visibility of a broad-line region. In one target, the post-starburst galaxy NGC 4736, we detect variability in a previously noted UV source that is offset by 2.5" (60 pc in projection) from the nucleus. This may be the nearest example of a binary active nucleus, and of the process leading to black hole merging.Comment: accepted to Ap

Socio-economic status over the life-course and depressive symptoms in men and women in Eastern Europe

Objective: Research into social inequalities in depression has studied western populations but data from non-western countries are sparse. In this paper, we investigate the extent of social inequalities in depression in Eastern Europe, the relative importance of social position at different points of the life-course, and whether social patterning of depression differs between men and women.Method: A cross-sectional study examined 12,053 men and 13,582 women in Russia, Poland and the Czech Republic. Depressive symptoms (16 or above on the CESD-20) were examined in relation to socio-economic circumstances at three phases of the life-course: childhood (household amenities and father's education); own education; current circumstances (financial difficulties and possession of household items).Results: Pronounced social differences in depression exist in men and women throughout Eastern Europe. Depression was largely influenced by current circumstances rather than by early life or education, with effects stronger in Poland and Russia. Odds ratios in men for current disadvantage were 3.16 [95% CI: 2.57-3.89], 3.16 [2.74-3.64] and 2.17 [1.80-2.63] in Russia, Poland and the Czech Republic respectively. Social variables did not explain the female excess in depression, which varied from 2.91 [2.58-3.27] in Russia to 1.90 [1.74-2.08] in Poland. Men were more affected by adult disadvantage than women, leading to narrower sex differentials in the presence of disadvantage.Limitations: Cross-sectional data with recall of childhood conditions were used.Conclusion: Current social circumstances are the strongest influence on increased depressive symptoms in countries which have recently experienced social changes. (C) 2007 Elsevier B.V. All rights reserved

Democratization in a passive dendritic tree : an analytical investigation

One way to achieve amplification of distal synaptic inputs on a dendritic tree is to scale the amplitude and/or duration of the synaptic conductance with its distance from the soma. This is an example of what is often referred to as “dendritic democracy”. Although well studied experimentally, to date this phenomenon has not been thoroughly explored from a mathematical perspective. In this paper we adopt a passive model of a dendritic tree with distributed excitatory synaptic conductances and analyze a number of key measures of democracy. In particular, via moment methods we derive laws for the transport, from synapse to soma, of strength, characteristic time, and dispersion. These laws lead immediately to synaptic scalings that overcome attenuation with distance. We follow this with a Neumann approximation of Green’s representation that readily produces the synaptic scaling that democratizes the peak somatic voltage response. Results are obtained for both idealized geometries and for the more realistic geometry of a rat CA1 pyramidal cell. For each measure of democratization we produce and contrast the synaptic scaling associated with treating the synapse as either a conductance change or a current injection. We find that our respective scalings agree up to a critical distance from the soma and we reveal how this critical distance decreases with decreasing branch radius

Videoconference-based creativity workshops for mental health staff during the COVID-19 pandemic

Background COVID-19 presented significant challenges to psychiatric staff, while social distancing and remote working necessitated digital communications. NHS England prioritised staff wellbeing. Arts-based creativity interventions appear to improve psychological wellbeing, so this study evaluated online Creativity Workshops as a staff support response for COVID-19-related stress. Methods Participants were staff from a South London NHS psychiatric hospital. Group Creativity Workshops were facilitated via Microsoft Teams. Acceptability data on pre- and post-workshop mood and attitudes were self-reported by participants. Feasibility data were gathered from adherence to number of workshop components delivered. Results Eight workshops were delivered in May-September 2020 (N = 55) with high adherence to components. Participants reported significantly increased positive mood and attitudes towards themselves and others; and decreased stress and anxiety. Conclusions Online Creativity Workshops appear feasible and acceptable in reducing stress in psychiatric staff. Integrating a programme of Creativity Workshops within healthcare staff support may benefit staff wellbeing

Public preferences for using quantitative faecal immunochemical test (FIT) vs colonoscopy (CC) as diagnostic test for colorectal cancer: Evidence from an online survey

Background: There has been interest in using the non-invasive, home-based quantitative faecal immunochemical test (FIT) to rule out colorectal cancer (CRC) in high-risk symptomatic patients. Aim: To elicit public preferences for FIT versus colonoscopy (CC) and its delivery in primary care. Design & setting: A cross-sectional online survey in England. Method: A total of 1057 adults (without CRC symptoms and diagnosis) aged 40–59 years were invited from an English online survey panel. Responders were asked to imagine they had been experiencing CRC symptoms that would qualify them for a diagnostic test. Participants were presented with choices between CC and FIT in ascending order of number of CRCs missed by FIT (from 1–10%). It was measured at what number of missed CRCs responders preferred CC over FIT. Results: While 150 participants did not want either of the tests when both missed 1% CRCs, the majority (n = 741, 70.0%) preferred FIT to CC at that level of accuracy. However, this preference reduced to 427 (40.4%) when FIT missed one additional cancer. Women were more likely to tolerate missing CRC when using FIT. Having lower numeracy and perceiving a higher level of risk meant participants were less likely to tolerate a false negative test. Most of those who chose FIT preferred to return it by mail (62.2%), to be informed about normal test results by letter (42.1%), and about abnormal test results face to face (32.5%). Conclusion: While the majority of participants preferred FIT over CC when both tests had the same sensitivity, tolerance for missed CRCs was low

Models of the SL9 Impacts II. Radiative-hydrodynamic Modeling of the Plume Splashback

We model the plume "splashback" phase of the SL9 collisions with Jupiter using the ZEUS-3D hydrodynamic code. We modified the Zeus code to include gray radiative transport, and we present validation tests. We couple the infalling mass and momentum fluxes of SL9 plume material (from paper I) to a jovian atmospheric model. A strong and complex shock structure results. The modeled shock temperatures agree well with observations, and the structure and evolution of the modeled shocks account for the appearance of high excitation molecular line emission after the peak of the continuum light curve. The splashback region cools by radial expansion as well as by radiation. The morphology of our synthetic continuum light curves agree with observations over a broad wavelength range (0.9 to 12 microns). A feature of our ballistic plume is a shell of mass at the highest velocities, which we term the "vanguard". Portions of the vanguard ejected on shallow trajectories produce a lateral shock front, whose initial expansion accounts for the "third precursors" seen in the 2-micron light curves of the larger impacts, and for hot methane emission at early times. Continued propagation of this lateral shock approximately reproduces the radii, propagation speed, and centroid positions of the large rings observed at 3-4 microns by McGregor et al. The portion of the vanguard ejected closer to the vertical falls back with high z-component velocities just after maximum light, producing CO emission and the "flare" seen at 0.9 microns. The model also produces secondary maxima ("bounces") whose amplitudes and periods are in agreement with observations.Comment: 13 pages, 9 figures (figs 3 and 4 in color), accepted for Ap.J. latex, version including full figures at: http://oobleck.tn.cornell.edu/jh/ast/papers/slplume2-20.ps.g