Stigmergy co-ordinates multicellular collective behaviours during Myxococcus xanthus surface migration

Surface translocation by the soil bacterium Myxococcus xanthus is a complex multicellular phenomenon that entails two motility systems. However, the mechanisms by which the activities of individual cells are coordinated to manifest this collective behaviour are currently unclear. Here we have developed a novel assay that enables detailed microscopic examination of M. xanthus motility at the interstitial interface between solidified nutrient medium and a glass coverslip. Under these conditions, M. xanthus motility is characterised by extensive micro-morphological patterning that is considerably more elaborate than occurs at an air-surface interface. We have found that during motility on solidified nutrient medium, M. xanthus forges an interconnected furrow network that is lined with an extracellular matrix comprised of exopolysaccharides, extracellular lipids, membrane vesicles and an unidentified slime. Our observations have revealed that M. xanthus motility on solidified nutrient medium is a stigmergic phenomenon in which multi-cellular collective behaviours are co-ordinated through trail-following that is guided by physical furrows and extracellular matrix materials

Direct intra-abdominal pressure monitoring via piezoresistive pressure measurement: a technical note

<p>Abstract</p> <p>Background</p> <p>Piezoresistive pressure measurement technique (PRM) has previously been applied for direct IAP measurement in a porcine model using two different devices. Aim of this clinical study was to assess both devices regarding complications, reliability and agreement with IVP in patients undergoing elective abdominal surgery.</p> <p>Methods</p> <p>A prospective cohort study was performed in 20 patients randomly scheduled to receive PRM either by a Coach^®-probe or an Accurate++^®-probe (both MIPM, Mammendorf, Germany). Probes were placed on the greater omentum and passed through the abdominal wall paralleling routine drainages. PRM was compared with IVP measurement by t-testing and by calculating mean difference as well as limits of agreement (LA).</p> <p>Results</p> <p>There were no probe related complications. Due to technical limitations, data could be collected in 3/10 patients with Coach^®and in 7/10 patients with Accurate++^®. Analysis was carried out only for Accurate++^®. Mean values did not differ to mean IVP values. Mean difference to IVP was 0.1 ± 2.8 mmHg (LA: -5.5 to 5.6 mmHg).</p> <p>Conclusion</p> <p>Direct IAP measurement was clinically uneventful. Although results of Accurate++^®were comparable to IVP, the device might be too fragile for IAP measurements in the clinical setting. Local ethical committee trial registration: EK2024</p

Self-organization of bacterial biofilms is facilitated by extracellular DNA

Twitching motility-mediated biofilm expansion is a complex, multicellular behavior that enables the active colonization of surfaces by many species of bacteria. In this study we have explored the emergence of intricate network patterns of interconnected trails that form in actively expanding biofilms of Pseudomonas aeruginosa. We have used high-resolution, phase-contrast time-lapse microscopy and developed sophisticated computer vision algorithms to track and analyze individual cell movements during expansion of P. aeruginosa biofilms. We have also used atomic force microscopy to examine the topography of the substrate underneath the expanding biofilm. Our analyses reveal that at the leading edge of the biofilm, highly coherent groups of bacteria migrate across the surface of the semisolid media and in doing so create furrows along which following cells preferentially migrate. This leads to the emergence of a network of trails that guide mass transit toward the leading edges of the biofilm. We have also determined that extracellular DNA (eDNA) facilitates efficient traffic flow throughout the furrow network by maintaining coherent cell alignments, thereby avoiding traffic jams and ensuring an efficient supply of cells to the migrating front. Our analyses reveal that eDNA also coordinates the movements of cells in the leading edge vanguard rafts and is required for the assembly of cells into the "bulldozer" aggregates that forge the interconnecting furrows. Our observations have revealed that large-scale self-organization of cells in actively expanding biofilms of P. aeruginosa occurs through construction of an intricate network of furrows that is facilitated by eDNA

Peer influence in network markets: a theoretical and empirical analysis

Network externalities spur the growth of networks and the adoption of network goods in two ways. First, they make it more attractive to join a network the larger its installed base. Second, they create incentives for network members to actively recruit new members. Despite indications that the latter "peer effect" can be more important for network growth than the installed-base effect, it has so far been largely ignored in the literature. We address this gap using game-theoretical models. When all early adopters can band together to exert peer influence-an assumption that fits, e.g., the case of firms supporting a technical standard-we find that the peer effect induces additional growth of the network by a factor. When, in contrast, individuals exert peer influence in small groups of size n, the increase in network size is by an additive constant-which, for small networks, can amount to a large relative increase. The difference between small, local, personal networks and large, global, anonymous networks arises endogenously from our analysis. Fundamentally, the first type of networks is "tie-reinforcing," the other, "tie-creating". We use survey data from users of the Internet services, Skype and eBay, to illustrate the main logic of our theoretical results. As predicted by the model, we find that the peer effect matters strongly for the network of Skype users-which effectively consists of numerous small sub-networks-but not for that of eBay users. Since many network goods give rise to small, local networks

A chicken bioreactor for efficient production of functional cytokines

The global market for protein drugs has the highest compound annual growth rate of any pharmaceutical class but their availability, especially outside of the US market, is compromised by the high cost of manufacture and validation compared to traditional chemical drugs. Improvements in transgenic technologies allow valuable proteins to be produced by genetically-modified animals; several therapeutic proteins from such animal bioreactors are already on the market after successful clinical trials and regulatory approval. Chickens have lagged behind mammals in bioreactor development, despite a number of potential advantages, due to the historic difficulty in producing transgenic birds, but the production of therapeutic proteins in egg white of transgenic chickens would substantially lower costs across the entire production cycle compared to traditional cell culture-based production systems. This could lead to more affordable treatments and wider markets, including in developing countries and for animal health applications. Here we report the efficient generation of new transgenic chicken lines to optimize protein production in eggs. As proof-of-concept, we describe the expression, purification and functional characterization of three pharmaceutical proteins, the human cytokine interferon α2a and two species-specific Fc fusions of the cytokine CSF1. Our work optimizes and validates a transgenic chicken system for the cost-effective production of pure, high quality, biologically active protein for therapeutics and other applications

A cross-sectional study of the nutritional status of community-dwelling people with idiopathic Parkinson's disease

<p>Abstract</p> <p>Background</p> <p>Parkinson's disease (PD) patients have an increased risk of under-nutrition, but we are unaware of any population based prevalence studies of under-nutrition in PD. The main objective of this study was to identify the prevalence, and nature, of under-nutrition in a representative population of people with PD.</p> <p>Methods</p> <p>People diagnosed with idiopathic PD from within two PD prevalence study sites in North-East England were asked to participate in this study. Those who participated (n = 136) were assessed using a number of standard rating scales including Hoehn & Yahr stage and Unified Parkinson's Disease Rating Scale (UPDRS). Body mass index (BMI), mid-arm circumference (MAC), triceps skin fold thickness (TSF) and grip strength were recorded together with social and demographic information.</p> <p>Results</p> <p>BMI < 20 identified over 15% of the study group to have under-nutrition. The Malnutritional Universal Screening Tool (MUST) scoring system identified 23.5% of participants at medium or high risk of malnutrition. Low BMI, indicating under-nutrition, was associated with greater age and disease duration, lower MAC, TSF, mid-arm muscle circumference (MAMC), reduced grip strength and a report of unintentional weight loss. Problems increased with increasing age and disease duration and were greater in females.</p> <p>Conclusions</p> <p>Under-nutrition is a problem for around 15% of community dwelling people with PD. All PD patients should be screened for under-nutrition; the MUST score is a useful early screening tool.</p

Peripheral and central arterial pressure and its relationship to vascular target organ damage in carotid artery, retina and arterial stiffness. Development and validation of a tool. The Vaso risk study

<p>Abstract</p> <p>Background</p> <p>Ambulatory blood pressure monitoring (ABPM) shows a better correlation to target organ damage and cardiovascular morbidity-mortality than office blood pressure. A loss of arterial elasticity and an increase in carotid artery intima-media thickness (IMT) has been associated with increased cardiovascular morbidity-mortality. Tools have been developed that allow estimation of the retinal arteriovenous index but not all studies coincide and there are contradictory results in relation to the evolution of the arteriosclerotic lesions and the caliber of the retinal vessels. The purpose of this study is to analyze the relationship between peripheral and central arterial pressure (clinic and ambulatory) and vascular structure and function as evaluated by the carotid artery intima-media thickness, retina arteriovenous index, pulse wave velocity (PWV) and ankle-brachial index in patients with and without type 2 diabetes. In turn, software is developed and validated for measuring retinal vessel thickness and automatically estimating the arteriovenous index.</p> <p>Methods/Design</p> <p>A cross-sectional study involving a control group will be made, with a posterior 4-year follow-up period in primary care. The study patients will be type 2 diabetics, with a control group of non-diabetic individuals. Consecutive sampling will be used to include 300 patients between 34-75 years of age and no previous cardiovascular disease, one-half being assigned to each group. Main measurements: age, gender, height, weight and abdominal circumference. Lipids, creatinine, microalbuminuria, blood glucose, HbA1c, blood insulin, high sensitivity C-reactive protein and endothelial dysfunction markers. Clinic and ambulatory blood pressure monitoring. Carotid ultrasound to evaluate IMT, and retinography to evaluate the arteriovenous index. ECG to assess left ventricle hypertrophy, ankle-brachial index, and pulse wave analysis (PWA) and pulse wave velocity (PWV) with the Sphigmocor System.</p> <p>Discussion</p> <p>We hope to obtain information on the correlation of different ABPM-derived parameters and PWA to organ target damage - particularly vascular structure and function evaluated from the IMT and PWV - and endothelial dysfunction in patients with and without type 2 diabetes. We also hope to demonstrate the usefulness of the instrument developed for the automated evaluation of retinal vascularization in the early detection of alterations in vascular structure and function and in the prognosis of middle-term cardiovascular morbidity.</p> <p>Trial Registration</p> <p>Clinical Trials.gov Identifier: <a href="http://www.clinicaltrials.gov/ct2/show/NCT01325064">NCT01325064</a></p