5,046 research outputs found

    Visualizing Muscle Assembly and Function in C. elegans

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    Myofibrils produce the forces that shorten muscles during contraction and are composed of proteins arranged in repeating contractile units (sarcomeres). These are composed of various proteins that self-organize into precise, alternating groups. The process of myofibril assembly is robust, flexible, and medically relevant. Various protein isoforms have evolved to modify the assembly process and generate a variety of muscle types with distinct physiologies and dynamics. To study myofibril assembly, I used the nematode Caenorhabditis elegans (C. elegans) which is an ideal model organism for this because it is transparent and has a variety of different muscle types that are responsible for locomotion, egg-laying, and defecation. To visualize myofibril assembly, I used transgenic gene-edited strains that express fluorescently-tagged myofibril proteins to determine when these myofibrillar proteins are expressed during muscle development and assemble into nascent and functional myofibrils. To observe the entire process of myofibril assembly at high resolution, I imaged developing C. elegans embryos with dual-view inverted selective plane illumination microscopy (diSPIM), a novel system to identify, measure, and classify how each muscle component becomes organized. In addition, I used confocal microscopy and functional assays on adult worms to determine whether fluorescent-tagging interferes with normal myofibril organization, growth, and physiology

    Identifying Temporal Codes in Spontaneously Active Sensory Neurons

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    The manner in which information is encoded in neural signals is a major issue in Neuroscience. A common distinction is between rate codes, where information in neural responses is encoded as the number of spikes within a specified time frame (encoding window), and temporal codes, where the position of spikes within the encoding window carries some or all of the information about the stimulus. One test for the existence of a temporal code in neural responses is to add artificial time jitter to each spike in the response, and then assess whether or not information in the response has been degraded. If so, temporal encoding might be inferred, on the assumption that the jitter is small enough to alter the position, but not the number, of spikes within the encoding window. Here, the effects of artificial jitter on various spike train and information metrics were derived analytically, and this theory was validated using data from afferent neurons of the turtle vestibular and paddlefish electrosensory systems, and from model neurons. We demonstrate that the jitter procedure will degrade information content even when coding is known to be entirely by rate. For this and additional reasons, we conclude that the jitter procedure by itself is not sufficient to establish the presence of a temporal code

    Primate surveys and conservation assessments

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    From first paragraph: The conservation of the world’s primates demands basic, but elusive and hard-to-get, information. Enormous efforts are underway to accumulate this information, and the fortuitous selection of six papers in this issue of Oryx illustrates these endeavours, each highlighting the sort of information needed. Besides a basic understanding of the diversity of primates, we need to know where they live (their geography and habitat requirements) and in what numbers. Only with such data is it possible to identify and evaluate the threats to their continued existence. Field research on particular aspects of primate ecology, behaviour, reproduction and demography provide an understanding of how primates respond to these threats and what conservation measures will be possible, effective and appropriate.Output Type: editoria

    Colours of Bulges and Discs within Galaxy Clusters and the Signature of Disc Fading on Infall

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    The origins of the bulge and disc components of galaxies are of primary importance to understanding galaxy formation. Here bulge–disc decomposition is performed simultaneously in B and R bands for 922 bright galaxies in eight nearby (z \u3c 0.06) clusters with deep redshift coverage using photometry from the National Optical Astronomy Observatory (NOAO) Fundamental Plane Survey. The total galaxy colours follow a universal colour–magnitude relation (CMR). The discs of L* galaxies are 0.24 mag bluer in B−R than bulges. Bulges have a significant CMR slope while the CMR slope of discs is flat. Thus the slope of the CMR of the total light is driven primarily (60 per cent) by the bulge CMR, and to a lesser extent (40 per cent) by the change in the bulge‐to‐total ratio as a function of magnitude. The colours of the bulge and disc components do not depend on the bulge‐to‐total ratio, for galaxies with bulge‐to‐total ratios greater than 0.2. While the colours of the bulge components do not depend significantly on environment, the median colours of discs vary significantly, with discs in the cluster centre redder by 0.10 mag than those at the virial radius. Thus while star formation in bulges appears to be regulated primarily by mass‐dependent, and hence presumably internal, processes, that of discs is affected by the cluster environment

    The Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS): survey design, data catalogue and GAMA/WiggleZ spectroscopy

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    © 2016 The Authors. We present the Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS), a spectroscopic catalogue of radio sources designed to include the full range of radio AGN populations out to redshift z ~ 0.8. The catalogue covers ~800 deg 2 of sky, and provides optical identifications for 19 179 radio sources from the 1.4 GHz Faint Images of the Radio Sky at Twenty-cm (FIRST) survey down to an optical magnitude limit of i mod < 20.5 in Sloan Digital Sky Survey (SDSS) images. Both galaxies and point-like objects are included, and no colour cuts are applied. In collaboration with the WiggleZ and Galaxy And Mass Assembly (GAMA) spectroscopic survey teams, we have obtained new spectra for over 5000 objects in the LARGESS sample. Combining these new spectra with data from earlier surveys provides spectroscopic data for 12 329 radio sources in the survey area, of which 10 856 have reliable redshifts. 85 per cent of the LARGESS spectroscopic sample are radio AGN (median redshift z = 0.44), and 15 per cent are nearby star-forming galaxies (median z = 0.08). Low-excitation radio galaxies (LERGs) comprise the majority (83 per cent) of LARGESS radio AGN at z < 0.8, with 12 per cent being high-excitation radio galaxies (HERGs) and 5 per cent radioloud QSOs. Unlike the more homogeneous LERG and QSO sub-populations, HERGs are a heterogeneous class of objects with relatively blue optical colours and a wide dispersion in mid-infrared colours. This is consistent with a picture in which most HERGs are hosted by galaxies with recent or ongoing star formation as well as a classical accretion disc

    Anterior cruciate ligament reconstruction with bone-patellar tendon-bone autograft versus allograft in young patients

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    Objectives: Traditionally, bone-patella tendon-bone (BTB) autograft has been the gold standard graft choice for younger, athletic patients requiring ACL reconstruction. However, donor site morbidity, post-operative patella fracture, and increased operative time have led many surgeons to choose BTB allograft for their reconstructions. Opponents of allografts feel that slower healing time, higher rate of graft failure, and potential for disease transmission makes them undesirable graft choices in athletic patients. The purpose of this study is to evaluate the clinical outcomes, both subjective and objective, of young patients that who have undergone either BTB autograft or allograft reconstructions with a minimum of 2-year follow-up. Methods: One hundred and twenty patients (60 autograft, 60 allograft), age 25 and below at time of surgery, were contacted after being retrospectively identified as patients having an ACL reconstruction with either a BTB allograft or autograft by one senior surgeon. Patients were administered the Lysholm Knee Scoring Scale and IKDC Subjective Knee Evaluation questionnaires. Fifty (25 BTB autograft and 25 BTB allograft) of the 120 returned for physical examination as well as completion of a single leg hop test and laxity evaluation using a KT-1000 arthrometer evaluation. Of the 120 patients contacted, there were a total of 7 failures (5.8%) requiring revision, 6 in the allograft group (86%) and 1 in the autograft group (14%). Results: The average Lysholm scores were 89.0 and 89.56 and the average IKDC scores were 90.8 and 92.1 in the autograft and allograft groups respectively. The differences in the Lysholm scores and the IKDC scores were not significant. The single leg hop and KT-1000 scores were also not significantly different. One autograft patient had a minor motion deficit. Three allograft patients had a grade 1 Lachman and pivot glide. One autograft patient and two allograft patients had mild patellafemoral crepitus. There was no significant difference in anterior knee pain between the two groups Conclusion: There is no significant difference in patient-rated outcome between ACL reconstructions using BTB autografts versus allografts. However, the overall study group did reveal an increased failure rate requiring revision in the allograft group. © The Author(s) 2015
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