1,673 research outputs found

    Chloroplast microsatellites: measures of genetic diversity and the effect of homoplasy

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    Chloroplast microsatellites have been widely used in population genetic studies of conifers in recent years. However, their haplotype configurations suggest that they could have high levels of homoplasy, thus limiting the power of these molecular markers. A coalescent-based computer simulation was used to explore the influence of homoplasy on measures of genetic diversity based on chloroplast microsatellites. The conditions of the simulation were defined to fit isolated populations originating from the colonization of one single haplotype into an area left available after a glacial retreat. Simulated data were compared with empirical data available from the literature for a species of Pinus that has expanded north after the Last Glacial Maximum. In the evaluation of genetic diversity, homoplasy was found to have little influence on Nei's unbiased haplotype diversity (H(E)) while Goldstein's genetic distance estimates (D2sh) were much more affected. The effect of the number of chloroplast microsatellite loci for evaluation of genetic diversity is also discussed

    Vagal sensory neurons drive mucous cell metaplasia

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    Summary: Airway sensory neuron-produced Substance P heightens allergy-induced goblet cell hyperplasia and hypersecretion of Muc5AC, electrically silencing these overreactive neurons reduced these components of lung type 2 allergic inflammatory response

    A competitive integration model of exogenous and endogenous eye movements

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    We present a model of the eye movement system in which the programming of an eye movement is the result of the competitive integration of information in the superior colliculi (SC). This brain area receives input from occipital cortex, the frontal eye fields, and the dorsolateral prefrontal cortex, on the basis of which it computes the location of the next saccadic target. Two critical assumptions in the model are that cortical inputs are not only excitatory, but can also inhibit saccades to specific locations, and that the SC continue to influence the trajectory of a saccade while it is being executed. With these assumptions, we account for many neurophysiological and behavioral findings from eye movement research. Interactions within the saccade map are shown to account for effects of distractors on saccadic reaction time (SRT) and saccade trajectory, including the global effect and oculomotor capture. In addition, the model accounts for express saccades, the gap effect, saccadic reaction times for antisaccades, and recorded responses from neurons in the SC and frontal eye fields in these tasks. © The Author(s) 2010

    Structure of a bacterial voltage-gated sodium channel pore reveals mechanisms of opening and closing

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    Voltage-gated sodium channels are vital membrane proteins essential for electrical signalling; in humans, they are key targets for the development of pharmaceutical drugs. Here we report the crystal structure of an open-channel conformation of NavMs, the bacterial channel pore from the marine bacterium Magnetococcus sp. (strain MC-1). It differs from the recently published crystal structure of a closed form of a related bacterial sodium channel (NavAb) by having its internal cavity accessible to the cytoplasmic surface as a result of a bend/rotation about a central residue in the carboxy-terminal transmembrane segment. This produces an open activation gate of sufficient diameter to allow hydrated sodium ions to pass through. Comparison of the open and closed structures provides new insight into the features of the functional states present in the activation cycles of sodium channels and the mechanism of channel opening and closing

    Novel use of an exchange catheter to facilitate intubation with an Aintree catheter in a tall patient with a predicted difficult airway: a case report

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    <p>Abstract</p> <p>Introduction</p> <p>The Aintree intubating catheter (Cook<sup>® </sup>Medical Inc., Bloomington, IN, USA) has been shown to successfully facilitate difficult intubations when other methods have failed. The Aintree intubating catheter (Cook<sup>® </sup>Medical Inc., Bloomington, IN, USA) has a fixed length of 56 cm, and it has been suggested in the literature that it may be too short for safe use in patients who are tall.</p> <p>Case presentation</p> <p>We present the case of a 32-year-old, 180 cm tall Caucasian woman with a predicted difficult airway who presented to our facility for an emergency cesarean section. After several failed intubation attempts via direct laryngoscopy, an airway was established with a laryngeal mask airway. After delivery of a healthy baby, our patient's condition necessitated tracheal intubation. A fiber-optic bronchoscope loaded with an Aintree intubating catheter (Cook<sup>® </sup>Medical Inc., Bloomington, IN, USA) was passed through the laryngeal mask airway into the trachea until just above the carina, but was too short to safely allow for the passage of an endotracheal tube.</p> <p>Conclusions</p> <p>We present a novel technique in which the Aintree intubating catheter (Cook<sup>® </sup>Medical Inc., Bloomington, IN, USA) was replaced with a longer (100 cm) exchange catheter, over which an endotracheal tube was passed successfully into the trachea.</p

    DNA Damage in Plant Herbarium Tissue

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    Dried plant herbarium specimens are potentially a valuable source of DNA. Efforts to obtain genetic information from this source are often hindered by an inability to obtain amplifiable DNA as herbarium DNA is typically highly degraded. DNA post-mortem damage may not only reduce the number of amplifiable template molecules, but may also lead to the generation of erroneous sequence information. A qualitative and quantitative assessment of DNA post-mortem damage is essential to determine the accuracy of molecular data from herbarium specimens. In this study we present an assessment of DNA damage as miscoding lesions in herbarium specimens using 454-sequencing of amplicons derived from plastid, mitochondrial, and nuclear DNA. In addition, we assess DNA degradation as a result of strand breaks and other types of polymerase non-bypassable damage by quantitative real-time PCR. Comparing four pairs of fresh and herbarium specimens of the same individuals we quantitatively assess post-mortem DNA damage, directly after specimen preparation, as well as after long-term herbarium storage. After specimen preparation we estimate the proportion of gene copy numbers of plastid, mitochondrial, and nuclear DNA to be 2.4–3.8% of fresh control DNA and 1.0–1.3% after long-term herbarium storage, indicating that nearly all DNA damage occurs on specimen preparation. In addition, there is no evidence of preferential degradation of organelle versus nuclear genomes. Increased levels of C→T/G→A transitions were observed in old herbarium plastid DNA, representing 21.8% of observed miscoding lesions. We interpret this type of post-mortem DNA damage-derived modification to have arisen from the hydrolytic deamination of cytosine during long-term herbarium storage. Our results suggest that reliable sequence data can be obtained from herbarium specimens

    The Main Belt Comets and ice in the Solar System

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    We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies
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