Pathways and nerve densities in cerebrovascular innervation

It is gradually becoming clear that cerebrovascular nerves contribute to the control of the cerebral circulation although the knowledge of the functional mechanisms is far from complete. However, many aspects of the morphologic substrate have been identified. The basal cerebral arteries receive sympathetic, parasympathetic and sensory innervation, utilizing the superior cervical and stellate, the pterygopalatine and otic, and the trigeminal ganglia, respectively, as the main peripheral sources. Many of the neural pathways to the cerebral arteries have been elucidated. Those to the supratentorial arterial tree are distributed via the cavernous sinus and surrounding regions. Not only the "classical" neurotransmitters, but also many neuropeptides are found in cerebrovascular nerves. This will lead to new insights since the concepts of cotransmission and neuromodulation have been established now. In the arterial wall, a multilayered organization of nerves has been recognized, consisting of paravascular nerve bundles of passage, a superficial plexus and a terminal plexus located at the adventitial-medial border. Human basal cerebral arteries display a topographical heterogeneity of densities of terminal nerve plexuses. Highest nerve densities are found in arterial segments forming the circle of Willis, in the efferent part of the posterior cerebral artery and in the anterior choroidal artery. Nerve density appears to be determined by locality rather than vascular diameter. Furthermore, local decreases in nerve density are observed with ageing and disease in animals and humans.Biomedical Reviews 1995; 4: 35-46

Making sense of real-world scenes

To interact with the world, we have to make sense of the continuous sensory input conveying information about our environment. A recent surge of studies has investigated the processes enabling scene understanding, using increasingly complex stimuli and sophisticated analyses to highlight the visual features and brain regions involved. However, there are two major challenges to producing a comprehensive framework for scene understanding. First, scene perception is highly dynamic, subserving multiple behavioral goals. Second, a multitude of different visual properties co-occur across scenes and may be correlated or independent. We synthesize the recent literature and argue that for a complete view of scene understanding, it is necessary to account for both differing observer goals and the contribution of diverse scene properties

Two-dimensional superconductivity at the (111)LaAlO3_3/SrTiO3_3 interface

We report on the discovery and transport study of the superconducting ground state present at the (111)LaAlO$_3$/SrTiO$_3$ interface. The superconducting transition is consistent with a Berezinskii-Kosterlitz-Thouless transition and its 2D nature is further corroborated by the anisotropy of the critical magnetic field, as calculated by Tinkham. The estimated superconducting layer thickness and coherence length are 10 nm and 60 nm, respectively. The results of this work provide a new platform to clarify the microscopic details of superconductivity at LaAlO$_3$/SrTiO$_3$ interfaces, in particular in what concerns the link with orbital symmetry.Comment: 4 pages, 4 figure

Restoration of SMN in Schwann cells reverses myelination defects and improves neuromuscular function in spinal muscular atrophy

Spinal muscular atrophy (SMA) is a neuromuscular disease caused by low levels of SMN protein, primarily affecting lower motor neurons. Recent evidence from SMA and related conditions suggests that glial cells can influence disease severity. Here, we investigated the role of glial cells in the peripheral nervous system by creating SMA mice selectively overexpressing SMN in myelinating Schwann cells (Smn(−/−);SMN2(tg/0);SMN1(SC)). Restoration of SMN protein levels restricted solely to Schwann cells reversed myelination defects, significantly improved neuromuscular function and ameliorated neuromuscular junction pathology in SMA mice. However, restoration of SMN in Schwann cells had no impact on motor neuron soma loss from the spinal cord or ongoing systemic and peripheral pathology. This study provides evidence for a defined, intrinsic contribution of glial cells to SMA disease pathogenesis and suggests that therapies designed to include Schwann cells in their target tissues are likely to be required in order to rescue myelination defects and associated disease symptoms

Optimal location of tsunami warning buoys and sea level monitoring stations in the mediterranean sea

The present study determines the optimal location of detection components of a tsunami warning system in the Mediterranean region given the existing and planned infrastructure. Specifically, we examine the locations of existing tsunameters DART buoys and coastal sea-level monitoring stations to see if additional buoys and stations will improve the proportion of the coastal population that may receive a warning ensuring a timely response. A spreadsheet model is used to examine this issue. Based on the historical record of tsunamis and assuming international cooperation in tsunami detection, it is demonstrated that the existing network of sea level stations and tsunameters enable around ninety percent of the coastal population of the Mediterranean Sea to receive a 15 minute warning. Improvement in this result can be achieved through investment in additional real-time, coastal, sea level monitoring stations. This work was undertaken as a final year undergraduate research project

Using Galvanic Vestibular Stimulation to Induce Post-Roll Illusion in a Fixed-Base Flight Simulator

INTRODUCTION: The illusions of head motion induced by galvanic vestibular stimulation (GVS) can be used to compromise flight performance of pilots in fixed-base simulators. However, the stimuli used in the majority of studies fail to mimic disorientation in realistic flight because they are independent from the simulated aircraft motion. This study investigated the potential of bilateral-bipolar GVS coupled to aircraft roll in a fixed-base simulator to mimic vestibular spatial disorientation illusions, specifically the “post-roll illusion” observed during flight.METHODS: There were 14 nonpilot subjects exposed to roll stimuli in a flight simulator operating in a fixed-base mode. GVS was delivered via carbon rubber electrodes on the mastoid processes. The electrical stimulus was driven by the high-pass filtered aircraft roll rate to mimic the semicircular canals’ physiological response. The post-roll test scenarios excluded outside visual cues or instruments and required subjects to actively maintain a constant bank angle after an abrupt stop following a passive prolonged roll maneuver. The anticipated outcome was an overshot in roll elicited by the GVS signal. RESULTS: The responses across subjects showed large variability, with less than a third aligning with the post-roll illusion. Subjective ratings suggest that the high-pass filtered GVS stimuli were mild and did not induce a clear sense of roll direction. However, uncontrolled head movements during stimulation might have obscured the intended effects of GVS-evoked illusory head movements. CONCLUSION: The mild and transient GVS stimuli used in this study, together with the uncontrolled head movements, did not convincingly mimic the post-roll illusion.</p

Potassium secretion by the descending limb or pars recta of the juxtamedullary nephron in vivo

Potassium secretion by the descending limb or pars recta of the juxtamedullary nephron in vivo. Potassium reabsorption by the juxtamedullary nephron up to the hairpin turn was studied by the micropuncture technique in the exposed renal papilla of rats. In 18 nondiuretic rats, the fraction of filtered potassium remaining at the end of the desdending limb averaged 113 ± 9%, indicating either that potassium is not reabsorbed by the juxtamedullary proximal tubule and descending limb or that potassium is reabsorbed and secreted in those segments. Furosemide, a drug which inhibits NaCl reabsorption in the ascending limb downstream from the descending limb, significantly decreased the potassium remaining at the end of the descending limb from 106 ± 12 to 72 ± 11% in seven rats. Benzolamide, a drug which inhibits reabsorption of NaHCO3 and water in the proximal tubule upstream from the descending limb, significantly increased the potassium remaining from 103 ± 13 to 177 ± 32% in eight rats. These findings support the hypothesis that in the rat, potassium is normally reabsorbed by the proximal convoluted tubule and secreted in the pars recta or descending limb of the juxtamedullary nephron

The effect of organelle discovery upon sub-cellular protein localisation.

Prediction of protein sub-cellular localisation by employing quantitative mass spectrometry experiments is an expanding field. Several methods have led to the assignment of proteins to specific subcellular localisations by partial separation of organelles across a fractionation scheme coupled with computational analysis. Methods developed to analyse organelle data have largely employed supervised machine learning algorithms to map unannotated abundance profiles to known protein–organelle associations. Such approaches are likely to make association errors if organelle-related groupings present in experimental output are not included in data used to create a protein–organelle classifier. Currently, there is no automated way to detect organelle-specific clusters within such datasets. In order to address the above issues we adapted a phenotype discovery algorithm, originally created to filter image-based output for RNAi screens, to identify putative subcellular groupings in organelle proteomics experiments. We were able to mine datasets to a deeper level and extract interesting phenotype clusters for more comprehensive evaluation in an unbiased fashion upon application of this approach. Organelle-related protein clusters were identified beyond those sufficiently annotated for use as training data. Furthermore, we propose avenues for the incorporation of observations made into general practice for the classification of protein–organelle membership from quantitative MS experiments. Biological significance Protein sub-cellular localisation plays an important role in molecular interactions, signalling and transport mechanisms. The prediction of protein localisation by quantitative mass-spectrometry (MS) proteomics is a growing field and an important endeavour in improving protein annotation. Several such approaches use gradient-based separation of cellular organelle content to measure relative protein abundance across distinct gradient fractions. The distribution profiles are commonly mapped in silico to known protein–organelle associations via supervised machine learning algorithms, to create classifiers that associate unannotated proteins to specific organelles. These strategies are prone to error, however, if organelle-related groupings present in experimental output are not represented, for example owing to the lack of existing annotation, when creating the protein–organelle mapping. Here, the application of a phenotype discovery approach to LOPIT gradient-based MS data identifies candidate organelle phenotypes for further evaluation in an unbiased fashion. Software implementation and usage guidelines are provided for application to wider protein–organelle association experiments. In the wider context, semi-supervised organelle discovery is discussed as a paradigm with which to generate new protein annotations from MS-based organelle proteomics experiments. This article is part of a Special Issue entitled: New Horizons and Applications for Proteomics [EuPA 2012]

Mapping cells and sub-cellular organelles on 2-D gels: ‘new tricks for an old horse’

AbstractNowadays, investigators in all fields are faced with the identification of unknown, up- or down-regulated, modified proteins that they are trying to identify. Two-dimensional (2-D) gel electrophoresis, with its ability to resolve several thousand proteins, is an extremely powerful technique. The current resolution and reproducibility of 2-D gel technology and the establishment of computer assisted 2-D gel protein databases have paved new ways for the identification of proteins