Expression of Semaphorins, Neuropilins, VEGF, and Tenascins in Rat and Human Primary Sensory Neurons after a Dorsal Root Injury

Dorsal root injury is a situation not expected to be followed by a strong regenerative growth, or growth of the injured axon into the central nervous system of the spinal cord, if the central axon of the dorsal root is injured but of strong regeneration if subjected to injury to the peripherally projecting axons. The clinical consequence of axonal injury is loss of sensation and may also lead to neuropathic pain. In this study, we have used in situ hybridization to examine the distribution of mRNAs for the neural guidance molecules semaphorin 3A (SEMA3A), semaphorin 3F (SEMA3F), and semaphorin 4F (SEMA4F), their receptors neuropilin 1 (NP1) and neuropilin 2 (NP2) but also for the neuropilin ligand vascular endothelial growth factor (VEGF) and Tenascin J1, an extracellular matrix molecule involved in axonal guidance, in rat dorsal root ganglia (DRG) after a unilateral dorsal rhizotomy (DRT) or sciatic nerve transcetion (SNT). The studied survival times were 1-365 days. The different forms of mRNAs were unevenly distributed between the different size classes of sensory nerve cells. The results show that mRNA for SEMA3A was diminished after trauma to the sensory nerve roots in rats. The SEMA3A receptor NP1, and SEMA3F receptor NP2, was significantly upregulated in the DRG neurons after DRT and SNT. SEMA4F was upregulated after a SNT. The expression of mRNA for VEGF in DRG neurons after DRT showed a significant upregulation that was high even a year after the injuries. These data suggest a role for the semaphorins, neuropilins, VEGF, and J1 in the reactions after dorsal root lesions

Conduction in ulnar nerve bundles that innervate the proximal and distal muscles: a clinical trial

<p>Abstract</p> <p>Background</p> <p>This study aims to investigate and compare the conduction parameters of nerve bundles in the ulnar nerve that innervates the forearm muscles and hand muscles; routine electromyography study merely evaluates the nerve segment of distal (hand) muscles.</p> <p>Methods</p> <p>An electrophysiological evaluation, consisting of velocities, amplitudes, and durations of ulnar nerve bundles to 2 forearm muscles and the hypothenar muscles was performed on the same humeral segment.</p> <p>Results</p> <p>The velocities and durations of the compound muscle action potential (CMAP) of the ulnar nerve bundle to the proximal muscles were greater than to distal muscles, but the amplitudes were smaller.</p> <p>Conclusions</p> <p>Bundles in the ulnar nerve of proximal muscles have larger neuronal bodies and thicker nerve fibers than those in the same nerve in distal muscles, and their conduction velocities are higher. The CMAPs of proximal muscles also have smaller amplitudes and greater durations. These findings can be attributed to the desynchronization that is caused by a wider range of distribution in nerve fiber diameters.</p> <p>Conduction parameters of nerve fibers with different diameters in the same peripheral nerve can be estimated.</p

Context-aware modeling of neuronal morphologies

© 2014 Torben-Nielsen and De Schutter. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these termsNEURONAL MORPHOLOGIES ARE PIVOTAL FOR BRAIN FUNCTIONING: physical overlap between dendrites and axons constrain the circuit topology, and the precise shape and composition of dendrites determine the integration of inputs to produce an output signal. At the same time, morphologies are highly diverse and variant. The variance, presumably, originates from neurons developing in a densely packed brain substrate where they interact (e.g., repulsion or attraction) with other actors in this substrate. However, when studying neurons their context is never part of the analysis and they are treated as if they existed in isolation. Here we argue that to fully understand neuronal morphology and its variance it is important to consider neurons in relation to each other and to other actors in the surrounding brain substrate, i.e., their context. We propose a context-aware computational framework, NeuroMaC, in which large numbers of neurons can be grown simultaneously according to growth rules expressed in terms of interactions between the developing neuron and the surrounding brain substrate. As a proof of principle, we demonstrate that by using NeuroMaC we can generate accurate virtual morphologies of distinct classes both in isolation and as part of neuronal forests. Accuracy is validated against population statistics of experimentally reconstructed morphologies. We show that context-aware generation of neurons can explain characteristics of variation. Indeed, plausible variation is an inherent property of the morphologies generated by context-aware rules. We speculate about the applicability of this framework to investigate morphologies and circuits, to classify healthy and pathological morphologies, and to generate large quantities of morphologies for large-scale modeling.Peer reviewe

Locomotor rhythm maintenance: electrical coupling among premotor excitatory interneurons in the brainstem and spinal cord of young Xenopus tadpoles

Electrical coupling is important in rhythm generating systems. We examine its role in circuits controlling locomotion in a simple vertebrate model, the young Xenopus tadpole, where the hindbrain and spinal cord excitatory descending interneurons (dINs) that drive and maintain swimming have been characterised. Using simultaneous paired recordings, we show that most dINs are electrically coupled exclusively to other dINs (DC coupling coefficients ∼8.5%). The coupling shows typical low-pass filtering. We found no evidence that other swimming central pattern generator (CPG) interneurons are coupled to dINs or to each other. Electrical coupling potentials between dINs appear to contribute to their unusually reliable firing during swimming. To investigate the role of electrical coupling in swimming, we evaluated the specificity of gap junction blockers (18-β-GA, carbenoxolone, flufenamic acid and heptanol) in paired recordings. 18-β-GA at 40–60 μm produced substantial (84%) coupling block but few effects on cellular properties. Swimming episodes in 18-β-GA were significantly shortened (to ∼2% of control durations). At the same time, dIN firing reliability fell from nearly 100% to 62% of swimming cycles and spike synchronization weakened. Because dINs drive CPG neuron firing and are critical in maintaining swimming, the weakening of dIN activity could account for the effects of 18-β-GA on swimming. We conclude that electrical coupling among pre motor reticulospinal and spinal dINs, the excitatory interneurons that drive the swimming CPG in the hatchling Xenopus tadpole, may contribute to the maintenance of swimming as well as synchronization of activity

Debris clearance by microglia: an essential link between degeneration and regeneration

Microglia are cells of myeloid origin that populate the CNS during early development and form the brain's innate immune cell type. They perform homoeostatic activity in the normal CNS, a function associated with high motility of their ramified processes and their constant phagocytic clearance of cell debris. This debris clearance role is amplified in CNS injury, where there is frank loss of tissue and recruitment of microglia to the injured area. Recent evidence suggests that this phagocytic clearance following injury is more than simply tidying up, but instead plays a fundamental role in facilitating the reorganization of neuronal circuits and triggering repair. Insufficient clearance by microglia, prevalent in several neurodegenerative diseases and declining with ageing, is associated with an inadequate regenerative response. Thus, understanding the mechanism and functional significance of microglial-mediated clearance of tissue debris following injury may open up exciting new therapeutic avenues

Научно-исследовательская, культурно-массовая, физкультурно-спортивная и общественная деятельность студентов как факторы успешности их учебно-познавательного процесса

Материалы IV Респ. науч.-метод. конф., посвящ. 120-летию со дня рождения П. О. Сухого, Гомель, 29–30 окт. 2015 г