Researcher studies nervous system development

Ashley Purdy, who recently finished a master’s degree in biology at VCU and is now pursuing her Ph.D., is studying nerve cells in zebrafish in hopes of unlocking secrets about the human nervous system. The research could shed light on how neurodevelopmental disorders like multiple sclerosis or epilepsy occur

Neural development and sensorimotor control

What is the relationship between development of the nervous system and the emergence of voluntary motor behavior? This is the central question of the nature-nurture discussion that has intrigued child psychologists and pediatric neurologists for decades. This paper attempts to revisit this issue. Recent empirical evidence on how infants acquire multi-joint coordination and how children learn to adapt to novel force environments will be discussed with reference to the underlying development of the nervous system. The claim will be made that the developing human nervous system by no means constitutes an ideal controller. However, its redundancy, its ability to integrate multi-modal sensory information and motor commands and its facility of time-critical neural plasticity are features that may prove to be useful for the design of adaptive robots

Confocal analysis of nervous system architecture in direct-developing juveniles of Neanthes arenaceodentata (Annelida, Nereididae)

Background: Members of Family Nereididae have complex neural morphology exemplary of errant polychaetes and are leading research models in the investigation of annelid nervous systems. However, few studies focus on the development of their nervous system morphology. Such data are particularly relevant today, as nereidids are the subjects of a growing body of "evo-devo" work concerning bilaterian nervous systems, and detailed knowledge of their developing neuroanatomy facilitates the interpretation of gene expression analyses. In addition, new data are needed to resolve discrepancies between classic studies of nereidid neuroanatomy. We present a neuroanatomical overview based on acetylated α-tubulin labeling and confocal microscopy for post-embryonic stages of Neanthes arenaceodentata, a direct-developing nereidid. Results: At hatching (2-3 chaetigers), the nervous system has developed much of the complexity of the adult (large brain, circumesophageal connectives, nerve cords, segmental nerves), and the stomatogastric nervous system is partially formed. By the 5-chaetiger stage, the cephalic appendages and anal cirri are well innervated and have clear connections to the central nervous system. Within one week of hatching (9-chaetigers), cephalic sensory structures (e.g., nuchal organs, Langdon's organs) and brain substructures (e.g., corpora pedunculata, stomatogastric ganglia) are clearly differentiated. Additionally, the segmental-nerve architecture (including interconnections) matches descriptions of other, adult nereidids, and the pharynx has developed longitudinal nerves, nerve rings, and ganglia. All central roots of the stomatogastric nervous system are distinguishable in 12-chaetiger juveniles. Evidence was also found for two previously undescribed peripheral nerve interconnections and aspects of parapodial muscle innervation. Conclusions: N. arenaceodentata has apparently lost all essential trochophore characteristics typical of nereidids. Relative to the polychaete Capitella, brain separation from a distinct epidermis occurs later in N. arenaceodentata, indicating different mechanisms of prostomial development. Our observations of parapodial innervation and the absence of lateral nerves in N. arenaceodentata are similar to a 19th century study of Alitta virens (formerly Nereis/Neanthes virens) but contrast with a more recent study that describes a single parapodial nerve pattern and lateral nerve presence in A. virens and two other genera. The latter study apparently does not account for among-nereidid variation in these major neural features

Distribution of α7 Nicotinic Acetylcholine Receptor Subunit mRNA in the Developing Mouse.

Homomeric α7 nicotinic acetylcholine receptors (nAChRs) are abundantly expressed in the central and peripheral nervous system (CNS and PNS, respectively), and spinal cord. In addition, expression and functional responses have been reported in non-neuronal tissue. In the nervous system, α7 nAChR subunit expression appears early during embryonic development and is often transiently upregulated, but little is known about their prenatal expression outside of the nervous system. For understanding potential short-term and long-term effects of gestational nicotine exposure, it is important to know the temporal and spatial expression of α7 nAChRs throughout the body. To that end, we studied the expression of α7 nAChR subunit mRNA using highly sensitive isotopic in situ hybridization in embryonic and neonatal whole-body mouse sections starting at gestational day 13. The results revealed expression of α7 mRNA as early as embryonic day 13 in the PNS, including dorsal root ganglia, parasympathetic and sympathetic ganglia, with the strongest expression in the superior cervical ganglion, and low to moderate levels were detected in brain and spinal cord, respectively, which rapidly increased in intensity with embryonic age. In addition, robust α7 mRNA expression was detected in the adrenal medulla, and low to moderate expression in selected peripheral tissues during embryonic development, potentially related to cells derived from the neural crest. Little or no mRNA expression was detected in thymus or spleen, sites of immune cell maturation. The results suggest that prenatal nicotine exposure could potentially affect the nervous system with limited effects in non-neural tissues

Modelling the spatial organization of cell proliferation in the developing central nervous system

How far is neuroepithelial cell proliferation in the developing central nervous system a deterministic process? Or, to put it in a more precise way, how accurately can it be described by a deterministic mathematical model? To provide tracks to answer this question, a deterministic system of transport and diffusion partial differential equations, both physiologically and spatially structured, is introduced as a model to describe the spatially organized process of cell proliferation during the development of the central nervous system. As an initial step towards dealing with the three-dimensional case, a unidimensional version of the model is presented. Numerical analysis and numerical tests are performed. In this work we also achieve a first experimental validation of the proposed model, by using cell proliferation data recorded from histological sections obtained during the development of the optic tectum in the chick embryo

Modeling of interstitial branching of axonal networks

A single axon can generate branches connecting with plenty synaptic targets. Process of branching is very important for making connections in central nervous system. The interstitial branching along primary axon shaft occurs during nervous system development. Growing axon makes pause in its movement and leaves active points behind its terminal. The new branches appear from these points. We suggest mathematical model to describe and investigate neural network branching process. The model under consideration describes neural network growth in which the concentration of axon guidance molecules manages axon's growth. We model the interstitial branching from axon shaft. Numerical simulations show that in the model framework axonal networks are similar to neural network.Comment: 12 pages, 7 figure

A Pipeline for Volume Electron Microscopy of the Caenorhabditis elegans Nervous System.

The "connectome," a comprehensive wiring diagram of synaptic connectivity, is achieved through volume electron microscopy (vEM) analysis of an entire nervous system and all associated non-neuronal tissues. White et al. (1986) pioneered the fully manual reconstruction of a connectome using Caenorhabditis elegans. Recent advances in vEM allow mapping new C. elegans connectomes with increased throughput, and reduced subjectivity. Current vEM studies aim to not only fill the remaining gaps in the original connectome, but also address fundamental questions including how the connectome changes during development, the nature of individuality, sexual dimorphism, and how genetic and environmental factors regulate connectivity. Here we describe our current vEM pipeline and projected improvements for the study of the C. elegans nervous system and beyond

Tyrosine kinase inhibition produces specific alterations in axon guidance in the grasshopper embryo

Tyrosine kinase signaling pathways are essential for process outgrowth and guidance during nervous system development. We have examined the roles of tyrosine kinase activity in programming growth cone guidance decisions in an intact nervous system in which neurons can be individually identified. We applied the tyrosine kinase inhibitors herbimycin A and genistein to whole 40% grasshopper embryos placed in medium, or injected the inhibitors into intact grasshopper eggs. Both inhibitors caused interneuronal axons that normally would grow along the longitudinal connectives to instead leave the central nervous system (CNS) within the segmental nerve root and grow out toward the body wall muscles. In addition, herbimycin A produced pathfinding errors in which many longitudinal axons crossed the CNS midline. To study how this drug affected guidance decisions made by individual growth cones, we dye-filled the pCC interneuron, which normally extends an axon anteriorly along the ipsilateral longitudinal connective. In the presence of herbimycin A, the pCC growth cone was redirected across the anterior commissure. These phenotypes suggest that tyrosine kinase inhibition blocks a signaling mechanism that repels the growth cones of longitudinal connective neurons and prevents them from crossing the midline

The mechanical control of nervous system development.

The development of the nervous system has so far, to a large extent, been considered in the context of biochemistry, molecular biology and genetics. However, there is growing evidence that many biological systems also integrate mechanical information when making decisions during differentiation, growth, proliferation, migration and general function. Based on recent findings, I hypothesize that several steps during nervous system development, including neural progenitor cell differentiation, neuronal migration, axon extension and the folding of the brain, rely on or are even driven by mechanical cues and forces.This work was supported by the Medical Research CouncilThis is the accepted version of the original publication available at http://dev.biologists.org/content/140/15/3069