Neural marker genes differently expressed in subsets of embryonic neural cells of the ascidian Halocynthia roretzi

Ascidians are lower chordates that possess a possible prototype of the vertebrate nervous system. The central and peripheral nervous systems of ascidian larvae are composed of only a few hundred cells (Nicol and Meinertzhagen, 1991). To investigate how these ascidian nervous systems develop, dissection at the molecular level using subset-specific markers is essential. Here we describe four new genes zygotically expressed in subsets of the ascidian neural cells. The spatial expression domains of these genes overlap in some parts but not in other parts of the nervous systems. Our results suggest that there are functionally different regions in the nervous systems owing to the gene expression differences. Further analyses of these genes will enable us to determine the molecular neuro-developmental characteristics of various clusters of neural cells.     

A comparative analysis of neural taste processing in animals

Understanding taste processing in the nervous system is a fundamental challenge of modern neuroscience. Recent research on the neural bases of taste coding in invertebrates and vertebrates allows discussion of whether labelled-line or across-fibre pattern encoding applies to taste perception. While the former posits that each gustatory receptor responds to one stimulus or a very limited range of stimuli and sends a direct 'line' to the central nervous system to communicate taste information, the latter postulates that each gustatory receptor responds to a wider range of stimuli so that the entire population of taste-responsive neurons participates in the taste code. Tastes are represented in the brain of the fruitfly and of the rat by spatial patterns of neural activity containing both distinct and overlapping regions, which are in accord with both labelled-line and across-fibre pattern processing of taste, respectively. In both animal models, taste representations seem to relate to the hedonic value of the tastant (e.g. palatable versus non-palatable). Thus, although the labelled-line hypothesis can account for peripheral taste processing, central processing remains either unknown or differs from a pure labelled-line coding. The essential task for a neuroscience of taste is, therefore, to determine the connectivity of taste-processing circuits in central nervous systems. Such connectivity may determine coding strategies that differ significantly from both the labelled-line and the across-fibre pattern models.     

Early development of the central and peripheral nervous systems is coordinated by Wnt and BMP signals

The formation of functional neural circuits that process sensory information requires coordinated development of the central and peripheral nervous systems derived from neural plate and neural plate border cells, respectively. Neural plate, neural crest and rostral placodal cells are all specified at the late gastrula stage. How the early development of the central and peripheral nervous systems are coordinated remains, however, poorly understood. Previous results have provided evidence that at the late gastrula stage, graded Wnt signals impose rostrocaudal character on neural plate cells, and Bone Morphogenetic Protein (BMP) signals specify olfactory and lens placodal cells at rostral forebrain levels. By using in vitro assays of neural crest and placodal cell differentiation, we now provide evidence that Wnt signals impose caudal character on neural plate border cells at the late gastrula stage, and that under these conditions, BMP signals induce neural crest instead of rostral placodal cells. We also provide evidence that both caudal neural and caudal neural plate border cells become independent of further exposure to Wnt signals at the head fold stage. Thus, the status of Wnt signaling in ectodermal cells at the late gastrula stage regulates the rostrocaudal patterning of both neural plate and neural plate border, providing a coordinated spatial and temporal control of the early development of the central and peripheral nervous systems.     

Experimental nerve imaging at 1.5-T

Experimental lesions of the peripheral nerve system can be visualized in vivo by magnetic resonance imaging (MRI). Many studies of the rat peripheral nervous systems were performed on dedicated animal MR scanners with a high magnetic field strength for good spatial resolution. Here, we present an MR protocol to study experimental lesions of the rat nervous system with clinical 1.5-T MR scanners and commercially available coils. Using a three-sequence approach (T1-weighted imaging, fat-saturated T2-weighted imaging and fat-saturated T1-weighted imaging with Gd-DTPA in the same plane), the relevant signal changes of the lesioned nerve can be visualized and separated from other structures, e.g., blood vessels. Furthermore, we give an overview on different types of contrast agents used for peripheral nerve MR imaging and MR findings in selected experimental models of rat peripheral nerve injury.     

Isolation of an early neural maker gene abundantly expressed in the nervous system of the ascidian, Halocynthia roretzi

Ascidian tadpole larvae possess a primitive nervous system, which is a prospective prototype of the chordate nervous system. It is composed of relatively few cells but sufficient for complex larval behavior. Here we report on HrETR-1, a gene zygotically expressed in a large proportion of the developing neural cells of the ascidian, Halocynthia roretzi. HrETR-1 is an early neural marker which can be used for analyzing neural differentiation. HrETR-1 expression intensified in most neural cells of genes isolated to date, in both central and peripheral nervous systems including palps as early as the 110-cell stage. Using this gene as a probe, we characterized neural cells in the nervous system as well as confirming their origins. Also, we recognized three types of peripheral epidermal neurons which presumably correlate to the larval neurons previously reported for another ascidian. Among these, five bilateral neurons located in the anterior region of the trunk appeared to be derived from a8.26 blastomeres.     

Zooming in on biological processes with fluorescence nanoscopy

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Highlights► Fluorescence nanoscopy can be used to decipher subcellular structures in biological systems. ► We review the underlying principles and biological application of STED, PALM, and STORM. ► For super-resolution imaging methods, there is a tradeoff between temporal and spatial resolution. ► Improving probe brightness and probe photostability are key factors for achieving higher resolution.     

Sex differences in microRNA regulation of gene expression: no smoke, just miRs

Sexual differentiation of the nervous system occurs via the interplay of genetics, endocrinology and social experience through development. Much of the research into mechanisms of sexual differentiation has been driven by an implicit theoretical framework in which these causal factors act primarily and directly on sexually dimorphic neural populations within the central nervous system. This review will examine an alternative explanation by describing what is known about the role of peripheral structures and mechanisms (both neural and non-neural) in producing sex differences in the central nervous system. The focus of the review will be on experimental evidence obtained from studies of androgenic masculinization of the spinal nucleus of the bulbocavernosus, but other systems will also be considered.     

Possible microwave mechanisms of the mammalian nervous system

The hypothesis is examined that the living mammal generates and uses electromagnetic waves in the lower microwave frequency region as an integral part of the functioning of central and peripheral nervous systems. Analysis of the potential energy of a protein integral to the neural membrane compared to that of an extracellular positive ion yields major known features of action potential generation, and identification of the integral protein as a microwave emitter and absorber by changes in rotational energy state. Prolate spheroidal analysis of the adult human brain/skull cavity shows capability to support modes in the range 200 MHz to 3 GHz; spatial mode properties correspond to gross anatomy and neuromorphology of the brain. Phase-lock loop interaction between lower microwave modes and action potential conduction results in pulse microwave/action potential generation observable by EEG instrumentation as brain waves; alpha waves occur if the corpus callosum is the major neural tract involved. Spatially consistent Lorentz forces of standing microwaves provide physical basis for correspondence of spatial properties of microwave modes with brain anatomy, and for the formation of myelin sheath and the nodes of Ranvier on larger neurons.     

Microscopic localization of cholinesterases in the nervous systems of the lobsters, Panulirus argus and Homarus americanus

Using acetylthiocholine as substrate, microscopically localizable cholinesterase (ChE) activity is demonstrated in neural and glial elements of central and peripheral nervous systems of the lobsters, Panulirus argus and Homarus americanus. Moderate to very intense ChE activity occurs in all synaptic regions of the central ganglia and stomatogastric ganglion, in glial sheaths around neuron somata and peripheral nerve axons, and in cytoplasm of a few nerve cell bodies. Axons, identified as motor, contain extremely little ChE. The principal reaction in peripheral nerves occurs in sheath elements of sensory fibres; in most cases, much of the reaction is lost as the nerves lose the sheaths at the point of entry into brain.     

Neural crest and placode interaction during the development of the cranial sensory system

In the vertebrate head, the peripheral components of the sensory nervous system are derived from two embryonic cell populations, the neural crest and cranial sensory placodes. Both arise in close proximity to each other at the border of the neural plate: neural crest precursors abut the future central nervous system, while placodes originate in a common preplacodal region slightly more lateral. During head morphogenesis, complex events organise these precursors into functional sensory structures, raising the question of how their development is coordinated. Here we review the evidence that neural crest and placode cells remain in close proximity throughout their development and interact repeatedly in a reciprocal manner. We also review recent controversies about the relative contribution of the neural crest and placodes to the otic and olfactory systems. We propose that a sequence of mutual interactions between the neural crest and placodes drives the coordinated morphogenesis that generates functional sensory systems within the head.     

Identity, origin, and migration of peripheral glial cells in the Drosophila embryo

Glial cells are crucial for the proper development and function of the nervous system. In the Drosophila embryo, the glial cells of the peripheral nervous system are generated both by central neuroblasts and sensory organ precursors. Most peripheral glial cells need to migrate along axonal projections of motor and sensory neurons to reach their final positions in the periphery. Here we studied the spatial and temporal pattern, the identity, the migration, and the origin of all peripheral glial cells in the truncal segments of wildtype embryos. The establishment of individual identities among these cells is reflected by the expression of a combinatorial code of molecular markers. This allows the identification of individual cells in various genetic backgrounds. Furthermore, mutant analysis of two of these marker genes, spalt major and castor, reveal their implication in peripheral glial development. Using confocal 4D microscopy to monitor and follow peripheral glia migration in living embryos, we show that the positioning of most of these cells is predetermined with minor variations, and that the order in which cells migrate into the periphery is almost fixed. By studying their lineages, we uncovered the origin of each of the peripheral glial cells and linked them to identified central and peripheral neural stem cells.     

低强度聚焦超声对中枢神经调控作用研究进展

利用导入神经回路内电、磁、光、声等物理因子作用来激发神经系统功能活性,进而改善神经疾病症状、提高生命质量的神经调控技术(neural control technology)在生命科学研究和医学临床诊疗中得到广泛应用.其中尤以低强度聚焦超声(low intensity focused ultrasound,LIFU)具有非损伤性、高穿透能力与时空分辨等优势,更适合用作安全的神经调控物理刺激因子.目前LIFU用于神经调控研究已受到科学界高度关注,进行了大量动物与人类神经调控实验研究并取得可喜成果.本文分别从LIFU用于动物与人类中枢神经调控研究进展、神经调控机制、安全性问题和未来应用前景等方面介绍评述,以期为神经调控研究与应用提供参考.     

Insights into new techniques for high resolution functional MRI

Non-invasive functional magnetic resonance imaging (fMRI) has opened a unique window into human and animal brain function, with a spatial resolution of a few millimeters and a temporal resolution of a few seconds. To further improve the current technical limitations of fMRI, various post-processing and data acquisition schemes were developed. Improved fMRI methods include variations of a conventional fMRI technique, mapping a single physiological parameter such as cerebral blood flow or cerebral blood volume, and direct mapping of neural activity. Advances in fMRI techniques allow scientists to map submillimeter columnar and laminar functional structures and to detect tens of millisecond neural activity in certain specific tasks.     

Neurogenic contractile activity of the penis retractor muscle of Helix pomatia L.

Using convential mechanical and electromyographic recording methods 2 distinct types of neurogenically elicited activity can be observed in the penis retractor muslce (PRM) of Helix pomatia: (1) rhythmic, phasic contractions correlated with single or a few compound action potentials and (2) intervening, strong, prolonged contractions accompanied by sustained, high frequency electrical muscle activity. The 2 distinct types of muscle activity which seem to play a part in the normal behaviour of the PRM in the intact animal are mediated by both the central nervous system and peripheral neurons. While central neuronal structures are involved in causing the strong, prolonged contractions, the phasic activity is initiated by peripheral neuronal structures located at the proximal end of the PRM. There is evidence that the transmission of the excitation at the neuromuscular level of central and peripheral origin is mediated by ACh.     

Stimulating neurons with light

Recent technological advances have enabled the use of different optical methods to activate neurons, including 'caged' glutamate, photoactivation of genetically engineered cascades, and direct two-photon excitation. The ability to use light as a stimulation tool provides, in principle, a non-invasive method for the temporally and spatially precise activation of any neuron or any part of a neuron. When combined with two-photon excitation, excellent spatial control can be achieved even in complex and highly scattering preparations, such as living nervous tissue. Different methods that have been developed in the last several decades have been used to probe neuronal sensitivity, mimic synaptic input, and elucidate patterns of neural connectivity.     

Peptidergic pathways in the avian brain

The results obtained by topographical studies on the immunoreactive peptide systems in the embryonic and adult avian brain (domestic fowl, domestic mallard, pigeon, Japanese quail, and zebra finch) can be realized only by means of phylogenetical comparisons. The comparative studies mainly demonstrate a fascinating constancy of the immunological properties and the spatial distribution of the neuropeptides. Independent of the development of the neopallium, and the increasing cerebral complexity, the spatial distribution of the neuropeptides, the location of their main perikaryal accumulations which are interconnected by immunoreactive fiber projections (and thereby forming widespread but continuous peptide systems) remain nearly unchanged during vertebrate evolution. The recognition of the neuropeptides as integral parts of the central nervous system is demonstrated by the fact that neuropeptidergic structures connect sensory inputs with central nervous areas as well as with the peripheral endocrinium.     

Large-scale characterization of genes specific to the larval nervous system in the ascidian Ciona intestinalis

The central and peripheral nervous systems (CNS and PNS) of the ascidian tadpole larva are comparatively simple, consisting of only about 350 cells. However, studies of the expression of neural patterning genes have demonstrated overall similarity between the ascidian CNS and the vertebrate CNS, suggesting that the ascidian CNS is sufficiently complex to be relevant to those of vertebrates. Recent progress in the Ciona intestinalis genome project and cDNA project together with considerable EST information has made Ciona an ideal model for investigating molecular mechanisms underlying the formation and function of the chordate nervous system. Here, we characterized 56 genes specific to the nervous system by determining their full-length cDNA sequences and confirming their spatial expression patterns. These genes included those that function in the nervous systems of other animals, especially those involved in photoreceptor-mediated signaling and neurotransmitter release. Thus, the nervous system-specific genes in Ciona larvae will provide not only probes for determining their function but also clues for exploring the complex network of nervous system-specific genes.     

Expression of human immunodeficiency virus type 1 in the nervous system of transgenic mice leads to neurological disease.

Patients infected with the human immunodeficiency virus type 1 (HIV-1) frequently develop central and peripheral nervous system complications, some of which may reflect the effect of the virus itself. In order to elucidate the pathogenic mechanisms of HIV in neurological disease in a small animal model, we generated transgenic mice expressing the entire HIV genome under control of the promoter for the human neurofilament NF-L gene. The transgene was predominantly expressed in anterior thalamic and spinal motor neurons. Animals developed a neurological syndrome characterized by hypoactivity and weakness and by axonal degeneration in peripheral nerves. These results provide evidence for a role of HIV in affecting both the central and peripheral nervous systems. This animal model may also facilitate the development of therapeutic agents against the human disease.