Development of the nervous system in the acorn worm Balanoglossus simodensis: insights into nervous system evolution

SUMMARY To examine the evolutionary origin of the chordate nervous system, an outgroup comparison with hemichordates is needed. When the nervous systems of chordates and hemichordates are compared, two possibilities have been proposed, one of which is that the chordate nervous system has evolved from the nervous system of hemichordate‐like larva and the other that it is comparable to the adult nervous system of hemichordates. To address this issue, we investigated the entire developmental process of the nervous system in the acorn worm Balanoglossus simodensis. In tornaria larvae, the nervous system developed along the longitudinal ciliary band and the telotroch, but no neurons were observed in the ventral band or the perianal ciliary ring throughout the developmental stages. The adult nervous system began to develop at the dorsal midline at the Krohn stage, considerably earlier than metamorphosis. During metamorphosis, the larval nervous system was not incorporated into the adult nervous system. These observations strongly suggest that the hemichordate larval nervous system contributes little to the newly formed adult nervous system.     

NPY样免疫反应在蝾螈发育过程中神经系统的定位研究

By immuno-cytochemical method the localization of neuropeptide Y (NPY) in the nervous system during embryonic development of Cynops orientalis was studied. The results revealed that NPY was first localized in the peripheral nervous system (late tail-bud stage), and later appeared in the central nervous system (larval stage) where it appeared with the appearance of glial cells. Very probably with the migration of neural crest cells NPY appeared first in the peripheral nervous system and then distributed to the central nervous system.     

Morphological characteristics of nerves of the vascular plexuses in the lateral cerebral ventricles of human fetuses

The vascular plexus of the lateral ventricle of the human brain includes the microcirculatory bed responsible for the blood supply and liquor production of the organ. Blood capillaries form a thick parviansiform network of the plexus. Innervation of the vascular plexus of the cerebral lateral ventricle in human embryos and fetuses develops synchronously with formation of the plexus itself. The structural complexity of the nervous apparatus increases at the expense of increasing number of nervous fasciculi and single nervous fibers. By the time of birth the nervous apparatus of the plexus acquires a definitive character. After birth further improvement of the nervous apparatus takes place. The role of the microcirculatory bed and of the nervous apparatus of the vascular plexus in ensuring functional loadings and their participation in reactions to certain pathological effects is substantiated.     

Interhemispheric asymmetry and the typological characteristics of the nervous system in rats

The paper is devoted to studies of interrelations between behavioural dominance of the left or right hemisphere and typological characteristics of the nervous system in rats. Rats with a strong type of nervous system are shown to possess species-specific interhemispheric asymmetry. In animals with a balanced nervous system it is greater than in animals with an unbalanced nervous system. Rats with a weak type of nervous system have no species-specific interhemispheric asymmetry.     

Basic proteins of rodent peripheral nerve myelin: immunochemical identification of the 21.5K, 18.5K, 17K, 14K, and P2 proteins

Abstract: Proteins in peripheral nervous system and central nervous system myelin and homogenates of sciatic nerve and brain from young and adult mice and rats were characterized with affinity-purified anti-P₂ and anti-myelin basic protein sera after electrophoretic transfer from sodium dodecyl sulfate-polyacrylamide gels to nitrocellulose sheets. Using this method we have identified a component of rodent peripheral nervous system myelin as P₂ protein. Peripheral nervous system myelin also showed the presence of four basic proteins in addition to P₂ protein. These were found to be analogous to the 14, 17, 18.5, and 21.5K species found in the central nervous system myelin. A number of high-molecular-weight proteins were also detected with anti-myelin basic protein serum in peripheral nervous system, as well as central nervous system myelin. In addition, we report the presence of a high-molecular-weight P₂ cross-reactive protein in rodent brain stem homogenates, but not in central nervous system myelin.     

Nervous system development of the sea cucumber Stichopus japonicus

The nervous system development of the sea cucumber Stichopus japonicus was investigated to explore the development of the bilateral larval nervous system into the pentaradial adult form typical of echinoderms. The first nerve cells were detected in the apical region of epidermis in the late gastrula. In the auricularia larvae, nerve tracts were seen along the ciliary band. There was a pair of bilateral apical ganglia consisted of serotonergic nerve cells lined along the ciliary bands. During the transition to the doliolaria larvae, the nerve tracts rearranged together with the ciliary bands, but they were not segmented and remained continuous. The doliolaria larvae possessed nerves along the ciliary rings but strongly retained the features of auricularia larvae nerve pattern. The adult nervous system began to develop inside the doliolaria larvae before the larval nervous system disappears. None of the larval nervous system was observed to be incorporated into the adult nervous system with immunohistochemistry. Since S. japonicus are known to possess an ancestral mode of development for echinoderms, these results suggest that the larval nervous system and the adult nervous system were probably formed independently in the last common ancestor of echinoderms.     

Nervous system of the extraembryonic organs of the white rat fetus

Nervous apparatuses of the fetal membranes have been studied in white rats on the 18th-19th days of embryogenesis. Experimental hypoxia, novocaine and potassium chloride solutions effect ensure better revealing of the nervous system elements. At supravital staining with mythelene blue and at impregnation with silver nitrate, nervous fibers are revealed in the distal part of the umbilical cord and in the placental chorional plate. In the labyrinth part of the placenta certain nervous terminals are revealed. In the amnion certain nervous fibers and terminals are found both in the connective tissue and in the epithelium. On the omphaloplacenta vessels numerous nervous apparatuses are detected. A conclusion is made that at the end of embryogenesis the fetal membranes in the white rats are abundantly innervated. This demonstrates nervous regulation of the fetal membranes functions and of interrelationships of the fetus and the maternal organism.     

Radiation physiology of higher nervous activity: results and perspectives

Reflex forming and stabilization, the typological peculiarities of the experimental animals' higher nervous activity were discussed. The problems of the central nervous system functional reactions to irradiation in small doses, the chronic irradiation in particular, influence to higher nervous activity of heavy particles irradiation and neurochemical mechanisms of the disturbances in the central nervous system require further experimental investigations.     

Reorganization of the nervous system during regeneration in Dugesia tigrina]

The normal structure of the nervous system in Dugesia tigrina Girard and the total morphodynamics of the nervous system during regeneration have been studied by means of choline esterase assay. The nervous system reacts to local damages of the planarian body; accumulations of nervous elements form in the wound region. Following the transverse cut of a planarian, the regeneration of the nervous system is not reduced to the completion of lacking parts. In this case (as well as in that of asexual reproduction) the nervous system manifests a considerable morphological lability and undergoes morphological rearrangements accompanied by the appearance of additional, frequently unpaired, nerve trunks. The data obtained are to be taken into account in neurobiological studies on planarians.     

Development of the neural and tissue components of the excretory ducts of the liver, pancreas and Odd's sphincter in human embryogeny]

The development of pancreatic, hepatic, cystic, common bile ducts, the Oddi's sphincter and their nervous apparatus were studied during prenatal human ontogenesis of fetuses and newborns. The process of formation of the nervous apparatus corresponds to the development of tissue structures of the ducts and the sphincter. The distinctions in the organization of nervous elements which are noted in adult humans are laid in the process of embryogenesis. These distinctions are especially pronounced in the structure of nervous plexuses and receptory endings. The nervous apparatus of the Oddi's sphincter region has a complex arrangement. This is the site of concentration of nerve nodules and receptory endings as well as abundant nervous connections between plexuses of the pancreatic head, duodenum and orifice zones of the both ducts. The receptors in nerve nodules and pericellular apparatuses on the bodies of ganglionic neurons were revealed.     

Role of gangliosides in the processes of calcium ion transport across the membranes of nerve cells

It has been demonstrated that the content of extracellular Ca in the nervous system is inversely related to the content of gangliosides. The results obtained on invertebrates, lower and higher vertebrates indicate that the highest content of extracellular Ca is typical of the nervous tissue of invertebrates, whereas the lower one--of the nervous tissue of higher vertebrates (mammals). Ganglioside content, on the contrary, is the highest in the brain tissue of the higher vertebrates (mammals and birds), being significantly lower in lower vertebrates; no gangliosides was found at all in the nervous tissue of protostomian invertebrates. The highest ganglioside content in the organism of vertebrates is characteristic to the surface membranes of the nervous cells, especially in the region of synapses. Functional significance of the inverse relationship between the content of extracellular Ca and gangliosides is discussed from the standpoint of one of the authors (R. Veh) who postulated the existence of calcium--ganglioside buffer in the vicinity of the surface of the nervous cells.     

The history of the theory of nervous trophism]

Concepts "trophism" and "nervous trophism", development of views on trophic function of the nervous system and its disorders (neurogenic dystrophies) are reviewed. The problem on the ways of the trophic effects of the nervous system on the tissues is considered. The role of neuromediators in this process, particularly the significance of balance of norepinephrine, (NE), a mediator of the sympathetic nervous system (SNS), for maintaining trophism of tissues, their structure and functions is emphasized. The activating role of SNS and NE in the resistance and reparative regeneration of different tissues is shown under the experimental and clinical conditions. In this view a comprehensive definition of concepts "nervous trophism" is given.     

Comparative characterization of the nervous system of the Turbellaria

Initial stages of the centralization of the nervous apparatus in the Turbellaria can be traced through a comparison of the structure of the nervous system in various representatives of the class. The most primitive state, found in the Acoela, is predominantly plexiform with a varying number of longitudinal trunks. Three, and in some cases four, longitudinal trunks are found in the Proseriata and Temnocephalida. Commissures appear in the Macrostomida and all higher orders and form an orthogon. Brain shape varies from ring-shaped in the Acoela to bilobed in the Neorhabdocoela. While the nervous system of the Polycladida is peculiar, having numerous lateral trunks and separation of dorsal and ventral parts of the nervous system, the development of the nervous system in Müller's larvae of polyclads shows it is of an orthogonal type comparable to other platyhelminths. Transition to parasitism is accompanied by some progressive transformations in the structure of the nervous system.     

家蚕神经系统研究进展

家蚕Bombyx mori神经系统属于腹神经索型, 构造简单, 却能产生丰富的行为, 是研究神经生物学的理想实验材料。研究表明： 家蚕神经系统由中枢神经系统、 外周神经系统和交感神经系统构成, 通过信号传递在调节家蚕视觉、 嗅觉、 取食、 结茧、 交配、 排泄等生命活动中发挥作用。家蚕具有编码乙酰胆碱、 γ-氨基丁酸、 多巴胺等多种神经递质及其受体和促前胸腺激素（prothoracicotropic hormone, PTTH）、 滞育激素（diapause hormone, DH）等神经肽的基因。家蚕神经系统发育受到许多基因和bmo-miR-92等小分子RNA的调控。目前研究家蚕神经的方法主要有触角电位技术、 免疫细胞化学法、 转基因方法、 神经信息学及计算机三维重建等。对家蚕神经系统的研究有助于阐明神经系统的信号传递机制和生物神经网络的形成机制。     

Ultrastructural bases of the development of the neural apparatus of the heart

By means of electron microscopy developmental dynamics of the human and mammalian innervation has been studied during prenatal period of ontogenesis. Regularities in formation of the intracardiac nervous ganglia and in differentiation of nervous-muscular connections in the myocardium have been stated. Ultrastructural peculiarities of proneuroblasts and the nervous fiber terminals, growing to differentiating cardiomyocytes have been described during the premediator stage of the vegetative nervous system development. Peculiarities of synaptogenesis have been followed, among them those demonstrated as heterochromic formation of pre- and post-synaptic membrane and as uneven accumulation of synaptic vesicles. Development of the nervous-muscular connections have been studied. At the beginning of the mediator stage of the vegetative nervous system development formation of simple contacts between the nervous terminals and cardiomyocytes is intensified, and glial tunics develop rather poorly. Therefore, at the beginning the terminal parts of axons are not surrounded with processes of gliocytes. Simultaneously, formation of small intensively luminescent cells takes place. Development of afferent nervous terminals occurs not only in the myocardium, but in the intracardiac ganglia.     

Morphodynamics of the nervous system in the regenerative processes of Convoluta convoluta (Turbellaria, Acoela)]

By means of the method for revealing cholinesterases the alterations in the nervous system of Convoluta convoluta after mechanical lesion were studied. After a transversal transection of the animal into two pieces the anterior part of the body acquired the normal form within 3-4 days; the nervous system underwent inconsiderable transformations associated with a formation of a plexus in the injured area. The posterior parts of the body regenerated slowly. During the first days disintegration of the resting parts of the nervous system was observed. Later on the diffuse cholinesterase activity suggesting the beginning of the brain formation was manifested in the wound field. Plexus strands "grow" in the caudal direction from the brain in parallel with its development. Within three weeks the nervous system of the animals which had restored their mouth opening, body shape and normal behaviour consists of the brain and plexus not arranged in nervous trunks. The reaction of the nervous system to the ablation of a part of the brain and to a continuous mechanical injury were studied. The data obtained show a high morphological lability of the nervous system of Convoluta convoluta, its ability to radical structural rearrangements.     

A gene catalogue of the amphioxus nervous system

The elaboration of extremely complex nervous systems is a major success of evolution. However, at the dawn of the post-genomic era, few data have helped yet to unravel how a nervous system develops and evolves to complexity. On the evolutionary road to vertebrates, amphioxus occupies a key position to tackle this exciting issue. Its "simple" nervous system basically consists of a dorsal nerve cord and a diffuse net of peripheral neurons, which contrasts greatly with the complexity of vertebrate nervous systems. Notwithstanding, increasing data on gene expression has faced up this simplicity by revealing a mounting level of cryptic complexity, with unexpected levels of neuronal diversity, organisation and regionalisation of the central and peripheral nervous systems. Furthermore, recent gene expression data also point to the high neurogenic potential of the epidermis of amphioxus, suggestive of a skin-brain track for the evolution of the vertebrate nervous system. Here I attempt to catalogue and synthesise current gene expression data in the amphioxus nervous system. From this global point of view, I suggest scenarios for the evolutionary origin of complex features in the vertebrate nervous system, with special emphasis on the evolutionary origin of placodes and neural crest, and postulate a pre-patterned migratory pathway of cells, which, in the epidermis, may represent an intermediate state towards the deployment of one of the most striking innovative features of vertebrates: the neural crest and its derivatives.     

The effects of ionic lanthanum and hypertonic physiological salines on the nervous systems of larval and adult stick insects.

The effects of the electron-opaque tracer ionic lanthanum in various concentrations and of hyperosmotic physiological salines on the nervous system of the stick insect, Carausius morosus, have been studied. Examination of the experimentally treated tissues revealed that the diffusion barrier to the exogenous tracer was maintained in all cases in the adult central and peripheral nervous systems, but not in the hatchling. When hatchling nervous tissues were incubated in 50 mM ionic lanthanum in phyerosmotic physiological saline, the tracer readily infiltrated all the extracellular spaces between axons and glia of all components of the nervous system examined. No difference was noted in this regard between fed and unfed hatchlings, Further, in all cases examined of adults and hatchlings, lanthanum readily surrounded those neurosecretory axons which are found in the neutral lamella, or extracellular nerve sheath, of the insect. The possible meanings of these variations in hatchling and adult nervous systems and in the accessibility of different elements of the nervous system to exogenous ionic lanthanum are discussed.     

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.