Ultrastructure of the circumoral nerve ring and the radial nerve cords in holothurians (Echinodermata)

The circumoral nerve ring and the radial nerve cords (RNCs) of Eupentacta fraudatrix and Pseudocnus lubricus (Holothuroidea) were examined as an example of holothurian nervous tissue. The RNC is composed of outer ectoneural and inner hyponeural layers, which are interconnected with one another via short neural bridges. The circumoral nerve ring is purely ectoneural. Both ectoneural and hyponeural components are epithelial tubes with a thick neuroepithelium at one side. A thin ciliated non-neuronal epithelium complements the neuroepithelium to form a tube, thereby enclosing the epineural and hyponeural canals. The whole of the ectoneural and hyponeural subsystems is separated from the surrounding tissue by a continuous basal lamina. The nerve ring and the ectoneural and hyponeural parts of the radial nerves are all neuroepithelia composed of supporting cells and neurons. Supporting cells are interpreted as being glial cells. Based on ultrastructural characters, three types of neurons can be distinguished: (1) putative primary sensory neurons, whose cilium protrudes into the epineural or hyponeural canal; (2) non-ciliated neurons with swollen rough endoplasmic reticulum cisternae; (3) monociliated neurons that are embedded in the trunk of nerve fibers. Different types of synapses occur in the neuropile area. They meet all morphological criteria of classical chemical synapses. Vacuolated cells occur in the neuroepithelium of E. fraudatrix, but are absent in P. lubricus; their function is unknown. The cells of the non-neuronal epithelia that overlie the ectoneural and hyponeural canals are hypothesized to belong to the same cell type as the supporting cells of the neuroepithelium.     

NADPH-diaphorase localization in the radial nerve cords of the starfish Patiria pectinifera

The presence and localization of NADPH-diaphorase (NADPH-d) in the radial nerve cords of Patiria pectonifera was shown by electron histochemistry. NADPH-d-positive structures were found in ectoneural and hyponeural regions of the radial nerve cord. Ultrastructural localization of NADPH-d was detected in neurons, sensory cells, supporting cells, and in the nerve plexus. The highest enzymatic activity in ectoneural region of the radial nerve cord is due, presumably, to the involvement of NADPH in sensory signal processing.     

Morphogenesis and organogenesis in the regenerating planktotrophic larvae of asteroids and echinoids

In a previous study, we described complete body regeneration (with organogenesis) following surgical bisection in the planktotrophic larvae of the asteroids Luidia foliolata and Pisaster ochraceus. Here we present further detailed observations of these unique regenerative processes not presented in the previous paper. Furthermore, we describe for the first time complete regeneration following surgical bisection of planktotrophic larvae of the regular echinoid Lytechinus variegatus and the irregular echinoid Dendraster excentricus. Larvae of both asteroids and echinoids displayed a capacity for rapid regeneration regardless of their developmental stage. Within 48 h after bisection, aggregations of mesenchyme cells with pseudopodia were observed at the site of surgical bisection. These cellular aggregations were similar in appearance to the mesenchymal blastemas that form in adult echinoderms prior to their arm regeneration, and to those described in other deuterostomes that undergo regeneration. When asteroid larvae were surgically bisected in the early stages of their development, clusters of mesenchyme cells developed into completely new pairs of coelomic pouches located anterior to the newly regenerated digestive tract. This indicates that cell fate in regenerating asteroid larvae remains indeterminate during early development. In the larvae of P. ochraceus, regardless of the developmental stage at the time of bisection, both the anterior and posterior portions regenerated all their missing organs and tissues. However, the larvae of L. foliolata displayed differential regenerative capacity in bisected larval halves at the late bipinnaria stage. The differences observed may be due to differences in larval development (L. foliolata has no brachiolaria stage), and may have evolutionary implications. In the regular echinoid L. variegatus, both larval portions regenerated into morphologically and functionally normal larvae that were indistinguishable from non-bisected control larvae. The regenerative processes were similar to those we observed in planktotrophic asteroid larvae. Regenerating larvae readily metamorphosed into normal juveniles. In the irregular echinoid D. excentricus, posterior portions of larvae completed regeneration and metamorphosis, but anterior portions regenerated only partially during the 2-week study. Our observations confirm that asteroid and echinoid larvae provide excellent models for studies of regeneration in deuterostomes.     

The structure of the nervous system of the pluteus larva of Strongylocentrotus purpuratus

Summary Tissues that have the ultrastructural characteristics of nervous tissues are associated with ciliary and muscular elements of the pluteus larva of Strongylocentrotus purpuratus. The nerve cells are found along the margins of the ciliary bands, which are composed predominantly of spindle-shaped ciliated cells. The nerve cells contribute axonal processes to a tract of axons, which runs at the base of the ciliary band throughout its length. Axonal tracts, in the esophagus, lie beneath the circumesophageal muscles. Branched microvilli, which have been interpreted as sensory receptors, are located on the oral side of the main ciliary band and connect with the nerve cells in the ciliary band. The nervous structures described here, and other tissues of the pluteus that have been previously described as nervous, are compared on the basis of their association with receptor and effector organs, and their ultrastructural characteristics.     

Morphology and ecological significance of intra-annual radial cracks in living conifers

 Intra-annual radial cracks were studied on 294 cross-sections of Norway spruce sampled at two forest sites in the eastern Alps (Italy) and from seven isolated trees in the Jura region (Switzerland). Cracks were occasionally accompanied by traumatic resin canals in the wood that was formed after the cracking. Most of the cracks, however, were without such canals. Traumatic resin canals are not significantly more abundant in tree rings formed after cracking, and their occurrence is not related to the cracking. Cracks developed when the cambium was inactive. Water imbalances during the early spring, due to transpiration losses and inadequate moisture supply from very cold roots, are the likely cause of these cracks. Received: 21 February 1996 / Accepted: 14 June 1996     

Resolving insect phylogeny: The significance of cephalic structures of the Nannomecoptera in understanding endopterygote relationships

The Nannomecoptera are among the most enigmatic and controversial taxa of endopterygote insects, the phylogenetic resolution of which is crucial to understanding the evolution of neopteran insects. Once considered a subordinate lineage within the Mecoptera, renewed interest in nannochoristids has been prompted by evidence that the Nannomecoptera are not admissible to the clade of extant scorpion flies but are more likely to belong to the clade Siphonaptera + Nannomecoptera + Diptera. The overarching purpose of the present account is to provide novel and extensive morphological character traits in addition to those already existing for adult structures. The aim is to determine if these traits support molecular data sets that have been suggested elsewhere to clarify the phyletic position of Nannochoristidae. This account focuses on nannomecopteran larvae, which unlike those of other mecopterans have received little attention. Thus, the thrust of this investigation is to provide detailed anatomical data on nannochoristid larvae for a targeted inquiry into their phylogenetic affinities. The described characters are discussed and presented in a data matrix comprising representatives of all endopterygote orders. While the study is based primarily on the New Zealand species Nannochorista philpotti, it is proposed that all nannomecopteran larvae will prove to be similar to this taxon in most if not all structural features of significance to a higher-level phylogenetic context.     

Frequency discrimination in the central nerve cords of locusts

The auditory mechanism in locusts, especially the central mechanism of frequency analysis, was examined electrophysiologically. The central auditory response had a sharp rise of threshold at a certain frequency range, and it showed a remarkable change when all peripheral fibres except the tympanic nerve were cut off. The response pattern was also changed by this procedure. These results indicate the presence of an inhibitory interaction mechanism of various auditory inputs. It can be concluded that locusts are able to discriminate sound frequency to some degree by this interactive mechanism.     

The pineal gland of the mole-rat (Spalax ehrenbergi,Nehring)

Summary A comparative investigation of the distribution of monoaminergic neurons in non-malacostracan crustaceans was performed with the histochemical fluorescence method of Falck-Hillarp.Two fluorophores were found: the more widespread of the two emits a green fluorescence; and the more sparsely distributed emits a yellow to brown-yellow fluorescence.Specific green fluorescent areas were shown to exist in the protocerebrum. The central body and the optic ganglia of the compound eye (where present) are always fluorescent. Moreover, the centre of the nauplius eye may have a green fluorophore, as in ostracods, and a neuropile area, here called the frontal area. These neuropile centres are known from ordinary histological studies of the nervous system. In addition, there are specific monoaminergic centres, such as the so-called dorsal area of phyllopods and anostracans as well as the copepod specific areas. Specific monoaminergic areas appear in the deutocerebrum and the suboesophageal ganglion where they are particularly well developed.Presumed sensory neurons in the cavity receptor organ of Artemia salina are shown to be monoaminergic. Monoaminergic sensory neurons have not been described previously in Arthropods.Presumed motor innervation of hind-gut and trunk muscles is also found, and it is concluded that in crustaceans neurons of every type (sensory, internuncial, motor) may be monoaminergic.We have enjoyed unrestricted laboratory facilities at the Department of Histology, Faculty of Medicine, and with great pleasure express our sincere thanks to Prof. Bengt Falck. — Grants from the Swedish Natural Science Research Council (2760-007), the Swedish Medical Research Council (04X-712), the Royal Swedish Academy of Science (Hierta-Retzius), the Royal Physiographic Society of Lund, and the University of Lund supported the work.     

TRPC6在中枢神经系统的作用

TRPC6（Thetransientreceptorpotentialcanonical6）为瞬时受体电位（TRP）超家族的成员之一,编码钙可通透的非选择性阳离子通道。其具有六次跨膜结构。TRPC6同型或异型四聚体通道由TRPC6蛋白相互结合形成或与同在一个亚家族的TRPC3,TRPC7形成。TRPC6通道可被G蛋白耦联受体（GPCR）和受体酪氨酸激酶（receptortyrosinekinasesRTK）通过激活磷脂酶C（PLC）激活。其还可直接被第二信使DAG（diacylglycer01）激活。已有研究证实该通道通过激活上述信号传导通路参与了多种生理过程。TRPC6基因编码的蛋白在人体多个部位均有表达。TRPC6在中枢神经系统广泛表达。其在不同部位的表达量不同,并与TRPC家族的其他成员一起参与了多种生理过程。TRPC6引起的细胞阳离子浓度的变化可能参与了多种神经系统疾病的发生发展过程。因此。研究TRPC6在中枢神经系统中的作用对疾病发病机制的了解及治疗变得更有意义。本文就TRPC6在中枢神经系统中的作用进行综述,并主要介绍其在树突发育,神经元保护及细胞生长方面的作用。     

Axial patterning of the pentaradial adult echinoderm body plan

Adult echinoderms possess a highly diverged, pentaradial body plan. Developmental mechanisms underlying this body plan are completely unknown, but are critical in understanding how echinoderm pentamery evolved from bilateral ancestors. These mechanisms are difficult to study in indirect-developing species; in this study, we use the direct-developing sea urchin Heliocidaris erythrogramma, whose accelerated adult development can be perturbed by NiCl₂. We introduce a new nomenclature for the adult echinoderm axes to facilitate discussion of the radially symmetric body plan and the events required to pattern it. In sea urchins, the adult oral–aboral axis is often conflated with the long axes of the five rays; we identify these as distinct body axes, the proximodistal (PD). In addition, we define a circular axis, the circumoral (CO), along which the division into five sectors occurs. In NiCl₂-treated larvae, aspects of normal PD pattern were retained, but CO pattern was abolished. Milder treatments resulted in relatively normal juveniles ranging from biradial to decaradial. NiCl₂ treatment had no effect either on mesodermal morphology or on the ectodermal gene expression response to an inductive mesodermal signal. This suggests that the mesoderm does not mediate the disruption of CO patterning by NiCl₂. In contrast, mesodermal signaling may explain the presence of PD pattern in treated larvae. However, variations in appendage pattern suggest that ectodermal signals are also required. We conclude that CO patterning in both germ layers is dependent on ectodermal events and PD patterning is controlled by mutual ectoderm–mesoderm signaling.     

Experimental analysis of sensory nerve pathways inDrosophila

Summary The pathway of adult sensory nerves has been analysed in three experimental situations: (i) in flies with grossly abnormal thoracic morphology resulting from X-irradiation early during development, (ii) in flies which had been subjected to surgical operations late in the larval period, (iii) in homoeotic mutants. The results provide experimental support for a simple mechanism in which developing adult axons join the nearest larval nerve and are guided by it up to the central nervous system. In particular, experimental interference with normal development can result in nerves from different segments, or from dorsal and ventral appendages, joining each other and entering the central nervous system together.     

Monoaminergic neurons in the nervous system of crustaceans

Summary Certain neurons in the nervous system of the malacostracan crustaceans give rise to a predominantly green and a sparse yellow fluorophore in the histochemical fluorescence method of Falck-Hillarp. The same applies to the whole of Crustacea. The green fluorophore is probably a catecholamine; the yellow to brown-yellow has not yet been identified.The biogenic amine responsible for the green fluorescence, besides being found in diffusely distributed fibres, also appears in distinct areas of fibre concentrations in the central nervous system. The protocerebrum of the malacostracans contains three areas: the central body and two areas in the top of the brain, one anterior and one posterior. The latter two are not recognized as separate areas in ordinary histological preparations. In addition, the optic neuropiles are fluorescent, some with a distinct stratification of the fluorophore. The deuto and tritocerebrum and the ventral nerve cord also contain monoaminergic neurons. Of the brightly fluorescent areas in the whole of Crustacea, only the central body consistently exists in all species. The other areas of concentrated fluorescent neuropile are restricted to smaller taxonomic units and differ from each other. p The monoaminergic neurons in Crustacea are sensory, motor, and internuncial, and also belong to a fourth type which mimics the neurosecretory neurons in neurohaemal organs. Only one example of a monoaminergic sensory neuron is known (in Anemia, a non-malacostracan, Aramant and Elofsson 1976), a few motor and a few neurosecretory mimics (the latter in malacostracans). Most are internuncials. Acknowledgement. We have enjoyed the laboratory facilities at the Department of Histology, Faculty of Medicine, and express our sincere thanks to Prof. Bengt Falck.-Grants from the Swedish Natural Science Research Council (2760-007) and the Swedish Medical Research Council (04X-712) supported the work     

神经系统内高亲和谷氨酸摄取及其调节影响因素

神经系统内高亲和谷氨酸１（Ｇｌｕ）摄取是Ｎａ＾＋依赖性的,由Ｇｌｕ能神经末梢及胶质细胞膜上的Ｇｌｕ转运蛋白介导。已克隆得到四种Ｇｌｕ转运蛋白,分别为ＧＬＡＳＴ１、ＧＬＵＴ１、ＥＡＡＣ１及ＥＡＡＴ４。它们的所在部位、分布及药理学性质都有自己的特点。花生四烯酸、一氧化氮、氧自由基、蛋白激酶、细胞因子及生长因子等多种因素能调节或影响高亲和Ｇｌｕ摄取。很显然这些因素的调节或影响效应具有一定生理及病理生理意     

The anatomy of the nervous system of the hydrozoan jellyfish,Polyorchis penicillatus,as revealed by a monoclonal antibody

Dissociated cells from the margin and tentacles of the hydromedusa Polyorchis penicillatus were centrifuged in a Percoll gradient to remove cnidocytes. The resulting formaldehyde-fixed cells were used to inoculate mice to produce monoclonal antibodies. One of the hybridomas, which secreted antibodies against all neurons, was cloned and designated as mAb 5C6. Immunohistochemical labelling with mAb 5C6 of whole-mount preparations and paraffin sections provided a far more complete picture of the organisation of the hydromedusan nervous system than was previously available when using neuronal labelling techniques that restrict labelling to certain neuronal types. Besides confirming anatomical features described in earlier studies these techniques allowed us to discover a number of new structures and to determine connections that were only suspected. Such findings included: 1.The discovery of an arch-like connection between the swimming motor neuron network at the apices of the subumbrellar muscle sheets 2.An orthogonal network connecting each pair of radial nerves in each radius 3.Continuity of a central branch of the radial nerve with the radial innervation of the manubrium 4.Details of the sensory neuronal contribution to the microanatomy of the ocelli and cnidocyte batteries 5.Presence of specialised receptor cells in the margin at the bases of tentacles 6.Neurons apparently innervating the radial muscles of the velum 7.Isolated neurons in the peduncle and gonads Electronic Publication