bluuebunny/crossref_metadata_2025 huggingface dataset:
Fly photoreceptor synapses: Their development, evolution, and plasticity
Authors: Meinertzhagen I. A.
Published: January 2005

Recent studies are reviewed on the synapses of photoreceptor terminals in the first optic neuropile of the flies, Musca and Drosophila. Afferent synaptic contacts are of uniform dimensions; they have a postsynaptic tetrad with a membrane organization of P‐face particles, resembling other inhibitory synapses. A distributed population of such contact sites forms progressively during synaptogenesis by the selective, sequential accretion of identified postsynaptic elements at the receptor terminal. The comparative anatomy of this synapse indicates that elements have also been added during its phylogeny from an ancestral dyad. All cells are homologs of those in other species of Diptera. The number of synaptic sites is regulated by both pre‐ and postsynaptic cells, in proportion to their cell surfaces; an independent size increase in the receptor terminals (procured in the Drosophila mutant gigas) produces an increase in their synaptic population. The number of sites declines with age, however, accompanied by an increase in size of those synaptic sites remaining; this occurs for both afferent and feedback photoreceptor synapses. Lastly, the number of sites changes with visual experience; the frequency of feedback synapses is larger following dark rearing during early adult life than following visual experience.
Characterization of protein‐linked glycoconjugates produced by identified neurons of Aplysia californica
Authors: Gabel Christopher A. , Den Halina , Ambron Richard T.
Published: January 2005

The biosynthetic capabilities of individual neurons of the abdominal ganglion of the marine mollusc Aplysia californica have been analyzed after intrasomatic injection of 3H‐monosaccharides. Glycopeptides prepared from the metabolically labeled cells were fractionated using serial lectin affinity and gel filtration chromatography. The fractionation procedure yielded eight populations of glycopeptides, and comparison of two different neurons (R2 and R14) showed that the quantity of the individual species produced is cell‐dependent. Structural analysis indicated that the glycoconjugates produced by the Aplysia neuron constitute both O‐ and N‐linked structures as well as an unusual class of oligosaccharide whose linkage to protein is unknown. The O‐linked units are small and consist only of N‐acetylglucosamine or N‐acetylgalactosamine attached to protein. High‐mannose‐type asparagine‐linked units are produced by the neurons, and some of these appear to be processed to biantennary complex‐type units that bind to lentil lectin‐agarose. Overall, although the Aplysia neurons produce oligosaccharides of a nature similar to that produced by higher eucaryotes, the N‐ and O‐linked structures produced by the neurons do not achieve the complexity of the comparable structures produced by mammalian cells. The results provide a basis for further studies aimed at understanding the role of glycoconjugates in the development of the nervous system.
Factors released by ciliary neurons and spinal cord explants induce acetylcholine receptor mRNA expression in cultured muscle cells
Authors: Bursztajn S. , Berman S. A. , Gilbert W.
Published: January 2005

The nuclei of cultured noninnervated muscles cells are heterogeneous with respect to production of mRNA for the nicotinic actycholine receptor (AChR). Some nuclei actively express AChR mRNA while others have a low level of activity or are inactive. To determine if innervation, or a factor released by neurons, influences nuclear expression of AChR mRNA, we examined mRNA at a single cell level via in situ hybridization and autoradiography with an α‐subunit AChR genomic probe. Four days after plating, we co‐cultured chicken primary muscle cells with spinal cord explants, ciliary neurons, or dorsal root ganglia (DRG) cells. In situ hybridization of the spinal‐cord and muscle‐cell co‐cultures with the AChR α‐subunit genomic probe revealed a high density of silver grains on muscle cells, which were within two explant diameters of the spinal cord explant, and a graded decrease in silver grain density as the distance from the explant increased, as well as the appearance of a strikingly nonhomogenous distribution of active and inactive muscle cell nuclei. When ciliary neurons were uniformly distributed over the muscle cells, a high level of AChR mRNA was induced, but no gradients appeared. Neither an increased mRNA level nor a gradient was observed when DRG cells were co‐cultured with muscle cells. When ciliary neurons are cultured within Costar permeable inserts, which prevent any contact between the neurons and the underlying muscle cells, AChR messenger RNA is still induced, showing that diffusible factors are responsible. Our results indicate that molecules released by cholinergic neurons regulate the expression of AChR mRNA in the myotubes and raise the possibility that AChR expression depends on both neuronal signals and on intracellular information from the muscle cell.
Induction of differentiation of rat retinal, germinal, neuroepithelial cells by dbcAMP
Authors: Taylor M. , Reh T. A.
Published: January 2005

Little is known about the factors that regulate the production of neurons during the development of the vertebrae central nervous system (CNS); however, evidence from several neuronal cell lines suggests that an increase in intracellular cAMP might trigger the process of differentiation. To determine if a similar process is involved in differentiation during normal CNS neurogenesis, we raised the intracellular level of cAMP in primary cultures of mitotically active, germinal neuroepithelial cells from fetal and postnatal rat retina. This treatment induced differentiation of the CNS precursors, causing the cells to cease DNA synthesis and increase their expression of proteins normally found in differentiated retinal cells. These results indicate that germinal neuroepithelial cell differentiation can be controlled through the cAMP second messenger system, and that the regulation of this system may in part determine the numbers and ratios of the various classes of neurons during the normal development of the CNS.
Sexual dimorphisms in the vocal control system of a teleost fish: Morphology of physiologically identified neurons
Authors: Bass Andrew H. , Baker Robert
Published: January 2005

In one species of vocalizing (sonic) fish, the midshipman (Porichthys notatus), there are two classes of sexually mature males—Types I and II—distinguished by a number of traits including body size, gonad size, and reproductive tactic. The larger Type‐I males (unlike Type‐II males and females) build nests, guard eggs, and generate several types of vocalizations. Sound production by Type‐I males is paralleled by a proportionate increase of 600% in their sonic muscle mass. The motor volley from ventral occipital roots innervating the sonic muscles establishes their contraction rate and, in turn, the fundamental frequency of emitted sounds. Electrical stimulation of the midbrain in every male and female elicited a rhythmic sonic discharge as recorded in the occipital roots; however, the fundamental frequency was slightly, but significantly, higher (20%) in Type‐I males. Intracellular recording from identified motoneurons and presumed presynaptic “pacemaker” neurons showed their synaptic and action potentials had the same frequency as that of the nerve volley in every male and female. Reconstructions of physiologically identified motoneurons and pacemaker neurons following intracellular horseradish‐peroxidase (HRP) filling showed their somata and dendrites to be 100–300% larger in Type‐I males. These data unambiguously show that the size of a target muscle is correlated with the size of both the respective motoneurons and their presynaptic afferent neurons. As discussed, this implies that the dramatic increase in neuron size in the sonic motor system of Type‐I males is causally dependent upon expansion of the sonic muscle. It is further likely that the more modest sex difference in the rhythmic central discharge is established by the intrinsic membrane properties of sonic neurons. These results also corroborate, at a number of behavioral, morphological, and neurophysiological levels, that the sonic motor system of “sneak spawning” Type‐II males is similar to that of females. Thus, unlike the vocalizing Type‐I males, sexual differentiation of the reproductive system in Type‐II males is not linked to concomitant changes in the neurophysiological and morphological features of the sonic motor circuit.
Neuromuscular development following tetrodotoxin‐induced inactivity in mouse embryos
Authors: Houenou Lucien J. , Pinçon‐Raymond Martine , Garcia Luis , Harris A. John , Rieger François
Published: January 2005

Developmental aspects of the neuromuscular system in mouse embryos chronically paralyzed in utero with tetrodotoxin (TTX) between embryonic days 14 and 18 were studied using biochemical and histological methods. The number of lumbar spinal motoneurons (MNs) was higher in inactive embryos than in controls suggesting a decreased motoneuron cell death. In association with the increase in MN number, choline acetyltransferase activity was significantly increased in both spinal cord and peripheral synaptic sites. Paralyzed muscles exhibited a decreased number of mature myofibers and the nuclei were centrally located. Creatine kinase activity was greatly decreased and total acetylcholine receptor and receptor cluster numbers per myofiber were significantly increased in paralyzed muscles. A similar pattern of changes occurs in the neuromuscular system of the mutant mouse muscular dysgenesis (mdg). However, in contrast to the mdg mutant, tetrodotoxin‐treated muscles were similar to controls in their innervation pattern, in the ultrastructural aspects of the excitation–contraction coupling system (i.e., dyads and triads) and in the extent of dihydropyridine binding. Thus, neuromuscular inactivity is not sufficient to impair the pattern of muscle innervation or the appearance of either the triadic junctions or dihydropyridine receptors. These results indicate that alterations of dihydropyridine binding sites and triads in muscular dysgenesis cannot be accounted for by inactivity but rather must reflect a more primary defect involving the structural gene(s) regulating the development of one or more aspects of muscle differentiation.
Short‐term action of insulin on Aplysia neurons: Generation of a possible novel modulator of ion channels
Authors: Shapiro Eli , Brown Steven D. , Saltiel Alan R. , Schwartz James H.
Published: January 2005

In mollusks as in other animals, peptides can act as hormones, growth factors, and neurotransmitters. The presence of insulin in vertebrate brain as well as its actions on nerve cells led us to examine the electrophysiological effects of the mammalian hormone on Aplysia neurons. Application of insulin extracellularly causes hyperpolarization of L14 and L10, identified neurons of the abdominal ganglion. This hyperpolarization is associated with a decreased membrane conductance that reverses at −35 mV. We also injected inositol phosphate glycan (IPG) into the identified neurons. This complex sugar, which was purified from rat liver and which is a putative second messenger for insulin in nonneural vertebrate cells (Saltiel and Cuatrecasas, 1986; Saltiel, Osterman, and Darnell, 1988), causes hyperpolarization with decreased membrane conductance in L14 and L10 similar to the effects of insulin. Furthermore, exposure of isolated ganglia to insulin results in the generation of IPG with a compensating decrease in its glycosyl‐phosphatidylinositol precursor. We suggest that, in addition to its other roles, insulin may function as a neuropeptide transmitter using IPG as a second messenger.
Development of estradiol‐induced progestin receptor immunoreactivity in the hypothalamus of female guinea pigs
Authors: Olster Deborah H. , Blaustein Jeffrey D.
Published: January 2005

The inability of young female guinea pigs to display progesterone‐facilitated lordosis has been attributed, in part, to a deficiency in the concentration of hypothalamic estradiol‐induced progestin receptors, as measured by in vitro binding assays. An immunocytochemical technique was used to ascertain where, within the mediobasal hypothalamus, estradiol‐induced progestin receptor levels are lower in immature than in adult females. Adult (>7 weeks) and juvenile (3 weeks) ovariectomized females received 10 μg estradiol benzoate, a dose that primes adult, but not immature females to respond behaviorally to progesterone. Progestin receptor‐immunoreactive (PR‐IR) cells were counted in the arcuate nucleus (ARC) and ventrolateral hypothalamus (VLH), the two regions containing the densest populations of estradiol‐induced progestin receptors in the mediobasal hypothalamus. There was no age difference in the number of PR‐IR cells in the rostral or caudal VLH, but immunostaining was darker in the rostral VLH of juveniles as compared to adults. We found similar numbers of PR‐IR cells in the rostral and mid‐ARC, but 35% fewer immunostained cells in the caudal ARC of immature, as compared to adult females. Furthermore, staining intensity was weaker in the mid‐ and caudal ARC of the juvenile females. These data suggest that the ARC, not the VLH, is a site of fewer estradiol‐induced progestin receptors in immature females.
Neuron loss and addition in developing zebra finch song nuclei are independent of auditory experience during song learning
Authors: Burek Michael J. , Nordeen Kathy W. , Nordeen Ernest J.
Published: January 2005

In zebra finches early auditory experience is critical for normal song development. Young males first listen to and memorize a suitable song model and then use auditory feedback from their own vocalizations to mimic that model. During these two phases of vocal learning, songrelated brain regions exhibit large, hormone‐induced changes in volume and neuron number. Overlap between these neural changes and auditory‐based vocal learning suggests that processing and acquiring auditory input may influence cellular processes that determine neuron number in the song system. We addressed this hypothesis by measuring neuron density, nuclear volume, and neuron number within the song system of normal male zebra finches and males deafened prior to song learning (10 days of age). Measures were obtained at 25, 50, 65, and 120 days of age, and included four song nuclei: the hyperstriatum ventralis pars caudalis or higher vocal center (HVc), Area X, the robust nucleus of the archistriatum (RA), and the lateral magnocellular nucleus of the anterior neostriatum (lMAN). In both HVc and Area X, nuclear volume and neuron number increased markedly with age in both normal and deafened birds. The volume of RA also increased with age and was not affected by early deafening. In lMAN, deafening also did not affect the overall age‐related loss of neurons, although at 25 days neuron number was slightly less in deafened than in normal birds. We conclude that while the addition and loss of neurons in the developing song system may provide plasticity essential for song learning, these changes do not reflect learning. Thus, in the zebra finch song system neither the growth of song nuclei nor the developmental regulation of neuron number depend on auditory learning during song development.
Distinctions in growth cone morphology and motility between monopolar and multipolar neurons in Drosophila CNS cultures
Authors: Kim Yun‐Taik , Wu Chun‐Fang
Published: January 2005

Growth cones play a central role in determining neurite extension, pathfinding and branching, and in establishing synaptic connections. This paper describes an initial characterization of growth cone morphology and behavior in dissociated larval central nervous system (CNS) cultures of Drosophila. Contrast‐enhanced video images of growth cones in monopolar and multipolar neurons were characterized by employing morphometric parameters such as the number and length of filopodia, and the area and roundness of the lamellipodia. Behavior of growth cones was analyzed by a motility index and boundary flow plots originally devised for measuring motility in other cellular systems. We found that separate CNS regions yielded cultures of different major cell types with distinct neuritic patterns that could be correlated with the morphology and motility of the associated growth cones. Monopolar neurons were the major cell type in brain cultures, whereas multipolar neurons were predominant in ventral ganglion cultures. Moreover, the growth cones of monopolar neurons, which are likely to be associated with the axonal processes, differed from those of multipolar neurons, which might be related to dendritic terminals. Growth cones in monopolar neurons had larger lamellipodia of less erratic shape accompanied by fewer and shorter filopodia, and, when active, displayed much higher motility and less directionality in motion. Alternatively, these morphological and behavioral distinctions between monopolar and multipolar neurons may result from intrinsic differences in membrane adhesion and intracellular transport properties.
Transneuronal induction of muscle atrophy in grasshoppers
Authors: Arbas Edmund A. , Weidner Mark H.
Published: January 2005

Autotomy is a process in grasshoppers whereby one or both hindlimbs can be shed to escape a predator or can be abandoned if damaged. It occurs between the trochanter and the femur (second and third leg segments) and once lost, the legs never regenerate. Autotomy severs branches of the leg nerve (N5) but damages no muscles since none span the autotomy plane. We find, however, that undamaged muscles intrinsic to the thorax of grass‐hoppers, Barytettix psolus, atrophy to <15% of their normal mass after autotomy of a hindlimb. These muscles operate the coxa and trochanter (first and second leg segments) and are innervated by branches of nerves 3 and 4; nerve branches that are not damaged by autotomy. Atrophy is localized to the side and body segment where autotomy occurs. Atrophy is evident 7–10 days after loss of a limb, is complete by about 30 days, and follows a similar time course whether induced in young adult, or sexually mature grasshoppers. During autotomy, leg nerve 5 is severed distal to the trochanter, the thoracic muscles lose their normal static and dynamic load, and these muscles are subsequently no longer used to support the weight of the insect during posture and locomotion. Experimental loading and unloading of the affected muscles, and cutting of nerves indicated that it is the severing of leg nerve 5 during autotomy that transneuronally induces muscle atrophy.
Physiological and developmental implications of motor unit anatomy
Authors: Ounjian M. , Roy R. R. , Eldred E. , Garfinkel A. , Payne J. R. , Armstrong A. , Toga A. W. , Edgerton V. R.
Published: January 2005

There is increasing evidence that the architectural design and arrangement of the fibers within a motor unit have important physiological and developmental ramifications. Limited data, however, are available to directly address this issue. In the present study the physiological properties of one motor unit in each of seven cat tibialis anterior (TA) muscles were determined. Each of these units then was repetitively stimulated to deplete the glycogen in all muscle fibers within the unit. Subsequently, the length, type of ending, and spatial distribution of fibers sampled from these physiologically and histochemically typed motor units were determined. Four fast fatigable (FF), one fast, fatigue resistant (FR), and two slow (S) motor units (MU) were studied. The samples consisted of all those glycogen‐depleted fibers (9–27) contained within a single fascicle or a circumscribed area of each of the motor unit territories. The mean fiber lengths for the two slow motor units were 35.9 and 45.5 mm. The mean fiber lengths for the fast motor unit samples ranged from 8.8 to 48.5 mm. Some fibers of both the fast and slow units reached lengths of 58 mm. Most of the fibers in the slow units extended the entire distance between the proximal and distal musculotendinous planes, had relatively constant cross‐sectional areas, and terminated at the tendon as blunt endings. In contrast, the majority of the fibers in the fast units terminated intrafascicularly at one end, and the cross‐sectional area decreased progressively along their lengths, that is, showed a tapering pattern for a significant proportion of their lengths. Therefore, the force generated by units that end midfascicularly would appear to be transmitted to connective tissue elements and/or adjacent fibers. All fibers of a fast unit within a fascicle were located at approximately the same proximo‐distal location. Thus, developmentally the selection of muscle fibers by a motoneuron would seem to be influenced by their spatial distribution. The architectural complexities of motor units also have clear implications for the mechanical interactions of active and inactive motor units. For example, the tension capabilities of a motor unit may be influenced not only by the spatial arrangement of its own fibers, but also by the level of activation of neighboring motor units.
Directional control of neurite outgrowth from cultured hippocampal neurons is modulated by the lectin concanavalin A
Authors: Farmer Lynne M. , Hagmann Jörg , Dagan Daniel , Matus Andrew I. , Levitan Irwin B.
Published: January 2005

Cell surface carbohydrates play an important role in the regulation of neurite outgrowth during neuronal development. We have investigated the actions of the plant lectin concanavalin A (Con A), a carbohydrate‐binding protein, on neurite outgrowth from hippocampal pyramidal neurons in primary cell culture. Neurons plated in culture medium containing nanomolar concentrations of Con A have a larger number of primary neurites arising directly from the cell soma than do neurons plated in culture medium alone. Furthermore, Con A causes counterclock‐wise turning of neurites in over 70% of the cultured neurons. Both of these effects of Con A are blocked by the hapten sugar α‐methyl‐d‐mannopyranoside, suggesting that they result from the interaction of Con A with a cell surface carbohydrate. Another lectin with a different sugar specificity, wheat germ agglutinin, does not modulate neurite outgrowth. Analysis of neurite outgrowth using video‐enhanced microscopy reveals that the counter‐clockwise turning is accompanied by directionally biased extension of filopodia from the growth cones of growing neurites. Treatment of the neurons with cytochalasin, which disrupts actin polymerization, eliminates the neurite turning induced by Con A, suggesting that actin microfilaments are involved in directional control of neurite outgrowth. © 1992 John Wiley & Sons, Inc.
Transient neonatal denervation alters the proliferative capacity of myosatellite cells in dystrophic (129ReJdy/dy) muscle
Authors: Ontell M. P. , Hughes D. , Hauschka S. D. , Ontell M.
Published: January 2005

It has been previously shown that transiently denervated, neonatal dystrophic muscle fails to undergo the degeneration–regeneration cycle characteristic of murine dystrophy (Moschella and Ontell, 1987). Thus, the myosatellite cells (myogenic stem cells) in these muscles have been spared the mitotic challenge to which dystrophic myosatellite cells are normally subjected early in the time course of the disease. By in vitro evaluation of the proliferative capacity of myosatellite cells derived from extensor digitorum longus (EDL) muscles of 100‐day‐old genetically normal (+/+) and genetically dystrophic [dy/dy (129ReJdy/dy)] mice and from muscles of age‐matched mice that had been neonatally denervated (by sciaticotomy) and allowed to reinnervate, it has been possible to directly determine whether the cessation of spontaneous regeneration in older dy/dy muscles in vivo, is due to an innate defect in the proliferative capacity of the myosatellite cells or exhaustion of the myosatellite cells' mitotic activity during the regenerative phase of the disease. This study demonstrates that transient neonatal denervation of dystrophic muscle (Den.dy/dy) increases the number of muscle colony‐forming cells (MCFs) permilligram of wet weight muscle tissue, increases the plating efficiency, and significantly increases the in vitro mitotic activity of dystrophic myosatellite cells toward normal values. The increased mitotic capability of myosatellite cells derived from Den.dy/dy muscle as compared to unoperated dy/dy muscle suggests that there is no innate defect in the proliferative capacity of the myosatellite cells of dy/dy muscles and that the cessation of spontaneous regeneration in the dy/dy muscles is related to the exhaustion of their myosatellite cells' mitotic capability. © 1992 John Wiley & Sons, Inc.
Preparation and biological properties of native and recombinant ciliary neurotrophic factor
Authors: Gupta S. K. , Altares M. , Benoit R. , Riopelle R. J. , Dunn R. J. , Richardson P. M.
Published: January 2005

CNTF (ciliary neurotrophic factor), purified from rabbit sciatic nerves by a relatively simple procedure, is bioactive in tissue culture at low picomolar concentration and appears as a doublet on polyacrylamide gel electrophoresis (PAGE). In these nerves, CNTF accounts for more than one‐half of the survival‐promoting activity on ciliary neurons. The concentration of CNTF in rabbit sciatic nerves is estimated to be 5 nmol/kg, more than 1000 times higher than would seem to be required to support neurons if the neurotrophic factor were homogeneously distributed. With recombinant DNA technology, rat CNTF has been synthesized in Escherichia coli, purified without denaturating agents, and found to be bioactive at a slightly lower concentration than CNTF extracted from rabbit sciatic nerves. After radioiodination, CNTF retains biological activity but is not specifically internalized and retrogradely transported in motor and sensory axons. In peripheral nerves, ciliary neurotrophic factor differs biologically from nerve growth factor (NGF) by its much higher tissue concentration and apparent lack of internalization by peripheral nerve axons. © 1992 John Wiley & Sons, Inc.
GAP‐43 as a plasticity protein in neuronal form and repair
Authors: Strittmatter Stephen M. , Vartanian Timothy , Fishman Mark C.
Published: January 2005

Neurons exhibit a remarkable plasticity of form, both during neural development and during the subsequent remodelling of synaptic connectivity. Here we review work on GAP‐43 and G0, and focus upon the thesis that their interaction may endow neurons with such plasticity. We also present new data on the role of G proteins in neurite growth, and on the interaction of GAP‐43 and actin. GAP‐43 is a protein induced during periods of axonal extension and highly enriched on the inner surface of the growth cone membrane. Its membrane localization is primarily due to a short amino terminal sequence which is subject to palmitoylation. Binding to actin filaments may also assist in restricting the protein to specific cellular domains. Consistent with its role as a „plasticity protein,”︁ there is evidence that GAP‐43 can directly alter cell shape and neurite extension, and several theses have been advanced for how it might do so. Two other prominent components of the growth cone membrane are the α and β subunits of G0. GAP‐43 regulates their guanine nucleotide exchange, which is an unusual role for an intracellular protein. We speculate that GAP‐43 may adjust the „set point”︁ of responsiveness for G0 stimulation by receptors, thereby altering the neuronal propensity to growth, without actually causing growth. To begin to address how G protein activity affects axon growth, we have developed a means to introduce guanine nucleotide analogs into sympathetic neurons. Stimulation of G proteins with GTP‐γ‐S retards axon growth, whereas GDP‐β‐S enhances it. This is compatible with G protein registration of inhibitory signals. © 1992 John Wiley & Sons, Inc.
Patterns of serotonin and SCP immunoreactivity during metamorphosis of the nervous system of the red abalone, Haliotis rufescens
Authors: Barlow Linda A. , Truman James W.
Published: January 2005

Larvae of the red abalone, Haliotis rufescens, rely on external chemical cues to trigger metamorphosis; thus, the timing of metamorphosis is depedent upon the larva's chance encounter with the appropriate substrate. We examined the effect of the timing of metamorphosis on the development of the central nervous system (CNS), concentrating on the pattern of serotonin and small cardioactive peptide‐ (SCP) immunopositive neurons in the cerebral ganglia. By 4 days postfertilization the cerebral ganglion has five pairs of serotonin‐immunoreactive (IR) neurons, one pair of which (the V cells) innervate the velum. This complement of cells remains stable for as long as the larval stage persists but metamorphosis causes the rapid loss of the V cells. In the case of SCP‐IR neurons, one pair is present prior to metamorphic competency, but as larvae continue to age in the absence of inducing cues, additional pairs are gradually added. Metamorphosis causes an acceleration in SCP‐IR neuron addition. This separation of developmental patterns is well adapted for the inherent uncertainty of the timing of metamorphosis in abalone larvae. © 1992 John Wiley & Sons, Inc.
The paired domain‐containing nuclear factor Pax[b] is expressed in specific commissural interneurons in zebrafish embryos
Authors: Mikkola Ingvild , Fjose Anders , Kuwada John Y. , Wilson Stephen , Guddal Per Henrik , Krauss Stefan
Published: January 2005

The zebrafish paired box (Pax) genes are expressed in the early neural tube and are thought to be transcription factors that regulate the differentiation of cells in the central nervous system (CNS). The protein product of one of these Pax genes, pax[b], is detectable as a nuclear antigen in all the regions of the embryo that transcribe the gene including the posterior midbrain, the nephritic primordium, the Wolffian duct, the optic stalk, and, in specific neurons, in the hindbrain and spinal cord. The timing and pattern of axonal outgrowth by the early pax[b]‐positive neurons suggest that they are the commissural secondary ascending (CoSA) interneurons in the spinal cord; the primary commissural interneurons (MiD2c and MiD3c) in hindbrain rhombomeres mi2 and mi3; and a previously unclassified set of commissural interneurons that we termed the commissural caudalrhombomere ascending (CoCaA) interneurons in the caudal hindbrain. In contrast, the Mauthner interneurons do not express pax[b] early in development. Shortly after the appearance of the first pax[b]‐positive interneurons, additional nuclei adjacent to the first pax[b]‐positive interneurons become pax[b] positive. This pattern of expression suggests that the pax[b] protein may be involved in determining the identity of specific commissural interneurons. © 1992 John Wiley & Sons, Inc.
The distribution of tyrosine hydroxylase immunoreactivity in the brains of male and female zebra finches
Authors: Bottjer Sarah W.
Published: January 2005

A system of brain nuclei controls song learning and behavior in zebra finches (Poephila guttata). The size of song‐control nuclei are much larger in males, which sing, than in females, which do not sing. This study examined the distribution of fibers, terminals, and cell bodies that are immunoreactive for tyrosine hydroxylase (TH) (the rate‐limiting enzyme in the synthesis of catecholamines) in song‐control nuclei of adult males and females and juvenile males. In addition, the broad pattern of TH staining throughout the brain was described. There was a sex difference in TH immunoreactivity within song‐control nuclei: males had light to moderate staining in all three cortical nuclei examined, whereas females had little or no label in corresponding areas [lateral magnocellular nucleus of the anterior neostriatum (IMAN), higher vocal center (HVC), and robust nucleus of the archistriatum (RA)]. The song‐control nucleus area X (X), located in the striatum of avian basal ganglia, was more darkly stained than the surrounding striatum only in males; X was not defined by more intense immunoreactivity in females and hence could not be visualized. There were no apparent differences in TH staining in males ranging in age from 50 days to adulthood (>90 days). Outside of the song‐control system there were no substantive differences as a function of sex or age in the pattern or intensity of TH labeling. Major areas of telencephalic staining included the striatal region of basal ganglia, which was covered with dense, fine‐grained label, and the septum, where cell bodies were encircled by extremely well‐labeled thick processes. In the diencephalon, the preoptic area and hypothalamus included a complex pattern of darkly stained somata and fiber and terminal labeling. Darkly stained somata surrounded the pretectal nucleus, and labeled processes ramified throughout the superficial layers of the optic tectum. The midbrain and hindbrain contained a dense plexus of extremely dark cell bodies corresponding to mammalian substantia nigra, adjacent tegmental areas, and locus ceruleus. Labeled hindbrain cells were also seen in the pontine region, around nucleus solitarius, and in the ventrolateral medulla. © 1993 John Wiley & Sons, Inc.
From neural crest to bowel: Development of the enteric nervous system
Authors: Gershon Michael D. , Chalazonitis Alcmèe , Rothman Taube P.
Published: January 2005

The ENS resembles the brain and differs both physiologically and structurally from any other region of the PNS. Recent experiments in which crest cell migration has been studied with DiI, a replication‐deficient retrovirus, or antibodies that label cells of neural crest origin, have confirmed that both the avian and mammalian bowel are colonized by émigrés from the sacral as well as the vagal level of the neural crest. Components of the extracellular matrix, such as laminin, may play roles in enteric neural and glial development. The observation that an overabundance of laminin develops in the presumptive aganglionic region of the gut in Is/Is mutant mice and is associated with the inability of crest‐derived cells to colonize this region of the bowel has led to the hypothesis that laminin promotes the development of crest‐derived cells as enteric neurons. Premature expression of a neuronal phenotype would cause crest‐derived cells to cease migrating before they complete the colonization of the gut. The acquisition by crest‐derived cells of a nonintegrin, nervespecific, 110 kD laminin‐binding protein when they enter the bowel may enable these cells to respond to laminin differently from their pre‐enteric migrating predecessors. Crest‐derived cells migrating along the vagal pathway to the mammalian gut are transiently catecholaminergic (TC). This phenotype appears to be lost rapidly as the cells enter the bowel and begin to follow their program of terminal differentiation. The appearance and disappearance of TC cells may thus be an example of the effects of the enteric microenvironment on the differentiation of crest‐derived cells in situ. Crest‐derived cells can be isolated from the enteric microenvironment by immunoselection, a method that takes advantage of the selective expression on the surfaces of crest‐derived cells of certain antigens. One neurotrophin, NT‐3, promotes the development of enteric neurons and glia in vitro. Because trkC is expressed in the developing and mature gut, it seems likely that NT‐3 plays a critical role in the development of the ENS in situ. Although the factors that are responsible for the development of the unique properties of the ENS remain unknown, progress made in understanding enteric neuronal development has recently accelerated. The application of new techniques and recently developed probes suggest that the accelerated pace of discovery in this area can be expected to continue. © 1993 John Wiley & Sons, Inc.
Immunocytochemical localization of sodium channels in an insect central nervous system using a site‐directed antibody
Authors: French A. S. , Sanders E. J. , Duszyk E. , Prasad S. , Torkkeli P. H. , Haskins J. , Murphy R. A.
Published: January 2005

Antibodies to channel proteins and specific peptide sequences have been previously used to localize voltage‐activated sodium channels in the rat brain. Here we describe the first localization of sodium channels in an insect nervous system using a site‐directed antibody. The mesothoracic ganglion of the cockroach was stained with an antibody to the highly conserved SP19 sequence. Antibody labelling was visualized by light microscopy using the avidin/biotin method on was sections, and transmission electron microscopy of immunogold‐labelled thin sections. Central ganglia of insects contain clearly separated regions of cell bodies, synaptic neuropil, axon tracts, and nerves. Antibody staining by light microscopy was limited to neurons, and was intense in axons throughout the ganglion and nerves. Staining was also strong in the cytoplasm, but not the nuclei, of many neuronal cell bodies. Neuropil regions were relatively lightly labelled. These findings can be correlated with the known electrophysiology of the ganglion. Electron microscopy detected sodium channels in areas surrounding axons, probably including axon membranes and enveloping glial cell membranes. Axonal mitochondria were also heavily labelled, suggesting a sodium channel transport function for these organelles. © 1993 John Wiley & Sons, Inc.
Injury‐associated induction of GAP‐43 expression displays axon branch specificity in rat dorsal root ganglion neurons
Authors: Schreyer David J. , Skene J. H. Pate
Published: January 2005

Peripheral nerve injury results in the increased synthesis and axonal trasnport of the growth‐associated protein GAP‐43 in dorsal root ganglion (DRG) neurons, coincident with regenerative growth of the injured peripheral axon branches. To determine wheter the injury‐associated signalling mechanism which leads to GAP‐43 induction also operates through the central branches of DRG axons, we used immunocytochemistry to compare the expression of GAP‐43 in adult rat DRG neurons 2 weeks after dorsal root crush lesions (central axotomy) or peripheral nerve crush lesions (peripheral axotomy). In uninjured ganglia, a subpopulation of smaller DRG neurons expresses moderate levels of GAP‐43, whereas larger neurons generally do not. At 2 weeks following peripheral axotomy, virtually all axotomized neurons, large and small, express high levels of GAP‐43. At 2 weeks following dorsal root lesions, no increase in GAP‐43 expression is detected. Thus, the injury‐associated up‐regulation of GAP‐43 expression in DRG neurons is triggered by a mechanism that is responsive to injury of only the peripheral, and not the central, axon branches. These findings support the hypothesis that GAP‐43 induction in DRG neurons is caused by disconnection from peripheral target tissue, not by axon injury per se. © 1993 John Wiley & Sons, Inc.
Induction and axial patterning of the neural plate: Planar and vertical signals
Authors: Altaba A. Rulz i
Published: January 2005

In this review I summarize recent findings on the contributions of different cell groups to the formation of the basic plan of the nervous system of vertebrate embryos. Midline cells of the mesoderm—the organizer, notochord, and prechordal plate—and midline cells of the neural ectoderm—the notoplate and floor plate—appear to have a fundamental role in the induction and patterning of the neural plate. Vertical signals acting across tissue layers and planar signals acting through the neural epithelium have distinct roles and cooperate in induction and pattern formation. Whereas the prechordal plate and notochord have distinct vertical signaling properties, the initial anteroposterior (A‐P) pattern of the neural plate may be induced by planar signals originating from the organizer region. Planar signals from the notoplate may also contribute to the mediolateral (M‐L) patterning of the neural plate. These and other findings suggest a general view of neural induction and axial patterning. © 1993 John Wiley & Sons, Inc.
Pax: Gene regulators in the developing nervous system
Authors: Chalepakis Georges , Stoykova Anastassia , Wijnholds Jan , Tremblay Patrick , Gruss Peter
Published: January 2005

In recent years, the discovery of Pax genes in mouse has played an invaluable role in furthering our understanding in mouse developmental processes and disorders. To date, eight murine paired box‐containing genes have been cloned. Seven of these exhibit a distinct spationtemporal expression pattern in the developing nervous system implying a role in the regional specification of the developing spinal cord and brain. The Pax genes encode for sequence‐specific DNA binding transcription factors that play a key role in embryonic development. Three of these developmental control genes are altered in mutant mice and two are associated with human diseases. Disruption of these Pax genes leads to abnormalities in neural crest derivatives, neuroectoderm, sclerotome or myotome‐derived tissues. Disruption of the Pax‐3 gene causes the Splotch phenotype in mice and Waardenburg syndrome in humans. Pax‐6 mutations result in Small eye mice and the human genetic disorder aniridia. The Pax‐1 gene is mutated in undulated mice. Pax proteins can transform cells in culture which then form tumours following injection in nude mice. Consistent with this activity, PAX3 has been recently implicated in the generation of the tumour alveolar rhabdomyosarcoma. © 1993 John Wiley & Sons, Inc.
Claustrin, an antiadhesive neural keratan sulfate proteoglycan, is structurally related to MAP1B
Authors: Burg Michael A. , Cole Gregory J.
Published: January 2005

Our laboratory has recently identified a keratan sulfate proteoglycan (KSPG), named claustrin, that inhibits neural cell adhesion and neurite outgrowth in the chick nervous system. Antisera prepared against claustrin were used to screen a cDNA expression library from embryonic day 9 chick brain. Initial characterization of positive cDNAs revealed a high degree of homology to the mouse MAP1B gene, although these cDNAs represent a 5′ truncated fragment of MAP1B. Protein sequencing of three peptides derived from a tryptic digest of purified, keratanase‐treated claustrin also revealed strong homology to MAP1B, and confirmed the authenticity of the 3.4 kb claustrin cDNA. To further determine the relationship between these two proteins, we used antibodies against MAP1B and KSPGs in immunoblotting and immunohistochemical studies. These studies demonstrated cross‐reactivity between MAP1B and claustrin antibodies, and that monoclonal antibodies to cartilage keratan sulfate react with MAP1B in rat nervous tissue, and with claustrin in the chick nervous system. In addition, keratanase treatment of a taxol microtubule fraction from chick or rat brain eliminated MAP1B, as detected by immunoblotting with the MAP5 monoclonal antibody. These results suggest that MAP1B and claustrin are highly related, if not identical, proteins. 1994 John Wiley & Sons, Inc.
Central projection of auditory receptors in the prothoracic ganglion of the bushcricket Psorodonotus illyricus (tettigoniidae): Computer‐aided analysis of the end branch pattern
Authors: Ebendt Ruettger , Friedel Joerg , Kalmring Klaus
Published: January 2005

The projection patterns of morphologically and functionally identified auditory and auditory‐vibratory receptor cells of receptor organs (the crista acustica and the intermediate organ) in the foreleg of the tettigoniid Psorodonotus illyricus, were investigated with combined recording and staining techniques, and subsequent histological examination and morphometric measurements. With the application of a computer program (AutoCAD), three‐dimensional reconstructions of the axon end branches of receptor cells within the neuropile of the anterior Ring Tract (aRT) were made, in order to determine, the entire shape of each, the pattern and density of the end branches, and the positions of the target areas within the auditory neuropile. Clear differences for different functional types of receptors were found. 1994 John Wiley & Sons, Inc.
Galanin and vasoactive intestinal peptide messenger RNAs increase following axotomy of adult sympathetic neurons
Authors: Mohney Robert P. , Siegel Ruth E. , Zigmond Richard E.
Published: January 2005

The adult rat superior cervical ganglion (SSG) contains low levels of galanin‐ and vasoactive intestinal peptide‐(VIP) like immunoreactivity, with very few immuno‐stained principal neurons. Immunoreactivity for both neuropeptides increases in these neurons after explanation or postganglionic axotomy in vivo. Northern blot analysis had demonstrated concomitant increases in mRNAs encoding these peptides. To localize cells in axotomized ganglia which increase their expression of these mRNAs, we performed in situ hybridization studies. In control SCG, only a few principal neurons contained mRNA for either galanin or VIP. After 48 h in organ culture, galanin mRNA was expressed in the majority of principal neurons. At 48 h after in vivo axotomy of both postganglionic trunks of the SCG, the internal and external carotid nerves, the distribution and number of neurons expressing galanin mRNA increased similarly to that seen in culture. Lesioning either trunk alone produced increases in galanin mRNA localized to those regions of the ganglion containing neurons that project into the lesioned trunk. Transection of the predominantly preganglionic cervical sympathetic trunk increased galanin mRNA expression in a small population of neurons that nerve trunk. The distributions of these labeled neurons, together with previous neuroanatomical studies, suggests that they had been axotomised by the lesions. Similar studies examining VIP mRNA expression demonstrated that although considerably fewer VIP mRNA expressing neurons than galanin mRNA expressing neurons were present after axotomy, the distribution of neuropeptide mRNA‐positive cells were similar in both cases. These observations suggest that increases in the peptide galanin and VIP after nerve transection result from changes in the levels of their mRNAs in those neurons that have been axotomized. 1994 John Wiley & Sons, Inc.
Regulation of vasoactive intestinal peptide expression in sympathetic neurons in culture and after axotomy: The role of cholinergic differentiation factor/leukemia inhibitory factor
Authors: Sun Yi , Rao Mahendra S. , Zigmond Richard E. , Landis Story C.
Published: January 2005

Vasoactive intestinal peptide (VIP) expression increases in sympathetic neurons when they are grown in dissociated cell or explant cultures and when they are axotomizedin vivo. In dissociated cell culture, the magnitude of the VIP increase was reduced when nonneuronal cells were removed and medium conditioned by ganglionic nonneuronal cells increased VIP in neuron‐enriched cultures. Antiserum Against cholinergic differentiation factor (also leukemia inhibitory factor; CDF/LIF), but not against ciliary neurotrophic factor, immunoprecipitated this activity. Medium conditioned by sympathetic ganglion explants also contained a VIP‐stimulatory molecule that was immunoprecipitated by CDF/LIF antiserum, and CDF/LIF antiserum partially blocked VIP induction in explants. CDF/LIF mRNA was increased in dissociated cell cultures, in ganglion explants andin vivoafter axotomy. Our results suggest that CDF/LIF released from ganglionic nonneuronal cells plays an important role in regulating VIP after axotomy. 1994 John Wiley & Sons, Inc.