bluuebunny/crossref_metadata_2025_split huggingface dataset:
High vocal center growth and its relation to neurogenesis, neuronal replacement and song acquisition in juvenile canaries
Authors: Alvarez‐Buylla Arturo , Ling Chang‐Ying , Nottebohm Fernando 
Published: January 2005

AbstractIt is generally thought that most circuits of the adult central nervous system (CNS) are sculpted, in part at least, by selective elimination of some of the neurons present in an initial overabundant set. In this scenario, the birth of neurons precedes the period when brain functions, such as learning, first occur. In contrast to this form of brainassembly, we describe here the delayed development of the high vocal center (HVC) and one of its efferent pathways in canaries. The retrograde tracer Fluoro‐Gold (FG) was injected into one of HVC's two efferent targets, the nucleus robustus archistriatalis (RA), to define the boundaries of HVC. The HVC grows markedly between 1 and 4 months, invading neighboring territories of the caudal telencephalon. During this same period, 0.43%–0.64% of the HVC neurons present at 1 year of age are labeled per day of [3H]‐thymidine injection. [3H]‐Thymidine labeling is a marker of cell birth, and during the first 4 months HVC neuron number increases, probably accounting for part of the HVC growth observed. Thereafter, the number of HVC neurons remains constant, but neuronal birth persists. We infer from this that neuronal replacement starts as early as 4 months after hatching and perhaps before then. About half of the neurons born after posthatching day 10 grow an axon to RA to form the main efferent pathway exiting from HVC. HVC growth, neurogenesis, axogenesis, and the observed replacement of neurons happen during the period of juvenile vocal learning. However, the recruitment of neurons that are still present at 1 year shows no particular inflections corresponding to the various stages in song learning, and continues at essentially the same rate after the more stereotyped adult song has been acquired. We suggest that a combination of neurogenesis and neuronal replacement provides unique advantages for learning.
Development of coordinated movement in chicks: II. Temporal analysis of hindlimb muscle synergies at embryonic day 10 in embryos with spinal gap transections
Authors: Bradley N. S. , Bekoff A. 
Published: January 2005

AbstractSpinal neural circuits can recruit muscles to produce organized patterns of activity early in embryonic development. In a previous study, using multichannel electromyographic (EMG) recordings, we characterized burst parameters for these patterns in the legs of chick embryos during spontaneous motility in ovo at embryonic days (E) 9 and E10 (Bradley and Bekoff, 1990). Results of the study suggested both neural and biomechanical factors play an important role in the development of coordinated limb movements. In this study, to explore the contribution of descending neural inputs to the control of leg movements during motility, we applied similar methods to characterize motor patterns produced by the spinal cord in the absence of descending inputs. Thoracic spinal gap transections were performed at E2 and EMG patterns were recorded at E10. Several EMG features for chronic spinal embryos were similar to those for normal embryos and demonstrate that lumbar spinal circuits can be correctly assembled to control limb movements in the absence of connectivity with more rostral neural structures during early differentiation processes. However, certain aspects of the EMG patterns in chronic spinal embryos were different from patterns in normal embryos and provide support for conclusions drawn earlier by Oppenheim (1975). Specifically, our data support the view that propriospinal and/or supraspinal inputs function to regulate the timing of cyclic limb movements controlled by spinal neural circuits. Finally, we consider the possible long‐term effects of chronic spinal gap transections as compared to acute spinal transections on the development of motility. © 1992 John Wiley & Sons, Inc.
The role of matrix molecules in regeneration of leech CNS
Authors: Masuda‐Nakagawa L. M. , Wiedemann C. 
Published: January 2005

AbstractExtracellular matrix (ECM) molecules extracted from the leech central nervous system (CNS) provide substrates that induce extensive growth of processes of identified leech nerve cells in culture. Two ECM molecules, laminin and tenascin, have been identified. The laminin‐like molecule has been purified and shown to be a cross‐shaped molecule similar to vertebrate laminin with subunits of 340, 220, 180, and 160 kD. Purified laminin as a substrate induces rapid outgrowth of Retzius (R) and Anterior Pagoda (AP) cells in culture. The tenascin molecule has been partially purified. In electronmicrographs, leech tenascin, like vertebrate tenascin, has six arms of equal size joined in a central globule. Highly enriched fractions of leech tenascin induce rapid and extensive outgrowth of Retzius and AP cells in culture. Substrate molecules not only induce outgrowth of processes but also affect the growth patterns of individual nerve cells. Neurites are straight with few branches in laminin, but curved with profuse branches on tenascin. During regeneration of the CNS in the animal, laminin appears at new sites associated with growth cones. The appearance of laminin correlates with the accumulation of microglial cells. Thus, ECM molecules with growth‐promoting activity for leech nerve cells in vitro appear to be involved in inducing regeneration and allowing the neurites to reconnect with former targets. © 1992 John Wiley & Sons, Inc.
Evidence that synaptic transmission between giant interneurons and identified thoracic interneurons in the cockroach is cholinergic
Authors: Casagrand Janet L. , Ritzmann Roy E. 
Published: January 2005

AbstractIn the cockroach, a population of thoracic interneurons (TIs) receives direct inputs from a population of ventral giant interneuons (vGIs). Synaptic potentials in type‐A TIs (TIAs) follow vGI action potentials with constant, short latencies at frequencies up to 200 Hz. These connections are important in the integration of directional wind information involved in determining an oriented escape response. The physiological and biochemical properties of these connections that underlie this decision‐making process were examined. Injection of hyperpolarizing or depolarizing current into the postsynaptic TIAs resulted in alterations in the amplitude of the postsynaptic potential (PSP) appropriate for a chemical connection. In addition, bathing cells in zero‐calcium, high magnesium saline resulted in a gradual decrement of the PSP, and ultimately blocked synaptic transmission, reversibly. Single‐cell choline acetyltransferase (ChAT) assays of vGI somata were performed. These assays indicated that the vGIs can synthesize acetylcholine. Further more, the pharmacological specificity of transmission at the vGI to TIA connections was similar to that previously reported for nicotinic, cholinergic synapses in insects, suggesting that the transmitter released by vGIs at these sypapses is acetylcholine. © 1992 John Wiley & Sons, Inc.
Ipsilateral retinal projections into the tectum during regeneration of the optic nerve in the cichlid fish Haplochromis burtoni: A dil study in fixed tissue
Authors: Wilm Claudia , Fritzsch Bernd 
Published: January 2005

AbstractRetinal projections were experimentally manipulated in a bony fish to reveal conditions under which considerably enlarged ipsilateral projections developed and persisted. Three experimental groups were studied: animals after unilateral enucleation, after unilateral nerve crush, and after enucleation and crush of the remaining optic nerve. At 29 days after unilateral enucleation alone, no enhanced ipsilateral projection had developed. After nerve crush, however, large numbers of retinal fibers regenerated into the ipsilateral tectum. Retrogradely filled, ipsilaterally projecting ganglion cells were distributed throughout the entire retina. After 15 days regenerating retinal fibers covered the entire ipsilateral tectum. At later stages the ipsilateral projection showed progressive reduction in coverage of the tectum. Combining enucleation with nerve crush led to an ipsilateral projection that covered the tectum at 28 days and later. In this experimental situation the development of an ipsilateral projection appears to be a two‐step process: (1) Fibers are rerouted to the ipsilateral side at the diencephalon, and (2) ipsilateral fibers persist in the tectum only in the absence of a contralateral projection while they appear to be eliminated in the other cases. © 1992 John Wiley & Sons, Inc.
Synaptic plasticity in a regenerated crayfish phasic motoneuron
Authors: Stewart Bryan A. , Atwood Harold L. 
Published: January 2005

AbstractCrustacean neuromuscular systems provide many advantages for the study of synaptic transmission and plasticity. The present study examines aspects of synaptic transmission in the phasic, fast closer excitor (FCE) motoneuron of regenerated crayfish claws. Excitatory postsynaptic potentials (EPSPs) fatigued rapidly and showed poor long‐term facilitation (LTF) in the smallest of regenerating claws. EPSPs in larger regenerating claws fatigued less and showed pronounced facilitation. These observations were not the same as those previously made during primary development of this motoneuron (Lnenicka and Atwood, 1985a, J. Neuroscience 5:459–467). Hence, regeneration is not the recapitulation of primary development. In situ stimulation of the FCE is known to lead to long‐lasting adaptation of synaptic performance. This adaptation is age dependent; it is expressed in young but not old animals. In the regenerated FCE of old animals, we observed a novel form of long‐lasting adaptation to imposed activity: EPSPs showed large initial EPSPs and did not exhibit resistance to fatigue during maintained stimulation. This indicates that aged motoneurons can express adaptive changes to increased activity following axonal regeneration, but that the adaptive changes are the opposite to what is observed in nonregenerated motoneurons. © 1992 John Wiley & Sons, Inc.
Electric organ morphology of Sternopygus macrurus, a wave‐type, weakly electric fish with a sexually dimorphic EOD
Authors: Mills Alice , Zakon Harold H. , Marchaterre Margaret A. , Bass Andrew H. 
Published: January 2005

AbstractIn several species of electric fish with a sex difference in their pulse‐type electric organ discharge (EOD), the action potential‐generating cells of the electric organ (electrocytes) of males are larger and more invaginated compared to females. Androgen treatment of females and juveniles produces a longer‐duration EOD pulse that mimics the mature male EOD, with a concurrent increase in electrocyte size and/or membrane infolding. In Sternopygus macrurus, which generates a wave‐type EOD, androgen also increases EOD pulse duration. To investigate possible morphological correlates of hormone‐dependent changes in EOD in Sternopygus, we examined electric organs from both fish collected in the field, and untreated and androgen‐treated specimens in the laboratory. The electrocytes are cigar shaped, with prominent papillae on the posterior, innervated end. Electrocytes of field‐caught specimens were significantly larger in all parameters than were electrocytes of specimens maintained in the laboratory. EOD pulse duration and frequency were highly correlated, and were significantly different between the sexes in sexually mature fish. Nevertheless, no sex difference in electrocyte morphology was observed, nor did any parameters of electrocyte morphology correlate with EOD pulse duration or frequency. Further, whereas androgen treatment significantly lowered EOD frequency and broadened EOD pulse duration, there was no difference in electrocyte morphology between hormone‐treated and control groups. Thus, in contrast to results from studies on both mormyrid and gymnotiform pulse fish, electrocyte morphology is not correlated with EOD waveform characteristics in the gymnotiform wave‐type fish Sternopygus. The data, therefore, suggest that sex differences in EOD are dependent on changes in active electrical properties of electrocyte membranes. © 1992 John Wiley & Sons, Inc.
Normal and abnormal pathfinding of facial nerve fibers in the chick embryo
Authors: von Bartheld Christopher S. , Yang Wenhua , Rubel Edwin W. 
Published: January 2005

AbstractDevelopment of the facial nerve was studied in normal chicken embryos and after surgical disruption of ingrowing sensory facial nerve fibers at 38–72 h of incubation. Disruption of facial nerve fibers by otocyst removal often induced a rostral deviation of the facial nerve and ganglion to the level of the trigeminal ganglion. Cell bodies of the geniculate ganglion trailed their deviating neurites and occupied an abnormal rostral position adjacent to the trigeminal ganglion. Deviating facial nerve fibers were labeled with the carbocyanine fluorescent tracer Dil in fixed tissue. Labeled fibers penetrated the cranium adjacent to the trigeminal ganglion, but they did not follow the trigeminal nerve fibers into the brain stem. Rather, after entering the cranium, they projected caudally to their usual site of entrance and proceeded towards their normal targets. This rostral deviation of the facial nerve was observed only after surgery at 48–72 h of incubation, but not in cases with early otocyst removal (38–48 h). A rostral deviation of the facial nerve was seen in cases with partial otocyst removal when the vestibular nerve was absent. The facial nerve followed its normal course when the vestibular nerve persisted. We conclude that disruption of the devloping facial pathway altered the routes of navigating axons, but did not prevent pathfinding and innervation of the normal targets. Pathfinding abilities may not be restricted to pioneering axons of the facial nerve; later‐developing facial nerve fibers also appeared to have positional information. Our findings are consistent with the hypothesis that navigating axons may respond to multiple guidance cues during development. These cues appear to differ as a function of position of the navigating axon. © 1992 John Wiley & Sons, Inc.
SSB, an antigen that selectively labels morphologically distinct synaptic boutons at the Drosophila larval neuromuscular junction
Authors: Budnik Vivian , Gorczyca Michael 
Published: January 2005

AbstractIn this report we describe the expression of Small Synaptic Bouton (SSB), an antigen that is selectively expressed in a specific subset of neuromuscular junction terminals in the body wall of Drosophila larva. The expression of SSB was studied with a polyclonal antibody raised against the cAMP phosphodiesterase of the Drosphila learning mutant dunce (Nighorn et al., 1991, Neuron 6:455–467); however, immunoreactivity was not abolished by the dunce (dnc) alleles dncM14 and dncM11 or deficiencies of the dnc gene, indicating that the antigen labelled could not be the dnc gene product, but another antigen that we termed SSB. Immunoreactivity was localized in the body wall muscles to a specific subset of neuromuscular junction terminals that have been implicated in activity‐dependent plasticity. This demonstrates that these morphologically distinct terminals can be immunocytochemically distinguished and that they probably represent innervation by a distinct neuronal population. Confocal and electron microscopic examination demonstrated that staining was restricted to the synaptic boutons themselves, not to neurites or motor axons. Ultrastructural analysis showed label close to synaptic vesicles in the presynaptic terminal and in the surrounding subsynaptic reticulum. Central nervous system (CNS) staining was restricted to a segmentally repeated pattern of cell bodies in the ventral ganglion and to a few small groups of cells in the brain lobes. © 1992 John Wiley & Sons, Inc.
Rapid and protracted phases of retinal ganglion cell loss follow axotomy in the optic nerve of adult rats
Authors: Villegas‐Pérez Maria‐Paz , Vidal‐Sanz Manuel , Rasminsky Michael , Bray Garth M. , Aguayo Albert J. 
Published: January 2005

AbstractTo investigate the short‐and long‐term effects of axotomy on the survival of central nervous system (CNS) neurons in adult rats, retinal ganglion cells (RGCs) were labelled retrogradely with the persistent market diI and their axons interrupted in the optic nerve (ON) by intracranial crush 8 or 10 mm from the eye or in intraorbital cut 0.5 or 3 mm from the eye. Labelled RGCs were counted in flat‐mounted retinas at intervals from 2 weeks to 20 months after axotomy. Two major patterns of RGC loss were observed: (1) an inital abrupt loss that was confined to the first 2 weeks after injury and was more severe when the ON was cut close to the eye; (2) a slower, persistent decline in RGC densities with one‐half survival times that ranged from approximately 1 month after intraorbital ON cut to 6 months after intracranial ON crush. A small population of RGCs (approximately 5%) survived for as long as 20 months after intraorbital axotomy. The initial loss of axotomized RGCs presumably results from time‐limited perturbations related to the position of the ON injury. A. persistent lack of terminal connectivity between RGCs and their targets in the brain may contribute to the subsequent, more protracted RGC loss, but the differences between intraorbital cut and intracranial crush suggest that additional mechanisms are involved. It is unclear whether the various injury‐related processes set in motion in both the ON and the retina exert random effects on all RGCs or act preferentially on subpopulations of these neurons. © 1993 John Wiley & Sons, Inc.
Gene elav of Drosophila melanogaster: A prototype for neuronal‐specific RNA binding protein gene family that is conserved in flies and humans
Authors: Yao Kwok‐Ming , Samson Marie‐Laure , Reeves Ronald , White Kalpana 
Published: January 2005

AbstractRegulated gene activity is crucial to the formation and function of the nervous system. It is well known that gene regulation can occur at the transcriptional, post‐transcriptional, translational, and post‐translational levels. In this review our focus has been on the post‐transcriptional regulation in neurons and on neural‐specific RNA binding proteins that may be involved in post‐transcriptional modulation of gene activity. We have taken advantage of this opportunity to review our work on the elav gene of Drosophila melanogaster which encodes a neural‐specific RNA binding protein and relate it to other members of this elav‐like gene family. We report new data that suggests that elav is post‐transcriptionally regulated and we demonstrate that below‐threshold levels of ELAV protein severely affects neuronal differentiation. © 1993 John Wiley & Sons, Inc.
Neuronal specificity and its development in the Drosophila wing disc and its derivatives
Authors: Palka John 
Published: January 2005

AbstractThe imaginal wing disc of flies gives rise to the adult wing blade and dorsal thorax (notum). A great deal has been learned in recent years about the process of neurogenesis in this disc; a number of genes that play crucial roles in the formation of sensory mother cells and in the differentiation of the sensory organs have been identified and their roles defined. Given this extensive background of developmental genetics, it has seemed profitable to summarize what is known about the end‐products of neural development, the adult sensory organs. Discussed are their physiological function and role in behavior, the pathways followed by their axons in the CNS, and both genes and epigenetic processes that might play some role in the later stages of neural development and in adult function. The highly individual characteristics of certain of the sensory organs is emphasized, both in the context of their adult roles and as a challenge for future studies in developmental genetics. © 1993 John Wiley & Sons, Inc.
Molecules and cognition: The latterday lessons of levels, language, and iac. Evolutionary overview of brain structure and function in some vertebrates and invertebrates
Authors: Miklos George L. Gabor 
Published: January 2005

AbstractThe characteristics of the nervous systems of a number of organisms in different phyla are examined at the recombinant DNA, protein, neuroanatomic, neurophysiological, and cognitive levels. Among the invertebrates, special attention is paid to the advantages as well as the shortcomings of the fly Drosophila melanogaster, the worm Caenorhabditis elegans, the honey bee Apis mellifera, the sea hare Aplysia californica, the octopus Octopus vulgaris, and the squid Loligo pealei. Among vertebrates, the focus is on Homo sapiens, the mouse Mus musculus, the rat Rattus norvegicus, the cat Felis catus, the macaque monkey Macaca fascicularis, the barn owl Tyto alba, and the zebrafish Brachydanio rerio. Vertebrate nervous systems have also been compared in fossil vs. extant organism. I conclude that complex nervous systems arose in the Early Cambrian via a big bang that was underpinned by a modular method of construction involving massive pleiotropy of gene circuits. This rapidity of construction had enormous implications for the degrees of freedom that were subsequently available to evolving nervous systems. I also conclude that at the level of neuronal populations and interactions of neuropiles there is no model system between phyla except at the basic macromolecular level. Further, I argue that to achieve a significant understanding of the functions of extant nervous systems we need to concentrate on fewer organisms in greater depth and manipulate genomes via transgenic technologies to understand the behavioral outputs that are possible from an organism. Finally, I analyze the concepts of “perceptual categorization” and “information processing” and the difficulties involved in the extrapolation of computer analogies to sophisticated nervous systems. © 1993 John Wiley & Sons, Inc.
Regenerating retinal fibers display error‐free homing along undamaged normal fibers
Authors: Wilm Claudia , Fritzsch Bernd 
Published: January 2005

AbstractAfter crushing one optic nerve in a bony fish, retinal fibers regenerate to both tecta. Anterograde labelling indicates that the ipsilaterally regenerating fibers have a rather straight growth, apparently along the undamaged fibers of the contralateral retina. In contrast, the contralaterally regenerating fibers deviate widely from a straight course. Retrograde labelling shows a mirror‐symmetric distribution of regenerated ipsilateral and resident contralateral ganglion cells in a comparable annulus. In contrast, ganglion cells in the regenerated contralateral retina show no topological order after comparable small Dil applications to the ventrolateral tectum. These data suggest that regenerating fibers can orient on the undisturbed, contralateral fibers. © 1993 John Wiley & Sons, Inc.