bluuebunny/crossref_metadata_2025_split huggingface dataset:
Castration and antisteroid treatment impari vocal learning in male zebra finches
Authors: Bottjer Sarah W. , Hewer Samantha J. 
Published: January 2005

AbstractBoth song behavior and its neural substrate are hormone sensitive: Castrated adult male zebra finches need replacement of gonadal steroids in order to restore normal levels of song production, and sexsteroids are necessary to establish male‐typical neural song‐controlcircuits during early development. This pattern of results suggests that hormones may be required for normal development of learned songbehavior, but evidence that steroids are necessary for normal neuraland behavioral development during song learning has been lacking. Weaddressed this question by attempting to eliminate the effects of gonadal steroids in juvenile male zebra finches between the time of initial song production and adulthood. Males were castrated at 20 daysof age and received systemic implants of either an antiandrogen (flutamide). an antiestrogen (tamoxifen), or both drugs. The songs of both flutamide‐and tamoxifen‐treated birds were extremely disrupted relative to normal controls in terms of the stereotypy and acoustic quality of individual note production, as well as stereotypy of the temporal structure of the song phrase. We did not discern any differences in the pattern of behavioral disruption between birds that were treated with either flutamide, tamoxifen, or a combination of both drugs. Flutamide treatment resulted in a reduced size of two forebrain nuclei that are known to play some role unique to early phases of song learning [lateral magnocellular nucleus of the anterior neostriatum (IMAN) and area X (X)], but did not affect the size of two song‐control nuclei that are necessary for normal song productionin adult birds [caudal nucleus of the ventral hyperstriatum (HVc) and robust nucleus of the archistriatum (RA)]. In contrast, treatment with tamoxifen did not result in any changes in the size of song‐control nuclei relative to normal controls, and it blocked the effects of flutamide on the neural song‐control system in birds that were treated with both drugs. Castration and antisteroid treatment exerted no deleterious effects on the quality of song behavior in adult birds, indicating that gonadal hormones are necessary for the development of normal song behavior during a sensitive period. © 1992 John Wiley & Sons, Inc.
Consequences of slow wallerian degeneration for regenerating motor and sensory axons
Authors: Brown M. C. , Lunn E. R. , Perry V. H. 
Published: January 2005

AbstractThe time course of Wallerian degeneration in the tibial and saphenous nerves was compared in Balb/c mice and mice of the C57BL/Ola strain (Lunn et al., 1989). Axons, particularly myelinated ones, in nerves of C57BL/Ola mice are very slow to degenerate, many still being present 3 weeks after axotomy. Nuclear numbers in the distal stump peak much later and do not reach the levels found in Balb/c mice; debris removal is very slow, and Schwann cell numbers only rise slightly above normal levels in the long term. Regeneration was investigated electrophysiologically and by electron microscopy (EM). Myelinated sensory axons regenerated slowly and incompletely compared with motor ones which were only slightly slowed after nerve crush (although they were significantly hindered after nerve section). Total myelinated axon numbers were still some 20% less than normal even after 200 days in sensory nerves. Even after all axons had degenerated in C57BL/Ola mice, regeneration rates of neither myelinated nor unmyelinated sensory axons reached those achieved in Balb/c mice. It is concluded that while regeneration can eventually proceed slowly when Wallerian degeneration is much delayed, the usual rapid time course of Wallerian degeneration is necessary if axons, particularly sensory ones, are to regenerate at optimal rates and to maximum extent. Whilelocal obstruction to axon growth probably impedes the early phase ofregeneration in C57BL/Ola mice, it seems possible that a lack of adequate early signals affects regeneration permanently by minimizing the cell body reaction to injury. © 1992 John Wiley & Sons, Inc.
Development of gabaergic connections in vitro: Increasing efficacy of synaptic transmission is not accompanied by changes in miniature currents
Authors: Kraszewski K. , Grantyn R. 
Published: January 2005

AbstractDevelopment of inhibitory synaptic transmission was studied using a dissociated cell culture from the superior colliculus of neonatal rat. Patch‐clamp recordings in the whole‐cell configuration were performed to measure evoked (single‐cell‐activated) inhibitory postsynaptic currents (IPSCs), miniature IPSCs and current responses to maximal concentrations of exogenous γ‐aminobutyric acid (GABA). Over a period of 3 weeks in vitro (DIV3‐24), the fraction of synaptically coupled neurons raised from 0% to 76%. Evoked IPSCs were first observed at DIV5. They had an average amplitude of 33.9 pA during the first week (n = 13) and 129.7 pA during the fourth week (n = 48). This increase by a factor of 3.8 represents a significant rise in the efficacy of GABAergic transmission during in vitro development. However, no developmental change has been observed in the average amplitudes of miniature somatic IPSCs. The latter remained at an average level of about 9 pA (symmetrical chloride concentration and a driving force of 68 mV). No increase was found also in whole‐cell current densities induced by saturating concentrations of exogenous GABA. Our results suggest that under the given conditions, synapse maturation was primarily the result of presynaptic sprouting. This conclusion is further supported by bouton counts in immunostained collicular cultures, where the number of axosomatic and axodendritic GABAergic contacts per neuron increased from 0.54 and 0.37, respectively, at DIV3, to 13.84 and >23.1, at DIV24. The overall density of GABAergic neurons decreased during this period from about 41,000/cm2 to 15,600 cm2, indicating that a growing number of contacts is formed by a declining number of presynaptic neurons. © 1992 John Wiley & Sons, Inc.
Establishment of mouse‐immortalized hybrid clones expressing characteristics of differentiated neurons derived from the cerebellar and brain stem regions
Authors: Satoh Jun‐Ichi , Gallyas Ferenc , Endoh Masumi , Yamamura Takashi , Kunishita Tatsuhide , Kobayashi Takayoshi , Tabira Takeshi 
Published: January 2005

AbstractTwo clonal immortalized neurons designated CL8c47 and CL8a5.2 were established by somatic cell fusion between a hypoxanthine phosphoribosyltransferase (HPRT−) deficient neuroblastoma N18TG2 and newborn mouse cerebellar/brain stem neurons. In the serum‐containing medium without extra differentiating agents, both clones exhibited a morphology of differentiated neurons. They contained high levels of glutamate but no gamma‐aminobutyric acid (GABA). The CL8a5.2 clone synthesized choline aceryltransferase and serotonin. In immunocytochemical studies, both clones expressed 200 kD neurofilament protein neuron‐specific enolase, microtubule‐associated protein 2 (MAP2), tau protein, neuronal cell adhesion molecule (N‐CAM), HNK‐1, Thy‐1.2, saxitoxin‐binding sodium channel protein, and glutamate. Synaptophysin immunoreactivity was identified in the neuritic terminals of CL8c4.7 cells. Most of these antigens were barely detectable on N18TG2 cells. Electrophysiologically, both clones generated action potentials in response to electrical stimuli. The hybrid clones that express characteristics of differentiated neurons derived from the cerebellar and brain stem regions might be invaluable for the study of the molecular basis of neuronal differentiation and degeneration in these regions. © 1992 John Wiley & Sons, Inc.
GAP‐43 phosphorylation is dynamically regulated in individual growth cones
Authors: Dent Erik W. , Meiri Karina F. 
Published: January 2005

AbstractIn vivo, kinase C phosphorylation of the growth‐associated protein GAP‐43 is spatially and temproally associated with the proximity of growing axons to their targets. Here we have used dissociated dorsal root ganglia (DRG)s and an antibody specific for the phosphorylated form of GAP‐43 to demonstrate that neurite regeneration in culture also begins in the absence of detectable levels of phosphorylated GAP‐43. Since the β isoform of kinase C was found to be enriched in growth cones before stably phosphorylated GAP‐43 was detected, it may normally be inactive during initial neurite outgrowth; however, premature phosphorylation of GAP‐43 could be stimulated in newly dissociated DRGs by plating them on cultures in which phosphorylation had already been initiated; media conditioned by such cultures caused no response suggesting an effect of either cell‐cell or cell‐substrate contact. Increased GAP‐43 phosphorylation correlated with a reduced extent of neurite outgrowth but not with the rate at which individual growth cones translocated so that motile growth cones contained very low levels of phosphorylated GAP‐43, whereas stationary growth cones showed much more immunoreactivity. Downregulation of kinase C by phorbol ester prevented increased GAP‐43 phosphorylation and led to growth cone collapse. Finally, phosphorylated GAP‐43 was found to be differently distributed within growth cones. Increased immunoreactivity was frequently observed in the neck of the growth cone and was heterogeneously distributed in lamellae and filopodia. These results, which demonstrate the dynamic regulation of GAP‐43 phosphorylation in individual growth cones, are discussed with reference to the association between changes in growth cone shape and the ability to translocate and change direction. © 1992 John Wiley & Sons, Inc.
Mechanism of inhibitory action of capsaicin on particulate axoplasmic transport in sensory neurons in culture
Authors: Kawakami Tadashi , Hikawa Naoshi , Kusakabe Tatsumi , Kano Masato , Bandou Yoko , Gotoh Hideki , Takenaka Toshifumi 
Published: January 2005

AbstractThe inhibitory effect of capsaicin on axoplasmic transport in cultured dorsal root ganglion cells was analyzed by video‐enhanced contrast microscopy. Capsaicin inhibited particle transports in a dose‐dependent manner, irrespective of the diameter of axons. The effect of capsaicin was reversible at low concentrations. Capsaicin affected both the anterograde and retrograde transport. Large organelles were more sensitive to capsaicin than small ones in the retrograde transport. An experiment using calcium‐sensitive dye, Fura 2, indicated that capsaicin raised the intraneuronal free calcium concentration preceding the inhibition of the transport. Electron microscopy revealed that microtubules and neurofilaments are disorganized and disoriented by capsaicin. We reached a conclusion that capsaicin inhibits fast axoplasmic transport of both anterograde and retrograde directions in all types of somatosensory neurons in culture by disorganizing intraaxonal cytoskeletal structures, through the elevated intracellular Ca2+ concentration. © 1993 John Wiley & Sons, Inc.
Approaches to identify genes involved in Drosophila embryonic CNS development
Authors: Noll Elizabeth , Perkins Lizabeth A. , Mahowald Anthony P. , Perrimon Norbert 
Published: January 2005

AbstractMany of the steps involved in formation of the Drosophila embryonic central nervous system (CNS) have been identified by both descriptive and experimental studies. In this review we will describe the various approaches that have been used to identify molecules involved in CNS development and the advantages and disadvantages of each of them. Our discussion will by no means be exhaustive; but rather we will discuss our experiences with each approach and provide an overview of what has been learned by using these methodologies. Finally, we will discuss methods that have been recently developed and how they are likely to provide further insight into CNS development. © 1993 John Wiley & Sons, Inc.
Cellular mechanisms governing synaptic development in Drosophila melanogaster
Authors: Keshishian Haig , Chiba Akira , Chang Te Ning , Halfon Marc S. , Harkins Elizabeth W. , Jarecki Jill , Wang Lansheng , Anderson Marydilys , Cash Sydney , Halpern Marnie E. , Johansen Jørgen 
Published: January 2005

AbstractThe neuromuscular connections of Drosophila are ideally suited for studying synaptic function and development. Hypotheses about cell recognition can be tested in a simple array of pre‐and postsynaptic elements. Drosophila muscle fibers are multiply innervated by individually identifiable motoneurons. The neurons express several synaptic cotransmitters, including glutamate, proctolin, and octopamine, and are specialized by their synaptic morphology, neurotransmitters, and connectivity. During larval development the initial motoneuron endings grow extensively over the surface of the muscle fibers, and differentiate synaptic boutons of characteristic morphology. While considerable growth occurs postembryonically, the initial wiring of motoneurons to muscle fibers is accomplished during mid‐to‐late embryogenesis (stages 15–17). Efferent growth cones sample multiple muscle fibers with rapidly moving filopodia. Upon reaching their target muscle fibers, the growth cones rapidly differentiate into synaptic contacts whose morphology prefigures that of the larval junction. Mismatch experiments show that growth cones recognize specific muscle fibers, and can do so when the surrounding musculature is radically altered. However, when denied their normal targets, motoneurons can establish functional synapses on alternate muscle fibers. Blocking synaptic activity with either injected toxins or ion channel mutants does not derange synaptogenesis, but may influence the number of motor ending processes. The molecular mechanisms governing cellular recognition during synaptogenesis remain to be identified. However, several cell surface glycoproteins known to mediate cellular adhesion events in vitro are expressed by the developing synapses. Furthermore, enhancer detector lines have identified genes with expression restricted to small subsets of muscle fibers and /or motoneurons during the period of synaptogenesis. These observations suggest that in Drosophila a mechanism of target chemoaffinity may be involved in the genesis of stereotypic synaptic wiring. © 1993 John Wiley & Sons, Inc.
Temporal patterning of song production: Participation of nucleus uvaeformis of the thalamus
Authors: Williams Heather , Vicario David S. 
Published: January 2005

AbstractBirdsong is a learned vocal behavior used in intraspecific communication. The motor pathway serving learned vocalizations includes the forebrain nuclei NIf, HVC, and RA; RA projects to midbrain and brain stem areas that control the temporal and acoustic features of song. Nucleus Uvaeformis of the thalamus (Uva) sends input to two of these forebrain nuclei (NIf and HVC) but has not been thought to be important for song production. We used three experimental approaches to reexamine Uva's function in adult male zebra finches. (1) Electrical stimulation applied to Uva activated HVC and the vocal motor pathway, including tracheosyringeal motor neurons that innervate the bird's vocal organ. (2) Bilateral lesions of Uva including the dorso‐medial portion of the nucleus affected the normal temporal organization of song. (3) Chronic multiunit recordings from Uva during normal song and calls show bursts of premotor activity that lead the onset of some song components, and also larger bursts that mark the end of complete song motifs. These results implicate Uva in the production of learned vocalizations, and further suggest that Uva contributes more to the temporal structure than to the acoustic characteristics of song. © 1993 John Wiley & Sons, Inc.
Dendritic reduction in Passover, a Drosophila mutant with a defective giant fiber neuronal pathway
Authors: Baird Douglas H. , Koto Mary , Wyman Robert J. 
Published: January 2005

AbstractThe jump response to a light‐off startle stimulus in Drosophila melanogaster occurs when the Giant Fiber (GF), a neuron descending from the brain to the thorax, drives the jump (tergotrochanteral) muscle motorneuron (TTMn). Nonjumping mutants have been isolated in which this response is disrupted. Flies bearing the X‐chromosome mutation Passover (Pas) fail to jump in response to a light‐off stimulus, and electrical stimulation of the GF in the brain no longer elicits the normal response in the TTM. We have used retrograde HRP labelling to examine the TTMn motorneuron in wild‐type flies and in a variety of newly identified Pas alleles. In wild type the medial branch (MB) of the TTMn has an extensive region of apposition with the GF. In Pas alleles, there is a general reduction in anterior‐posterior (A‐P) extent of the medial branch but not of the posterior branch. Nevertheless, Pas alleles usually leave the TTMn close enough to the GF so that contact would not be precluded. In flies carrying a particular deficiency of Pas, Df(1) 16–3–22, including Pas/Df(1) 16–3–22 heterozygotes, there can be extensive growth of the medial branch including a contralateral projection; these heterozygotes have more than the normal amount of overlap between the GF and the TTMn. This phenotype, originally ascribed to Pas mutants, is associated with Df(1) 16–3–22, but not with other deletions of the Pas gene. The driving of the TTMn by the GF is defective in mutant genotypes with extensive medial branches as well as in mutants where GF‐TTMn contact is reduced. The fact that the TTMn grows into its normal synaptic region in mutant genotypes, but the GF pathway functions abnormally suggests that pathfinding by the TTMn is not impaired. It is more likely that the Pas mutation disrupts cell recognition, synaptogenesis, or synaptic function in the TTMn or its presynaptic partners. © 1993 John Wiley & Sons, Inc.
Differential ultrastructure of synaptic terminals on ventral longitudinal abdominal muscles in Drosophila larvae
Authors: Atwood H. L. , Govind C. K. , Wu C.‐F. 
Published: January 2005

AbstractThe innervation of ventral longitudinal abdominal muscles (muscles 6, 7, 12, and 13) of third‐instar Drosophila larvae was investigated with Nomarski, confocal, and electron microscopy to define the ultrastructural features of synapse‐bearing terminals. As shown by previous workers, muscles 6 and 7 receive in most abdominal segments “Type I” endings, which are restricted in distribution and possess relatively prominent periodic terminal enlargements (“boutons”); whereas muscles 12 and 13 have in addition “Type II” terminals, which are more widely distributed and have smaller “boutons.” Serial sectioning of the Type I innervation of muscles 6 and 7 showed that two axons with distinctive endings contribute to it. One axon (termed Axon 1) has somewhat larger boutons, containing numerous synapses and presynaptic dense bodies (putative active zones for transmitter release). This axon also has more numerous intraterminal mitochondria, and a profuse subsynaptic reticulum around or under the synaptic boutons. The second axon (Axon 2) provides somewhat smaller boutons, with fewer synapses and dense bodies per bouton, fewer intraterminal mitochondria, and less‐developed subsynaptic reticulum. Both axons contain clear synaptic vesicles, with occasional large dense vesicles. Approximately 800 synapses are provided by Axon 1 to muscles 6 and 7, and approximately 250 synapses are provided by Axon 2. In muscles 12 and 13, endings with predominantly clear synaptic vesicles, generally similar to the Type I endings of muscles 6 and 7, were found, along with another type of ending containing predominantly dense‐cored vesicles, with small clusters of clear synaptic vesicles. This second type of ending was found most frequently in muscle 12, and probably corresponds to a subset of the “Type II” endings seen in the light microscope. Type I endings are thought to generate the ‚fast’︁ and ‚slow’︁ junctional potentials seen in electrophysiological recordings, whereas the physiological actions of Type II endings are presently not known. © 1993 John Wiley & Sons, Inc.
Role of a telencephalic nucleus in the delayed song learning of socially isolated zebra finches
Authors: Morrison Robert G. , Nottebohm Fernando 
Published: January 2005

AbstractMale zebra finches normally learn their song from adult models during a restricted period of juvenile development. If song models are not available then, juveniles develop an isolate song which can be modified in adulthood. In this report we investigate the features of juvenile experience that underly the timing of song learning. Juvenile males raised in soundproof chambers or in visual isolation from conspecifics developed stable isolate song. However, whereas visual isolate song notes were similar to those of colony‐reared males, soundproof chamber isolates included many phonologically abnormal notes in their songs. Despite having stable isolate songs, both groups copied new notes from tutors presented to them in adulthood (2.7 notes per bird for soundproof chamber isolates, 4.4 notes per bird for visual isolates). Old notes were often modified or eliminated. We infer that social interactions with live tutors are normally important for closing the sensitive period for song learning. Lesions of a forebrain nucleus (IMAN) had previously been shown to disrupt juvenile song learning, but not maintenance of adult song for up to 5 weeks after surgery. In this study, colony‐reared adult males given bilateral lesions of IMAN retained all their song notes for up to 4–7.5 months after lesioning. However, similar lesions blocked all song note acquisition in adulthood by both visual and soundproof chamber isolates. Other work has shown that intact hearing is necessary for the maintenance of adult zebra finch song. We infer that auditory pathways used for song maintenance and acquisition differ: IMAN is necessary for auditorily guided song acquisition—whether by juveniles or adults—but not for adult auditorily guided song maintenance. © 1993 John Wiley & Sons, Inc.
Interactions between spinal cord stimulation and activity blockade in the regulation of synaptogenesis and motoneuron survival in the chick embryo
Authors: Le Ray C. Fournier , Prevette D. , Oppenheim R. W. , Fontaine‐Perus J. 
Published: January 2005

AbstractThe present study investigated the effects of spinal cord stimulation, neuromuscular blockade, or a combination of the two on neuromuscular development both during and after the period of naturally occurring motoneuron death in the chick embryo. Electrical stimulation of the spinal cord was without effect on motoneuron survival, synaptogenesis, or muscle properties. By contrast, activity blockade rescued motoneurons from cell death and altered synaptogenesis. A combination of spinal cord stimulation and activity blockade resulted in a marked increase in motoneuron death, and also altered synaptogenesis similar to that seen with activity blockade alone. Perturbation of normal nerve–muscle interactions by activity blockade may increase the vulnerability of developing motoneurons to excessive excitatory afferent input (spinal cord stimulation) resulting in excitotoxic‐induced cell death. © 1993 John Wiley & Sons, Inc.
Members of the Dlx‐and NKx2‐gene families are regionally expressed in the developing forebrain
Authors: Price Melanie 
Published: January 2005

AbstractMembers of the vertebrate Dlx‐ and NKx2‐homeobox‐containing gene families exhibit closely related, comple‐mentary areas of gene expression in the developing forebrain. The expression domains and onset of gene transcription indicate that these genes may play a role in forebrain patterning, particularly in the diencephalon. In some cases, gene expression borders coincide with mor‐phological boundaries separating functional and anatomical regions of the forebrain suggesting that the rostral region of the neural tube may indeed arise from a segmented structure. © 1993 John Wiley & Sons, Inc.