bluuebunny/crossref_metadata_2025 huggingface dataset:
Developmental maps of acetylcholinesterase and G4‐antigen of the early chicken brain: Long‐distance tracts originate from AChE‐producing cell bodies
Authors: Weikert Thomas , Rathjen Fritz G. , Layer Paul G.
Published: January 2005

After approaching the outer surface of the neuroepithelium, postmitotic cell bodies abruptly start to synthesize acetylcholinesterase (AChE). Their easy histochemical detection allows us to trace sensitively spationtemporal patterns of differentiation processes of the chicken nervous system. To investigate the relationship between postmitotic AChE production and the first formation of neurites, AChE histochemistry is combined here with immunohistochemistry using the neurite‐specific G4‐antibody. Spatial computer reconstructions from double‐stained serial sections of whole brains of H.H. stages 10–20 demonstrate that G4‐neurite expression spatiotemporally follows the expression of AChE in its complex polycentric pattern closely, the details of which have been described earlier. By comparing both differentiative steps at the single cell level reveals that a great majority (if not all) of the G4‐positive neurites originate from AChE‐positive cell bodies. Based on both the computer reconstructions as well as single cell analysis, including [3H]‐thymidine pulse‐experiments followed by autoradiography, we conclude, that AChE expression precedes formation of G4‐neurites by about 15 h. In addition, the reconstructions provide the first detailed maps of G4‐fiber tract formation and shows that G4‐neurites form fascicles, most of which travel over long distances to targets within or without the central nervous system (CNS). This is the first demonstration for the entire young chicken brain which verifies that AChE‐expressing cells, generally, are those that will establish efferents to distant targets.
Metamorphosis alters the response to spinal cord transection in Xenopus laevis frogs
Authors: Beattie Michael S. , Bresnahan Jacqueline C. , Lopate Glenn
Published: January 2005

A series of studies has examined the response of the spinal cord to lesions made at various stages prior to and after metamorphic climax in the clawed frog Xenopus laevis. Complete transections made between Nieuwkoop and Faber (1956) stages 50 and 62 were followed by gradual recovery of righting and coordinated swimming as animals metamorphosed into juveniles (stage 66). Examination of descending axonal projections using horseradish peroxidase (HRP) showed fibers crossing the lesion site and distributing to the caudal lumbar spinal cord. These fibers could be traced from more rostral spinal segments as well as from brainstem injections of HRP. No evidence for rostrally projecting fibers crossing the lesion was obtained. Juvenile frogs of varying ages failed to demonstrate recovery of coordinated swimming or reconstitution of spinal descending pathways. In an additional series of animals, spinal transections were made within 1 or 2 days of tail resorption to assess whether regenerative capacities extended at all into post‐metamorphic stages. No evidence for regeneration was found. Studies of metamorphosing frogs after spinal transections showed that fibers crossed the lesion within 5–12 days of transection, well prior to the end of metamorphic climax; however, in some cases in which metamorphosis seemed arrested, little regeneration was observed. Immunocytochemical studies showed that fibers containing serotonin (5‐HT) were included in the population of axons that rapidly crossed the lesion after transection at metamorphic stages. These results are compared to those for lesions of the dorsal columns and other systems in developing and juvenile Xenopus. It is suggested that both metamorphosis‐related hormonal changes, and axon substrate pathways, may affect the regenerative response in the Xenopus central nervous system (CNS).
Directed early axonal outgrowth from retinal transplants into host rat brains
Authors: Hankin Mark H. , Lund Raymond D.
Published: January 2005

Axons from retinae transplanted to the brain stem of neonatal rats exhibit two patterns of outgrowth that can be experimentally uncoupled from each other depending upon the location of the graft. Retinae placed close to the surface of the rostral brain stem (as much as 5 mm from the tectum) emit axons that project toward the superior colliculus along the subpial margin of the rostral brain stem. In contrast, axons from grafts embedded deep within the midbrain parenchyma project through the neuropil directly to the overlying superior colliculus, as long as the retina is within about 1 mm of the tectal surface. The present study shows that, as long as the retina is located outside the superior colliculus, and regardless of whether the axons derive from grafts in subpial or intraparenchymal locations, the earliest projections are oriented towards the superior colliculus. We have also found, however, that axons from retinae transplanted directly onto the superior colliculus can form projections that extend along the subpial margin away form the tectum. There are several major conclusions that may be drawn from these observations. First, the final tectopetal, transplant‐derived projection does not result from the reorganization of an initially random outgrowth but is directed from the start toward an appropriate region of termination. Second, it appears that the interaction of retinal axons with a primary target alters the ability of the growth cone to respond to directional cues along the optic tract. Thus, although adding support to the proposal that optic axons attain the superior colliculus through an interaction involving substrates distributed along the optic tract and diffusible factors originating in the target region, it is increasingly clear that such interactions are likely to be complex and hierachical.
Developmental regulation of type II calcium/calmodulin‐dependent kinase isoforms in rat cerebellum
Authors: Vallano Mary Lou
Published: January 2005

Two distinct isoforms of a Type II calcium/calmodulindependent protein kinase were separated from highspeed supernates (cytosol) of rat neonatal [postnatal day 10 (P10)] and adult [postnatal day 40 (P40)] cerebellum using cation‐exchange chromatography. The isoenzymes contained variable amounts of three subunits of apparent Mr's of 50 kDa (α), 58 kDa (β'), and 60 kDa (β). The specific activity of calmodulin‐dependent kinase (CaM kinase II) in crude homogenates increased sixfold between P10 and P40 using exogenous MAP 2 as substrate. Cytosol from cerebellum at P40 contained a predominant isoform (∼40% of total cytosolic activity) with a 1:5 molar ratio of α:β',β subunits that eluted with 150 mM NaCl (designated 150) and a less abundant isoform (∼20% of total cytosolic activity) containing a 1:8 molar ratio of α:β',β subunits that eluted with 350 mM NaCl (designated 350). In neonatal cerebellum at P10, the relative abundance of the two isoforms was reversed such that ∼50% of the cytosolic calmodulin‐dependent kinase activity was recovered in the 350 isoform, whereas only 20% of the total cytosolic kinase activity was recovered in the 150 isoform. Previous studies indicate that cerebellar granule cells may contain an all β',β isoform of CaM kinase II that lacks α subunit. Thus, to assess the cell‐specific localization of kinase isoforms within cerebellum, cytosol prepared from primary cultures of rat cerebellar granule cells was applied to cation‐exchange chromatography and analyzed for calmodulin‐dependent kinase activity. The cells contained both isoforms of the kinase that were present in fresh tissue suggesting that granule cell‐enriched cultures express all three kinase subunits. The data demonstrate that rat cerebellum contains unique mixtures of CaM kinase II isoenzymes and that their expression is developmentally regulated.
Odorant‐binding‐protein subfamilies associate with distinct classes of olfactory receptor neurons in insects
Authors: Vogt Richard G. , Prestwich Glenn D. , Lerner Michael R.
Published: January 2005

The olfactory receptors of terrestrial animals exist in an aqueous environment, yet detect odorants that are primarily hydrophobic. The aqueous solubility of hydrophobic odorants is thought to be greatly enhanced via odorant binding proteins (OBP) which exist in the extracellular fluid surrounding the odorant receptors. We have isolated and partially sequenced 14 candidate OBPs from six insect (moth) species. All 14 represent a single homologous family based on conserved sequence domains. The 14 proteins can be divided into three subfamilies based on differences in tissue specific expression and similarities in amino acid sequences. All 14 proteins are specifically expressed in antennal olfactory tissue. Subfamily I represents previously described pheromone binding proteins (PBP), which are malespecific, associate with pheromone‐sensitive neurons, and are highly variable in their sequences when compared among species. Subfamilies II and III are expressed in both male and female antennae, appear to associate with general‐odorant‐sensitive neurons, and are highly conserved when compared among species. The properties of the subfamily II and III proteins suggest these are general‐odorant binding proteins (GOBP). The properties of the respective insect OBP subfamilies suggest that they have different odorant binding specificities. The association of different insect OBP subfamilies with distinct classes of olfactory neurons having different odorant specificities suggests that OBPs can act as selective signal filters, peripheral to the actual receptor proteins.
Phosphorylation of membrane‐associated proteins by phorbol esters in isolated bag cell neurons of Aplysia
Authors: Azhderian Edward M. , Kaczmarek Leonard K.
Published: January 2005

Following brief synaptic stimulation, the bag cell neurons in the abdominal ganglion of Aplysia undergo a series of changes in electrophysiological and secretory properties that triggers egg laying behavior. Activation of protein kinase C appears to play an important role in these changes and, in particular, causes the unmasking of a new species of voltage‐dependent calcium channel. We have now used isolated bag cell neurons maintained in cell culture to study changes in protein phosphorylation that are induced by exposure to an activator of protein kinase C. Primary cultures of bag cell neurons were labeled with 32P orthophosphate and then incubated with either tetradecanoyl phorbol 13‐acetate (TPA), a potent activator of protein kinase C, or with an inactive phorbol ester. When protein extracts were separated with 2D electrophoresis approximately 100 phosphoproteins could be distinguished. Only four of these proteins, with molecular weights of 20, 32, 200, and 250 kD, underwent a reproducible increase in the extent of phosphorylation of at least twofold in response to TPA. TPA‐induced changes in phosphate incorporation were blocked by pretreatment with the protein kinase C inhibitor H7. One of the TPA‐regulated phosphoproteins was localized in a plasma membrane‐containing fraction and was sensitive to trypsin treatment of intact cells, suggesting that it is a membrane protein with sites exposed to the extracellular medium. Two of the other TPA‐regulated phosphoproteins may be associated with the inner face of the plasma membrane. Our results indicate that only a small number of proteins undergo a major change in phosphorylation state following the activation of protein kinase C in isolated bag cell neurons. One or more of these proteins may contribute to the unmasking of the calcium channels.
Connectivity of identified central synapses in the cricket is normal following regeneration and blockade of presynaptic activity
Authors: Chiba Akira , Murphey R. K.
Published: January 2005

Cercal sensory neurons in the cricket innervate interneurons in the central nervous system (CNS) and provide a model system for studying the formation of central synapses. When axons of the sensory neurons were transected during larval development, the cell bodies and the soma‐bearing portion of axons, which are located within the cercus, survived but lost their excitability for 9–10 days. During this period, the sensory neurons grew new axons and reinnervated the terminal abdominal ganglion. Physiological recordings showed that sensory neurons of known identity reestablished monosynaptic contacts with their normal postsynaptic interneuron. Moreover, each synapse exhibited a characterstic strength indistinguishable from the intact synapse in an unoperated cricket. Since this selective connectivity was apparent immediately after the excitability of the axotomized sensory neurons was restored, action potentials in the sensory neurons appear to be unnecessary for normal synaptic regeneration to occur. Consistent with this, the reinnervation process was unaffected even when action potentials in the sensory neurons were blocked by tetrodotoxin (TTX) immediately following axotomy until just before testing. During the normal course of development, the characteristic strength of individual synapses changes systematically, resulting in the developmental rearrangement of these synapses (Chiba et al., 1988). This synaptic rearrangement was also unaffected when action potentials in the sensory neurons were blocked by TTX for the last 30% of larval development. Therefore, in the cricket cercal sensory system, both regeneration of the central synapses following axotomy of the presynaptic sensory neurons and the normal rearrangement of connectivity during larval development appear not to require axonal action potentials.
Regeneration of the projection and synaptic connections of tympanic receptor fibers of Locusta migratoria (orthoptera) after axotomy
Authors: Lakes Reinhard , Kalmring Klaus
Published: January 2005

The tergite nerve N6 of the first abdominal segment of the locust Locusta migratoria contains receptor fibers, from the tympanic organ, and hair sensilla as well as motoric axons. The nerve was axotomized in nymphal instars or adults, and the regeneration of nerve fibers was studied. The sensory fibers regrow and regenerate their projection pattern within the central nervous system. They recognize their specific neuropile areas even after entering the ganglion through different pathways. The receptor fibers of the tympanic organ reestablish synaptic connections to auditory interneurons, even though the physiological characteristics of the interneurons are not fully restored. This regenerative capability contrasts with the lack of regeneration of peripheral structures in locusts, but supports the described plasticity in the auditory system of monaural locusts (Lakes, Kalmring, and Engelhard, 1990). The motor fibers do not regenerate nerves innervating muscles of the body wall.
Down‐regulation of quantal size at frog neuromuscular junctions: Possible roles for elevated intracellular calcium and for protein kinase C
Authors: Van der Kloot William
Published: January 2005

Previous work showed that quantal size can be at least doubled at the frog neuromuscular junction by pretreatment with hormones or hypertonic solutions, primarily by the release of more acetylcholine (ACh) per quantum. Once increased, quantal size slowly declined over hours. Quantal size was measured from miniature endplate potentials (MEPPs) or currents (MEPCs). In the present experiments, preparations in which quantal size had been increased were exposed to 17–25 mM [K+], quantal size decreased within minutes. Release of comparable numbers of quanta by nerve stimulation did not decrease size. K+‐solutions did not decrease size if Ca2+ was omitted or replaced with Sr2+. The phosphokinase C (PKC) activators phorbol 12,13‐diacetate (PDA) and 1‐oleoyl‐2‐acetyl‐rac‐glycerol (OAG) also decreased quantal size within minutes when applied in a hypertonic solution that increased the rate of spontaneous release. Phorbol 12,13‐dideconate, which does not activate PKC, did not decrease quantal size. The size decrease triggered by K+‐solutions or PKC activators was blocked by 100 μM 1‐(5‐isoquinolinyl‐sulfonyl)‐2‐methyl‐piperazine (H7), a protein kinase inhibitor. Apparently, in creasing [K+]elevated intracellular [Ca2+], which activates PKC, and which leads to the down‐regulation of quantal size. During the period in which size is decreasing, there appears to be large and normal subpopulations of MEPP sizes, with normal gradually replacing large. This suggests that large quanta are formed by adding additional ACh to preformed quanta shortly before they are available for release.
Spectrum of in vitro differentiation of quail trunk neural crest cells isolated by cell sorting using the HNK‐1 antibody and analysis of the adrenergic development of HNK‐1+ sorted subpopulations
Authors: Maxwell Gerald D. , Forbes M. Elizabeth
Published: January 2005

Previous work has demonstrated that catecholamine‐containing cells differentiate preferentially from populations of quail trunk neural crest cells isolated by cell sorting using the HNK‐1 antibody (Maxwell, Forbes, and Christie, 1988). In the present work, we examine several additional features of the differentiation of these sorted cell populations. As one part of this study, the development of subpopulations of the HNK‐1+‐sorted neural crest cells has been investigated. Twice as many catecholamine‐positive and total cells developed from the brightest third of the HNK‐1+ cells compared to the remaining HNK‐1+ cells, but the proportion of catecholamine‐containing cells was similar in both populations. When either of these HNK‐1+ subpopulations were grown together with HNK‐1− cells, no reduction in the number of adrenergic cells was observed. These results indicate that subpopulations of HNK‐1+ cells are qualitatively similar and that their adrenergic development is not affected by HNK‐1− cells. In the second part of this study, we investigate the specificity of differentiation of HNK‐1+‐ and HNK‐1−‐sorted cells by examining several additional phenotypic markers of development. We found that tyrosine hydroxylase and somatostatin immunoreactive cells developed from the HNK‐1+‐sorted population, while few, if any, cells bearing these phenotypic markers appeared in the HNK‐1−‐sorted population. In marked contrast, substantial numbers of cells immunoreactive for A2B5, E/C8, and NF‐160 differentiated from both the HNK‐1+‐ and the HNK‐1−‐sorted cell populations. The A2B5, E/C8, and NF‐160 immunoreactive cells exhibited a variety of morphologies ranging from nonneuronal to neuronal in both sorted populations. Taken together, these results indicate that the presence of the HNK‐1 antigen(s) on the trunk neural crest cell surface at 2 days in vitro is rather tightly correlated with the differentiation of adrenergic and some peptidergic cells, but much less so with other classes of neural cells including A2B5, E/C8, and NF‐160 immunoreactive cells. Thus, these findings support the view that cell surface differences are correlated with and may contribute to the generation of the phenotypic diversity of neural crest cell derivatives.
A specific 70K protein found in epileptic rat cortex: Induction of bursting activity and negative resistance by its intracellular application in Euhadra neurons
Authors: Onozuka Minoru , Imai Shizuko , Furuichi Hiroyasu , Ozono Satoru
Published: January 2005

The effect of 70‐kD protein (P70, a specific protein found in cobalt‐induced epileptogenic focus of rat cerebral cortex) on membrane properties was examined in identified neurons of the snail, Euhadra peliomphala, using the pressure injection method combined with the voltage‐clamp technique. In neurons that normally exhibited spontaneous regular firing, intracellular injection of P70 elicited bursting activity and a negative slope resistance (NSR) region in their current‐voltage (I‐V) curve in a manner corresponding to the duration of its injection. These responses were suppressed by prior injection of an antibody to P70 into the neurons, and were markedly inhibited by a reduction of extracellular Na+ ions and the anticonvulsant agent phenytoin, but not by Co2+‐substituted Ca2+‐free saline. In addition, intracellularly applied P70 potentiated both bursting activity and the NSR induced by a Na channel activator, veratridine. However, prior application of a saturating dose of this activator occluded the effect of P70. These results suggest that P70 elicits a Na+‐dependent negative resistance, which may contribute to the generation of bursting activity.
Characterization and spatial distribution of the ELAV protein during Drosophila melanogaster development
Authors: Robinow Steven , White Kalpana
Published: January 2005

The embryonic lethal abnormal visual system (elav) gene of Drosophila melanogaster is required for the development and maintenance of the nervous system. Transcripts from this locus are distributed ubiquitously throughout the nervous system at all developmental stages. A product of this gene, the ELAV protein, has homology to known RNA binding proteins. The localization of the ELAV protein was studied in all developmental stages using antibodies that were generated against a hybrid protein made in Escherichia coli. In general, these data are consistent with previous results and demonstrate that (1) the ELAV protein is detected in the developing embryonic nervous system at a time coincident with the birth of the first neurons, (2) the ELAV protein is first detected in the majority of neurons of the central and peripheral nervous systems of embryos, larvae, pupae, and adults, (3) the ELAV protein appears to be localized to the nucleus, and (4) the ELAV protein is not detected in neuroblasts or identifiable glia. These data also provide new information concerning elav expression and show that (1) ELAV is not expressed in the ganglion mother cells (GMCs), (2) while the ELAV protein is localized to the nucleus, it is not uniformly distributed throughout this structure, and (3) other Drosophila species do express an ELAV‐like antigen. We propose that the elav gene provides a neuronal‐housekeeping function that is required for the successful posttranscriptional processing of transcripts from a set of genes the function of which is required for proper neuronal development and maintenance.
Expression of a novel nuclear protein is correlated with neuronal differentiation in vivo
Authors: Paden Charles M. , Cranston Harwood , Hapner Sharon J.
Published: January 2005

We report the production of a monoclonal antibody (MAb 526) that recognizes a novel, developmentally regulated nuclear protein expressed in neurons throughout the rat nervous system. Analysis of whole brain and cell nuclear extracts by SDS‐PAGE and immunoblotting determined that MAb 526 recognizes a single nuclear protein (np) of apparent molecular weight 42 kD, designated np526, as well as a slightly larger (ca. 44 kD) cytoplasmic protein. Light microscopic immunocytochemistry showed np526 to be present in neurons of all types throughout the central and peripheral nervous systems. Nuclei of both fibrous and protoplasmic astrocytes were also immunoreactive, but oligodendrocyte nuclei were negative. Positive, but highly variable immunocytochemical staining of nonneural cell nuclei in a variety of other tissues was also observed. Electron microscopic (EM) immunocytochemistry using pre‐embedding peroxidase methods revealed that np526 is associated with euchromatin or with the edges of condensed chromatin bundles in neurons, indicating that it is likely to be a chromosomal protein. Most interestingly, the expression of np526 was found to be developmentally regulated in brain. Immunocytochemical analysis of the developing cerebral cortex from embryonic day (E) 16 to postnatal day (P) 4 and cerebellum from P4 to P18 revealed that np526 first appears in central neurons following the cessation of mitosis and that the intensity of nuclear staining increases during subsequent neuronal maturation. To our knowledge, np526 is the first presumptive chromosomal protein whose expression has been precisely correlated with the early postmitotic differentiation of mammalian neurons.
Cholinergic differentiation in neurogenic basal forebrain cultures
Authors: Martinic Marjana , Lambert Mary P. , Hua Sherwin , Klein William L.
Published: January 2005

To study early events in the central nervous system (CNS) cholinergic development, cells from rat basal fore brain tissue were placed in culture at an age when neurogenesis in vivo is still active [embryonic day (E) 15]. The rapid mortality of these cells in defined medium, with 50% mortality after 5–10 h, was blocked completely by soluble proteins from the olfactory bulb (a basal forebrain target), extending earlier observations (Lambert, Megerian, Garden, and Klein, 1988). Treated cultures were capable of incorporating thymidine into DNA, and most cells incorporating 3H‐thymidine (>90%) also stained positive for neurofilament, confirming neuronal proliferation in the supplemented cultures. A small percentage of 3H‐thymidine labelled cells were glial fibrillary acidic protein (GFAP) positive, but growth factors that support astroglial proliferation [epidermal growth factor (EGF), basic fibroblast growth factor (bFGF), and insulin‐like growth factor (IGF‐1)] were not sufficient for neuronal support. After 5 culture days with supplemented medium, almost 50% of the cells showed choline acetyltransferase (ChAT) immunofluorescence. The cholinergic neurons typically formed clusters separate from noncholinergic cells. These mature cultures did not develop if young cultures were treated with aphidicolin to block DNA synthesis. The data show that cultures of very young rat basal forebrain cells can be neurogenic, giving rise to abundant cholinergic neurons, and that early cell proliferation is essential for long‐term culture survival.
Structure‐activity relationship of the neurotransmitter alpha‐bag cell peptide on Aplysia LUQ neurons: Implications regarding its inactivation in the extracellular space
Authors: Owens David F. , Menon Jaishri G. , Rothman Barry S.
Published: January 2005

Alpha‐bag cell peptide [α‐BCP (Ala‐Pro‐Arg‐Leu‐Arg‐Phe‐Tyr‐Ser‐Leu)] is a neurotransmitter that mediates bag cell‐induced inhibition of left‐upper‐quadrant (LUQ) neurons L2, L3, L4, and L6 in the abdominal ganglion of Aplysia. Our recent biochemical studies have shown that α‐BCP[1–9] is cleaved into α‐BCP[1–2], [3–9], [1–5], [6–9], and [7–9] by a combination of three distinct peptidase activities located within the extracellular spaces of the CNS: A diaminopeptidase‐IV (DAP‐IV)‐like enzyme cleaves α‐BCP[1–9] at the 2–3 peptide bond; a neutral metalloendopeptidase (NEP)‐like enzyme cleaves either α‐BCP[1–9] or α‐BCP[3–9] at the 5–6 bond; an aminopeptidase M‐II (APM‐II)‐like enzyme cleaves α‐BCP[6–9] at the 6–7 bond, but cleaves neither α‐BCP[1–9], nor the other ganglionic peptidase products. To further understand the manner in which α‐BCP is inactivated after release, that is loses its electro‐physiological activity, we studied its structure‐activity relationship by recording intracellularly from LUQ neurons in isolated abdominal ganglia that were arterially perfused with peptides dissolved in artificial sea water. The effects of α‐BCP[1–9] and 15 of its fragments ([1–8], [1–7], [1–6], [1–5], [2–9], [3–9], [3–8], [6–9], [7–9], [8–9], [6–7], [6–8], [1–2], Phe, Tyr) indicated that the sequence Phe6‐Tyr7 was both necessary and sufficient to produce LUQ inhibitory activity. The combined results of our electrophysiological and biochemical studies strongly suggest that α‐BCP[1–9] is inactivated by the serial actions of the NEP‐like and APM‐II‐like peptidases; that is, the NEP‐like enzyme yields an electro‐physiologically active product, α‐BCP[6–9], that is cleaved by the APM‐II‐like enzyme to yield inactive α‐BCP[7–9]. Furthermore, because α‐BCP[6–9] is more active than α‐BCP[1–9], cleavage by the NEP‐like enzyme potentiates α‐BCP's activity. © 1992 John Wiley & Sons, Inc.
The development of ipsilateral retinal projections into the tectum in the cichlid fish Haplochromis burtoni: A dil study in fixed tissue
Authors: Fritzsch Bernd , Wilm Claudia
Published: January 2005

The normal development of the retinal projection was studied in a bony fish with Dil. Between 5.5 and 10 days postfertilization the contralateral retinal projection grows from the rostral pole of the tectum across its center. A maximum of 15 retinal fibers reaches the ipsilateral tectum. In 33‐day‐old juvenile animals, less than 15 ipsilateral fibers terminate in the entire tectum. Ipsilaterally projecting ganglion cells (maximal number = 20 cells) are scattered throughout the entire retina, and the location of ganglion cells in the retina and axonal terminations in the tectum display a large interindividual variability. This suggests that the small adult contingent of ipsilateral fibers in this bony fish develops without an initial exuberant ipsilateral retinal projection that is later pruned back. © 1992 John Wiley & Sons, Inc.
Hormone accumulation in song regions of the canary brain
Authors: Brenowitz Eliot A. , Arnold Arthur P.
Published: January 2005

[3H]Testosterone (T) was injected into male and female canaries (Serinus canarius), a species in which females are able to sing but do so more rarely and more simply than males. Autoradiographic analysis revealed that males and females have equal proportions of cells labeled by T or its metabolites in four song control nuclei: the high vocal center (HVC), the lateral portion of the magnocellular nucleus of the anterior neostriatum (IMAN), the robust nucleus of the archistriatum (RA), and the hypoglossal motor nucleus (nXII). Labeled cells were also observed in both sexes in the medial portion of MAN, and in hypothalamic nuclei. In both sexes, labeled cells in HVC, IMAN, RA, and nXII were larger than unlabeled cells. There were no sex differences in the size of either labeled or unlabeled cells in these song nuclei. The density of labeled cells per unit volume of tissue did not differ between the sexes in any song nucleus analyzed. However, because males have larger HVC and RA than females, males have a greater total number of hormone‐sensitive cells in these regions than do females. Comparison of these results with measures of hormone accumulation in zebra finches and tropical duetting wrens suggests that the complexity of song that a bird can produce is correlated with the total number of hormone‐sensitive cells in song nuclei. © 1992 John Wiley & Sons, Inc.
Olfactory physiology in the Drosophila antenna and maxillary palp: acj6 Distinguishes two classes of odorant pathways
Authors: Ayer Richard K. , Carlson John
Published: January 2005

This article provides characterization of the electrical response to odorants in the Drosophila antenna and provides physiological evidence that a second organ, the maxillary palp, also has olfactory function in Drosophila. The acj6 mutation, previously isolated by virtue of defective olfactory behavior, affects olfactory physiology in the maxillary palp as well as in the antenna. Interestingly, abnormal chemosensory jump 6 (acj6) reduces response in the maxillary palp to all odorants tested except benzaldehyde (odor of almond), as if response to benzaldehyde is mediated through a different type of odorant pathway from the other odorants. In other experiments, different parts of the antenna are shown to differ with respect to odorant sensitivity. Evidence is also provided that antennal response to odorants varies with age, and that odorants differ in their age dependence. © 1992 John Wiley & Sons, Inc.
Behavior of fish retinal growth cones encountering chick caudal tectal membranes: A time‐lapse study on growthcone collapse
Authors: Bastmeyer Martin , Stuermer Claudia A. O.
Published: January 2005

In a cross species in vitro assay, growth cones from fish temporal retina elongating on laminin lanes were observed with time‐lapse videomicroscopy as they encountered lanes and territories that carried membrane fragments from the chick caudal tectum. Caudal tectal membranes of adult fish and embryonic chick are known to possess a repellent guiding component for temporal retinal axons. The caudal membranes of chick exert a particularly strong influence on fish temporal axons. Contacts with chick caudal membranes by just a few filopodia and parts of the lamellipodia evoked a turning response away from the membrane lane of the entire growth cone. Contacts by filo‐ and lamellipodia over the entire circumference of the growth cone, however, caused invariably growth cone collapse and retraction. During growth cone turning and collapse and retraction, filopodia remained in contact with the tectal membrane fragments, suggesting strong membrane–filopodia adhesion simultaneous to growth cone repulsion by the repellent guiding component. © 1993 John Wiley & Sons, Inc.
Restriction of neurogenic ability during neural crest cell differentiation
Authors: Vogel Kristine S. , Marusich Michael F. , Weston James A.
Published: January 2005

Multipotent neural crest cells undergo developmental restrictions during embryogenesis and eventually give rise to the neurons and glia of the peripheral nervous system, melanocytes, and pheochromocytes. To understand how neuronal potential is restricted to a subpopulation of crest‐derived cells, we have utilized sensitive markers of early neuronal differentiation to assess neurogenesis in crest‐derived cell populations subjected to defined experimental conditions in vitro and in vivo. We describe environmental conditions that either (a) result in the irreversible loss of neurogenic potential over a characteristic time course or (b) maintain neurogenic potential among neural crest cells. © 1993 John Wiley & Sons, Inc.
Octopamine effects mimick state‐dependent changes in a proprioceptive feedback system
Authors: Büschges Ansgar , Kittmann Rolf , Ramirez Jan‐Marino
Published: January 2005

The modulatory actions of the biogenic amine octopamine on the femur tibia (FT) control loop in the stick insect Carausius morosus were examined. The response properties of the FT control loop were determined under open loop conditions. Mechanical stimulation of the femoral chordotonal organ (fCO) was the input and tibial movement and motoneuronal activity were measured as the output of the system. Following octopamine injection into the hemolymph of intact, inactive animals, two consecutive phases occurred at the behavioral level. Octopamine caused initially an activation of the animal. During this first phase (3.5–12 min duration) the response properties of the FT control loop were similar to those found in animals that were activated by tactile stimuli under normal conditions. Afterward, animals became inactive. During this second phase (15–20 min duration), the gain of the control loop was zero and no resistance reflex in the FT joint was generated in response to fCO stimulation. However, active movements of the tibia could still be elicited. As we could show in restrained animals, where dl‐octopamine was applied topically onto the undesheated mesothoracic ganglion, the complete suppression of the resistance reflex on the motoneuronal level was dose dependent starting at concentrations of 5 ± 10−3 M octopamine. We could show that octopamine specifically suppressed the pathways involved in the resistance reflex, while feedback loop responses to fCO stimuli typical for active animals could still be elicited. Our results indicate that an increase in the octopamine concentration mimicks activation of the animal: Properties being characteristic for the control of the FT joint in the inactive animal are inhibited by octopamine, while properties of the FT control loop typical for the active animal appear to be facilitated following octopamine injection. The results clearly demonstrate that different pathways in the neuronal network underlying the FT control loop are involved in the responses of the control loop to fCO stimuli in the inactive and active behavioral states of the stick insect. © 1993 John Wiley & Sons, Inc.
Testosterone‐induced changes in adult canary brain are reversible
Authors: Brown Susan D. , Bottjer Sarah W.
Published: January 2005

Brain nuclei that control song are larger in male canaries, which sing, than in females, which sing rarely or not at all. Treatment of adult female canaries with testosterone (T) induces song production and causes song‐control nuclei to grow, approaching the volumes observed in males. For example, the higher vocal center (HVC) of adult females approximately doubles in size by 1 month following the onset of T treatment. Male HVC projects to a second telencephalic nucleus, RA (the robust nucleus of the archistriatum), which projects in turn to the vocal motor neurons. Whether HVC makes a similar connection in female canaries is not known, although HVC and RA are not functionally connected in female zebra finches, a species in which testosterone does not induce neural or behavioral changes in the adult song system. This experiment investigated whether HVC makes an efferent projection to RA in normal adult female canaries, or if T is necessary to induce the growth of this connection. In addition, we examined whether T‐induced changes in adult female canary brain are reversible. Adult female canaries received systemic T implants that were removed after 4 weeks; these birds were killed 4 weeks after T removal (Testosterone‐Removal, T‐R). Separate groups of control birds received either (a) T implants for 4 weeks which were not removed (Testosterone‐Control, T‐C) or (b) empty implants (Untreated Control, øO‐C). Crystals of the fluorescent tracer DiI were placed in the song‐control nucleus HVC in order to anterogradely label both efferent targets of HVC, RA and Area X. Projections from HVC to RA and Area X were present in all treatment groups including untreated controls, and did not appear to differ either qualitatively or quantitatively. Thus, formation of efferent connections from HVC may be prerequisite to hormone‐induced expression of song behavior in adult songbirds. The volumes of RA and Area X were measured using the distribution of anterograde label as well as their appearance in Nissl‐stained tissue. RA was larger in T‐treated control birds than in untreated controls. Experimental birds in which T was given and then removed (T‐R) had RA volumes closer in size to untreated controls (ø‐C). Because the volume of RA in T‐treated controls (T‐C) was larger than that of birds that did not receive T (ø‐C), we conclude that the volume of RA increased in both T‐C and T‐R birds but regressed upon removal of T in T‐R birds. Surprisingly, the volume of Area X did not increase in T‐treated birds. Birds in this study were maintained on short days, suggesting that T‐induced growth of Area X reported previously may have resulted from an interaction between T and another seasonal or photoperiodic factor induced by exposure to long daylengths. © 1993 John Wiley & Sons, Inc.
Synaptic loss following removal of serotoninergic fibers in newly hatched and adult chickens
Authors: Okado Nobuo , Cheng Ling , Tanatsugu Yasuyuki , Hamada Shun , Hamaguchi Kayoko
Published: January 2005

Neurotransmitters such as serotonin (5HT) may have nontransmitter, trophic‐like functions in the developing and adult nervous system. In order to examine this possibility in the avian spinal cord, we have quantified synapse numbers on spinal neurons following treatment with drugs that result in the destruction of 5HT positive axons. Either p‐chlorophenylalanine or reserpine was injected into newly hatched or adult chickens. Following treatment for 7 days the density of nonserotoninergic synapses was considerably decreased in the targets of 5HT fibers. By contrast, neither change was observed in the dendritic structures of spinal motoneurons or in the distribution of substance P and enkephalin positive fibers. These data suggest that 5HT may play an important role in the normal increase and maintenance of synapses in developing and adult animals. A lesion of 5HT neurons may not only alter neurochemistry but also alter the general synaptic structures of the brain. While 5HT containing fibers were depleted in a dose‐dependent fashion we cannot rule out the possibility that other neurotransmitter systems were depleted at higher dose of PCPA and reserpine. © 1993 John Wiley & Sons, Inc.
The history of the discovery of the nerve growth factor
Authors: Hamburger Viktor
Published: January 2005

The Nerve Growth Factor (NGF) is the progenitor of a family of growth factors which is still expanding. The history of its discovery is very colorful; it is a rare combination of scientific reasoning, intuition, fortuities, and good luck. In addition, I believe that the collaboration of three scientists with very different backgrounds contributed to the success: I had grown up in a laboratory of experimental embryology, Dr. Levi‐Montalcini came from neurology, and Dr. Stanley Cohen was from biochemistry.

The decision where to begin the history of a discovery is always arbitrary. I shall give my reasons why I begin this story with my wing bud extirpations on chick embryos and the analysis of the effects of the operation on the development of spinal nerve centers, published in 1934. Of course, I am aware of the fact that the analysis of neurogenesis had been pioneered by Dr. R. G. Harrison and his students at Yale University since the beginning of this century. It should be mentioned that their experiments had been done on amphibian embryos. My own interest in problems of neurogenesis dates back to my Ph.D. thesis in the Zoology Department of Professor H. Spemann at the University of Freiburg in (the Federal Republic of) Germany; it dealt with the influence of the nervous system on the development of limbs in frog embryos. After I had obtained some inconclusive results I did the crucial experiment of producing nerveless legs. I removed the lumbar part of the spinal cord and the spinal ganglia before the outgrowth of nerve fibers. The nerveless legs developed normally in every respect, but the muscles atrophied eventually.
Axial level‐dependent differences in size of avian dorsal root ganglia are present from gangliogenesis
Authors: Goldstein Ronald S.
Published: January 2005

Dorsal root ganglia (DRG) form from neural crest cells that colonize the rostral sclerotomes of the somites of the trunk of higher vertebrates. Differences in sensory field size and innervation density are reflected by the size of the ganglia at different axial levels. Some of the position‐dependent differences in ganglionic size derives from asymmetry in embryonic programmed cell death, when more DRG neurons die at non‐limb‐innervating levels than at the levels that innervate the limbs. I have now examined early chick embryos determine whether there is asymmetry in DRG size at the time of their condensation at stage 20 [embryonic day (E) 3], before the onset of cell death. Ganglia in brachial segments 14 and 15 are more than 80% larger on average than those in cervical segments 5 and 6 at this stage of development. This difference in volume is due to increased numbers of cells in the brachial sensory ganglia. Several other morphometric parameters of the DRG and sclerotomes were then determined. The rostro‐caudal length was found to be significantly greater for brachial ganglia. The greater length of the brachial ganglia was found to be correlated with (1) a greater length of brachial than cervical sclerotomes and (2) the occupation by brachial ganglia of a larger proportion of the rostro‐caudal extent of the sclerotome. These results demonstrate that the mature pattern of axial differences in ganglionic size are foreshadowed by a pattern set during the period of gangliogenesis, which is then further sculpted by apoptosis. This initial axial asymmetry in size preceding cell death parallels that recently shown for the development of the ventral motor column. Thus the sensory ganglia, like the somites, have distinct axial‐position‐dependent characteristics from their outset, characteristics that are not dependent on cell death resulting from competition for target‐derived survival factors as was previously thought. DRG positional identities, like their segmentation, may be imposed by the paraxial mesoderm or may alternatively be intrinsically determined as is the case for the rhombomeres of the hindbrain. © 1993 John Wiley & Sons, Inc.
Planar and vertical induction of anteroposterior pattern during the development of the amphibian central nervous system
Authors: Doniach Tabitha
Published: January 2005

In amphibians and other vertebrates, neural development is induced in the ectoderm by signals coming from the dorsal mesoderm during gastrulation. Classical embryological results indicated that these signals follow a “vertical” path, from the involuted dorsal mesoderm to the overlying ectoderm. Recent work with the frog Xenopus laevis, however, has revealed the existence of “planar” neural‐inducing signals, which pass within the continuous sheet or plane of tissue formed by the dorsal mesoderm and presumptive neurectoderm. Much of this work has made use of Keller explants, in which dorsal mesoderm and ectoderm are cultured in a planar configuration with contact along only a single edge, and vertical contact is prevented. Planar signals can induce the full anteroposterior (A‐P) extent of neural pattern, as evidenced in Keller explants by the expression of genes that mark specific positions along the A‐P axis. In this review, classical and modern molecular work on vertical and planar inductionwill be discussed. This will be followed by a discussion of various models for vertical induction and planar induction. It has been proposed that the A‐P pattern in the nervous system is derived from a parallel pattern of inducers in the dorsal mesoderm which is “imprinted” vertically onto the overlying ectoderm. Since it is now known that planar signals can also induce A‐P neural pattern, this kind of model must be reassessed. The study of planar induction of A‐P pattern in Xenopus embryos provides a simple, manipulable, two‐dimensional system in which to investigate pattern formation. © 1993 John Wiley & Sons, Inc.
Sexual differences in the numerical density of synaptic profiles of developing rat visual cortex
Authors: Muñoz‐Cueto José Antonia , Ruiz‐Marcos Antonio
Published: January 2005

Axo‐dendritic synaptic profiles were quantified along the whole depth of the visual cortex of 10‐day‐old male and female rats. In both sexes the numerical density of synaptic profiles on spine‐like structures was greater than the numerical density of synapses on dendritic shafts. Females had a significantly greater numerical density of synaptic profiles on spine‐like structures, than did males at a distance of 200–400 and 500–600 μm from the pia surface, which corresponds to layers II–III and IV of the cortex, respectively. A small percentage (2%–4%) of spine‐like structures received two presynaptic terminals. This type of double synapses was three times more abundant in females. No sex differences were found in the numerical density of synapses on dendritic shafts in any cortical layer. 1994 John Wiley & Sons, Inc.
Identification of a 70 kD protein with sequence homology to squid neurofilament protein in glial cells of the leech CNS
Authors: Lüthi Theres E. , Brodbeck Daniela L. , Jenö Paul
Published: January 2005

A monoclonal antibody G39, generated against a protein extract of leech central nervous system, labels specific cell types in adult, embryonic, and regenerating preparations. The antibody stained glial cells, microglial cells, and connective tissue cells, but nor neurons or muscle on cryosections. The staining pattern resembled that of an intracellular network. Affinity purification of the antigen revealed a 70 kD protein. Peptide sequencing showed significant homology of a stretch of 15 amino acids to squid neural filament protein. The same mAb G39 delineated glial cells as they formed during development of the CNS and showed that the giant neuropil glial cells appear before those in the packets. The antigen recognized by mAb G39 represents a nonneuronal intermediate filament of the leech Hirudo medicinalis found in various cell‐types such as glia, microglia, and some cells of the connective tissue. 1994 John Wiley & Sons, Inc.