bluuebunny/crossref_metadata_2025_split huggingface dataset:
Novel effects of serotonin on neurite outgrowth in neurons cultured from embryos of Helisoma trivolvis
Authors: Goldberg Jeffrey I. , Mills Linda R. , Kater Stanley B. 
Published: January 2005

AbstractThe neurotransmitter serotonin has been shown to inhibit neurite outgrowth in specific identified neurons isolated from adult Helisoma. While in vivo experiments on Helisoma embryos have supported the hypothesis that endogenous serotonin regulates neurite outgrowth during embryonic development, direct effects of serotonin on embryonic neurons have not been measured. In the present study, cultures of dissociated embryonic neurons were used to test the direct actions of serotonin on developing embryonic neurons. Serotonin arrested neurite outgrowth in a significant percentage of elongating neurites in a dose‐dependent manner. Furthermore, analysis of neurons with stable, nonelongating neurites revealed a novel response. Serotonin caused the reinitiation of neurite outgrowth in a significant percentage of nonelongating neurites. The arrestment of outgrowth and reinitiation of outgrowth occurred in similar percentages of elongating and nonelongating neurites, respectively. Parallel experiments on cultures of dissociated adult neurons were carried out to determine whether serotonin could also induce both inhibitory and stimulatory responses in adult cells. Serotonin arrested neurite outgrowth in a similar percentage of neurites to that observed in cultures of embryonic neurons. In contrast, serotonin did not reinitiate neurite outgrowth in a significant percentage of adult neurites. These data support the hypothesis that serotonin regulates neurite outgrowth in developing embryonic neurons. Furthermore, only some of these regulatory effects appear to be conserved from embryonic to adult neurons.
Location and connectivity of abdominal motoneurons in the embryo and larva of Drosophila melanogaster
Authors: Sink Helen , Whitington Paul M. 
Published: January 2005

AbstractThe soma location and peripheral connectivity of motoneurons in abdominal segments of the embryo and larva of the fruitfly, Drosophila melanogaster are described as an initial step in determining the mechanisms by which motoneurons make connections with their target muscles in a genetically accessible organism. Embryonic motoneuron somata were retrogradely labelled by application of the fluorescent dye, DiI, to the whole peripheral nerve or to its separate anterior or posterior fascicles in segments A5–A7 of late stage 15/early stage 16 embryos. This technique reveals a stereotyped, segmentally repeated population of 34 motoneurons per hemisegment, several of which can be individually identified from their soma position. The same set of motoneurons was revealed in third instar larvae of D. melanogaster by cobalt backfilling of abdominal peripheral nerves, although the positions of some of these neurons change during larval development. The peripheral connectivity and axon morphology of several of the abdominal motoneurons was determined by intracellular injection with Lucifer Yellow in stage 16 embryos. For the motoneurons with axons in the anterior fascicle there is no clear relationship between somata groupings and the muscle targets innervated: contrary to earlier claims, these motoneurons arborize over both ventral and dorsal muscles. Individual motoneurons possess a stereotyped pattern of terminal arborization.
An autoradiographic analysis of neurogenesis in juvenile Aplysia californica
Authors: Hickmott Peter W. , Carew Thomas J. 
Published: January 2005

AbstractIn developing Aplysia californica, a dramatic proliferation of new neurons occurs throughout the central nervous system (CNS) surprisingly late in juvenile development (Cash and Carew, 1989). In the present study, we investigated the source of these new neurons. Using tritiated thymidine autoradiography, we examined two different juvenile stages: stage 11 (before the large‐scale proliferation)and stage 12 (at the peak of proliferation). Previous results implicated the body wall as a source for neurons in developing Aplysia (McAllister, Scheller, Kandel, and Axel, 1983; Jacob, 1984). Thus, we focused our attention on the body wall adjacent to a specific central ganglion, the abdominal ganglion. We found that in stage 11 there was uniform labelling of cells across the entire body wall. However, in stage 12 there was significantly more labelling in the body wall region immediately adjacent to the abdominal ganglion compared to flanking regions. Thus, at the time of neuronal proliferation, specific and highly localized regions of the body wall immediately opposite their target in the CNS show a significant increase in cell division.We also examined the distribution of labelled cells in the abdominal ganglion at survival times of 1 and 7 days after thymidine injection. In both stage 11 and stage 12, the fraction of labelled cells on the surface of the ganglion decreased over time, with a corresponding significant increase in the fraction observed on the inside. Our results support the hypothesis that specific regions of body wall are significantly up‐regulated in juvenile Aplysia development, giving rise to widespread neuronal proliferation. These neurons then migrate from the body wall to their target ganglion, and from there continue migrating into the ganglion to achieve their final position.
R15α1 and R15α2 peptides from Aplysia: Comparison of bioactivity, distribution, and function of two peptides generated by alternative splicing
Authors: Alevizos A. , Karagogeos D. , Weiss K. R. , Buck L. , Koester J. 
Published: January 2005

AbstractThe mRNA precursor encoded by the R15 gene is alternatively spliced in different neurons to form two related variants, R15‐1 and R15‐2 mRNA. One of the peptides encoded by the R15‐2 mRNA, the R15α1 peptide, is expressed in the endogenously bursting neuron R15 and mediates some of its central and peripheral synaptic actions. In this study we found that the R15α2 peptide, which is encoded by the R15‐1 mRNA, is synthesized in other neurons in the abdominal ganglion and is also bioactive. The R15α1 and R15α2 peptides were found to exert many similar actions on the cardiovascular, digestive, respiratory, and reproductive systems. However, the differences between many of the pharmacological effects of the R15α1 and R15α2 peptides indicate that alternative splicing in this system results in two functionally different peptides. Widespread immunoreactivity was found for an antibody directed against the R15α2 peptide, both in the central nervous system and the periphery. But because of the shared sequence with the R15α1 peptide, the antibody cross‐reacts with the R15α1 peptide. To distinguish immunocytochemically between the two peptides, we also raised a second antibody that recognizes only the R15α1 peptide. This antibody labeled the cell body of only one neuron in the central nervous system, R15, although widespread immunoreactivity was found in axons and varicosities in the periphery.
A positive correlation between permissiveness of mesoderm to neural crest migration and early DRG growth
Authors: Gvirtzman Gilat , Goldstein Ronald S. , Kalcheim Chaya 
Published: January 2005

AbstractThe microenvironment created by grafting rostral somitic halves in place of normal somites leads to the formation of nonsegmented peripheral ganglia (Kalcheim and Teillet, 1989; Goldstein and Kalcheim, 1991) and is mitogenic for neural crest (NC) cells that become dorsal root ganglia (DRG) (Goldstein et al., 1990). We have now extended these studies by using three surgical manipulations to determine how additional mesodermal tissues affected DRG growth in chick embryos. The following experimental manipulations were performed: (1) unilateral deletion of epithelial somites, similar deletions followed by replacing the somites with (2) a three‐dimensional collagen matrix, or (3) fragments of quail lateral plate mesoderm. When somites were absent or replaced by collagen matrix, ganglia were unsegmented, and their volumes were decreased by 21% and 12%, respectively, compared to contralateral intact DRG. In contrast, when lateral plate mesoderm was transplanted in place of somitic mesoderm, NC cells migrated into the grafted mesoderm and formed unsegmented DRG whose volumes were increased by 62.6% compared to the contralateral ganglia. These results suggest that although DRG precursors do not require sclerotome to begin migration and condensation precesses, DRG size is modulated by the properties of the mesoderm. Permissiveness to migration is positively correlated with an increase in DRG volume. This volume increase observed in grafts of lateral plate mesoderm is likely to result from enhanced proliferation of neural crest progenitors, previously demonstrated for DRG cells in rostral somitic grafts.
Differential effects of serotonin depletion on sensitization and dishabituation in the leech, Hirudo medicinalis
Authors: Ehrlich Joshua S. , Boulis Nicholas M. , Karrer Tracy , Sahley Christie L. 
Published: January 2005

AbstractThe goal of these experiments was to test the hypothesis that serotonin (5‐HT) is involved in facilitation of the shortening reflex in the leech Hirudo medicinalis. For this reason, we have used the toxin 5‐hydroxytryptamine (5,7‐DHT) to deplete serotonin from the nervous systems of intact leeches and have assessed the effect on early facilitation, dishabituation, and sensitization of the touch‐elicited shortening reflex using behavioral procedures previously developed in our lab (Boulis and Sahley, 1988). We find that 5,7‐DHT lesions completely attenuate early facilitation and sensitization but only reduce dishabituation of the touch‐elicited shortening reflex. Histological analyses of the ganglia from these leeches using glyoxilic acid staining procedures revealed an absence of staining in the Retzius cell of experimental leeches. All other serotonin‐containing neurons showed glyoxilic acid staining comparable to that observed in the control leeches.
S100 is present in developing chicken neurons and schwann cell and promotes motor neuron survival in vivo
Authors: Bhattacharyya Anita , Oppenheim Ronald W. , Prevette David , Moore Blake W. , Brackenbury Robert , Ratner Nancy 
Published: January 2005

AbstractWe used polyclonal antisera recognizing S100, a small acidic protein highly enriched in nervous tissue, to stain sections of embryonic chicken lumbosacral spinal cord and hindlimb. S100 immunoreactivity was detected in developing sensory neurons of the dorsal root ganglia (DRG) and motor neurons of the ventral spinal cord as early as embryonic day (E) 5, and staining persisted through hatching. In contrast, expression of S100 first became apparent in Schwann cells at E13, just before myelination, and was not detected in developing skin or muscle. Since S100β was present in motor and sensory neurons and is known to promote neuronal survival and neurite extension in vitro (Winningham‐Major, Staecker, Barger, Coats, and Van Eldik, 1989), we tested the ability of S100 to promote neuron survival in an in ovo survival assay. Addition of S100 to chick embryos in ovo during the period of naturally occurring motor neuron cell death resulted in a significant increase in motor neuron survival, but had no effect on the in vivo survival of sensory neurons in the DRG. The findings that S100 is present in spinal motor neurons and that the addition of S100 enhances the survival of these cells in vivo are consistent with the possibility that S100 may act as a naturally occurring neuron survival factor during development. © 1992 John Wiley & Sons, Inc.
Trying to understand axonal regeneration in the CNS of fish
Authors: Stuermer Claudia A. O. , Bastmeyer Martin , Bähr Matthias , Strobel Gabriele , Paschke Katja 
Published: January 2005

AbstractIn contrast to the situation in mammals and birds, neurons in the central nervous system (CNS) of fish—such as the retinal ganglion cells—are capable of regenerating their axons and restoring vision. Special properties of the glial cells and the neurons of the fish visual pathway appear to contribute to the success of axonal regeneration. The fish oligodendrocytes lack the axon growth inhibiting molecules that interfere with axonal extension in mammals. Instead, fish optic nerve oligodendrocytes support—at least in vitro—axonal elongation of fish as well as that of rat retinal axons. Moreover, the fish retinal ganglion cells re‐express upon injury a set of growth associated cell surface molecules and equip the regenerating axons throughout their path and up into their target, the tectum opticum with these molecules. This may indicate that the injured fish ganglion cells reactivate the cellular machinery necessary for axonal regrowth and pathfinding. Furthermore, the target itself provides positional marker molecules even in adult fish. These marker molecules are required to guide the regenerating axons back to their retinotopic home territory within the tectum. © 1992 John Wiley & Sons, Inc.
Specificity of a target cell‐derived stop signal for afferent axonal growth
Authors: Baird Douglas H. , Baptista Carlos A. , Wang Li‐Chong , Mason Carol A. 
Published: January 2005

AbstractWith a novel model culture system in which afferents are co‐cultured with purified populations of target neurons, we have demonstrated that a target cell within the central nervous system (CNS), the cerebellar granule neuron, poses a „stop‐growing signal”︁ for its appropriate afferents, the mossy fibers. To ask whether this stop signal is afferent specific, we co‐cultured granule neurons with an other cerebellar afferent system, the climbing fibers from the inferior olivary nuclei, which normally contact Purkinje neurons, and with retinal ganglion cell afferents, which never enter the cerebellum. Granule neurons do not pose a stop signal to either of these afferents. In contrast to pontine mossy afferents that grow well on laminin and showed reduced outgrowth on granule neurons, both olivary and retinal fibers displayed similar growth on laminin alone or on granule neurons. In addition, each afferent showed different degrees of fasciculation and growth cone morphology on laminin. Thus, the growth arrest signal sent by granule neurons is specifically recognized by their appropriate afferents. Moreover, these three types of afferents exhibit varying growth patterns on the same noncellular and cellular substrates, implicating distinct molecular characteristics of growth regulation for different classes of neurons that would contribute to specificity of synapse formation. © 1992 John Wiley & Sons, Inc.
Dopamine and nicotine, but not serotonin, modulate the crustacean ventilatory pattern generator
Authors: Rajashekhar K. P. , Wilkens J. L. 
Published: January 2005

AbstractDopamine (DA) causes a dose‐dependent increase in the frequency of motor neuron bursts [virtual ventilation (fR)] produced by deafferented crab ventilatory pattern generators (CPGv). Domperidone, a D2‐specific DA antagonist, by itself reversibly depresses fRand also blocks the stimulatory effects of DA. Serotonin (5HT) has no direct effects on this CPGv. Nicotine also causes dramatic dose‐dependent increases in the frequency of motor bursts from the CPGv. The action is triphasic, beginning with an initial reversal of burst pattern typical of reversed‐mode ventilation, followed by a 2‐ to 3‐min period of depression and then a long period of elevated burst rate. Acetylcholine chloride (ACh) alone is ineffective, but in the presence of eserine is moderately stimulatory. The inhibitory effects of nicotine are only partially blocked by curare. The excitatory action of nicotine is blocked by prior perfusion of domperidone, but not by SKF‐83566.HCl, a D1‐specific DA antagonist. SKF‐83566 had no effects on the ongoing pattern of firing. These observations support the hypothesis that dopaminergic pathways are involved in the maintenance of the CPGvrhythm and that the acceleratory effects of nicotine may involve release of DA either directly or via stimulation of atypical ACh receptors at intraganglionic sites. © 1992 John Wiley & Sons, Inc.
Transient expression of adheron molecules during chick retinal development
Authors: Tsui Ho‐Ching Tiffany , Pope Whitney B. , Kim Chong S. , Klein William L. 
Published: January 2005

AbstractNeuritogenesis and synapse formation are transient phenomena mediated in part by filopodial attachments (Tsui, Lankford, and Klein, Proc. Natl. Acad. Sci. 82:8256–8260 1985). These attachments can be labeled by antisera against adherons, adhesive microparticles isolated from cell culture media (Tsui, Schubert, and Klein, J. Cell Biol. 106:2095–2108 1988). Here, two monoclonal antibodies raised against adherons have been found to recognize transiently expressed membrane antigens of developing avian retina. Early in development, monoclonal antibody (mAb) AD1 stained antigens that spanned the entire tissue. With time, immunoreactivity became restricted to optic fiber, ganglion cell, and inner plexiform layers. Immunoblots of embryonic day (E) 13 retina showed a broad band at 66–72 kD for particulate fractions and a fine band at 70 kD for suluble fractions. The particulate forms disappeared as retinas matured, but the soluble form did not. mAb AD2 initially labeled retina antigens of optic fiber, ganglion cell, and inner plexiform layers (IPL). Labeling in the plexiform layer showed discrete lamina. Immunoreactivity first appeared at E9, peaked at E15, and then disappeared shortly after hatching. In isolated cells, AD2 labeled small cell surface aggregates. Cytoarchitectural studies, using whole mount transmission electron microscopy, showed AD2 antigen in cell surface microfilaments, including some that joined filopodia together. The adheron antigens recognized by mAbs AD1 and AD2 thus were (1) topographically restricted; (2) associated with cell surfaces; and (3) developmentally down‐regulated. This pattern suggests a role in developmentally transient cell surface phenomena, such as neurite extension or junction biogenesis. © 1992 John Wiley & Sons, Inc.
Association of neuronal pp60c‐src with growth cone glycoproteins of rat brain
Authors: Hanissian Silva H. , Chatila Talal , Sahyoun Naji E. 
Published: January 2005

AbstractTyrosine phosphorylation and protein tyrosine kinase (PTK) activity in the growth cone membrane‐associated glycoprotein (GCGP) fraction of 1‐day‐old rat brain were examined. Using immunoblotting and immunoprecipitation techniques, pp60c‐src was identified as one of the major PTKs associated with GCGPs. Furthermore, only GCGP‐associated src that was also tyrosine phosphorylated was active. Immunoprecipitation experiments using various src antibodies revealed that pp60c‐src contributed partially to the PTK activity detected in GCGPs, and that it is associated with several proteins of Mr 140 K, 120 K, 85 K and 50 K. This association of src protein with GCGPs was specific, and another src family member p59fyn, which is also abundant in the brain, did not exhibit such an association. In addition to pp60c‐src, the GCGP fraction contained several major phosphotryosine‐containing proteins of Mr 140 K, and a 97/90 K doublet that corresponded to the beta subunits of IGF‐I/ insulin receptors. These studies show that pp60c‐src associated with GCGPs is an active PTK that could be involved in neuronal growth and development, transmembrane signalling, and in recognition and/or adhesive events. © 1992 John Wiley & Sons, Inc.
Development and organization of the Drosophila olfactory system: An analysis using enhancer traps
Authors: Riesgo‐Escovar Juan , Woodard Craig , Gaines Peter , Carlson John 
Published: January 2005

AbstractDrosophila uses different olfactory organs at different developmental stages. The larval and adult olfactory organs are morphologically dissimilar and have different developmental origins: the antenno‐maxillary complex (AMC), which houses the larval olfactory organ, is histolyzed during metamorphosis; the third antennal segment—the principal adult olfactory organ—derives from an imaginal disc. A screen for genes expressed in both larval and adult olfactory organs, but in relatively few other tissues, has been carried out. Seven enhancer trap lines showing reporter gene expression in both the larval AMC and in certain subsets of the adult antenna are described. The antennal staining pattern of one line shows a striking change over the first few days of adult life, with a time course comparable to that of the development of sexual maturity. A pronounced sexual dimorphism in antennal staining pattern is seen in another line. Some staining patterns resemble the patterns of certain classes of antennal sensilla; others show expression restricted to only a small number of cells. Some lines also show expression associated with other chemosensory organs at either the larval or adult stage, including the maxillary palps, labellum, and anterior wing margin. One line, which also shows staining in the male reproductive tract, is male sterile. The significance of these results is considered in terms of (1) the molecular organization of the olfactory system; (2) the recruitment of olfactory genes for use in two developmental contexts; (3) the sharing of genes among different sensory modalities; (4) the role of olfaction in sexual behavior; and (5) posteclosional changes in the olfactory system. © 1992 John Wiley & Sons, Inc.
Depolarization‐induced changes in neurite elongation and intracellular Ca2+ in isolated Helisoma neurons
Authors: Cohan Christopher S. 
Published: January 2005

AbstractThis study focuses on the effects of K+ depolarization on neurite elongation of identified Helisoma neurons isolated into culture. Application of K+ to the external medium caused a dose‐dependent suppression of neurite elongation. Lower concentrations of K+ were associated with a slowing in the rate of neurite elongation, whereas higher concentrations produced neurite retraction. Surprisingly, the effects of K+ depolarization were transient, and neurite elongation rates recovered towards control levels within 90 min even though the neurons remained in high‐K+ solution. Identified neurons differed in the magnitude of their response to K+ depolarization; neurite elongation of buccal neuron B4 was inhibited at 5 mM K+, but elongation in B5 and B19 was not affected until concentrations of 25 mM. Electrophysiologically, K+ application evoked a brief period (5–10 s) of action potential activity that was followed by a steady‐state membrane depolarization lasting 2 h or more. The changes in neurite elongation induced by K+ depolarization occurred in isolated growth cones severed from their neurites and were blocked by application of calcium antagonists. Intracellular free Ca2+ levels in growth cones of B4 and B19 increased and then decreased during the 90‐min depolarization, corresponding to the changes in elongation. B4 and B19 showed differences in the magnitude, time course, and spatial distribution of the Ca2+ change during depolarization, reflecting their different sensitivities to depolarization.