bluuebunny/crossref_metadata_2025 huggingface dataset:
The vocal motor neurons of Xenopus laevis: Development of sex differences in axon number
Authors: Kelley Darcy B. , Dennison Jane
Published: January 2005

Sex differences in the number of muscle fibers in the larynx of clawed frogs (Xenopus laevis) develop after metamorphosis. In order to examine possible contributions of neural innervation to this process, we prepared sections of the laryngeal nerve from tadpole stage 56, when the sexes can first be distinguished, through adulthood, and counted axons on electron micrographs. The adult number of axons is achieved by a sexually differentiated pattern of axonal addition and loss. Axon numbers are high at tadpole stage 56 and equal for males and females; thereafter, males have more axons. Sex differences are most pronounced at tadpole stage 62 because between stages 59 and 62 the number of laryngeal axons in males increases by an average of 119 per nerve. Ultra‐structural evidence is congruent with the hypothesis that new axons are added to the laryngeal nerve between tadpole stages 56 and 62. The loss of axons from the laryngeal nerve is greater for females than for males. Between tadpole stages 56 and adulthood, overall axon number decreases by 47% in males and by 64% in females. Signs of axonal degeneration are present in both sexes before metamorphosis but are rare at juvenile or adult stages. The numbers of axons in juvenile frogs do not differ from those in adults and continue to be greater in males than in females. In contrast to the amount of axon addition and loss, the timing of axon loss and the percentage of myelinated axons is the same for males and females throughout development. Thus sex differences in the innervation of laryngeal muscle originate before metamorphosis and could contribute to the marked sex differences in muscle fiber addition that occur thereafter.
Phentolamine selectively affects the fast sodium component of sensory adaptation in an insect mechanoreceptor
Authors: Ramirez J.‐M. , French A. S.
Published: January 2005

Phentolamine and related compounds have several different actions on nervous tissues in vertebrates and invertebrates, including a local anesthetic effect. However, recent work suggests that phentolamine can interfere with sensory transduction in insect mechanoreceptors at significantly lower concetrations than are required for conduction block. We tested the actions of phentolamine on sensory transduction and encoding in an insect mechanoreceptor, the cockroach tactile spine neuron and found that 500 μM phentolamine increased the action potential threshold by 50%. The passive membrane properties of the neuron were not affected, but one component of dynamic threshold change was strongly and selectively reduced. This component has previously been attributed to slowly inactivating sodium channels in the action potential initiating region, suggesting that these channels are the most phentolamine‐sensitive sites.
Differential effects of denervation on acetylcholinesterase activity in parasympathetic and sympathetic ganglia of the frog,Rana pipiens
Authors: Streichert Laura C. , Sargent Peter B.
Published: January 2005

The transsynaptic regulation of acetylcholinesterase (AChE) was studied by recording the changes in enzymatic activity following denervation in two types of autonomic ganglia in the frog,Rana pipiens. Opposite effects on AChE were found in the parasympathetic cardiac ganglion and in the sympathetic lumbar ganglion; denervation produced a significant increase in AChE activity in cardiac ganglia but a significant decrease in lumbar ganglia. The relative effects of denervation on intracellular and total AChE were examined by selectively inhibiting extracellular AChE with echothiophate, a poorly lipid‐soluble cholinesterase inhibitor. Denervation resulted in a significant increase in intracellular AChE in cholinergic cardiac ganglia but had no effect on intracellular AChE activity in adrenergic lumbar ganglia. Histochemical studies revealed little change in extracellular AChE staining upon denervation in the cardiac ganglion, whereas in the lumbar ganglia there was a loss of AChE‐specific reaction product. These results raise the possibility that the transsynaptic control of AChE activity by innervation in the frog is influenced by the transmitter synthetic properties of the postsynaptic ganglion cells.
Neuronal adaptation accompanying metamorphosis in the flatfish
Authors: Graf Werner , Baker Robert
Published: January 2005

Flatfish provide a natural paradigm to investigate adaptive changes in the central nervous system of vertebrates. During their metamorphosis, the animals undergo a 90° tilt to one side or the other to become the bottom‐adapted adult flatfish. The eye on the down side is pushed over to the up side. Thus, vestibular and oculomotor coordinate systems rotate 90° relative to each other. As a result, during swimming movements different types of compensatory eye movements are produced before and after metamorphosis by the same vestibular stimulation. Intracellular staining of central neurons with horseradish peroxidase revealed that in postmetamorphic flatfish second‐order horizontal canal neurons contact vertical eye muscle motoneuron pools on both sides of the brain via pathways that are absent in all other vertebrates studied. These unique connections provide the necessary and sufficient connectivity to adapt the flatfish's eye movement system to the animals' postmetamorphic existence. Although the adult fish has a bilaterally asymmetric appearance, the central nervous connectivity reestablishes symmetry in the vestibulooculomotor system.
Parallel motor pathways from thoracic interneurons of the ventral giant interneurons system of the cockroach, Periplaneta americana
Authors: Ritzmann Roy E. , Pollack Alan J.
Published: January 2005

The data described here complete the principal components of the cockroach wind‐mediated escape circuit form cercal afferents to leg motor neurons. It was previously known that the cercal afferents excite ventral giant interneurons which then conduct information on wind stimuli to thoracic ganglia. The ventral giant interneurons connect to a large population of interneurons in the thoracic ganglia which, in turn, are capable of exciting motor neurons that control leg movements. Thoracic interneurons that receive constant short latency inputs from ventral giant interneurons have been referred to as type A thoracic interneurons (TIAs). In this paper, we demonstrate that the motor response of TIAs occurs in adjacent ganglia as well as in the ganglion of origin for the TIA. We then describe the pathway from TIAs to motor neurons in both ganglia. Our observations reveal complex interactions between thoracic interneurons and leg motor neurons. Two parallel pathways exist. TIAs excite leg motor neurons directly and via local interneurons. Latency and amplitude of post‐synaptic potentials (PSPs) in motor neurons and local interneurons either in the ganglion of origin or in adjacent ganglia are all similar. However, the sign of the responses recorded in local interneurons (LI) and motor neurons varies according to the TIA subpopulation based on the location of their cell bodies. One group, the dorsal posterior group, (DPGs) has dorsal cell bodies, whereas the other group, the ventral median cells, (VMC) has ventral cell bodies. All DPG interneurons either excited postsynaptic cells or failed to show any connection at all. In contrast, all VMC interneurons either inhibited postsynaptic cells or failed to show any connection. It appears that the TIAs utilize directional wind information from the ventral giant interneurons to make a decision on the optimal direction of escape. The output connections, which project not only to cells within the ganglion of origin but also to adjacent ganglia and perhaps beyond, could allow this decision to be made throughout the thoracic ganglia as a single unit. However, nothing in these connections indicates a mechanism for making appropriate coordinated leg movements. Because each pair of legs plays a unique role in the turn, this coordination should be controlled by circuits didicated to each leg. We suggest that this is accomplished by local interneurons between TIAs and leg motor neurons.
Lateralization of syringeal function during song production in the canary
Authors: Hartley Rebecca S. , Suthers Roderick A.
Published: January 2005

The canary (Serinus canaria) vocal organ, the syrinx, has two separate sound sources, one in the cranial end of each bronchus. Previous investigations of whether song syllables are produced unilaterally or bilaterally have provided two contradictory results, as one researcher suggested that almost all syllables are produced by the left side of the syrinx alone, whereas another researcher suggested that both sides contribute similarly to all syllables. Our experiments, which involved unilateral bronchus plugging followed later by denervation of the ipsilateral syringeal muscles, attempted to resolve this disagreement. The males with right bronchus plugs, singing on the left side of the syrinx alone, produced nearly normal songs, whereas the birds with left bronchus plugs, singing on the right side, sang quite poorly. Interpretation of these data is difficult because it is not clear how syringeal function would be affected if the airflow rate through the intact side is increased above normal, nor is it known if the bird can compensate for bronchus occlusion. Nonetheless, we suggest that in male canaries most syllables are normally sung by the left side alone, with some syllables being produced by the right side alone and some being sung by both sides together. Right nerve section had little effect on the right‐bronchus‐plugged males' ability to sing, but the repertoires of the left‐plugged males were altered after left nerve section, indicating the possibility that signals carried by the left nerve exert an influence on the contralateral side.
Ependymin as a substrate for outgrowth of axons from cultured explants of goldfish retina
Authors: Schmidt John T. , Schmidt Rupert , Lin Weichun , Jian Xiaoying , Stuermer Claudia A. O.
Published: January 2005

Ependymin, a prominent protein of the brain's extracellular fluid (ECF) was‐previously implicated in the consolidation of memory and in the activity‐driven sharpening of the retinotectal projection. Because both these phenomena probably involve the growth and elaboration of appropriate synapses, we have tested whether ependymin can serve as a substrate for the growth of axons from goldfish retinal ganglion cells in a culture assay. Ependymin (Ep), laminin (LAM), polylysine (PL), and Concanavalin A (Con A) were plated on glass coverslips either uniformly or in striped patterns. Ep alone, either soluble or partly polymerized (by dropping calcium concentration and pH), was a good substrate for axonal outgrowth, as good or better than PL and Con A, but not as good as LAM. Neurites grew faster on LAM (71 μm/h) than on Ep (32 μm/h) or on PL (22 μm/h). Fasciculation was low on LAM, intermediate on Ep, and highest on PL. In exclusive side‐by‐side stripe assays, axons preferred LAM over Ep, but gave weak or no preference for Ep over Con A or PL. With stripes of LAM + Ep alongside pure LAM, the axons preferred the mixture of LAM + Ep. When antibodies to Ep were plated in stripes over continuous Ep substrate, the axons avoided the antibody‐blocked stripes and grew on the Ep stripes. Antibodies to Ep did not, however, block growth on laminin substrates, nor did antibodies to LAM block growth on Ep. Dot blots and western blots showed very little cross recognition between the antibodies. Ependymin is a good substrate for neurite outgrowth, which is normally present in ECF, and adhesion to Ep is independent of LAM and possibly additive to it.
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

The 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

The 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

In 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

The 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

The 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

The 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

We 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

In 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

With 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

Dopamine (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

Neuritogenesis 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

Tyrosine 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

Drosophila 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

This 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.
Right‐side dominance for song control in the zebra finch
Authors: Williams Heather , Crane Linda A. , Hale Timothy K. , Esposito Matthew A. , Nottebohm Fernando
Published: January 2005

Adult male zebra finches underwent unilateral denervation of the syrinx or unilateral lesion of the forebrain nucleus HVC known to be important for song control. Disruptive effects of song were greater after right‐side than after left‐side operations. After denervation of the right half of the syrinx, the fundamental frequencies of all syllables within a song converged on a value near 500 Hz, and nearly all syllables were altered in type. In contrast, the syllables produced after denervation of the left side of the syrinx largely maintained their preoperative frequencies, and fewer syllables changed in type. Unlike nerve sections, HVC lesions did not result in strikingly lateralized effects on syllable phonology; however, HVC lesions did affect the temporal patterning of a bird's song, whereas nerve sections did not, and changes in temporal patterning were more marked after right than after left HVC lesions. Right‐side dominance for zebra finch song control is the reverse of that described in other songbird species with lateral asymmetry for vocal communication. We suggest that the need for a dominant side is more important than the side of dominance. © 1992 John Wiley & Sons, Inc.
Cellular interactions determine neuronal phenotypes in rodent retinal cultures
Authors: Reh Thomas A.
Published: January 2005

Progenitor cells isolated from early rat embryo retinas differentiate into phenotypes normally generated early in retinal development (e.g., ganglion cells), whereas progenitors isolated from postnatal retinas differentiate into later‐generated retinal cell types (e.g., rod photoreceptors; Reh and Kljavin, J. Neurosci. 9:4179–4189; 1989; Adler and Hatlee, 1989; Science 243:391–393; Sparrow, Hicks, and Barnstable, 1990, Dev. Brain Res. 51:69–84). To determine whether this change in committment is intrinsic to the progenitor cells, or alternatively can be modified by interactions with their developing environment, I co‐cultured mouse and rat retinal cells, from different developmental stages, and identified the resulting phenotypes with species‐specific and cell class‐specific antibodies. I found that the phenotypes into which mouse neuroepithelial cells differentiate depends on the phenotypes of the rat cells that surround them. Retinal precursor cells from embryonic day (E) 10–12 will adopt the rod photoreceptor phenotype only when close to cells expressing this phenotype. By contrast, when the E10–12 retinal progenitor cells are cultured with cells from the cerebral cortex, they differentiate primarily into large multipolar neurons, similar in their morphology and antigen expression to retinal ganglion cells. These results indicate that interactions among the cells of the developing retina are important in the determination of cell fate. © 1992 John Wiley & Sons, Inc.
Influence of spinal cord transection on the presence and axonal transport of CGRP‐, chromogranin A‐, VIP‐, synapsin I‐, and synaptophysin‐like immunoreactivities in rat motor nerve
Authors: Li Jia‐Yi , Kling‐Petersen Anne , Dahlström Annica
Published: January 2005

Using immunofluorescence and cytofluorimetric scanning (CFS), we investigated the short‐term (1‐7 days) influence of lower thoracic spinal cord transection on lumbar motor neurons. The content of calcitonin gene‐related peptide‐ (CGRP) like immunoreactivity (LI), chromogranin A (Chr A) ‐LI, vasoactive intestinal polypeptide (VIP)‐LI, Syn I‐LI, and synaptophysin (p38)‐LI in motor perikarya, and the anterograde and retrograde axonal transport of these substances in the sciatic nerve, were studied in nerve crush (6 h) experiments. During the week after transection, CGRP‐LI in perikarya decreased, whereas Chr A‐LI increased. VIP‐LI, co‐localized with Chr A‐LI in motor perikarya, did not change after transection. The antero‐ and retrograde transport of CGRP‐LI in the sciatic nerve, occurring in both motor and sensory axons, appeared unchanged in cytofluorimetric scanning (CFS) graphs, but the microscopical picture clearly showed that large motor axons had a decreased content of CGRP‐LI at 3 and 7 days posttransection, whereas thinner axons were unchanged in fluorescence intensity. The anterograde transport of Chr A‐LI, present in both motor and postganglionic adrenergic axons, was decreased 1 and 3 days after lesion, but returned to control by day 7. There was a marked decrease in anterograde transport of VIP‐LI, present mainly in postganglionic sympathetic axons, at day 3, but at 7 days transport was normal. The amounts of transported p38, the synaptic vesicle marker, were in the normal range during the whole period. Syn I‐LI accumulation anterogradely was somewhat decreased at 3 and 7 days posttransection, and at 1 day the retrograde accumulation was significantly increased. The results suggest that removal of supraspinal input to intact lower motor neurons causes alterations in metabolism and axonal transport of organelle‐associated substances, partly probably related to the complex pattern of transmitter leakage from degenerating, descending nerve terminals. These alterations appear to take place also in postganglionic sympathetic neurons in the sciatic nerve, that originate in the lumbar sympathetic chain. © 1992 John Wiley & Sons, Inc.
Dendritic reorganization of an identified neuron during metamorphosis of the moth Manduca sexta: The influence of interactions with the periphery
Authors: Kent Karla S. , Levine Richard B.
Published: January 2005

During metamorphosis of the moth, Manduca sexta, an identified leg motor neuron, the femoral extensor motor neuron (FeExt MN) undergoes dramatic reorganization. Larval dendrites occupy two distinct regions of neuropil, one in the lateral leg neuropil and a second in dorsomedial neuropil. Adult dendrites occupy a greater volume of lateral leg neuropil but do not extend to the dorsomedial region of the ganglion. The adult dendritic morphology is acquired by extreme dendritic regression followed by extensive dendritic growth. Towards the end of larval life, MN dendrites begin to regress, but the most dramatic loss of dendrites occurs in the 3 days following pupation, such that only a few sparse dendrites are retained in the lateral region of leg neuropil. Extensive dendritic growth occurs over the subsequent days such that the MN acquires an adult‐like morphology between 12 and 14 days after pupation. This basic process of dendritic remodeling is not dependent upon the presence of the adult leg, suggesting that neither contact with the new target muscle nor inputs from new leg sensory neurons are necessary for triggering dendritic changes. The final distribution of MN dendrites in the adult, however, is altered when the adult leg is absent, suggesting that cues from the adult leg are involved in directing or shaping the growth of MN dendrites to specific regions of neuropil. © 1993 John Wiley & Sons, Inc.
Testosterone propionate administration prevents the loss of neurons within the central part of the medial peroptic nucleus
Authors: Dodson Robin E. , Gorski Roger A.
Published: January 2005

In the rat, the central part of the medial preoptic nucleus (MPNc) of the male is larger in volume and has a greater number of neurons than that of the female. The nucleus of the female, however, can be “sex reversed” by exposing the rat to gonadal steroids perinatally. The purpose of the present study was to examine the development of the MPNc to determine when the sex difference first appears and whether this difference occurs due to the relative accumulation of neurons into the compact part of the MPNc of the male and sex‐reversed female rat or to the loss of MPNc neurons in the control female. Pregnant, female Sprague‐Dawley rats were given an injection of [3H]methyl thymidine on embryonic day 18 (E18). Rats were exposed to testosterone propionate (TP) or vehicle from E20 to postnatal day 10 (PN10) or until the time of sacrifice. Pups from three groups [males (oil), females (oil), and sex‐reversed females (TP)] were sacrificed on PN2, PN4, PN7, PN10, or PN30. The volume of the compact part of the MPNc increased in males and sex‐reversed females after PN4 but the volume in the nucleus of females remained relatively constant. The number of neurons and [3H]thymidine‐labeled cells remained elevated from PN2–PN30 in males or sex‐reversed females but decreased dramatically in oiltreated females between PN4 and PN7, reaching a minimal number by PN10. Cell cross‐sectional area increased with age while cell density decreased. These observations are consistent with the hypothesis that the lack of growth of the compact part of the MPNc of the female is due to a loss of neurons while the increase in volume of the male's nucleus is due at least in part to growth of its constituent neurons. © 1993 John Wiley & Sons, Inc.
Hippocampal growth cone responses to focally applied electric fields
Authors: Davenport Roger W. , McCaig Colin D.
Published: January 2005

A wide variety of cell types respond to electric fields in culture. Despite evidence for electric fields existing in the mammalian embryo, there are few studies testing the effects electric fields exert on neurons from the mammalian central nervous system (CNS). The present study demonstrates orientation responses to focally applied electric fields of embryonic rat hippocampal neurons isolated in culture. The most striking result from this study is that different growth cones of the same neuron can show differential responsiveness to focally applied electric fields: growth cones on the short straight processes that are destined to become dendrites, oriented toward the cathode, whereas growth cones on the longest process, the presumptive axon, did not orient. The present experiments bring a significant increase in resolution to the study of neuronal growth cone orientation by applied electric fields: a novel examination of the early events leading to orientation. Growth cones on dendrites displayed a spectrum of orientation responses: directed lamellipodial extension, directed filopodial extension and/or reorientation, cytoplasmic swelling of existing filopodia, consolidation of filopodia, and rapid elongation of the entire process. Individual growth cones displayed only one or two of these responses. Additionally, not all growth cones on these short processes sustained their initial orientation response: 35% adapted within 6 min. © 1993 John Wiley & Sons, Inc.
A comparison of the development of neuropeptide and MAP2 immunocytochemical labeling in the macaque visual cortex during pre‐ and postnatal development
Authors: Mehra Raj D. , Hendrickson Anita E.
Published: January 2005

The appearance of Substance P (SP) and Neuropeptide Y (NPY) has been studied using light microscopic immunocytochemical labeling throughout the complete developmental span of Macaca nemestrina monkey striate cortex. In the adult, 80% of the NPY + neurons occur in the white matter (WM) and most of the remainder are medium to large multipolar neurons in layer 2. Fibers occur in all layers except 4C and are very numerous, given the relatively small number of NPY+ cell bodies. NPY+ neurons first were seen at embryonic day (E) 75. Most neurons were in the intermediate zone (IZ), but a few were in the immature cortical plate (CP). An adultlike distribution was present by E125 for neurons and by birth for fibers, but fiber staining intensity and number increased to postnatal year 1 (P1yr). In adult cortex, numerous SP+ nonpyramidal neurons were present in layers 2–6 and WM, but SP+ fibers were surprisingly infrequent. During development, significant numbers of SP+ neurons were not seen in the CP until E113–125. Later prenatal ages had a prominent plexus of SP+ cell bodies and fibers at the layer 5/6 border. This plexus disappeared by P12wk due to either down‐regulation of SP or cell death. SP+ neurons in IZ/WM were very sparse until birth after which they increased in number and staining intensity up to P1yr, suggesting a postnatal up‐regulation of SP in a preexisting WM subpopulation. Cell densities were determined for SP, NPY, and the neuron‐specific marker microtubule‐associated protein 2 (MAP2) to clarify the developmental dynamics of IZ/WM neurons. MAP2+ cell densities in WM peaked around birth and then declined 20% in the outer half and 77% in the inner half of WM. SP+ cell density rose 57% from birth to P20wk and then declined 20% into adult hood. NPY+ cell density was fairly constant prenatally and then rose 300% by adulthood. Neuropeptide cell density changes took place predominatly in the outer WM. These data indicate that cell death does occur in the general population of monkey striate cortical WM neurons. In contrast, both SP+ and NPY+ cells are characterized by minimal cell death and a late expression of neuropeptides which causes an increase in neuropeptide+ cell density in postnatal WM. © 1993 John Wiley & Sons, Inc.