bluuebunny/crossref_metadata_2025_split huggingface dataset:
Perturbed glial scaffold formation precedes axon tract malformation in Drosophila mutants
Authors: Jacobs J. Roger 
Published: January 2005

AbstractThe longitudinal glia (LG), progeny of a single glioblast, form a scaffold that presages the formation of longitudinal tracts in the ventral nerve cord (VNC) of the Drosophila embryo. The LG are used as a substrate during the extension of the first axons of the longitudinal tract. I have examined the differentiation of the LG in six mutations in which the longitudinal tracts were absent, displaced, or interrupted to determine whether the axon tract malformations may be attributable to disruptions in the LG scaffold. Embryos mutant for the gene prospero had no longitudinal tracts, and glial differentiation remained arrested at a preaxonogenic state. Two mutants of the Polycomb group also lacked longitudinal tracts; here the glia failed to form an oriented scaffold, but cytological differentiation of the LG was unperturbed. The longitudinal tracts in embryos mutant for slit fused at the VNC midline and scaffold formation was normal, except that it was medially displaced. Longitudinaltracts had intersegmental interruptions in embryos mutant for hindsight and midline. In hindsight, there were intersegmental gaps in the glial scaffold. In midline, the glial scaffold retracted after initial extension. LG morphogenesis during axonogenesis was abnormal in midline. Commitment to glial identity and glial differentiation also occurred before scaffold formation. In all mutants examined, the early distribution of the glycoprotein neuroglian was perturbed. This was indicative of early alterations in VNC pattern present before LG scaffold formation began. Therefore, some changes in scaffold formation may have reflected changes in the placement and differentiation of other cells of the VNC. In all mutants, alterations in scaffold formation preceded longitudinal axon tract formation. © 1993 John Wiley & Sons, Inc.
Enchancer detector analysis of the extent of genomic involvement in nervous system development in Drosophila melanogaster
Authors: Datta Sumana , Stark Karen , Kankel Douglas R. 
Published: January 2005

AbstractWe conducted a survey of the patterns of gene expression in the central nervous system (CNS) of larvae of the fruitfly Drosophila melanogaster to identify genes that may be important in the development of the CNS, aid in the recognition of basic organizing features that might underlie CNS development, and estimate the extent of the use of information encoded in the genome in the construction of the nervous system. A so‐called enhancer detector strategy was used to generate many thousands of lines containing a β‐galactosidase reporter gene. These lines were screened as third‐instar larvae for patterns of expression in the developing optic lobes and other portions of the CNS. Most of the lines recovered which evidence staining within the CNS could be included in one of a relatively small number of patterns. A random sample of 594 lines from the larger population screened was selected to quantify the relative frequencies of these patterns, and a more careful analysis of the changes in the patterns of expression with developmental time was done for representative lines of nine of the patterns. These studies demonstrated great variability in the patterns of gene expression as a function of developmental stage. Few, if any, lines showed β‐galactosidase activity limited to the optic lobes; similarly, few lines were identified in which staining was limited to only a small number of cells. Together with the limited number of patterns of gene expression seen, this suggests that in the larval CNS developmental pathways may be controlled by a combinatorial process of gene activity that involves the majority of the genome rather than by having a specific gene specify the fate of only a few neuronal precursors. © 1993 John Wiley & Sons, Inc.
Regeneration from crayfish phasic and tonic motor axonsin vitro
Authors: Egid Kathleen , Lnenicka Gregory A. 
Published: January 2005

AbstractAn explant culture system is described that allows examination of axonal growth from the tonically and phasically active motoneurons of the abdominal nerve cord of the crayfish. In this preparation, growth occurs from the cut end of the axon while the remainder of the motoneuron is undisturbed.In vitrogrowth from the branches of the third roots, which contain the axons from the tonic and phasic motoneurons of abdominal ganglia one through four, was verified as axonal by retrograde labeling of axons and neuronal somata within the nerve cord. Growth from the axons of phasic and tonic cells was observed as early as 24 h after plating and continued for an additional 7–10 days. The morphology and growth rates of the motor terminals differed between the tonic and phasic axons. The phasic axons grew significantly faster and branched more often than did the tonic motor axons. These differences in growth may be related to differences in motoneuron size or, may result from differences in electrical activity. Tonic motoneurons show spontaneous impulse activity for up to 6 days in culture, whereas phasic motoneurons show no spontaneous impulse activity. In addition, the differences in growth may be related to the morphological differences in tonic and phasic motor terminals observedin situ. © 1993 John Wiley & Sons, Inc.
Modulation of the enkephalinergic phenotype of rat sympathetic neurons by hormonal and transynaptic mechanisms
Authors: Henion Paul D. , Landis Story C. 
Published: January 2005

AbstractMost sympathetic neurons contain one or more neuropeptides in addition to catecholamines. Although the regulation of catecholamines has been studied extensively, comparatively little is known about the regulation of neuropeptides. Since glucocorticoids and preganglionic innervation regulate catecholaminergic properties in chromaffin cells, we examined the effects of these factors on a co‐localized neuropeptide, leucine enkephalin (L‐Enk), in adult rat sympathetic neurons in vivo. Lowered serum glucocorticoid levels as a consequence of bilateral adrenalectomy resulted in a reduction of ganglionic L‐Enk content that was reversed by exposure of adrenalectomized animals to the synthetic glucocorticoid, dexamethasone. Surgical denervation of the SCG eliminated L‐Enk‐IR preganglionic fibers and caused a dramatic increase in the number of L‐Enk‐IR neurons. Inhibition of the enkephalinergic component of the preganglionic innervation by chronic exposure to the opiate receptor antagonist naloxone increases the number of L‐Enk‐IR cell bodies and total ganglionic L‐Enk content. None of the experimental manipulations noticeably altered the number or distribution of NPY‐IR neurons, suggesting that the effects of glucocorticoids and the innervation on ganglionic L‐Enk levels were specific and not simply an alteration of the biosynthetic state of the cells. These results demonstrate that circulating glucocorticoids and the preganglionic innervation regulate L‐Enk levels in sympathetic neurons. Since both glucocorticoid levels and preganglionic activity are known to be altered by stressful stimuli, acute regulation of sympathetic L‐Enk levels may constitute an important component of the autonomic response to stress. © 1993 John Wiley & Sons, Inc.
Rin, a novel cell‐surface protein that labels reticular neurons early in chick neurogenesis
Authors: Chang Susannah , Raible David W. 
Published: January 2005

AbstractRin is a large cell‐surface glycoprotein that we have recently purified from chick brain, with a molecular weight of approximately 200 kD. Protein microsequence obtained from immunopurified rin does not match any sequences in the Genbank data base. Based on the sequences information and on its localization in the early chick embryo, rin is a novel cell‐surface protein. Rin is expressed on the surface of many, but not all, axons in the developing chick nervous system. In the chick hind‐brain, rin is expressed on reticular neurons, the first neurons to extend axons within the brain. Cranial motorneurons, which extend axons just a few stages later, do not express rin. Rin‐positive axons pioneer the caudal section of the medial longitudinal fasciculus. The very first rin‐positive axons that reach the floorplate do not enter the floorplate, but remain ipsilateral. Some of the next immunopositive axons to reach the floorplate do cross the midline, often with an alteration in trajectory, and often extending within the floorplate for some distance before reaching the other side. The failure of the very first rin‐positive axons to cross the floorplate, and the changes in trajectory observed when the next axons extend onto the floorplate, suggests that early differentiating neurons cross the midline with some difficulty. 1994 John Wiley & Sons, Inc.
The survival of rat cerebral cortical neurons in the presence of trophic APP peptides
Authors: Yamamoto Kyoko , Miyoshi Toshio , Yae Tetsuji , Kawashima Kazuaki , Araki Hiroaki , Hanada Kazunori , Otero Deborah A. C. , Roch Jean‐Marc , Saitoh Tsunao 
Published: January 2005

AbstractOne function of Alzheimer amyloid protein precursor (APP) is the regulation of growth and differentiation in several types of cells, including fibroblasts, PC12 cells, and neurons. This activity is represented by a small stretch of amino acids in the center of the molecule around RERMS. The APP 17‐mer peptide containing the RERMS domain supported survival and neurite extension of rat cortical neurons in a dose‐dependent and sequence‐specific manner. The APP fragment synthesized inEscherichia colisupported the survival and neurite extension of rat cortical neurons, whereas the mutant APP fragment lacking the 30 amino acids around the RERMS domain had drastically reduced activity to support the survival and neurite extension. The current study established APP as a neuron survival factor and determined that the sequence around RERMS is important for this function. © 1994 John Wiley & Sons, Inc.
FGF and EGF are mitogens for immortalized neural progenitors
Authors: Kitchens Daniel L. , Snyder Evan Y. , Gottlieb David I. 
Published: January 2005

AbstractIndividual neural progenitors, derived from the external germinal layer of neonatal murine cerebellum, were previously immortalized by the retrovirus‐mediated transduction of avian myc (v‐myc). C17‐2 is one of those cloanl multipotent progenitor cell lines (Snyder et al., 1992, Cell 68: 33–51; Ryder et al., 1990, J. Neurobiol. 21:356–375). When transplanted into newborn mouse cerebellum (CB), the cells participate in normal CB development; they engraft in a cytoarchitecturally appropriate, nontumorigenic manner and differentiate into multiple CB cell types (neuronal and glial) similar to endogenous progenitors (Snyder et al., 1992, as above). They also appear to engraft and participate in the development of multiple other structures along the neural axis and at multiple other stages (Snyder et al., 1993, Soc. Neurosci. Abstr. 19). Thus conclusions regarding these immortalized progenitors may be applicable to endogenous neural progenitors in vivo. To help identify and analyze factors that promote differentiation of endogenous progenitors, we first investigated the ability to maintain C17‐2 cells in a defined, serum‐free medium (N2). The cell survive in vitro in N2 but undergo mitosis at a very low rate. Addition of epidermal growth factor (EGF), however, either from mouse submaxillary gland or the human recombinant protein, appreciably stimulates thymidine incorporation and cell division approximately threefold. Basic fibroblast growth factor (bFGF) is an even more potent mitogen, promoting thymidine incorporation, cell division, and a net increase in cell number equal to that in serum. Both EGF and bFGF are active at very low nanomolar concentrations, suggesting that they interact with their respective receptors rather than a homologous receptor system. The findings demonstrate that C17‐2 cells can be maintained and propagated in a fully defined medium, providing the basis for analysis of other growth and differentiation factors. That EGF and particularly bFGF are mitogenic for these cells is in accord with recent observations on primary neural tissue (Reynolds and Weiss, 1992, Science 255:1707–1710; Kilpatrick and Barlett, 1993, Neuron 10:255–265; Ray et al., 1993, Proc. Natl. Acad. Sci. U.S.A. 90: 3602–3606) suggesting that bFGF and EGF responsiveness may be fundamental properties of neural progenitors. 1994 John Wiley & Sons, Inc.
Selective expression of glionexin, a glial glycoprotein, in insect mechanoreceptors
Authors: Field L. H. , Meyer M. R. , Edwards J. S. 
Published: January 2005

AbstractThe distribution of a glial cell‐associated glycoprotein, glionexin (GX), on sensory receptors of the adult cricket Acheta domesticus is described, using the monoclonal antibody 5B12 as an immunohistochemical probe. GX was previously shown to be widely distributed in the embryo and to persist in the postembryonic to adult central nervous system. Here we demonstrate that it is restricted in the adult periphery to three subclasses of mechano‐receptor sensilla: large socketed hair mechanoreceptors, their associated campaniform sensilla, and chordotonal organs. GX was not detected in photoreceptors, chemoreceptors, or other mechanoreceptors. The pattern of distribution differs significantly within the three subclasses of mechanoreceptors. In the hair and campaniform receptors GX is restricted to the extracellular space among glial cells clustered around the axon hillock region, but in chordotonal organs it surrounds the scolopidium at the tip of dendrites. The highly restricted distribution of GX in the periphery suggests possible functions that include mechanical stability of the sensory apparatus and ionic homeostasis in the respective neuronal spike‐generating regions. The developmental modulation of GX expression is taken to imply multiple functions for the molecule during the life of the insect. 1994 John Wiley & Sons, Inc.
Sexual differentiation in the CNS of the moth, Manduca sexta. II. Target dependence for the survival of the imaginal midline neurons
Authors: Thorn Robert S. , Truman James W. 
Published: January 2005

AbstractWhile majority of the neurons in the adult nervous system of the moth Manduca sexta are produced postembryonically, little is known about how these cells interact with their targets during development. Few of these cells are motor neurons; most of Manduca's adult motor neurons are respecified larval motor neurons do develop postembryonically, including a large class of mixed neurosecretory and motor neurons called the imaginal midline neurons (IMNs). A subset of these cells show an unusual pattern of sex‐specific development and survival (Thorn and Truman, 1994, J. Neurobiol. in press), which led us to suspect that factors extrinsic to the cells were controlling their fates. We analyzed one such potential factor by altering the contacts between a subset of these developing IMNs and their adult‐specific target, the male sperm duct.When we transected the nerve that innervated the sperm duct in the pupa, we observed a loss of many sperm duct IMNs. In contrast, a transection of the same nerve in larvae showed no neuron loss. Immunocytochemistry showed that the pupal nerve transections were accompanied by a loss of axon endings on the sperm duct, while the larval nerve transections showed no such loss. Using local hormone application to slow the development of the sperm duct while leaving the nerve intact still resulted in a loss of IMNs. These results suggest that these IMNs need contact with a robust developing target in the pupa to survive metamorphosis. 1994 John Wiley & Sons, Inc.
Re‐evaluation of the absolute threshold and response mode of the most sensitive know “vibration” detector, the cockroach's subgenual organ: A cochlea‐like displacement threshold and a direct response to sound
Authors: Shaw Stephen R. 
Published: January 2005

AbstractEarlier accounts claim from indirect measurements that the subgenual organ (SGO) in the proximal tibia of the cockroach leg can detect vibrational displacements down to 0.002 mm, two orders of magnitude below the threshold for vertebrate hair cells in the cochlea. The SGO vibration threshold is redetermined here more directly by a new method on a cantilever beam, while controlling for particular acoustic and vibrational artifacts that might have compromised earlier efforts. The threshold is revised upwards to about 0.2 mm in the most sensitive preparation, about the same as cochlea. Recently, it has been determined that the cockroach SGO also has an auditory response, and the data here on subthreshold summation and response‐intensity relationships provide further evidence that sound and contact vibration are both sensed by the same receptor neurons. Direct measurements rule out the prevailing hypothesis that sound is detected indirectly as induced vibration of the ground, and also weigh strongly against any significant involvement of generalized leg resonance in acoustic pick‐up. The results fit with a recent proposal that the auditory response is direct, and that acoustic fluctuations inside the tracheae may be the primary response mode in the transduction of both vibration and sound. 1994 John Wiley & Sons, Inc.
Involvement of protein kinase C in the axonal growth‐promoting effect on spinal cord neurons by target‐derived astrocytes
Authors: Qian Jiang , Wang Hoau‐Yan , Fischer Itzhak , Friedman Eitan , Levitt Pat 
Published: January 2005

AbstractAstroglial cells participate in a variety of developmental events during neuronal morphogenesis. We have shown that axonal, but not dendritic, outgrowth of spinal cord neurons can be promoted by a diffusible factor or factors secreted from target region‐derived cerebellar astroglia in vitro in comparison with spinal astroglia. In the present study, we examined the involvement of protein kinase C (PKC) in the axon‐promoting effect by astroglia. The inhibition of PKC by sphingosine or by the phorbol ester 12‐O‐tetradecanoylphorbol 13‐acetate (TPA) at high concentration greatly reduced the mean axonal length of spinal neurons cultured in medium conditioned by cerebellar astroglia (SCn‐CBg), while activation of PKC by TPA at low concentration, or by retinoic acid, was not additive to the glial effect. The activation of PKC by TPA or retinoic acid promoted axon growth of spinal neurons cultured in medium conditioned by spinal astroglia (SCn‐SCg), which otherwise would not be as supportive for axon growth as cerebellar astroglia. Western blotting and PKC activity assays showed that there was a trend for increased PKC activity and protein levels (in particular, PKCβ) in SCn‐CBg cultures, which correlated with enhanced axon growth. Inhibition of PKC by sphingosine appeared to decrease protein levels, especially PKCβ, which correlated with suppressed axon outgrowth. In SCn‐SCg cultures, phorbol ester activation of PKC increased both activity and protein levels of both PKCα and PKCβ. This activation correlated with stimulated axonal outgrowth. These results suggest that the glial signaling that regulates specific axonal outgrowth by target astroglia is mediated in part by the PKC second messenger system. © 1994 John Wiley & Sons, Inc. 1994 John Wiley & Sons, Inc.
A human glial hybrid cell line differentially expressing genes subserving oligodendrocyte and astrocyte phenotype
Authors: McLaurin Joanne , Trudel Geralyn C. , Shaw Ivan T. , Antel Jack P. , Cashman Neil R. 
Published: January 2005

AbstractWe have developed a series of immortal human‐human hybrid cell lines that express phenotypic characteristics of primary oligodendrocytes, by fusing a 6‐thioguanine–resistant mutant of the human rhabdomyosarcoma RD with adult human oligodendrocytes by a lectin‐enhanced polyethylene glycol procedure. Hybrids were selected in an aminopterin‐containing media. In contrast to the tumor parent cells, a hybrid clone M03.13 expressed surface immunoreactivity for galactosyl cerebroside and intracellular immunoreactivity for myelin basic protein (MBP), proteolipid protein (PLP), and glial fibrillary acidic protein (GFAP). Serum deprivation or chronic treatment with a protein kinase C activator 4‐β‐phorbol 12‐myristate 13‐acetate (PMA), but not dibutyl cyclic adenosine monophosphate induced coordinate up‐regulation or de novo induction of oligodendrocyte phenotypic markers with concomitant down‐regulation of GFAP expression. Consistent with immunohistochemical studies, northern blot analysis demonstrated that both MBP and PLP mRNA were up‐regulated in MO3.13 cells by PMA treatment. M03.13 cells provide an immortalized clonal model system suitable for study of gene expression subserving oligodendrocyte and astrocyte phenotypes. © 1995 John Wiley & Sons, Inc.
Spontaneous calcium transients regulate neuronal plasticity in developing neurons
Authors: Spitzer Nicholas C. , Olson Eric , Gu Xiaonan 
Published: January 2005

AbstractCalcium ions play critical roles in neuronal differentiation. We have recorded transient, repeated elevations of calcium in embryonic Xenopus spinal neurons over periods of 1 h in vitro and in vivo, confocally imaging fluo 3‐loaded cells at 5 s intervals. Calcium spikes and calcium waves are found both in neurons in culture and in the intact spinal cord. Spikes rise rapidly to approximately 400% of baseline fluorescence and have a double exponential decay, whereas waves rise slowly to approximately 200% of baseline fluorescence and decay slowly as well. Imaging of fura 2‐loaded neurons indicates that intracellular calcium increases from 50 to 500 nM during spikes. Both spikes and waves are abolished by removal of extracellular calcium. Developmentally, the incidence and frequency of spikes decrease, whereas the incidence and frequency of waves are constant. Spikes are generated by spontaneous calcium‐dependent action potentials and also utilize intracellular calcium stores. Waves are produced by a mechanism that does not involve classic voltage‐dependent calcium channels. Spikes are required for expression of the transmitter GABA and for potassium channel modulation. Waves in growth cones are likely to regulate neurite extension. The results demonstrate the roles of a novel signaling system in regulating neuronal plasticity, that operates on a time scale 104 times slower than that of action potentials. © 1995 John Wiley & Sons, Inc.
Multiple forms of long‐term potentiation and multiple regulatory sites of N‐methyl‐D‐aspartate receptors: Role of the redox site
Authors: Gozlan H. , Khazipov R. , Ben‐Ari Y. 
Published: January 2005

AbstractLong‐term potentiation (LTP) is a form of synaptic plasticity thought to be involved in learning and memory. Althrough extensively studied, mainly in the CA1 region of the hippocampus, the mechanisms underlying the induction and expression of LTP are poorly elucidated. This is probably due to the fact that LTP is not a unique process and indeed recent studies have shown that several forms of LTP could be generated depending on the experimental conditions. Furthermore, LTP is generally associated with a long‐lasting increase of the synaptic efficacy of AMPA receptors but an increasing number of data also suggested that NMDA receptors could be potentiated as well. NMDA receptor responses are modulated by a large number of extracellular and intracellular events, providing additional possibilities for the generation of LTP. The role of these different modulatory sites of the NMDA receptor and their relation with LTP are reviewed with a particular attention to the redox site which seems to be a selective target to distinguish between AMPA and NMDA‐LTP. © 1995 John Wiley & Sons, Inc.