bluuebunny/crossref_metadata_2025_split huggingface dataset:
The neural cell adhesion molecule and synaptic plasticity
Authors: Doherty Patrick , Fazeli Mohammed S. , Walsh Frank S. 
Published: January 2005

AbstractHighly stereotyped patterns of neuronal connections are laid down during the development of the nervous system via a range of activity independent and activity dependent mechanisms. Whereas the coarse hard‐wiring of the nervous system appears to rely on molecular recognition events between the neuron, its pathway, and its target, the establishment of precisely patterned functional circuits is thought to be driven by neuronal activity. In this review we discuss the role that the neuronal cell adhesion molecule (NCAM) plays in morphological plasticity. Recent studies on NCAM and its probable species homologue in Aplysia (apCAM) suggests that an individual CAM can function to both promote synaptic plasticity and maintain the structure of the synapse. In the adult brain, changes between stability and plasticity are likely to underlie dynamic morphological changes in synaptic structures associated with learning and memory. In this review we use NCAM as an example to illustrate mechanisms that can change the function of an individual CAM from a molecule that promotes plasticity to one that does not. We also discuss evidence that NCAM promotes plasticity by activating a conventional signal transduction cascade, rather than by modulating adhesion perse. Finally, we consider the evidence that supports a role for NCAM in learning and memory. © 1995 John Wiley & Sons, Inc.
Developmental expression of heterotrimeric G proteins in the nervous system of Manduca sexta
Authors: Copenhaver P. F. , Horgan A. M. , Nichols D. C. , Rasmussen M. A. 
Published: January 2005

AbstractThe heterotrimeric G proteins are a conserved family of guanyl nucleotide‐binding proteins that appear in all eukaryotic cells but whose developmental functions are largely unknown. We have examined the developmental expression of representative G proteins in the developing nervous system of the moth Manduca sexta. Using affinity‐purified antisera against different Gα subunits, we found that each of the G proteins exhibited distinctive patterns of expression within the developing central nervous system (CNS), and that these patterns underwent progressive phases of spatial and temporal regulation that corresponded to specific aspects of neuronal differentiation. Several of the G proteins examined (including Gsα and Goα) were expressed in an apparently ubiquitous manner in all neurons, but other proteins (including Giα) were ultimately confined to a more restricted subset of cells in the mature CNS. Although most of the G proteins examined could be detected within the central ganglia, only Goα‐related proteins were seen in the developing peripheral nerves; manipulations of G protein activity in cultured embryos suggested that this class of G protein may contribute to the regulation of neuronal motility during axonal outgrowth. Goα‐related protein were also localized to the developing axons and terminals of the developing adult limb during metamorphosis. These intracellular signaling molecules may, therefore, play similar developmental roles in both the embryonic and postembryonic nervous system. © 1995 John Wiley & Sons, Inc.
In situ hybridization reveals transient laminin B‐chain expression by individual glial and muscle cells in embryonic leech central nervous system
Authors: Luebke Anne E. , Dickerson Ian M. , Muller Kenneth J. 
Published: January 2005

AbstractLaminin, which strongly stimulates axon outgrowth in vitro, appears transiently within the central nervous system (CNS) in embryos. After CNS injury, laminin reportedly reappears along axonal pathways only in animal species in which central axon regeneration is successful, including the leech Hirudo medicinalis. Although glia have been suspected of making CNS laminin, in adult leeches glia are not required for laminin synthesis and evidently microglia, not present in the early embryo, produce laminin. To determine which embryonic cells make laminin, a 1.2 kb DNA fragment of leech laminin B1 chain, with homology to Drosophila, human, and mouse B1 laminins and rat S laminin, was isolated using reverse‐transcription and degenerate polymerase chain reaction (PCR) cloning. In situ hybridization revealed that laminin expression began before embryonic day 8, and by days 8 and 9 it was seen in paired CNS muscle cells. By late day 9, the two neuropil glial cells began to express laminin. Lucifer Yellow dye was injected intracellularly and muscle cells stimulated to contract, confirming the identities of muscle and glial cells. Packet glial cells began to express B1 laminin by embryonic day 12. By day 15, the cells of the perineurial sheath expressed B1 laminin, whereas it was no longer detectable in CNS muscle and glia. The results agree with published immunohistochemistry showing laminin within the CNS among growing axons by day 8, and only later in the perineurial sheath, by which time laminin disappears from within the CNS. Therefore, different cells synthesize laminin in the embryo and during repair in adults. © 1995 John Wiley & Sons, Inc.
Octopamine mediates rapid stimulation of protein kinase A in the antennal lobe of honeybees
Authors: Hildebrandt Herbert , Müller Uli 
Published: January 2005

AbstractIn the honeybee octopamine mediates mechanisms of arousal that interfere with the appetitive proboscis extension response to food‐indicating chemosensory stimuli. This study demonstrates that injections of octopamine or cyclic adenosine monophosphate (cAMP) into the primary chemosensory neuropil of the honeybee, the antennal lobe, evokes a rapid and transient activation of cAMP‐dependent protein kinase (PKA). Other monoamines detectable in the antennal lobe, dopamine and serotonin, do not affect the level of PKA activity. Stimulation of the bees' antenna with the appetitive stimulus water or sucrose solution in vivo also causes a short‐term activation of PKA in the antennal lobe. The increased PKA activity can be detected immediately (0.5 s) after stimulation but reverts to the basal level within 3 s. This effect can be abolished by monoamine depletion with reserpine. Since octopamine is the only monoamine that stimulates PKA, it appears to mediate the PKA activation after sucrose stimulus and may contribute to the processing of this chemosensory input. © 1995 John Wiley & Sons, Inc.
Regressive development in neuronal structure during song learning in birds
Authors: Nixdorf‐Bergweiler B. E. , Wallhäusser‐Franke E. , Devoogd T. J. 
Published: January 2005

AbstractWe investigated the development of spiny neurons in the lateral magnocellular nucleus of the anterior neostriatum before, during, and after song learning in male zebra finches (Taeniopygia guttata). The frequency of dendritic spines, dendritic field size, and branching characteristics were quantified at different ages in Golgi‐stained tissue using a three‐dimensional computerized tracing system. During development, overall spine frequencies increase between 3 and 5 weeks and decrease thereafter. In particular, spine frequencies of middle segments decrease significantly by 14% between 5 and 7 weeks posthatching (p = 0.017). A further reduction of 48% occurs between 7 weeks and adulthood (p < 0.001), resulting in a spine reduction of 56% on middle segments between 35 days of age and adulthood. In addition to the reduction of spine frequencies, we find regressive events also on some of the neuronal parameters that we have quantified. In general, dendrites of adult animals terminate closer to the cell body than those of 7‐, 5‐, or 3‐week‐old birds. Whereas no changes in segment length of first‐ and second‐order dendrites have been identified, third‐order dendrites end 19% closer to the cell body in adults than in younger birds (p < 0.024). Second‐order dendrites in adult animals branch less frequently than in 3‐week‐old animals (35%, p = 0.017). There is also a trend of a smaller number of tertiary branches in adulthood compared with 3‐week‐old birds (41%, p = 0.060). The morphological changes may be related to the function of this nucleus and the sensitive phase for song acquisition. © 1995 John Wiley & Sons, Inc.
Synapse formation and function: Insights from identified leech neurons in culture
Authors: Fernández‐de‐Miguel Francisco , Drapeau Pierre 
Published: January 2005

AbstractIdentified leech neurons in culture are providing novel insights to the signals underlying synapse formation and function. Identified neurons from the central nervous system of the leech can be removed individually and plated in culture, where they retain their characteristic physiological properties, grow neurites, and form specific synapses that are directly accessible by a variety of approaches. Synapses between cultured neurons can be chemical or electrical (either rectifying or not) or may not form, depending on the neuronal identities. Furthermore, the characteristics of these synapses depend on the regions of the cells that come into contact. The formation and physiology of synapses between the Retzius cell and its partners have been well characterized. Retzius cells form purely chemical, inhibitory synapses with pressuresensitive (P) cells where serotonin (5‐HT) is the transmitter. Retzius cells synthesize 5‐HT, which is stored in vesicles that recycle after 5‐HT is secreted on stimulation. The release of 5‐HT is quantal, calcium‐dependent, and shows activity‐dependent facilitation and depression. Anterograde and retrograde signals during synapse formation modify calcium currents, responses to 5‐HT, and neurite outgrowth. The nature of these synaptogenic signals is being elucidated. For example, contact specifically with Retzius cells induces a localized selection of transmitter responses in postsynaptic P cells. This effect is signaled by tyrosine phosphorylation prior to synapse formation. © 1995 John Wiley & Sons, Inc.
What we have learned from the study of learning in the leech
Authors: Sahley Christie L. 
Published: January 2005

AbstractThe use of invertebrate preparations has contributed greatly to our understanding of the neural basis of learning. The leech is especially useful for studying behavioral changes and their underlying neuronal mechanisms. Learning in the leech is essentially identical to that found in other animals, both vertebrate and invertebrate. Using anatomical and physiological techniques on leeches as they learn, we have begun to characterize the properties of individual neurons and neuronal networks that play a role in learning. We have been able to show two neuronal mechanisms that have not been previously associated with associative conditioning. The first has to do with the importance of contingency: one stimulus [the conditional stimulus (CS)] becomes associated with a second stimulus [the unconditional stimulus, (US)] in proportion to the ability of the CS to predict the US. We have found that important properties for encoding predictability, such as circuit reconfiguration, may lie in the US pathway. The firing of the serotonergic Retzius cells is taken as the US; consistent CS prediction of a US prevents “dropout” of a critical component of one US pathway. Throughout training, predicted USs continue to elicit a barrage of action potentials in these cells. Recurring unpredicted USs degrade both the learning and the response of the Retzius cell to the US. A second insight is that at least two US pathways contribute to learning, the Retzius cell pathway and the nociceptive (N) cell pathway. This second pathway persists after the elimination of the Retzius cell pathway. The observation of multiple US pathways raises a host of issues concerning CS–US convergence and the functional significance of distinct US pathways, and our results are discussed in terms of implications to current models of learning. © 1995 John Wiley & Sons, Inc.
Localization of tissue plasminogen activator mRNA in the developing rat cerebellum and effects of inhibiting tissue plasminogen activator on granule cell migration
Authors: Ware J. H. , DiBenedetto A. J. , Pitman R. N. 
Published: January 2005

AbstractTissue plasminogen activator (tPA) mRNA was localized in the developing cerebellum and the potentials role of tPA in migration of cerebellar granule cells was investigated. Proteolytic assays and Northern blots showed little variation in levels of tPA proteolytic activity or tPA mRNA expression in the developing cerebellum. The distribution of cerebellar tPA mRNA at different ages was visualized by in situ hybridization histochemistry. At postnatal day 7 (P7), most labeled cells were in the internal granule layer or developing white matter, and very few if any premigratory granule cells contained tPA mRNA. Although the molecular layer contained labeled cells at all ages, cell counts indicated that a greater percentage of cells in the molecular layer contained tPA mRNA during adulthood than during the period of granule cell migration. The most striking change in tPA mRNA expression was in Purkinje neurons, most of which began to express tPA mRNA between P7 and P14. The potential role of tPA in granule cell migration was investigated by performing migration assays in cerebellar slice explants in the presence or absence of protease inhibitors. The presence of inhibitors did not affect the distance that granule cells migrated. Data in the present study do not support a role for tPA in granule neuron migration; however, they do indicate that tPA is both spatially and temporally regulated during cerebellar development. Possible functions of tPA in the cerebellum are discussed. © 1995 John Wiley & Sons, Inc.
A mouse homolog of dunce, a gene important for learning and memory in drosophila, is preferentially expressed in olfactory receptor neurons
Authors: Cherry James A. , Davis Ronald L. 
Published: January 2005

AbstractThe dunce (dnc) gene in Drosophila codes for a cyclic adenosine monophosphate‐specific phosphodiesterase (PDE). Flies with a mutation at this locus exhibit severe deficits in learning and memory. We have begun to analyze the neural distribution of mammalian homologs of dnc in the mouse. Surprisingly, in situ hybridization and northern blotting using a probe specific for one of the four mammalian dnc homologs (mPDE2) reveals high levels of expression in the olfactory neuroepithelium. Anti mPDE2 antibody confirms that this PDE protein is abundant in the axons and dendrites of the olfactory receptor neurons but is conspicuosly absent from the cilia, where the initial events in olfactory signal transduction occur. Lower levels of mPDE2 were also detected throughout the brain and in the testis. These findings suggest an important modulatory role for mPDE2 in mammalian olfaction. © 1995 John Wiley & Sons, Inc.
Human schwann cells in vitro. I. Failure to differentiate and support neuronal health under co‐culture conditions that promote full function of rodent cells
Authors: Morrissey T. K. , Bunge R. P. , Kleitman N. 
Published: January 2005

AbstractSchwann cells (SCs) play critical roles in regeneration after injury to the peripheral nervous system and can also induce axonal regeneration in the central nervous system. Transplantation of purified SCs into sites of neural injury in rodents has confirmed the remarkable ability of these cells to promote axonal regrowth, suggesting that human application of SC transplantation could be valuable. In this report, we have compared the functional capacities of SCs derived from adult human and rodent nerves by maintaining SCs from these two sources in culture with sensory neurons. We noted that techniques commonly in use for maintaining pure rat SC populations are not sufficient to sustain populations of human SCs free of fibroblasts. In these co‐cultures, human SCs express a limited profile of characteristic behaviors and they proliferate more slowly than rat SCs in response to axonal contact, Slow SC proliferation, relative to that of contaminating fibroblasts, leads to a high proportion of fibroblasts in the cultures. After 3 to 4 weeks of co‐culture with neurons, human SCs express extracellular matrix molecules, but only partially ensheathe axons, whereas rat SCs differentiate, form basal lamina, and ensheathe or myelinate axons. Co‐culture of sensory neurons with human (but not rat) SC preparations (or conditioned medium therefrom) leads to a progressive neuronal atrophy characterized by shrinking neuronal cells bodies and a decrease in the density of the neurite network in the culture dish. As the divergent effects of human and rat SCs on neuronal health were also observed in co‐cultures with human sensory neurons, these effects reflect differences between the rat and human‐derived SC populations, rather than a species mismatch between SCs and neurons. The marked differences in behavior observed between rat and human SCs derived by the same methods requires further exploration if human‐derived SCs are to be considered in the treatment of disease. In a companion article we report experiments that define culture conditions more effective in promoting human SC function in vitro. © 1995 John Wiley & Sons, Inc.
Scutoid mutation of drosophila melanogaster specifically decreases olfactory responses to short‐chain acetate esters and ketones
Authors: Dubin Adrienne E. , Heald Nathan L. , Cleveland Byrd , Carlson John R. , Harris Greg L. 
Published: January 2005

AbstractA molecular‐genetic approach has been taken to identify genes involved in olfactory transduction in Drosophila melanogaster. Two independent lines of research led to the finding that the dominant Scutoid (Sco) mutation causes a diminshed extracellular electroantennogram response to the odorants ethyl acetate (EtAC) and acetone (AC). Sco flies showed about 4‐ and 2.5‐fold reduced responses to EtAC and AC, respectively, compared to Canton‐S wild‐type and sibling control flies lacking the Sco mutation when electroantennogram recordings were made from the proximal anterior third antennal segment. The responses to five other odors from three different chemical classes were unaltered. The maximum response to either EtAC or AC was decreased with no change in apparent affinity. Responses to short‐chain (but not long‐chain) acetate esters and ketones were dramatically affected at all antennal locations tested. Only in the proximal quadrants were responses to ethyl acetoacetate also reduced. Most Sco revertants tested had a normal olfactory response; duplications of the region including no‐ocelli partially suppress the Sco bristle as well as olfactory phenotypes. Sco adults had an impaired behavioral response to EtAC but not to banana or propionate. There was no effect of the mutation on larval chemosensory behavior or extracellularly recorded adult compound eye and ocellar visual responses. These findings suggest the involvement of Sco in an olfactory pathway in adults which is specific for short‐chain acetate esters and ketones. © 1995 John Wiley & Sons, Inc.
Importance of target innervation in recovery from axotomy‐induced loss of androgen receptor in rat perineal motoneurons
Authors: Al‐Shamma Hussien A. , Arnold Arthur P. 
Published: January 2005

AbstractIn adult male rats, axotomy of the spinal nucleus of the bulbocavernosus (SNB) motoneurons transiently down‐regulates androgen receptor (AR) immunoreactivity. The present study investigates the importance of target reinnervation in the recovery of AR expression in axotomized SNB motoneurons after short (up to 5 days) and long (1 to 6 weeks) periods of recovery. In the long‐term recovery experiment, animals were divided into two groups. In one, the two stumps of the cut pudendal nerve, which carries the axons of the SNB motoneurons, were sutured together immediately after axotomy. In the second group, the proximal stump was ligated immediately after axotomy to prevent target reinnervation. Axotomy of the SNB motoneurons caused a significant down‐regulation in AR immunoreactivity within 3 days. At 6 weeks, AR immunoreactivity was still depressed in ligated animals but had recovered to control levels in resutured animals. The recovery in the resutured group was coincident with the first signs of reinnervation of the target perineal muscles, although reinnervation seemed to lag behind AR immunoreactivity. SNB soma size was significantly reduced 2 weeks after axotomy and returned to control levels after 6 weeks of recovery only in the resutured animals. These findings suggest that the target perineal muscles play a role in the regulation of AR expression and androgen sensitivity in the SNB motoneurons, perhaps mediated by muscle‐derived trophic factors. © 1995 John Wiley & Sons, Inc.
A method for determining the melt elasticity in capillary flow
Authors: Han C. D. , Charles M. 
Published: December 2004

AbstractA method for determining the melt elasticity is developed. The method requires the measurement of axial pressure distribution in a capillary and makes use of the extrapolated value of the pressure at the exit of a capillary, the so‐called “residual pressure.” The same measurement also provides data for determining the flow curve. Measurements were taken with polyethylene and polypropylene. The results are presented and discussed with particular emphasis on the application of the method to various ways of processing polymers.
Dimensional recovery of cold‐rolled polycarbonate
Authors: Rusch K. C. 
Published: December 2004

AbstractThe dimensional recovery of cold‐rolled polycarbonate was measured between 100 and 147°C, and compared to stress‐relaxation data. The strain‐recovery isotherms were superimposed to produce a master curve which could be represented by a distribution function, U(τ), termed the strain recovery spectrum. U(τ) is found to be nearly identical to the relaxation spectrum, H(τ), calculated from the stress‐relaxation master curve; and the shift in U(τ) as a function of temperature, WLF shift factor, is similar to that obtained from other viscoelastic measurements on polycarbonate. For the deformations studied, 25 and 50% reduction in thickness, the recovery behavior is found to be independent of strain (linear), suggesting that nonlinearity in a polymer glass results from large stresses, and not from large strains.
Solids conveying in screw extruders part II: Non isothermal model
Authors: Tadmor Z. , Broyer E. 
Published: December 2004

AbstractIsothermal solids conveying theories have been developed in the past. However, due to friction, the surface temperature of the solid plug does increase. This change in temperature will strongly affect the temperature sensitive coefficients of friction and consequently also the pressure that develops. The surface temperature of the solid plug is also an important variable on its own because, when it reaches the melting point, the solids conveying zone is terminated. A mathematical model has been developed to calculate the temperature profile in the solid plug together with the strongly interacting pressure profile. Calculations indicate that high pressure in the solids conveying zone can practically be obtained only by very efficient cooling of the barrel in this zone.