bluuebunny/crossref_metadata_2025_split huggingface dataset:
GAP‐43 mRNA in Rat Spinal Cord and Dorsal Root Ganglia Neurons: Developmental Changes and Re‐expression Following Peripheral Nerve Injury
Authors: Chong M. S. , Fitzgerald M. , Winter J. , Hu‐Tsai M. , Emson P. C. , Wiese U. , Woolf C. J. 
Published: April 2006

AbstractThe expression of growth‐associated protein GAP‐43 mRNA in spinal cord and dorsal root ganglion (DRG) neurons has been studied using an enzyme linked in situ hybridization technique in neonatal and adult rats. High levels of GAP‐43 mRNA are present at birth in the majority of spinal cord neurons and in all dorsal root ganglion cells. This persists until postnatal day 7 and then declines progressively to near adult levels (with low levels of mRNA in spinal cord motor neurons and 2000–3000 DRG cells expressing high levels) at postnatal day 21. A re‐expression of GAP‐43 mRNA in adult rats is apparent, both in sciatic motor neurons and the majority of L4 and L5 dorsal root ganglion cells, 1 day after sciatic nerve section. High levels of the GAP‐43 mRNA in the axotomized spinal motor neurons persist for at least 2 weeks but decline 5 weeks after sciatic nerve section, with the mRNA virtually undetectable after 10 weeks. The initial changes after sciatic nerve crush are similar, but by 5 weeks GAP‐43 mRNA in the sciatic motor neurons has declined to control levels. In DRG cells, after both sciatic nerve section or crush, GAP‐43 mRNA re‐expression persists much longer than in motor neurons. There was no re‐expression of GAP‐43 mRNA in the dorsal horn of the spinal cord after peripheral nerve lesions. Our study demonstrates a similar developmental regulation in spinal cord and DRG neurons of GAP‐43 mRNA. We show moreover that failure of re‐innervation does not result in a maintenance of GAP‐43 mRNA in axotomized motor neurons.
Cell Type‐specific Effects of the Neural Adhesion Molecules L1 and N‐CAM on Diverse Second Messenger Systems
Authors: von Bohlen und Halbach Friedrich , Taylor Joanne , Schachner Melitta 
Published: April 2006

AbstractWe have previously shown that the neural adhesion molecules L1 and N‐CAM influence second messenger systems when triggered with specific antibodies at the surface of the phaeochromocytoma PC12 cell line (Schuch et al., Neuron, 3, 13–20, 1989). To determine whether the two molecules are linked to the same intracellular signalling cascades, independent of the cell type expressing them, or whether different neural cell types respond with different signal transduction mechanisms, we have investigated the effects of antibodies to L1 and N‐CAM, and the isolated molecules themselves, on second messenger systems in different neural cell types. We have investigated cultures of cerebellar and dorsal root ganglion neurons and transformed Schwann cells and related these results to those obtained with the PC12 cell line. Here we show that addition of L1 and N‐CAM antibodies and the isolated molecules themselves elicit cell type‐specific responses that can be modulated by the substrate on which the cells are maintained. Depending on the cell type, cells respond to the triggering of L1 and N‐CAM with antibodies, or addition of the purified molecules, by either up‐regulation or down‐regulation of inositol phosphate turnover, by a rise in intracellular Ca2+ levels dependent on or independent of the opening of voltage‐gated Ca2+ channels, or by an increase or decrease in intracellular pH. Moreover, cerebellar neurons expressing N‐CAM respond to addition of N‐CAM, but not to N‐CAM antibodies, in contrast to the other neural cell types studied, which respond to both triggers. Furthermore, cerebellar neurons were the only cells to show a rise in cAMP levels in response to any of the ligands tested. This stimulation of cAMP production by L1 antibodies depended on the cross‐linking of L1 molecules at the cell surface, whereas the other responses did not depend on clustering of L1. Simultaneous addition of L1 and N‐CAM antibodies either elicited an additive or more than additive effect on the intracellular responses which, for cerebellar neurons, depends on the substrate on which the cells are maintained. These observations indicate that L1 and N‐CAM or their antibodies activate cell type‐specific intracellular signalling systems and that the two molecules can act interdependently or independently of each other.
Protein SP40,40‐like Immunoreactivity in the Rat Brain: Progressive Increase With Age
Authors: Senut M. C. , Jazat F. , Choi N. H. , Lamour Y. 
Published: April 2006

AbstractThe pattern of distribution of SP40,40‐like immunoreactive structures has been studied in the rat brain using a well‐characterized polyclonal antibody raised against the SP40,40 protein. Protein SP40,40 is the human counterpart of the rat sulphated glycoprotein 2, whose mRNA shows widespread expression in the developing and mature brain. In young adult rats few immunoreactive structures were observed. Some immunoreactive neurons were found in the cingulate cortex, the arcuate and perifornical hypothalamic nuclei, as well as glial labelling in the hypothalamus. A striking increase in the number of immunoreactive cells was observed as a function of age. In 20–22‐month‐old rats, numerous immunoreactive cells were observed in the cingulate cortex, several thalamic and hypothalamic nuclei, the red nucleus, olivary nuclei, superior colliculus, and many cranial nerve nuclei. Whereas the immunoreactivity was restricted to a diffuse labelling of the cell bodies and processes in young rats, other forms of labelling were observed in aged rats: punctate cytoplasmic labelling and intensely stained granules with no visible cell membrane. A further increase in the density of the immunoreactive material was observed in 30–31‐month‐old rats. Double labelling experiments demonstrated that the SP40,40 immunoreactivity was almost exclusively located in neurons and not in glial cells (with the exception noted above). The distribution of SP40,40 immunoreactivity in aged rats did not coincide with the distribution of the microtubule‐associated tau protein, OX42 or lipofuscin.
Quantitative Autoradiographic Demonstration of Changes in Binding to NMDA‐sensitive [3H]Glutamate and [3H]MK801, but not [3H]AMPA Receptors in Chick Forebrain 30 min After Passive Avoidance Training
Authors: Stewart Michael G. , Bourne Rachel C. , Steele Robert J. 
Published: April 2006

AbstractDay‐old domestic chicks (Gallus domesticus) were trained on a one‐trial passive avoidance task in which the aversive stimulus was an unpleasant tasting substance, methyl anthranilate. Thirty minutes later, localization of N‐methyl‐d‐aspartic acid (NMDA)‐sensitive [3H]glutamate receptor binding sites, [3H]MK801 and [3H]AMPA binding sites in 17 regions of the forebrain of methylanthranilate‐trained and control (water‐trained) chicks was determined using quantitative receptor autoradiography. Significant differences in binding to both MK801‐ and NMDA‐sensitive glutamate receptors, but not α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptors, were found in three regions of the forebrain of trained compared to control chicks; two of these regions have been implicated from previous lesion, biochemical and morphological studies as playing a key role in the process of memory formation and storage following passive avoidance training. For NMDA‐sensitive [3H]glutamate receptors, significant elevations in binding were observed in two regions, the left intermediate and medial hyperstriatum ventrale (IMHV) (39%) and the lobus parolfactorius (LPO) (34%), at 30 min post‐training, but a decrease (44%) occurred in binding to the lateral neostriatum. Significant increases in binding to MK801 receptors were observed in the left IMHV (19%) and right IMHV (13%), and left LPO (22%) at 30 min post‐training, though there was a decrease in the right LPO (15%). These findings, coupled with those described in a previous paper from our group (Burchuladze and Rose, Eur. J. Neurosci., 4, 533–538, 1992), demonstrate that a glutamate receptor subtype is involved in learning and memory formation in the chick.
Differential Expression of Markers and Activities in a Group of PC12 Nerve Cell Clones
Authors: Clementi Emilio , Racchetti Gabriella , Zacchetti Daniele , Panzeri Maria Carla , Meldolesi Jacopo 
Published: April 2006

AbstractSixteen clones, recently isolated from the PC12 nerve cell line, were analysed for a variety of markers and activities. Two endoplasmic reticulum (ER) luminal markers, the chaperone protein BiP and the major Ca2+ storage protein calreticulin, as well as the 40‐kD rough ER membrane marker and the plus‐end‐directed mirotubule motor protein, kinesin, were found to be expressed at similar levels. These results suggest that the size of the ER, the function of microtubules and the capacity of the rapidly exchanging Ca2+ store do not change substantially among the clones. Other proteins expressed at comparable levels were synapsin I and IIa, members of a nerve cell‐specific protein family known to bind synaptic vesicles to the cytoskeleton. In contrast, another ER membrane protein, calnexin, and the markers of secretory organelles were found to vary markedly. One clone (clone 27) completely lacked both chromogranin B and secretogranin II, the proteins contained within dense granules, and synaptophysin, a marker of clear vesicles. Other clones expressed these markers to variable and apparently mutually unrelated levels. Marked variability was observed also in the uptake of exogenous catecholamines, in their release both at rest and after stimulation, and in nerve growth factor‐induced differentiation. These results provide indirect information about the mechanisms that regulate the expression of structures and activities in PC12 cells. Of particular interest is clone 27, which appears globally incompetent for regulated secretion and might therefore be a valuable tool for the study of this activity in a nerve cell.
Plasticity of μ and δ Opioid Receptors in the Superficial Dorsal Horn of the Adult Rat Spinal Cord Following Dorsal Rhizotomies: A Quantitative Autoradiographic Study
Authors: Besse D. , Lombard M. C. , Besson J. M. 
Published: April 2006

AbstractThe aim was to study the regulation of μ and δ opioid binding sites in the superficial layers (laminae I–II) of the dorsal horn of the adult rat spinal cord 1, 2, 4 and 12 weeks after unilateral dorsal rhizotomies of various extents. Using quantitative autoradiography and highly selective tritiated opioid ligands, we have shown that the decrease in [3H]Tyr*‐d‐Ala‐Gly‐NMe‐Phe‐Gly‐ol ([3H]DAMGO) (μ sites) and [3H]Tyr*‐d‐Thr‐Gly‐Phe‐Leu‐Thr ([3H]DTLET) (δ sites) binding in the side ipsilateral to the lesion as compared to the intact side is related to the number of dorsal roots cut. In the segment central to the lesion, 1 week after the lesion, ipsilateral/contralateral side binding ratios for [3H]DAMGO were 0.70, 0.49, 0.36 and 0.25 when 1, 3, 5 and 7 roots respectively were sectioned. For [3H]DTLET, the ratios were 0.71, 0.54, 0.42 and 0.39. The time‐related analysis of binding ratios showed that, in partially deafferented spinal segments after long‐term deafferentation (12 weeks postlesion) there were greater numbers of μ and δ binding sites than in cases of short‐term deafferentation (1–2 weeks). By contrast, in spinal segments considered as completely deafferented, there was no difference in the remaining μ and δ binding sites at 12 weeks as compared to 1 week postlesion. Consequently, it is deduced that the partial recovery of μ and δ binding observed after long‐term partial deafferentation could be associated with neuronal plasticity (probably collateral sprouting) of fine diameter primary afferent fibres arising from intact dorsal roots.
The Effectiveness of the Gene Which Slows the Rate of Wallerian Degeneration in C57BL/Ola Mice Declines With Age
Authors: Perry V. H. , Brown M. C. , Tsao J. W. 
Published: April 2006

AbstractThe rate of Wallerian degeneration is unusually slow in severed axons of mice of the C57BL/Ola strain. Within mice of that strain we have now found that the rate of degeneration increases with the age of the animal. In 4‐week‐old mice nerve stimulation evokes muscle contractions even 5 days after sciatic nerve section and compound action potentials can be recorded in the distal nerve stump up to 3 weeks after section. In 1‐year‐old animals no action potentials can be excited 5 days after nerve section. Heterozygous mice carrying only one copy of the dominant gene show the same age‐related decline in viability of the distal nerve stump after axotomy, and the rate of decline is no greater than for homozygous mice. The more rapid rate of degeneration of severed axons of mice of the C57BL/6J strain was affected in the opposite way by age, degeneration occurring more slowly in older animals.
The Extent of the Dendritic Tree and the Number of Synapses in the Frog Motoneuron
Authors: Birinyi A. , Antal M. , Wolf E. , Székely G. 
Published: April 2006

AbstractFrog motoneurons were intracellularly labelled with cobaltic lysine in the brachial and the lumbar segments of the spinal cord, and the material was processed for light microscopy in serial sections. With the aid of the neuron reconstruction system NEUTRACE, the dendritic tree of neurons was reconstructed and the length and surface area of dendrites measured. The surface of somata was determined with the prolate – oblate average ellipsoid calculation. Corrections were made for shrinkage and for optical distortion. The mean surface area of somata was 6710 μm2; lumbar motoneurons were slightly larger than brachial motoneurons. The mean length of the combined dendritic tree of brachial neurons was 29 408 μm and that of lumbar neurons 46 806 μm. The mean surface area was 127 335 μm2 in brachial neurons, and 168 063 μm2 in lumbar neurons. The soma – dendrite surface area ratio was 3 – 5% in most cases. Dendrites with a diameter of ≤ 1.0 μm constituted ∼ 75% of the combined dendritic length in most of the neurons. Unlike in the cat, there was no correlation between the size of stem dendrites and the extent of daughter branches. From the synaptic density estimated in earlier electron microscope investigations of frog motoneuron dendrites (Antal et al., J. Neurocytol., 15, 303–310, 1986; 21, 34–49, 1992), and from the present data, the number of synapses on the dendritic tree was calculated. The calculations indicated 26 949 synapses on the smallest and 61 519 synapses on the largest neuron if the synaptic density was multiplied by the length of the dendritic tree. If the synaptic density was multiplied by the surface area of the dendritic tree the calculation yielded 23 337 synapses for the smallest and 60 682 synapses for the largest neuron. More than 60% of the combined surface area of dendrites was >600 μm from the soma. This suggests that about two‐thirds of the synapses impinged upon distant dendrites >600 μm from the soma. The efficacy of synapses at these large distances is investigated on model neurons in the accompanying paper (Wolf et al., Eur. J. Neurosci., 4, 1013–1021, 1992).
Phase‐dependent Modulation of a Cutaneous Sensory Pathway by Glycinergic Inhibition from the Locomotor Rhythm Generator in Xenopus Embryos
Authors: Sillar Keith T. , Roberts Alan 
Published: April 2006

AbstractIn immobilized Xenopus laevis embryos two classes of sensory interneuron are excited by mechanosensory Rohon‐Beard neurons and rhythmically inhibited during fictive swimming. Dorsolateral commissural (DLC) interneurons are inhibited in time with rhythmic motor discharge on the same side as their soma, while unidentified dorsolateral (DLX) interneurons are inhibited in the opposite phase of the swimming rhythm. The inhibition is abolished by bath application of strychnine sulphate at 1–10 μM, but not by the γ‐aminobutyric acid antagonists bicuculline (20–40 μM) or curare (70–100 μM). The inhibitory postsynaptic potentials (IPSPs) involve an increase in chloride conductance since they are reversed in sign to become depolarizing following intracellular injection of chloride ions. The conductance increase during inhibition was able to block impulses evoked by intracellular current in a phase‐dependent manner, suggesting that postsynaptic inhibition is sufficient to account for the gating of afferent input to the spinal cord during swimming. An interneuron receives IPSPs that are predominantly in one phase of the rhythm, but most interneurons are also inhibited sporadically in the opposite phase. The amplitude and time course of the IPSPs closely follow the frequency of the swimming rhythm, with maximal inhibition occurring near the starts of episodes, when swimming frequency is at its highest. Towards the end of an episode, when swimming frequency declines, the level of inhibition is low, the membrane potential of the interneurons returns to rest between cycles, and IPSPs often fail to occur. Inhibition suppresses sensory excitation in a phase‐dependent manner (cf. Sillar and Roberts, Nature, 331, 262–265, 1988). Sensory interneurons fire a single impulse in response to a brief sensory stimulus, but they will usually fire multiple impulses when depolarized with sufficient intracellular current. In some sensory interneurons a short‐latency IPSP follows the impulse evoked by skin stimulation that could curtail impulse activity. However, when the inhibition is blocked by strychnine, sensory interneurons still fire a single short‐latency impulse, favouring the conclusion that brief, synchronized afferent excitation elicits a single impulse in neurons that are capable of firing multiply. Since the inhibition of DLC interneurons occurs in phase with activity on the same side it probably originates from spiking in ipsilateral glycinergic commissural interneurons which have ipsilateral as well as contralateral projections. The inhibition of DLX interneurons in the opposite phase probably originates from the contralateral projections of commissural interneurons.
Ca2+ Channel Expression in the Oligodendrocyte Lineage
Authors: Blankenfeld Gabriela v. , Verkhratsky Alexej N. , Kettenmann Helmut 
Published: April 2006

AbstractThe development of oligodendrocytes from their precursor cells through different developmental stages can be studied in vitro. These stages can be distinguished by specific monoclonal antibodies and by a characteristic K+ channel profile. In this study we demonstrate that the occurrence of Ca2+ currents also undergoes marked changes during the development of mouse oligodendrocytes. Immature precursor cells which can develop into astrocytes or oligodendrocytes expressed two different types of voltage‐activated Ca2+ channels. The expression of Ca2+ channels in precursor cells was strongly correlated with the expression of Na+ channels. When cells started to express the O1 antigen and were committed to the oligodendrocyte lineage, Ca2+ and Na+ currents could no longer be detected. Large Ca2+ currents were, however, recorded later in the development of the oligodendrocytes, correlated with the expression of the O10 antigen. The Ca2+ channels were classified as high and low voltage‐activated Ca2+ channels according to their range of activation, and are further described by their kinetic and pharmacological properties.
GABA Triggers a [Ca2+]i Increase in Murine Precursor Cells of the Oligodendrocyte Lineage
Authors: Kirchhoff Frank , Kettenmann Helmut 
Published: April 2006

AbstractThe development of oligodendrocytes from their precursor cells can be studied in vitro by using a culture system in which cells can be identified at different developmental stages. We used this culture system to compare the effect of the inhibitory neurotransmitter γ‐aminobutyric acid (GABA) on intracellular Ca2+ concentration ([Ca2+]i) using fura‐2 fluorescence systems. Application of GABA evoked transient [Ca2+]i increases in precursor cells. In contrast, [Ca2+]i levels were not affected in oligodendrocytes, which were identified by their positive labelling with the antibody O1. The precursor cells, identified by a lack of O1 staining, responded to GABA in the concentration range between 10−6 and 10−4 M. Since muscimol mimicked and bicuculline as well as picrotoxin blocked the GABA response, we conclude that the response is mediated by activation of GABAA receptors. The involvement of Ca2+ channels is inferred from the observation that the [Ca2+]i changes could be blocked by nifedipine or by omitting Ca2+ from the bath solution. Both GABAA receptors and Ca2+ channels have been previously identified on these precursor cells with the aid of the patch‐clamp technique. We thus propose the following mechanism to explain our observations: the Cl− efflux via the GABA receptor depolarizes precursor cells, and this depolarization leads to activation of Ca2+ channels, resulting in an influx of Ca2+ and the observed rise in cytosolic [Ca2+]. Although its physiological importance is speculative, this event could serve as a signal from GABAergic neurons to glial precursor cells.
Simultaneous Demonstration of Serotonin‐immunoreactive Terminals and GABAergic Neurons in the VPL Nucleus of the Cat Thalamus
Authors: Liu X.‐B. , Jones E. G. 
Published: April 2006

AbstractPre‐embedding immunoperoxidase (for serotonin) and postembedding immunogold (for γ‐aminobutyric acid; GABA) labelling were combined at light and electron microscopic levels to demonstrate the neuronal targets of serotonin (5‐HT) afferents in the ventral posterior lateral nucleus (VPL) of the cat thalamus. 5‐HT‐immunoreactive fibres and terminal varicosities were found in close proximity to GABA‐immunoreactive interneurons and non‐GABAergic relay neurons. Ultrastructurally, the vast majority of 5‐HT terminals made close membrane contacts without overt membrane specializations with GABAergic axon terminals, GABAergic presynaptic dendrites and GABAergic somata. A very small number of 5‐HT terminals formed typical asymmetrical synapses with GABAergic presynaptic dendrites and with dendritic shafts of relay cells. Some 5‐HT terminals participated with the presynaptic dendrites in triadic synaptic arrangements. These findings suggest a dual innervation pattern by 5‐HT afferents in VPL and the release of 5‐HT in large part at sites not associated with morphologically detectable synapses.
Evidence for a Slowly Inactivating K+ Current in Prefrontal Cortical Cells
Authors: Hammond C. , Crépel F. 
Published: April 2006

AbstractThe in vitro slice preparation of rat prefrontal cortical cells was used to analyse the presence and characteristics of a slowly inactivating outward current and its effect on the delayed integration of synaptic inputs. Pyramidal cells were identified as regular firing or bursting cells. In a fraction of these cells a depolarizing current pulse to –40 mV from a holding potential of –95 mV evoked the fast outward IA current followed by a slower outward current (IKs) which inactivated slowly during the 3‐s pulse. This slowly inactivating outward current was completely inactivated at holding potentials near –40 mV and was fully deinactivated by large hyperpolarizing pulses of 1 s duration. It was sensitive to micromolar concentrations of 4‐aminopyridine and to 10 mM tetraethylammonium. In current clamp experiments, when the cells were maintained at –80 mV, they responded to subliminal depolarizing current pulses by a slow rising depolarization which reached threshold for spike firing after a delay of several seconds. This delay was considerably reduced either by maintaining the cell at less hyperpolarized potentials or by bath application of 40 μM 4‐aminopyridine, or by repeated application of depolarizing pulses. The inactivation of IKs by the last procedure also led to plateau depolarization of the cell. These results suggest that the activation of the slowly inactivating outward current IKs can shunt excitatory inputs, preventing the cell from reaching spike threshold as long as it is not largely inactivated.