bluuebunny/crossref_metadata_2025_split huggingface dataset:
Brain Spectrins 240/235 and 240/235E: Differential Expression During Development of Chicken Dorsal Root Ganglia in vivo and in vitro
Authors: Barakat‐Walter I. , Reiderer B. M. 
Published: April 2006

AbstractBrain spectrin, a membrane‐related cytoskeletal protein, exists as two isoforms. Brain spectrin 240/235 is localized preferentially in the perikaryon and axon of neuronal cells and brain spectrin 240/235E is found essentially in the neuronal soma and dendrites and in glia (Riederer et al., 1986, J. Cell Biol., 102, 2088–2097). The sensory neurons in dorsal root ganglia, devoid of any dendrites, make a good tool to investigate such differential expression of spectrin isoforms. In this study expression and localization of both brain spectrin isoforms were analysed during early chicken dorsal root ganglia development in vivo and in culture. Both isoforms appeared at embryonic day 6. Brain spectrin 240/235 exhibited a transient increase during embryonic development and was first expressed in ventrolateral neurons. In ganglion cells in situ and in culture this spectrin type showed a somato – axonal distribution pattern. In contrast, brain spectrin 240/235E slightly increased between E6 and E15 and remained practically unchanged. It was localized mainly in smaller neurons of the mediodorsal area as punctate staining in the cytoplasm, was restricted exclusively to the ganglion cell perikarya and was absent from axons both in situ and in culture. This study suggests that brain spectrin 240/235 may contribute towards outgrowth, elongation and maintenance of axonal processes and that brain spectrin 240/235E seems to be exclusively involved in the stabilization of the cytoarchitecture of cell bodies in a selected population of ganglion cells.
Localization and Synaptic Release of N‐acetylaspartyl‐glutamate in the Chick Retina and Optic Tectum
Authors: Williamson Lura C. , Eagles Douglas A. , Brady Meghan J. , Moffett John R. , Namboodiri M. A. Aryan , Neale Joseph H. 
Published: April 2006

AbstractThe neuropeptide, N‐acetylaspartylglutamate (NAAG), was identified in the chick retina (1.4 nmol/retina) by HPLC, radioimmunoassay and immunohistochemistry. This acidic dipeptide was found within retinal ganglion cell bodies and their neurites in the optic fibre layer of the retina. Substantial, but less intense, immunoreactivity was detected in many amacrine‐like cells in the inner nuclear layer and in multiple bands within the inner plexiform layer. In addition, NAAG immunoreactivity was observed in the optic fibre layer and in the neuropil of the superficial layers of the optic tectum, as well as in many cell bodies in the tectum. Using a newly developed, specific and highly sensitive (3 fmol/50 μI) radioimmunoassay for NAAG, peptide release was detected in isolated retinas upon depolarization with 55 mM extracellular potassium. This assay also permitted detection of peptide release from the optic tectum following stimulation of action potentials in retinal ganglion cell axons of the optic tract. Both of these release processes required the presence of extracellular calcium. Electrically stimulated release from the tectum was reversibly blocked by extracellular cadmium. These findings suggest that NAAG serves an extracellular function following depolarization‐induced release from retinal amacrine neurons and from ganglion cell axon endings in the chick optic tectum. These data support the hypothesis that NAAG functions in synaptic communication between neurons in the visual system.
Functional Properties of Neurons in the Anterior Bank of the Parieto‐occipital Sulcus of the Macaque Monkey
Authors: Galletti C. , Battaglini P. P. , Fattori P. 
Published: April 2006

AbstractExtracellular recordings were made in the anterior bank of the parieto‐occipital sulcus of two waking monkeys trained to perform fixation tasks in normal illumination or in complete darkness. Of the recorded neurons, 73% (251/343) were responsive to visual stimulation, but their overall organization did not conform to a simple, continuous retinotopic map. Most of the visual neurons showed a high degree of orientation and direction sensitivity, higher than that found in areas V1, V2 and V3A under the same experimental conditions. Whether they had a resolvable receptive field or not, the discharge rate of many neurons in the anterior bank of the parieto‐occipital sulcus was influenced by oculomotor activity. The animals were required to execute pursuit or saccadic eye movements in darkness. Saccadic eye movements were found to influence 19% of the neurons tested (29/156); by contrast, pursuit eye movements were without effect (0/64). Saccade responses were direction‐tuned and, in several cases, the neuronal discharge started before the onset of eye movement. The animals were also required to gaze, in darkness, at nine different positions on the screen they faced. Of the neurons tested, 59% (102/174) were affected by the direction of gaze. Higher discharge rates were generally observed when the animals looked towards the lower part of the field of view. Given the functional properties of its neurons, its connections with area V3A—where neural signals appropriate for building an objective map of the visual space are present (Galletti and Battaglini, 1989, J. Neurosci., 9, 1112–1125)—and its output to the visuomotor centres involved in the generation of saccades (frontal eye fields and superior colliculus), we infer that the cortex of the anterior bank of the parieto‐occipital sulcus might be part of the network involved in the control of gaze in order to locate objects in visual space.
Somatosensory Discrimination of Shape: Tactile Exploration and Cerebral Activation
Authors: Seitz Rüdiger J. , Roland Per E. , Bohm Christian , Greitz Torgny , Stone‐Elander Sharon 
Published: April 2006

AbstractThis study of somatosensory discrimination of rectangular parallelepipeds with the right hand had three purposes: (i) to describe the exploratory finger movements; (ii) to reveal the anatomical brain structures specifically engaged in the production of exploratory finger movements; and (iii) to reveal the anatomical structures specifically engaged in the discrimination of tactually sensed shape. The thumb was the most active finger, moving with a mean exploration frequency of 2.4 Hz, as evident from videotape records of the exploratory finger movements. The cerebral structures activated during somatosensory discrimination were mapped by measurements of regional cerebral blood flow (rCBF) in six healthy male volunteers with positron emission tomography (PET) and the use of the computerized brain atlas of Greitz et al. (1991, J. Comp. Ass. Tomogr., 15, 26–38). The rCBF changes caused by somatosensory discrimination were compared point‐to‐point to a PET‐study on right‐hand finger movements and a PET‐study on vibration stimulation of the right hand. From these results the following conclusions were drawn. The rCBF increase in the left superior parietal lobule indicated the site engaged in the analysis of shape. The rCBF increases in the left supplementary sensory area, bilaterally in premotor areas, in the left putamen, the right dentate nucleus and bilaterally in the posterior cerebellum were related to the control of the tactile exploratory finger movements. The rCBF increases in the right homologue of Broca's area, bilaterally in the superior prefrontal cortex and in the right midfrontal cortex probably resulted from working memory, the direction of attention, and the discrimination process.
Ultrastructural Relationships Between GABAergic Terminals and Cardiac Vagal Preganglionic Motoneurons and Vagal Afferents in the Cat: A Combined HRP Tracing and Immunogold Labelling Study
Authors: Maqbool Azhar , Batten Trevor F. C. , McWilliam Peter N. 
Published: April 2006

AbstractThe ultrastructural relationships between γ‐aminobutyric acid‐immunoreactive (GABA‐ir) neurons and other neurons of the nucleus tractus solitarius (NTS) and motoneurons of the nucleus ambiguus (NA) and dorsal motor vagal nucleus (DMVN), were examined by electron microscopic (EM) immunogold labelling with an anti‐GABA antiserum on brain stem sections in which vagal motoneurons and vagal afferent fibres were labelled with horseradish peroxidase (HRP). HRP was applied to the cervical vagus or the cardiac vagal branch of anaesthetized cats. After 24–48 h survival, brains were glutaraldehyde‐fixed and a stable HRP‐tetramethylbenzidine reaction product compatible with EM processing was revealed on 250 μm vibratome sections. Following osmium postfixation, dehydration and resin embedding, GABA‐ir was localized on ultrathin sections by an immunogold technique. GABA‐ir axon terminals, heavily and specifically labelled with gold particles, were very numerous within NTS, DMVN and NA. All terminals contained small, clear, pleomorphic vesicles and a few also contained larger dense cored vesicles. The density of gold particles over clear vesicles, dense cored vesicles and mitochondria was significantly greater than over the cytoplasm of these terminals. GABA‐ir synapses were found on the soma and dendrites of neurons, but rarely on other axon terminals within NTS, where GABA‐ir cell bodies and dendrites were also seen. These received synaptic contacts from both GABA‐ir terminals and from HRP‐labelled vagal afferents. In both the DMVN and NA, similar GABA‐ir synapses were present on both the soma and dendrites of HRP‐labelled motoneurons. GABA synapses were also present on other cell types in DMVN. These observations provide an anatomical basis for a GABAergic inhibition of neurons forming the central pathways of cardiovascular and other autonomic reflexes.
Mast Cell Degranulating Peptide Increases the Frequency of Spontaneous Miniature Postsynaptic Currents in CA3 Rat Hippocampal Neurons
Authors: Neuman R. , Ben Ari Y. , Cherubini E. 
Published: April 2006

AbstractMast cell degranulating peptide (MCDP) is a neurotoxic agent isolated from bee venom. It produces a long‐term potentiation in the hippocampus. We now report that MCDP, at nanomolar concentrations, induces a reduction of a transient voltage‐dependent potassium current (ID) in CA3 rat pyramidal neurons and a persistent (>30 min) enhancement of the frequency of spontaneous miniature excitatory and inhibitory postsynaptic currents (m.e.p.s.c.s. and m.i.p.s.c.s.). M.e.p.s.c.s. and m.i.p.s.c.s. were recorded in the presence of bicuculline (30 μM) and 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX, 10 μM), respectively. The increased frequency of m.e.p.s.c.s. (408±60%) and m.i.p.s.c.s. (583±553%) was independent of the reduction of ID because 4‐aminopyridine (4‐AP, 30 μM‐2 mM) blocked ID but had no effects on m.e.p.s.c.s. and m.i.p.s.c.s. In the presence of the calcium channel blocker manganese (3 mM), MCDP still enhanced the frequency of m.e.p.s.c.s. (326±162%). It is concluded that MCDP augments the release of excitatory and inhibitory transmitter by an action, which is independent of calcium influx, through voltage‐dependent channels.
Acidic Amino Acids and Self‐stimulation of the Prefrontal Cortex in the Rat: A Pharmacological Study
Authors: Cobo M. , Mora F. 
Published: April 2006

AbstractThe effects of intraventricular and intracortical microinjections of acidic amino acid antagonists on self‐stimulation (SS) of the medial prefrontal cortex (MPC) were investigated. Self‐stimulation was measured by depressing a lever in a standard chamber. Spontaneous motor activity of the animal and SS of the contralateral non‐injected MPC were used as control for non‐specific effects of the drugs. Intraventricular microinjections of γ‐d‐glutamylglycine (DGG), an antagonist of NMDA, kainate and quisqualate receptors, or 2‐amino‐5‐phosphonovalerate (AP‐5), a specific antagonist of NMDA receptors, produced a dose‐related decrease of SS in the MPC. Spontaneous motor activity of the animal was not significantly affected. Unilateral microinjections into the medial prefrontal cortex of DGG or AP‐5 produced a decrease of SS in the ipsilateral side while no effects were found on the contralateral MPC. On the contrary, intraventricular microinjections of γ‐d‐glutamyltaurine (Glu‐tau), an antagonist with more relative affinity for kainate and quisqualate receptors, produced a dose‐related decrease of both self‐stimulation and spontaneous motor activity of the rats. Moreover, intracortical microinjections of Glu‐tau had no effect on self‐stimulation of this cortical area. These results suggest that acidic amino acids through NMDA, but not kainate or quisqualate, receptors could be part of the neurochemical substrate underlying SS of the MPC in the rat.
Reorganization of the Cytoskeleton in Rat Neurons Following Stimulation With Excitatory Amino Acids In Vitro
Authors: Bigot D. , Matus A. , Hunt S. P. 
Published: April 2006

AbstractThe state of neuronal microtubule polymerization is influenced by microtubule‐associated proteins such as MAP2, which is specifically localized within neuronal dendrites and cell bodies. We have demonstrated that stimulation of spinal cord or cortical neurons in vitro with excitatory amino acids results in a dramatic modification of the neuronal cytoskeleton as monitored with antibodies against MAP2 and tubulin. Stimulation of cultures with glutamate receptor agonists induced a reorganization of MAP2 immunoreactivity into a distinctive network of bundles within certain neuronal cell bodies and their proximal neurites. The effect was not abolished by depolymerizing drugs such as nocodazole, or protein synthesis inhibitors. The effect was dependent upon the entry of sodium following depolarization and was not associated with neuronal damage. We suggest that in neurons the state of the neuronal cytoskeleton can be modulated by glutamate receptor activation acting through MAP2.
Excitatory Connections Between CA1 Pyramidal Cells Revealed by Spike Triggered Averaging in Slices of Rat Hippocampus are Partially NMDA Receptor Mediated
Authors: Thomson Alex M. , Radpour Shahrzad 
Published: April 2006

AbstractSpike triggered averaging was used to record local circuit connections between pairs of CA1 pyramidal neurons in isolated slices of rat hippocampus. Of 795 pairs of neurons tested, six were connected. These epsps were only partially blocked by 2‐amino‐5‐phosphonovalerate (AP‐5), which decreased the amplitude and half width of the epsp, but did not affect the early rising phase. In contrast, 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX) blocked all phases of the epsp and combinations of AP‐5 and CNQX blocked the epsp almost entirely. These results indicate that these epsps were mediated by both N‐methyl‐d‐aspartate (NMDA) and non‐NMDA excitatory amino acid receptors. Moreover, they exhibited a voltage relation typical of neuronal responses to NMDA, increasing in amplitude and duration as the postsynaptic cell was depolarized. These epsps were brief (10–90% rise time < 5 ms, width at half amplitude < 20 ms), indicating a proximal location. Increasing presynaptic firing rate (1–4 spikes/s) reduced average epsp amplitude by almost 50%. When epsps were evoked by pairs of spikes (interval 3–25 ms), a large response to the first spike precluded a large response to the second. No evidence for selective enhancement of the NMDA receptor component by paired spike activation was found. It is concluded that a significant NMDA receptor mediated input to CA1 is provided by local circuit CA1–CA1 connectionsx and that these synapses can be demonstrated under control conditions.
Coactivation of Local Circuit NMDA Receptor Mediated epsps Induces Lasting Enhancement of Minimal Schaffer Collateral epsps in Slices of Rat Hippocampus
Authors: Radpour Shahrzad , Thomson Alex M. 
Published: April 2006

AbstractLasting enhancement of minimal Schaffer collateral epsps in CA1 pyramidal neurons was induced when these epsps were coactivated with putative local circuit N‐methyl‐d‐aspartate (NMDA) receptor‐mediated epsps. In transverse slices of hippocampus, minimal epsps were evoked by stimulating the Schaffer collateral/commissural pathway within CA3 stratum radiatum and the local circuit axons were stimulated within CA1 stratum oriens or alveus using fine, two barrel glass micropipettes. Minimal Schaffer collateral epsps were insensitive to d‐2‐amino‐5‐phosphonovalerate (AP‐5) and displayed conventional voltage relations. Local epsps were sensitive to AP‐5 and increased in amplitude and duration with membrane depolarization. High frequency tetanic stimulation of the minimal Schaffer collateral epsps induced no lasting enhancement. However, pairing of the Schaffer epsp with a frequency potentiated local epsp resulted in a delayed, but lasting increase in the Schaffer epsp. When the local epsp did not exhibit frequency potentiation during pairing, no enhancement resulted. When either epsp was contaminated with an ipsp, no lasting increase resulted. When transmission through the alveus was blocked by focal application of local anaesthetic, traditional protocols for long‐term potentiation (LTP) induction were relatively ineffective. These results indicate that a significant source of the NMDA receptor activation required for the induction of LTP in the Schaffer collateral input to CA1 derives from local circuit connections between CA1 pyramidal neurons and, moreover, that lasting enhancement can be induced with low frequency activation, at postsynaptic resting potential, in the presence of Mg2+ and with local inhibition intact.
Molecular Association of the Neural Adhesion Molecules L1 and N‐CAM in the Surface Membrane of Neuroblastoma Cells is Shown by Chemical Cross‐linking
Authors: Simon Horst , Klinz Stephan , Fahrig Thomas , Schachner Melitta 
Published: April 2006

AbstractThe two neural cell adhesion molecules L1 and N‐CAM could be shown to be associated in the surface membrane of cultured neuroblastoma cells by chemical cross‐linking with 3,3′‐dithiobis(sulphosuccinimidylpropionate) and subsequent immunopurification and precipitation using antibodies to L1 and N‐CAM. Glycoproteins recognized in neuroblastoma cells by antibodies to mouse liver membranes were not chemically cross‐linked to L1 or N‐CAM. These observations suggest that a molecular association between the two molecules may be the basis for their functional cooperativity (Kadmon et al., 1990a, b, J. Cell Biol., 110, 193–208; 209–218).
Auditory Pontine Grey: Connections and Response Properties in the Horseshoe Bat
Authors: Schuller Gerd , Covey Ellen , Casseday John H. 
Published: April 2006

AbstractThis study investigates the role of the pontine grey as a link between the auditory system and the cerebellum in the bat, Rhinolophus rouxi. We recorded response properties of single neurons in the pontine grey and, in the same preparation, injected wheat germ agglutinin ‐ horseradish peroxidase (WGA‐HRP) in areas responsive to sound. Thus the functional evidence was correlated with retrograde and anterograde transport. The main results are: (i) all auditory neurons in the pontine grey are tuned within one of two harmonically related frequency ranges of the echolocation call. The upper range corresponds to the constant frequency and frequency modulated components of the second harmonic, but the lower range corresponds only to the frequency modulated component of the first harmonic. There is no systematic tonotopic organization; (ii) discharge patterns are extremely variable, latencies cover a wide range, and about half of the neurons are binaurally responsive with excitation from both ears; (iii) most pontine auditory neurons respond preferentially to frequency modulated stimuli; (iv) there is massive input to the pontine grey from the central nucleus of the inferior colliculus; (v) cortical input to the pontine grey does not originate in tonotopically organized auditory cortex. The input is from a dorsal belt area that is specialized for processing combinations of sounds with specific frequency ratios and delays; (vi) projections from the auditory region of the pontine grey are widespread within the cerebellar cortex. The data suggest that the pontine grey transmits to the cerebellum information contained in specific components of the bat's biosonar signal.
Modulation of Human Neurite Outgrowth by Serine Proteases: A Comparison of the Interaction of Thrombin and Prothrombin with Glia‐Derived Nexin
Authors: Grabham P. W. , Monard D. , Gallimore P. H. , Grand R. J. A. 
Published: April 2006

AbstractNeurite outgrowth from cells of neuroepithelial origin is under the reciprocal control of thrombin and the thrombin inhibitor‐glia‐derived nexin (GDN). The neurite retraction activity of thrombin is blocked when GDN complexes with the enzyme and inhibits its proteolytic activity. However, we have previously shown that enzymically inactive proenzyme is also capable of inducing neurite retraction. We present evidence here to show that GDN does not bind to prothrombin in solution. When a mixture of prothrombin and GDN is subjected to either polyacrylamide gel electrophoresis or immunoprecipitation, a stable complex cannot be detected. This is in direct contrast to thrombin, which exhibits stable complexes with GDN under both conditions. At the cell surface, however, GDN is able to inhibit the biological activity of prothrombin. When a mixture of proenzyme and inhibitor is applied to previously differentiated transformed retinobiasts (Ad12 HER10), the ability of prothrombin to induce neurite retraction is blocked. Furthermore, following 1 h exposure to Ad12 HER10 cells, a solution of prothrombin was found to contain half the potential enzyme activity as detected by chromogenic assay. These results have been interpreted as evidence for the ability of neuronal cells to cleave prothrombin and subsequently release activated enzyme.
Characterization and Regional Distribution of a Class of Synapses with Highly Concentrated cAMP Binding Sites in the Rat Brain
Authors: Caretta Antonio , Cevolani Daniela , Luppino Giuseppe , Matelli Massimo , Tirindelli Roberto 
Published: April 2006

AbstractA class of putative synaptic terminals with concentrated cAMP binding sites are labelled in unfixed sections of rat brain by means of the ligand 8‐thioacetamido fluorescein cAMP (SAF‐cAMP), a fluorescent analogue of cAMP. The labelled terminals appear as sharply delimited bouton‐like structures in close proximity but external to the cell body of neurons. The SAF‐cAMP binding, measured at equilibrium in competition with other nucleotides, indicates that the binding site recognizes the cAMP moiety of SAF‐cAMP. In the labelled terminals of the frontal cortex the concentration of SAF‐cAMP binding sites is estimated to be in the millimolar range (at least 2.1 ± 1.0 mM). In a brain homogenate, labelled terminals are visualized only in the membrane fraction enriched in synaptosomes. The cAMP binding activity of the synaptosomes is insoluble in high and in low ionic strength solution and is only partially solubilized by detergents, suggesting that the binding sites are intrinsic membrane proteins and/or proteins associated with the cytoskeleton. There is the possibility that SAF‐cAMP labels new cAMP binding sites highly concentrated in a class of synaptic terminals. SAF‐cAMP labelling is prominent in well defined regions of the rat brain: (i) the frontal and entorhinal areas of the cortex; (ii) the field CA1 of the hippocampus; (iii) the olfactory system; (iv) the medial nuclei of the thalamus; (v) the parabrachial nuclei and other less defined regions of the reticular substance; (vi) the substantia gelatinosa of Rolando in the spinal cord; and (vii) the neo‐ and paleocerebellum in the Purkinje cell layer, the archicerebellum in the granular cell layer. SAF‐cAMP labelling is absent in specific motor and sensory structures, with the exception of the olfactory system. It is proposed that SAF‐cAMP binding sites single out a new type of synaptic terminals involved in complex nervous functions.