bluuebunny/crossref_metadata_2025_split huggingface dataset:
The mechanism of Ara‐C‐induced apoptosis of differentiating cerebellar granule neurons
Authors: Courtney Michael J. , Coffey Eleanor T. 
Published: March 2003

AbstractNeurotoxicity is one of the side‐effects of the therapeutically useful antitumour agent, Ara‐C (or 1‐beta‐d‐arabinofuranosyl‐cytosine, cytarabine). This agent is also reported to induce cell death of cultured neurons. In this study, we show that Ara‐C‐induced death of differentiating rat cerebellar granule neurons is prevented by cycloheximide at concentrations corresponding to its action in preventing protein synthesis. The death is accompanied by cleavage of the caspase substrate poly ADP ribose polymerase (PARP) and c‐Abl‐dependent activation of the stress‐activated protein kinases c‐Jun N‐terminal kinase and p38. However, c‐Jun levels do not rise and the activation of the stress‐activated protein kinases is not required for this form of neuronal death. Cyclin‐dependent kinase (cdk) activity and inappropriate cell‐cycle re‐entry have been implicated in some forms of death in differentiated neurons. Here we show that Ara‐C‐induced death of cerebellar granule neurons is prevented by an inhibitor of cdk4, whereas inhibition of cdk1, −2 and −5 mimics the death, and non‐cdk4/6 cdks are inhibited by Ara‐C treatment. Cdk1 and −2 are dramatically down‐regulated during neuronal differentiation, and neither Ara‐C nor inhibition of these cdks induces death in mature neurons. This mechanism could also play a significant role in the neurotoxicity associated with the therapeutic use of Ara‐C, as cdk levels can be upregulated in stressed neurons of adult brain. We propose that the balance between cdk4/6 and cdk1/2/5 activity may determine the survival of early differentiating neurons, and that DNA‐damaging agents may induce neuronal death by inhibiting cdk1/2/5 under conditions which require these activities for survival.
The interaction between F3 immunoglobulin domains and protein tyrosine phosphatases ζ/β triggers bidirectional signalling between neurons and glial cells
Authors: Revest Jean‐Michel , Faivre‐Sarrailh Catherine , Maeda Nobuaki , Noda Masaharu , Schachner Melitta , Rougon Geneviève 
Published: March 2003

AbstractF3, a mouse glycosyl‐phosphatidylinositol anchored molecule of the immunoglobulin superfamily, is known to influence axonal growth and fasciculation via multiple interactions of its modular immunoglobulin‐like domains. We prepared an Fc chimeric molecule (F3IgFc) to identify molecules interacting with these domains and characterize the functional impact of the interactions. We affinity‐isolated tenascin‐C and isoforms of the proteoglycan‐type protein tyrosine phosphatases ζ/β (PTPζ/RPTPβ) from extracts of developing mouse brain. We showed that both PTPζ/RPTPβ and tenascin‐C can bind directly to F3, possibly in an exclusive manner, with the highest affinity for the F3–PTPζ/RPTPβ interaction. We observed a strong binding of F3IgFc‐coated fluorospheres to astrocytes in neural primary cultures and to C6 astrocytoma cells, and demonstrated, in antibody perturbation experiments, that F3‐Ig binding on astrocytes depends on its interaction with PTPζ/RPTPβ. We also found by confocal analysis that tenascin‐C and PTPζ/RPTPβ were colocalized on astrocytes which suggests a complex interplay of interactions between PTPζ/RPTPβ, tenascin‐C and F3. We showed that the interaction between PTPζ/RPTPβ and F3‐Ig‐like domains can trigger bidirectional signalling. C6 glia‐expressed PTPζ/RPTPβ stimulated neurite outgrowth by cortical and cerebellar neurons, whereas preclustered F3IgFc specifically modified the distribution of phosphotyrosine labelling in these glial cells. Both effects could be prevented and/or mimicked by anti‐F3 and anti‐6B4PG antibodies. These results identify F3 and PTPζ/RPTPβ as potential mediators of a reciprocal exchange of information between glia and neurons.
Activation of reward circuitry in human opiate addicts
Authors: Sell L. A. , Morris J. , Bearn J. , Frackowiak R. S. J. , Friston K. J. , Dolan R. J. 
Published: March 2003

AbstractThe neurobiological mechanisms of opiate addictive behaviour in humans are unknown. A proposed model of addiction implicates ascending brainstem neuromodulatory systems, particularly dopamine. Using functional neuroimaging, we assessed the neural response to heroin and heroin‐related cues in established opiate addicts. We show that the effect of both heroin and heroin‐related visual cues are maximally expressed in the sites of origin of ascending midbrain neuromodulatory systems. These context‐specific midbrain activations predict responses to salient visual cues in cortical and subcortical regions implicated in reward‐related behaviour. These findings implicate common neurobiological processes underlying drug and drug‐cue‐related effects.
Selective up‐regulation of P‐ and R‐type Ca2+ channels in rat embryo motoneurons by BDNF
Authors: Baldelli Pietro , Magnelli Valeria , Carbone Emilio 
Published: March 2003

AbstractCultured spinal cord motoneurons from day 15 rat embryos (E15) represent a useful model to study Ca2+ channel diversities and their regulation by neurotrophins. Besides the previously identified L‐, N‐ and P‐type channels, E15 rat motoneurons also express high densities of R‐type channels. We have previously shown that the P‐type channel is nearly absent in 60% of these cells, while the R‐type contributes to ≈ 35% of the total current. Here, we show that chronic preincubation of cultured rat motoneurons with high concentrations (20–100 ng/mL) of brain‐derived neurotrophic factor (BDNF) caused a selective up‐regulation of the P‐ and R‐type current density available after blocking N‐ and L‐type channels, with no changes to cell membrane capacitance. N‐ and L‐type channels were either not affected or slightly down‐modulated by the neurotrophin. The onset of BDNF up‐regulation of P/R‐type currents had a half‐time of 12 h and reached maximal values of ≈ 80%. High concentrations of nerve growth factor (NGF; 50–100 ng/mL) had no effect on P/R currents, while BDNF action was prevented by the kinase inhibitor K252a and by the protein synthesis inhibitor anisomycin. These results suggest that chronic applications of BDNF selectively up‐regulates the Ca2+ channel types which are most likely to be involved in the control of neurotransmitter release in mammalian neuromuscular junctions. The signal transduction mechanism is probably mediated by TrkB receptors and involves the synthesis of newly functionally active P‐ and R‐type channels. Our data furnish a rationale for a number of recent observations in other laboratories, in which prolonged applications of neurotrophins were shown to potentiate the presynaptic response in developing synapses.
Direct comparison of projections from the central amygdaloid region and nucleus accumbens shell
Authors: Zahm Daniel S. , Jensen Sarah L. , Williams Evelyn S. , Martin John R. 
Published: March 2003

AbstractCertain neurochemical and connectional characteristics common to extended amygdala and the nucleus accumbens shell suggest that the two represent a single functional–anatomical continuum. If this is so, it follows that the outputs of the two structures should be substantially similar. To address this, projections from the caudomedial shell and central nucleus of the amygdala, a key extended amygdala structure, were demonstrated in Sprague–Dawley rats with different anterograde axonal tracers processed separately to exhibit distinguishable brown and blue–black precipitates. The caudomedial shell projection is strong in the ventral pallidum and along the medial forebrain bundle through the lateral preopticohypothalamic continuum into the ventral tegmental area, distal to which it thins abruptly. The central nucleus projects strongly to the bed nucleus of the stria terminalis and the sublenticular extended amygdala, but substantially to the lateral hypothalamus only at levels behind the rostral part of the entopeduncular nucleus. Innervation of the ventral tegmental area by the central amygdala is minimal, but the lateral one‐third of the substantia nigra, pars compacta and an adjacent lateral part of the retrorubral field receive substantial central amygdala input. Central amygdaloid projections are robust in caudal brainstem sites, such as the reticular formation, parabrachial nucleus, nucleus of the solitary tract and dorsal vagal complex, all of which receive little input from the accumbens. The substantial differences in the output systems of the caudomedial shell of accumbens and central amygdala suggest that the two represent distinct functional–anatomical systems.
Functional heterogeneity in dopamine release and in the expression of Fos‐like proteins within the rat striatal complex
Authors: Barrot Michel , Marinelli Michela , Abrous Djoher Nora , Rougé‐Pont Françoise , Le Moal Michel , Piazza Pier Vincenzo 
Published: March 2003

AbstractThe dorsolateral striatum, and the core and shell of the nucleus accumbens are three major anatomical regions of the striatal complex. The shell is considered as a part of the extended amygdala, and is involved in the control of motivation and reward. The core and the striatum are considered central to sensory motor integration. In this study we compared the responses of these three regions to mild stress and drugs of abuse by measuring extracellular dopamine (DA) concentrations and Fos‐like immunoreactivity (Fos‐LI). The results are summarrized as follows. (i) In unchallenged conditions, extracellular DA concentrations were highest in the dorsolateral striatum and lowest in the core, whereas Fos‐LI was highest in the shell and lowest in the dorsolateral striatum. (ii) After challenges that increase DA by depolarizing DAergic neurons (injection stress or 2 mg/kg morphine), the shell presented the largest increase in DA levels and Fos‐LI. (iii) After the administration of a DA‐uptake blocker (15 mg/kg cocaine), the percentage increase in DA was still largest in the shell. However, the absolute increase in DA and Fos‐LI in the shell and the dorsolateral striatum were similar. (iv) After a full D1 agonist (SKF82958), Fos‐LI was highest in the shell and lowest in the dorsolateral striatum. In conclusion, the nucleus accumbens shell seems to be the area of the striatal complex most functionally reactive to stress and drugs of abuse. However, the dorsolateral striatum and the core appear functionally distinct, as for most of the parameters studied these two regions differed.
N‐cadherin expression in endothelial cells during early angiogenesis in the eye and brain of the chicken: relation to blood–retina and blood–brain barrier development*
Authors: Gerhardt H. , Liebner S. , Redies C. , Wolburg H. 
Published: March 2003

AbstractThe factors responsible for the induction and maintenance of blood–brain barrier properties are still undefined. The process of blood–brain barrier formation is thought to take place in a two‐stage manner: the initial commitment of vascular sprouts by neuroectodermal cells may be followed by the stabilization of barrier properties. In the present study, we investigated the expression pattern of neural (N)‐cadherin during early angiogenesis in the brain and the pecten oculi of the chicken. The pecten has been introduced previously as a model for the investigation of the formation and maturation of barrier properties in the central nervous system. Whereas perineural and choroid vessels remained immunonegative for N‐cadherin, vascular sprouts invading both the brain and the pecten primordium acquired anti‐N‐cadherin immunoreactivity. Confocal laser scanning and immunoelectron microscopy indicated that the antigen was located at the ablumenal endothelial membrane in contact with subendothelial cells. With the onset of barrier differentiation as determined by junctional restriction of the tight junction protein occludin, N‐cadherin labelling rapidly decreased. Specific intraneuroectodermal upregulation and decline of endothelial N‐cadherin was confirmed by in situ hybridization and suggests that N‐cadherin expression by cerebral and pecteneal endothelial cells represents an initial and transient signal which may be involved in the commitment of early blood vessels to express blood–brain and blood–retina barrier properties.
Incorporation of a gephyrin‐binding motif targets NMDA receptors to gephyrin‐rich domains in HEK 293 cells
Authors: Kins Stefan , Kuhse Jochen , Laube Bodo , Betz Heinrich , Kirsch Joachim 
Published: March 2003

AbstractThe peripheral membrane protein gephyrin is essential for the postsynaptic localization of inhibitory glycine receptors (GlyRs). Binding of gephyrin to the GlyR β subunit is mediated by a sequence motif located in the intracellular loop region connecting transmembrane segments 3 and 4. Here, insertion of this binding motif is shown to alter the subcellular distribution of an excitatory neurotransmitter receptor in transfected mammalian cells. Upon coexpression with gephyrin, a mutant N‐methyl‐d‐aspartate (NMDA) receptor containing NMDA receptor 1 (NR1) subunits which harboured a gephyrin‐binding motif within its cytoplasmic tail region, was targeted to intracellular gephyrin‐rich domains, as previously observed for the GlyR β subunit. Our data indicate that a gephyrin‐binding motif located in a cytoplasmic domain of an integral membrane protein suffices for routing to gephyrin‐rich domains.
Excitatory synaptic inputs to pyramidal neurons of the lateral amygdala
Authors: Mahanty Nishith K. , Sah Pankaj 
Published: March 2003

AbstractWhole‐cell patch clamp recordings were made from pyramidal neurons in the rat lateral amygdala (LA). Synaptic currents were evoked by stimulating in either the external capsule (ec), internal capsule (ic) or basolateral nucleus (BLA). Stimulation of either the ic, ec or BLA evoked a glutamatergic excitatory synaptic current (EPSC) which was mediated by both non‐NMDA and NMDA (N‐methyl‐d‐aspartic acid) receptors. The ratio of the amplitude of the NMDA receptor‐mediated component measured at +40 mV to the amplitude of the α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) component measured at −60 mV was similar regardless of whether EPSCs were evoked in the ec, ic or BLA. At resting membrane potentials, excitatory synaptic potentials evoked from either the ec or putative thalamic inputs were unaffected by application of the NMDA receptor antagonist APV. Spontaneous glutamatergic currents had two components to their decay phase. The slow component was selectively blocked by the NMDA receptor antagonist D‐APV, indicating that AMPA and NMDA receptors are colocalized in spiny neurons. We conclude that pyramidal cells of the LA receive convergent inputs from the cortex, thalamus and basal nuclei. At all inputs, both AMPA/kainate and NMDA‐type receptors are active and colocalized in the postsynaptic density.
Androgen treatment of neonatal rats decreases susceptibility of cerebellar granule neurons to oxidative stress in vitro
Authors: Ahlbom E. , Grandison L. , Bonfoco E. , Zhivotovsky B. , Ceccatelli S. 
Published: March 2003

AbstractOxidative stress has been implicated in various neurodegenerative diseases. There is substantial evidence indicating that gonadal hormones can affect neuronal cell survival via both a genomic as well as a non‐genomic mode of action. In the present study, the potential protective activity of testosterone on neuronal cells was investigated by using an in vitro/ex vivo model. Cerebellar granule cells (CGC) were prepared from 7‐day‐old rats which had been treated with a single dose of oil or testosterone propionate on postnatal day 3. After 7 days in culture, cells were exposed to oxidative challenges, including hydrogen peroxide and the nitric oxide donor S‐nitrosocysteine (SNOC), which can induce CGC death via apoptosis. Colchicine, which causes apoptosis via a different mechanism, was also used. The cells were monitored for apoptotic morphology by propidium iodide and TUNEL staining. Additionally, the presence of chromatin fragmentation was determined. CGC obtained from testosterone‐treated rats were found to be more resistant to hydrogen peroxide and nitric oxide toxicity, as shown by a 75 and 45% decrease in apoptotic cells, respectively. In contrast, the susceptibility to colchicine was not modified. As CGC from testosterone‐treated pups were selectively protected from oxidative stress, different components of the antioxidant defence systems were analysed. A twofold increase in the activity of catalase and superoxide dismutase was found in the CGC prepared from testosterone‐treated rats. These results suggest that in vivo treatment with androgens render CGC less vulnerable to oxidative stress‐induced apoptosis by potentiating antioxidant defences.
Categorization of complex visual images by rhesus monkeys. Part 1: behavioural study
Authors: Vogels Rufin 
Published: March 2003

AbstractIn order to study how visual categories are coded by the activities of single neurons, it is necessary to first demonstrate that the animal subjects can categorize the visual stimuli employed in the single‐unit recordings. Thus, rhesus monkeys were trained in a visual categorization task designed to minimize rote learning of individual exemplars and to allow testing of transfer from old to novel exemplars of the category. The stimuli were presented during controlled fixation. The monkeys learned to distinguish complex colour images of trees from other objects and generalized from old to novel exemplars. An extensive series of tests with probe stimuli showed that simple form, colour and texture features had insufficient stimulus control to account for the categorization performance. Scrambling the images impaired categorization performance, suggesting that the configuration of stimulus components controlled the categorization. The animals also learned a fish/non‐fish categorization, but more slowly than a tree/non‐tree categorization. These results indicate that rhesus monkeys can learn to categorize socially neutral, complex, natural visual images and suggest that this categorization is based on a combination of low‐level features.
Categorization of complex visual images by rhesus monkeys. Part 2: single‐cell study
Authors: Vogels Rufin 
Published: March 2003

AbstractIn order to investigate the neural coding of ordinate‐level visual categories, single‐cell recordings were made in the anterior temporal cortex of two rhesus monkeys performing a categorization of colour images of trees versus images of other objects. Neurons showed a high average degree of selectivity for these complex colour images. Although most neurons responded to trees and non‐trees, about a quarter responded in a category‐specific manner, e.g. to trees but not non‐trees, and about one‐tenth responded almost exclusively to exemplars of the trained category. The responses of these neurons were largely invariant for stimulus transformations, e.g. changes in position or size, and decreased with the degree of image scrambling, mimicking the behavioural results. However, the responses of single neurons were insufficiently stimulus invariant to accommodate the entire range of variability present in the features of exemplars within the same category. This strong within‐category selectivity challenges the idea that a prototype is represented at the single neuron level, but suggests that ordinate‐level categorization is based on a population of neurons, each selective for a limited set of exemplars.
Effects of excitotoxic lesions of the rat prefrontal cortex on CREB regulation and presynaptic markers of dopamine and amino acid function in the nucleus accumbens
Authors: Dalley J. W. , Thomas K. L. , Howes S. R. , Tsai T. H. , Aparicio‐Legarza M. I. , Reynolds G. P. , Everitt B. J. , Robbins T. W. 
Published: March 2003

AbstractThe present study investigated the effects of excitotoxic lesions of the prefrontal cortex (PFC) on dopamine (DA) and excitatory amino acid (EAA) function in the nucleus accumbens core using in vivo microdialysis in freely moving rats. As a postsynaptic marker of neuronal function, the nuclear levels of the transcriptional factor CREB and its active phosphorylated form, CREB‐P, were measured in the ventral tegmental area (VTA), and in the core and shell subregions of the nucleus accumbens of sham and lesioned animals. PFC‐lesioned animals exhibited a greater locomotor response to novelty and amphetamine administration (125–500 μg/kg i.v.). No change was observed in extracellular levels of glutamate or saturable d‐aspartate binding (a marker for the high‐affinity EAA transporter) in the nucleus accumbens of PFC‐lesioned animals. Extracellular levels of DA were comparable in sham and lesioned animals under tonic conditions, however, following amphetamine administration, DA efflux was significantly attenuated in lesioned animals. No correlation was observed between microdialysate levels of amino acids and the attenuated dopaminergic response to amphetamine in lesioned animals. Further, no effect of the lesion was found on nuclear CREB protein in saline‐ and amphetamine‐treated rats. The density of CREB‐P immunoreactive nuclei, while remaining unchanged in the VTA, increased in the nucleus accumbens shell following amphetamine treatment in lesioned animals. The results show that an important modulatory role of the PFC on the behavioural response to novelty and amphetamine is associated with the level of immediate‐early gene regulation rather than levels of extracellular DA and amino acids in the ventral striatum.
Clusters of GABAA receptors on cultured hippocampal cells correlate only partially with functional synapses
Authors: Kannenberg Kai , Sieghart Werner , Reuter Harald 
Published: March 2003

AbstractWe describe a method to label γ‐aminobutyric acid (GABA)A receptors on the surface of living hippocampal neurons in primary culture, and we compare the distribution of receptors with that of active synapses. To visualize GABAA receptors, the affinity‐purified antibody β3(1–13), recognizing the extracellular N‐termini of the GABAA receptor β2‐ and β3‐subunits, was used in combination with fluorescent secondary antibodies. The β2‐ and β3‐subunits belong to the predominant GABAA receptor subunits in the hippocampus. As expected for aggregates of GABAA receptors in the somato‐dendritic plasma membrane, a patchy staining pattern similar to that seen by labelling neurons after fixation was obtained. An antiserum recognizing an intracellular epitope of GABAA receptor β3‐subunits did not label the receptors in living neurons. Whole‐cell recordings of GABA‐evoked Cl – currents were not affected after decorating GABAA receptors with antibody β3(1–13). Combining the staining of GABAA receptors with the labelling of active presynaptic terminals with the fluorescent dyes FM1‐43 or FM4‐64, consistently resulted in the detection of GABAA receptor clusters that were not located at active synapses. These amounted to ≈ 50% of all labelled GABAA receptor clusters. GABAA receptor clusters that were not associated with active presynaptic terminals partially colocalized with the synaptic vesicle marker protein sv2, while another fraction had no presynaptic counterpart at all. These findings suggest the presence of presynaptically silent GABAergic synapses in cultured hippocampal neurons. They also indicate that for the maintenance of GABAA receptor aggregates, the release of GABA from an opposing active terminal is not essential.