bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pattern Formation in the Mammalian Forebrain: Striatal Patch and Matrix Neurons Intermix Prior to Compartment Formation
Authors: Krushel Leslie A. , Fishell Gord , van der Kooy Derek 
Published: April 2006

AbstractThe striatum of the mammalian forebrain is divided into two compartments: the patches and the matrix. Neurons of the patch compartment in the rat striatum become postmitotic earlier in neurogenesis than neurons of the matrix compartment. The selective adhesion of patch neurons to one another has been suggested previously to be an important developmental mechanism of striatal compartmentation. We asked if the selective adhesion of patch neurons is expressed before or after the migration of the majority of the matrix neurons into the striatum. Patch neurons were labelled in vivo by a fluorescent retrograde tracer injected into the substantia nigra on embryonic day 19, which almost exclusively labelled patch neurons. Matrix neurons were labelled with a maternal injection of bromodeoxyuridine at embryonic day 18. When animals were killed at embryonic day 20, the majority of the retrogradely labelled patch neurons were intermixed with the bromodeoxyuridine‐labelled matrix neurons, although there appeared to be clustering of some of the patch neurons. However, by postnatal day 2 there was a complete segregation of the clusters of the retrogradely labelled patch neurons from the bromodeoxyuridine‐labelled matrix neurons in the striatum. This process was modelled in vitro. The patch and matrix compartments were labelled in vivo at embryonic day 13 and 18 respectively, with different birthdate markers ([3H]thymidine or bromodeoxyuridine). At embryonic day 20 the striatal tissue was removed, dissociated and reaggregated in suspension cultures. After 1 day in vitro, labelled patch and matrix neurons were randomly intermixed within the reaggregates. Examination of the cultures at 2.5 and 4 days in vitro revealed clumping of the labelled patch neurons towards the centres of the reaggregates. Over this same period, the labelled matrix neurons did not clump and were dispersed towards the periphery of the reaggregates. The results suggest that patch neuron adhesiveness may appear relatively soon after these neurons become postmitotic, but that this adhesiveness is unable to overcome the initial force produced by the massive migration of matrix neurons into the striatum. We hypothesize that a migratory phase of embryonic striatal development exists, when fated patch and matrix neurons intermix. After this migratory phase, patch neuron adhesiveness can produce the mature segregation of the striatal compartments.
Desensitization of AMPA Receptors Limits the Amplitude of EPSPs and the Excitability of Motoneurons of the Rat Isolated Spinal Cord
Authors: Ballerini Laura , Bracci Enrico , Nistri Andrea 
Published: April 2006

AbstractIntracellular recording was used to study the effect of cyclothiazide, a selective blocker of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA) receptor desensitization, on lumbar motoneurons of the rat isolated spinal cord. Cyclothiazide (25 μM) enhanced the responses to AMPA in a tetrodotoxin‐insensitive fashion, without affecting those produced by N‐methyl‐D‐aspartate or γ‐aminobutyric acid. Excitatory postsynaptic potentials (EPSPs) evoked by dorsal root stimulation were strongly potentiated in amplitude while paired‐pulse depression (produced by applying pairs of pulses at 2 s interval) of the EPSP was decreased. In the presence of cyclothiazide the frequency of spontaneous synaptic events was greatly increased and network‐driven bursting activity developed with eventual loss of electrical excitability. The present results suggest that pharmacological block of AMPA receptor desensitization led to strong excitation of motoneurons and indicate a physiological role of desensitization in protecting these nerve cells from overactivity.
Lines of Murine Oligodendroglial Precursor Cells Immortalized by an Activated neu Tyrosine Kinase Show Distinct Degrees of Interaction with Axons In Vitro and In Vivo
Authors: Jung M. , Krämer E. , Grzenkowski M. , Tang K. , Blakemore W. , Aguzzi A. , Khazaie K. , Chlichlia K. , von Blankenfeld G. , Kettenmann H. , Trotter J. 
Published: April 2006

AbstractReplication‐defective retroviruses expressing the t‐neu oncogene, or a hybrid protein with the neu tyrosine kinase linked to the external region of the human epidermal growth factor receptor (egfr‐neu), were used to establish lines of murine oligodendroglial precursor cells. Differentiation of the t‐neu lines into myelin‐associated glycoprotein (MAG)‐positive oligodendrocytes was induced by dibutyryl cAMP, and the egfr‐neu line showed limited differentiation in vitro upon withdrawal of epidermal growth factor. Cerebellar granule cell neurons expressed mitogens for the cell lines. Upon transplantation into demyelinated lesions, t‐neu line cells engaged with the demyelinated axons whereas the egfr‐neu line cells differentiated further and ensheathed the axons. These cell lines thus interact with neurons in vitro and in vivo and can be used as tools to define the molecules involved in different stages of neuron‐glia interaction.
Role of Bcl‐2 in the Brain‐derived Neurotrophic Factor Survival Response
Authors: Allsopp Timothy E. , Kiselev Sergei , Wyatt Sean , Davies Alun M. 
Published: April 2006

AbstractDeveloping neurons die if they fail to obtain an adequate supply of neurotrophins from their targets but how neurotrophins suppress cell death is not known. Although over‐expression of exogenous Bcl‐2 can prevent the death of cultured neurons deprived of members of the nerve growth factor family of neurotrophins it is not known if this effect is physiologically relevant. To determine if Bcl‐2 participates in the neurotrophin survival response we used antisense bcl‐2 RNA to inhibit endogenous Bcl‐2 expression. Here we show that brain‐derived neurotrophic factor (BDNF)‐dependent neurons are killed by antisense bcl‐2 RNA in the presence of BDNF. However, when these neurons were supported with ciliary neurotrophic factor (CNTF) their survival was not affected by antisense bcl‐2 RNA. Likewise, the survival of CNTF‐dependent ciliary neurons was not affected by antisense bcl‐2 RNA. Our findings suggest that Bcl‐2 is required for the BDNF survival response and that alternative, Bcl‐2‐independent survival mechanisms operate in sensory and parasympathetic neurons exposed to CNTF.
Decrease of zif‐268 and c‐fos and Increase of c‐jun mRNA in the Cat Areas 17, 18 and 19 Following Complete Visual Deafferentation
Authors: Zhang Fan , Vanduffel Wim , Schiffmann Serge N. , Mailleux Pierre , Arckens Lutgarde , Vandesande Frans , Orban Guy A. , Vanderhaeghen Jean‐Jacques 
Published: April 2006

AbstractWe used in situ hybridization to investigate the effect of complete visual deafferentation on immediate early gene expression in adult cat visual cortex. Deafferentation was obtained by unilateral section of the optic tract and sections of both the corpus callosum and anterior commissure. In this model, one hemisphere served as control for the other within the same animal. A decrease in zinc finger protein (zif)‐268 and c‐fos mRNA was observed in the superficial and deep layers of areas 17 and 18, and all layers of area 19 in the deafferented hemisphere. This decrease, present 3 days after surgery, was maximal after 30 days. An increase of c‐jun mRNA was observed in the deep layers of areas 17, 18 and 19 in the deafferented hemisphere 3, 10 and 30 days after surgery. These results suggest that visual input activates zif‐268 and c‐fos expression and tonically depresses c‐jun expression in the primary visual complex yielding similar levels of c‐jun and c‐fos expression in normal conditions.
Polymer Encapsulated Cell Lines Genetically Engineered to Release Ciliary Neurotrophic Factor Can Slow Down Progressive Motor Neuronopathy in the Mouse
Authors: Sagot Y. , Tan S. A. , Baetge E. , Schmalbruch H. , Kato A. C. , Aebischer P. 
Published: April 2006

AbstractCiliary neurotrophic factor (CNTF) has recently generated great interest due to its potential as a therapeutic agent for the treatment of human neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). Because the systemic half‐life of CNTF is only in the order of a few minutes, continuous delivery of this trophic factor could be attractive or even necessary in the therapy of these diseases. One promising technique involves the polymer encapsulation of cells which have been genetically modified to secrete neurotrophic factors. The polymer capsules can be implanted into animals and effect the slow release of the protein for several months. The encapsulation technique immuno‐isolates the foreign cells from host immune cells and at the same time prevents tumour formation by the transplanted cells. In this study, we have used progressive motoneuronopathy (pmn) mice to determine the extent to which encapsulated cell lines secreting CNTF could alter the course of the disease. pmn/pmn homozygotes present severe loss of myelinated motor fibres and a significant reduction of facial motoneuron cell bodies. The mice develop weakness of the hindlimbs and die during the sixth week after birth. We found that CNTF delayed the disease progression by increasing the survival time by 40% and by improving motor function as assessed by three behavioural tests. Moreover, histological counts of the phrenic nerve myelinated axons and facial nucleus motoneurons indicated a significant reduction of motoneuron loss. These results suggest that polymer‐encapsulated cells releasing neurotrophic factors may provide a potential delivery system for treating neurodegenerative diseases such as ALS.
HIV‐1 gp120 Glycoprotein Induces [Ca2+]i Responses not only in Type‐2 but also Type‐1 Astrocytes and Oligodendrocytes of the Rat Cerebellum
Authors: Codazzi Franca , Menegon Andrea , Zacchetti Daniele , Ciardo Alberto , Grohovaz Fabio , Meldolesi Jacopo 
Published: April 2006

AbstractCultures of cerebellar cortex cells were exposed to the HIV‐1 envelope glycoprotein, gp120, and investigated for cytosolic Ca2+ ion concentration ([Ca2+]i) changes by the fura‐2 ratio videoimaging technique while bathed in complete, Na+‐free or Mg2+‐free Krebs‐Ringer media. At the end of the [Ca2+]i experiments the cells were fixed and immunoidentified through the revelation of markers specific for neurons (microtubule associated protein‐2), type‐2 (A2B5) or all (glial fibrillary acidic protein) astrocytes, oligodendrocytes (galactocerebroside) or microglia (F4/80 antibody). In complete medium, rapid biphasic (spike‐plateau) responses induced by gp120 (0.1–1 nM) were observed in a subpopulation of type‐2 astrocytes. In addition, slow but progressive responses were observed in other type‐2 cells and oligodendrocytes, whereas type‐1 astrocytes showed small responses, if any, and granule neurons did not respond at all. Use of Na+‐free medium (a condition that blocked another gp120‐induced response, cytosolic alkalinization) resulted in an increase in [Ca2+]i response that was appreciable not only in type‐2 but also in most type‐1 astrocytes, possibly because of the inhibition of the Na+/Ca2+ exchanger and the ensuing decrease in Ca2+ extrusion. Granule neurons, including those in direct contact with responsive astrocytes, remained unresponsive, even when the experiments were carried out in Mg2+‐free medium supplemented with glycine, a condition that favours activation of the glutamatergic N‐methyl‐D‐aspartate (NMDA) receptor. The results obtained demonstrate that sensitivity to gp120 is a property of not only a few type‐2 astrocytes but of the majority of cerebellar glial cells, which, however, do not respond to the protein with glutamate release, as indicated by the negative results obtained with NMDA‐receptor‐expressing granule neurons. Single glial cell [Ca2+]i increase, the faster and most sensitive effect of gp120 revealed in the brain so far, could be ultimately employed to reveal CD4‐independent transmembrane signalling machanisms of the viral protein that, at the moment, remain almost entirely unknown.
Exposure to gp120 of HIV‐1 Induces an Increased Release of Arachidonic Acid in Rat Primary Neuronal Cell Culture Followed by NMDA Receptor‐mediated Neurotoxicity
Authors: Ushijima Hiroshi , Nishio Osamu , Klöcking Renate , Perovic Sanja , Müller Werner E.G. 
Published: April 2006

AbstractAfter incubation of highly enriched neurons from rat cerebral cortex with the HIV‐1 coat protein gp120 for 18 h, cells showed fragmentation of DNA at internucleosomal linkers followed by NMDA receptor‐mediated neurotoxicity. We report that in response to exposure to gp120 cells react with an increased release of arachidonic acid (AA) via activation of phospholipase A2. This process was not inhibited by NMDA receptor antagonists. To investigate the role of AA on the sensitivity of the NMDA receptor towards its agonist, low concentrations of NMDA were co‐administered with AA. This condition enhanced the NMDA‐mediated cytotoxicity. Administration of mepacrine reduced cytotoxicity caused by gp120. We conclude that gp120 causes an activation of phospholipase A2, resulting in the increased release of AA, which may in turn sensitize the NMDA receptor.
Differential Expression Patterns of Five Acetylcholine Receptor Subunit Genes in Rat Muscle During Development
Authors: Kues W. A. , Sakmann B. , Witzemann V. 
Published: April 2006

AbstractThe spatial and temporal expression patterns of five genes which encode the α‐, β‐, γ‐, δ‐ and ε‐subunits of the nicotinic acetylcholine receptor in skeletal muscle were followed during development in the rat by in situ hybridization analysis. Three major developmental phases, characterized by specific expression patterns, could be distinguished. (i) During myogenic differentiation α‐, β‐, γ‐ and δ‐subunit genes are activated and transcripts are expressed in muscle precursor cells at embryonic day 12 (E12) and during subsequent cell fusion. (ii) Following innervation of myotubes at ˜E15‐E17 the mRNA of the α‐, β‐, γ‐ and δ‐subunit genes accumulate in synaptic and decrease in extrasynaptic fibre regions during early synaptogenesis. The mRNA of the δ‐subunit gene becomes detectable first in subsynaptic nuclei 2–3 days after innervation has occurred. (iii) During postnatal development α‐, β‐ and δ‐ subunit transcript levels are reduced predominantly in extrasynaptic fibre segments and show significant differences in distribution depending on the muscle subtype whereas the γ‐subunit mRNA disappears completely within the first postnatal week in all muscles. In contrast, the γ‐subunit gene is transcribed only in subsynaptic myonuclei throughout development and in the adult muscle.
Physiological and Morphological Heterogeneity of Dentate Gyrus—Hilus Interneurons in the Gerbil Hippocampus In Vivo
Authors: Buckmaster Paul S. , Schwartzkroin Philip A. 
Published: April 2006

AbstractA variety of morphological types of dentate gyrus/hilus interneurons have been described, but little is known about their corresponding physiological characteristics. To address this issue, intracellular responses to current injection and perforant path stimulation were obtained from putative dentate interneurons in anaesthetized adult gerbils. Our sample of interneurons showed heterogeneity in their intrinsic physiological characteristics and spike thresholds to perforant path stimulation, suggesting the existence of distinct physiologically‐defined classes. ‘Fast‐spiking’interneurons had a low threshold to perforant path stimulation, whereas ‘slow‐spiking’interneurons responded with predominantly inhibitory potentials. In several cases, cells were intracellularly labelled with biocytin for visualization. Interneurons with different physiological traits had distinct morphological features. These results confirm that, as in hippocampus proper, morphologically identifiable interneurons in the dentate hilus show electrophysiological features that are likely to reflect functionally specific roles in informational processing.
Flip and Flop Variants of AMPA Receptors in the Rat Lumbar Spinal Cord
Authors: Tölle T. R. , Berthele A. , Zieglgänsberger W. , Seeburg P. H. , Wisden W. 
Published: April 2006

AbstractThe expression of eight messenger RNA splice forms encoding the Flip and Flop variants of AMPA receptor subunits GluR‐A to ‐D in the rat lumbar spinal cord was examined by in situ hybridization using specific oligonucleotides. In the dorsal horn (laminae I, II and III) the predominant mRNA was GluR‐B Flip. Much lower levels of GluR‐A Flip were found in lamina I and in superficial parts of lamina II outer. In the ventral horn, motor neurons expressed mainly GluR‐B Flip, GluR‐C Flip and Flop, and GluR‐D Flip. Serial sectioning through large motor neurons indicated that a given cell contained, for example, both GluR‐C Flip and Flop splice types.
The Neurotrophin Receptors TrkA and TrkB are Inhibitory for Neurite Outgrowth
Authors: Tannahill Lesley , Klein Rüdiger , Schachner Melitta 
Published: April 2006

AbstractTo investigate the possibility that the neurotrophin tyrosine kinase receptors are also recognition molecules by virtue of their immunoglobulin‐like domains, the ability of TrkA and TrkB to influence neurite outgrowth was tested in vitro. Cell monolayers of fibroblasts transfected to express either the TrkA or TrkB receptor reduced neurite outgrowth of phaeochromocytoma PC12 cells by 50–60% when compared to mock transfected fibroblasts or fibroblasts transfected with the epidermal growth factor receptor. Neurite outgrowth from cerebellar neurons was inhibited by 30–40% on these substrates. When a recombinantly expressed fragment of TrkA comprising the two immunoglobulin‐like domains was coated as a substrate in combination with poly‐L‐lysine and laminin, neurite outgrowth was inhibited in a dose‐dependent manner. This inhibition of neurite outgrowth was not mediated via an interaction with laminin as there is no specific binding of the TrkA fragment to laminin. The adhesion of cell bodies to this substrate was not affected by the immunoglobulin‐like domains. These observations suggest that the mammalian neurotrophin receptors not only influence neurite outgrowth by neurotrophin triggered activation of the receptor, but also by cell surface recognition processes conveyed by the immunoglobulin‐like domains.
Target Preference of Embryonic Retina Cells and Retinal Cell Lines is Cell‐autonomous, Position‐specific, Early Determined and Heritable
Authors: Pollerberg G. E. , Eickholt B. J. 
Published: April 2006

AbstractRetinal ganglion cells (RGCs) form the topographic connection between retina and optic tectum in the developing avian embryo. In vitro, neurons with the morphological traits and marker expression of RGCs were found both in single‐cell cultures from embryonic day (E) 6 chick retina and in retinal cell lines derived from E3.5 quail retina. Rapid and substantial differentiation of RGC‐like cells could be induced in the lines by addition of fibroblast growth factor aFGF or bFGF. RGC‐like cells were examined with respect to their target discrimination properties as single cells in the stripe carpet assay. In this assay system, alternating stripes of membrane vesicles prepared from the anterior and posterior tectum are offered to growing axonal processes as a substrate. Temporal RGC‐like cells, both primary cells prepared from the temporal retina and immortalized cells of those retinal lines derived from the temporal retina, avoid stripes of membrane vesicles from posterior tectum; they prefer to grow on membrane vesicles from the anterior tectum, which is their in vivo target. Nasal RGC‐like cells did not exhibit a target preference, in accordance with previous findings. Together the experiments show that target preference of RGCs is a cell‐autonomous and heritable mechanism that is determined early and is position‐dependent.
Behaviour of Small Inhibitory Interneurons in Early Postnatal Mouse Cerebellar Microexplant Cultures: A Video Time‐lapse Analysis
Authors: Magyar‐Lehmann Stefanie , Suter Caterina Savi , Stahel Werner , Schachner Melitta 
Published: April 2006

AbstractThe aim of this work was to investigate how the environment of the neuropil determines the positioning and differentiation of neurons that are postsynaptic to them. We investigated how stellate and basket cells, the small inhibitory interneurons of the cerebellar cortex, find their perpendicular orientation to the direction of fasciculated granule cell axons. Cultures of early postnatal mouse cerebellar microexplants showing this cellular behaviour in vitro were analysed by video time‐lapse cinematography and evaluated by morphometry. The small interneurons were first detectable when they migrated, intermingled with granule cells, away from the explant along the radial fascicles of granule cell neurites. During migration some cells suddenly changed their orientation by extending neurites in perpendicular orientation to the radial fascicles. These cells were all GABA‐immunoreactive and expressed the cytoskeletal markers tau in the thin axon‐like process and MAP2 in the thicker dendrite‐like arborizations at the opposite pole of the cell body. After having translocated in perpendicular orientation, these neurons were again able to turn back to move along the radial neurite bundles to another position. Furthermore, while in perpendicular orientation, the processes of these cells repelled each other upon contact of their growth cones, leading to equal spacing between the cell bodies with time in culture.
Fasciculation of Granule Cell Neurites is Responsible for the Perpendicular Orientation of Small Inhibitory Interneurons in Mouse Cerebellar Microexplant Cultures In Vitro
Authors: Magyar‐Lehmann Stefanie , Frei Thomas , Schachner Melitta 
Published: April 2006

AbstractTo study the cellular and molecular mechanisms involved in the perpendicular orientation of stellate and/or basket cells to the direction of fasciculating granule cell neurites, we have used cultures of microexplants from early postnatal mouse cerebellum that show this cellular behaviour in vitro. When these cultures were maintained in the presence of antibodies to the neural cell adhesion molecules L1 and N‐CAM or immunoglobulin‐like domains I, II and IV of N‐CAM, the resulting decrease or increase in the fasciculation of granule cell neurites changed the perpendicular orientation and morphology of the small inhibitory interneurons. Additives which did not perturb fasciculation did not affect the perpendicular orientation and morphology of stellate and/or basket cells. Furthermore, when perturbation of fasciculation was prevented, neither L1 nor N‐CAM antibodies modified the positioning or morphology of interneurons. These observations indicate that ordered fasciculation of granule cell neurites is an important parameter in the perpendicular orientation and elaboration of the typical morphology of the small cerebellar inhibitory interneurons.