bluuebunny/crossref_metadata_2025_split huggingface dataset:
Biochemical and Functional Characterization of Basal Lamina‐bound Agrin in the Chick Central Nervous System
Authors: Kröger Stephan , Mann Sabine 
Published: April 2006

AbstractAgrin is a high‐molecular weight extracellular matrix molecule, initially purified from the electric organ of the marine ray Torpedo californica, which induces on the surface of cultured myotubes the formation of postsynaptic specializations similar to those found at the neuromuscular junction. Agrin immunoreactivity is highly concentrated in the basal lamina of the synaptic cleft but is also found in a number of other tissues where its function is not known. We characterized agrin associated with two basal laminae from the central nervous system, the inner limiting membrane of the retina and the mesencephalic external limiting membrane. A major broad band with an apparent molecular weight of <300 kDa was identified in immunoblots of isolated basal laminae from retina, mesencephalon, kidney and muscle, showing that basal lamina‐bound agrin from the central nervous system and that from non‐neural tissues have similar molecular sizes. Agrin is stably but not covalently bound to the inner limiting membrane and could be completely removed only with strong detergents. Agrin could be partially extracted with buffers that are also able to partially release acetylcholine receptor aggregation activity from the neuromuscular junction or from the electric organ. Despite these immunological and biochemical similarities, agrin from both central nervous system‐derived basal laminae was not able to induce acetylcholine receptor aggregation on cultured myotubes. This shows that functionally different agrin isoforms are associated with basal laminae in the central nervous system compared to the neuromuscular junction or the electric organ.
Ciliary Neurotrophic Factor Constitutively Expressed in the Nervous System of Transgenic Mice Protects Embryonic Dorsal Root Ganglion Neurons from Apoptosis
Authors: Tolosano Emanuela , Cutufia Miguel Angel , Hirsch Emilio , Stefanuto Guglielmo , Voyron Samuele , Fasolo Aldo , Silengo Lorenzo , Altruda Fiorella 
Published: April 2006

AbstractCiliary neurotrophic factor (CNTF) is a potent survival factor for several neuronal populations. It is expressed postnatally by Schwann cells in the peripheral nervous system and by some glial and neuronal cells in the central nervous system. We used the promoter of the neurofilament light chain gene to produce transgenic mice that express CNTF in neurons from the beginning of neuronal differentiation. These transgenic animals may represent a suitable model to identify neuronal cell types responsive to CNTF in vivo and to study the mechanism of action of this neurotrophic factor. We show that dorsal root ganglion neurons of transgenic mice expressing CNTF in neurons are protected from apoptosis during embryonic development: 40% of these cells undergo apoptosis between embryonic day 12.5 and postnatal day 5 in transgenic mice whereas 60% do so in control animals. However, protection from apoptosis does not result in an increase in the total number of neurons at the end of development. We discuss our results with regard to CNTF potentialities in vivo and the significance of programmed cell death during development.
A Quantitative Study of Electroencephalography, Eye Movements and Neck Electromyography Characterizing the Sleep—Wake Cycle of the Guinea‐pig
Authors: Escudero M. , Vidal P. P. 
Published: April 2006

AbstractThe qualitative and quantitative characteristics of cerebral cortex electrical activity, ocular motility and muscular activity were studied in six head‐restrained guinea‐pigs during wakefulness, slow‐wave and paradoxical sleep. Animals were chronically implanted with bipolar electrodes in the obliquus capitis muscle for electromyographic recordings and epidurally through the parietal bones for electroencephalographic (EEG) recordings. Eye movements were recorded using the scleral search‐coil technique. After postoperative recovery and a short period of habituation to immobilization, head‐restrained animals exhibited a polyphasic sleep–wake cycle similar to what has already been described in the unrestrained guinea‐pig. Paradoxical sleep periods of mean duration 110 ± 42 s occurred at a mean interval of 32.2 ± 7.2 min. Amplitude and frequency components of EEG activity were different for each state of vigilance. EEG amplitude was highest and frequency range lowest—with two well‐defined peaks at 4 and 10 Hz—during slow‐wave sleep. During paradoxical sleep, frequencies were higher and amplitudes lower than during wakefulness. Three types of eye movement intermingled with periods of ocular fixation were recorded: saccadic movements during wakefulness and paradoxical sleep, slow drifts during slow‐wave sleep and paradoxical sleep, and a new type of eye movement—bursts of high‐velocity eye oscillations during paradoxical sleep. Saccadic eye movements during paradoxical sleep were more frequent and showed higher velocities and amplitudes than during wakefulness. During paradoxical sleep the episodes of eye oscillation (8–14 Hz) occurred quite regularly every 1.6 s and had a mean duration of 1.4 s. During wakefulness, the obliquus muscle activity displayed a burst‐tonic pattern. Bursting components were closely related to saccadic eye movements directed to the side of the recorded muscle. The muscle activity was predominantly tonic during slow‐wave sleep and was completely absent during paradoxical sleep except for small bursts or twitches. These twitches were tightly synchronized with the occurrence of the rapid eye movements oriented towards the side of the recorded obliquus muscle, as during wakefulness. These results strongly suggest that paradoxical sleep is characterized by the oscillatory discharge of at least two neuronal populations: the brainstem saccadic generators and the tecto‐reticular spinal network which underlies gaze‐orienting behaviour during wakefulness. The occurrence of rhythmic discharges at ˜11 Hz may explain the spinal motoneurons’ inhibition during paradoxical sleep in order to avoid anarchic motor behaviour. Whether these neuronal oscillations are simply an epiphenomenon or have functional implications remains to be determined.
Synaptically Activated Low‐threshold Muscarinic Inward Current Sustains Tonic Firing in Rabbit Prevertebral Sympathetic Neurons
Authors: Niel J.‐P. , Delmas P. , Gola M. 
Published: April 2006

AbstractWhole‐cell patch‐clamp experiments were performed on non‐dissociated rabbit coeliac sympathetic neurons in the presence of nicotinic blockers. Coeliac neurons were classified as either silent or spontaneously active (pacemaker) cells. Under voltage‐clamp conditions, pacemaker cells exhibited a steady‐state N‐shaped current‐voltage relationship due to the presence of a persistent voltage‐dependent inward current in the potential range of ‐100 to —20 mV. This inward current sustained the regular firing activity of pacemaker cells and was absent from quiescent neurons. It disappeared in the presence of tetrodotoxin and in low Ca2+‐high Mg2+ external solutions and was enhanced by eserine. Splanchnic nerve stimulation induced slow regenerative depolarizations and firing discharges in silent neurons by activating a low‐threshold voltage‐sensitive inward current. The synaptic current had a U‐shaped voltage‐dependence from —96 to —20 mV and exhibited the dynamic properties of the muscarinic voltage‐dependent inward current lNa, M. It gave the current‐voltage relationship an N shape similar to that observed in spontaneously active cells. The muscarinic antagonists atropine and pirenzepine abolished the inward current present in pacemaker cells and that induced by nerve stimulation in silent neurons. These data provide evidence that both spontaneous firing activity and nerve‐evoked depolarizing responses in coeliac neurons are sustained by the activation of the muscarinic Na, M current. The tonic activation of lNa, M in spontaneously firing cells results from a sustained Ca2+‐dependent tetrodotoxin‐sensitive release of acetylcholine. This study provides evidence that the role of the muscarinic receptors is not purely a neuromodulatory one, but that these receptors are directly involved in ganglionic neurotransmission.
A Decrease in [Ca2+]c but not in cAMP Mediates L‐AP4 Inhibition of Glutamate Release: PKC‐mediated Suppression of this Inhibitory Pathway
Authors: Herrero Inmaculada , Vázquez Elena , Miras‐Portugal M. Teresa , Sánchez‐Prieto José 
Published: April 2006

AbstractWe investigated the mechanism of the inhibition of glutamate release by L‐2‐amino‐4‐phosphonobutyrate (L‐AP4) in cerebrocortical nerve terminals from young rats (3 weeks of age). The Ca2+‐dependent release of glutamate was reduced by L‐AP4 in a concentration‐dependent manner. This inhibitory effect was prevented by pertussis toxin, insensitive to staurosporine and associated with a reduction both in the depolarization‐evoked increase in the cytoplasmic free Ca2+ concentration ([Ca2+]c) and in forskolin‐stimulated cAMP formation. However, the reduction in [Ca2+]c but not in cAMP seemed to be responsible for the decrease in release, since inhibition by L‐AP4 can also be observed in the absence of detectable changes in CAMP. The inhibitory modulation by L‐AP4 was suppressed by the activation of protein kinase C with phorbol esters. The nerve terminals from young rats also exhibited a facilitatory pathway of glutamate release which was mediated by protein kinase C. Interestingly, stimulation of this pathway with the glutamate agonist (1 S,3R)‐1‐aminocyclopentane‐1,3‐dicarboxylate in the presence of arachidonic acid also abolished the inhibitory action of L‐AP4. The dominance of the facilitatory pathway in its interaction with the L‐AP4‐mediated inhibitory control may provide some clues to understand the presynaptic changes during synaptic plasticity.
Ex Vivo Gene Transfer of Brain‐derived Neurotrophic Factor to the Intact Rat Forebrain: Neurotrophic Effects on Cholinergic Neurons
Authors: Martinez‐Serrano Alberto , Hantzopoulos Petros A. , Björklund Anders 
Published: April 2006

AbstractNeurotrophic effects of human brain‐derived neurotrophic factor (hBDNF) on forebrain cholinergic neurons were addressed after ex vivo gene transfer to the intact adult rat brain, using a conditionally immortalized neural progenitor cell line (CINP) engineered to secrete the neurotrophin (2.8 ng/h/106 cells). This cell line was derived by repeated retroviral infection of the parental neural precursor line HiB5 followed by subcloning. The cells survived well in the host brain for long periods of time (up to 4 weeks), and induced a hypertrophic response of cholinergic neurons (positive for acetylcholinesterase, choline acetyltransferase or low‐affinity nerve growth factor receptor) in the nucleus basalis magnocellularis and striatum. We conclude that these cholinergic cell groups are responsive to a low‐level supply (nanograms per day) of BDNF in vivo when the neurotrophin is administered locally in the vicinity of the cell bodies.
Selective Excitatory Amino Acid Uptake in Glutamatergic Nerve Terminals and in Glia in the Rat Striatum: Quantitative Electron Microscopic Immunocytochemistry of Exogenous D‐Aspartate and Endogenous Glutamate and GABA
Authors: Gundersen Vidar , Ottersen Ole Petter , Storm‐Mathisen Jon 
Published: April 2006

AbstractTo characterize glutamate/aspartate uptake activity in various cellular and subcellular elements in the striatum, rat striatal slices were exposed to 10 and 50 μM exogenous D‐aspartate. After fixation with glutaraldehyde/ formaldehyde the distribution of D‐aspartate was analysed by postembedding immunocytochemistry and the ultrastructural distribution was compared with the distributions of endogenous glutamate and GABA. Light microscopically, D‐aspartate‐like immunoreactivity was localized in conspicuous dots along very weakly labelled dendritic profiles and neuron cell bodies. At the electron microscope level gold particles signalling D‐aspartate occurred at highest density in nerve terminals making asymmetrical contacts with postsynaptic spines (i.e. resembling synapses of cortical afferents). Astrocytic processes also contained gold particles, but at a lower density than nerve endings. In contrast, dendritic spines were only weakly D‐aspartate–positive. The difference in labelling at 10 and 50 μM D‐aspartate was consistent with‘high‐affinity’uptake. Neighbouring sections processed with other antibodies showed that the D‐aspartate labelling occurred in nerve terminals strongly immunoreactive for glutamate, rather than in terminals very weakly glutamate‐immunopositive or in nerve endings immunoreactive for GABA. Glutamate labelling of perfusion‐fixed striatum confirmed that terminals forming asymmetrical synaptic contacts with spines were enriched with gold particles, suggesting that these terminals use glutamate as a transmitter. This study demonstrates that high‐affinity uptake sites for excitatory amino acids in the striatum are most strongly expressed on presumed glutamatergic nerve terminals and on astrocytes.
Opioid Inhibition of Ca2+ Channel Subtypes in Bovine Chromaffin Cells: Selectivity of Action and Voltage‐dependence
Authors: Albillos Almudena , Carbone Emilio , Gandia Luis , Garcia Antonio G. , Polio Antonella 
Published: April 2006

AbstractBovine chromaffin cells possess a mixture of high‐voltage‐activated Ca2+ channel subtypes: L‐type, dihydropyridine‐sensitive channels, and N‐, P‐ and Q‐types, ω‐conotoxin MVIIC‐sensitive channels. In these cells, we studied the reversible, naloxone‐antagonized inhibition of Ba2+ currents by the opioid agonist met‐enkephalin (IC50= 272 nM). This inhibition could be resolved into a voltage‐dependent and a voltage‐independent component. The first was revealed by its slow Ba2+ current activation kinetics at 0 mV and by the current facilitation induced by short prepulses to +90 mV. The second was estimated as the residual inhibition persisting after the facilitation protocol. The two inhibitory components varied markedly from cell to cell and each contributed to about half of the total inhibition. Replacement of internal GTP by GDP‐β‐S or cell pretreatment with pertussis toxin completely abolished the voltage‐dependent inhibition by opioids, partially preserving the voltage‐independent component. The opioid‐induced inhibition was not selective for any Ca2+ channel subtype, being not prevented after the addition of specific Ca2+ channel antagonists. However, when separately analyzing the contribution of each channel type to the voltage‐dependent and voltage‐independent modulation, a clear‐cut distinction could be achieved. The voltage‐independent inhibition was effective on all Ca2+ channel subtypes but predominantly on L‐type Ca2+ channels. The voltage‐dependent process was abolished by ω‐conotoxin‐MVIIC, but unaffected by nifedipine, and was thus sharply restricted to non‐L‐type channels (N‐, P‐ and Q‐types). Our data suggest a functionally distinct opioid receptor‐mediated modulation of L‐ and non‐L‐type channels, i.e. of the two channel classes sharing major control of catecholamine secretion from bovine chromaffin cells.
A Glutamate‐sensitizing Activity in Conditioned Media Derived from Rat Cerebellar Granule Cells
Authors: Ciotti Maria Teresa , Giannetti Stefano , Mercanti Delio , Calissano Pietro 
Published: April 2006

AbstractWhen cerebellar granule cells that had been cultured in vitro for 8 days were subjected to a cytotoxic glutamate pulse (100 μM, 30 min incubation), the response varied according to cell density and the volume of medium in which cells were grown. Thus, lowering the cell density by a factor of 4 compared with usual conditions (2.6 × 105 cells/cm2) or increasing the volume by an identical 4‐fold factor reduced cell death from 90‐95% to 20‐30%. Addition of a conditioned medium derived from high‐density to low‐density cultures or to high‐volume cultures markedly increased the sensitivity of the cells to glutamate. This glutamate‐sensitizing activity, which accelerated by several days the onset of the response of cerebellar cultures to glutamate, was inhibited by actinomycin D and was not detectable in conditioned medium derived from confluent cultures of cerebellar astroglia, or from cell lines such as PC12, GT1‐7, 3T3 and CHP 100. Glutamate‐sensitizing activity was not mimicked by triiodo‐L‐thyronine, insulin‐like growth factor‐I (IGF‐I), truncated IGF‐I, GPE [a tripeptide (gly‐pro‐glu) derived from IGF‐I], brain‐derived neurotrophic factor (BDNF), basic fibroblast growth factor or tumour necrosis factor‐α. However, IGF‐I added to cultures of granule cells plated at high density and grown in basal medium Eagle's without serum or any other constituent of chemically defined media was capable of supporting production of glutamate‐sensitizing activity to an extent similar to that shown by whole fetal calf serum. Under the same conditions triodoi‐L‐thyronine and BDNF did not support the production of glutamate‐sensitizing activity. Glutamate‐sensitizing activity was not mimicked by glutamate, NMDA, glycine or lactate, and was not inhibited by glucose, haemoglobin or N‐Ω‐nitro‐L‐arginine methyl ester. At variance with the response of granule cells, the response to glutamate of GABAergic cells present in the same culture was not affected by cell density or by glutamate‐sensitizing activity.
Characteristic Localization of gpl30 (the Signal‐transducing Receptor Component Used in Common for IL‐6/IL‐11/CNTF/LIF/OSM) in the Rat Brain
Authors: Watanabe D. , Yoshimura R. , Khalil M. , Yoshida K. , Kishimoto T. , Taga T. , Kiyama H. 
Published: April 2006

AbstractThe localization of gp130, the signal transducing receptor component used in common for interleukin (IL)‐6, IL‐11, ciliary neurotrophic factor (CNTF), LIF and OSM, in the rat brain was demonstrated by immunohistochemistry using an antibody specific to gpl30. The gp130 immunoreactivity was observed in both glial and neuronal cells. Two distinct neuronal staining patterns were observed. The first showed neuropil staining, observed mainly in telencephalic structures including the hippocampus, cerebral cortex and caudate‐putamen. The second pattern was observed on the cytoplasmic membrane of neuronal somata and was found primarily in the lower brainstem, in the large neurons of the reticular formation, and in spinal and cranial motor neurons. Electron‐microscopic analysis revealed that both types of gpl30 immunoreactivity were primarily associated with the cytoplasmic membrane and were not localized exactly at synaptic sites. Further, gpl30 immunoreactivity was also observed in the oligodendrocytes and subependymal zone. These widespread but characteristic patterns of gp130 immunoreactivity overlap well with those of IL‐6 receptor and CNTF alpha chains, suggesting a role of cytokines and growth factors such as IL‐6 and CNTF via gp130 in certain specific regions of the brain.
Developmentally Regulated Neurite Outgrowth Response from Dorsal Root Ganglion Neurons to Heparin‐binding Growth‐associated Molecule (HB‐GAM) and the Expression of HB‐GAM in the Targets of the Developing Dorsal Root Ganglion Neurites
Authors: Nolo Riitta , Kaksonen Marko , Rauvala Heikki 
Published: April 2006

AbstractHeparin‐binding growth‐associated molecule (HB‐GAM) is a highly conserved cell surface‐ and extracellular matrix‐associated protein that enhances neurite outgrowth in brain neurons in vitro. To study the possible response of peripheral neurons, we cultured chicken dorsal root ganglion neurons from different developmental stages from embryonic day 4.5 (E4.5; St 25) to E9 (St 35) on recombinant HB‐GAM. We discovered that the neurite outgrowth response to HB‐GAM is maximal at E5.5‐6.5 (St 28‐30). In order to correlate this in vitro phenomenon with in vivo phenomena, immunohistochemical staining and in situ hybridization were performed on cryosections. The protein expression of HB‐GAM peaked at E6 (St 29) and was most extensive on the dorsal spinal cord and dorsal roots. Using Dil labelling, we confirmed that at the time when sensory afferents travel longitudinally in the bundle of His of the spinal cord, HB‐GAM protein expression there is at its peak. Though HB‐GAM is a secreted protein, at the RNA level the timing of HB‐GAM appearance and existence in the spinal cord and sensory ganglia is in accordance with its protein expression. Our results demonstrate that peripheral neurons are responsive to substrate‐bound HB‐GAM in a developmentally regulated manner, and that the expression of both HB‐GAM mRNA and protein in vivo is spatially and temporally matched to this in vitro phenomenon. HB‐GAM is therefore a putative cue for the growth of sensory afferents to and within the dorsal spinal cord.
M‐cadherin Distribution in the Mouse Adult Neuromuscular System Suggests a Role in Muscle Innervation
Authors: Cifuentes‐Diaz Carmen , Goudou Danièle , Padilla Françoise , Facchinetti Patricia , Nicolet Marc , Mège René‐Marc , Rieger François 
Published: April 2006

AbstractM‐cadherin belongs to the Ca2+‐dependent cadherin family of cell adhesion molecules and was first isolated from a mouse muscle cell line cDNA library. It is specifically expressed in muscle tissue during development and is supposed to play an important role in secondary myogenesis. In the present study the expression of M‐cadherin mRNA and protein and its localization were investigated in adult mouse skeletal muscle and peripheral nerve. The mRNA was abundant in embryonic legs from embryonic day (E)14 to E18. It remained expressed in new‐born and adult muscles. In the adult muscle M‐cadherin immunoreactivity was only detected at the neuromuscular junction, associated with perijunctional mononucleated cells and on intramuscular nerves. Peripheral nerves were also M‐cadherin‐positive. The molecule was found at the surface of myelinated nerve fibres where it was concentrated at the node of Ranvier. When a nerve was crushed and allowed to regenerate, M‐cadherin was over‐expressed at the site of nerve injury and in the distal stump. M‐cadherin was also up‐regulated on the sarcolemma of denervated muscle fibres. Taken together, these observations point toward a much wider tissue distribution of M‐cadherin than previously thought. M‐cadherin might be involved not only in specific steps of myogenesis but also in some aspects of synaptogenesis, axon/Schwann cell interactions and node of Ranvier structural maintenance.
Long‐term Survival of Retina Optic Nerve Section in Adult Ganglion Cells Following bcl‐2 Transgenic Mice
Authors: Cenni Maria Cristina , Bonfanti Lidia , Martinou Jean‐Claude , Ratto Gian Michele , Strettoi Enrica , Maffei Lam berto 
Published: April 2006

AbstractThe bcl‐2 gene codes for a protein that acts as a powerful inhibitor of active cell death. Since the transection of the optic nerve in adult mammalians starts a massive process of degeneration in retinal ganglion cells, we investigated whether the overexpression of bcl‐2 in adult transgenic mice can protect the axotomited ganglion cells. We performed intracranial optic nerve transection on both wild type and transgenic adult mice, and we tested cell survival 2 or 3.5 months after axotomy. The percentage of surviving ganglion cells after optic nerve section was computed by combining the counts of the optic nerve fibres in intact nerves with the cell density measures of the ganglion cell layer of axotomized retinae. From these data we found that in transgenic mice˜65% of ganglion cells survived 3.5 months after axotomy. In contrast, 2 months after surgery, <10% of ganglion cells were left in wild type retinae. We have also examined the morphology and fine structure of the proximal stump of the sectioned optic nerves by light and electron microscopy. In the transgenic mice a very large number of axons survived after surgery and they still exhibited fairly normal morphology and ultrastructure. On the other hand the wild type transected nerves had only a few visible axons that displayed clear signs of degeneration. We conclude that the overexpression of Bcl‐2 protein in central neurons is a very effective strategy to ensure long‐term survival in axotomized cells.