bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Critical Period for Repair of CNS of Neonatal Opossum (Monodelphis domestica) in Culture: Correlation with Development of Glial Cells, Myelin and Growth‐inhibitory Molecules
Authors: Varga Z. M. , Bandtlow C. E. , Eurlkar S. D. , Schwab M. E. , Nicholls J. G. 
Published: April 2006

AbstractA comparison was made of neurite growth across spinal cord lesions in the isolated central nervous system (CMS) of newborn opossums (Monodelphis domestica) at various stages of development. The aim was to define the critical period at which growth after injury ceases to occur, with emphasis on growth‐inhibitory proteins, myelin and glial cells. In postnatal opossums 3–6 days old (P3–6), repair was observed 5 days after lesions were made in culture at the cervical level (C7) by crushing with forceps. Through‐conduction of action potentials was re‐established and axons stained by Oil grew into and beyond the crush. In a series of 66 animals 29 showed repair. In 28 animals at P11–12 with comparable lesions repair was observed in five preparations. At P13–14, the CMS was still viable in culture, but none of the 25 preparations examined showed any axonal growth into the crush or conduction through it. The rostra‐caudal gradient of development permitted lesions to be made in mature cervical and immature lumbar regions of P11–12 spinal cord. Growth across crushes occurred in lumbar but not in cervical segments of the same preparation. The development of glial cells and myelin was assessed by electron microscopy and by staining with specific antibodies (Rip‐1 and myelin‐associated glycoprotein) in cervical segments of neonatal P6–14 opossums. At P8, oligodendrocytes and thin myelin sheaths started to appear followed at P9 by astrocytes stained with antibody against glial fibrillary acidic protein. By P14, astrocytes, oligodendrocytes and well‐developed myelin sheaths were abundant. The cervical crush sites of P12 cords contained occasional astrocytes but no oligodendrocytes. Specific antibodies (IN‐1) to neurite growth‐inhibiting proteins (NI‐35/250) associated with oligodendrocytes and myelin in the rat CNS cross‐reacted with opossum proteins. Assays using the spreading of 3T3 fibroblasts and IN‐1 showed that by P7 inhibitory proteins became apparent, particularly in the hindbrain and cervical spinal cord. The concentrations of NI‐35/250 thereafter increased and became abundant in the adult opossum. Our finding of a well‐defined critical period, encompassing only 5 days, in CNS preparations that can be maintained in culture offers advantages for analysing mechanisms that promote or prevent CNS repair.
Purification of a Meningeal Cell‐derived Chondroitin Sulphate Proteoglycan with Neurotrophic Activity for Brain Neurons and its Identification as Biglycan
Authors: Junghans Ulrich , Koops Antje , Westmeyer Annette , Kappler Joachim , Meyer Helmut E. , Müller Hans Werner 
Published: April 2006

AbstractSerum‐free cultures of meningeal fibroblasts synthesize and release a chondroitin sulphate proteoglycan (CSPG) that markedly enhances survival but not adhesion of embryonic rat (embryonic day 15) neocortical neurons in vitro. The active molecule was purified from conditioned medium (meningeal cell‐conditioned medium, MCM) in three steps by means of fast‐performance liquid chromatography fractionation combined with a quantitative microphotometric bioassay: (i) preparative Q‐Sepharose anion exchange chromatography under native conditions; (ii) rechromatography of biologically active Q‐Sepharose fractions on a MonoQ column in the presence of 8 M urea; and (iii) final gel filtration of active MonoQ fractions on Superose 6 in the presence of 4 M guanidinium hydrochloride. Analytical sodium dodecyl sulphate‐polyacrylamide gradient gel electrophoresis of active Superose 6 fractions revealed a single broad glycoprotein band with a molecular mass in the range of 220–340 kDa. Further characterization of the purified molecule with glycosaminoglycan:lyases revealed a core protein of 50 kDa and the nearly complete loss of neurotrophic activity after chondroitinase digestion, whereas heparitinase treatment changed neither electrophoretic mobility nor biological activity. Amino‐terminal sequencing of the purified CSPG core protein revealed identity with the amino acid sequence of rat biglycan. Biglycan purified from bovine cartilage supported neuron survival with virtually the same activity as the CSPG purified from MCM (half‐maximal activity ∼10‐8 M). In conclusion, we isolated a neurotrophic CSPG from meningeal cells with strong survival‐enhancing activity for brain neurons that was identified as biglycan, a molecule not previously related to neural functions.
Actions of Glycine on Non‐dopaminergic Neurons of the Rat Substantia Nigra
Authors: Mercuri Nicola B. , Bonci Antonello , Pisani Antonio , Calabresi Paolo , Bernardi Giorgio 
Published: April 2006

AbstractThe effects of glycine on non‐dopaminergic cells in rat substantia nigra pars compacta and pars reticulata maintained in vitro were investigated using intracellular recording techniques. Glycine, superfused at a concentration between 30 μM and 1 mM, reversibly blocked the spontaneous firing of these neurons. The inhibition of firing discharge was associated with a hyperpolarization of the membrane (potassium acetate‐filled electrodes) and an increase in conductance. Under voltage‐clamp experiments (holding potential between ‐57 and ‐65 mV), glycine produced an outward response which reversed polarity at about ‐74 mV. However, when the recording electrodes were filled with KCI, the glycinergic response was mainly depolarizing/inward and reversed at about ‐43 mV. Thus, it appeared to be due to an increase in chloride permeability. Furthermore, the effects of glycine were reversibly antagonized by strychnine (between 300 nM and 1 μM). Our findings demonstrate that glycine is a potent inhibitory agent on non‐dopaminergic cells of the substantia pars compacta and pars reticulata that acts by activating strychnine‐sensitive receptors.
Serotonin Modulation of Inferior Olivary Oscillations and Synchronicity: A Multiple‐electrode Study in the Rat Cerebellum
Authors: Sugihara I. , Lang E. J. , Llinás R. 
Published: April 2006

AbstractSimultaneous recording of complex spikes from multiple Purkinje cells (up to 44) in the rat cerebellum was used to examine the effects of 5‐hydroxytryptamine (serotonin, 5‐HT) on olivocerebellar function. Microinjection into the inferior olive was found to increase the average firing rate of inferior olivary neurons while slowing their oscillation frequency and increasing the coherence of their oscillations. Indeed, while the normal rostrocaudal band of synchronous activity remained unchanged, the degree of synchrony between Purkinje cell complex spikes within this band was enhanced following the 5‐HT injections. Multiple‐electrode recordings obtained from crus Ha and vermal lobule Vlb yielded qualitatively similar results; however, the effects on vermal activity were more pronounced. The effects of the 5‐HT microinjection decayed with a time course of 75 min. The half‐maximum effective concentration of 5‐HT was between 10 and 100 μM. Injections of various 5‐HT agonists and antagonists demonstrated that a 5‐HT type‐2A (5‐HT2A) receptor is the main mediator for the 5‐HT effect, which was very similar to the effect produced by injections of harmaline. However, 5‐HT and harmaline appear to have independent mechanisms since the action of harmaline was not blocked by the 5‐HT2A antagonist LY53857. A possible role for 5‐HT, as a physiological enhancer of the timing of motor function of the olivocerebellar system, is discussed.
Age‐related Changes in the NMDA Receptor/Nitric Oxide/cGMP Pathway in the Hippocampus and Cerebellum of Freely Moving Rats Subjected to Transcerebral Microdialysis
Authors: Vallebuona F. , Raiteri M. 
Published: April 2006

AbstractThe N‐methyl‐d‐aspartate (NMDA) receptor/nitric oxide synthase/guanylate cyclase pathway was studied during aging by monitoring extracellular cGMP in the rat hippocampus and cerebellum during in vivo microdialysis. In the hippocampus the basal cGMP efflux decreased by 50% from 3 to 12 months of age, whereas it remained constant with age in the cerebellum. Locally perfused NMDA (1 mM) evoked remarkable cGMP responses in 3‐month‐old rats; in the hippocampus the cGMP production was already dramatically reduced at 12 months, whereas in the cerebellum a similar impairment occurred much later (24 months). The nitric oxide donor S‐nitroso‐N‐penicillamine (1 mM) elicited cGMP responses which slightly decreased from 3 to 12–24 months in the hippocampus, while no significant decrement with age could be seen in the cerebellum. Local perfusion of the phosphodiesterase inhibitor 3‐isobutyl‐1 methylxanthine (IBMX, 1 mM) produced large increases in hippocampal cGMP levels. The response decreased at 12 and 24 months, apparently in parallel with the fall in the basal level of cGMP. No significant differences across ages were observed following IBMX infusion in the cerebellum. The decreases in basal outflow and in the NMDA‐evoked cGMP response seen in the aged hippocampus were not compensated for by supplying l‐arginine. Infusion of d‐serine (1 mM) enhanced (150–200%) extracellular cGMP in the cerebellum with no age‐related differences. The activity in vitro, of hippocampal nitric oxide synthase at 24 months was 33% lower than at 3 months, whereas the cerebellar enzyme did not show any age‐related decay. Aging seems therefore to affect differentially the NMDA receptor/nitric oxide synthase/cGMP pathway in the rat hippocampus versus the cerebellum. In the hippocampus the early fall in the NMDA‐evoked cGMP response seems to originate from deficits in NMDA receptor function and nitric oxide synthase and guanylate cyclase activities; in the cerebellum, the decreased response to NMDA in the old animals seems essentially to be due to impairment of NMDA receptor function.
Double In Situ Hybridization Reveals Overlapping Neuronal Populations Expressing the Low Molecular Weight GTPases Rab3a and Rab3b in Rat Brain
Authors: Stettler Olivier , Nothias Fatiha , Tavitian Bertrand , Vernier Philippe 
Published: April 2006

AbstractThe ras‐related Rab3 gene subfamily codes for small GTP‐binding proteins which control a late step of exocytosis during which vesicles become docked to the plasma membrane. Rab3a and Rab3b are the most abundant Rab3 isoforms expressed in the CNS of mammals. We have shown previously that the Rab3a protein was selectively distributed and expressed in various regions of the rat brain. Here we have determined the pattern of expression of Rab3b mRNA in the brain and compared it with that of Rab3a mRNA. In addition, we examined the co‐expression of these two Rab within individual neurons. In general the Rab3b transcript was detected in many regions which also express Rab3a mRNA but at a lower level than Rab3a, except in the olfactory bulb and in the pituitary where the Rab3b hybridization signal was similar and higher respectively. Double in situ hybridization revealed that Rab3a and Rab3b mRNAs were co‐localized in most neurons, in all brain areas examined. However, in each of these areas, subsets of neurons appeared to preferentially express either Rab3b or Rab3a, or some neurons did not express either Rab3 homologue at detectable levels. These data support the view of a functional specialization of Rab3a and Rab3b in the control of exocytosis in neuronal and neuroendocrine cells.
Neurophysiological Investigations of a Recognition Memory System for Imprinting in the Domestic Chick
Authors: Nicol A. U. , Brown M. W. , Horn G. 
Published: April 2006

AbstractThe responsiveness of neurons in a region of the chick brain involved in the learning process of imprinting, the right intermediate and medial hyperstriatum ventrale (right IMHV), has been investigated in unanaesthetized, trained and untrained chicks. The results demonstrate that neuronal responsiveness in this region reflects a variety of behavioural consequences of imprinting and is markedly altered as a result of the learning process. Groups of chicks (nine in each group) were either dark‐reared or trained (imprinted) by exposure to a rotating red box or a rotating blue cylinder. Recordings of single or small groups of neurons were subsequently made from 156 sites in the right IMHV while the 2‐day‐old chicks were free to move in a running wheel. There was a highly significant increase in the proportion of sites responsive to the stimulus used to train the birds compared to the proportion responsive to that stimulus in dark‐reared birds (30 and 9% respectively). These changes were found when either the red box or the blue cylinder was used to train the bird, the changes being similar for both stimuli. There was also a significant increase in the mean magnitude of the change in neuronal activity on stimulus presentation for the training stimulus compared to the same stimulus when not used in the bird's training. No significant effects of the training experience of the chicks were found upon either the magnitude of evoked activity or the proportion of sites responsive to a rotating stuffed jungle fowl or the sound of the maternal call. The presence of the training stimulus was selectively signalled by the response at certain sites. At other sites there was response generalization across stimulus shape or colour. A comparison with results for the left IMHV demonstrates both similarities and differences in neuronal responsiveness between the two regions. In both regions imprinting selectively enhances neuronal responsiveness to the training stimulus. However, for trained birds the mean proportion of sites responding to whichever of the red box or the blue cylinder was not used in the bird's training was significantly lower in the right than the left IMHV. These results are discussed in relationship to previously reported asymmetries in the response of the right and left IMHV regions to imprinting. A model is introduced to explain the physiological findings. The effects of training on right IMHV neuronal function are consistent with a long‐term role for this region in the recognition memory of imprinting.
Up‐regulation of a Chondroitin Sulphate Epitope during Regeneration of Mouse Sciatic Nerve: Evidence that the Immunoreactive Molecules are Related to the Chondroitin Sulphate Proteoglycans Decorin and Versican
Authors: Braunewell Karl‐Heinz , Martini Rudolf , LeBaron Richard , Kresse Hans , Faissner Andreas , Schmitz Brigitte , Schachner Melitta 
Published: April 2006

AbstractAfter transection of adult mouse sciatic nerve, the expression of a chondroitin sulphate epitope recognized by the monoclonal antibody 473‐HD (mAb 473‐HD) was found to be up‐regulated. The epitope was localized immunocytochemically mainly in Schwann cell basal laminae and, more weakly, also in the endoneurium. In cultures of mouse dorsal root ganglion cells, Schwann cells expressed high levels but fibroblasts only low levels of the epitope. To identify the molecule(s) carrying this chondroitin sulphate epitope, human sciatic nerves were extracted with phosphate‐buffered saline and shown to contain two chondroitin sulphate proteoglycans of apparent molecular weights of 130 and 900 kDa. The 900 kDa and, more weakly, the 130 kDa proteoglycan were reactive with mAb 473‐HD, which was found to recognize chondroitin‐6‐sulphate as epitope. Following chondroitinase ABC treatment of the 130 kDa proteoglycan, a core protein of ∼45 kDa was seen and shown to react with polyclonal antibodies against the chondroitin‐dermatan sulphate proteoglycan decorin from human fibroblasts. Chondroitinase ABC treatment of the 900 kDa proteoglycan yielded a core protein with a molecular weight of ∼400 kDa that was recognized by polyclonal antibodies against recombinantly expressed fusion proteins from human versican. After transection of adult mouse sciatic nerves, the distal nerve stumps showed up‐regulation of the chondroitin‐6‐sulphate epitope of the 900 kDa proteoglycan, whereas the core protein of this proteoglycan did not show any detectable change in the level of expression. In contrast, the core protein of the 130 kDa proteoglycan was up‐regulated in expression. These observations suggest that versican‐ and decorinlike molecules may contribute to successful regeneration in the peripheral nervous system of mammals.
Anatomical Distribution and Postnatal Changes in Endogenous Free D‐Aspartate and D‐Serine in Rat Brain and Periphery
Authors: Hashimoto Atsushi , Oka Takae , Nishikawa Toru 
Published: April 2006

AbstractWe have investigated the anatomical distribution and postnatal development of D‐aspartate and D‐serine in the rat brain and periphery using HPLC techniques. D‐Serine was confined predominantly to the brain throughout postnatal life. At birth, a substantial quantity of D‐serine was observed throughout the brain areas. The cerebral D‐serine content increased from birth to postnatal week (PW) 3 and remained constant thereafter, whereas the cerebellar D‐serine content peaked at PW1. In contrast, the transient emergence of D‐aspartate was found in almost all brain and peripheral organs. A substantial quantity of D‐aspartate was also seen in all brain areas at birth, whereas the D‐aspartate content in the cerebrum and cerebellum decreased dramatically by PW1 and 7 respectively. Further, the D‐aspartate content and the ratio of D‐aspartate to total aspartate were highest in the adrenal at PW3 (608 ± 70 nmol/g, 45.9%) and in the testis at PW14 (221 ± 7 nmol/g, 57.8%) respectively. Because D‐serine potentiates N‐methyl‐D‐aspartate receptor‐mediated transmission through the strychnine‐insensitive glycine site and because D‐serine exhibits an N‐methyl‐D‐aspartate receptor‐related distribution and development, D‐serine may be a tenable candidate for an intrinsic ligand for the glycine site. In contrast, because the periods of maximal emergence of D‐aspartate in the brain and periphery occur during critical periods of morphological and functional maturation of organs, D‐aspartate could participate in the regulation of these developmental processes of organs.
Alpha1‐adrenergic Effects on Dopamine Neurons Recorded Intracellularly in the Rat Midbrain Slice
Authors: Grenhoff Johan , North R. Alan , Johnson Steven W. 
Published: April 2006

AbstractPrevious studies have indicated excitatory adrenergic effects on midbrain dopamine systems. To investigate the cellular mechanisms, intracellular recordings were made from neurons in perfused, oxygenated slices of male rat midbrain. Electrophysiological and pharmacological parameters were used to identify cells as principal (presumably dopaminergic) neurons as opposed to secondary (presumably GABAergic) neurons in the substantia nigra zona compacta and the ventral tegmental area. Noradrenalin (10–100 μM) hyperpolarized 57% of all principal cells and depolarized 36%. Sulpiride (100–1000 nM), a dopamine D2 receptor antagonist, completely blocked noradrenalin‐induced hyperpolarizations (six of six cells). In sulpiride, noradrenalin depolarized 58% of all principal neurons and had no effect in 42%; this effect was mimicked by the α‐adrenergic agonist phenylephrine (10–30 μM) which depolarized 43 of 72 cells. The α1 receptor antagonist prazosin (30–100 nM) completely blocked the membrane depolarization produced by either noradrenalin or phenylephrine in all cells tested, whereas α2‐ and β‐adrenergic agents had no effect. In voltage clamp, phenylephrine evoked an inward current (at ‐60 mV) and reduced cord conductance by 0.81 ± 0.14 nS (n= 4). Inward current evoked by phenylephrine became outward at ‐96 ± 8 mV, which is near the membrane reversal potential for potassium as predicted by the Nernst equation. Phenylephrine also depolarized secondary cells and increased the frequency of spontaneous GABAA receptor‐mediated postsynaptic potentials recorded in both principal and secondary cells. We conclude that stimulation of α1‐adrenergic receptors depolarizes principal (dopamine) neurons by reducing membrane conductance for potassium, but this effect is modulated by the increase in frequency of spontaneous inhibitory postsynaptic potentials evoked by stimulation of α1‐adrenergic receptors located on local interneurons.
Development of Electrical Membrane Properties and Discharge Characteristics of Superior Olivary Complex Neurons in Fetal and Postnatal Rats
Authors: Kandler Karl , Friauf Eckhard 
Published: April 2006

AbstractAlthough hearing onset occurs relatively late during ontogeny of rats [around postnatal day (P) 12], anatomical brainstem connections are formed much earlier and are present before birth, indicating that a substantial amount of maturation occurs without acoustic input. Electrical activity is thought to influence neuronal development, but the physiological properties of auditory brainstem neurons during perinatal maturation are barely known. The present study focuses on the development of electrophysiological membrane properties of neurons in the rat's superior olivary complex (SOC), the first binaural station in the mammalian auditory brainstem. In in vitro slice preparations, intracellular recordings were obtained from 115 SOC cells from embryonic day (E) 18 to P17, and cells were morphologically identified by intracellular injection of biocytin or neurobiotin. By E18, i.e. 4 days before birth, SOC neurons were capable of generating Na+‐dependent action potentials. Several passive and active membrane properties, including the resting potential, spike threshold and spike amplitude, did not change with development. In contrast, input resistance, time constant and spike duration decreased significantly, and maximal spike frequency increased significantly during the age period sampled. Our results show that rat SOC neurons display mature as well as immature electrical membrane properties during the same developmental period when anatomical connections are refined and when the soma‐dendritic morphology develops. We conclude, therefore, that their membrane properties represent adequate physiological adaptations to the immature auditory brainstem microcircuits and that they form a basis upon which the development of these microcircuits is shaped.
Developmental Regulation of Acetylcholinesterase Transcripts in the Mouse Diaphragm: Alternative Splicing and Focalization
Authors: Legay Claire , Huchet Monique , Massoulié Jean , Changeux Jean‐Pierre 
Published: April 2006

AbstractWe studied the splicing and compartmentalization of acetylcholinesterase (AChE) mRNAs during muscle differentiation in the mouse, both in vitro and in vivo. We used the polymerase chain reaction (PCR) to analyse AChE mRNAs in cultures of the myogenic C2 and So l8 cell lines, and in the developing diaphragm, from embryonic day 14 (E14). We characterized three types of alternatively spliced AChE mRNAs, encoding catalytic subunits that differ by their C‐terminal regions (R, H and T). The T transcript is predominant in all cases and represents the only AChE mRNA in the adult muscle. We detected the presence of the minor R and H transcripts in the myogenic cell lines, both as myoblasts and differentiated myotubes, and also in the diaphragm from E14 until birth. At E14 the R transcript represents ∼1% of AChE mRNA and the level of the H transcript is still lower. By in situ hybridization, we found that the T AChE mRNAs begin to preferentially accumulate at the level of the first neuromuscular contacts in the mouse diaphragm and other muscles as early as E14, e.g. concomitantly with mRNAs encoding the receptor subunits. This suggests that a common control mechanism ensures the synaptic focalization of mRNAs encoding the cholinergic proteins AChE and acetylcholine receptor during muscle development.