bluuebunny/crossref_metadata_2025_split huggingface dataset:
Axonal Transport of Dopamine‐containing Vesicles Labelled In Vivo with [3H] Reserpine
Authors: Lechardeur D. , Castel M. N. , Reibaud M. , Scherman D. , Laduron P. M. 
Published: April 2006

AbstractAxonal transport of the vesicular monoamine transporter was assayed in the rat brain by in vivo binding of the specific ligand [3H] reserpine. Because of the marked localization of reserpine binding sites in dopaminergic cell bodies and nerve terminals, the dopaminergic nigrostriatal pathway was chosen for the study of the axonal transport of the monoamine carrier present in the membrane of synaptic vesicles. When labelled reserpine was injected into the substantia nigra, a delayed accumulation of radioactivity in the ipsilateral striatum was observed ∼4 h after the injection. Similarly, injection into the right striatum was followed by a substantial accumulation of radioactivity in the ipsilateral substantia nigra, which was prevented by peripheral injection of unlabelled reserpine or tetrabenazine. This process was rapid and dependent on microtubules. In senescent rats, the amount of retrogradely transported [3H] reserpine was significantly reduced. These results demonstrate that labelled reserpine may be used to monitor in vivo fast axonal transport in central neurons.
In Vitro Phosphorylation in Isolated Horizontal Cells of the Fish Retina: Effects of the State of Light Adaptation
Authors: Janssen‐Bienhold Ulrike , Nagel Heinz , Weiler Reto 
Published: April 2006

AbstractHorizontal cells, which are second‐order neurons of the vertebrate retina, exhibit synaptic plasticity governed by light and dark adaptation. We have investigated the alterations in the protein phosphorylation patterns of isolated carp (Cyprinus carpio) horizontal cells in relation to their state of light adaptation by using an in vitro phosphorylation assay and compared the resulting data with protein synthesis patterns of the whole retina. Phosphoproteins and [35S]methionine‐labelled proteins were analysed by one‐ and two‐dimensional gel electrophoresis followed by autoradiography. The state of light adaptation significantly affected the in vitro phosphorylation of horizontal cell proteins with molecular weights of 68, 56/58, 47, 28 and 15 kDa, but had no effect on the protein synthesis of retinal proteins. In the light the most prominent increase of 32P incorporation was observed in the 47 kDa protein. The biochemical properties of this protein closely resembled those of the growth‐associated GAP‐48, found in the fish retina. In addition, the phosphorylation of horizontal cell homogenates in the presence of protein kinase activators such as cyclic AMP, calcium, calmodulin and phospholipids revealed that horizontal cells of the fish retina contain cyclic AMP‐, calcium/calmodulin‐ and calcium/phospholipid‐dependent protein kinase activity resulting in the phosphorylation of several horizontal cell proteins, including the phosphoproteins which were affected by the state of light adaptation.
The Proximal Region of the MBP Gene Promoter is Sufficient to Induce Oligodendroglial‐specific Expression in Transgenic Mice
Authors: Goujet‐Zalc C. , Babinet Ch. , Monge M. , Timsit S. , Cabon F. , Gansmüller A. , Miura M. , Sanchez M. , Pournin S. , Mikoshiba K. , Zalc B. 
Published: April 2006

AbstractTo characterize regulatory DNA sequences involved in oligodendroglial expression of myelin basic protein (MBP), transgenic mice carrying a 256 bp fragment of the mouse MBP promoter fused to an Escherichia coli lacZ gene were generated. Of four transgenic families, two (lines 2 and 4) expressed β‐galactosidase activity in the nervous system but not in most other tissues. Histochemical and immunohistochemical analysis of adult brain from these two lines showed oligodendroglial‐specific expression of the transgene. In line 2, only a small proportion of oligodendrocytes expressed the transgene, and in labelled cells the product of the enzymatic reaction with β‐galactosidase was confined to a small round vesicle in the vicinity of the nucleus. In contrast, in tissue sections from line 4 adult brain and spinal cord β‐galactosidase activity was much more intense and at least 80 – 90% of oligodendrocytes expressed the transgene. Detection of the MBP‐lacZ transcript by in situ hybridization showed that the transgene mRNA was confined to the oligodendrocyte cell body. These results suggest that cis‐acting regulatory elements, specifying oligodendrocytes identity, are located within 256 bp upstream from the MBP gene.
Developmentally Regulated Expression of CGRP in the Mouse Olfactory Pathway
Authors: Denis‐Donini S. , Chini B. , Vitadello M. 
Published: April 2006

AbstractThe pattern of expression of the neuropeptide CGRP and its encoding mRNA has been determined by immunohistochemistry and in situ hybridization in the mouse olfactory pathway during development. Specific CGRP transcripts are first detected at E13 followed by the appearance of the peptide at E15. Both peptide and transcript are present until birth; their expression then appears to be down‐regulated since postnatally the peptide is only observed in some olfactory receptor neurons. A monoclonal antibody that specifically recognizes the neurofilament subunit NF‐M has been used in order to identify olfactory and trigeminal axons. Our results demonstrate that CGRP is expressed in olfactory neurons and their axons during development, thus supporting further its role as a differentiation factor during olfactory bulb ontogenesis.
Changes in the Mechanical Tuning Characteristics of the Hearing Organ Following Acoustic Overstimulation
Authors: Ulfendahl Mats , Khanna Shyam M. , Löfstrand Paula 
Published: April 2006

AbstractAn in vitro preparation of the guinea‐pig temporal bone was used to study the effects of acoustic overstimulation on the mechanical tuning characteristics of the inner ear. Using laser heterodyne interferometry, the vibratory responses of selected sensory and supporting cells within the hearing organ were measured in response to acoustic signals applied to the ear to obtain mechanical tuning curves before and after applying acoustic overstimulation. Following overstimulation the frequency at which the maximal vibration response occurred moved towards lower frequencies, the vibration amplitude generally increased and the shape of the mechanical tuning curves became considerably flatter. These effects were seen within minutes of overstimulation. The micromechanical changes were accompanied by distinct morphological changes mainly affecting the first row of outer hair cells, which were swollen and shortened. Hensen bodies and swelling of the subsurface cisternae were observed in the affected cells. Apart from this, most of the shortened cells looked structurally intact, had undamaged sensory hair bundles and made synaptic contacts to both afferent and efferent nerve fibres. The results demonstrate that the outer hair cells play a key role in determining the tuning of the hearing organ.
Differential Responses of Single Reticulospinal Cells to Spatially Localized Stimulation of the Optic Tectum in a Teleost Fish, Salmo trutta
Authors: Bosch T. J. , Paul D. H. 
Published: April 2006

AbstractTo determine whether the topographically organized retinal input to the optic tectum is subsequently mapped onto the reticular formation, the responses of antidromically identified reticulospinal cells to tectal surface stimulation were investigated in 45 decerebrated, paralysed trout. The tectum was stimulated through a silver ball surface electrode at 24 different locations, and extracellular recordings were made from the rhombencephalic brainstem with glass microelectrodes filled with a 10% solution of horseradish peroxidase (HRP) in Tris buffer (pH 7.4). After recording, the HRP was, in some cases, iontophoretically expelled from the pipette to identify its location and visualized in histological sections by a modified Hanker‐Yates method. Individual reticulospinal neurons discharged 1 – 4 spikes at short latency in response to stimulation of each of the 24 tectal locations. From one tectal location per cell, this initial response was followed by a late, sustained burst. With a short stimulus train (6 pulses, 55 Hz) the burst could last for over a second with discharge rates of up to 500 Hz. Sometimes this burst could be evoked from neighbouring tectal locations, but only by greatly increasing the stimulus strength. We conclude that the reticular formation receives a highly divergent monosynaptic connection from all locations of the tectum and that the longer latency, sustained burst response is due to a mapped connection between the tectum and the reticular formation. Since the late burst could be preceded by a silent period lasting for ∼32 ms, we cannot rule out a dependence on interneurons situated between the tectum and the reticulospinal cells.
In vitro and In vivo Analysis of a Rat Bipotential O – 2A Progenitor Cell Line Containing the Temperature‐sensitive Mutant Gene of the SV40 Large T Antigen
Authors: Barnett Susan C. , Franklin Robin J. M. , Blakemore William F. 
Published: April 2006

AbstractPrimary cultures from neonatal rat optic nerve contain pluripotential O – 2A progenitor cells that are capable of differentiating into oligodendrocytes, type‐2 astrocytes or adult O – 2A progenitors (O – 2Aadult). Since primary optic nerve cultures contain a mixture of glial cell types of which only a small number are O – 2A progenitors, experiments on cell lineage and differentiation carried out using these cultures are both intrinsically limited and difficult to interpret. Ideally, cells from a clonal cell population would provide the optimal starting material for biological studies. In this paper we describe the creation of an O – 2A progenitor cell line using a retrovirus carrying a temperature‐sensitive mutant SV40 large T antigen gene. This cell line has provided sufficient numbers of cells to allow analysis of their in vitro properties and their behaviour following transplantation into an in vivo environment. At the non‐permissive temperature (39°C), these cells differentiate into oligodendrocytes and type‐2 astrocytes in a similar fashion to O – 2A progenitor cells from primary cultures (O – 2Aprim). When grown in media containing platelet‐derived growth factor and basic fibroblast growth factor, the cell numbers can be expanded in culture without differentiating, consistent with the behaviour of O – 2Aprim progenitor cells. By exploiting this property, it has been possible to culture large numbers of O – 2A progenitors for in vivo analysis. In this study we have shown that transplantation of this O – 2A cell line into glia‐free areas in adult rat spinal cord results in differentiation of a proportion of cells into oligodendrocytes which are capable of myelinating axons. Furthermore, differentiation of O – 2A cells into astrocytes was also observed, indicating that the bipotentiality of these cells in vitro can also be demonstrated in vivo.
Methoxyverapamil Reduction of Nicotine‐induced Catecholamine Release Involves Inhibition of Nicotinic Acetylcholine Receptor Currents
Authors: Boehm Stefan , Huck Sigismund 
Published: April 2006

AbstractThe mechanism by which the putative Ca2+ channel blocker methoxyverapamil (D600) inhibits nicotine‐induced catecholamine release was investigated in bovine adrenal chromaffin cells and in neurons from paravertebral sympathetic ganglia of chick embryos. We found D600 to prevent catecholamine release evoked by 30 s applications of nicotine with a significantly higher potency than the release induced either by 30 s K+ depolarizations or by electrical field stimulation of sympathetic neurons. Like the use‐dependent action of D600 upon Ca2+ channels, the magnitude of inhibition of the K+‐evoked secretion depended on the duration of stimulation (10 s to 5 min). Data on catecholamine release were supplemented by patch‐clamp recordings. We found whole‐cell currents in chromaffin cells evoked by (extrapolated) 0.5 s applications of nicotine to be significantly more sensitive to D600 than Ca2+ currents induced by a 0.5 s depolarization from ‐80 to 0 mV. In both instances, the potency of D600 depended on the duration of the (nicotinic and depolarizing) stimuli. Our data suggest that D600 inhibits nicotine‐induced catecholamine release by reducing nicotinic acetylcholine receptor currents rather than voltage‐gated Ca2+ currents. Hence, in chromaffin cells as well as in sympathetic neuronal preparations, D600 does not appear to be a suitable tool to investigate the part voltage‐activated Ca2+ currents play in cellular events induced by nicotine.
A Study of the Barium‐sensitive and ‐insensitive Components of the Action of Thyrotropin‐releasing Hormone on Lumbar Motoneurons of the Rat Isolated Spinal Cord
Authors: Fisher N. D. , Nistri A. 
Published: April 2006

AbstractThe electrophysiological action of thyrotropin‐releasing hormone (TRH) on rat spinal motoneurons was studied in vitro using single‐electrode voltage‐ and current‐clamp techniques. In current‐clamp conditions TRH elicited a slowly developing depolarization, associated with a large input resistance increase and sustained neuronal firing; the primary metabolites of TRH were ineffective. Under voltage‐clamp conditions in the presence of tetrodotoxin, TRH evoked a large inward current (ITRH; peaking at approximately –40 mV) associated with a large input conductance fall. Only 44% of cells displayed ITRH reversal; when the chord conductance values of these cells were plotted against membrane potential, a bell‐shaped relation occurred, indicating voltage‐dependent block by TRH of a persistent conductance active over a wide range of membrane potentials. ITRH reversal values were shifted to more positive levels in high K+ solution in Nernstian fashion; hence a large proportion of the TRH response is suggested to be mediated by the block of a K+ conductance (IK(T)). IK(T) (and its voltage‐dependent block by TRH) was resistant to certain K+ channel antagonists (tetraethylammonium, Cs+, 4‐aminopyridine or apamin), but was depressed by Ba2+. The Ba2+‐resistant fraction of ITRH was attenuated by Cd2+, Mn2+ or Co2+, indicating that it probably involved a Ca2+‐sensitive inward current. Concomitant application of Ba2+ and Cd2+ induced a near‐total block of the response to TRH. It is suggested that suppression of IK(T), associated with the onset of a Ca2+‐sensitive current, can explain the excitatory effect of TRH on rat spinal motoneurons.
Cysteine Sulphinate and Cysteate: Mediators of Cysteine Toxicity in the Neonatal Rat Brain?
Authors: Lehmann Anders , Hagberg Henrik , Orwar Owe , Sandberg Mats 
Published: April 2006

AbstractExcitotoxic amino acids contain two acidic groups, but cysteine represents an exception to this rule. The hypothesis that cysteine toxicity is mediated by the oxidized and diacidic metabolites cysteine sulphinate and/or cysteate was tested in the present study. The issue was approached in three different ways. Firstly, the distribution of brain injury after subcutaneous administration of cysteine (1 mg/g) to 4‐day‐old rats was compared with that caused by cysteine sulphinate (3 mg/g). Secondly, the effects of excitatory amino acid receptor antagonists on cysteine and cysteine sulphinate toxicity were investigated. Thirdly, the cerebral concentrations of cysteine sulphinate were determined after cysteine administration and compared with those obtained after cysteine sulphinate injection. The cerebral cortex was the region most vulnerable to cysteine toxicity, followed by the hippocampus (especially the medial subicular neurons), amygdala, caudoputamen, cerebellum and septum. Pronounced extravasation of red blood cells was observed in lesioned areas. One day after cysteine administration, the injury was infarction‐like and sharply demarcated. Cysteine sulphinate‐induced damage resembled cysteine‐induced lesions in some respects: the anterior cingulate and retrosplenial cortices, as well as medial subicular cells, were quite vulnerable. However, the differences prevailed. Cysteine sulphinate, but not cysteine, killed neurons of the superficial part of the tectum, the medial habenula, the ventromedial hypothalamus and the arcuate nucleus. Further, while cysteine toxicity was prominent in deep cortical layers, cysteine sulphinate preferentially damaged superficial cortical neurons. Cysteine toxicity was abolished by pretreatment with MK‐801, a selective NMDA antagonist, but not by 2,3‐dihydroxy‐6‐nitro‐7‐sulphamoyl‐benzo(F)quinoxaline, a selective AMPA receptor blocker. In contrast, the considerably smaller lesion seen after cysteine sulphinate administration was only partially prevented by MK‐801. Large (19‐fold) increases in cortical cysteine sulphinate concentration were noted after injection of a toxic dose of cysteine. This corresponds to 90 nmol cysteine sulphinate/g protein. The cysteate concentration was not increased above the detection limit. Injection of a toxic dose of cysteine sulphinate elevated cysteine sulphinate concentration in the frontomedial cortex (a region consistently injured by cysteine sulphinate) almost three orders of magnitude more than that observed after cysteine administration. Taken together, these results strongly suggest that neither cysteine sulphinate nor cysteate alone mediate cysteine toxicity. Possible candidates for such a role include cysteine carbamate and S‐sulpho‐cysteine. Another alternative is that the sulphydryl group of cysteine sensitizes the NMDA receptor complex and thereby enhances the effect of glutamate and/or some other endogenous NMDAmimetics.
Covariations Between Hippocampal Mossy Fibres and Working and Reference Memory in Spatial and Non‐spatial Radial Maze Tasks in Mice
Authors: Crusio Wim E. , Schwegler Herbert , Brust Ingrid 
Published: April 2006

AbstractMale mice from nine inbred mouse strains were tested at the age of 3 months in either a spatial or a non‐spatial version of the radial maze. Only four out of eight arms contained food rewards, permitting simultaneous assessment of working and reference memory in both situations. Other animals from the same strains were processed histologically to estimate the strain‐specific extents of the mossy fibre projections. No significant between‐task correlations were obtained for either working or reference memory. However, measures of working and reference memory correlated with each other within tasks. This suggests that these concepts may perhaps not be validly used in the mouse. Large, positive correlations of the size of the intra‐ and infrapyramidal mossy fibre projection with both working and reference memory were obtained in the spatial radial maze task, but not in the non‐spatial one. We conclude that heritable variations of the hippocampal intra‐ and infrapyramidal mossy fibre projection influence processes related to spatial learning capabilities in radial mazes.
Interleukin‐6 and Transforming Growth Factor‐β1 mRNAs are Induced in Rat Facial Nucleus Following Motoneuron Axotomy
Authors: Kiefer Reinhard , Lindholm Dan , Kreutzberg Georg W. 
Published: April 2006

AbstractTransection of the rat facial nerve leads to a rapid activation of both astrocytes and microglia around axotomized motoneurons. The factors involved in glial activation in vivo are poorly defined but cytokines have been implicated as major regulators of glial activity in vitro. In the present study we have investigated the expression of cytokine mRNAs in the axotomized facial nucleus that might be involved in glial activation. Eight hours after axotomy unilateral transection of the facial nerve had already induced a rapid accumulation of interleukin (IL)‐6‐mRNA, with a peak at 24 hours. No IL‐6 mRNA was detected on the unoperated control side. Transforming growth factor (TGF)‐β1 mRNA was detected at low levels in the normal facial nucleus, increasing to three times the normal level 2 days after axotomy. After day 7 TGF‐β1 mRNA levels gradually declined, with a second minor peak 21 days after axotomy. In situ hybridization experiments, 4 and 21 days after axotomy, localized TGF‐β1 mRNA to activated microglial cells around regenerating motoneurons, as well as probably some astrocytes. Motoneurons did not express TGF‐β1 mRNA. TGF‐β3 was found to be normally expressed in the facial nucleus but was not regulated by axotomy. No mRNA for IL‐1, tumour necrosis factor‐α or interferon‐γ was found in the regenerating facial nucleus at any point in time. Our data indicate that IL‐6 might act as an early activating signal for glial cells in response to motoneuron axotomy, and that TGF‐β1 expressed by activated glial cells might provide a long‐lasting negative feedback signal to control glial activation.
High External Potassium Induces an Increase in the Phosphorylation of the Cytoskeletal Protein MAP2 in Rat Hippocampal Slices
Authors: Díaz‐Nido Javier , Montoro Rafael J. , López‐Barneo José , Avila Jesús 
Published: April 2006

AbstractDepolarization induced in rat hippocampal slices by a high concentration of extracellular K+ leads to an increase in the phosphorylation of microtubule‐associated protein MAP2. The comparison of the major phosphopeptides derived from in situ and in vitro phosphorylated MAP2 suggests the implication of calcium‐dependent protein kinases, including calcium/calmodulin‐dependent protein kinase type II and protein kinase C, in the up‐phosphorylation of MAP2. In particular, a peptide containing the tubulin‐binding domain of the MAP2 molecule may be phosphorylated by protein kinase C. As the association of MAP2 with the cytoskeleton may be regulated by phosphorylation, we suggest that changes in the phosphorylation level bf MAP2 might be involved in synaptic remodelling in hippocampal neurons.
Cytokines Regulate L‐Arginine‐Dependent Cyclic GMP Production in Rat Glial Cells
Authors: Simmons Martha L. , Murphy Sean 
Published: April 2006

AbstractWe have previously demonstrated that primary astrocyte cultures from neonatal rat cortex and C6 glioma cells express a calcium‐independent nitric oxide synthase (NOS) on induction with bacterial endotoxin (lipopolysaccharide, LPS). One hypothesis regarding the mechanism of the LPS induction is that it causes release of cytokines from these cells which then induce the enzyme directly. Such cytokine induction of NOS has been demonstrated in many extraneural cell types. l‐Arginine‐dependent increases in cyclic GMP correlate with smaller increases in accumulation of nitrite, the major oxidation product of nitric oxide, and hence can serve as a more sensitive measure of nitric oxide production. Here we provide evidence that interferon‐γ (IFN‐γ), interleukin (IL)‐1β and tumour necrosis factor‐α induce l‐arginine‐dependent cyclic GMP synthesis in C6 cells and that a combination of IFN‐γ and IL‐1β induce l‐arginine‐dependent cyclic GMP synthesis in astrocyte cultures, indicating that these cytokines induce NOS. In both cell types the induction by cytokines was less sensitive to inhibition by dexamethasone, IL‐10 and IL‐4 than was induction by LPS. These data suggest that cytokines can also induce a NOS in glial cells and that the mechanism of this induction may be more direct than that of LPS, since it is less sensitive to modulation by immunosuppressors. Due to the close associations of astrocytes with neurons and microvasculature, cytokine‐induced NOS could have potentially important pathophysiological effects in the central nervous system.