bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of verapamil on the release of different neurotransmitters
Authors: Sitges María , Reyes A. 
Published: January 2005

AbstractThe effect of verapamil on resting and depolarization‐induced monoamine release was investigated in rat hippocampal synaptosomes prelabeled with [3H]‐5‐hydroxytryptamine (HT) or [3H]‐norepinephrine (NE) and rat striatal synaptosomes prelabeled with [3H]‐dopamine (DA). Verapamil (50 μM) completely abolishes high K+‐induced [3H]‐NE release, but paradoxically facilitates high K+‐induced [3H]‐5‐HT and [3H]‐DA release. All these high K+‐evoked responses were Ca2+ dependent. Verapamil does not modify [3H]‐NE baseline release, but increases dose dependently [3H]‐5‐HT and [3H]‐DA baseline release. Verapamil (10 μM, for 5 min) increases endogenous DA release (70%) and endogenous 5‐HT release (40%) independently on the presence of external Ca2+. The total amount of these monoamines (released plus retained by the preparation) and their metabolites (DOPAC and 5‐HIAA) was similar in control and verapamil‐treated synaptosomes. Verapamil displaces [3H]‐spiroperidol specific binding (Ki of 2.4 × 10−6M) and [3H]‐SCH‐23390 specific binding (Ki of 9 × 10−6M) from striatal synaptosomal membranes, and [3H]‐5‐HT specific binding (Ki of 3 × 10−5M) from hippocampal synaptosomal membranes. It is concluded that in addition to the Ca2+ antagonistic properties of verapamil on the Ca2+‐dependent, depolarization‐induced release of some neurotransmitters [gamma aminobutyric acid (GABA and NE)], another mechanism probably mediated by presynaptic receptors underlies the effects of verapamil on DA and 5‐HT release from discrete brain regions. © 1995 Wiley‐Liss, Inc.
Evidence that secretase cleavage of cell surface Alzheimer amyloid precursor occurs after normal endocytic internalization
Authors: Refolo L. M. , Sambamurti K. , Efthimiopoulos S. , Pappolla M. A. , Robakis N. K. 
Published: January 2005

AbstractThree different treatments (methylamine, colchicine, and 18°C temperature block), known to disrupt normal endocytic internalization, significantly reduced the secretory cleavage of cell surface‐derived Alzheimer amyloid precursor (APP) in non‐transfected C6 cell cultures. Conversely, treatments with methylamine or colchicine had no significant effect on the secretion of total APP. Treatment of these cells with the lysosomotropic amine chloroquine resulted in a significant increase in the levels of both cell surface full‐length APP and cell surface‐derived secreted nexin II (NXII). Immunofluorescence analysis of C6 glioma cells transfected with APP751 indicated that under normal conditions, cell surface APP was internalized, and within 30 minutes was localized in discrete intracellular vesicles. These vesicles contained the endocytic tracer Texas red‐conjugated ovalbumin and probably represented late endosomes or lyso‐somes. However, treatment of the transfected C6 cultures with methylamine or colchicine prevented localization of cell surface APP in intracellular vesicles, suggesting that these treatments altered the normal intracellular trafficking of cell surface‐derived APP. Both the biochemical and immunofluorescence data are compatible with the suggestion that inhibition of normal endocytic internalization reduces the secretory cleavage of cell surface APP. Furthermore, our results suggest that following internalization, cell surface APP is cleaved by secretase(s) and secreted or routed to the lysosomes where it is degraded. © 1995 Wiley‐Liss, Inc.
Cloning of rat grp75, an hsp70‐family member, and its expression in normal and ischemic brain
Authors: Massa Stephen M. , Longo F. M. , Zuo J. , Wang S. , Chen J. , Sharp F. R. 
Published: January 2005

AbstractFollowing metabolic stress a variety of gene products are induced in cells in the brain, some of which may protect the tissue from subsequent stresses. The heat shock proteins (hsps), in particular hsp70, have been widely studied in this context, but evidence for the involvement of known hsps in protection of the CNS is inconclusive. We have therefore undertaken the search for other stress‐induced proteins which may mitigate ischemic injury. Beginning with degenerate RT‐PCR, we have isolated a rat‐brain cDNA encoding a protein highly similar to human grp75, a mitochondrial member of the hsp 70‐family of stress proteins. It is also highly similar to two non‐mitochondrial proteins; mortalin, a senescence‐related gene product, and pbp74, a protein implicated in B‐cell peptide processing. Sequence structure and phylogenetic analyses predict mitochondrial localization and induction by a calcium ionophore and glucose deprivation in PC12 cells support its identification as rat grp75. In situ analysis of normal brain reveals an unusual distribution, with very high expression in neurons of the basal forebrain, reticular and subthalamic nuclei, globus pallidus, amygdala and elsewhere. grp75‐mRNA is upregulated following focal brain ischemia in a distinctive fashion. When the degree of injury is small, induction occurs in the area of injury, similar to the pattern observed for hsp70. However, when the injury is extensive, hsr is upregulated in neurons outside the ischemic area. The induction of grp75 may represent a sensitive marker of metabolically compromised tissue. © 1995 Wiley‐Liss, Inc.
Changes in neuronal mRNAs induced by a local inflammatory reaction
Authors: Lu X. , Richardson P. M. 
Published: January 2005

AbstractInjection of Corynebacterium parvum into the rat dorsal root ganglion has previously been shown to cause an inflammatory reaction dominated by macrophages and to enhance regeneration of the central axons of primary sensory neurons. Here, neuronal mRNAs that are modified by nerve transection were analyzed by in situ hybridization following injection of C. parvum into the dorsal root ganglion. Neuronal concentrations of mRNAs for the growth‐associated protein (GAP‐43) and the immediate early gene c‐jun were increased by a local inflammatory response just as after axotomy. The concentration of mRNA for calcitonin gene‐related peptide (CGRP) was also increased in a constant subpopulation of sensory neurons after injection of C. parvum in contrast to its decrease following axotomy. The results are consistent with the hypothesis that some of the responses to sensory neurons to axotomy are sustained by macrophages which accumulate within the dorsal root ganglion after nerve injury. © 1995 Wiley‐Liss, Inc.
Bacterially expressed F1‐20/AP‐3 assembles clathrin into cages with a narrow size distribution: Implications for the regulation of quantal size during neurotransmission
Authors: Ye W. , Lafer E. M. 
Published: January 2005

AbstractF1‐20/AP‐3 is a synapse‐specific phosphoprotein. In this study we characterize the ability of bacterially expressed F1‐20/AP‐3 to bind and assemble clathrin cages. We find that both of two bacterially expressed alternatively spliced isoforms of F1‐20/AP‐3 can bind and assemble clathrin as efficiently as preparations of F1‐20/AP‐3 from bovine brain. This establishes that the clathrin assembly activity found in F1‐20/AP‐3 preparations from brain extracts is indeed encoded by the cloned gene for F1‐20/AP‐3. It also demonstrates that posttranslation modification is not required for activation of the clathrin binding or assembly function of F1‐20/AP‐3. Ultrastructural analyses of the clathrin cages assembled by bacterially expressed F1‐20/AP‐3 reveals a strikingly narrow size distribution. This may be important for the regulation of quantal size during neurotransmission. We also express the 33 kD NH2‐terminus of F1‐20/AP‐3 in E. coli, and measure its ability to bind to clathrin triskelia, to bind to clathrin cages, and to assemble clathrin triskelia into clathrin cages. It has been suggested that the 33 kD NH2‐terminus of F1‐20/AP‐3 constitutes a clathrin binding domain. We find that the bacterially expressed 33 kD NH2‐terminus of Fl20/AP‐3 binds to clathrin triskelia, fails to bind to preassembled clathrin cages, and is not sufficient for clathrin assembly. The finding that the 33 kD NH2‐terminus of F1‐20/AP‐3 binds to clathrin triskelia but fails to assemble clathrin triskelia into clathrin cages is consistent with the published proteolysis studies. The finding that the 33 kD NH2‐terminus of F1‐20/AP‐3 fails to bind to clathrin cages is novel and potentially important. It is clear from these experiments that the 33 kD NH2‐terminus of F1‐20/AP‐3 is sufficient to carry out some aspects of clathrin binding; however it appears that defining the regions of the protein involved in clathrin binding and assembly may be more complex than originally anticipated. © 1995 Wiley‐Liss, Inc.
Abnormal expression and glycosylation of the large and small isoforms of myelin‐associated glycoprotein in dysmyelinating quaking mutants
Authors: Bartoszewicz Z. P. , Noronha A. B. , Fujita N. , Sato S. , Bö L. , Trapp B. D. , Quarles R. H. 
Published: January 2005

AbstractThe relative expression of large (L) and small (S) iso‐forms of the myelin‐associated glycoprotein (MAG) and their glycosylation were compared in developing spinal cord of quaking and control mice. Using anti‐sera specific for L‐ and S‐MAG, respectively, it was shown that S‐MAG is the principal isoform in quaking mice at all ages between 13 and 72 days, although L‐MAG was just detectable by western blotting at the early ages. Both L‐ and S‐MAG have higher apparent molecular weights in quaking mice than in controls. Experiments involving lectin binding and glycosidase treatment demonstrated that the higher molecular weight of MAG in the quaking mutant was due to a higher content of N‐acetyineuraminic acid residues linked α2‐3 to galactose as well as to more branching of oligosaccharide moieties indicated by a higher content of subterminal galactose residues. The total sialic acid measured by HPAE‐chromatography in purified quaking MAG was 40% higher than in control MAG. By contrast, quaking MAG contained less of the adhesion‐related, HNK‐1 carbohydrate epitope. Another difference was that a lower molecular weight form of MAG with predominantly high mannose oli‐gosaccharides was prominent in young quaking mice, but not in controls. The abnormalities of MAG expression related to splicing of its mRNA and glycosylation may contribute to the myelin pathology in quaking mutants. © 1995 Wiley‐Liss, Inc.
Oxystdrol (7β‐hydroxycholestesteryl‐3‐oleate) promotes serotonergic reinnervation in the lesioned rat spinal cord by reducing glial reaction
Authors: Giménez y Ribotta M. , Rajaofetra N. , Morin‐Richaud C. , Alonso G. , Bochelen D. , Sandillon F. , Legrand A. , Mersel M. , Privat A. 
Published: January 2005

AbstractIn the present study, following previous experience with electrolytic lesion of the rat brain, and subsequent reduction of reactive gliosis with 7b̃‐hydroxycholesterol derivatives (Bochelen et al.: Neuroscience 51:827‐834, 1992), we have performed a hemisection of the spinal cord in adult rats and investigated the influence of 7b̃‐hydroxycholesteryl‐3‐oleate (oxysterol) on the intensity of the astrocytic reaction and the axonal regeneration. We have shown here that local administration of liposomes containing this oxysterol reduced the intensity of the astroglial reaction on the sectioned side, as seen with immunocytochemical detection of glial fibrillary acidic protein (GFAP) and by in situ hybridization with a specific RNA probe. Moreover, radioautographic evaluation of astrocyte proliferation with tritiated thymidine evidenced a reduction of the astrocyte labelling index. In addition, double immunocytochemical detection of GFAP and polysialylated neural cell adhesion molecule (E‐NCAM) revealed a decrease of the expression of this molecule in reactive astrocytes of the treated animals. Finally, immunocytochemical detection of serotonin (5HT) was determined in the raphespinal projections, which constitute a major descending system. In treated animals, serotonergic axons originating from the intact side reinnervated the dorsal horn of the sectioned side, below the hemisection.These results demonstrate that 7b̃‐hydroxycholesteryl‐3‐oleate can reduce the astrocytic reaction following spinal cord injury, promoting the serotonergic reinnervation of a denervated territory. © 1995 Wiley‐Liss, Inc.
A serum‐free, pyruvate‐free medium that supports neonatal neural/glial cultures
Authors: Martin F. C. , Wiley C. A. 
Published: January 2005

AbstractTissue culture media with serum generally cause excessive astrocyte proliferation in neonatal brain cultures, and often fail to support neonatal neurons. Published serum‐free media for brain cultures contain sodium pyruvate, which interferes with lactate dehydrogenase (LDH) assays for cell death. We wanted to use neonatal neural‐glial cultures in LDH assays while avoiding astrocyte proliferation, so we developed a serum‐free medium without sodium pyruvate. Our initial medium was based on that of Romijn et al. (J Neurosci Methods 23:75‐83, 1988), testing selected additives. Cell survival in 8‐10‐day‐old cultures was measured using 3‐[4,5‐Dimethylthiazol‐2‐yl]‐2,5‐diphenyltetrazolium bromide (MTT). N‐acetylcysteine, citrate, superoxide dismutase, ascorbate, supplemental amino acids, and high levels of transferrin improved survival. The optimized medium supported neonatal brain cells in reaggregates or in monolayers of 400 cells/mm2 for several weeks with large, healthyappearing neurons and very little astrocyte proliferation. Neurons stained strongly for the neuronal marker class III b̃‐tubulin and the synapse marker synaptophysin. Electron microscopy of reaggregate cultures demonstrated abundant neurons with synapses in a dense neuropil. This medium will be useful for various in vitro applications, especially those using LDH assays or requiring the use of neonatal cells. © 1995 Wiley‐Liss, Inc.
Expression of receptor protein tyrosine phosphatase‐σ (RPTP‐σ) in the nervous system of the developing and adult rat
Authors: Wang H. , Yan H. , Canoll P. D. , Silvennoinen O. , Schlessinger J. , Musacchio J. M. 
Published: January 2005

AbstractThe expression of receptor protein tyrosine phosphatase‐σ (RPTP‐σ) mRNA during rat development was examined by Northern blot and in situ hybridization analyses. Northern blot analysis revealed that the two transcripts (5.7 kb and 6.9 kb) had different spatial and temporal patterns of expression. The 6.9‐kb transcript was more abundant during embryonic development, whereas the 5.7‐kb transcript was more abundant during postnatal development and in the adult. In situ hybridization revealed that RPTP‐σ mRNA was widely expressed throughout the central and peripheral nervous system during embryonic development. Very high levels were seen in the ventricular zone, subventricular zone, cortex, dorsal root ganglia, cranial nerve ganglia, olfactory epithelium, and retina. During postnatal development the level of expression decreased in most brain regions. However, high levels continued to be seen in the hippocampus. Emulsion autoradiography revealed that the majority of RPTP‐σ mRNA is expressed in neurons. Northern analysis showed that cultured glial cells expressed the 6.9‐kb transcript, but not the 5.7‐kb. RPTP‐σ mRNA expression profiles were clearly distinct from those of leukocyte antigen‐related protein (LAR), a closely related RPTP. The spatiotemporal pattern of RPTP‐σ mRNA expression indicates that RPTP‐σ may play a role in the development of the nervous system. © 1995 Wiley‐Liss, Inc.
Glia‐to‐axon communication: Enrichment of glial proteins transferred to the squid giant axon
Authors: Sheller R. A. , Tytell M. , Smyers M. , Bittner G. D. 
Published: January 2005

AbstractThe transfer of newly synthesized proteins from the glial sheath into the axon is a well‐documented process for the squid giant axon. In this study, we used a novel approach to separate the transferred glial proteins (TGPs) from the endogenous axoplasmic proteins of the squid giant axon. Axoplasm, containing radiolabelled TGPs, was extruded as a cylinder and immersed in an intracellular buffer. After 1–30 min, the TGPs were enriched in the intracellular buffer, because they were eluted from the axoplasm into the intracellular buffer much faster than the endogenous axoplasmic proteins. Most of the TGPs enriched in the intracellular buffer did not pellet when centrifuged at 24,000 g for 20 min and were susceptible to protease digestion without the addition of Triton X‐100. Additionally, transmission electron microscopic autoradiography of intact axons, containing radiolabelled TGPs, suggested that most TGPs were not associated with vesicular organelles within the axon. We conclude that most of the TGPs are not contained within vesicles in the axoplasm of the squid giant axon, as would be expected if the mechanism of glia‐to‐axon transfer were conventional exocytosisendocytosis or microphagocytosis. © 1995 Wiley‐Liss, Inc.
Membrane properties of cultured glial cells obtained mechanically or by enzymatic dissociation: Differential alterations by gangliosides
Authors: Bouchon B. , Petegnief V. , Rebel G. 
Published: January 2005

AbstractRat astroglial cells were obtained either mechanically or by enzymatic dissociation and some properties of the primary and secondary cultures were studied. Differences in the ganglioside amount, taurine uptake, membrane fluorescence anisotropy, or their respective modulation by total brain gangliosides confirmed that although the two types of cultures are morphologically similar, they are biochemically distinct. © 1995 Wiley‐Liss, Inc.
Notochord and floor plate stimulate oligodendrocyte differentiation in cultures of the chick dorsal neural tube
Authors: Trousse F. , Giess M. C. , Soula C. , Ghandour S. , Duprat A.‐M. , Cochard P. 
Published: January 2005

AbstractThe regionalization of oligodendrocyte potentialities and the cellular interactions leading to the expression of the oligodendrocyte phenotype have been analyzed in the embryonic chick spinal cord. Dorsal and ventral regions of the spinal cord of 4‐day‐old embryos (E4) were cultivated separately. Oligodendrocyte differentiation was monitored at various times after explantation, using specific oligodendrocyte markers. After 2 weeks, several hundreds of differentiated oligodendrocytes were invariably observed in ventral cultures whereas significant numbers of oligodendrocytes failed to develop in dorsal spinal cord cultures. However, the E7 dorsal spinal cord was found to produce large numbers of oligodendrocytes, indicating that the ventral restriction of oligodendrocyte potentialities is transient. To test whether ventrally derived signals might influence oligodendrocyte differentiation, E4 dorsal spinal cord microexplants were cocultivated with notochord segments or with floor plate tissue. Numerous oligodendrocytes were found in dorsal explants associated with either tissue, notochord or floor plate, but not in dorsal explants cultivated alone, indicating that cells competent to be induced along the oligodendrocyte phenotype exist in the dorsal spinal cord. These results show that oligodendrocyte differentiation potentialities are initially restricted to the ventral spinal cord and suggest that ventrally derived signals from notochord and floor plate influence oligodendrocyte differentiation in the embryonic spinal cord. © 1995 Wiley‐Liss, Inc.
Chemotaxis and accumulation of nerve growth factor by microglia and macrophages
Authors: Gilad G. M. , Gilad V. H. 
Published: January 2005

AbstractAstrocytes and microglia play a critical role in the reaction of the central nervous system (CNS) to trauma. Although both astrocytes and microglia can produce it, accumulation of immunoreactive nerve growth factor (the prototype neurotrophin important for the survival of several classes of neurons) was observed selectively in cultured microglia and macrophages, rather than in astrocytes. Furthermore, microglia were found to display chemotaxis toward a localized source of nerve growth factor and, as demonstrated by autoradiography, take up extracellular nerve growth factor. These findings suggest that microglia, the brain's own macrophages, participate in the regulation of nerve growth factor availability in a site‐specific manner. This novel function may assume a general importance both in the CNS and the peripheral nervous system at critical times after trauma when this neurotrophin is needed for nerve cell survival. © 1995 Wiley‐Liss, Inc.
Acetyl‐ and butyrylcholinesterase activities in the rat retina and retinal pigment epithelium
Authors: Sánchez‐Chávez G. , Vidal C. J. , Salceda R. 
Published: January 2005

AbstractThe acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) activities in the neural retina and retinal pigment epithelium (RPE) of adult rats were determined. The tissues were extracted with a saline buffer to release the soluble enzymes (S1) and the pellet re‐extracted with Triton X‐100 to detach the membrane‐bound enzymes (S2). Less than 5 % of the cholinesterase activity measured in retina and almost 30% of that assayed in RPE was due to BChE. About 20% and 10% of the AChE in retina and RPE was brought into solution with a saline buffer and the rest with a detergent‐containing buffer. Main AChE molecular forms of 10.5S (hydrophilic G4H), 9.5S (amphiphilic G4 A) and 3.OS (amphiphilic G1A) were identified in retina by subjecting the supernatant S1 to sedimentation analysis in sucrose gradients made with Brij 96. Amphiphilic G4 and G1 AChE were found in S2. Analysis of the soluble fractions obtained from RPE in the gradients made with Brij 96 revealed 16.OS (asymmetric A12), 10.5–10.0S (globular G4H + G4A), 4.5S (G2A), and 3.0S (G1A) AChE forms in S1, whereas G4A, G2A, and G1A enzyme molecules predominated in S2. Our results show that amphiphilic tetramers and monomers of AChE are abundant in neural retina, and enzyme tetramers, dimers, and monomers in RPE. The AChE in the neural retina might be involved in cholinergic actions. The enzyme function in the retinal pigment epithelium remains to be established. © 1995 Wiley‐Liss, Inc.
Differential regulation of bcl‐2, bax, c‐fos, junB, and krox‐24 expression in the cerebellum of Purkinje cell degeneration mutant mice
Authors: Gillardon F. , Bäurle J. , Wickert H. , Grüsser‐Cornehls U. , Zimmermann M. 
Published: January 2005

AbstractPurkinje cell degeneration (pcd) is an autosomal recessive mutation in the mouse characterized by an almost complete loss of cerebellar Purkinje neurons between postnatal days 22 and 28. The pcd gene has not been identified, however, a relationship between activation of specitic genes and cell death has been suggested in other models of neuronal cell death. In the present study we analyzed the expression of several candidate cell death effector genes (bax, c fos, junB, krox‐24) and a cell death repressor gene (bcl‐2) in the cerebellum of pcd homozygotes and wild‐type mice. At postnatal day 22, when Purkinje cells start to degenerate, levels of c fos, junB, and krox‐24 mRNA increased about 5‐fold in mutants. To the contrary, the amount of bcl‐2 mRNA declined and bax transcripts remained unchanged compared to wild‐type animals. Immunoreactivity for c‐Fos and Jun could be detected exclusively in cerebellar Purkinje neurons of pcd mice but not in wild‐types, whereas the number of Bcl‐2 immunopositive Purkinje cells decreased significantly in mutants. Both double labeling experiments and immunostaining of consecutive sections revealed lack of colocalization of Jun with Bcl‐2. These results demonstrate an induction of members of the fos and jun family and a downregulation of antiapoptotic bcl‐2 in cerebellar Purkinje neurons that are destined to die. Fos and Jun transcription factor proteins may be implicated in the regulation of bcl‐2 expression and in the signal cascade leading to Purkinje cell death. © 1995 Wiley‐Liss, Inc.