摘要:

AbstractWe have isolated a cDNA coding for the larger isoform of the rat brain 2′,3′ ‐cyclic nucleotide 3′ ‐phosphodiesterase (CNP2), a protein associated with myelination in the central nervous system (CNS). The complete 420 amino acid sequence was deduced from the nucleotide sequence of the cDNA. Sequence comparisons show that rat CNP shares 96% homology with mouse, 84% with bovine, and 86% with human CNP. Errors in the published sequence of rat CNP1 have now been corrected. Comparisons with other proteins reveal several interesting conserved motifs, including two leucine repeat heptads, and two consensus motifs for phosphorylation in the N‐terminal domain of CNP2.© 1994 Wil

ISSN:0360-4012    

DOI:10.1002/jnr.490380302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAlzheimer's disease (AD) is characterized by the deposition of amyloid in the extracellular and intracellular compartments of the cerebral cortex. The extracellular amyloid consists of a protein (βA4) which is derived from a larger precursor, the amyloid protein precursor (APP). Several studies have implicated APP in the regulation of neurite outgrowth during development, although the precise function of APP remains unknown. To examine the role of APP in the regulation of neutrite outgrowth from hippocampal neurons, an explant culture system was developed. Explants of E18 mouse hippocampus were found to extend neurites when co‐cultured with explants of E18 mouse septum. This finding demonstrated that the septum can release a neurite outgrowth‐promoting factor (NOPF). As nerve growth factor (NGF) was also able to stimulate neurite outgrowth from the hippocampal explants, this suggested that the NOPF might be NGF. Immunoprecipitation of NGF from septal conditioned medium using a specific monoclonal antibody (27/21) completely blocked the neurite outgrowth‐promoting effect, supporting this conclusion. Concomitant with its ability to stimulate neurite outgrowth, NGF stimulated the release of APP from the hippocampal explants. As previous studies have suggested that the binding of APP to heparan sulfate proteoglycans (HSPGs) in the extracellular matrix might be an important step in the regulation of neurite outgrowth by NGF, we examined the effect of APP on neurite outgrowth from dissociated hippocampal cells cultured on various protein substrates. When cells were cultured on a substrate of APP and HSPG, neurite outgrowth was markedly stimulated. No stimulation of neurite outgrowth was seen when neurons were cultured on substrates of either APP or HSPG alone. The results suggest that secreted forms of APP may be involved in stimulating neurite outgrowth from hippocampal neurons and that interactions between APP and HSPG may be important for a neurite outgrowth‐promoting function. © 1994 Wiley

ISSN:0360-4012    

DOI:10.1002/jnr.490380303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTotal deficiency of hypoxanthine phosphoribosyl‐transferase (HPRT) in humans causes the neurological disorder Lesch‐Nyhan syndrome. The HPRT gene is expressed at basal levels in all tissues but at higher levels in the brain, the relevance and mechanism of which is unknown. To determine ifcis‐acting DNA elements play a role in the tissue‐differential pattern of expression, we generated transgenic mice carrying different sequences of the human HPRT (hHPRT) promoter fused to the bacteriallacZgene. We show that a 1.6 kb fragment of the hHPRT promoter contains essential information to direct β‐galactosidase expression preferentially to the basal ganglia, cerebral cortex, hippocampus, and several other areas of the forebrain. At least two elements within the 1.6 kb fragment appear to be required for neuronal expression. A 182 bp element (hHPRT‐NE) represents one of those sequences and is involved not only in confering neuronal specificity but also in repressing transgene expression in non‐neuronal tissues. These studies provide molecular insight into the mechanism of increased HPRT expression in the brain. © 1994

ISSN:0360-4012    

DOI:10.1002/jnr.490380304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractCultures consisting primarily of O‐2A progenitor cells and immature oligodendrocytes with a few microglia and astrocytes were obtained by shaking primary cultures from neonatal rat brain after 12‐‐14 days in vitro. Addition of 50 μg/ml exogenous Neu‐NAcα2‐3Galβ1‐1′ ceramide (GM3 ganglioside) to the cultures resulted in an increase in the number and thickness of cell processes that stained intensely for sulfatide and galactocerebroside (galC) in comparison to control cultures without added GM3. The treated cultures also contained fewer astrocytes than control cultures as revealed by immunostaining for glial fibrillary acidic protein (GFAP). Cells that immunostained for both GFAP and sulfatide/galC were very rare in control cultures but were frequently seen in the GM3‐treated cultures, suggesting that these may represent cells changing their direction of differentiation away from type II astrocytes toward oligodendrocytes under the influence of GM3. These effects on the developing rat oligodendrocytes were specific for GM3 ganglioside and were not produced by adding GM1, GM2, GD3, or GD1a to the cultures. Lactosyl ceramide and neuraminyl lactose were also ineffective. When control cultures were initially plated on polylysine and incubated with [14C]galactose, GD3 was the principal labeled ganglioside. However, as the control cells differentiated over time in culture without the addition of exogenous GM3 and produced increasing amounts of myelin‐related components, the incorporation of [14C]galactose into endogenous GM3 increased to become the predominant labeled ganglioside by 6 days after plating. Metabolic labeling of the GM3‐treated oligodendrocytes with [14C]galactose revealed increased incorporation into galC and sulfatide in comparison to control cultures, but a decreased labeling of endogenous GM3. Similarly, incorporation of an amino acid precursor into the myelin‐associated glycoprotein (MAG) was increased by GM3 treatment, but incorporation into myelin basic protein (MBP) was not affected. Although the overall effect of added GM3 was to decrease the phosphorylation of most proteins in the oligodendrocytes, including MBP, GM3 enhanced the phosphorylation of MAG. These findings indicate that GM3 ganglioside has an important role in the differentiation of cells of the O‐2A lineage toward myelin production, since differentiation is associated with increased metabolic labeling of endogenous GM3 in control cultures and is enhanced by the addition of exogenous GM3. © 1994 Wiley‐Liss, Inc.This article is a US Government work and, as such, is in the public domain in

ISSN:0360-4012    

DOI:10.1002/jnr.490380305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe aim of this study was to show whether reduction or loss of cortical cholinergic activity results in any particular change in the expression of the proto‐on‐cogenes c‐fos and/or c‐jun. To produce cortical cholinergic hypofunction, the monoclonal antibody, 1921gG, to the low‐affinity nerve growth factor receptor p75NGFRcoupled to a cytotoxin, saporin, was used as an efficient and selective immunotoxin for cholinergic neurons in rat basal forebrain. Brain sections of adult rats that had received an intracerebro‐ventricular injection of 4 μg of the 1921gG‐saporin were subjected to in situ hybridization using oligonucleotides to detect c‐fos and c‐jun mRNA. Autoradiographs obtained were evaluated by quantitative image analysis. Seven days following injection of the immunotoxin there was a dramatic loss in acetylcholinesterase staining in frontal, parietal, piriform, temporal, and occipital cortices, hippocampus, and olfactory bulb, but not in the striatum and cerebellum. In situ hybridization revealed a considerable increase in the level of c‐fos mRNA in the lateral septum following the cholinergic lesion, whereas in the medial septum both c‐fos and c‐jun mRNA were elevated. Immunolesioning led to a distinct and specific increase in the level of c‐jun but not c‐fos mRNA in the parietal and occipital cortex that was restricted to cortical layer IV.These data suggest that reduced cortical cholinergic activity differentially regulates expression of c‐fos/c‐jun genes in distinct cortical regions of the r

ISSN:0360-4012    

DOI:10.1002/jnr.490380306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractIn rat muscles, AChE activity drops rapidly after denervation, and the patterns of AChE molecular forms in slow and fast muscles differ considerably. Both observations imply that muscle AChE is regulated by the motor nerve. In order to obtain a better insight into the underlying mechanism, AChE regulation in rat muscles was examined on the level of its catalytic subunit mRNA using northern blot analysis. The level of two AChE transcripts (2.4 and 3.2 kb) was much higher in the fast sternomastoid (STM) than in the slow soleus muscle, which explains the difference in AChE activity between the two types of muscles. Expression of AChE mRNA in the extrajunctional region of STM muscle is fairly high so that little difference in the level of AChE mRNAs was observed in comparison to the region rich in the neuromuscular junctions. This indicates that very high AChE activity in the neuromuscular junctions is achieved by unique posttranslational modifications and cellular processing of AChE enhancing stability of the junctional in comparison to the extrajunctional AChE. Denervation as well as botulinum toxin evoked paralysis of STM muscle caused rapid decline of AChE transcripts to almost undetectable levels both in the junctional and extrajunctional regions. The low level of AChE mRNA is therefore largely responsible for low AChE activity in denervated rat muscles. It seems that either muscle activity and/or quantal ACh release enhance the level of AChE mRNA in the junctional as well as extrajunctional regions. In rat muscles, extrajunctional mRNA level of the catalytic subunit of AChE is neurally regulated in exact opposite fashion from that of acetylcholine receptor subunits. © 1994 Wiley‐Liss, I

ISSN:0360-4012    

DOI:10.1002/jnr.490380307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractPrevious studies have documented that cultured Schwann cells require serum‐containing medium to respond maximally to mitogens. We now report that Schwann cells are able to proliferate to a mitogenic response in a serum‐free defined medium termed oligodendrocyte defined media (ODM). Glucocorticoids are the essential component of ODM which allow Schwann cell proliferation in the serum‐free medium. Charcoal treatment of the fetal calf serum decreases the mitogenic potency of the axolemma‐enriched fraction (AEF) by 50%. The addition of 2 μM hydrocortisone to charcoal‐treated fetal calf serum restores 75% of the lost mitogenicity. These observations are consistent with the view that glucocorticoids present in fetal calf serum are potent co‐mitogens essential for AEF‐induced Schwann cell proliferation. The synthetic glucocorticoid, dexamethasone, is a more potent co‐mitogen than hydrocortisone, with a maximal effect at concentrations less than 10 nM. In contrast, other steroids including aldosterone, progesterone, testosterone, and 17β‐estradiol have no effect on enhancing the mitogenic response of Schwann cells to the AEF. The glucocorticoid antagonists RU 486 and dehydroepiandrosterone (DHEA), but not the antiestrogenic compound tamoxifen, block AEF‐induced Schwann cell proliferation. These results suggest that glucocorticoid‐induced Schwann cell proliferation is mediated through a glucocorticoid receptor (GR) mechanism. We detected immunoreactivity to the GR in the cytoplasm, but not in the nuclei of Schwann cells grown in ODM lacking dexamethasone. The addition of 100 nM dexamethasone to these cultures resulted in immunoreactivity in the nucleus. This data suggests that glucocorticoids working through the GR are potent co‐mitogens for Schwann cell proliferatio

ISSN:0360-4012    

DOI:10.1002/jnr.490380308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe goal of this study was to examine the possible production of vasoactive factors by astrocytes. We consistently observe that rat astroglial cells in suspension produce marked relaxation when added to precontracted rings of intact (but not endothelium‐denuded) rabbit basilar artery. The ultimate mediator of this relaxation was endothelium‐derived nitric oxide whose synthesis is activated by an as yet unidentified factor(s) produced tonically by astrocytes. The factor is relatively stable, and is not arachidonate, or a product of cyclooxygenase or P450 metabolism. Based upon studies with selective inhibitors, the factor appears to result from 12‐ or 15‐lipoxygenase metabolism, the products of which are known to be vasoactive. In a separate series of experiments, astrocyte‐conditioned medium stimulated the production of citrulline from L‐arginine by nitric oxide synthase in bovine aortic endothelial cells. The possible significance for central nervous system (CNS) pathophysiology of an astrocyte‐derived vasodilator is discussed. © 1994 W

ISSN:0360-4012    

DOI:10.1002/jnr.490380309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractPrimary cultures of cerebral cortical GABA‐ergic neurons growing on top of a preformed layer of astrocytes (co‐cultures) were incubated with [1‐13C]glucose and exposed to a low oxygen atmosphere (2% O2) for 17 hr.13C,1H, and13P nuclear magnetic resonance (NMR) spectroscopy was performed on perchloric acid (PCA) extracts of cells and of media collected from these cultures. In the control groups incorporation of13C label into glutamine, citrate, and lactate could be demonstrated in both cell extracts and culture media. Labeled GABA and glutamate were only observed in cell extracts. During hypoxia high energy phosphates decreased but lactate production and glucose consumption increased. There was a decreased amount of citrate and glutamine in cell extracts and media of the hypoxic co‐cultures. There was a change in distribution of the13C label within the GABA molecule, with an increase of labeling in the C‐2 position. This change in13C distribution was not found in glutamine present in the media where it is a precursor for GABA in neurons. Instead a decrease in the corresponding C‐4 position was observed. These results suggest that energy depletion during hypoxia leads to reduced export from the astrocytic tricarboxylic acid (TCA) cycle as demonstrated by a decreased amount of citrate and changed distribution of13C in glutamine. The change in the distribution of label in GABA from cell extracts as compared to glutamine in the medium may indicate that neurons are synthesizing GABA using precursors supplied from their own TCA cycle and not from precursors supplied by

ISSN:0360-4012    

DOI:10.1002/jnr.490380310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe growth‐associated protein B‐50 (GAP‐43) is thought to play a major role in the development and regeneration of neurons. The participation of B‐50 in neuronal plasticity is well documented, especially for monoaminergic systems. However, such an important role for B‐50 in GABAergic systems has not been substantiated to date. This study was performed to obtain detailed information about the identity of B‐50 immunopositive axons and terminals in the cerebellum and to test the involvement of this protein during plastic changes as observed in the projections of GABAergic Purkinje cells to the lateral vestibular nucleus (LVN). For this purpose mutant mice with specific cerebellar cell loss were used. Weaver mutants (B6CBAwv/wv), PCD‐mutants (B6C3Fepcd/pcd), and their corresponding wild‐type mice were investigated with immunocytochemical and immunoblot procedures at the age of 8‐‐23 days and 5‐‐6 months using polyclonal and monoclonal antibodies to B‐50. Substantial differences in B‐50 distribution wee detected between normals and mutants and between young and adult animals. These results demonstrate that the labeling of B‐50 is mainly related to the outgrowth of parallel fibers and to a minor degree on the ingrowth of non‐GABAergic cerebellar afferents. There was no immunocytochemical indication that B‐50 is related to Purkinje cells or accompanies the plasticity of the GABAergic innervation o

ISSN:0360-4012    

DOI:10.1002/jnr.490380311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY