摘要:

Abstract:The cDNA for Tyr‐Loc, a G protein‐coupled receptor that clearly shows homology to a number of mammalian and fruit fly receptors for biogenic amines, was cloned from the nervous system ofLocusta migratoria. Functional expression of the cloned cDNA was obtained in cultured insect cells, i.e., inSpodopteraSF9 cells using a baculoviral expression system and in stably transformedDrosophilaSchneider 2 (S2) cells. Multiple copies of the receptor expression construct are inserted into the genome of these permanently transformed cells. The expression of the receptor cDNA was driven by the upstream sequences of aBombyx moribaculoviral immediate early gene. Tyramine shows a much higher binding affinity to this receptor than other possible endogenous ligands. It also reduces forskolin‐induced cyclic AMP production in the permanently transformed S2 cells. The pharmacological profile of the Tyr‐Loc receptor is distinct from that of any locust receptor‐type described so far, but it is similar to that of theDrosophilatyramine/octopamine receptor. In the locust CNS, the Tyr‐Loc mRNA is not present in the distal part of the optic lobes but has a widespread distribution in the brain and the ventral

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062387.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:Oligodendroglial cell death in the myelin proteolipid protein (PLP) mutants can be partially rescued by the environment factor(s) supplied by the wild‐type cells in vivo and in vitro. It is possible that the presence of PLP or DM‐20 results in secretion of a factor or factors in the CNS influencing oligodendrocyte development. We previously showed that DM‐20 mRNA is produced in G26 mouse oligodendroglioma, B104 rat neuroblastoma, and B16 mouse melanoma but not in NIH3T3 mouse fibroblast cell lines. Culture supernatants from these cell lines were added to primary glial cell cultures from embryonic day 17 mouse brain. After 4 days, the number of oligodendrocytes present in cultures with supernatants from DM‐20‐producing cells (G26, B104, and B16) was significantly higher than that of control cultures but not with the NIH3T3 supernatant. To investigate more directly whether the PLP gene expression is involved in this process, NIH3T3 cells (nonneural cells) were forced to produce PLP or DM‐20. By addition of the supernatants from the PLP/DM‐20 transformants, the number of oligodendrocytes in the mixed glial cell cultures increased. This clearly demonstrates that the expression of the PLP gene is sufficient for and directly associated with secretion of a factor, which influences the oligodendrocyt

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062396.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:The actions of basic fibroblast growth factor (bFGF) and ciliary neurotrophic factor (CNTF) on tyrosine hydroxylase (TH) gene expression were studied using IMR‐32 neuroblastoma cells. Treatment of these cells with bFGF for 3 days induced the expression of detectable levels of immunoreactive TH protein and TH mRNA. In contrast, CNTF did not affect TH expression unless bFGF was present. In the presence of saturating amounts of bFGF, CNTF increased TH protein and mRNA levels of TH two‐ to threefold over those found in bFGF‐treated cultures. The effects of CNTF on TH expression diminished with increasing culture time, and after 6 days of incubation CNTF no longer enhanced TH levels. The requirement for bFGF as cofactor in the effects of CNTF on TH was specific, as CNTF did not affect TH when it was coadministered with 8‐(4‐chlorophenylthio)‐cyclic AMP, another agent that stimulates TH development in this cell line, and bFGF was not required for CNTF to stimulate the development of choline acetyltransferase. Moreover, cotreatment with bFGF reduced the ability of CNTF to enhance choline acetyltransferase. These results demonstrate that bFGF and CNTF can enhance expression of TH and that bFGF can modify the effects of CNTF on neurotransmitte

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062404.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:We have identified and studied potential ionotropic glutamate receptor genes in pigeon brain. Three cDNA clones exhibit significant amino acid sequence identity to members of a rodent ligand‐gated ion channel family. One of them, GluP‐II, encodes a full‐length AMPA‐sensitive glutamate receptor GluR2 (GluR‐B) homologue, whereas the other two partial clones, designated as GluP‐III and ‐IV, are nearly identical to rodent GluR3 (GluR‐C) and GluR4 (GluR‐D) receptor subunits. Northern analysis demonstrated that the avian genes are widely expressed in the brain. Within the brain regions analyzed by in situ hybridization histochemistry, the three avian GluR subunits showed distinct and regionally specific mRNA expression patterns in the adult. Most of the differences in their expression were observed in cell types of the telencephalon, certain thalamic nuclei, the optic tectum, and the cerebellar cortex. A particularly striking finding was the expression of GluP‐II in Golgi epithelial/Bergmann glial cells. In contrast, Bergmann glial cells in rat cerebellum do not express GluR2 (GluR‐B) subunit genes. Immunoreactivity for a monoclonal sequence‐specific antipeptide antibody was widespread and most prominent in Purkinje cell perikarya and their dendrites, neuronal cell bodies of the ectostriatum, and the deep optic tectum. These results demonstrate the existence of multiple subunits of the ionotropic glutamate receptor channel family in avians. Excitatory amino acid receptor genes appear to be highly con

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062413.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:A full‐length cDNA encoding a major structural glycoprotein of trout CNS myelin (IP1) was cloned and sequenced. The deduced amino acid sequence exhibited a significant structural homology with the P0proteins of rat PNS and shark CNS. Sequence conservation was strongest in the extracellular domain, and it included the position of the two cysteine residues required for stabilization of an immunoglobulin‐like secondary structure as well as those of the singleN‐glycosylation acceptor site. The cytoplasmic domain was shorter by 38 amino acids than those of rat and shark P0and except for a high proportion of basic amino acids did not show any appreciable sequence homology. A single mRNA species of 2 kb was identified by northern blotting, which was expressed in brain tissue but not in liver. By in situ hybridization a selective labeling of myelinating glial cells in the trout CNS and PNS was revealed. The developmental appearance of the IP1 transcript closely coincided with a period of active myelin deposition in most regions of the trout

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062427.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:The effects of nitric oxide (NO)‐generating agents on45Ca2+uptake in rat brain slices and cultured rat astrocytes were studied in the presence of monensin, which is considered to drive the Na+‐Ca2+exchanger in the reverse mode. Sodium nitroprusside (SNP) at>10 µMincreased monensin‐stimulated Ca2+uptake in the slices, although it did not affect high K+‐stimulated Ca2+uptake. Another NO donor, 3‐morpholinosydnonimine, was effective. The effect of SNP was antagonized by hemoglobin (50 µM), a NO scavenger, and mimicked by 8‐bromo‐cyclic GMP (100 µM). In rat brain synaptosomes, SNP increased monensin‐stimulated Ca2+uptake, but it did not affect high K+‐stimulated Ca2+uptake. 8‐Bromocyclic GMP, but not SNP, increased Na+‐dependent Ca2+uptake significantly in synaptic membrane vesicles in the absence of monensin. In cultured rat astrocytes, SNP and 8‐bromo‐cyclic GMP increased Ca2+uptake in the presence of ouabain and monensin, which were required for the Ca2+uptake in the cells. These findings suggest that NO stimulates the Na+‐Ca2+exchanger in neuronal preparations and astrocytes in a

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062437.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:We demonstrate by reverse transcriptase‐polymerase chain reaction and Southern blotting that an immortalized rat oligodendroglial cell line (CG‐4) expresses the non‐N‐methyl‐d‐aspartate (non‐NMDA) glutamate receptor (GluR) genesGluR2–7, KA‐1,andKA‐2and that nonimmortalized cells of the rat oligodendroglial lineage express theGluR1–3, GluR5–7, KA‐1,andKA‐2genes. Lactic dehydrogenase release assays show that both immortalized and nonimmortalized cells of the oligodendroglial lineage are damaged by a 24‐h exposure to 500 µMkainate or 5 mMl‐glutamate, but not by a 24‐h exposure to up to 10 mMα‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA). Damage is prevented by the non‐NMDA GluR channel inhibitor 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione and is also averted if Ca2+is removed from the culture medium. Cyclothiazide, which blocks desensitization of AMPA‐preferring GluRs, increases cytotoxicity of kainate as well as inducing toxicity of AMPA. We conclude that cells of the oligodendroglial lineage express a population of AMPA‐preferring and possibly also kainate‐preferring GluR channels that are capable of mediating Ca2+‐dependent excitotoxicity and that AMPA‐indu

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062442.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:The present article investigates chronic opioid regulation of the stimulatory adenylate cyclase‐coupled prostaglandin E1(PGE1) receptor system in neuroblastoma × glioma (NG108‐15) hybrid cells. Persistent activation of δ‐opioid receptors by morphine (10 µmol/L; 3 days) substantially down‐regulates the number of PGE1binding sites by ∼30%, without affecting their affinity. Radioligand binding studies performed in the presence of GTPγS (100 µmol/L) further revealed that the remaining PGE1binding sites are still capable of interacting functionally with their associated stimulatory G proteins, Gs. On the postreceptor level, neither changes in the abundance nor in the intrinsic activity of the α subunit of Gs(Gsα) were found during the state of opioid dependence, as has been verified by western blot and S49 cyc−reconstitution experiments, respectively. Evaluation of the functional interaction between PGE1receptors and Gsby means of receptor‐stimulated, cholera toxin‐catalyzed ADP‐ribosylation of Gsα revealed a significant increase in the ability of PGE1receptors to activate Gsα (3.3‐fold increase in EC50;p<0.05) in cells chronically exposed to morphine. This effect was completely blocked by coincubation of the cells together with the opiate antagonist naloxone (100 µmol/L; 3 days), whereas precipitation of morphine withdrawal by naloxone (100 µmol/L) had no further effect on sensitization in PGE1receptor/Gscoupling. These findings provide evidence that the stimulatory adenylate cyclase‐coupled PGE1receptor system represents a potential target of chronic δ‐opioid receptor activation in NG108‐15 hybrid cells. They further suggest that sensitization in stimulatory signal transduction plays a critical role i

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062449.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:Both iron and the major iron‐binding protein ferritin are enriched in oligodendrocytes compared with astrocytes and neurons, but their functional role remains to be determined. Progressive hypoxia dramatically induces the synthesis of ferritin in both neonatal rat oligodendrocytes and a human oligodendroglioma cell line. We now report that the release of iron from either transferrin or ferritin‐bound iron, after a decrease in intracellular pH, also leads to the induction of ferritin synthesis. The hypoxic induction of ferritin synthesis can be blocked either with iron chelators (deferoxamine or phenanthroline) or by preventing intracellular acidification (which is required for the release of transferrin‐bound iron) with weak base treatment (ammonium chloride and amantadine). Two sources of exogenous iron (hemin and ferric ammonium citrate) were able to stimulate ferritin synthesis in both oligodendrocytes and HOG in the absence of hypoxia. This was not additive to the hypoxic stimulation, suggesting a common mechanism. We also show that ferritin induction may require intracellular free radical formation because hypoxia‐mediated ferritin synthesis can be further enhanced by cotreatment with hydrogen peroxide. This in turn was blocked by the addition of exogenous catalase to the culture medium. Our data suggest that disruption of intracellular free iron homeostasis is an early event in hypoxic oligodendrocytes and that ferritin may serve as an iron sequestrator and antioxidant to protect cells from subsequent iron‐catalyzed lipid peroxidati

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062458.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract:In this study, we have investigated the ability of galectin‐3, a β‐galactoside‐binding animal lectin, to interact in vitro with different neural tissue‐derived glycoproteins involved in cell‐cell and cell‐substrate adhesion. Galectin‐3 interacted to varying degrees with the cell recognition molecules L1, the myelin‐associated glycoprotein, and the neural cell adhesion molecule and the extracellular matrix molecules tenascin‐C and tenascin‐R but not with collagen type I. Binding of galectin‐3 to the different glycoproteins tested was carbohydrate dependent and could be specifically inhibited by the addition of lactose and, to a le

ISSN:0022-3042    

DOI:10.1046/j.1471-4159.1995.64062465.x

出版商:Blackwell Science Ltd    

年代:1995

数据来源: WILEY