bluuebunny/crossref_metadata_2025_split huggingface dataset:
Posttranslational modification of glycine‐extended substance P by an α‐amidating enzyme in cultured sensory neurons of dorsal root ganglia
Authors: Wong M. , Jeng A. Y. 
Published: January 2005

AbstractThe terminal step in the biosynthesis of substance P is the conversion of its glycine‐extended precursor to the mature, amidated peptide by the α‐amidating enzyme. This posttranslational modification was demonstrated in cultured dissociated sensory neurons of dorsal root ganglia from neonatal rats. An assay was developed to quantitate both substance P and its precursor peptide in these cells. More than 90% of these two peptide was present as mature peptide in uncultured cells. In contrast, after 8 days in culture, about 85% of the peptides was the precursor, which increased 200‐fold, whereas the level of substance P itself tripled during this culturing period. Since α‐amidating enzyme requires ascorbate for activity, this reducing agent was added to the culture medium. Ascorbate induced a dose‐dependent rise in the percentage of amidated peptide, with an apparent Km of 20μM. After 5 days of culturing in the presence of 500 μ ascorbate, substance P increased 8‐fold, constituting 70% of the total. The α‐amidating enzyme also needs copper for activity. Even with 500 μM ascorbate in the culture medium, the copper chelator diethyldithiocarbamate dose‐dependently reduced substance P synthesis by the sensory neurons, with a concomitant increase in its precursor peptide. These results suggest the presence of α‐amidating enzyme in sensory neurons of dorsal root ganglia. It is likely that conversion of other glycine‐extended precursors to their mature peptides in cell cultures would also require ascorbate and copper. © 1994 Wiley‐Liss, Inc.
Glucocorticoid‐induced upregulation of proteolipid protein and myelin‐associated glycoprotein genes in C6 cells
Authors: Zhu W. , Wiggins R. C. , Konat G. W. 
Published: January 2005

AbstractThe effect of dexamethasone on the expression of proteolipid protein (PLP) and myelin‐associated glycoprotein (MAG) genes was investigated in rat C6 glioma cells. The steady state level of the respective mRNA was quantitated by Northern blot analysis. The treatment of cells with dexamethasone transiently upregulated the expression of both genes with peak mRNA levels of approximately 10‐fold over control levels occurring at day 3 for the PLP gene and at day 5 for the MAG gene. The effect was directly related to the drug concentration in the range from 10−9 to 10−5M. Combined exposure of the cells to dexamethasone and retinoic acid featured an additive effect on PLP gene expression, whereas MAG gene expression was depressed below detectability level. The dissimilarity in the response of the genes to dexamethasone and retinoic acid supports the contention that the genes are controlled by different mechanisms. Furthermore, the results indicate that the effects of dexamethasone and retinoic acid on the myelin genes are mediated by different regulatory pathways. © 1994 Wiley‐Liss, Inc.
Characteristics of HIV‐1 gp120 glycoprotein binding to glycolipids
Authors: McAlarney T. , Apostolski S. , Lederman S. , Latov N. 
Published: January 2005

AbstractWe examined the binding of the gp120 envelope glycoprotein (gp120) of the human immunodeficiency virus (HIV‐1) to sulfatide (GalS), galactocerebroside (GalC), and GMI‐ganglioside (GMI). The gp120 glycoprotein bound to GalS but not to GalC or GMI by enzyme‐linked immunosorbent assay (ELISA) and by an immunospot assay on nitrocellulose paper. However, it bound to all three glycolipids by an immunospot assay on thin layer chromotography (TLC) plates. In studies to determine whether GalS could be a receptor for gp120 on the surface of cells, gp120 bound to GalS incorporated into the plasma membrane of lymphoid cells as determined by cytofluorometric analysis and immunofluorescence microscopy. These studies indicate that GalS may function as a receptor for gp120 and HIV‐1. © 1994 Wiley‐Liss, Inc.
Delayed application of aurintricarboxylic acid reduces glutamate‐induced cortical neuronal injury
Authors: Csernansky C. A. , Canzoniero L. M. T. , Sensi S. L. , Yu S. P. , Choi D. W. 
Published: January 2005

AbstractThe non‐specific endonuclease inhibitor, aurintricarboxylic acid (ATA), attenuated glutamate‐induced destruction of cultured cortical neurons. In part, this protective effect likely reflected the ability of ATA to produce a slowly developing block of N‐methyl‐D‐aspartate receptor‐mediated inward whole cell current or increase in intracellular free Ca2+. However, ATA also attenuated a high K+‐induced increase in intracellular free Ca2+ in the presence of D‐aminophosphonovalerate, suggesting that ATA may have a more general effect on Ca2+ homeostasis. In addition, ATA attenuated glutamate neurotoxicity even if added up to 2 hr after completion of glutamate exposure, a time when glutamate antagonists or lipid peroxidation inhibitors are no longer neuroprotective. Involvement of apoptosis in this excitotoxic death is unlikely, as Southern blotting of genomic DNA revealed no evidence of fragmentation, and death was not prevented by inhibitors of RNA or protein synthesis. Most likely, ATA interferes with some key downstream consequences of excitotoxic glutamate receptor overactivation. © 1994 Wiley‐Liss, Inc.
Neural regulation of muscle acetylcholinesterase is exerted on the level of its mRNA
Authors: Črešnar B. , Črne‐Finderle N. , Breskvar K. , Sketelj J. 
Published: January 2005

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, Inc.
Astrocyte‐derived lipoxygenase product evokes endothelium‐dependent relaxation of the basilar artery
Authors: Murphy S. , Rich G. , Orgren K. I. , Moore S. A. , Faraci F. M. 
Published: January 2005

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 Wiley‐Liss, Inc.
Subcellular localization of the F5 protein to the neuronal membrane‐associated cytoskeleton
Authors: Arai M. , Cohen J. A. 
Published: January 2005

AbstractF5 was identified originally as an interleukin‐2‐regulated gene in the murine helper T‐lymphocyte clone L2. Subsequent studies demonstrated high levels of F5 mRNA and protein in mature neurons in adult mouse central and peripheral nervous systems. The F5 protein was present in dendrites and perikarya but not in axons. In the present studies, the intracellular localization of the F5 protein in adult mouse brain was determined by subcellular fractionation and Western blotting. Although the deduced F5 sequence predicts a soluble protein, virtually no F5 immunoreactivity was found in the cytosol. The F5 protein was restricted to the P2 crude mitochondrial and P3 crude microsomal particulate fractions. Within the P2 fraction, F5 protein was enriched in the P2B synaptosomal subfraction. The results of temperature‐dependent phase separation with Triton X‐114 and alkaline extraction with sodium carbonate of the P2 and P3 fractions were consistent with the F5 protein being an extrinsic membrane‐associated protein. Although essentially all of the F5 protein in the P3 fraction was membrane‐associated, a substantial proportion of P2‐associated F5 protein and nearly all of the synaptosomal F5 protein was detergent‐insoluble. Direct isolation and subfractionation of brain cytoskeleton confirmed colocalization of F5 immunoreactivity with the membrane‐associated cytoskeleton and postsynaptic densities. These studies suggest that the F5 protein, which has a large number of potential phosphorylation sites, plays a role in membrane‐cytoskeletal interactions and in dynamic aspects of synaptic structure or function. © 1994 Wiley‐Liss, Inc.
Coexpression of alpha and gamma enolase genes in neurons of adult rat brain
Authors: Keller A. , Bérod A. , Dussaillant M. , Lamandé N. , Gros F. , Lucas M. 
Published: January 2005

AbstractEnolase (EC 4.2.1.11) is a glycolytic enzyme active as a dimer. In adult brain extracts, three forms, αα, αγ and γγ, have been described, with the αγ hybrid accounting for 30% of total enolase activity (Fletcher et al., Dev Biol 65:462–475, 1978; Lucas et al., Dev Neurosci 10:91–98, 1988). Previous biochemical studies strongly suggest that this hybrid is not generated artefactually during the extraction procedures (Keller et al., J Neurochem 36:1389–1397, 1981; Shimizu et al., BBA 748:278–284, 1983). Immunocytological observations have demonstrated the cell specific localization of the α subunit in astrocytes and of the γ subunit in neurons at the adult stage, but failed to identify a cell type containing both the α and γ subunits necessary for the formation of the αγ hybrid isoform (Ghandour et al., Exp Brain Res 41:271–279, 1981; Vinores et al., J Histochem Cytochem 32:1295–1302, 1984; Iwanaga et al., Arch Histol Cytol [Suppl] 52:13–24, 1989). We sought to approach this question by performing in situ hybridization studies in order to visualize the α and γ mRNAs. In agreement with the immunocytological reports, we observe a specific accumulation of the γ enolase transcripts in neurons and a high accumulation of α enolase transcripts in some glial cells such as the ependymocytes lining the ventricles.Our observations, following hybridization with 35S labeled oligonucleotide specific probes on adjacent thin sections, demonstrate for the first time that transcription of both α and γ enolase genes occurs in many neurons of different brain regions. These results render highly probable the formation of the αγ hybrid in mature neurons.Furthermore, we observe a differential expression of the genes encoding the α and γ enolase subunits in various neuronal populations of the brain. The implications of these observations are discussed. © 1994 Wiley‐Liss, Inc.
Fibroblast growth factor‐induced increases in calcium currents in the PC12 pheochromocytoma cell line are tyrosine phosphorylation dependent
Authors: Rane S. G. , Pollock J. D. 
Published: January 2005

AbstractThe PC12 rat pheochromocytoma cell line is widely used to study neuronal differentiation by growth factors. In response to nerve growth factor (NGF) and basic fibroblast growth factor (bFGF), PC12 cells differentiate into sympathetic‐like neurons and become electrically excitable. Using whole cell patch‐clamp recording, with barium as a charge carrier, we looked at the effects of bFGF on calcium channel expression as reflected by changes in barium current amplitudes normalized to cell membrane area. Similar to the effect reported for NGF, we show that 7 day treatment with bFGF increased the barium current approximately 4‐fold. The largest contributor to the increase in barium current with bFGF treatment is a 6‐fold increase in the high threshold voltage activated Ω‐conotoxin sensitive barium current. Smaller increases in current produced by bFGF treatment of PC12 cells are observed for the dihydropyridine sensitive and dihydropyridine/conotoxin insensitive currents. The bFGF‐induced increases in barium currents are dependent on tyrosine phosphorylation, since the effects of bFGF are blocked by genistein, a tyrosine kinase inhibitor. This system will ultimately be useful in understanding the signaling pathways that control calcium channel expression in response to growth factors. © 1994 Wiley‐Liss, Inc.
Expression of the intermediate filament‐associated protein related to β‐amyloid precursor protein is developmentally regulated in cultured cells
Authors: Durham H. D. , Minotti S. , Dooley N. P. , Nalbantoglu J. 
Published: January 2005

AbstractIt was previously reported that a monoclonal antibody to β‐amyloid precursor protein (mab22C11; Boehringer Mannheim, Indianapolis, IN) labels an intermediate filament‐associated protein (βAPP‐IFAP) in cultured human skin fibroblasts (Dooley et al.: J Neurosci Res 33:60–67, 1992). The time course of its expression and association with different classes of intermediate filaments has been assessed in neurons, Schwann cells, and astrocytes in dissociated cultures of murine brain and spinal cord‐dorsal root ganglia; in primary cultures of human muscle; and in the epithelial cell line PtK1. βAPP‐IFAP was expressed in all non‐neuronal cell types examined. Mab22C11 immunoreactivity was minimal or absent following dissociation or subculture, but gradually increased with time. In fibroblasts, myoblasts, and epithelial cells, the distribution eventually resembled that of vimentin. With the exception of glial fibrillary acidic protein (GFAP), βAPP‐IFAP was not associated with the intermediate filament proteins characteristically found in differentiated cells, i.e., desmin, the cytokeratins, and neurofilament proteins. No labeling of neurons by mab22C11 was observed at any stage of in vitro maturation. In sections of Alzheimer's brain, the antibody labeled a subpopulation of reactive astrocytes. It is suggested that βAPP‐IFAP may be the product of a member of the βAPP multigene family expressed developmentally in non‐neuronal cells. © 1994 Wiley‐Liss, Inc.
Human fetal neurons in culture: Intercellular communication and voltage‐ and ligand‐gated responses
Authors: Chiu F.‐C. , Rozental R. , Bassallo C. , Lyman W. D. , Spray D. C. 
Published: January 2005

AbstractWe established high density primary cultures of neural cells from dissociated second trimester human fetal brains using a novel spin seeding method. Under our culture conditions, the majority of the cells exhibited neuronal phenotypes as evidenced by morphological criteria, immunoreactivity to the 66 kDa neurofilament protein and expression of TTX‐sensitive Na+ channels and cell excitability. These cultures were enriched in glutamic acid decarboxylase (GAD), the synthetic enzyme of the neurotransmitter GABA, and responded with Ca2+ influx to acute application of glutamate. Interestingly, the human fetal neurons in culture did not express either dopaminergic or cholinergic phenotypes. In addition, the population of neurons obtained express a high incidence of gap junction‐mediated intercellular communication. These studies provide evidence that functional neuronal properties arise early during prenatal development in humans and offer the potential to evaluate pharmacological agents on primary human neurons. © 1994 Wiley‐Liss, Inc.
Inhibitors of N‐linked oligosaccharide processing glucosidases interfere with oligodendrocyte differentiation in culture
Authors: Bhat N. R. , Zhang P. 
Published: January 2005

AbstractPrevious studies have demonstrated that inhibitors of glycoprotein processing glucosidases interfere with the development of oligodendrocyte properties in primary cultures of embryonic rat brain cells (Bhat, J Neurosci Res 20:158–164, 1988). The present study examines the effect of castanospermine, an inhibitor of the processing glucosidases, on the development and differentiation of isolated oligodendrocyte progenitor cells. Treatment of oligodendrocyte progenitors with castanospermine did not affect the developmental progression of the precursors to become committed oligodendrocytes as revealed by comparable increases in the percentages of cells positive for galactocerebroside (a surface marker for terminally differentiated oligodendrocytes) in control and drugtreated cultures. On the other hand, there was an impairment of the expression of differentiated properties of oligodendrocytes [i.e., sulfolipid synthesis, myelin basic protein (MBP)] and 2′3′‐cyclic nucleotide 3′‐phosphohydrolase in the drug‐treated cultures. Immunocytochemical analysis with anti‐MBP antibodies revealed a reduced number of MBP‐positive cells in inhibitor‐treated cultures. Furthermore, a majority of MBP‐positive cells in such cultures displayed immunoreactive MBP in their cell body and not the processes, unlike in control cultures where both cell body and the processes of oligodendrocytes stained intensely for MBP. The strong inhibitory effect of castanospermine on the expression of oligodendrocyte‐specific activities was contrasted with a relatively smaller effect of swainsonine, a mannosidase inhibitor on oligodendrocyte differentiation. Both castanospermine and swainsonine, however, effectively blocked the formation of complex‐type oligosaccharides, suggesting thereby a lack of correlation between the inhibition of the formation of complex‐type oligosaccharides and oligodendrocyte differentiation. It is suggested, therefore, that early trimming reactions involving the removal of glucose residues from the high mannose oligosaccharides in the endoplasmic reticulum may be essential for the cell surface localization and function of glycoproteins critically involved in surface interactions of oligodendrocytes with each other and/or with the substratum. Copyright © 1994 Wiley‐Liss, Inc.
Dopamine transporter mediated release of dopamine: Role of chloride
Authors: Sitges M. , Reyes A. , Chiu L. M. 
Published: January 2005

AbstractUsing a rapid (0.5 ml/min) flow rate superfusion system, the dopamine (DA) transporter mediated release of DA is further explored, and compared to the depolarization evoked release of DA in rat striatal synaptosomes preloaded with radioactive DA (3H‐DA). In this system external DA in the low μM range efficaciously releases the preloaded transmitter, the maximal response being reached at 3 μM DA. The external DA stimulated release is Ca2+‐independent, Cl−‐dependent, and blocked by both bupropion and nomifensine. The atypical antidepressant bupropion inhibits 3H‐DA accumulation to rat striatal synaptosomes with a calculated IC50 of 1.3 × 10−6M. Among DA uptake blockers some are known to act as DA releasing agents. Here we found that the DA uptake blocker nomifensine (30 μM) is unable to modify the baseline release of 3H‐DA, whereas bupropion (10 μM) clearly elevates the baseline release of 3H‐DA in a Ca2+‐independent and Cl−‐dependent manner. The non releasing agent nomifensine blocks the release of 3H‐DA induced by bupropion. The Ca2+‐dependent, high K+ depolarization evoked release of 3H‐DA is not modified by nomifensine and does not depend on the external Cl− concentration. When the depolarizing medium contains DA the carrier mediated release of 3H‐DA induced by the external DA is additive to the high K+ induced response. A drastic drop in the external Cl− concentration induces 3H‐DA release. This release of 3H‐DA induced by low external Cl− levels is completely blocked by nomifensine, which only slightly diminished the release of 3H‐DA induced by the absence of external Na+. On the basis of these results, it is concluded that: (1) Rapid perfusion flow rates eliminate DA reuptake. (2) DA uptake inhibitors either with or without DA releasing capabilities block the release of DA induced by μM levels of external DA. (3) By preventing translocation of the DA transporter mobile moiety, nomifensine may inhibit the release of DA induced by external DA or bupropion and by drastic drops in the external Cl−w concentration. (4) In the absence of nomifensine, the DA transporter works under both resting and depolarized conditions, but in contrast to the GABA transporter (Sitges et al.: Neurochem Res 18:1081–1087, 1993), the DA transporter does not contribute to the amount of the DA released by depolarization. (5) Reversal of the DA uptake carrier is favored by conditions increasing the internal DA levels. (6) Cl− rather than Na+ is a major determinant in 3H‐DA movements through the DA transporter. Copyright © 1994 Wiley‐Liss, Inc.