bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular calcium levels regulate the actions of nerve growth factor on calcium uptake in PC12 cells
Authors: Kozak A. , Nikodijevic B. , Yavin E. , Guroff G. 
Published: January 2005

AbstractThe uptake of divalent cations and the intracellular concentration of calcium in PC12 cells were studied by flow cytometric analysis using the calcium‐sensitive dye, Fluo‐3, under a variety of conditions. In particular the actions of nerve growth factor were analyzed. The data show that nerve growth factor stimulates the uptake of divalent cations and increases the intracellular calcium levels of cells attached to collagen‐coated plates. The data further indicate that nerve growth factor‐dependent increases in the uptake of divalent cations become less pronounced as the intracellular concentration of calcium increases. Intracellular calcium levels increase upon detachment of the cells from the plates and also with increasing cell density. Studies on the uptake of 45calcium confirmed the influence of intracellular calcium levels on nerve growth factor‐stimulated calcium uptake. Thus, the effect of nerve growth factor on the uptake of divalent cations is dependent on the calcium levels in the cells, perhaps explaining why previous studies in this field have provided inconsistent results. © 1992 Wiley‐Liss, Inc.
Mechanisms of nerve growth factor mRNA regulation by interleukin‐1β in hippocampal cultures: Role of second messengers
Authors: Friedman W. J. , Altiok N. , Fredholm B. B. , Persson H. 
Published: January 2005

AbstractCytokines such as interleukin‐1, which are found in the brain after trauma, regulate expression of nerve growth factor (NGF) mRNA and protein in hippocampal cultures. We have investigated possible mechanisms by which Il‐1β regulates NGF in hippocampal cells. The induction of NGF mRNA by Il‐1β was blocked by a receptor antagonist indicating that this effect is receptor mediated. Il‐1β elicited a dramatic induction of c‐fos mRNA and a slight elevation of c‐jun mRNA in a time dependent manner which may allow for a role in the induction of NGF mRNA expression. We examined whether specific second messenger pathways were involved in mediating the action of Il‐1β in the hippocampus. Activation of cAMP with forskolin or treatment with 8‐Br‐cAMP had no effect on NGF mRNA levels. Moreover, exposure of hippocampal cultures to Il‐1β evoked no change in cAMP levels, indicating that this second messenger system played little or no role in the regulation of NGF expression by Il‐1β in these cells. Further, interleukin‐1 elicited no change in membrane inositol phosphate turnover, nor did it affect intracellular calcium levels. Treatment of cell cultures with the phorbol ester PMA elicited an increase in NGF mRNA, suggesting that activation of protein kinase C (PKC) may mediate NGF mRNA expression. However, prolonged treatment of cultures with PMA to desensitize PKC did not eliminate the Il‐1β induction of NGF mRNA. Il‐1β, therfore, did not appear to activate NGF expression via cAMP, Ca2+, or a PKC isoform that is downregulated by prolonged PMA treatment. However, a phosphorylation event may be involved in the signal transduction mechanism, as treatment with okadaic acid to inhibit protein phosphatase 2a potentiated the induction of NGF mRNA by Il‐1β. The results presented indicate that Il‐1β acts via its receptor in induce a rise in NGF expression. Identification of the specific second messenger pathway has remained elusive; however, a phosphorylation event appears to be intermediary. Moreover, the induction of c‐fos and c‐jun may represent a final common path in activation of NGF gene expression by different signals such as Il‐1β and PMA. © 1992 Wiley‐Liss, Inc.
Cell cycle and proliferation dynamics of adult rat oligodendrocytes
Authors: Vick R. S. , Collins J. M. , Devries G. H. 
Published: January 2005

AbstractAdult oligodendrocytes (OLGs) have been shown to be mitotically responsive when co‐cultured with dorsal root ganglion. We have investigated the population dynamics of the OLG proliferative response, including the maximum percent of cells which will proliferate and the cell cycle duration time of the adult rat OLG. Adult OLGs were stimulated with pituitary extract and either continuously labeled or pulse labeled with bromodeoxyuridine (BrdU). The labeled cells were stained with a fluorescent anti‐BrdU monoclonal antibody, and fluorescence measurements were made with a multiparameter flow cytometer. A maximum number of 53% of the adult OLGs entered the cell division cycle after 9 days. The cell division cycle duration time (Tc) was determined to be approximately 35.4 hr, and the durations of G1, S, and G2M found to be 12.1, 8.5, and 5.8 hr, respectively. A scenario was generated for adult OLG proliferation in which 2.2% of the initial population is stimulated to enter the cell division cycle in the first 24 hr. This initial population divides and continues in the cell division cycle. Another 2.2% of the initial population enters the cell division cycle during the second 24 hr period, divides, and continues in the cell division cycle. This entry of 2.2% of the cells into the proliferative phase continues until 53% of the initial population has left a quiescent state and entered the cell cycle. © 1992 Wiley‐Liss, Inc.
DM20 mRNA splice product of the myelin proteolipid protein gene is expressed in the murine heart
Authors: Campagnoni C. W. , Garbay B. , Micevych P. , Pribyl T. , Kampf K. , Handley V. W. , Campagnoni A. T. 
Published: January 2005

AbstractNorthern blot analysis of poly A(+) RNA isolated from mouse heart revealed the expression of 3.3 and 2.4 kb mRNAs that hybridized with a cDNA for the mouse proteolipid protein (PLP). In order to examine the relationship of these RNAs to the myelin PLP/DM20 mRNAs, a mouse heart cDNA library was prepared and screened with a mouse PLP cDNA. A cDNA was isolated, sequenced, and found to encode the DM20 variant of PLP. Polymerase chain reaction (PCR) analysis of heart cDNA with three sets of primers confirmed the presence of DM20 mRNA in mouse heart and indicated that it is the major splice product of the PLP gene expressed in that tissue. In situ hybridization localized the expression of the DM20 mRNA to the myocardial cells. Northern blot analysis indicated that expression of the DM20 mRNA is developmentally regulated in the murine heart, increasing significantly in concentration after 12 days postpartum. Northern analysis also revealed the expression of the DM20 mRNA in the hearts of the jimpy and quaking mutants. These results indicate that the PLP gene is expressed in tissues other than brain and support the concept that products of the PLP gene may have some biological role other than as structural components of myelin. © 1992 Wiley‐Liss, Inc.
Incorporation of 15N from L‐leucine into isoleucine by rat brain cerebral cortex slices
Authors: Gheorvassaki E. , Papadakis D. , Alikaridis F. , Kephalas T. , Larsen C. , Palaiologos G. 
Published: January 2005

AbstractThe fate of leucine nitrogen in the central nervous system was investigated by incubating rat cerebral cortex slices in the presence of 0.5 mM each of L‐[15N]‐leucine, L‐isoleucine, and L‐valine. Analysis of the slices and incubation media for free amino acids by gas chromatography‐mass spectrometry revealed that the 15N from leucine is incorporated into isoleucine only. No 15N was detected in valine or any other amino acid. These results suggest that leucine, valine, and their corresponding aminotransferases may be compartmentalized in brain cerebral cortex. © Wiley‐Liss, Inc.
Oligodendrocyte differentiation and progenitor cell proliferation are independently regulated by cyclic AMP
Authors: Raible D. W. , McMorris F. Arthur 
Published: January 2005

AbstractOligodendrocytes, the glial cells specialized to synthesize myelin in the central nervous system, differentiate in primary rat brain cell cultures on a schedule similar to that observed in vivo. The schedule of oligodendrocyte differentiation and the rate of oligodendroglial progenitor cell proliferation in vitro are both modulated by 3′,5′‐cyclic AMP (cAMP). A 24‐hour exposure to 1 mM N6,2′O‐dibutyryladenosine 3′,5′‐cyclic monophosphate (dbcAMP) induced a wave of oligodendrocyte differentiation but inhibited proliferation of oligodendroglial progenitors, and reduced by 30‐fold the proliferation of progenitors in response to platelet‐derived growth factor (PDGF). When cells were grown in the presence of maximally stimulating concentrations of PDGF, the inhibitory effect of cAMP on progenitor cell proliferation was abolished while the stimulatory effect of cAMP on oligodendrocyte differentiation remained, demonstrating that these two cAMP‐regulated events are independent. © 1993 Wiley‐Liss, Inc.
Cytotoxic actions and effects on intracellular Ca2+ and cGMP concentrations of sulphur‐containing excitatory amino acids in cultured cerebral cortical neurons
Authors: Frandsen A. , Schousboe A. , Griffiths R. 
Published: January 2005

AbstractEffects of the sulphur‐containing acidic amino acids (SAAs) cysteic acid (CA), homocysteic acid (HCA), cysteine sulphinic acid (CSA), homocysteine sulphinic acid (HCSA), and S‐sulphocysteine (SC) on intracellular concentrations of Ca2+ ([Ca2+]i) and cGMP ([cGMP]i) as well as their cytotoxic actions were investigated in cultured cerebral cortical neurons. The glutamate receptor subtype selective antagonists APV (D‐(−)‐2‐amino‐5‐phosphonopentanoate) acting on N‐methyl‐D‐aspartate (NMDA) receptors and DNQX (6,7‐dinitroquinoxaline‐2,3‐dione) acting on non‐NMDA receptors were employed to obtain information about the involvement of glutamate receptor subtypes in these actions of the SAAs. It was found that all SAAs exerted a cytotoxic action on the neurons. The ED50 values for CSA, CA, HCSA, and HCA were around 30 to 50 μM and that for SC was about 150 μM. The glutamate transport blocker L‐aspartate‐β‐hydroxamate increased the efficacy of CSA and CA but had no effect on the cytotoxic actions of the remaining SAAs. In case of CA, HCA, and SC the cytotoxicity could be prevented by APV alone and for HCSA, DNQX could block the toxic action. DNQX reduced the toxicity of HCA somewhat but the presence of APV was required for complete protection. CSA toxicity could only be blocked by the combination of APV and DNQX. All SAAs induced an increase in [cGMP]i and [Ca2+]i and with regard to [Ca2+]i SC was the most potent and CA the least potent SAA. The effect of all SAAs on [cGMP]i could be blocked by APV alone whereas DNQX had no effect except in the case of HCSA where the response was blocked completely and HCA where the response was inhibited by 75%. The SAA‐induced increase in [Ca2+]i could in all cases be significantly reduced by 0.6 mM Mg2+ and in the presence of Mg2+, APV dose dependently blocked the remaining SAA induced increase in [Ca2+]i completely. Under these conditions DNQX was also found to block the SAA‐induced increase in [Ca2+]i dose dependently. In the absence of Mg2+, DNQX (25 μM) inhibited the response of the SAAs only by 65–75%. Under these conditions all SAA responses except that to SC could be fully antagonized by 300 μM APV. The SC‐induced increase in [Ca2+]i was inhibited by 60% by APV. The results show that no simple correlation exists between SAA‐induced cytotoxicity and their ability to increase intracellular levels of Ca2+ and cGMP. However, when both NMDA and non‐NMDA receptors were antagonized no toxicity or changes in calcium or cGMP were observed. © 1993 Wiley‐Liss, Inc.
Selective modulation of cholinergic properties in cultures of avian embryonic sympathetic ganglia
Authors: Smith J. , Vyas S. , Garcia‐Arraras J. E. 
Published: January 2005

AbstractWe have studied the expression of catecholaminergic and cholinergic phenotypes in sympathetic ganglia removed from 7‐ to 10‐day‐old quail embryos and grown in vitro under different conditions. Quantitative data were obtained by measuring the conversion of (3H) tyrosine and (3H) choline to catecholamines (CA) and acetylcholine (ACh), respectively. In explant cultures, large amounts of both neurotransmitters were synthesized from the onset, but CA generally predominated, the molar ratios of CA:ACh being, on average, of the order of 2:1. If the ganglia were dissociated before plating, there was a selective increase in ACh synthesis (three‐ to fivefold) such that the CA:ACh ratio fell strikingly. The early expression of the cholinergic phenotype appears to be species‐specific in that, under identical conditions, dissociated cell cultures of newborn mouse superior cervical ganglia were overwhelmingly catecholaminergic (CA:ACh ratio of approximately 40:1) and ACh synthesis was only just detectable. Addition of veratridine (1.5 μM) either to explant or to dissociated cell cultures of embryonic quail sympathetic ganglia barely altered CA‐synthesizing ability; in contrast, ACh synthesis and accumulation were stimulated about threefold. This effect, which we found to correspond to a quantitatively similar increase in the activity of choline acetyltransferase (ChAT), was completely blocked by tetrodotoxin, indicating that it was due to Na+‐dependent depolarization. A preferential stimulation of ACh production was also observed when the concentration of K+ was raised to 20 mM. Veratridine treatment of cultures of presumptive sympathoblasts, in the form of sclerotome‐associated neural crest cells, had identical effects. Our results reveal the quantitative importance of ACh‐related properties in avian sympathetic ganglia from the earliest stages of their development and suggest that depolarization may be one of the factors selectively enhancing expression of the cholinergic phenotype during ontogeny. In these respects, the neurochemical differentiation of sympathetic neurons unfolds according to dissimilar scenarios in birds and mammals. © 1993 Wiley‐Liss, Inc.
Detection of 5‐hydroxytryptamine2 receptors by radioligand binding, northern blot analysis, and Ca2+ responses in rat primary astrocyte cultures
Authors: Deecher D. C. , Wilcox B. D. , Dave V. , Rossman P. A. , Kimelberg H. K. 
Published: January 2005

AbstractRadioligand binding, Northern blot analysis, and changes in [Ca2+]i were used to study serotonin [5‐hydroxytryptamine (5HT)] receptor subtypes in primary cultures of astrocytes from neonatal rat cerebral cortex. Radioligand binding studies revealed the presence of 5HT2, but not the 5HT1 or 5HT3 receptor subtypes. Radioligand binding was also used to show the presence of serotonin uptake sites, which had previously been shown to be present by [3H]‐5HT uptake, and also α1‐adrenergic receptors as has previously been reported by binding studies. Northern blot analysis of cortical astrocyte mRNA demonstrated the presence of transcripts for 5HT2 receptors, but failed to identify mRNA for 5HT1α or 5HT1c receptors. Thus, results from Northern blot analysis correlated with the radioligand binding data which showed only 5HT2 receptors. Equilibrium saturation studies, using 125[I]‐LSD to label 5HT2 receptors, yielded a KD of 9 nM and a Bmax of 177 fmol/mg protein. Radioligand binding studies or primary astrocyte cultures prepared from other brain regions also showed the presence of α1‐ adrenergic, 5HT2 receptor, and 5HT‐uptake sites, but no detectable 5HT1a receptors, which were the only 5HT1 receptors studied. Studies demonstrating 5HT‐induced, spiperone‐ and ketanserin‐sensitive increases in free [Ca2+]i as measured by FURA‐2, showed that the 5HT2 receptors were functional in these cells. These data provide clear evidence for the existence of both 5HT2 receptors and 5HT‐uptake sites in the same primary astrocyte cultures from neonatal rat cerebral cortex, with no detectable evidence of 5HT1a or 5HT1c subtypes. © 1993 Wiley‐Liss, Inc.
Expression of heterologous proteins in cultured rat hippocampal neurons using the semliki forest virus vector
Authors: Olkkonen V. M. , Liljeström P. , Garoff H. , Simons K. , Dotti C. G. 
Published: January 2005

AbstractThe Semliki Forest virus expression vector (Liljeström and Garoff: Bio/Technology 9:1356‐1361, 1991) was tested in cultured rat hippocampal neurons using two Madin‐Darby canine kidney (MDCK) cell membrane‐associated proteins as reporters: rab8, a small GTP ase involved in post‐Golgi vesicle transport, and VIP21, an integral membrane protein of caveolae, trans‐Golgi network, and post‐Golgi vesicles. Expression of the c‐myc epitope‐tagged proteins was visualized by immunofluorescence microscopy. The proteins were first detected in neurons after 3–4 hr infection by the recombinant viruses. The infection efficiency on neurons was high: after 6 hr infection at a multiplicity of one, 50–60% of the cells expressed the reporter proteins. The neurons tolerated the in fection well up to 8 hr. Their polarized organization was not disturbed, as judged from morphology and from distribution of the dendritic MAP2 and axonal synaptophysin marker proteins. The Semliki Forest virus vector thus seems suitable for short‐term expression of proteins in cultured neurons. © 1993 Wiley‐Liss, Inc.
Striatal degeneration induced by mitochondrial blockade is prevented by biologically delivered NGF
Authors: Frim D. M. , Simpson J. , Uhler T. A. , Short M. P. , Bossi S. R. , Breakefield X. O. , Isacson O. 
Published: January 2005

AbstractConsistent with the notion that a defect in cellular energy metabolism is a cause of human neurodegenerative disease, systemic treatment with the mitochondrial complex II inhibitor 3‐nitropropionic acid (3‐NPA) can model the striatal neurodegeneration seen in Huntington's disease. Previously, we have found that nerve growth factor (NGF), delivered biologically by the implantation of a genetically altered fibroblast cell‐line, can protect locally against striatal degeneration induced by infusions of high doses of glutamate receptor agonists. We now report that implantation of NGF‐secreting fibroblasts reduces the size of adjacent striatal 3‐NPA lesions by an average of 64%. We conclude that biologically delivered NGF protects neurons against excitotoxicity and mitochondrial blockade—both energy‐depleting processes—implying that appropriate neurotrophic support in the adult brain could protect against neurodegenerative diseases caused in part by energy depletion. © 1993 Wiley‐Liss, Inc.
Specific regulation of immediate early genes by patterned neuronal activity
Authors: Sheng H. Z. , Fields R. D. , Nelson P. G. 
Published: January 2005

AbstractElectrical activity shapes development of the nervous system, presumably in part by regulating gene expression. A set of regulatory genes, immediate early genes (IEGs), which are responsive to a number of extrinsic cellular stimuli have been proposed to play a role in coupling such activity to gene expression. Using a semiquantitative polymerase chain reaction assay, we show that in dissociated mouse dorsal root ganglion neurons the expression of two IEGs, c‐fos and nur/77, is differentially sensitive to patterns of electrical stimulation. Differences in c‐fos activation did not correlate with the peak intracellular calcium [Ca++]i produced by the different stimulation patterns or with residual [Ca++]i following stimulation. However, the net increase in [Ca++]i (calcium time integral) was greater for the pulsed stimulus that activated c‐fos (6 impulses/min), compared to the ineffective stimulus (12 impulses/2 min). This system of genes seems suited to mediating the coupling between electrical activity and other functional genes. © 1993 Wiley‐Liss, Inc.
Optimized survival of hippocampal neurons in B27‐supplemented neurobasal™, a new serum‐free medium combination
Authors: Brewer G. J. , Torricelli J. R. , Evege E. K. , Price P. J. 
Published: January 2005

AbstractWe have systematically optimized the concentrations of 20 components of a previously published serumfree medium (Brewer and Cotman, Brain Res 494: 65‐74, 1989) for survival of rat embryonic hippocampal neurons after 4 days in culture. This serum‐freemedium Supplement, B27, produced neuron survival above 60% independent of plating density above 160 plated cells/mm2 For isolated cells (<100 cells/mm2), survival at 4 days was still above 45%, but could be rescued to the 60% level at 40 cells/mm2 by simply applying a coverslip on top of the cells. This suggests a need for additional trophic factors. High survival was achieved with osmolarity lower than found in Dulbecco's Modified Eagle's Medium (DMEM), and by reducing cysteine and glutamine concentrations and by the elimination of toxic ferrnous sulphate found in DME/F12. Neurobasal is a new medium that incorporates these modifications to DMEM. In B27/ Neurobasal, glial growth is reduced to less than 0.5% of the nearly pure neuronal population, as judged by immunocytochemistry for glial fibrillary acidic protein and neuron‐specific enolase. Excellent long‐term viability is achieved after 4 weeks in culture with greater than 90%viability for cells plated at 640/mm2 and greater than 50 viability for cells plated at 160/mm2 Since the medium also supports the growth of neurons from embryonic rat striatum, substantia nigra, septum, and cortex, and neonatal dentate gyrus and cerebellum (Brewer, in preparation), support for other neuron types is likely. B27/Neurobasal should be useful for in vitro studies of neuronal toxicology, pharmacology, electrophysiology, gene expression, development, and effects of growth factors and hormones. © 1993 Wiley‐Liss, Inc.
B‐50 (GAP‐43) in the spinal cord caudal to hemisection: Indication for lack of intraspinal sprouting in dorsal root axons
Authors: Nacimiento W. , Mautes A. , Töpper R. , Oestreicher A. B. , Gispen W. H. , Nacimiento A. C. , Noth J. , Kreutzberg G. W. 
Published: January 2005

AbstractSprouting of dorsal root axons has been suggested to occur in the mature cat spinal cord caudal to a hemisection at a low thoracic level sparing the dorsal columns. The lesion interrupts supraspinal descending projections, while leaving ascending collaterals of dorsal root axons intact. This hypothesis was re‐evaluated by comparing the light and electron microscopic immunoreactivity of B‐50 (GAP‐43) on both sides of the postulated target regions for sprouting, the intermediate gray and the dorsal horn. The neural‐specific phosphoprotein B‐50 is involved in regenerative and developmental axonal outgrowth and synaptic plasticity. The light microscopic distribution pattern and density of B‐50 immunostaining, measured by quantitative densitometry, were bilaterally symmetrical in all segments below the hemisection 3.5, 8, 14, 21, and 56 days postoperatively, as they were in the intact animal. Ultrastructurally, growth cone‐like profiles were not detectable during putative periods of sprouting in regions of interest. After removal of degenerated axon terminals, vacated postsynaptic places appeared to be covered by astrocytic processes. These results indicate that, under the present experimental conditions, sprouting of primary afferents in adult cats is unlikely to be involved in functional plasticity after removal of descending pathways. © 1993 Wiley‐Liss, Inc.