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  • 1
    Electronic Resource
    Electronic Resource
    Characterization of P2X3, P2Y1 and P2Y4 receptors in cultured HEK293-hP2X3 cells and their inhibition by ethanol and trichloroethanol (2003)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 85 (2003), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Membrane currents and changes in the intracellular Ca2+ concentration ([Ca2+]i) were measured in HEK293 cells transfected with the human P2X3 receptor (HEK293-hP2X3). RT-PCR and immunocytochemistry indicated the additional presence of endogenous P2Y1 and to some extent P2Y4 receptors. P2 receptor agonists induced inward currents in HEK293-hP2X3 cells with the rank order of potency α,β-meATP ≈ ATP 〉 ADP-β-S 〉 UTP. A comparable rise in [Ca2+]i was observed after the slow superfusion of ATP, ADP-β-S and UTP; α,β-meATP was ineffective. These data, in conjunction with results obtained by using the P2 receptor antagonists TNP-ATP, PPADS and MRS2179 indicate that the current response to α,β-meATP is due to P2X3 receptor activation, while the ATP-induced rise in [Ca2+]i is evoked by P2Y1 and P2Y4 receptor activation. TCE depressed the α,β-meATP current in a manner compatible with a non-competitive antagonism. The ATP-induced increase of [Ca2+]i was much less sensitive to the inhibitory effect of TCE than the current response to α,β-meATP. The present study indicates that in HEK293-hP2X3 cells, TCE, but not ethanol, potently inhibits ligand-gated P2X3 receptors and, in addition, moderately interferes with G protein-coupled P2Y1 and P2Y4 receptors. Such an effect may be relevant for the interruption of pain transmission in dorsal root ganglion neurons following ingestion of chloral hydrate or trichloroethylene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2003.01716.x
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  • 2
    Electronic Resource
    Electronic Resource
    Tyrosine Kinases Are Required for Catecholamine Secretion and Mitogen-Activated Protein Kinase Activation in Bovine Adrenal Chromaffin Cells (1996)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 66 (1996), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Nicotine-induced catecholamine secretion in bovine adrenomedullary chromaffin cells is accompanied by rapid tyrosine phosphorylation of multiple cellular proteins, most notably the mitogen-activated protein kinases (MAPKs). The requirement for activation of tyrosine kinases and MAPKs in chromaffin cell exocytosis was investigated using a panel of tyrosine kinase inhibitors. Genistein and tyrphostin 23, two compounds that inhibit tyrosine kinases by distinct mechanisms, were found to inhibit secretion by 〉90% in cells stimulated by nicotine, 55 mM KCI, or the Ca2+ ionophore A23187. Inhibition of secretion induced by all three secretagogues correlated with a block in both protein tyrosine phosphorylation and activation of the MAPKs and their activators (MEKs) in situ. However, neither genistein nor tyrphostin 23 inhibited the activities of the MAPKs or MEKs in vitro. These results indicate that the target(s) of inhibition lie down-stream of Ca2+ influx and upstream of MEK activation. This Ca2+-activated tyrosine kinase activity could not be accounted for entirely by c-Src or Fyn (two nonreceptor tyrosine kinases that are expressed abundantly in chromaffin cells), because their in vitro kinase activities were not inhibited by tyrphostin 23 and only partially inhibited by genistein. These results demonstrate that an unidentified Ca2+-activated tyrosine kinase(s) is required for MAPK activation and exocytosis in chromaffin cells and suggest that MAPK participates in the regulation of secretion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1996.66031103.x
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  • 3
    Electronic Resource
    Electronic Resource
    Corticosterone Has a Permissive Effect on Expression of Heme Oxygenase-1 in CA1–CA3 Neurons of Hippocampus in Thermal-Stressed Rats (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 64 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Activity of the stress protein, heme oxygenase-1 (hsp32; HO-1), produces carbon monoxide (CO), the potential messenger molecule for excitatory N-methyl-d-aspartate receptor-mediated events, in the hippocampus. Long-term stress caused by elevated adrenocorticoids induces pathological changes in CA1–CA3 neurons, of the hippocampus; the adrenal hormones also exacerbate damage from stress. In rats chronically treated with corticosterone, we examined expression of HO-1 and its response to thermal stress in the hippocampus. An unprecedented appearance of scattered immunoreactive astrocytes marked the molecular layer of the hippocampus in corticosterone-treated rats. Steroid treatment showed no discernible effect on whole-brain HO-1 mRNA. When these rats were subjected to hyperthermia, neurons in the CA1–CA3 area, including pyramidal cells, exhibited intense immunoreactivity for the oxygenase and a pronounced increase (∼10-fold) in number. HO-1 is essentially undetectable in this area when rats are exposed to chronic corticosterone alone or thermal stress by itself, or in control rats. In contrast, similar analysis of hilar neurons showed no apparent effect on either the number or relative intensity of HO-1-immunostained cells after treatment. Corticosterone treatment also intensified the stress response of cerebellum, including Purkinje cells and Bergmann glia in the molecular layer. In brain, despite a pronounced reduction in NO synthase activity in corticosterone-treated and/or heat-stressed animals, the level of cyclic GMP was not significantly reduced. These observations are consistent with the hypothesis that responsiveness to environmental stress of CA1–CA3 neurons brought about by chronic elevation in circulating adrenocorticoids results in an increased excitatory neuronal activity and eventual hippocampal degeneration. Moreover, these findings yield further support for a role of CO in the production of cyclic GMP in the brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.64041769.x
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  • 4
    Electronic Resource
    Electronic Resource
    Corticosterone Regulates Heme Oxygenase-2 and NO Synthase Transcription and Protein Expression In Rat Brain (1994)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 63 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Heme oxygenase (HO)-1 and -2 produce carbon monoxide, which is suspected, as is nitric oxide (NO), to function as a neuronal messenger. We report on glucocorticoid-mediated modulation of HO-2 and NO synthase expression in brain and the differential response of the two proteins to corticosterone in different brain regions. Corticosterone treatment (40 mg/kg, 20 days) had opposing effects on HO-2 and NO synthase transcript levels: increasing the 1.3- and 1.9-kb HO-2 mRNAs and decreasing that of the brain-specific 10.5-kb NO synthase. Corticosterone did not uniformly affect HO-2 protein expression in all regions, but appeared to cause a universal reduction in NO synthase, e.g., HO-2 was decreased in hippocampus (CA1 and dentate gyrus), but not in cerebellum. In contrast, NADPH diaphorase staining was reduced in hippocampus and in molecular and granule layers of cerebellum (not detected in Purkinje cells). Striking deficits in neuronal morphology and number of diaphorase-staining neurons were observed in the lateral tegmental area, paraventricular nucleus, and frontal cortex; HO-2 expression was only selectively affected. In cerebellum, activity of NO synthase, but not that of HO, was reduced. Consistent with the possibility that carbon monoxide can generate cyclic GMP, the change in cyclic GMP level did not mirror the decrease in NO synthase. We suggest that glucocorticoid-mediated deficits in hippocampal functions may reflect their negative effect on messenger-generating systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.63030953.x
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  • 5
    Electronic Resource
    Electronic Resource
    A Novel Orphan G Protein-Coupled Receptor Primarily Expressed in the Brain Is Localized on Human Chromosomal Band 2q21 (1998)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 70 (1998), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A human hippocampus cDNA library was screened with a probe obtained from degenerate RT-PCR aimed at P2Y-homologous sequences. A positive clone, designated hip4, was identified containing an open reading frame of 1,020 bp that had been previously detected in a published genomic clone called R12. Subsequent screening of a human fetal brain cDNA library yielded a splice variant with a 1,104-bp open reading frame, which was named fb1. Both variants display the seven-transmembrane topology that is typical for G protein-coupled receptors. Probing a human multitissue northern blot revealed two brain-specific transcripts of 2.3 and 6.3 kb, respectively. Northern blot analyses with specific fragments confirmed that the two transcripts are generated by alternative polyadenylation yielding two different 3′ untranslated regions. A genomic clone from the corresponding gene was isolated and mapped to human chromosomal band 2q21 by fluorescence in situ hybridization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1998.70041357.x
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  • 6
    Electronic Resource
    Electronic Resource
    Intracellular Free Calcium Dynamics in Stretch-Injured Astrocytes (1998)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 70 (1998), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We have previously developed an in vitro model for traumatic brain injury that simulates a major component of in vivo trauma, that being tissue strain or stretch. We have validated our model by demonstrating that it produces many of the posttraumatic responses observed in vivo. Sustained elevation of the intracellular free calcium concentration ([Ca2+]i) has been hypothesized to be a primary biochemical mechanism inducing cell dysfunction after trauma. In the present report, we have examined this hypothesis in astrocytes using our in vitro injury model and fura-2 microphotometry. Our results indicate that astrocyte [Ca2+]i is rapidly elevated after stretch injury, the magnitude of which is proportional to the degree of injury. However, the injury-induced [Ca2+]i elevation is not sustained and returns to near-basal levels by 15 min postinjury and to basal levels between 3 and 24 h after injury. Although basal [Ca2+]i returns to normal after injury, we have identified persistent injury-induced alterations in calcium-mediated signal transduction pathways. We report here, for the first time, that traumatic stretch injury causes release of calcium from inositol trisphosphate-sensitive intracellular calcium stores and may uncouple the stores from participation in metabotropic glutamate receptor-mediated signal transduction events. We found that for a prolonged period after trauma astrocytes no longer respond to thapsigargin, glutamate, or the inositol trisphosphate-linked metabotropic glutamate receptor agonist trans-(1S,3R)-1-amino-1,3-cyclopentanedicarboxylic acid with an elevation in [Ca2+]i. We hypothesize that changes in calcium-mediated signaling pathways, rather than an absolute elevation in [Ca2+]i, is responsible for some of the pathological consequences of traumatic brain injury.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1998.70062377.x
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  • 7
    Electronic Resource
    Electronic Resource
    6-Hydroxykynurenic acid and kynurenic acid differently antagonise AMPA and NMDA receptors in hippocampal neurones (2001)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 77 (2001), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: 6-Hydroxykynurenic acid (6-HKA), a derivative of kynurenic acid (KYNA) extracted from Ginkgo biloba leaves, was tested for its putative glutamate receptor (GluR) antagonism in comparison to the scaffold substance. The patch-clamp method together with fast-application techniques were used to estimate inhibition by 6-HKA and KYNA of agonist binding at NMDA and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors (NMDARs and AMPARs) of CA1 pyramidal neurones. 6-Hydroxykynurenic acid proved to be a low-affinity antagonist. When comparing with KYNA, 6-HKA was less potent at NMDARs (IC50 = 136 versus 59 µm), but showed a higher affinity to AMPARs (KB = 22 versus 172 µm). The replacement of 6-HKA and KYNA by glutamate was investigated on outside-out patches. Both antagonists competitively inhibited AMPAR responses and displayed fast unbinding kinetics, but the derivative was significantly slower displaced than KYNA (τ = 1.63 versus 1.22 ms). Our findings demonstrate that 6-hydroxylation considerably changes the pharmacological profile of KYNA. Among the 6-derivatives of KYNA, 6-HKA shows the highest affinity to AMPARs. Despite its relatively low lipophily, these properties might be of clinical relevance under conditions that compromise the integrity of the blood–brain barrier. Furthermore, 6-HKA should be a useful tool to analyse glutamate-mediated synaptic responses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2001.00340.x
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  • 8
    Electronic Resource
    Electronic Resource
    Phospholipase Cγ1 in Bovine Rod Outer Segments: Immunolocalization and Light-Dependent Binding to Membranes (1998)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 70 (1998), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We have investigated the isozymes of a phosphoinositide-specific phospholipase C (PLC) in bovine retina using several monoclonal antisera to PLCβ1, γ1, and δ1. Immunoblot analysis showed that all three isozymes were present in the retina. Immunocytochemical localization in frozen bovine retina sections showed that PLCγ1 was present in the photoreceptor cell layer, outer plexiform cell layer, inner plexiform cell layer, and ganglion cell layer. Immunoreaction within the photoreceptor cell layer was dependent on dark/light adaptation state of retinas. Immunoblot analysis of rod outer segments (ROS) with monoclonal or polyclonal antibodies to PLCγ1 showed the presence of an immunoreactive band of 140 kDa. ROS prepared from retinas light-adapted in vitro had more PLCγ1 on immunoblots than ROS from dark-adapted retinas. PLC enzyme activity in ROS from light-adapted retinas was 69 and 46% higher than ROS from dark-adapted retinas, when assayed in the presence and absence of ATP, respectively. This increase in enzyme activity was observed at [Ca2+]free between 0.32 and 100 µM. These results demonstrate the presence of PLCγ1 in bovine ROS and show that ROS prepared from light-adapted retinas are enriched in this isozyme, suggesting that light may promote the binding of this isozyme to bleached ROS membranes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1998.70010171.x
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  • 9
    Electronic Resource
    Electronic Resource
    Intrastriatal Grafting of Cos Cells Stably Expressing Human Aromatic l-Amino Acid Decarboxylase: Neurochemical Effects (1997)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 68 (1997), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: To study the possibility that increasing striatal activity of aromatic l-amino acid decarboxylase (AADC; EC 4.1.1.28) can increase dopamine production in dopamine denervated striatum in response to l-3,4-dihydroxyphenylalanine (l-DOPA) administration, we grafted Cos cells stably expressing the human AADC gene (Cos-haadc cells) into 6-hydroxydopamine denervated rat striatum. Before grafting, the catalytic activity of the enzyme was assessed in vitro via the generation of 14CO2 from l-[14C]DOPA. The Km value for l-DOPA in intact and disrupted cells was 0.60 and 0.56 mM, respectively. The cofactor, pyridoxal 5-phosphate, enhanced enzymatic activity with maximal effect at 0.1 mM. The pH optimum for enzyme activity was 6.8. Grafting Cos-haadc cells into denervated rat striatum enhanced striatal dopamine levels measured after systemic administration of l-DOPA. When measured 2 h after l-DOPA administration, the mean dopamine level in the striata of Cos-haadc-grafted animals was 2 µg/g of tissue, representing 31% of normal striatal dopamine concentration. The mean dopamine concentration in the striata grafted with untransfected Cos cells (Cos-ut cells) was 1 µg/g. At 6–8 h after l-DOPA administration, striatal dopamine content in the Cos-haadc-grafted animals was 0.67 µg/g of tissue weight, representing 9% of intact striatum dopamine content. By contrast, the average dopamine content in the Cos-ut-grafted animals was undetectable. These findings demonstrate that enhancing striatal AADC activity can improve dopamine bioformation in response to systemically administered l-DOPA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1997.68041520.x
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  • 10
    Electronic Resource
    Electronic Resource
    Cutaneous leukaemic infiltrations in a patient with previously undiagnosed myelodysplastic syndrome (2004)
    Oxford, UK : Blackwell Science Ltd
    Clinical and experimental dermatology 29 (2004), S. 0 
    Details
    ISSN: 1365-2230
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We report the rare case of a patient with leukaemia cutis first presenting only on the hand and fingers and then subsequently spreading over the trunk and face. The lesions heralded the transformation of a previously undiagnosed myelodysplastic syndrome type RAEB (refractory anaemia with blast excess) into frank myeloid leukaemia. The haematological disease was first detected by the dermatohistopathologist. This case underlines the need to look meticulously for skin changes and perform early skin biopsies in haematological patients, as the skin can reveal the first clinical signs of an otherwise not evident bone marrow disorder. Leukaemia cutis as the initial clinical presentation of a transforming myelodysplastic syndrome type RAEB into acute myeloid leukaemia has been reported only very rarely.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2230.2004.01550.x
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