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  • 1
    Electronic Resource
    Electronic Resource
    Sodium-Dependent Uptake of Nucleosides by Dissociated Brain Cells from the Rat (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 52 (1989), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Sodium-dependent 3H-labeled nucleoside transport was studied using a mixed population of dissociated brain cells from adult rats. The accumulation of [3H]adenosine during brief (15-s) incubation periods was significantly greater in the presence of 110 μM Na+ than in its absence. This occurred at substrate concentrations that ranged from 0.25 to 100 μM. Similar findings were observed for the rapid accumulation of [3H]uridine. Kinetically, the rapid accumulation of [3H]adenosine in both the absence and the presence of Na+ was best described by a two-component system. In the presence of Na+, the KT and Vmax values for the high-affinity component were 0.9 μM and 8.9 pmol/mg of protein/15 s, and those for the low-affinity component were 313 μM and 3,428 pmol/mg of protein/15 s, respectively. In the absence of Na+, the KT value for the high-affinity component was significantly higher (1.8 μM). [3H]Uridine accumulation was best described kinetically by a one-component system that in the presence of Na+ had KT and Vmax values of 1.0 mM and 2.6 nmol/mg of protein/15 s, respectively. As was found for [3H]adenosine, in the absence of Na+, the KT value was significantly higher (1.8 mM). The sodium-dependent transport of [3H]adenosine was inhibitable by ouabain and 2,4-dinitrophenol. Of the three nucleoside transport inhibitors tested, only nitrobenzylthioinosine demonstrated high affinity and selectivity in blocking the sodium component. Thus, high-affinity sodium-dependent nucleoside transport systems, in addition to facilitated diffusion systems, exist on brain cells from adult rats.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb10900.x
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  • 2
    Electronic Resource
    Electronic Resource
    Caffeine Stimulates Amyloid β-Peptide Release from β-Amyloid Precursor Protein-Transfected HEK293 Cells (1997)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 69 (1997), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Extracellular amyloid β-peptide (Aβ) deposition is a pathological feature of Alzheimer's disease and the aging brain. Intracellular Aβ accumulation is observed in the human muscle disease, inclusion body myositis. Aβ has been reported to be toxic to neurons through disruption of normal calcium homeostasis. The pathogenic role of Aβ in inclusion body myositis is not as clear. Elevation of intracellular calcium following application of calcium ionophore increases the generation of Aβ from its precursor protein (βAPP). A receptor-based mechanism for the increase in Aβ production has not been reported to our knowledge. Here, we use caffeine to stimulate ryanodine receptor (RYR)-regulated intracellular calcium release channels and show that internal calcium stores also participate in the genesis of Aβ. In cultured HEK293 cells transfected with βAPP cDNA, caffeine (5–10 mM) significantly increased the release of Aβ fourfold compared with control. These actions of caffeine were saturable, modulated by ryanodine, and inhibited by the RYR antagonists ruthenium red and procaine. The calcium reuptake inhibitors thapsigargin and cyclopiazonic acid potentiated caffeine-stimulated Aβ release. NH4Cl and monensin, agents that alter acidic gradients in intracellular vesicles, abolished both the caffeine and ionophore effects. Immunocytochemical studies showed some correspondence between the distribution patterns of RYR and cellular βAPP immunoreactivities. The relevance of these findings to Alzheimer's disease and inclusion body myositis is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1997.69041580.x
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  • 3
    Electronic Resource
    Electronic Resource
    Distribution of Equilibrative, Nitrobenzylthioinosine-Sensitive Nucleoside Transporters (ENT1) in Brain (1999)
    Oxford UK : Blackwell Science Ltd.
    Journal of neurochemistry 73 (1999), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract : Nucleoside transport processes may play a role in regulating endogenous levels of the inhibitory neuromodulator adenosine in brain. The cDNAs encoding species homologues of one member of the equilibrative nucleoside transporter (ENT) gene family have recently been isolated from rat (rENT1) and human (hENT1) tissues. The current study used RT-PCR, northern blot, in situ hybridization, and [3H]nitrobenzylthioinosine autoradiography to determine the distribution of mRNA and protein for ENT1 in rat and human brain. Northern blot analysis indicated that hENT1 mRNA is widely distributed in adult human brain. 35S-labeled sense and antisense riboprobes, transcribed from a 153-bp segment of rENT1, were hybridized to fresh frozen coronal sections from adult rat brain and revealed widespread rENT1 mRNA in pyramidal neurons of the hippocampus, granule neurons of the dentate gyrus, Purkinje and granule neurons of the cerebellum, and cortical and striatal neurons. Regional localization in rat brain was confirmed by RT-PCR. Thus, ENT1 mRNA has a wide cellular and regional distribution in brain, indicating that this nucleoside transporter subtype may be important in regulating intra- and extracellular levels of adenosine in brain.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1999.0730867.x
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  • 4
    Electronic Resource
    Electronic Resource
    Secreted Form of Amyloid Precursor Protein Enhances Basal Glucose and Glutamate Transport and Protects Against Oxidative Impairment of Glucose and Glutamate Transport in Synaptosomes by a Cyclic GMP-Mediated Mechanism (1999)
    Oxford UK : Blackwell Science Ltd.
    Journal of neurochemistry 73 (1999), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract : Synaptic dysfunction and degeneration are believed to underlie the cognitive deficits that characterize Alzheimer's disease, and overactivation of glutamate receptors under conditions of increased oxidative stress and metabolic compromise may contribute to the neurodegenerative process in many different disorders. The secreted form of amyloid precursor protein (sAPPα), which is released from neurons in an activity-dependent manner, can modulate neurite outgrowth, synaptic plasticity, and neuron survival. We now report that sAPPα can enhance glucose and glutamate transport in synaptic compartments. Treatment of cortical synaptosomes with nanomolar concentrations of sAPPα resulted in an attenuation of impairment of glutamate and glucose transport induced by exposure to amyloid β-peptide and Fe2+. The protective effect of sAPPα was mimicked by treatment with 8-bromo-cyclic GMP and blocked by a cyclic GMP-dependent protein kinase inhibitor, suggesting that protective action of sAPPα is mediated by cyclic GMP. Our data suggest that glucose and glutamate transport can be regulated locally at the level of the synapse and further suggest important roles for sAPPα and cyclic GMP in modulating synaptic physiology under normal and pathophysiological conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1999.0730532.x
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  • 5
    Electronic Resource
    Electronic Resource
    Enzymes of adenosine metabolism in the brain: diurnal rhythm and the effect of sleep deprivation (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: Adenosine plays a role in promoting sleep, an effect that is thought to be mediated in the basal forebrain. Adenosine levels vary in this region with prolonged wakefulness in a unique way. The basis for this is unknown. We examined, in rats, the activity of the major metabolic enzymes for adenosine – adenosine deaminase, adenosine kinase, ecto- and cytosolic 5′-nucleotidase – in sleep/wake regulatory regions as well as cerebral cortex, and how the activity varies across the day and with sleep deprivation. There were robust spatial differences for the activity of adenosine deaminase, adenosine kinase, and cytosolic and ecto-5′-nucleotidase. However, the basal forebrain was not different from other sleep/wake regulatory regions apart from the tuberomammillary nucleus. All adenosine metabolic enzymes exhibited diurnal variations in their activity, albeit not in all brain regions. Activity of adenosine deaminase increased during the active period in the ventrolateral pre-optic area but decreased significantly in the basal forebrain. Enzymatic activity of adenosine kinase and cytosolic-5′-nucleotidase was higher during the active period in all brain regions tested. However, the activity of ecto-5′-nucleotidase was augmented during the active period only in the cerebral cortex. This diurnal variation may play a role in the regulation of adenosine in relationship to sleep and wakefulness across the day. In contrast, we found no changes specifically with sleep deprivation in the activity of any enzyme in any brain region. Thus, changes in adenosine with sleep deprivation are not a consequence of alterations in adenosine enzyme activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.2003.01687.x
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  • 6
    Electronic Resource
    Electronic Resource
    Interactions of the human immunodeficiency virus with astrocytes (1996)
    Springer
    Perspectives in drug discovery and design 5 (1996), S. 30-42 
    Details
    ISSN: 1573-9023
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Infection with the human immunodeficiency virus type 1 (HIV-1) can cause a dementing illness. Astrocytes, the most numerous cells within the central nervous system, can be infected with HIV-1. These cells are infected by predominantly lymphotropic strains of HIV-1. The mode of infection does not involve CD4 or galactocerebroside C and is, most likely, due to a unique binding-site protein located on the surface of astrocytes. The virus produces low levels of infection. Astrocytic function is significantly altered by viral proteins and nonviral products released by other infected cells. Future therapeutic developments for treating HIV-1 infection will need to take into account the unique mechanisms of interaction of HIV-1 with astrocytes. This review discusses astrocyte involvement in the pathogenesis of the HIV-1 cognitive motor complex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02173999
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