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  • 1995-1999  (4)
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  • 1
    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
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 69 (1997), S. 0 
    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
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  • 3
    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
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Perspectives in drug discovery and design 5 (1996), S. 30-42 
    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
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