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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We report here the characterization of a full-length cDNA encoding the human myelin/oligodendrocyte glycoprotein (MOG). The sequence of the coding region of the human MOG cDNA is highly homologous to that of other previously cloned mouse, rat, and bovine MOG cDNAs, but the 3′ untranslated region differs by an insertion of an Alu sequence between nucleotides 1,590 and 1,924. Accordingly, northern blot analyzes with cDNA probes corresponding to the coding region or the 3′ untranslated Alu-containing sequence revealed a single band of 2 kb, rather than the 1.6 kb of bovine, rat, or mouse MOG cDNA(s). Immunocytochemical analysis of HeLa cells transfected with human MOG cDNA, which was performed using a specific antibody raised against whole MOG, clearly indicated that MOG is expressed at the cell surface as an intrinsic protein. These data are in accordance with the predicted amino acid sequence, which contains a signal peptide and two putative transmembrane domains. The knowledge of the human MOG sequence should facilitate further investigations on its potential as a target antigen in autoimmune demyelinating diseases like multiple sclerosis.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 66 (1996), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The death of dopaminergic and other neurons in primary cultures of the mesencephalon could be induced by treatment with ceramide, as in lymphocytes where it mediates activation by the cytokines tumor necrosis factor-α and interleukin-1β of a novel sphingomyelin-dependent signaling pathway leading to apoptosis. The morphological hallmarks of this form of cell death—bleb formation, cell body shrinkage, nuclear chromatin condensation, and fragmentation—were observed in degenerating neurons. Internucleosomal DNA degradation could also be evidenced by gel electrophoresis. The C2 and C6 analogues as well as native ceramide, administered in a dodecane suspension, had a similar effect, whereas the closely related C2-dihydroceramide, which lacks the 4–5 trans double bond in the sphingosine chain, failed to induce apoptosis. Neuronal death could be delayed by serum factors, dibutyryl cyclic AMP, and the protein synthesis inhibitor cycloheximide.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Reduced activity of the mitochondrial respiratory chain – particularly complex I – may be implicated in the etiology of both Parkinson's disease and progressive supranuclear palsy, although these neurodegenerative diseases differ substantially as to their distinctive pattern of neuronal cell loss and the predominance of cerebral α-synuclein or tau protein pathology. To determine experimentally whether chronic generalized complex I inhibition has an effect on the distribution of α-synuclein or tau, we infused rats systemically with the plant-derived isoflavonoid rotenone. Rotenone-treated rats with a pronounced metabolic impairment had reduced locomotor activity, dystonic limb posture and postural instability. They lost neurons in the substantia nigra and in the striatum. Spherical deposits of α-synuclein were observed in a few cells, but cells with abnormal cytoplasmic accumulations of tau immunoreactivity were significantly more numerous in the striatum of severely lesioned rats. Abnormally high levels of tau immunoreactivity were found in the cytoplasm of neurons, oligodendrocytes and astrocytes. Ultrastructurally, tau-immunoreactive material consisted of straight 15-nm filaments decorated by antibodies against phosphorylated tau. Many tau+ cell bodies also stained positive for thioflavin S, nitrotyrosine and ubiquitin. Some cells with abnormal tau immunoreactivity contained activated caspase 3. Our data suggest that chronic respiratory chain dysfunction might trigger a form of neurodegeneration in which accumulation of hyperphosphorylated tau protein predominates over deposits of α-synuclein.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Two biochemical deficits have been described in the substantia nigra in Parkinson's disease, decreased activity of mitochondrial complex I and reduced proteasomal activity. We analysed interactions between these deficits in primary mesencephalic cultures. Proteasome inhibitors (epoxomicin, MG132) exacerbated the toxicity of complex I inhibitors [rotenone, 1-methyl-4-phenylpyridinium (MPP+)] and of the toxic dopamine analogue 6-hydroxydopamine, but not of inhibitors of mitochondrial complex II–V or excitotoxins [N-methyl-d-aspartate (NMDA), kainate]. Rotenone and MPP+ increased free radicals and reduced proteasomal activity via adenosine triphosphate (ATP) depletion. 6-hydroxydopamine also increased free radicals, but did not affect ATP levels and increased proteasomal activity, presumably in response to oxidative damage. Proteasome inhibition potentiated the toxicity of rotenone, MPP+ and 6-hydroxydopamine at concentrations at which they increased free radical levels ≥ 40% above baseline, exceeding the cellular capacity to detoxify oxidized proteins reduced by proteasome inhibition, and also exacerbated ATP depletion caused by complex I inhibition. Consistently, both free radical scavenging and stimulation of ATP production by glucose supplementation protected against the synergistic toxicity. In summary, proteasome inhibition increases neuronal vulnerability to normally subtoxic levels of free radicals and amplifies energy depletion following complex I inhibition.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Levodopa, the major treatment for patients with Parkinson's disease, has been shown to induce a variety of compensatory effects, including facilitation of sprouting by dopaminergic neurons, in experimental animals with lesions leading to denervation of the striatum. To better understand the cellular and molecular environment where most of these compensatory changes take place, in particular elements that might contribute to the recovery of dopaminergic innervation, we have constructed a differential expression library enriched in transcripts from the striata of rats with lesions of the medial forebrain bundle treated with levodopa for 6 months. We have used this library to screen an expression array of rat genes representing the major cell functions, and have identified several that are involved in neurotrophic mechanisms and plasticity. We have confirmed the differential expression of selected transcripts by non-radioactive in situ hybridization, and report that the growth factor pleiotrophin, myelin basic protein and calmodulin are overexpressed in the denervated striatum of levodopa-treated rats.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In Guadeloupe, epidemiological data have linked atypical parkinsonism with fruit and herbal teas from plants of the Annonaceae family, particularly Annona muricata. These plants contain a class of powerful, lipophilic complex I inhibitors, the annonaceous acetogenins. To determine the neurotoxic potential of these substances, we administered annonacin, the major acetogenin of A. muricata, to rats intravenously with Azlet osmotic minipumps (3.8 and 7.6 mg per kg per day for 28 days). Annonacin inhibited complex I in brain homogenates in a concentration-dependent manner, and, when administered systemically, entered the brain parenchyma, where it was detected by matrix-associated laser desorption ionization – time of flight mass spectrometry, and decreased brain ATP levels by 44%. In the absence of evident systemic toxicity, we observed neuropathological abnormalities in the basal ganglia and brainstem nuclei. Stereological cell counts showed significant loss of dopaminergic neurones in the substantia nigra (− 31.7%), and cholinergic (− 37.9%) and dopamine and cyclic AMP-regulated phosphoprotein (DARPP-32)-immunoreactive GABAergic neurones (− 39.3%) in the striatum, accompanied by a significant increase in the number of astrocytes (35.4%) and microglial cells (73.4%). The distribution of the lesions was similar to that in patients with atypical parkinsonism. These data are compatible with the theory that annonaceous acetogenins, such as annonacin, might be implicated in the aetiology of Guadeloupean parkinsonism and support the hypothesis that some forms of parkinsonism might be induced by environmental toxins.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The death of dopaminergic neurons that occurs spontaneously in mesencephalic cultures was prevented by depolarizing concentrations of K+ (20–50 mm). However, unlike that observed previously in other neuronal populations of the PNS or CNS, promotion of survival required concurrent blockade of either NMDA or α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA)/kainate receptors by the specific antagonists, MK-801 and GYKI-52466, respectively. Rescued neurons appeared to be healthy and functional because the same treatment also dramatically enhanced their capacity to accumulate dopamine. The effects on survival and uptake were rather specific to dopaminergic neurons, rapidly reversible and still observed when treatment was delayed after plating. Glutamate release increased substantially in the presence of elevated concentrations of K+, and chronic treatment with glutamate induced a loss of dopaminergic neurons that was prevented by MK-801 or GYKI-52466 suggesting that an excitotoxic process interfered with survival when only the depolarizing treatment was applied. The effects of the depolarizing stimulus in the presence of MK-801 were mimicked by BAY K-8644 and abolished by nifedipine, suggesting that neuroprotection resulted from Ca2+ influx through L-type calcium channels. Measurement of intracellular calcium revealed that MK-801 or GYKI-52466 were required to maintain Ca2+ levels within a trophic range, thus preventing K+-induced excitotoxic stress and Ca2+ overload. Altogether, our results suggest that dopaminergic neurons may require a finely tuned interplay between glutamatergic receptors and calcium channels for their development and maturation.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: In Parkinson’s disease, nigrostriatal denervation leads to an overactivity of the subthalamic nucleus and its target areas, which is responsible of the clinical manifestations of the disease. Because the subthalamic nucleus uses glutamate as neurotransmitter and is innervated by glutamatergic fibers, pharmacological blockade of glutamate transmission might be expected to restore the cascade of neurochemical changes induced by a dopaminergic denervation within the basal ganglia. To test this hypothesis, two types of glutamate antagonists, the NMDA receptor antagonist MK-801 and the α-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor antagonist LY293558, were administered systemically, either alone or in combination with L-DOPA, in rats with a unilateral 6-hydroxydopamine lesion of the nigrostriatal dopamine pathway. The effect of treatment was assessed neurochemically by analyzing at the cellular level the functional activity of basal ganglia output structures and the subthalamic nucleus using the expression levels of the mRNAs coding for glutamic acid decarboxylase and cytochrome oxidase, respectively, as molecular markers of neuronal activity. The present study shows that treatment with glutamate antagonists, and particularly with AMPA antagonists, alone or in combination with L-DOPA, reverses the overactivity of the subthalamic nucleus and its target areas induced by nigrostriatal denervation. These results furnish the neurochemical basis for the potential use of glutamate antagonists as therapeutic agents in Parkinson’s disease.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 72 (1999), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The purinergic nucleoside adenosine effectively prevented the death of dopaminergic neurons that occurs spontaneously and progressively in cultures of rat mesencephalon. Adenosine also significantly increased dopamine uptake, attesting to the state of differentiation and functional integrity of the neurons that were rescued. The effects of adenosine were (a) specific to the dopaminergic neurons in these cultures, (b) long-lived, (c) still observed when the treatment was delayed after plating, (d) potentiated by inhibition of adenosine deaminase, and (e) abolished when this enzyme was added in excess to the culture medium. The action of adenosine was mimicked by 5′-(N-ethylcarboxamido)adenosine and dibutyryl-cyclic AMP, but not by CGS-21680, suggesting the possible involvement of A2B subtype purinergic receptors. ATP was also neuroprotective, but its action resulted principally from conversion to adenosine by ectonucleotidases. Several anticancer drugs, including cytosine arabinoside, have been shown previously to prevent apoptosis in cultured dopaminergic neurons by a mechanism that requires the inhibition of proliferating astrocytes. In the presence of adenosine, astrocytes were more differentiated, and their proliferation rate was significantly reduced, suggesting that the neurotrophic effect of the adenine nucleoside resulted also from the repression of the astroglial cells. We did not find evidence of a trophic intermediary in adenosine-treated cultures, however, leading to the hypothesis that limitation of astrocyte replication in itself and/or ensuing changes in the glial phenotype were crucial. Our results suggest that molecules that modulate adenine nucleotide/nucleoside release may be useful for the treatment of chronic neurodegenerative conditions affecting dopaminergic neurons, such as Parkinson's disease.
    Type of Medium: Electronic Resource
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  • 10
    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: Nanomolar concentrations of cytosine arabinoside (ara-C), a structural analogue of 2′-deoxycytidine (2′dC) used in the chemotherapy of cancer, proved to be highly effective in preventing the death of postmitotic dopaminergic neurons that occurs spontaneously by apoptosis in mesencephalic cultures. The rescued cells were totally functional and highly differentiated. The trophic/neuroprotective effects of ara-C were (1) specific for dopaminergic neurons; (2) long-lived, remaining detectable several days after withdrawal of the nucleoside analogue from the culture medium; (3) still observed when the treatment was delayed after plating; (4) abolished by an excess of 2′dC or dCTP, or by exposure to the neurotoxin 1-methyl-4-phenylpyridinium; and (5) mimicked by ara-CTP, 5-fluoro-2′-deoxyuridine, and aphidicolin. Autoradiographic studies revealed that ara-C was incorporated exclusively into astrocyte nuclei, suggesting that the dopaminotrophic activity was indirect and resulted from the antiproliferative action of the modified nucleoside on glial cells at concentrations that were not neurotoxic. No evidence was found for putative deleterious or trophic molecules secreted by proliferating or ara-C-treated astrocytes, respectively, suggesting that neuroglial contact may play a role. Our results suggest a possible mechanism underlying neurodegeneration in Parkinson's disease, where selective loss of dopaminergic neurons in the mesencephalon is accompanied by astrogliosis.
    Type of Medium: Electronic Resource
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