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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: U-78518F, a 21-aminosteroid from the novel family of lipid peroxidation inhibitors (lazaroids), increased survival of dopamine (DA) neurons in mesencephalic cell cultures incubated with the neurotoxin l-methyl-4-phenylpyridinium (MPP+). Protection against DA neuron death occurred with increasing concentrations of U-78518F up to 30 μM. Nonspecific toxicity produced with higher concentrations of MPP+ was not affected by the lazaroid. U-78518F inhibited cellular uptake of [3H]MPP+ and [3H]DA, but not that of γ-[3H]aminobutyric acid. In human striatal membrane preparations, U-78518F competed with [3H]mazindol for binding to the DA transporter, with a calculated Ki value of 10 μM. Two of four lazaroids tested inhibited [3H]DA uptake in the cell culture system. The protective effects of 21-aminosteroids in MPP+-induced neurotoxicity are, in part, a function of the interaction of these agents with the DA transporter.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Dopaminergic neurons in cultures of dissociated cells from fetal rat mesencephalon were exposed to the principal metabolite of the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), 1-methyl-4-phenyl-pyridinium ion (MPP+), and several of its structural analogues. At concentrations between 0.01 and 0.1 μM, MPP+ inhibited catecholamine accumulation as visualized by cytofluorescence. Between 0.1 and 10.0 μM, MPP+ resulted in disappearance of tyrosine hydroxylase immunoreactivity without affecting other cells in the cultures. At concentrations higher than 10 μM, MPP+ was toxic to all cells present in the cultures. The effect of low concentrations of MPP+ on catecholamine cytofluorescence of the dopaminergic neurons was partially reversible. The intermediate concentrations produced irreversible structural changes of tyrosine hydroxylase-positive cells, resulting in complete disappearance of these neurons. The morphological changes were specific to the dopaminergic neurons and were not evident in other cells viewed with phase contrast microscopy. Of the structural analogues tested, the 1-ethyl analogue of MPP+ was effective in selectively destroying dopaminergic neurons in our culture system. The antioxidants l-acetylcarnitine, β-carotene, and α-tocopherol failed to protect against MPP+ neurotoxicity when co-incubated with the toxin.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 55 (1990), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Transferrin receptors were characterized with 125Iferrotransferrin on membrane fractions prepared from the rodent forebrain. The distribution of transferrin receptors in the rat brain was investigated further by in vitro autoradiography. Saturation binding analysis revealed an apparent single class of sites with a dissociation constant of 2 nM and a binding site density of 15 pmol/g. The Hill coefficient derived from these data was 1.05. indicating the absence of cooperativity and that 125I-ferrotransferrin binds to a single class of sites. Estimates of the kinetically determined Kd for forebrain membranes were within the 2–4 nM range, in agreement with the equilibrium measurements. Apotransferrin and ferrotransferrin competitively displaced the binding of 125I-ferrotransferrin, while ferritin, albumin, and cytochrome c failed to compete for the binding site. Ceruloplasmin, the copper transport protein, was a weak inhibitor of 125I-ferrotransferrin binding. Autoradiographic localization studies demonstrate a heterogeneous distribution of transferrin receptors in the rat brain. Transferrin receptor densities were markedly elevated over the cerebral cortex and the hippocampus. Moderate to high 125I-ferrotransferrin binding was also apparent throughout areas involved in motor functions, including the caudate-putamen, the nucleus accumbens, the substantia nigra, the red nucleus, and the cerebellum.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 570 (1989), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 537 (1988), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2072
    Keywords: 5-Hydroxytryptophan ; Serotonin ; Neuroleptics ; Methysergide ; Dopamine ; Hyper-sensitivity ; Apomorphine ; Amphetamine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It has been proposed that prolonged pharmacologic blockade of specific receptor sites by specific antagonists results in specific denervation hypersensitivity. The exact specificity of such antagonist-induced behavioral hypersensitivity has not previously been investigated. The present study was undertaken to determine whether hypersensitivity induced by a chronic dopamine antagonist (chlorpromazine or haloperidol) and by a serotonin antagonist (methysergide) is specific to their respective agonists or whether the induced physiologic alterations are more generalized. Chlorpromazine, haloperidol, or methysergide was given to guinea pigs daily for 21 days and the subsequent behavioral responses to d-amphetamine, apomorphine, and d,l-5-hydroxytryptophan were observed. Chronic dopaminergic antagonism resulted in hypersensitivity to dopamine agonism but did not change the response to serotonin agonism as gauged by 5-hydroxytryptophan-induced stereotypy. Chronic serotonin antagonism was shown to result in hypersensitivity to serotonin agonism, which was not associated with any increase in the behavioral response to either direct or indirect dopamine antagonists. These findings indicate that the chronic administration of dopamine and serotonin antagonists results in behavioral hypersensitivity, which is limited to the system antagonized, and that antagonist-induced hypersensitivity involves the transmitter-specific receptors blocked by the antagonist in question.
    Type of Medium: Electronic Resource
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