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  • 1
    Electronic Resource
    Electronic Resource
    [3H]N-[1-(2-Thienyl)cyclohexyl]-3,4-Piperidine ([3H]TCP) Binding in Human Frontal Cortex: Decreases in Alzheimer-Type Dementia (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 54 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: We studied [3H]N-[1-(2-thienyl)cyclohexyl]-3,4-piperidine ([3H]TCP) binding to human frontal cortex obtained at autopsy from 10 histologically normal controls and eight histopathologically verified cases with Alzheimer-type dementia (ATD). Extensively washed membrane preparations were used to minimize the effects of endogenous substances. In ATD frontal cortex, the total concentration (Bmax) of [3H]TCP binding sites was significantly reduced by 40–50%. The apparent dissociation constant (KD) values showed no significant change. The reduction in binding capacity was also apparent in Triton X-100–treated membrane preparations, and there was a linear correlation between the number of [3H]TCP binding sites and that of N-methyl-D-aspartate (NMDA)-sensitive [3H]glutamate binding sites. [3H]TCP binding sites spared in ATD brains retained the affinity for the ligand and the reactivity to NMDA, L-glutamate, and glycine. These results suggest that the primary change in NMDA receptor-ion channel complex in ATD brains is the reduction of its number, possibly reflecting the loss of neurons bearing these receptor complexes, and that the functional linkage within the receptor complexes spared in ATD brains remains normal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb01903.x
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  • 2
    Electronic Resource
    Electronic Resource
    Phosphoinositide Breakdown in Rat Hippocampal Slices: Sensitivity to Glutamate Induced by In Vitro Anoxia (1990)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 55 (1990), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We examined the effects of in vitro anoxia on phosphoinositide (PI) breakdown in rat hippocampal slices stimulated by glutamate and quisqualate. In addition to assays of accumulations of 3H-inositol phosphates (3H-IPs) degraded from prelabeled PI, we adopted direct assay procedures of inositol 1,4,5-triphosphate (1,4,5-IP3) using l,4,5-IP3-specific binding protein to determine the formation of 1,4,5-IP3. The first effect, observed with anoxic incubation by itself, was the diminished quisqualate (10--5M)-stimulated accumulation of 3H-IPs degraded from prelabeled PI under prolonged anoxia. Quisqualate caused a transient increase in 1,4,5-IP3 formation in the early phase of anoxia, similar to that under oxygenated conditions. Glutamate (10--5M), under normal conditions, influenced neither the accumulation of 3H-IPs nor the formation of 1,4,5-IP3. Also, the accumulation of 3H-IPs under prolonged anoxia was unaffected. The same concentration of glutamate, however, gave rise to a transient increase in 1,4,5-IP3 content in the early phase of anoxia, similar to that caused by quisqualate. The second effect, observed by oxygenation following anoxia, was the induction of glutamate-stimulated accumulation of 3H-IPs. When the hippocampal slices were oxygenated following a sufficiently long (〉30-min) exposure to anoxia, glutamate (10--5M) caused a significant increase in accumulation of 3H-IPs degraded from prelabeled PI. Quisqualate-stimulated accumulation of 3H-IPs under oxygenated incubations was also increased by prior exposure of slices to anoxia. These results support the hypothesis that an exposure of hippocampal slices to anoxia induces a sensitivity of the PI breakdown pathway to glutamate and that, given an oxygen supply following sufficiently long exposure to anoxia, the slices maintain their sensitivity to glutamate with an apparent increase in the accumulation of 3H-IPs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1990.tb04589.x
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of Oxygen Depletion on Norepinephrine- and Carbachol-Stimulated Phosphoinositide Turnover in Rat Brain Slices (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 53 (1989), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We examined the effects of in vitro anoxia and in vivo hypoxia (8% 02/92% N2) on norepinephrine (NE)- and carbachol-stimulated phosphoinositide (PI) turnover in rat brain slices. The formation of 3H-labeled polyPI in cortical slices was impaired by in vitro anoxia and fully restored by reoxygenation. Accumulation of 3H-labeled myo-inositol phosphates (3H-IPs) stimulated by 10−5M NE was significantly reduced by anoxia (control at 60 min, 1,217 ± 86 cpm/mg of protein; anoxia for 60 min, 651 ±82 cpm/mg; mean ± SEM; n =5;p 〉 0.01), and reoxygenation following anoxia resulted in overshooting of the accumulation (control at 120 min, 1,302 ± 70 cpm/mg; anoxia for 50 min plus oxygenation for 70 min, 1,790 ± 126 cpm/mg; n = 5; p 〉 0.01). The underlying mechanisms for the two phenomena—the decrease caused by anoxia and the overshooting caused by reoxygenation following anoxia—seemed to be completely different because of the following observations, (a) Although the suppression of NE-stimulated accumulation at low 02 tensions was also observed in Ca2+-free medium, the overshooting in response to reoxygenation was not. (b) Carbachol-stimulated accumulation was significantly reduced by anoxia and was restored by reoxygenation only to control levels. Thus, the postanoxic overshooting in accumulation of 3H-IPs seems to be a specific response to NE. (c) The decrease observed at low 02 tensions was due to a decrease in Emax value, whereas the postanoxic overshooting was due to a decrease in EC50 value. There was also a significant increase in NE-stimulated accumulation of 3H-IPs in cortical slices from rats exposed to in vivo hypoxia (8% 02/92% N2) for 〈6 h, compared with those from rats exposed to room air. These results indicate that depletion of oxygen causes significant changes in receptor-mediated PI metabolism in brain slices and may provide a clue for understanding biochemical mechanisms for the electrophysiologically demonstrable effects of hypoxia/anoxia on synaptic transmission.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1989.tb07312.x
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  • 4
    Electronic Resource
    Electronic Resource
    Increased Binding of [3H]Muscimol and [3H]Flunitrazepam in the Rat Brain Under Hypoxia (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 51 (1988), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We examined the effects of in vivo hypoxia (10% O2/90% N2) on the γ-aminobutyric acid (GABA)/benzo-diazepine receptors and on glutamic acid decarboxylase (GAD) activity in the rat brain. Male Wistar rats were exposed to a mixture of 10% O2 and 90% N2 in a chamber for various periods (3, 6, 12, and 24 h). The control rats were exposed to room air. The brain regions examined were the cerebral cortex, striatum, hippocampus, and cerebellum. GABA and benzodiazepine receptors were assessed using [3H]muscimol and [3H]flunitrazepam, respectively. Compared with control values, GAD activity was decreased significantly following a 6-h exposure to hypoxia in all four regions studied. On the other hand, the numbers of both [3H]muscimol and [3H]flunitrazepam binding sites were increased significantly. The increase in receptor number tended to return to control values after 24 h. Treatment of the membrane preparations with 0.05% Triton X-100 eliminated the increase in the binding capacity. These results may represent an up-regulation of postsynaptically located GABA/benzodiazepine receptors corresponding to the impaired presynaptic activity under hypoxia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1988.tb03075.x
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  • 5
    Electronic Resource
    Electronic Resource
    Biologically Active Domain of the Secreted Form of the Amyloid β/A4 Protein Precursor (1993)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 695 (1993), S. 0 
    Details
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Notes: The amyloid β/A4 protein precursor (APP), a large transmembrane protein, is expressed ubiquitously in many organisms, as well as in a variety of cultured cells. Studies of the synthesis and processing of APP have revealed several intricate metabolic pathways for this protein. One of these pathways involves the cleavage of APP in the middle of the β/A4 domain and results in the secretion of the large amino-terminal portion of the protein. The biological function of this secreted form of APP has been the subject of intense investigation by several groups and various activities have been described for the different domains of APP studied. Our initial approach was to create a fibroblast cell line in which APP expression is dramatically reduced. These fibroblasts, called A-1, have a very slow growth rate. Addition of exogenous APP in the medium of A-1 cells restores their growth to the level of normal parent fibroblasts, demonstrating a growth factor-like activity for the secreted form of APP. Using APP fragments made in bacteria as well as synthetic peptides, we have been able to locate the active site of APP within a domain of 17 amino-acids (Ala319-Met335). This domain of APP can stimulate neurite extension of cultured neuroblastoma cells and it is proposed that APP mediates this effect through binding to a cell surface receptor, triggering intracellular transduction mechanisms. Thus, the secreted form of APP can function as a growth and/or differentiation factor and the site involved in these activities is within a 17-mer domain in the middle of the molecule. Our current lines of research seek to further characterize the mechanisms of APP function as well as its activity in vivo.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1749-6632.1993.tb23044.x
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  • 6
    Electronic Resource
    Electronic Resource
    NPC1 gene mutations in Japanese patients with Niemann-Pick disease type C (1999)
    Springer
    Human genetics 〈Berlin〉 105 (1999), S. 10-16 
    Details
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Complementary and genomic DNAs isolated from the fibroblasts of 10 Japanese (7 late infantile, 2 juvenile, and 1 adult form of the disease) and one Caucasian patient with Niemann-Pick disease type C were analyzed for mutations in the NPC1 gene. Fourteen novel mutations were found including small deletions and point mutations. A one-base deletion and a point mutation caused splicing errors. The mutations were not clustered in any particular region of the gene and were found both in and out of the transmembrane domains. Three patients were homozygous, five were compound heterozygous, and the remaining three were suspected of being compound hetrozygous with an unknown error in one of their NPC1 alleles. Of the 14 mutations, the G1553A substitution that caused a splicing error of exon 9 appeared to be relatively common in Japanese patients, because two patients were homozygous and one patient was compound heterozygous for this mutation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004399900059
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  • 7
    Electronic Resource
    Electronic Resource
    Structural basis of the function of endothelin receptor (1999)
    Springer
    Molecular and cellular biochemistry 190 (1999), S. 153-156 
    Details
    ISSN: 1573-4919
    Keywords: G-protein ; vasoconstriction ; ligand selectivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Endothelin receptor is a good model for analysis of the function of heptahelical G-protein coupled receptor. In ligand binding to the heptahelical receptor, the receptor has two functions, i.e. ‘message’ and ‘address’ functions. Each function has been assigned to different domain of the receptor. A different part of the ligand structure also corresponds to each domain of the receptor. Classically, classification of receptor has been done according to the difference of address domain, i.e. affinity difference of the receptor. However, present results predict that the classification of receptor is also possible according to the message domain. After stimulation of ET receptor by a ligand, the receptor transmits a signal to G-protein. Several kinds of G-proteins can possibly be activated. Different structural domains of the receptor are assigned to the coupling of the different Gα-protein. Activated G-protein transmits the message to effector. Each Gα-protein acts on different target molecules, resulting in different responses. However, the activation of each Gα-protein presumably depends on its intracellular level. Even if the same receptor is activated with the same ligand, resulting final response is different from cell to cell. Therefore, classification of receptor according to the function of the receptor is difficult.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006986914326
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