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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 140 (1984), S. 215-217 
    ISSN: 1432-072X
    Keywords: Glutathione reductase ; Cyanobacteria ; Nostoc muscorum ; O2 protection ; Glutathione ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Glutathione reductase activity was detected and characterized in heterocysts and vegetative cells of the cyanobacterium Nostoc muscorum. The activity of the enzyme varied between 50 and 150 nmol reduced glutathione· min-1·mg protein-1, and the apparent Km for NADPH was 0.125 and 0.200 mM for heterocysts and vegetative cells, respectively. The enzyme was found to be sensitive to Zn+2 ions, however, preincubation with oxidized glutathione rendered its resistance to Zn+2 inhibition. Nostoc muscorum filaments were found to contain 0.6–0.7mM glutathione, and it is suggested that glutathione reductase can regenerate reduced glutathione in both cell types. The combined activity of glutathione reductase and isocitrate dehydrogenase in heterocysts was as high as 18 nmol reduced glutathione·min-1·mg protein-1. A relatively high superoxide dismutase activity was found in the two cell types; 34.2 and 64.3 enzyme units·min-1·mg protein-1 in heterocysts and vegetative cells, respectively. We suggest that glutathione reductase plays a role in the protection mechanism which removes oxygen radicals in the N2-fixing cyanobacterium Nostoc muscorum.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Journal of neurochemistry 80 (2002), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: GABARAP (GABAA receptor-associated protein) interacts with both microtubules and GABAA receptors in vitro and in␣vivo and is capable of modulating receptor channel kinetics. In this study, we use the intracellular loop of 15 GABAA receptor subunits to show that the interaction between GABARAP and GABAA receptor is specific for the gamma subunits. Pharmacological characterization of proteins purified by GABARAP affinity column indicates that native GABAA receptors interact with GABARAP. Quantitative yeast two-hybrid assays were used to identify the interaction domain in the γ2 subunit for GABARAP binding, and to identify the interaction domain in GABARAP for GABAA receptor binding. A peptide corresponding to the GABARAP interaction domain in the γ2 subunit was used to inhibit the interaction between GABARAP and the γ2 subunit. In addition, the ability of GABARAP to promote cluster formation of recombinant receptors expressed in QT-6 fibroblasts was inhibited by a membrane-permeable form of this peptide in a time-dependent manner. The establishment of a model for GABARAP-induced clustering of GABAA receptors in living cells and the identification of subunit specificity and interaction domains in the interaction between GABARAP and GABAA receptors is a step in dissecting the function of GABARAP in GABAA receptor clustering and/or targeting.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: γ-Aminobutyric acid (GABAa) receptor β3 subunits were expressed in Xenopus laevis oocytes and studied using two-electrode voltage clamp. Injected oocytes exhibited an increased resting membrane conductance and more depolarized membrane potentials compared to uninjected control cells. Oocytes expressing β3 subunits were insensitive to GABA and muscimol, but pentobarbitone increased the membrane conductance in a concentration-dependent manner. The membrane current response to pentobarbitone reversed at the Cl−equilibrium potential and at relatively high concentrations (〉500 μM), a rebound CI− current was induced following the removal of pentobarbitone. In transfected human embryonic kidney (HEK) cells, the rebound current amplitude was reduced by desensitizing the β3 receptor with increased durations of ligand application. Both picrotoxin (0.5 nM to 10 μM) and Zn2+ (10 nM to 100 μM) reduced the resting membrane conductance for β3 cDNA-injected oocytes. These oocytes were insensitive to flurazepam (5 μM) and alphaxalone (10 μM), but responded with increased membrane conductance to propofol (10 μM) and pregnanolone (50 nM to 5 μM). The antagonists, bicuculline (10 μM) and strychnine (50 nM to 100 μM), also induced conductance increases in a concentration dependent manner; however, glycine (1 mM) was inactive. It was concluded that β3 subunits form spontaneously opening ion channels that can be up-regulated by some allosteric modulators, principally by pentobarbitone and propofol and, surprisingly, by bicuculline and strychnine, whilst picrotoxin and Zn2+ acted as antagonists. Computer modelling of some kinetic schemes was used to describe the rebound current observed in transfected HEK cells. This indicated that pentobarbitone, after modulation of the conductance, is potentially capable of further binding to the β3 receptor complex ‘driving’ the receptor into one or more desensitized states. This phenomenon may be of some importance for native neuronal GABAA receptors, where pentobarbitone can also evoke rebound current activation.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 397 (1999), S. 66-69 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The ionotropic type-A and type-C receptors for the neurotransmitter γ-aminobutyric acid (GABAA and GABAC receptors) are the principal sites of fast synaptic inhibition in the central nervous system, but it is not known how these receptors are localized at ...
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 377 (1995), S. 344-348 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Tyrosine phosphorylation of GABAA receptors was analysed in human embryonic kidney cells5 7 (A293; CRL 1573) expressing GABAA-receptor al, |31 and y2L subunits. Receptors composed of these subunits can reproduce many of the properties of neuronal GABAA receptors1 3'5 7. Tagging of the y2L subunit ...
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    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
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1752-7325
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Following ingestion of dietary fluoride, microquantities of fluoride return to the mouth in saliva, but in quantities large enough to facilitate the maintenance and reparative functions of enamel. Dietary fluoride supplements alone are unlikely to be the cause of the reported increase in fluorosis. Compliance continues to be extremely poor and few children use supplements for more than a year and a half. The amount of background fluoride resulting from dietary fluoride supplements appears to be very small. Considering the almost ubiquitous presence of fluoride dentifrice and the strong possibility of additional unintentional fluoride ingestion from many sources, the present fluorosis data is too amorphous to use as a basis for making reasonable risk/benefit evaluations. Very mild and mild fluorosis is not a serious problem for either the clinician or the patient. By altering the present recommended dosage we may deprive children from receiving a proven effective dose. One cannot make a risk/benefit decision concerning an esthetic problem without involving the patient's perception as well as the caries score. The apparent severity of the milder forms of fluorosis lessens with age and a community fluorosis index should be used only on populations who are older than 15 years.
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1708-8240
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Macmillan Magazines Ltd.
    Nature 397 (1999), S. 69-72 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Type-A receptors for the neurotransmitter GABA (γ-aminobutyric acid) are ligand-gated chloride channels that mediate inhibitory neurotransmission. Each subunit of the pentameric receptor protein has ligand-binding sites in the amino-terminal extracellular domain and four membrane-spanning ...
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 58 (1992), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The structure and distribution of non-N-methyl-D-aspartate glutamate receptors in the rat brain were studied using subunit-specific antibodies that recognize the receptor subunit GluRl. The GluRl protein, a 106-kDa glycoprotein, appears predominantly in synaptic plasma membranes, where it is highly enriched in the postsynaptic densities. When synaptic plasma membranes are solubilized with the detergent 3-[(3-cholamidopropyl)dimethylammonio]-l-propanesul-fonate, high-affinity a-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) binding and GluRl immunoreactivity comigrate at a native Mr of 610,000. GluRl is enriched in the hippocampus and cerebellar cortex but is present throughout the CNS. It is found on neuronal cell bodies and processes within most regions of the brain; within the cerebellum, however, it is localized to the Bergmann glia. These data suggest that the GluRl protein is a subunit of multimeric AMPA-preferring glutamate receptors present on neurons and on specialized glia.
    Type of Medium: Electronic Resource
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