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  • 1
    Electronic Resource
    Electronic Resource
    Activation of (Na+, K+)-ATPase by Nanomolar Concentrations of GM1 Ganglioside (1981)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 37 (1981), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: GM1 ganglioside binding to the crude mitochondrial fraction of rat brain and its effect on (Na+, K+)-ATPase were studied, the following results being obtained: (a) the binding process followed a biphasic kinetics with a break at 50 nM-GM1; GM1 at concentrations below the break was stably associated, while over the break it was loosely associated; (b) stably bound GM1 activated (Na+, K+)-ATPase up to a maximum of 43%; (c) the activation was dependent upon the amount of bound GM1 and was highest at the critical concentration of 20 pmol bound GM1× mg protein-1; (d) loosely bound GM1 suppressed the activating effect on (Na+, K+)-ATPase elicited by firmly bound GM1; (e) GM1-activated (Na+, K+)-ATPase had the same pH optimum and apparent Km (for ATP) as normal (Na+, K+)-ATPase but a greater apparent Vmax; (f) under identical binding conditions (2 h, 37°C, with 40 nM substance) all tested gangliosides (GM1, GD1a, GD1b, GT1b) activated (Na+, K+)-ATPase (from 26–43%); NeuNAc, sodium dodecylsulphate, sulphatide and cerebroside had only a very slight effect. It is suggested that the ganglioside activation of (Na+ -K+)-ATPase is a specific phenomenon not related to the amphiphilic and ionic properties of gangliosides, but due to modifications of the membrane lipid environment surrounding the enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1981.tb00462.x
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  • 2
    Electronic Resource
    Electronic Resource
    Promotion of Neuritogenesis in Mouse Neuroblastoma Cells by Exogenous Gangliosides. Relationship Between the Effect and the Cell Association of Ganglioside GM1 (1984)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 42 (1984), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Ganglioside GM1 promoted neuritogenesis of neuroblastoma cells, neuro-2a clone, in monolayer culture. GM1 bound to neuro-2a cells in three distinct forms, one removable by treatment with serum-containing solutions, one serum-resistant and labile to trypsin treatment, and one resistant to serum and trypsin treatments. The proportions among the three forms of cell-associated GM1 varied in relation to duration of exposure to ganglioside, ganglioside concentration in the medium, and number of cells in culture. The form removable by serum was predominant at the initial stages of association and at the highest ganglioside concentrations (over 10−6M); the trypsin-labile and -stable forms tended to increase with increasing cell number and decreasing ganglioside concentration. The neuritogenic effect of GM1 was higher when neuro-2a cells were incubated for 24 h in the presence of GM1 and fetal calf serum. Under this condition the percentage of neurite-bearing cells increased from 11% of control to 62% at the optimal ganglioside concentration of 10−4M. The effect was still present, although to a lower extent (from 11% to 28% of neurite-bearing cells), when cells were first exposed for only 2 h to GM1, then washed and incubated for 24 h in the presence of fetal calf serum. The trypsin-labile and -stable forms of cell-associated GM1 had a fundamental role in the effect, whereas the form removable by serum was not involved. The preparation of GM1 used was extremely pure (99%) and, in particular, had a peptide contamination, if any, 〈1:20,000–1:50,000. Therefore the neuritogenic effect can be attributed to ganglioside itself. The results obtained suggest that under the experimental conditions used the stimulation of neuro-2a cell differentiation by GM1 is related to changes of the plasma membrane properties following association of exogenous GM1 molecules. This would facilitate the spontaneous process of differentiation, or enhance cell responsiveness to differentiating factors present in the serum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1984.tb02678.x
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  • 3
    Electronic Resource
    Electronic Resource
    Melanin Biosynthesis From Dopamine. II. A Mass Spectrometric and Collisional Spectroscopic Investigation (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Periodontology 2000 5 (1992), S. 0 
    Details
    ISSN: 1600-0757
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Electron impact (EI) and fast atom bombardment (FAB) mass spectrometry together with collisional activation (CA) experiments were applied to the study of the oxidation pathway of dopamine by tyrosinase. In order to prevent attachment of the protein to the highly reactive intermediates, ultrafiltration was employed to remove the enzyme at different reaction times. FAB, privileging molecular species formation, was successfully used for identification of transient intermediates and their relative concentrations with respect to time, directly in the reaction mixture. The presence of isobaric molecular species made chromatographic separation necessary. Further EI mass spectrometry and collision spectroscopy led to structural identification of pure components. Of these, dopamine-o-quinone, leucoaminochrome, and aminochrome semiquinone were characterized for the first time as real intermediates in dopamine melanogenesis, in agreement with previous hypotheses.This approach elucidated the pathway of dopamine melanogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1600-0749.1992.tb00008.x
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  • 4
    Electronic Resource
    Electronic Resource
    Regulatory aspects of nigrostriatal dopaminergic neurons (1992)
    Springer
    Experimental brain research 91 (1992), S. 489-495 
    Details
    ISSN: 1432-1106
    Keywords: Regulation ; Synthesis ; Release ; Dopamine ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the urethane-anesthetized rat, electrical stimulation (10 Hz, 30 s, 250 μA) of the medial forebrain bundle (MFB), at 20-min intervals over an 8-h period, combined with intracerebral microdialysis in the striatum caused: an undiminished increase in the release of dopamine (DA) with each stimulation episode; a decreased efflux of 3,4-dihydroxyphenylacetic acid (DO-PAC) and 4-hydroxy-3-methoxyphenylacetic acid (HVA) after the first stimulation only; a delayed increased efflux of DOPAC with no change in HVA; and a poststimulation depression of firing of dopaminergic neurons in the substantia nigra (before, 3.1±0.7 Hz; after, 1.9±1.0 Hz; P〈0.05). After the last stimulation episode, the release of DA declined to prestimulation values, while the increased efflux of DOPAC persisted for three more hours. After the infusion of tetrodotoxin (4.0×10-7 M, 1.5 μl, 1.0 μl/min) into the MFB, the basal release of DA was reduced (P〈0.05), while the efflux of DOPAC and HVA was increased (P〈0.05). A model is proposed suggesting that: (1) during increased release of DA in the striatum, the metabolism of DA is decreased; (2) inhibition of nigrostriatal dopaminergic neurons is the usual cause of increased synthesis and metabolism of DA in the striatum; and (3) increased release of DA, and increased synthesis and metabolism of DA in the striatum are not causally linked and are noncoupled processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227845
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  • 5
    Electronic Resource
    Electronic Resource
    Incorporation of exogenous ganglioside GM1 into neuroblastoma membranes: Inhibition by calcium ion and dependence upon membrane protein (1989)
    Springer
    Neurochemical research 14 (1989), S. 547-554 
    Details
    ISSN: 1573-6903
    Keywords: Exogenous gangliosides ; ganglioside binding ; GM1 ; neuroblastoma ; calcium ion ; differentiation ; neuritogenesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Since exogenous gangliosides are known to promote neuritogenesis, the incorporation of exogenous GM1 into neuroblastoma membranes was examined. Neuro-2A cells, synchronized in the G1/G0 phase, were suspended in HEPES buffered saline containing 10−4 M [3H]GM1, and membrane incorporation was measured as radioactivity remaining with the cell pellet following incubation with serum-containing medium and trypsin. Calcium ion (0.01 to 10 mM) reduced incorporation of exogenous GM1, due to its interaction with GM1 micelles in solution. When cells were treated with proteases prior to incubation with GM1, the inhibitory effect of Ca2+ was lost and total incorporation into membranes was lowered by approximately one order of magnitude. Pretreatment of cells with 0.05% trypsin resulted in an inhibition of GM1 incorporation within 5 minutes. When trypsinized cells were resuspended in complete growth medium, the cells recovered the ability to incorporate GM1 with time, and this paralleled labeling of cellular protein with [3H]leucine. The role of membrane protein in the incorporation of exogenous GM1 could not be explained by the lytic release of cytosolic transfer proteins nor the artifactual coating of the cell surface by serum proteins. These results suggest that the incorporation of exogenous gangliosides into cellular membrane lipid bilayers cannot be fully explained by considerations of lipophilicity alone, and leads us to propose that initial recognition by membrane protein(s) is necessary.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00964917
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  • 6
    Electronic Resource
    Electronic Resource
    Reversal of scopolamine-induced amnesia by phosphatidylserine in rats (1986)
    Springer
    Psychopharmacology 90 (1986), S. 274-275 
    Details
    ISSN: 1432-2072
    Keywords: Amnesia ; Phosphatidylserine ; Scopolamine ; Propranolol ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Scopolamine (2 mg/kg IP) and propranolol (55 mg/kg IP), given before a single learning trial, reduce retention of a passive avoidance response in rats. Phosphatidylserine, 30–60 mg/kg IP, antagonizes the amnesic effect of scopolamine but not that of propranolol. The retention of the passive avoidance response is not affected by phosphatidylserine given alone. The results indicate that this phospholipid selectively counteracts the action of scopolamine on passive avoidance acquisition, probably via a cholinergic mechanism.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00181257
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  • 7
    Electronic Resource
    Electronic Resource
    Synergistic effect of phosphatidylserine with γ-aminobutyric acid in antagonizing the isoniazid-induced convulsions in mice (1984)
    Springer
    Neurochemical research 9 (1984), S. 1065-1073 
    Details
    ISSN: 1573-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The influence of phosphatidylserine (PS) on the isoniazid-induced convulsions has been studied in mice. Sonicated dispersions of this phospholipid given intravenously do not show anticonvulsant activity but they do so when γ-aminobutyric acid (GABA) is simultaneously injected. GABA alone is inactive. The synergism between PS and GABA is influenced by the structure of the phospholipid liposomes. In contrast to multilamellar vesicles, oligolamellar vesicles are active. Under these conditions the effect shows head group specificity, in that the neutral phosphatidylcholine (PC) or the acidic phosphatidylinositol (PI) are inactive, either in the presence or in the absence of GABA. Lysophosphatidylserine (lysoPS), the deacylated PS derivative, shows increased efficacy as an isoniazid antagonist in the presence of GABA, and has anticonvulsant activity also in the absence of GABA. Other lysophospholipids are inactive. It is suggested that PS, after its metabolic conversion to lysoPS, enhances the anticonvulsant effect of GABA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00964802
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  • 8
    Electronic Resource
    Electronic Resource
    Biochemical changes of rat brain membranes with aging (1983)
    Springer
    Neurochemical research 8 (1983), S. 483-492 
    Details
    ISSN: 1573-6903
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Modification of membrane composition and enzymatic activities both in total brain homogenate and purified synaptic plasma membrane of 3 and 24 month old rats has been investigated. Protein, cholesterol and phospholipid content and (Na+, K+)ATPase and 2′, 3′ cyclic nucleotide phosphohydrolase activities were determined. The major changes occurred in the whole homogenate where a general increase in total protein and cholesterol content with age and a significant increase of the cholesterol/phospholipids molar ratio has been detected. In S.P.M. aging process induced a decrease of protein, cholesterol and phospholipids content associated with an increased membrane viscosity and a decrease of ΔE. These data are consistent with a change in the structural organization and in the distribution pattern of different cell population in the aging brain. A possible artifactual effect of freezing on the reported parameter is also discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00965104
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