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  • 1
    Electronic Resource
    Electronic Resource
    Phospholipase A2 Stimulation by Methyl Mercury in Neuron Culture (1994)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 62 (1994), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: In primary prelabeled cultures of cerebellar granule cells, methyl mercury (MeHg) induced a concentration- and time-dependent release of [3H]arachidonic acid. MeHg-induced [3H]arachidonate release was partially dependent on the extracellular Ca2+ concentration. MeHg at 10–20 µM also stimulated basal 45Ca2+ uptake after 20 min of incubation at 37°C, and at 10 µM inhibited K+ depolarization-stimulated uptake. MeHg stimulated [3H]arachidonate uptake, but had no effect on the rate of phospholipid reacylation. Phospholipase A2 (PLA2) activation preceded cytotoxicity, but at higher concentrations of MeHg such dissociation was not evident. Inhibition of MeHg-induced PLA2 activation by 100 µM mepacrine failed to modify cytotoxicity. MeHg-induced lipoperoxidation, measured as the production of thiobarbituric acid-reacting products, was inhibited by α-tocopherol without inhibition of [3H]arachidonate release. The absence of α-tocopherol inhibition of MeHg-induced arachidonate release precludes a causal role for lipoperoxide-induced PLA2 activation in this system. Moreover, MeHg induced an increased susceptibility of unilamellar vesicles to exogenous PLA2 in the presence of low Ca2+ concentrations without evidence of lipid peroxidation. [3H]Arachidonate incorporation into granule neuron phospholipids was analyzed by isocratic HPLC analysis. Relatively high proportional incorporation was found in the combined phosphatidylcholine fractions and phosphatidylinositol. With MeHg, an increase in the relative specific activity of incorporation was found in the phosphatidylinositol fraction, indicating a preferential turnover in this phospholipid species in the presence of MeHg.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1994.62020705.x
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  • 2
    Electronic Resource
    Electronic Resource
    THYROID HORMONE INHIBITION OF SYNAPTOSOME AMINO ACID UPTAKE AND PROTEIN SYNTHESIS (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— 3,3′,5-Triiodothyronine (T3) inhibited L-[14C]leucine uptake into synaptosomes. Inhibition was competitive with a Ki of 3.1 × 10−5m. Hofstee plot revealed an inverted hyperbolic curve suggestive of a two carrier or carrier plus diffusion mediated system for amino acid uptake. Both the carrier mediated and diffusional components were inhibited by thyroid analogues. l-Thyroxine and analogues inhibited the incorporation of l-[14C] leucine into cerebral synaptosome protein. At 50 μm, the triiodo-compounds were more inhibitory than tetraiodo-〉3,5-triiodo-l-thyronine 〉3,3′,5-triiodothyropro-pionic〉 l-thyroxine 〉3,5-diiodo-l-tyrosine. Thyroid analogue inhibition was not seen in liver or brain mitochondrial protein synthesis. 3,3′,5-Triiodothyronine had no effect on respiratory control or 2,4-DNP stimulated synaptosome respiration supported by malate plus pyruvate. Ouabain did not inhibit [14C]leucine uptake into adult synaptosomes. There was synergistic inhibition of synaptosome protein synthesis by thyroid analogues in the presence of 0.2 mm-ouabain. 3,3′,5-Triiodothyronine had no effect on synaptosome fraction ATPase or Na-K ATPase. Addition of T3 induced further inhibition of synaptosome protein synthesis in the presence of either chloramphenicol (100μm) or cycloheximide (50μg/ml). [14C]Glycine uptake and incorporation into synaptosome protein was inhibited by 3,3′,5-triiodothyronine. There was no inhibition of [14C]proline uptake or incorporation.The above evidence and kinetic data strongly favor a selective competitive block in amino acid transport at the synaptosome membrane leading to a decreased rate of protein synthesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1977.tb10728.x
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  • 3
    Electronic Resource
    Electronic Resource
    METHYL MERCURY INHIBITION OF SYNAPTOSOME AND BRAIN SLICE PROTEIN SYNTHESIS: IN VIVO AND IN VITRO STUDIES (1977)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Subacute methyl mercury (MeHg) intoxication was induced in adult rats following the daily intragastric administration of 1 mg MeHg/100 g body weight. Decreased [14C]leucine incorporation into cerebral and cerebellar slice protein was found. Weight loss occurred during the latent and neurotoxic phases but pair feeding did not reveal a significant defect in amino acid incorporation into slice protein. There was no decline in synaptosome protein synthesis in vitro during the latent phase but a significant decline in cerebellar and cerebral synaptosome synthesis was found during the neurotoxic phase. MeHg in vitro inhibited cerebral slice and synaptosome protein synthesis at half maximal concentrations of 7.5 and 12.5 μM respectively. Inhibition of synthesis in synaptosomes was non-competitive with K1 of 4 × 10−6M. MeHg had no effect on [14C]leucine or [14C]proline uptake into synaptosomes. There was no significant inhibition of synaptosome basal ATPase or Na + K ATPase at concentrations of MeHg (12 μM) giving half maximal inhibition of protein synthesis. No preferential inhibition of the chloramphenicol (55S) or cycloheximide sensitive components of synaptosome fraction protein synthesis was found, suggesting that the inhibition is common to both mitochondrial and extramitochondrial protein synthesizing systems. Addition of nucleotides and/or atractylate failed to influence protein synthesis and did not reverse the MeHg inhibition. Mannitol, as a replacement for the predominant cation species of the incubation medium, gave 40% inhibition of protein synthesis in the control but protected against further inhibition by MeHg.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1977.tb07785.x
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  • 4
    Electronic Resource
    Electronic Resource
    CATION MODULATION OF SYNAPTOSOMAL RESPIRATION (1972)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 19 (1972), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Synaptosomes were prepared from the cerebral cortex of the adult rat by a rapid technique, involving the use of centrifugation in a Ficoll-sucrose discontinuous gradient. Adequate respiratory control ratios were obtained with glutamate and succinate plus rotenone. The addition of Na+ to the incubation medium stimulated synaptosomal, State-4 respiration, with a half-maximal response at 15 mM Na+. The stimulation by Na+ was inhibited by atractylate, oligomycin, ouabain or EDTA. A cooperative interaction between Na+ and low concentrations of Mg2+ was observed. A significant proportion (39 per cent) of the total Na-K ATPase (EC 3.6.1.4) activity in the discontinuous gradient was localized in the synaptosomal fraction. In the absence of exogenous Mg2+, Na+ induced a 64 per cent stimulation of the synaptosomal ATPase activity which was sensitive to ouabain. Such stimulation of ATP hydrolysis would account for the formation of increased amounts of ADP, with consequent recycling to ATP through adequately controlled oxidative phosphorylation. These observations demonstrate a significant role for transmembrane cationic gradients in the control of synaptosomal respiration and mitochondrial oxidative phosphorylation. The preparation exhibits moderate respiratory control and should prove useful in studies of integrated mitochondrial oxidative metabolism and neuronal membrane function.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1972.tb01456.x
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  • 5
    Electronic Resource
    Electronic Resource
    STRUCTURE-LINKED ACTIVITY OF LYSOSOMAL ENZYMES IN THE DEVELOPING MOUSE BRAIN (1968)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 15 (1968), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —A longitudinal study of the maturation of mouse cerebral lysosomal enzymes has been completed. Activity of the enzymes, acid phosphatase (I.U.B. 3.1.3.2), β-glucuronidase (I.U.B. 3.2.1.31) and β-acetylglucosaminidase (I.U.B. 3.2.1.30) was assayed spectrofluorimetrically on portions of supernatant from 0.25 M sucrose homogenates spun at 6 x 103 -min. Activities were obtained in native (free) and Triton X-100 activated samples (total).The neonatal period was characterized by relatively low free and high total acid phosphatase activities. An abrupt rise in free activity occurred during the period 10–20 days. Discontinuous anion exchange DEAE cellulose chromatography (0.01 m-tris–maleate, pH 6.3) with elution by ascending molarities of NaCl of the Triton X-100 activated supernatant revealed three major peaks in the adult. A fourth peak, designated as fraction II (‘maturation fraction’) occurred only during the neonatal period, a time also characterized by increased specific activity of fraction I, with no change in fraction IV. The chromatographic fractions were further characterized by optimal pH, ascorbate, fluoride, Cu2+ and Fe2+ ions.The maturation profiles of total, β-glucuronidase and total, β-acetylglucosaminidase differed from each other, and from that of total acid phosphatase. Comparable differences existed in the profiles of the free activities, and the ratio of free:total activity differed for each enzyme at any selected time especially during the neonatal period. These findings are are discussed with reference to the maturation of isoenzyme fractions with age, and suggest that the changes in structure-linked organization of individual lysosomal hydrolases are functions of heterogeneity in enzyme complement of individual lysosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1968.tb06176.x
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  • 6
    Electronic Resource
    Electronic Resource
    ORGANIC MERCURIAL ENCEPHALOPATHY: IN VIVO AND IN VITRO EFFECTS OF METHYL MERCURY ON SYNAPTOSOMAL RESPIRATION (1975)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 25 (1975), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —A reproducible model of subacute methyl mercury (MeHg) intoxication was developed in the adult rat following the daily intragastric administration of 10 mg methyl mercury/kg body wt. Synaptosomes isolated from animals during the latent phase of mercury neurotoxicity (6-10 days) demonstrated no significant change in respiratory control, State 3, State 4, or 2,4-dinitrophenol stimulated respiration with succinate, glutamate or pyruvate plus malate. During the neurotoxic phase, a significant decline in respiratory control was evident with all substrates. Cerebellar synaptosomes revealed qualitatively similar but quantitatively greater inhibition of 2,4-dinitrophenol stimulated respiration during the latent and neurotoxic phases with glutamate. In vitro studies of synaptosome respiration, oxidative phosphorylation and respiratory control with 5-15 μm-methyl mercury revealed a stimulation of initial State 4 respiration, loss of RCI, inhibition of State 3 but no change in the gramicidin or 2,4-dinitrophenol uncoupled rate supported by pyruvate-malate. Phosphate did not relieve the State 3 inhibition. At 25 μm-methyl mercury and above, considerable inhibition of electron transfer occurred. At this concentration, cytochrome c oxidase was inhibited 50%. Isosmotic replacement of medium KC1 by mannitol reduced the MeHg stimulation of State 4 respiration but had no effect on MeHg inhibition of ADP stimulated respiration. Half-maximal stimulation of State 4 respiration by MeHg occurred at [K]+⋍ 6 mm. These findings are compatible with an energy-linked methyl mercury induced cation translocation across the synaptosome (mitochondrial) membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1975.tb04405.x
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  • 7
    Electronic Resource
    Electronic Resource
    CHARACTERIZATION AND LOCALIZATION OF ACID HYDROLASE ACTIVITY IN THE SYNAPTOSOMAL FRACTION FROM RAT CEREBRAL CORTEX (1973)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 20 (1973), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Synaptosomes were prepared from the cerebral cortex of adult rats by a rapid technique of centrifugation in a Ficoll-sucrose discontinuous gradient. The synaptosomal fraction contained 40 per cent of the total gradient activity of acid α-naphthyl phosphatase (EC 3.1.3.2). Quantitative electron microscopy of this fraction revealed rare, typical, extrasynaptosomal dense body lysosomes. pH-activity profiles of free and Triton X-100 (total) activities were prepared for α-naphthyl phosphatase, β-glucuronidase (EC 3.2.1.31), β-galactosidase (EC 3.2.1.23), arylsulfatase (EC 3.1.6.1) and N-acetylglucosaminidase (EC 3.2.1.30). The ratios of total to free activity varied in the order: arylsulfatase 〉 β-galactosidase 〉 β-glucuronidase 〉 N-acetylglucosaminidase 〉 acid phosphohydrolase. Incubation of synaptosomal fractions at pH 5 and 37°C produced significant activation of β-galactosidase and N-acetylglucosaminidase but no activation of cryptic lactate dehydrogenase (EC 1.1.1.27). Hyposmotic suspension and subfractionation of the synaptosomal fraction produced considerable solubilization of lactate dehydrogenase, arylsulfatase and β-galactosidase but only partial liberation of α-naphthyl phosphatase, the remainder being associated with synaptosomal membrane fragments. Incomplete equilibrium sedimentation of synaptosomes in a continuous sucrose gradient (0·55-1·5 M) provided a broad lactate dehydrogenase and Na + K ATPase (EC 3.6.1.4) peak (peak I) at low sucrose densities. β-Glucuronidase, β-glucosidase and α-naphthyl phosphatase were significantly present in peak I. Conversely, N-acetylglucosaminidase, arylsulphatase and β-galactosidase were predominantly located in denser particles sedimenting through 1·2 M sucrose (peak II). Electron microscopy confirmed the heterogeneity of this second peak and the presence of numerous extrasynapto-somal dense body lysosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1471-4159.1973.tb00280.x
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  • 8
    Electronic Resource
    Electronic Resource
    Fatal hemorrhage in a cerebral pilocytic astrocytoma-adult type (1991)
    Springer
    Acta neuropathologica 81 (1991), S. 688-690 
    Details
    ISSN: 1432-0533
    Keywords: Pilocytic astrocytoma-adult type ; Cerebral neoplasm ; Hemorrhage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A 69-year-old female presented with a 6-week history of left-sided weakness and a large cerebral mass on computed tomographic scan and magnetic resonance imaging. The patient subsequently had an acute intracerebral hemorrhage with uncal and tonsillar herniation. Postmortem examination revealed an acute cerebral hemorrhage from a pilocytic astrocytoma-adult type. These cerebral neoplasms are rarely associated with hemorrhage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296382
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