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  • 1
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Cavernous angiomas are vascular malformations that cause neurodegeneration and symptoms including epileptiform seizures, headache, and motor deficits. Following neurosurgical removal of the angiomas, patients mostly recover well and become seizure-free. This study reports on the levels of certain amino acids in angiomas, obtained from 13 patients. Distinct zones of the angiomas were analyzed, from the thrombotic core, via gliotic, hemosiderin-infiltrated intermediate zones, to a periphery without macroscopic abnormalities. The neurotransmitter amino acids glutamate, aspartate, and GABA as well as phosphoethanolamine displayed decreasing levels from the periphery to the core, reflecting the gradual neuronal loss. Compared with normal brain tissue, there was a marked increase in the levels of serine (fivefold), glycine (10-fold), and ethanolamine (20-fold) in the peripheral zone of the cavernous angiomas. The results are discussed in relation to seizures and NMDA receptor activation, neuron-glia interactions, membrane phospholipids, and blood-brain barrier function.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: In cerebellar slices, the lowering of oxygen availability, obtained by bubbling N2 in the medium, reduced the incorporation of radioactive serine into phosphatidylserine (PtdSer). CPCCOEt, an antagonist of metabotropic glutamate receptors type 1 (mGluR1) counteracted the effect, whereas antagonists of NMDA or AMPA receptors were ineffective. In oxygenated slices, agonists of Group I mGluRs, which include mGluR1, inhibited PtdSer synthesis. This effect was also counteracted by CPCCOEt. These findings indicate that glutamate inhibits PtdSer synthesis by acting on mGluR1. This could be important in relation to the known release of glutamate in hypoxia–ischaemia conditions. In cerebellar Purkinje cells, mGluR1 are involved in the generation of mGluR-EPSP evoked by parallel fibre stimulation. The administration of l-serine to cerebellar slices reduced in a dose-dependent manner the mGluR-EPSP evoked by parallel fibre stimulation. The effect was mostly due to the increased synthesis of PtdSer. Thus inhibition of PtdSer synthesis, mediated by mGluR1, may participate in the generation of mGluR-EPSP.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The report concerns mechanisms for the increase of extracellular levels of ethanolamine and phosphoethanolamine in CNS regions, such as the hippocampus, in transient brain ischemia, hypoglycemia, seizures, etc. l-Serine (2.5–10 mM), d-serine (10 mM), or ethanolamine (10 mM) was administered for 20 min via a microdialysis tubing to the hippocampus of unanesthetized rabbits. The concentrations of primary amines were determined in the dialysates. When levels were elevated 10–100 times in the extracellular fluid, l-serine caused a dose-dependent increase of the concentration of extracellular ethanolamine. Ethanolamine caused a corresponding, although somewhat smaller, increase in serine levels. Furthermore, l-serine also induced an increased concentration of phosphoethanolamine that was delayed in time relative to the peak of ethanolamine. d-Serine was as effective as l-serine in raising ethanolamine levels but had no effect on phosphoethanolamine. Ethanolamine, but not l-serine, also increased extracellular glutamate/aspartate levels in an MK-801-dependent fashion. A similar effect, but delayed in time, was observed with d-serine. These effects were inhibited by MK-801. The concentrations of other amino acids were not significantly affected. The characteristics of the effects are suggestive of base exchange reactions between serine and ethanolamine and between ethanolamine and serine glycerophospholipids, respectively, in neuronal plasma membranes.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0533
    Keywords: Canine distemper virus ; Demyelination ; Plasmalogenase ; Phospholipase ; Arachidonic acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Three weeks after inoculation of 24-day-old gnotobiotic dogs with Snyder-Hill canine distemper virus, white matter samples were taken from the primary predilection sites for canine distemper virus-associated demyelination. The plasmalogenase activity in extracts was nearly 6-fold greater than control values for a dog with extensive demyelination and was not detectable in tissue from a dog with non-demyelinating lesions. Acid and neutral phospholipases A1 and A2 were assayed in homogenates and extracts with phosphatidyl ethanolamine substrates. Phospholipase A2 activities at both pH 4.3 and pH 6.8 were less in the dog with severe demyelinating lesions than in dogs with less severe lesions. Phospholipase A1 activities were generally similar for all four dogs. The marked elevation of plasmalogenase activity in demyelinating tissue may be associated with a release from the plasmalogens of arachidonic acid which is converted to oxygenated metabolites that may then be responsible for the inflammation. Phospholipases acting on phosphatidyl ethanolamine do not seem to be involved in the pathogenesis of demyelination associated with canine distemper virus.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-4919
    Keywords: phosphatidylserine ; base exchange ; apoptosis ; thymocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The exposure of phosphatidylserine toward the external surface of the membrane is a well-established event of programmed cell death. The possibility that an apoptotic stimulus influences the metabolism of this phospholipid could be relevant not only in relation to the previously mentioned event but also in relation to the capability of membrane phosphatidylserine to influence PKC activity. The present investigation demonstrates that treatment of mouse thymocytes with the apoptotic stimulus dexamethasone, enhances the incorporation of [3H]serine into phosphatidylserine. Cell treatment with dexamethasone also enhanced the activity of serine base exchange enzyme, assayed in thymocyte lysate. Both the effects were observed at periods of treatment preceding DNA fragmentation. The addition of unlabelled ethanolamine, together with [3H]serine to the medium containing dexamethasone-treated thymocytes lowered the radioactivity into phosphatidylserine. Serine base exchange enzyme activity was influenced by the procedure used to prepare thymocyte lysate and was lowered by the addition of fluoroaluminate, that is widely used as a G-protein activator. The increase of serine base exchange enzyme activity induced by dexamethasone treatment was observed independently by the procedure used to prepare cell lysate and by the presence or absence of fluoroaluminate.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-4919
    Keywords: serine base exchange ; phosphatidylserine ; platelets ; heparin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Phosphatidylserine is one of the PKC modulators and thus it may play an important role in signal transduction. Regulation of the synthesis of this phospholipid is not yet clarified. The contrasting reports are possibly related to the existence of different enzymes which, in mammalian tissues, catalyse the exchange between free serine and the nitrogen base of a membrane phospholipid. This study demonstrates that serine base exchange reactions of commercially available lyophilised porcine platelets exhibit similar pH optima, temperature and Ca2+ dependence as observed in fresh tissues. Analysis of fatty acids composition of the three phospholipid classes involved in base exchange reactions also demonstrated a similarity with fresh platelets. Serine and ethanolamine base exchange enzyme activities were assayed in parallel in platelet lysate subjected to preincubation at various temperatures (30-60°C). When dithioerithrol was omitted from the incubation medium, the two base exchange reactions were inhibited with a similar temperature-dependent pattern. Addition of the reducing agent enhanced the sensitivity to preincubation only for the serine base exchange reaction which was inhibited by 80% after preincubation at 45°C. With respect to its regulation, porcine platelet serine base exchange enzyme(s) was inhibited by fluoroalluminate, a widely used G-protein activator, and stimulated by unfractionated heparin. Low mol. wt. heparin did not influence enzyme activity. Unfractionated heparin greatly stimulated SBEE activity assayed at pH 7.4, a pH value far from the optimal pH.
    Type of Medium: Electronic Resource
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