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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 56 (1991), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Brain homogenate, cerebral microvessels, and endothelial cells (ECs) were prepared from 15–18-week-old human fetuses and analyzed biochemically for the presence of elements of the cholinergic system [acetylcholinesterase (AChE), choline acetyltransferase (ChAT), and butyrylcholinesterase]. The ECs were cultured, and their purity was checked by light microscopic immunohistochemistry with the application of anti-human factor VIII and glial fibrillary acidic protein. The highest activity of ChAT was found in the brain homogenate and the lowest in the microvessel fraction. No ChAT activity could be detected in the cultured ECs, despite the presence of high AChE activity. It is suggested that human brain ECs may be under the control of acetylcholine released from cholinergic nerve terminals but that the cells do not produce the transmitter itself. In coculture experiments, when ECs were plated on the upper surface of a polycarbonate filter and glial cells were seeded on the lower surface, the electric resistance was measured. During the culture period, the resistance first increased up to 5 days in vitro (297 ± 17 ohm·cm2) but later gradually declined. These results demonstrate that human ECs cocultured with glial cells provide a useful model for study of the function of the blood-brain barrier in vitro.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 51 (1988), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The role of second messengers in the regulation of protein phosphorylation was studied in microvessels isolated from rat cerebral cortex. The phosphoproteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and the kinetics of 32P incorporation into specific protein substrates were evaluated by computer-aided x-ray film densitometry. With the use of this method, Ca2+-calmodulin (CAM)-, Ca2+/phospholipid (PK C)-, cyclic GMP (cGMP)-, and cyclic AMP (cAMP)-dependent protein kinases were detected. CAM-dependent protein ki-nase proved to be the major phosphorylating enzyme in the microvascular fraction of the rat cerebral cortex; the activity of cGMP-dependent protein kinase was much higher than that of the cAMP-dependent one. Autophosphoryla-tion of both the α- and β-subunits of CAM-dependent protein kinase and the proteolytic fragment of the PK C enzyme was also detected. The kinetics of phosphorylation of the individual polypeptides indicate the presence in the cerebral endothelium of phosphoprotein phosphatases. The phosphorylation of proteins in the cerebral capillaries was more or less reversible; the addition of second messengers initiated a very rapid increase in 32P incorporation, followed by a slow decrease. Because the intracellular signal transducers like Ca2+ and cyclic nucleotides are frequently regulated by different vasoactive substances in the endothe-lial cells, the modified phosphorylation evoked by these second messengers may be related in vivo to certain changes in the transport processes of the blood-brain barrier.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 65 (1995), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The protein kinase C (PKC) family is composed of at least four conventional (α, βI, βII, and γ) and several related novel (δ, ε, η, and ζ) isoforms with different distribution and sensitivity to Ca2+ and phorbol esters. The enzyme is known to be present in cerebral endothelial cells. We have investigated the occurrence of seven isoforms (α, β, γ, δ, ε, η, and ζ) by using reverse transcriptase-polymerase chain reaction in rat brain, in a freshly isolated brain microvessel fraction, in primary cultures of rat brain endothelial cells, in an immortalized rat brain endothelial cell line, and in aortic endothelial cell cultures. Brain tissue contained all seven investigated isoforms. A similar expression pattern was seen in freshly purified microvessels, but the PKC-γ isoform could not be detected. Primary cultures of endothelial cells expressed PKC-α, -β, -δ, -η, and -ε isoenzymes, whereas the immortalized cell line expressed PKC-α, -δ, -ε, and -η. The rat aortic endothelium contained only PKC-α and -δ isoforms. The variety of expression patterns of PKC family members in endothelial cells of different type may reflect differences in the functional responsiveness to environmental stimuli. Because PKC has been shown to be involved in the regulation of the blood-brain barrier permeability, the presence of different isoforms may confer a sophisticated intracellular regulatory mechanism to the brain endothelial cells.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 49 (1987), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Changes in the activity of Na+, K+-ATPase and in the water, Na+, and K+ levels in the parietal cortex, hippocampus, and thalamus were investigated in rats 1, 3, 6, and 24 h following systemic kainic acid injection. An increase in Na+, K+-ATPase activity was observed in all three regions 3 h after the treatment, with a subsequent decrease in enzyme activity. The elevation in Na+,K+-ATPase activity was accompanied by an increase in the Na+ content and a decrease in the K+ content. These changes are presumed to occur because of repeated discharges and excessive prolonged depolarization in response to kainic acid. The decreases in Na+,K+-ATPase activity 6 and 24 h following kainic acid treatment coincide with neuropathological damage and edema formation, mainly in the hippocampus and thalamus.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: γ-Aminobutyric acid (GABA) was applied to the superior cervical ganglion (SCG) of CFY rats in vitro and in vivo, with or without implantation of a hypoglossal nerve, to evaluate the effects of these experimental interventions on the acetylcholine (ACh) system, which mainly serves the synaptic transmission of the preganglionic input. Long-lasting GABA microinfusion into the SCG in vivo apparently resulted in a “functional denervation.”This treatment reduced the acetylcholinesterase (AChE; EC 3.1.1.7) activity by 30% (p 〈 0.01) and transiently increased the number of nicotinic acetylcholine receptors, but had no significant effect on the choline acetyltransferase (acetyl-coenzyme A:choline-O-acetyl-transferase; EC 2.3.1.6) activity, the ACh level, or the number of muscarinic acetylcholine receptors. The relative amounts of the different molecular forms of AChE did not change under these conditions. In vivo GABA application to the SCG with a hypoglossal nerve implanted in the presence of intact preganglionic afferent synapses exerted a significant modulatory effect on the AChE activity and its molecular forms. The “hyperin-nervation”of the ganglia led to increases in the AChE activity (to 142.5%, p 〈 0.01) and the 16S molecular form (to 200%, p 〈 0.01). It is concluded that in vivo GABA microinfusion and GABA treatment in the presence of additional cholinergic synapses has a modulatory effect on the elements of the ACh system in the SCG of CFY rats.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: —The aim of the experiments was to determine whether a direct correlation exists between cholinergic transmission and zinc-iodide-osmium (ZIO) positivity of the synaptic vesicles of the preganglionic terminals in sympathetic ganglia of the cat. It was found that hemicholinium (HC-3) pretreatment with or without preganglionic stimulation did not cause any significant changes in the ZIO positivity of cholinergic nerve terminals. The authors suppose that there is no direct relation between the ZIO positivity of axon terminals and the functioning of cholinergic transmission.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 13 (1966), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: A fraction enriched in capillaries has been prepared from the guinea pig cerebral cortex. The purity of this fraction was checked by light- and electron-microscopic examination and by its high enrichment in alkaline phosphatase and γ-glutamyl transpeptidase. In the capillary-rich fraction, the endogenous level of histamine was 1.9%’of that measured in the initial hornogenate. The histamine-synthesizing enzyme, I-histidine decarboxylase, and the metabolizing enzyme, histamine-N-methyltransferase, were barely detectable. In addition, histamine elicits a twofold stimulation in the accumulation of cyclic AMP in this capillary fraction with an EC50 of 5 γM. Agonists and antagonists of the two types of histamine receptors (H1 and H2) were used for the characterization of the receptors mediating this action: H2-receptor agonists were able to activate the adenylate cyclase with “relative potencies” similar to that found on typical H2-receptors, and cimetidine, a specific H2-receptor antagonist, competitively inhibited the response to histamine with a K1 value reflecting its interaction with a single population of H2-receptors. On the contrary, data obtained with H1-receptor agonists and antagonists reflect their interaction with H2-receptors rather than H1-receptors. Thus H2-receptors are involved in the activation of adenylate cyclase of the capillary fraction.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 29 (1977), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Synaptic vesicles were prepared from guinea-pig cerebral cortex on a continuous D2O-H2O(1:1)-sucrose gradient and purified in the presence of 1 mm-EGTA by chromatography on columns of glass beads of controlled pore size. As markers, endogenous ACh, NA, dopamine and DβH were measured.Two distinct populations of synaptic vesicles were recognized between the layers of 0.2–0.3 m- and 0.3–0.5 m-sucrose, which differed from each other both in electron microscopic appearance and transmitter content. The less dense vesicles had a much higher ACh content than the more dense vesicles which were composed mainly of somewhat larger particles with high NA and dopamine content. DβH was found to be present in substantial amounts in guinea-pig cortex and was located in the synaptic vesicle fractions having high CA content.After glass bead chromatography the vesicle preparations were morphologically homogeneous, practically free from other subcellular elements and were contaminated with each other by not more than 10%The yields were 0.2 and 0.1 mg protein g cortex−1 tissue for ‘cholinergic’ and ‘adrenergic’ vesicle preparations, respectively.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 24 (1975), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
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