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  • 1
    ISSN: 0992-7689
    Keywords: Ionosphere (modelling and forecasting; polar ionosphere) ; Radio Science (instruments and techniques)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The tomographic reconstruction technique generates a two-dimensional latitude versus height electron density distribution from sets of slant total electron content measurements (TEC) along ray paths between beacon satellites and ground-based radio receivers. In this note, the technique is applied to TEC values obtained from data simulated by the Sheffield/UCL/SEL Coupled Thermosphere/Ionosphere/Model (CTIM). A comparison of the resulting reconstructed image with the ‘input’ modelled data allows for verification of the reconstruction technique. All the features of the high-latitude ionosphere in the model data are reproduced well in the tomographic image. Reconstructed vertical TEC values follow closely the modelled values, with the F-layer maximum density (NmF2) agreeing generally within about 10%. The method has also been able successfully to reproduce underlying auroral-E ionisation over a restricted latitudinal range in part of the image. The height of the F2 peak is generally in agreement to within about the vertical image resolution (25 km).
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0533
    Keywords: Intoxication ; Dog ; Clioquinol ; 2,5-hexanedione ; Distal axonopathy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The central distal axonopathy induced in dogs by the administration of high doses of clioquinol is contrasted with the central-peripheral distal axonopathy precipitated by intoxication with 2,5-hexanedione. Mature, pure-bred Beagle dogs received a daily oral dose of 400 mg/kg of clioquinol for up to 7 months, or 1 ml per animal (approximately corresponding to 110 mg/kg) of 2,5-hexanedione for up to 5 months. Intoxicated and control animals were killed and perfused at monthly intervals, so that the spatial-temporal development of the lesion could be followed and correlated with clinical symptoms. During the treatment, dogs intoxicated with 2,5-hexanedione developed symptoms of peripheral neuropathy consisting of flaccid weakness, muscle atrophy, hind-limb foot-drop and areflexia. By contrast, the dogs surviving clioquinol intoxication exhibited a stiff-legged gait, hyperreflexia but no muscle atrophy. Light and electron microscope examination of central and peripheral nervous tissue from dogs intoxicated with 2,5-hexanedione revealed giant axonal swelling and distal axonal degeneration. By contrast, dogs receiving clioquinol showed a distal axonal degeneration confined to the optic tract and the long spinal cord tracts, without any visible involvement of peripheral nerves.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract— Neurotoxic hexacarbon compounds 2,5-hexanedione (2,5-HD) and methyl n-butyl ketone (MnBK) inhibit crystalline and endogenous CNS and PNS glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Preincubation of the enzyme with the toxin was necessary for inhibition. The enzyme activity of GAPDH was preserved by the addition of dithiothreitol in the presence of either neurotoxin. By contrast, lactate dehydrogenase (LDH) activity was not inhibited by these neurotoxic chemicals. Neurologically inactive compounds 1,6-hexanediol and acetone failed to inhibit GAPDH. The present data indicate that 2,5-HD and M “BK block energy metabolism by inhibiting glycolysis at the site of GAPDH. These observations may account for the known failure of GAPDH-dependent axonal transport and the axonal degeneration which occurs in hexacarbon neuropathy.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An improved scheme for polarization insensitive four-wave mixing in semiconductor optical amplifiers (SOAs) is proposed, utilizing just one polarization insensitive SOA and one input pump wave, and without compromising the achievable conjugate power compared with that obtained from a conventional dual-pump co-propagating configuration. For frequency detuning larger than ∼300 GHz for a device length of say 500 μm, polarization sensitivity less than ∼0.8 dB can be obtained. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 199 (1963), S. 1298-1299 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We have administered thyroxine sodium (1 or 2 mg/kg daily) to groups of rat and mice and then tested them for sensitivity to histamine. In all experiments, a temporary increase in sensitivity to histamine was noted, coupled with elevated tissue and urinary histamine. Continued treatment with ...
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  • 7
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 184 (1959), S. 2020-2020 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In the first experiments, it was confirmed that intra-peritoneal injections of soluble insulin (4-12 units/ kgm.) given 15 min. before egg white (24 ml./kgm.) or dextran (300 mgm./kgm.) aggravated the anaphylac-toid reactions; its speed of onset was increased, and the reaction which developed was ...
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  • 8
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 237 (1972), S. 513-514 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Fig. 1 Effect of age of young chickens on the response to peripherally-administered ouabain. Chicks received 0.7 mg/kg ouabain intraperitoneally (x) 2 days, (O) 3 days, (?) 4 days, (?) 5 days or (?) 10 days after hatching. In each case controls received 10 ml./kg saline intraperitoneally. Ranger ...
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 200 (1963), S. 895-896 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The in vitro anti-5-hydroxytryptamine activity of compounds was investigated using the isolated oestrus rat uterus preparation. Dose-response curves to 5-hydroxytryptamine (5HT) were obtained in the presence or absence of varying concentrations of antagonist and the concentration of antagonist ...
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  • 10
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Severance of a peripheral nerve leads to a characteristic series of events in the distal stump, including the dissolution of axons and myelin and the proliferation of Schwann cells within their basal lamina. This study examines the relationship between the spatial-temporal pattern of the induction of the Schwann cell S phase, loss of the structural and functional properties of axolemma, and the clearance of myelin debris in the cat tibial nerve. Nerve transection stimulated a monophasic increase in [3H]thymidine incorporation that peaked at 4 days post-transection throughout an 80-mm length of distal stump. Light microscope autoradiography revealed prominent incorporation into Schwann cells of myelinated fibres. Treatment of distal stumps with mitomycin C at the time of nerve transection greatly retarded thymidine incorporation and clearance of myelin debris, but not the time course of axonal degeneration, decline in the synthesis of the major myelin glycoprotein, P0, or the onset of ovoid formation. Nerve transection also greatly reduced the specific uptake of [3H]saxitoxin (STX), a ligand which binds to voltage-sensitive sodium channels. Binding in the distal stump fell precipitously to 20% of the normal at 4 days post-transection, concurrent with the peak of thymidine incorporation. This low level of binding was maintained for periods of up to 70 days, demonstrating that some STX binds to structures other than axons in denervated distal stumps. Prior treatment with mitomycin C delayed the loss of specific STX binding. In conclusion, these studies suggest that: (a) Schwann cell DNA replication- and/or mitosis regulates other events during Wallerian degeneration, including myelin degeneration, catabolism of P0 and the clearance of sodium channels from nodal axolemma; (b) the decline in P0 synthesis and/or shift to synthesis of less extensively processed P0 is independent of the induction of Schwann cell S phase; and (c) Schwann cells enveloping myelinated axons enter S phase within a 24-h period throughout the entire 80-mm length of distal stump.
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