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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Mycorrhiza 8 (1998), S. 61-65 
    ISSN: 1432-1890
    Keywords: Key words Lignin degradation ; Fenton reaction ; Hymenoscyphus ericae ; Lignin peroxidase ; Ectomycorrhizal fungi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Several reports attest to the apparent ability of some ectomycorrhizal (ECM) and ericoid (ERM) mycorrhizal fungi to produce peroxidase enzyme activities during growth in axenic culture. In critically reviewing these data, we highlight that apparent peroxidase activities have been observed during growth in media containing 60–70 μM Fe. ECM and ERM fungi are known to produce H2O2 via carbohydrate oxidase activity and conditions in common culture media are favourable to the production of hydroxyl radicals, superoxide radicals and ferryl ions via the Fenton reaction. Free radicals so produced can mediate oxidation of substrates commonly used in presumptive peroxidase assays, leading to false-positive results. We argue that there is currently no evidence to support production of peroxidase activity by ECM or ERM fungi, but highlight circumstances in which peroxidase expression might be observed in future work.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1106
    Keywords: Deiters' nucleus ; Medial longitudinal fasciculus ; Fictive locomotion ; Spinal cord ; Interneurons ; Decerebrate cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study compares some characteristics of the disynaptic excitatory pathways from the lateral vestibular nucleus (LVN) and medial longitudinal fasciculus (MLF) to lumbosacral α-motoneurons in the decerebrate cat. We used the spatial facilitation technique to test whether disynaptic LVN and MLF excitatory postsynaptic potentials (EPSPs) are produced by common last-order interneurons in the lumbosacral segments of the spinal cord. Of 77 motoneurons examined, 26 exhibited disynaptic EPSPs from both supraspinal sources. No spatial facilitation was found between LVN and MLF EPSPs in 21 of 24 cells that were adequately tested. In 3 of 23 cells (all flexor motoneurons), some spatial facilitation was found in some but not all trials. These observations suggest that stimulation of the LVN and MLF produces disynaptic EPSPs in motoneurons through largely separate populations of last-order interneurons. Disynaptic MLF and LVN EPSPs showed parallel patterns of modulation during fictive locomotion. Maximal disynaptic EPSP amplitudes occurred during the phase of the step cycle when the recorded motoneuron, whether flexor or extensor, exhibited depolarizing locomotor drive potentials and the corresponding muscle nerve was active. These observations, taken together, suggest that disynaptic LVN and MLF EPSPs are produced in motoneurons by at least four separate populations of segmental last-order excitatory interneurons, with separate populations projecting to flexor versus extensor cells. The results also suggest that the modulation of the disynaptic EPSPs during fictive locomotion is mainly due to premotoneuronal convergence of input from the respective descending systems and from the segmental central pattern generator for locomotion onto common interneurons.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 128 (1999), S. 263-277 
    ISSN: 1432-1106
    Keywords: Key words Spinal cord ; Motoneurons ; DOPA ; Locomotion ; Scratching ; Spatial facilitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  This review examines the proposition that state-dependent modulation of transmission through spinal reflex pathways can be used as an investigative tool to reveal details about the organization of spinal interneurons into functional circuits. The first set of examples includes the use of spinal and supraspinal lesions, as well as the administration of the drug l-dihydroxyphenylalanine (l-DOPA), to produce different, relatively stable ”states” of the central nervous system (CNS), revealing previously unsuspected spinal pathways activated by the flexor reflex afferents (FRA). The second set of examples deals with the use of fictive locomotion and scratching to investigate the organization of oligosynaptic excitatory and inhibitory reflex pathways from cutaneous and muscle afferents. As in the first set of examples, several hitherto unknown reflex pathways have been found only during the flexion or extension phases of rhythmic locomotion, which are regarded as different CNS states. Differences in the patterns of control can be used to infer the existence of distinct sets of reflex pathway interneurons that have remarkably precise input/output relations.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Plasma-based ion implantation (PBII) is a recent method to implant ions into materials for modifying surface properties. Negative high voltage pulses are applied to the substrate to extract ions from the plasma and accelerate them directly onto the substrate surface. The main advantages of PBII over ion beam implantation are its simplicity for processing large surfaces or three-dimensional objects, and the possibility of preparing surfaces at low ion bombardment energy prior to the implantation process. However, in contrast to conventional ion implantation, the PBII process does not apply mass selection. Due to the wide ion sheath expansion (a few tens of cm), large volumes of plasma are mandatory around the substrate. Multipolar discharges, which produce a peripheral ionization facing the substrate and can be easily scaled up, are well adapted to the PBII process and thus widely used. However, hot filaments to sustain plasmas of reactive gases in multipolar magnetic field structures are progressively phased out in favor of distributed electron cyclotron resonance (DECR) plasma sources. The principle, the design, and the performances of DECR plasmas are presented. Then, PBII in DECR plasmas is illustrated through two selected examples.© 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-5036
    Keywords: cellulase ; ericoid mycorrhizas ; hemicellulase ; lignin degradation ; pectinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Hymenoscyphus ericae (Read) Korf & Kernan is known to form mycorrhizas with a number of host plants in the Ericaceae. The fungus produces a range of extracellular enzyme activities which have the potential to mediate utilisation of organic sources of nitrogen and phosphorus in soil. H. ericae has recently been shown also to produce enzyme activities that may allow the fungus to decompose components of the plant cell wall, facilitating access to mineral nutrients sequestered within the walls of moribund plant cells. In this review we assess the evidence for production of cellulolytic, hemicellulolytic, pectinolytic and ligninolytic activities by H. ericae and discuss their likely relevance to nutrient cycling processes.
    Type of Medium: Electronic Resource
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