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  • 1
    Electronic Resource
    Electronic Resource
    Attempted endogenous tissue repair following experimental spinal cord injury in the rat: involvement of cell adhesion molecules L1 and NCAM? (2000)
    Oxford, UK : Blackwell Science Ltd
    European journal of neuroscience 12 (2000), S. 0 
    Details
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: It is widely accepted that the devastating consequences of spinal cord injury are due to the failure of lesioned CNS axons to regenerate. The current study of the spontaneous tissue repair processes following dorsal hemisection of the adult rat spinal cord demonstrates a phase of rapid and substantial nerve fibre in-growth into the lesion that was derived largely from both rostral and caudal spinal tissues. The response was characterized by increasing numbers of axons traversing the clearly defined interface between the lesion and the adjacent intact spinal cord, beginning by 5 days post operation (p.o.). Having penetrated the lesion, axons became associated with a framework of NGFr-positive non-neuronal cells (Schwann cells and leptomeningeal cells). Surprisingly few of these axons were derived from CGRP- or SP-immunoreactive dorsal root ganglion neurons. At the longest survival time (56 days p.o.), there was a marked shift in the overall orientation of fibres from a largely rostro-caudal to a dorso-ventral axis. Attempts to identify which recognition molecules may be important for these re-organizational processes during attempted tissue repair demonstrated the widespread and intense expression of the cell adhesion molecules (CAM) L1 and N-CAM. Double immunofluorescence suggested that both Schwann cells and leptomeningeal cells contributed to the pattern of CAM expression associated with the cellular framework within the lesion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00228.x
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  • 2
    Electronic Resource
    Electronic Resource
    Transmitter release in tetanus and botulinum A toxin-poisoned mammalian motor endplates and its dependence on nerve stimulation and temperature (1983)
    Springer
    Pflügers Archiv 399 (1983), S. 228-234 
    Details
    ISSN: 1432-2013
    Keywords: Motor nerve terminal ; Botulinum toxin ; Tetanus toxin ; Transmitter release ; Temperature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of tetanus toxin (TeTx) and botulinum A toxin (BoTx) on spontaneous and nerve-evoked transmitter release have been compared in mouse hemidiaphragms poisoned in vitro. At 37°C endplates poisoned with either of these agents were characterized by (1) a decrease of miniature endplate potential (m.e.p.p.)-frequency to less than 30/min for TeTx and 3/min for BoTx, (2) reduced mean m.e.p.p.-amplitude and (3) 100% failure to show endplate potentials (e.p.p.s) in response to single nerve stimuli. In addition (4) tetanic nerve stimulation and/or reduction of temperature to about 20°C caused a remarkable increase in the nerveevoked transmitter release, but did not affect the low frequency of spontaneous m.e.p.p.s. However, several important differences exist between the effects of both toxins. (1) At room temperature even single nerve stimuli could elicit e.p.p.s in BoTx-muscles the failure rate being about 80%. For TeTx the failure was 100%. However, if the nerve was stimulated with higher frequencies (〉5Hz), the probability of quantal release increased, the delay for release from the onset of stimulation being several seconds and similar to that observed at 37°C. (2) TeTx distorted the synchronous release of quanta increasing the distribution of their synaptic delays. BoTx did not influence the time course of the phasic secretion process in response to nerve action potentials. (3) TeTx preferentially blocked the release of spontaneous m.e.p.p.s of large amplitude without affecting the frequency of the small amplitude ones, while BoTx inhibited both the small and large amplitude m.e.p.p.s. The distribution of the amplitudes of the nerve-evoked m.e.p.p.s were similar to those of spontaneous m.e.p.p.s before the blockade with the toxins. We conclude that TeTx and BoTx act at different stages in the chain of events that result in spontaneous and in nerveevoked transmitter release at motor endplates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00656720
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  • 3
    Electronic Resource
    Electronic Resource
    Responses of photosynthetic O2 evolution to PPFD in the CAM epiphyte Tillandsia usneoides L. (Bromeliaceae) (1989)
    Springer
    Photosynthesis research 21 (1989), S. 145-150 
    Details
    ISSN: 1573-5079
    Keywords: acclimation ; Crassulacean acid metabolism ; epiphyte ; irradiance ; O2 evolution ; Tillandsia usneoides ; titratable acidity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Past studies of the effects of varying levels of photosynthetic photon flux density (PPFD) on the morphology and physiology of the epiphytic Crassulacean acid metabolism (CAM) plant Tillandsia usneoides L. (Bromeliaceae) have resulted in two important findings: (1) CAM, measured as integrated nocturnal CO2 uptake or as nocturnal increases in tissue acidity, saturates at relatively low PPFD, and (2) this plant does not acclimate to different PPFD levels, these findings require substantiation using photosynthetic responses immediately attributable to different PPFD levels, e.g., O2 evolution, as opposed to the delayed, nocturnal responses (CO2 uptake and acid accumulation). In the present study, instantaneous responses of O2 evolution to PPFD level were measured using plants grown eight weeks at three PPFD (20–45, 200–350, and 750–800 μmol m-2s-1) in a growth chamber, and using shoots taken from the exposed upper portions (maximum PPFD of 800 μmol m-2s-1) and shaded lower portions (maximum PPFD of 140 μmol m-2s-1) of plants grown ten years in a greenhouse. In addition, nocturnal increases in acidity were measured in the growth chamber plants. Regardless of the PPFD levels during growth, O2 evolution rates saturated around 500 μmol m-2s-1. Furthermore, nocturnal increases in tissue acidity saturated at much lower PPFD. Thus, previous results were confirmed: photosynthesis saturated at low PPFD, and this epiphyte does not acclimate to different levels of PPFD.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00037178
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  • 4
    Electronic Resource
    Electronic Resource
    Stereoselective Substitution at Phenyl-Substituted γ-Lactols with Organometallic Compounds (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 871-876 
    Details
    ISSN: 0009-2940
    Keywords: γ-Lactone ; Reduction ; γ-Lactol ; Lewis acid ; Tetrahydrofurans ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A variety of monosubstituted γ-lactols 4-6 were prepared in good yields by DIBAL reduction of the corresponding γ-lactones 1-3. The monophenyl-substituted lactols 4b-6b were transformed into disubstituted tetrahydrofuran derivatives by replacement of the hydroxyl group by the alkyl residue of organometallic compounds used as nucleophiles. The diastereoselectivity of the substitution was found to depend strongly on the substitution pattern of the γ-lactols. For the reaction of the 3- and 4-substituted derivatives 4b and 5b, respectively, good to excellent trans selectivity was observed, while the 5-substituted derivative reacted without any diastereoselectivity. These results were interpreted by means of the Felkin-Anh model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280904
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