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  • 1
    Electronic Resource
    Electronic Resource
    Functional connections are established in the deafferented rat spinal cord by peripherally transplanted human embryonic sensory neurons (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: Functionally useful repair of the mature spinal cord following injury requires axon growth and the re-establishment of specific synaptic connections. We have shown previously that axons from peripherally grafted human embryonic dorsal root ganglion cells grow for long distances in adult host rat dorsal roots, traverse the interface between the peripheral and central nervous system, and enter the spinal cord to arborize in the dorsal horn. Here we show that these transplants mediate synaptic activity in the host spinal cord. Dorsal root ganglia from human embryonic donors were transplanted in place of native adult rat ganglia. Two to three months after transplantation the recipient rats were examined anatomically and physiologically. Human fibres labelled with a human-specific axon marker were distributed in superficial as well as deep laminae of the recipient rat spinal cord. About 36% of the grafted neurons were double labelled following injections of the fluorescent tracers MiniRuby into the sciatic and Fluoro-Gold into the lower lumbar spinal cord, indicating that some of the grafted neurons had grown processes into the spinal cord as well as towards the denervated peripheral targets. Electrophysiological recordings demonstrated that the transplanted human dorsal roots conducted impulses that evoked postsynaptic activity in dorsal horn neurons and polysynaptic reflexes in ipsilateral ventral roots. The time course of the synaptic activation indicated that the human fibres were non-myelinated or thinly myelinated. Our findings show that growing human sensory nerve fibres which enter the adult deafferentated rat spinal cord become anatomically and physiologically integrated into functional spinal circuits.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1460-9568.2000.00245.x
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  • 2
    Electronic Resource
    Electronic Resource
    Functional organization of the nociceptive withdrawal reflexes (1992)
    Springer
    Experimental brain research 90 (1992), S. 469-478 
    Details
    ISSN: 1432-1106
    Keywords: Pain ; Nociception ; Spinal cord ; Withdrawal reflexes ; Spinal cord injury ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The spatial organization of the cutaneous input to hindlimb withdrawal reflexes was studied in spinalized, decerebrated, unanesthetized rats. Reflex activity in plantar flexors of the digits, pronators of the foot, dorsiflexors of the digits, and/or the ankle and flexors of the knee was recorded with electromyographic techniques for up to 12 h after spinalization. Graded mechanical (pinch) and thermal stimulation (CO2 laser) of the skin were used. Reflexes were absent (“spinal shock”) during approximately 10–20 min after spinalization. The reflex thresholds for pinch and CO2 laser stimulation then decreased considerably during the following 5–8 h. After this time, even mild pressure (less than 0.1 N/mm2) on the skin was sufficient to evoke a reflex in most muscles. During the period from about 0.5–3 h after spinalization, the nociceptive receptive field of each muscle usually corresponded to the area of the skin withdrawn by the muscle. Maximal responses were evoked from the area of the receptive field maximally withdrawn. During this period, responses to innocuous pinch were evoked mainly from the most sensitive area of the receptive fields. Concomitant with the decrease in reflex thresholds, the nociceptive receptive fields expanded for all muscles, often to include areas of the skin not withdrawn by the muscles. For most muscles, reflexes on tactile stimuli were eventually elicited from the entire receptive fields. The receptive fields for thermonociceptive and mechanonociceptive inputs were similar in most muscles. The interossei muscles were exceptional in that they responded very weakly to thermal stimulation. It is concluded that there are neuronal networks in the spinal cord that translate cutaneous nociceptive and tactile input into a withdrawal. However, the control exerted by descending pathways is necessary to maintain a functionally adequate excitability in these reflex pathways and an appropriate size for their receptive fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230929
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  • 3
    Electronic Resource
    Electronic Resource
    Evaluation of Alcaligenes eutrophus cells as an NADH regenerating catalyst in organic-aqueous two-phase system (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 57 (1998), S. 79-86 
    Details
    ISSN: 0006-3592
    Keywords: Alcaligenes eutrophus ; hydrogenase ; NADH regeneration ; HLADH ; organic solvent ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A soluble NAD-dependent hydrogenase contained in Alcaligenes eutrophus was evaluated as a coenzyme regenerating catalyst in an organic-aqueous two-phase (predominantly organic) system. The horse-liver alcohol-dehydrogenase (HLADH) catalyzed reduction of cyclohexanone to cyclohexanol was used as a model reaction. The impact of different solvents (selected to span a large variety of principal properties) on the stability and activity of the HLADH, using substrate-driven regeneration, was studied. Solvents suitable for the HLADH were then selected for an evaluation of the hydrogenase-driven coenzyme regeneration. Hydrophobic solvents such as heptane, toluene, and 1,1,1-trichloroethane were found to be suitable for the coupled reactions catalyzed by HLADH and hydrogenase. Nonimmobilized cells, permeabilized with cetyl-trimethyl-ammonium bromide, were the most efficient preparation for the regeneration of NADH. The use of this preparation in heptane (10% water) was optimized with respect to the yield obtained in the HLADH-catalyzed reduction of cyclohexanone. Using the optimized conditions, yields of 99% cyclohexanol were obtained. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 57: 79-86, 1988.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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