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  • Central noradrenergic system  (1)
  • Conifers  (1)
  • 1
    ISSN: 1432-2013
    Keywords: Vasopressin ; Central noradrenergic system ; Locus coeruleus ; Control of posture ; Vestibulospinal reflexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Vasopressin (VP) acts as a neurotransmitter or a neuromodulator on noradrenergic locus coeruleus (LC) neurons by exciting them. Experiments were performed in precollicular decerebrate cats to investigate whether direct infusion of VP into the LC complex of one side produced changes in posture as well as in the gain of vestibulospinal reflexes acting on forelimb extensors. Unilateral microinjection of 0.25 μl VP solution (10−11 μg/μl saline) into the LC complex increased the extensor rigidity in the ipsilateral limbs, while that of the contralateral limbs either remained unmodified or slightly decreased. The amplitude of modulation and thus the response gain of both the ipsilateral and the contralateral triceps brachii to roll tilt of the animal leading to stimulation of labyrinth receptors decreased (t-test, P〈0.001 for both the ipsilateral and the contralateral responses). Moreover, a slight decrease in phase lead of the responses was observed. These findings occurred 5–10 min after the injection, were fully developed within 30 min and disappeared in about 2 h. The changes in posture as well as in the gain of vestibulospinal reflexes described above were site specific and depended upon the injected neuropeptide. They were attributed to tonic activation of presumptive noradrenergic neurons, which exert a facilitatory influence on limb extensor motoneurons either directly, by utilizing the coeruleospinal pathway, or indirectly by inhibiting the dorsal pontine reticular formation and the related medullary inhibitory reticulospinal neurons.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2242
    Keywords: Key words Somaclonal variation ; Somatic embryogenesis ; Conifers ; RAPD ; Trisomy ; Chimerism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four embryogenic clones of Norway spruce have been subcultivated and observed over several years to determine the evolution of production of mature embryos and to assess the quality of the embryos produced. A wide range of intraclonal quantitative and qualitative variability has been observed within this production. Certain morphologic deviations appeared at the immature stage and after maturation, such as immature embryos with a diffuse organization, complete or part albino mature embryos or acclimated somatic seedlings comparable to dwarf mutants. All of these phenotypic variations could be the result of a modification of the genome itself or of only the expression of the genome. Two approaches, chromosome counting and RAPD (random amplified polymorphic DNA), were chosen for their capacity to detect genotypic variations: respectively, genomic and chromosomic or genic mutations. The cytogenetic approach revealed, for the first time in this species, three cases of mutated acclimated somatic plants: one totally trisomic and two chimeras with trisomic buds and diploid roots. Other cases of 5-year-old trisomic, double trisomic, tetraploid or mixoploid embryogenic masses were also detected. The molecular approach (RAPD) revealed no somaclonal variation despite the large sample of DNA and primers used and the important interclonal variation observed.
    Type of Medium: Electronic Resource
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