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  • 1990-1994  (2)
  • Rat  (1)
  • West African parkland savanna  (1)
  • 1
    ISSN: 1432-1106
    Keywords: Swallowing ; Nucleus tractus solitarius ; Excitatory amino acids ; Ketamine anesthesia ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Swallowing is a patterned motor activity generated by neurons located within the nucleus tractus solitarius (NTS). An excitatory amino acid (EAA) neurotransmitter, such as glutamate (GLU), is suspected of being involved in the initiation of swallowing by NTS neuronal components. However, swallowing can still be elicited in animals anesthetized with ketamine, an antagonist of the N-methyl-D-aspartate (NMDA) subclass of EAA receptors. The present experiments were therefore designed to investigate the influence of EAA administration within the NTS on the swallowing motor acitivity of rats anesthetized with ketamine. Pressure microinjections of GLU in doses ranging from 25 to 500 pmol elicited swallowing. This effect was dose-dependent and was not reproduced when control injections of the vehicle solution were performed. Microinjections of the GLU agonists, quisqualate (QUIS) and NMDA, in doses ranging between 2.5 and 50 pmol, also induced swallowing motor activities. QUIS, like GLU, elicited a short series of swallows at a brief latency while NMDA generated long-lasting rhythmic swallowing with a longer latency. Swallowing induced by GLU microinjections (100 pmol) was suppressed almost completely by local pretreatment with either the broad spectrum EAA receptor antagonist, gamma-D-glutamylglycine (250 pmol), or the more selective non-NMDA antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione (50–100 pmol), but not by pretreatment with the selective NMDA antagonist, DL-2-amino-5-phosponovalerate (250 pmol). On the other hand, pretreatment with DL-2-amino-5-phosphonovalerate (50 pmol) suppressed the deglutitions induced by NMDA microinjections (10 pmol) but not those elicited by QUIS microinjections (10 pmol). These results provide evidence that swallowing can be induced by activation of EAA receptors of both the NMDA and the non-NMDA subclasses located within the NTS. Furthermore they indicate that both subclasses may still be active in ketamine-anesthetized animals.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Agroforestry systems 17 (1992), S. 97-118 
    ISSN: 1572-9680
    Keywords: West African parkland savanna ; tree-crop relations ; tree management ; shade influence ; Vitellaria paradoxa ; Parkia biglobosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Résumé Les rendements en graines de sorgho sous le karité et le néré sont respectivement environ 50% et 70% plus basses que celles hors des houppiers. La fertilité du sol, étant le facteur limitant pour la production primaire dans la région, est au moins assez favorable sous les arbres que hors des houppiers. L'ombre sous les arbres, réduisant la lumière sous le néré à 20% au minimum, est probablement largement responsable pour la réduction des rendements sous les arbres. Les profits par la vente des produits des arbres sont plus élevés que les pertes de rendements céréaliers, ce qui explique pourqoui les arbres sont conservés dans les champs. La taille des branches, la selection des cultures qui résistent l'ombre et la selection des arbres peuvent réduire les pertes de rendements, mais n'auront pas un grand effet sur la productivité des arbres ni des cultures.
    Notes: Abstract Sorghum grain yields under the karité and the néré are reduced by an average of 50% and 70% respectively, in comparison with yields in the open field. Soil fertility, limiting primary production in the region, is at least as favorable under the tree canopies as in the open field. Reduced light intensity, to a minimum of 20% under the néré canopy, is probably largely responsible for low sorghum production under the tree canopies. Benefits from the tree products are more valuable than losses in cereal yields, explaining why trees are maintained on the agricultural fields. Pruning of tree branches, selection of (shade-) crops and tree selection could reduce crop yield losses but cannot be expected to increase tree- and crop production.
    Type of Medium: Electronic Resource
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