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  • Methadone  (2)
  • maize  (2)
  • Abiotic factors  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Growth and alkaloid contents in leaves of Tabernaemontana pachysiphon Stapf (Apocynaceae) as influenced by light intensity, water and nutrient supply (1996)
    Springer
    Oecologia 107 (1996), S. 160-169 
    Details
    ISSN: 1432-1939
    Keywords: Monoterpene indole alkaloids ; Tropical trees ; Abiotic factors ; Growth ; C/N balance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The growth of Tabernaemontana pachysiphon (Apocynaceae) plants and the alkaloid content of leaves were investigated in the greenhouse at three levels of nutrient supply under two contrasting water and light regimes. We determined height increment, above-ground biomass production, leaf size, specific leaf weight and the content of the alkaloids apparicine, A2, isovoacangine, tubotaiwine and tubotaiwine-N-oxide. The effects of major controlling factors such as light, water and nutrient supply could be directly correlated with growth and were largely independent of each other. In contrast, leaf-alkaloid contents were influenced by interdependencies among the main factors and individually affected in a synergistic or antagonistic manner which deviated from the effects on growth. The following general trends could be identified with respect to the quantitatively predominant alkaloids apparicine, tubotaiwine and isovoacangine. Increasing nutrient supply had a positive effect on both growth and alkaloid content. Drought increased alkaloid content, but retarded growth. High light intensity lowered alkaloid content but promoted growth. We investigated the relationship between primary production and the production of secondary metabolites with respect to relative and total alkaloid content as well as in relation to the leaves' nitrogen status. Our results showed that under conditions of low nutrient supply, higher proportions of leaf nitrogen were allocated to alkaloids than at moderate or high nutrient supply. Under conditions of drought and low light, all plants allocated almost equal proportions of leaf nitrogen to alkaloids, regardless of fertiliser. Total alkaloid content per plant, however, increased with fertilisation. With respect to the N-allocation strategy, we found no indication of a trade-off between primary production and the production of secondary metabolites in this species. Rather, our results are in accordance with the carbon nutrient balance hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00327899
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Sustained ingestion of methadone and the sleep of monkeys (1978)
    Springer
    Psychopharmacology 60 (1978), S. 29-34 
    Details
    ISSN: 1432-2072
    Keywords: Sleep ; Methadone ; Sustained ingestion ; Monkey
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Methadone HCl was administered daily to four stump-tailed macaques. The animals' sleep was periodically examined throughout a year of methadone maintenance and, in two animals, during eight months of withdrawal. REM sleep was substantially decreased by methadone treatment and gradually returned to predrug values over a 6-to 8-month period of maintenance. Measures of non-REM sleep and awakenings showed similar disruption with no return to predrug values. These changes were not correlated with alterations in plasma-methadone concentrations. REM sleep rebound occurred temporarily upon drug with-drawal in two animals, but no consistent sleep disruption was apparent during the subsequent eight months. Contrary to some suggestions, therefore, tolerance to the sleep-disruptive effects of the drug may be specific and incomplete, and extended REM rebound upon withdrawal is not a universal response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00429175
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  • 3
    Electronic Resource
    Electronic Resource
    Methadone-induced changes in the visual evoked response recorded from multiple sites in the cat brain (1979)
    Springer
    Psychopharmacology 63 (1979), S. 89-95 
    Details
    ISSN: 1432-2072
    Keywords: Methadone ; Visual evoked responses ; Cortical ; Subcortical ; Cats
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Visual evoked responses (VERs) and EEG were recorded following the i.p. administration of five doses of methadone (0.5–4 mg/kg) to 12 adult cats, which were implanted with cortical and subcortical electrodes. Additional cats, subjected to the same drug regimen, were used to evaluate plasma methadone concentrations. Doses of methadone that produced plasma concentrations between 80 and 190 ng/ml differentially affected VERs recorded from cortical and subcortical sites. Of the subcortical structures evaluated, the limbic system, specifically the hippocampus, was the most sensitive to the effects of the drug. These effects appeared to be primarily depressant. Responses recorded from the reticular formation and centromedian were affected only by the highest dose of methadone, while VERs recorded from cortical sites were reliably altered following the two highest doses and appeared to reflect both excitation and depression. Behavioral changes, however, were clearly evidenced in some cats at lower doses of methadone. Therefore, the data suggest (1) that those structures evaluated electrophysiologically did not reflect the full force of the drug's action as evidenced by its effect on behavior, (2) that cortical and subcortical recording sites have differential sensitivities, and (3) that one clearly defined, principal site of action of methadone is absent in the cat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00426927
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Reassessment of root competition for P of field-grown maize in pure and mixed cropping (1988)
    Springer
    Plant and soil 106 (1988), S. 299-301 
    Details
    ISSN: 1573-5036
    Keywords: lupin ; maize ; phosphate ; root competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Root competition for phosphate (P) in the field was calculated with maize i) as singly grown plants, ii) in pure cropping and iii) in mixed cropping with lupin. The experimentally determined parameters used for this purpose were thein situ root-distance pattern as registered by autoradiography and the P-depletion cylinder around a maize root as determined autoradiographically under radial diffusional flow. The results do not indicate any competition for P between roots of adjacently grown plants in either pure or mixed cropping. On the other hand, the P-depletion cylinders of approximately one third of the roots of an individual maize plant were found to overlap. However, when allowance was made for the concentration gradients within a depletion cylinder, the actual competition for phosphate was less than 1%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02371230
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  • 5
    Electronic Resource
    Electronic Resource
    Development and replenishment of the P-depletion zone around the primary root of maize during the vegetation period (1987)
    Springer
    Plant and soil 101 (1987), S. 247-255 
    Details
    ISSN: 1573-5036
    Keywords: freeze-cutting ; dynamics ; depletion zone ; root longevity ; maize ; P-deficiency ; phosphate ; radioautography
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The dynamics of the development and replenishment of P-depletion zones around the primary root of maize (Zea mays L. cv ‘Garbo’) was studied during a vegetation period (80 days) under greenhouse conditions in a loamy sand of low P-availability. A recently described freeze-cutting technique was used to determine radial diffusion of labelled phosphate to the primary root. The development of the depletion zone was biphasic. In the initial phase after two days of growth of the primary root in a soil layer labelled with33P a minimum of isotopically exchangeable P (EP) was observed which had decreased to about 30% of its original amount at the root surface. At that time the corresponding P-concentration in the soil solution was calculated to be as low as 5×10−7 M. The depletion zone had already spread 0.4 mm from the root surface. During the second phase, between the 10th and 20th day of plant growth the concentration of EP at the root surface increased slowly but did not change markedly. However, the depletion zone continued to spread and after the 20th day of growth reached its maximal diameter (1.07 mm from the root surface) but remained completely within the root hair cyclinder; the single root hairs never exceeded 1.14 mm in length. The biphasic growth of the depletion zone was probably caused by proton extrusion of the root tip. Acidification of the soil solution from pH 5.8 to about 3.9 results in an about 3-fold rise of the concentration of desorbed phosphate and might also have activated acidophilic P-translocators of the root during the initial phase. Anion over cation uptake normally prevailing during the later stage of root development might resulted in a rise of the soil pH within the root hair zone. Consequently P-availability, as well as P-uptake capacity declined, but P-uptake by the seminal root still continued until the 20th day. Subsequently, the P-concentration within the depletion zone increased again while simultaneously its extent was reduced until it was almost completely replenished after 60 days indicating a loss of P-uptake capacity of the primary root. Within the root tissue33P was accumulated to about twice the concentration of that in the undepleted soils. This accumulation corresponded to periods of high uptake due to the development of root laterals. In the root cortex a high P-content was observed during the first 30 days of growth. At the onset of the reproductive stage of the plant the P-content of the shoot and especially in the developing seeds rose considerably at the cost of phosphate stored in the root cortex. The accumulation of33P in the root tissue indicated that nutrient gain was mainly achieved during the early stages of plant development and that P was temporarily stored to some extent within the root system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02370652
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