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- Angerbjörn, Anders, et al.
(author)
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Dietary Variation in Arctic Foxes (Alopex-Lagopus) - an Analysis of Stable Carbon Isotopes
- 1994
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In: Oecologia. ; 99:3-4, s. 226-232
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Journal article (peer-reviewed)abstract
- We used stable carbon isotopes to analyse individual variation in arctic fox diet. We extracted collagen from bones (the lower jaw), and measured stable carbon isotopes. The foxes came from three different localities: Iceland, where both microtines and reindeer are rare; west Greenland, where microtines are absent; and Sweden, where seat analyses showed the primary food to be microtine rodents and reindeer. The Icelandic samples included foxes from both coastal and inland habitats, the Swedish sample came from an inland area, and the Greenland sample from coastal sites. The spatial variation in the isotopic pattern followed a basic division between marine and terrestrial sources of protein. Arctic foxes from inland sites had delta(13)C values of -21.4 (Ice land) and -20.4 parts per thousand (Sweden), showing typical terrestrial values. Coastal foxes from Greenland had typical marine Values of -14.9 parts per thousand, whereas coastal foxes from Iceland had intermediate values of -17.7 parts per thousand. However, there was individual variation within each sample, probably caused by habitat heterogeneity and territoriality among foxes. The variation on a larger scale was related to the availability of different food items. These results were in accordance with other dietary analyses based on seat analyses. This is the first time that stable isotopes have been used to reveal individual dietary patterns. Our study also indicated that isotopic values can be used on a global scale.
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| 2. |
- Gustafson, Ingvar, et al.
(author)
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Brain cortical tissue levels of noradrenaline and its glycol metabolites : effects of ischemia and postischemic administration of idazoxan
- 1992
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In: Experimental Brain Research. - 0014-4819. ; 90:3, s. 551-556
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Journal article (peer-reviewed)abstract
- The brain noradrenaline (NA) system is known to modulate ischemic neuronal damage, and the turnover of NA has been suggested to increase in the early recovery period following cerebral ischemia. Using HPLC and gas chromatography-mass spectrometry we analyzed the tissue levels of NA and its metabolites, 3,4-dihydroxyphenylethyleneglycol (DHPG) and 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG), in rat brain cortex after 10 min of forebrain ischemia followed by 1 h of recirculation. The effect of idazoxan, given in cerebro-pbrotective doses, as a bolus of 0.1 mg·kg-1 immediately after ischemia followed by 10 μg·kg-1·min-1 for 1 h, was also investigated. Ischemia decreased basal NA cortical levels from 384 ng/g tissue in control animals to 214 ng/g, while DHPG increased from 74 to 103 ng/g (+39%) and MHPG from 82 to 154 ng/g (+88%). Conjugated but not free DHPG increased, while both free and conjugated MHPG increased equally. The findings indicate an enhanced postischemic NA turnover with a major proportion of uptake and metabolism occurring extraneuronally, possibly secondary to a saturation of neuronal NA uptake in the postischemic phase. Idazoxan further increased NA turnover, as evidenced by higher postischemic levels of free MHPG and a higher MHPG/NA ratio. A correlation may exist between the protective action of idazoxan and its effect on NA turnover.
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