| 1. |
- Jonsdottir, Ingibjörg H, 1966, et al.
(författare)
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Muscle contractions induce interleukin-6 mRNA production in rat skeletal muscles.
- 2000
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Ingår i: The Journal of physiology. - 0022-3751. ; 528 Pt 1, s. 157-63
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Tidskriftsartikel (refereegranskat)abstract
- 1. The present study explored the hypothesis that interleukin-6 (IL-6) might be locally produced in response to skeletal muscle contractions and whether the production might reflect the type of muscle contraction performed. Rats were anaesthetized and the calf muscles of one limb were stimulated electrically for concentric or eccentric contractions (4 x 10 contractions with 1 min of rest between the 4 series, 100 Hz). The contralateral muscles served as unstimulated controls. The mRNA levels for IL-6, the glucose transport protein GLUT-4 and beta-actin in the rat muscles (white and red gastrocnemius and soleus) were quantified by quantitative competitive RT-PCR. 2. The IL-6 mRNA level, measured 30 min after the stimulation, increased after both eccentric and concentric contractions and there were no significant differences in IL-6 mRNA levels between the different muscle fibre types. No significant increase in IL-6 mRNA level was seen in the unstimulated contralateral muscle fibres. 3. No increase in GLUT-4 mRNA level was detected, indicating that the increase in IL-6 mRNA level was not due to general changes in transcription. 4. We conclude that IL-6 is locally produced after muscle contraction, with no significant differences between different muscle fibre types. This local production of IL-6 is not due to general changes in transcription, since no changes in the level of GLUT-4 mRNA were found. The fact that increased IL-6 mRNA levels were seen after both concentric and eccentric contractions indicates that the production of IL-6 is not solely due to muscle damage, seen primarily after eccentric exercise.
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| 2. |
- Krebs, C. J., et al.
(författare)
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Terrestrial trophic dynamics in the Canadian Arctic
- 2003
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Ingår i: Canadian Journal of Zoology-Revue Canadienne De Zoologie. ; 81, s. 827-843
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish Tundra Northwest Expedition of 1999 visited 17 sites throughout the Canadian Arctic. At 12 sites that were intensively sampled we estimated the standing crop of plants and the densities of herbivores and predators with an array of trapping, visual surveys, and faecal-pellet transects. We developed a trophic-balance model using ECOPATH to integrate these observations and determine the fate of primary and secondary production in these tundra ecosystems, which spanned an 8-fold range of standing crop of plants. We estimated that about 13% of net primary production was consumed by herbivores, while over 70% of small-herbivore production was estimated to flow to predators. Only 9% of large-herbivore production was consumed by predators. Organization of Canadian Arctic ecosystems appears to be more top-down than bottom-up. Net primary production does not seem to be herbivore-limited at any site. This is the first attempt to integrate trophic dynamics over the entire Canadian Arctic.
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