| 1. |
- Jonsdottir, I.H.
(författare)
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Neuropeptides and their interaction with exercise and immune function
- 2000
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Ingår i: Immunology and Cell Biology. - Oxford : Blackwell Publishing. - 0818-9641 .- 1440-1711. ; 78:5, s. 562-570
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Forskningsöversikt (refereegranskat)abstract
- It is known today that the immune system is influenced by various types of psychological and physiological stressors, including physical activity. It is well known that physical activity can influence neuropeptide levels both in the central nervous system as well as in peripheral blood. The reported changes of immune function in response to exercise have been suggested to be partly regulated by the activation of different neuropeptides and the identification of receptors for neuropeptides and steroid hormones on cells of the immune system has created a new dimension in this endocrine-immune interaction. It has also been shown that immune cells are capable of producing neuropeptides, creating a bidirectional link between the nervous and immune systems. The most common neuropeptides mentioned in this context are the endogenous opioids. The activation of endogenous opioid peptides in response to physical exercise is well known in the literature, as well as the immunomodulation mediated by opioid peptides. The role of endogenous opioids in the exercise-induced modulation of immune function is less clear. The present paper will also discuss the role of other neuroendocrine factors, such as substance P, neuropeptide Y and vasoactive intestinal peptide, and pituitary hormones, including growth hormone, prolactin and adrenocorticotrophin, in exercise and their possible effects on immune function.
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| 2. |
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| 3. |
- 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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| 4. |
- Persson, Anders I., 1973, et al.
(författare)
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Differential regulation of hippocampal progenitor proliferation by opioid receptor antagonists in running and non-running spontaneously hypertensive rats.
- 2004
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Ingår i: The European journal of neuroscience. - : Wiley. - 0953-816X .- 1460-9568. ; 19:7, s. 1847-55
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Tidskriftsartikel (refereegranskat)abstract
- Voluntary running in mice and forced treadmill running in rats have been shown to increase the amount of proliferating cells in the hippocampus. Little is known as yet about the mechanisms involved in these processes. It is well known that the endogenous opioid system is affected during running and other forms of physical exercise. In this study, we evaluated the involvement of the endogenous opioids in the regulation of hippocampal proliferation in non-running and voluntary running rats. Nine days of wheel running was compared with non-running in spontaneously hypertensive rats (SHR), a rat strain known to run voluntarily. On the last 2 days of the experimental period all rats received two daily injections of the opioid receptor antagonists naltrexone or naltrindole together with injections of bromodeoxyuridine to label dividing cells. Brain sections from the running rats showed approximately a five-fold increase in newly generated cells in the hippocampus, and this increase was partly reduced by naltrexone but not by naltrindole. By contrast, both naltrexone and naltrindole increased hippocampal proliferation in non-running rats. In non-running rats the administration of naltrexone decreased corticosterone levels and adrenal gland weights, whereas no significant effects on these parameters could be detected for naltrindole. However, adrenal gland weights were increased in naltrexone- but not in naltrindole-administered running rats. In addition, in voluntary running rats there was a three-fold increase in the hippocampal levels of Met-enkephalin-Arg-Phe compared with non-runners, indicating an increase in opioid activity in the hippocampus during running. These data suggest an involvement of endogenous opioids in the regulation of hippocampal proliferation in non-running rats, probably through hypothalamic-pituitary-adrenal axis modulation. During voluntary running in SHR naltrexone altered hippocampal proliferation via as yet unknown mechanisms.
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| 5. |
- Stenstrom, A., et al.
(författare)
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Genetic variation and clonal diversity in four clonal sedges (Carex) along the Arctic coast of Eurasia
- 2001
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Ingår i: Molecular Ecology. - 0962-1083 .- 1365-294X. ; 10:2, s. 497-513
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Tidskriftsartikel (refereegranskat)abstract
- We studied the structure of genetic variation (at both ramet- and genet-level) and clonal diversity within and among populations in the four closely related arctic clonal sedges Carex bigelowii, C. ensifolia, C. lugens and C. stans by use of allozyme markers. Compared to other sedges and arctic plants, the studied taxa all had high levels of genetic variation, both within populations and taxa. These taxa contained most of the total gene diversity (HT) within populations and a small part of the diversity among populations (GST ranged 0.05-0.43). Carex bigelowii had genetic variation (HS = 0.173, mean for populations) at a comparable level to other outbreeding arctic plants and to other widespread, rhizomatous and mainly outbreeding Carex species. In contrast, C. ensifolia (HS = 0.335), C. lugens (HS = 0.339) and C. stans (HS = 0.294) had within-population variations that were higher than in most other studied Carex species and for arctic plants in general. Genetic variation was not related to any tested environmental variable, but it was lower in areas deglaciated only 10 000 years BP compared to areas deglaciated 60 000 years BP or not glaciated at all during the Weichselian. All the populations were multiclonal, except for two populations of C. stans that were monoclonal. In contrast to genetic variation, clonal diversity decreased with latitude and did not differ between areas with different times of deglaciation. In accordance with previous studies, C. bigelowii and C. lugens were found to be outbreeding, while C. ensifolia and C. stans had mixed mating systems.
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| 6. |
- Stenström, A, et al.
(författare)
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Genetic variation and clonal diversity in four clonal sedges (Carex) along the Arctic coast of Eurasia
- 2001
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 10:2, s. 497-513
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Tidskriftsartikel (refereegranskat)abstract
- We studied the structure of genetic variation (at both ramet- and genet-level) and clonal diversity within and among populations in the four closely related arctic clonal sedges Carex bigelowii, C. ensifolia, C. lugens and C. starts by use of allozyme markers. Compared to other sedges and arctic plants, the studied taxa all had high levels of genetic variation, both within populations and taxa. These taxa contained most of the total gene diversity (H-T) within populations and a small part of the diversity among populations (G(ST) ranged 0.05-0.43). Carex bigelowii had genetic variation (H-S = 0.173, mean for populations) at a comparable level to other outbreeding arctic plants and to other widespread, rhizomatous and mainly outbreeding Carex species. In contrast, C. ensifolia (H-S = 0.335), C. lugens (H-S = 0.339) and C. stans (H-S = 0.294) had within-population variations that were higher than in most other studied Carex species and for arctic plants in general. Genetic variation was not related to any tested environmental variable, but it was lower in areas deglaciated only 10 000 years BP compared to areas deglaciated 60 000 years BP or not glaciated at all during the Weichselian. All the populations were multiclonal, except for two populations of C. starts that were monoclonal. In contrast to genetic variation, clonal diversity decreased with latitude and did not differ between areas with different times of deglaciation. In accordance with previous studies, C. bigelowii and C. lugens were found to be outbreeding, while C. ensifolia and C. stans had mixed mating systems.
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