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- Andersson, Staffan, 1959, et al.
(författare)
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Multiple receivers, multiple ornaments, and a trade-off between agonistic and epigamic signaling in a widowbird.
- 2002
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Ingår i: The American naturalist. - : University of Chicago Press. - 1537-5323 .- 0003-0147. ; 160:5, s. 683-91
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Tidskriftsartikel (refereegranskat)abstract
- Sexual displays often involve several different ornamental traits. Yet most indicator models of sexual selection based on a single receiver (usually a choosy female) find that multiple handicap signals should be unstable. Here we study reasons for this contradiction, analyzing signal function, signal content, and trade-offs between signals in the polygynous red-collared widowbird Euplectes ardens. Males have both a long, graduated tail and a red carotenoid collar badge. Territory-holding "residents" have slightly shorter tails than the nonbreeding "floaters," but their carotenoid collars are 40% larger, and they have (on the basis of reflectance spectrometry and objective colorimetry) a 23-nm more long-wave ("redder") hue than floaters. This corroborates experimental evidence that the red collar is selected by male contest competition, whereas female choice is based almost exclusively on male tail length. Tail length is negatively correlated with the carotenoid signal, which together with body size and condition explains 55% of the variation in tail length. The trade-off in tail length and carotenoid investment is steeper among residents, suggesting an interaction with costs of territory defense. We propose that the "multiple receiver hypothesis" can explain the coexistence of multiple handicap signals. Furthermore, the trade-off between signal expressions might contribute to the inverse relation between nuptial tail elongation and coloration in the genus Euplectes (bishops and widowbirds).
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| 2. |
- Lindsay, Willow, 1980, et al.
(författare)
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Seasonal but not sex-biased gene expression of the carotenoid ketolase, CYP2J19, in the sexually dichromatic southern red bishop (Euplectes orix)
- 2022
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Ingår i: Royal Society Open Science. - : The Royal Society. - 2054-5703. ; 9:8
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Tidskriftsartikel (refereegranskat)abstract
- Intense red colours in birds are often owing to ketocarotenoids (KCs). In many land birds, KCs are oxidized from dietary yellow precursors, presumably by the avian carotenoid ketolase CYP2J19, the regulation and constraints of which have important implications for condition-dependence and honest signalling of carotenoid colour displays. We investigated hepatic CYP2J19 gene expression in the seasonally and sexually dichromatic southern red bishop (Euplectes orix) in relation to season, sex, progression of the prenuptial moult, testis size, body condition, redness and circulating sex steroids. A coloration function of CYP2J19 is supported by a seasonal upregulation prior to and during the carotenoid-depositing stage of the male prenuptial moult. However, CYP2J19 expression was similarly high in females (which do not moult prenuptially), and remained high in males after moult, suggesting additional or alternative roles of hepatic CYP2J19 or its products, such as detoxification or antioxidant functions. In males, the CYP2J19 upregulation preceded and was unrelated to the rise in plasma testosterone, but was correlated with androstenedione, probably of adrenal origin and compatible with luteinizing hormone-induced and (in females) oestrogen-suppressed moult. Finally, contrary to ideas that carotenoid ketolation rate mediates honest signalling of male quality, CYP2J19 expression was not related to plumage redness or male body condition.
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| 3. |
- Svensson, Henrik, 1982, et al.
(författare)
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Adipose tissue and body composition in women six years after gestational diabetes: factors associated with development of type 2 diabetes.
- 2018
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Ingår i: Adipocyte. - : Informa UK Limited. - 2162-397X .- 2162-3945. ; 7:4, s. 229-237
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Tidskriftsartikel (refereegranskat)abstract
- Factors differentiating women at highest risk of progression to type 2 diabetes mellitus (T2DM) after gestational diabetes mellitus (GDM) are incompletely known. Our aim was to characterize adipose tissue and body composition in relation to glucose metabolism in women with a history of GDM and to identify factors associated with development of T2DM. We examined glucose tolerance (OGTT), insulin sensitivity (HOMA-IR), body composition (anthropometry, air displacement plethysmography), and blood chemistry in 39 women 6years after GDM. An adipose tissue biopsy was obtained to assess the size, number, and lipolytic activity of adipocytes, and adipokine release and density of immune cells and blood vessels in adipose tissue. Normal glucose tolerance (NGT) was identified in 31 women and impaired glucose metabolism (IGM) in 8. Women with IGM had higher BMI/fat mass, and related expected adipose tissue features, than women with NGT. Ethnicity was similar in the groups, but numerically there was a higher proportion of European women in the NGT group and a higher proportion of non-European women in the IGM group. BMI was the best discriminator of NGT versus IGM (multivariable logistic regression: OR=1.34, P<0.01). Waist-to-height ratio and adipocyte volume were most strongly associated with HOMA-IR (multivariable linear regression: R2=0.656, P<0.001). After adjustment for BMI/ethnicity, women with IGM had increased serum adipocyte fatty acid-binding protein, weight gain after index pregnancy, and a lower proportion of fat-free mass. These factors, together with high BMI, abdominal fat distribution, and enlarged adipocytes, may increase the risk of progression to T2DM after GDM.
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| 4. |
- Andersson, Anderz, 1953-, et al.
(författare)
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Arbetsrätt
- 2021. - 7
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med den här boken är att ge läsaren grundläggande kunskaper i arbetsrätt och den svenska modellen. I fokus för framställningen står den arbetsrättsliga lagstiftningens framväxt, arbetsmarknadens parter, medbestämmande, anställningsskydd, arbetsmiljö och skydd mot diskriminering. Andra områden som behandlas är arbetstidsregleringen och ledighetslagstiftningen. Vidare behandlas EU-arbetsrättens inverkan på den svenska lagstiftningen.
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| 9. |
- Andersson, Staffan, 1959, et al.
(författare)
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Effects of egg yolk testosterone on growth and immunity in a precocial bird
- 2004
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Ingår i: Journal of Evolutionary Biology. - : Wiley. - 1010-061X. ; 17:3, s. 501-505
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Tidskriftsartikel (refereegranskat)abstract
- In oviparous vertebrates, maternal steroid allocation to eggs can have important fitness consequences for the offspring. However, elevated testosterone levels are not only associated with beneficial postnatal effects, such as enhanced growth and high social status, but may also entail costs by suppressing the immune system. In this study, testosterone levels in eggs of Chinese painted quail (Coturnix chinensis) were experimentally manipulated to evaluate its effects on growth and immunocompetence. Testosterone did not affect embryonic development, body size or growth during the first 20 days. However, elevated testosterone levels during embryonic development were immunosuppressive for chicks with inherently higher growth rate. Adaptive scenarios where only beneficial effects of increased testosterone levels are considered may therefore need to be re-evaluated.
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