| 1. |
- Kling, Peter, 1968, et al.
(author)
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A homologous salmonid leptin radioimmunoassay indicates elevated plasma leptin levels during fasting of rainbow trout
- 2009
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In: General and Comparative Endocrinology. ; 162:3, s. 307-312
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Journal article (peer-reviewed)abstract
- The present study was conducted to establish a homologous radioimmunoassay (RIA) for quantifying plasma leptin (Lep) levels in salmonid species, and to study Lep levels in relation to nutritional status. A part of the Lep peptide, a 14 amino acid long sequence, identical between a Salmo and an Oncorhynchus species was synthesised. Polyclonal antibodies were raised in rabbit against this antigen and both were subsequently used in the development of a RIA protocol for assessing plasma Lep levels. The limit of detection of the assay was 0.3 nM, and intra- and interassay coefficient of variation (CV) were 8.4% and 13%, respectively. Apart from Atlantic salmon and rainbow trout, the assay exhibits measuring parallelism for a range of fish species, including arctic char, Atlantic cod and turbot, suggesting that the established RIA is useful for quantifying Lep levels in several fish species. The RIA indicates that Lep is found in salmonid plasma at levels of 0.5–5 nM, which is comparable with other peptide hormones, and well within the measuring range of the RIA. A study of fed and fasted rainbow trout showed elevated plasma Lep levels during fasting. In addition there was no correlation between Lep levels and condition factor. These data suggest that the relation between circulating Lep levels and energy status differs from that in mammals. While Lep is linked to energy balance, it may not act as an adiposity signal in salmonids, possibly pointing to functional divergence among ectothermic and endothermic vertebrates.
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| 2. |
- Kling, Peter, 1968, et al.
(author)
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The role of GH in lipid homeostasis, energy utilization and partitioning in rainbow trout: interactions with ghrelin, leptin and insulin-like growth factor I
- 2012
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In: General and Comparative Endocrinology. - : Elsevier BV. - 0016-6480. ; 175:1, s. 153-162
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Journal article (peer-reviewed)abstract
- The growth-promoting effects of in vivo growth hormone (GH) treatment were studied in relation to size and lipid content of energy stores including liver, mesentery, white muscle and belly flap in rainbow trout. In order to elucidate endocrine interactions and links to regulation of growth, adiposity and energy metabolism, plasma levels of GH, insulin-like growth factor I (IGF-I), leptin (Lep) and ghrelin, were assessed and correlated to growth and energy status. In addition tissue-specific expression of lepa1 mRNA was examined. Juvenile rainbow trout were implanted with sustained-release bovine GH implants and terminally sub-sampled at 1, 3 and 6 weeks. GH increased specific growth rate, reduced condition factor (CF) and increased feed conversion efficiency resulting in a redistribution of energy stores. Thus, GH decreased mesenteric (MSI) and liver somatic index (LSI). Lipid content of the belly flap increased following GH-treatment while liver and muscle lipid content decreased. Independent of GH substantial growth was accompanied by an increase in muscle lipids and a decrease in belly flap lipids. The data suggest that the belly flap may function as an energy buffering tissue during episodes of feeding and lean growth. Liver and muscle lipids were positively correlated to body weight, indicating a size-dependent change in adiposity. Hepatic lepa1 mRNA positively correlated to MSI and CF and its expression decreased following GH treatment, coinciding with decreased hepatic lipid content. Plasma Lep was positively correlated to MSI and belly flap lipid content, suggesting that Lep may communicate energy status. In summary, the observed GH tissue-specific effects on lipid metabolism in rainbow trout highlight the complex physiology of the energy reserves and their endocrine control.
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| 3. |
- Sundell, Kristina, 1959, et al.
(author)
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Intestinal absorption
- 2011
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In: Encyclopedia of Fish Physiology: From Genome to Environent. - London : Academic Press, an imprint of Elsevier. - 9780080923239 ; , s. 1311-1321
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Book chapter (peer-reviewed)abstract
- The fish intestine is the main site of absorption. The functional morphology and physiology of the intestinal epithelium have evolved to selectively absorb essential nutrients as well as water and ions from the ingested food and water, while preventing entrance of harmful substances. Membrane-bound transport and channel proteins together with endocytotic mechanisms ensure a well-controlled uptake. Being a multifunctional tissue, there is a constant balance between the different physiological tasks of the intestinal epithelium, and both internal and external factors can affect and control these events that are of fundamental importance for development, growth, and performance of the fish.
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