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- Lennquist, Anna, 1978, et al.
(författare)
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Colour and melanophore function in rainbow trout after long term exposure to the new antifoulant medetomidine
- 2010
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Ingår i: Chemosphere. - : Elsevier BV. - 0045-6535 .- 1879-1298. ; 80:9, s. 1050-1055
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Tidskriftsartikel (refereegranskat)abstract
- Medetomidine is a new antifouling agent, and its effects in non-target aquatic organisms have been investigated. Earlier short-term studies in fish have shown a skin lightening response to medetomidine, but effects after chronic exposure have not been studied. In fish, the dark pigment melanin is contained within specialized cells, melanophores. Medetomidine binds to the melanophore α2-adrenoceptor, which stimulates pigment aggregation resulting in the light appearance. In the present study, rainbow trout (Oncorhynchus mykiss) was long-term exposed to 0.5 and 5.0 nM of medetomidine via water for 54 d. The fish were then photographed for paleness quantification and the images were analyzed using ImageJ analysis software. Additionally, scales were removed and used for in vitro function studies of the melanophores, monitoring the response to melanophore stimulating hormone (MSH) and subsequent medetomidine addition. The number of melanophores was also investigated. As a result of the medetomidine exposure, fish from the 5 nM treatment were significantly paler than control fish and the melanophores from these fishes were also more aggregated. Melanophores from all the treatments were functional, responding to MSH by dispersion and to subsequent medetomidine by aggregation. However, the results indicate a difference in sensitivity among treatments. The number of melanophores in the scales did not change significantly after long term exposure to medetomidine. These results suggest that the observed paleness may be reversible, even after chronic exposure.
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| 3. |
- Lennquist, Anna, 1978, et al.
(författare)
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Effects of medetomidine on hepatic EROD activity in three species of fish
- 2008
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Ingår i: Ecotoxicology and Environmental Safety. - : Elsevier BV. - 0147-6513. ; 69:1, s. 74-79
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Tidskriftsartikel (refereegranskat)abstract
- Medetomidine, an antifouling candidate, was investigated for its effects on cytochrome P4501A (CYP1A) activity in fish. Rainbow trout (Oncorhynchus mykiss), turbot (Psetta maxima), and Atlantic cod (Gadus morhua) were exposed to medetomidine either via i.p. injection (o5 mmol (1 mg)/kg) or via water (o50 nM). Enzyme activity was measured as ethoxyresorufin-O-deethylase (EROD) activity in liver microsomes. There was a small (2–7-fold) increase in EROD activity in rainbow trout. In turbot, EROD activity increased (4- fold) after injection, while a non-significant (50%) decrease was observed after water exposure. No effects on EROD activities were observed in Atlantic cod. In vitro inhibition studies of EROD activities in liver microsomes from all three species showed that medetomidine was a very potent CYP1A inhibitor. Thus, median inhibition values (IC50) were 35710nM for rainbow trout, 47717nM for turbot, and 111770nM for Atlantic cod. These observed effects suggest that medetomidine interferes with CYP1A-dependent metabolism of xenobiotics in these fish species.
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| 4. |
- Lennquist, Anna, 1978, et al.
(författare)
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Physiology and mRNA expression in rainbow trout (Oncorhynchus mykiss) after long-term exposure to the new antifoulant medetomidine.
- 2011
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Ingår i: Comparative biochemistry and physiology. Toxicology & pharmacology : CBP. - : Elsevier BV. - 1532-0456. ; 154:3, s. 234-41
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Tidskriftsartikel (refereegranskat)abstract
- Medetomidine is under evaluation for use as an antifouling agent, and its effects on non-target aquatic organisms are therefore of interest. In this study, rainbow trout was exposed to low (0.5 and 5.0nM) concentrations of medetomidine for up to 54days. Recently we have reported on effects on paleness and melanophore aggregation of medetomidine in these fish. Here, specific growth rates were investigated together with a broad set of physiological parameters including plasma levels of growth hormone (GH), insulin-like growth factor-I (IGF-I) and leptin, glucose and haemoglobin (Hb), hematocrit (Ht), condition factor, liver and heart somatic indexes (LSI, HSI). Hepatic enzyme activities of CYP1A (EROD activity), glutathione S-transferases (GST) and glutathione reductase (GR) were also measured. Additionally, hepatic mRNA expression was analysed through microarray and quantitative PCR in fish sampled after 31days of exposure. Medetomidine at both concentrations significantly lowered blood glucose levels and the higher concentration significantly reduced the LSI. The mRNA expression analysis revealed few differentially expressed genes in the liver and the false discovery rate was high. Taken together, the results suggest that medetomidine at investigated concentrations could interfere with carbohydrate metabolism of exposed fish but without any clear consequences for growth.
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| 5. |
- Lennquist, Anna, 1978, et al.
(författare)
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Responses in fish exposed to medetomidine, a new antifouling agent
- 2010
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Ingår i: Marine Environmental Research. - : Elsevier BV. - 0141-1136. ; 69
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Tidskriftsartikel (refereegranskat)abstract
- Medetomidine is being introduced as a new antifouling agent. As part of a large risk assessment campaign, we have studied responses to medetomidine in a number of fish species. The studied parameters include respiration, blood parameters, antioxidant enzymes, CYP1A, behaviour, pigmentation, reproduction and growth. The main observations from these studies are: 1. Body paleness at water concentrations in the range of 0.5-50 nM, depending on species. In addition, impaired adaptation to the background colour was shown in fry from turbot and lumpfish. In rainbow trout, desensitization of melanophores (pigment cells) occurred in fish exposed to medetomidine for 21 days, but a prolonged study (54 days exposure time), showed that the melanophores were well functioning and in addition that no apoptosis had occurred. 2. CYP1A activities, measured as EROD activities, were increased at medetomidine water concentrations from 0.5-5 nM in rainbow trout, Atlantic salmon, turbot and three-spined stickleback. However, investigations in vitro showed medetomidine to be a potent inhibitor of EROD activity. 3. In lumpfish and turbot fry, a decreased oxygen consumption and respiration rate was observed from 2 nM medetomidine. This effect was reversible to a large extent.
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