α-MSH in fish. Functions in stress responses and skin colour change

Contains fulltext : 26955_alphinfi.pdf (publisher's version ) (Open Access)Radboud University Nijmegen, Animal Ecology and Ec, 07 juli 2005Promotores : Wendelaar Bonga, S.E., Flik, G.136 p

α-MSH, the melanocortin-1 receptor and background adaptation in the Mozambique tilapia, Oreochromis mossambicus

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In vitro evidence that cortisol directly modulates stress-related responses in the skin epidermis of the rainbow trout (Oncorhynchus mykiss Walbaum)

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The host-parasite relationship between the rainbow trout (Oncorhynchus mykiss) and the ectoparasite Argulus foliaceus (Crustacea: Branchiura): epithelial mucous cell response, cortisol and factors which may influence parasite establishment

The effects of short-term infection with the branchurian crustacean ectoparasite Argulus foliaceus, and the fish stress hormone cortisol (which is reported to stimulate mucus discharge), were studied on the mucous cell population of the head skin of rainbow trout (Oncorhynchus mykiss). Argulus infection did not raise plasma cortisol significantly and had no effect on the number of epidermal mucous cells in the head skin. Cortisol was administered twice to groups of trout via the food, significantly elevating circulating plasma cortisol at 24 h post feeding without affecting numbers of mucous cells, and increasing the numbers of vesicles in the upper cells of the epidermis. Subsequent infection with the parasite (6 Argulus f/fish) did not affect either plasma cortisol or total numbers of mucous cells at 48 h post-infection with the parasite, but led to a significantly lower parasite infestation per fish in the cortisol-administered groups. A 24 h culture system was used to expose pieces of trout skin to 50 ng/ml cortisol in vitro to investigate whether cortisol alone would stimulate reductions in mucous cell numbers. These were unaffected by the addition of cortisol. The in vivo and in vitro results are discussed in relation to the current understanding of crustacean host-parasite interactions

High groundwater nitrate concentrations inhibit eutrophication of sulphate-rich freshwater wetlands

Contains fulltext : 60491.pdf (publisher's version ) (Closed access)During the last 60 years, pollution of the groundwater with NO3- has greatly increased in many parts of Europe, as a consequence of excessive use of manure and synthetic fertilisers. Monitoring of groundwater-fed wetlands indicated that sediments with high NO3- concentrations had the lowest Fe and PO43- concentrations in the pore water. A comparison of two restored open water fens, differing in NO3- supply via the groundwater, indicated that the redox potential and the sulphate (SO42-) reduction rate were lower when the groundwater contained not only SO42- but also high NO3- concentrations. The lower SO42- reduction rates in the NO3--rich open water fen were associated with lower PO43- concentrations and the presence of plant species characteristic of clear water. In contrast, the higher SO42- reduction rates in the NO3--poor open water fen were associated with very high PO43- concentrations and massive development of plant species characteristic of eutrophic environments. Investigations at NO3--rich seepage sites in black alder carrs , showed that high NO3- concentrations in the pore water caused chlorosis in the alder carr vegetation due to lower availability of Fe in the pore water and less Fe uptake by the plants. Experimental desiccation of sediments proved that the NO3--rich seepage sites contained no oxidisable FeSx, contrary to NO3--poor locations, which became acidified and mobilised extremely high amounts of SO42- due to FeSx oxidation. A laboratory experiment showed that NO3- addition to sediments led to reduced release of Fe and S-2(-) and increased release of SO42-, very likely due to the oxidation of reduced Fe and S compounds. Overall, the results confirmed that NO3- is an energetically more favourable electron acceptor in anaerobic sediments than Fe and SO2- and that high NO3- loads function as a redox buffer, preventing reduction of Fe and SO42-. Limited SO42- reduction prevents S-2(-)-mediated mobilisation of PO43- from Fe-PO43- complexes. At a higher redox potential, reduced Fe, including FeSx, was oxidised, increasing the content of Fe(III) capable of binding PO43-. This prevented increased PO43- availability and the concomitant massive development of plant species characteristic of eutrophic environments

The acute stress response of red porgy, Pagrus pagrus, kept on a red or white background

Contains fulltext : 32297.pdf (publisher's version ) (Closed access)The skin colour of red porgy, Pagrus pagrus, can be modified by exposure to different background colours. Red and white background colours brighten the dark skin colour that develops under common culture conditions in red porgy. To assess whether skin colour is also modified by aquaculture related handling stress, we subjected red porgy to 5min of netting stress combined with air exposure. Fish kept on a white background have: (1) a lighter skin colour, which is not influenced by an acute stressor, (2) a less saturated red colour, which significantly decreases 24h post-handling, and (3) a similar hue as fish kept on a red background. The first plasma parameters to rise after application of the stressor are cortisol, lactate and Na(+); then, glucose levels rose. Other plasma ions (Ca(2+), Cl(-), K(+)) were not affected up to 2h post-stressor, but had decreased at 8 and 24h after handling. Plasma pH decreased over the first 2h post-handling, indicative of plasma acidosis upon air exposure. The acidosis then coincided with increases in plasma lactate levels. As alphaMSH levels were not significantly affected by the stressor while cortisol levels showed a five to tenfold increase, we suggest that following acute stress in red porgy, plasma cortisol release is controlled by ACTH, perhaps in combination with a sympathic stimulation

Effects of infection with the ectoparasite Argulus japonicus (Thiele) and administration of cortisol on cellular proliferation and apoptosis in the epidermis of common carp, Cyprinus carpio L., skin

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