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Hormones of the adrenal or interrenal axis and stress situations which induce elevated glucocorticoid plasma levels (e.g. handling and starvation), inhibit thyroid function in growing and adult vertebrates. However, data indicate that during foetal and embryonic development (mammals and birds) or during larval growth and metamorphosis (fish and amphibians),(More)
Two rapeseed (Brassica napus) meals, RM1 and RM2, with two levels of glucosinolates (GLS; 5 and 41 mumol/g DM respectively) were incorporated at the levels of 300 and 500 g/kg of the diets of juvenile rainbow trout (Oncorhynchus mykiss) in replacement of fish meal, and compared with a fish-meal-based diet. A decrease in the digestibility of the DM, protein,(More)
Two rapeseed meals (RM1 and RM2), containing glucosinolates at a concentration of 26 and 40 micromol/g, respectively, were incorporated at increasing levels (10, 20, and 30% for RM1 and 30 and 50% for RM2) in diets of juvenile rainbow trout. Disturbances in the thyroid axis appeared after 14 days of feeding (with a dietary incorporation level of 10%). The(More)
In this study, intravenous injection of several doses of porcine follicle stimulating hormone (pFSH: 0.002, 0.01, 0.05, and 0.5 micrograms/g body wt), bovine TSH (bTSH: 0.5 micrograms/g body wt), and ovine growth hormone (oGH: 0.04, 0.02, and 0.4 microgram/g body wt) stimulated an increase in plasma thyroxine (T4) and reverse triiodothyronine (rT3) in(More)
The presence of outer ring deiodinating (ORD) and inner ring deiodinating (IRD) activities was investigated in different tissues of Oreochromis niloticus (Nile tilapia), Clarias gariepinus (African catfish), Oncorhynchus mykiss (rainbow trout) and halmus maximus (turbot). High-Km rT3 ORD is present in the kidney of most of the fishes studied, except in(More)
Radioimmunoassay of 3,5,3'-triiodothyronine (T3) and thyroxine (T4) in the thyroidal region of mature male Oreochromis niloticus revealed stores of T4 but negligible levels of T3, yielding a very low T3/T4 ratio (0.3%). 5'-Deiodination (5-D) of T4 into T3 was examined in liver and kidney homogenates in vitro by radioimmunoassay of T3 with T4 as substrate.(More)
Fasting and refeeding have considerable effects on thyroid hormone metabolism. In tilapia (Oreochromis niloticus), fasting results in lower plasma T3 and T4 concentrations when compared to the ad libitum fed animals. This is accompanied by a decrease in hepatic type II (D2) and in brain and gill type III (D3) activity. No changes in kidney type I (D1)(More)
In tilapia, there is a sex-related growth difference between males and females. This study tried to detect any correlation between the somatic growth and the plasma endocrine status. For this, individually marked (Floytags) male and female tilapia (BW 82 +/- 10 g) were either starved or fed on different daily food rations (1, 2, or 3% of the biomass) during(More)
The presence of iodothyronine deiodinases was investigated in the different tissues of blue tilapia (Oreochromis aureus), and their biochemical properties were compared with those of mammalian deiodinases. High-Km rT3 outer ring deiodination (ORD) was observed in tilapia kidney, low-Km T4 ORD in liver, and low-Km T3 inner ring deiodination (IRD) in brain(More)