Factors Affecting Antioxidant Response in Fish from a Long-term Mercury-Contaminated Reservoir.

The objective of this work was to evaluate antioxidant defence and oxidative damage in organs (liver, gills, kidney, and brain) of five fish species (Aspius aspius, Esox lucius, Sander lucioperca, Abramis brama, Rutilus rutilus) from the long-term mercury-contaminated Skalka Reservoir in the Czech Republic. Special emphasis was placed on a comprehensive assessment of the factors that may affect the antioxidant response to mercury in fish. Antioxidant enzymes (glutathione reductase, glutathione peroxidase, and glutathione-S-transferase) did not significantly respond to mercury contamination. Levels of the analysed enzymes and oxidative damage to lipids were predominantly determined by a separate organ factor or species factor, or by the combination of both (p < 0.001). Levels of total glutathione and the reduced/oxidized glutathione ratio were influenced by mercury contamination in combination with their specific organ distribution (p < 0.001). Our results suggest that species and type of organ alone or in combination are more important factors than chronic exposure to mercury contamination with respect to effects on antioxidant defence in fish under field conditions. Our findings suggest that the main antioxidant defensive mechanism in fish from the studied long-term mercury contaminated site was the inter-tissue distribution of glutathione.

Effects of subchronic nitrite exposure on rainbow trout (Oncorhynchus mykiss).

Subchronic toxicity of nitrite in rainbow trout (Oncorhynchus mykiss; mean mass ± S.D., 18.9 ± 1.3g) was assessed in a 28-day trial. The influence of nitrite on fish mortality, growth rate, haematology, blood biochemistry, and gill histology was observed. Survival was not affected by exposures up to 1 mg l(-1) NO(2)(-) (at 10 mg l(-1) Cl(-)). On the basis of growth rate inhibition data, the values of NOEC (28 d LC(0)) and LOEC (28 d LC(10)) were estimated at 0.01 and 0.2 mg l(-1) NO(2)(-), respectively. At 0.01 mg l(-1) NO(2)(-) (the lowest concentration tested), there was segmental hyperplasia of the respiratory epithelium of secondary lamellae and elevated glucose and decreased potassium. Elevated nitrite concentrations were found in blood plasma of fish exposed to concentrations of 1.0 mg l(-1) NO(2)(-) and higher, and in muscle tissue at the highest concentration 3.0 mg l(-1) NO(2)(-). Plasma and muscle nitrite levels were lower than those in the ambient water in all experimental groups.

Stress in broilers resulting from shackling.

The aim of this study was to assess stress response of broilers to different periods of shackling. Stress effects of shackling were monitored in a group of male Ross 308 broilers (total number: 400) aged 42 d. Three shackling treatments were used in our experiment: shackling of broilers for 30 s (group T30), 60 s (group T60), and 120 s (group T120). Corticosterone plasma concentration was elevated in T60 broilers (P<0.05) and in T120 birds (P<0.01); glucose plasma concentration was increased (P<0.05) in both T60 and T120 broilers when compared with nonshackled control. Lactate concentrations increased in T30 birds (P<0.05) and in both T60 and T120 birds (P<0.01). Furthermore, T120 broilers exhibited an increase (P<0.01) in heterophil counts and heterophil:lymphocyte ratio. Duration of tonic immobility was increased (P<0.05) in T60 and T120 broilers. Number of attempts to induce tonic immobility decreased (P<0.01) in all test groups (T30, T60, T120). Duration of shackling period was positively correlated (P<0.001) with corticosterone, glucose and lactate level, tonic immobility duration, and heterophil:lymphocyte ratio. The number of inductions was negatively correlated (P<0.001) with duration of the shackling period. According to the results of our study, the act of shackling is a considerable traumatic procedure for broilers, and its stress effect is markedly dependent on duration of shackling period that the broiler chickens experience. It follows from our study that the optimal shackling period should be less than 60 s.

Effects of deltamethrin on rainbow trout (Oncorhynchus mykiss).

The aim of this study was to assess the effect of deltamethrin on rainbow trout (Oncorhynchus mykiss). Control and experimental group of fish were exposed to Decis EW 50 pesticide preparation (active substance 50g/l of deltamethrin). The acute semistatical toxicity test lasting 96h was performed on rainbow trout juveniles. The 96hLC(50) value of Decis EW 50 was 0.02mg/l. Examination of haematological and biochemical profile and histological tissue examination was performed on 1-2-year-old rainbow trout after 96h of exposure to Decis EW 50 in a concentration of 0.02mg/l. The experimental group showed significantly lower values (p<0.05) of plasma glucose, alanine aminotransferase, cholinesterase and significantly higher (p<0.05) values of erythrocyte count, haemoglobin content, haematocrit and plasma total protein, albumins, ammonia, aspartate aminotransferase, creatinekinase and calcium compared to the control group. The deltamethrin-based Decis EW 50 pesticide preparation was classified among substances strongly toxic for fish.