In the present study, fish were exposed to sub-lethal doses of CuONPs (68.92 ± 3.49 nm) (10 mg/L, 20 mg/L, and 50 mg/L) for a long exposure period (25 days). Compared to the control group (0.0 mg/L CuONPs), a significant dose-dependent elevation in blood urea and creatinine values, serum alanine transaminase, aspartate transaminase, and alkaline phosphatase enzyme activities were evident in CuONPs-exposed groups (p < 0.05). Fish exposure to 50 mg/L CuONPs significantly upregulated the transcription of pro-inflammatory cytokines (tumor necrosis factor-alpha, interleukin-1beta, interleukin 12, and interleukin 8), heat shock protein 70, apoptosis-related gene (caspase 3), and oxidative stress-related (superoxide dismutase, catalase, and glutathione peroxidase) genes in liver and gills of the exposed fish in comparison with those in the control group (p < 0.05). Moreover, varying histopathological injuries were noticed in the hepatopancreatic tissues, posterior kidneys, and gills of fish groups correlated to the tested exposure dose of CuONPs. In summary, our results provide new insights and helpful information for better understanding the mechanisms of CuONPs toxicity in Nile tilapia at hematological, molecular levels, and tissue levels.
The current investigation assessed the impacts of sub-lethal concentrations of silicon dioxide nanoparticles (SiO2NPs) on hepato-renal functions, histopathological characteristics, and gene transcription in gills and liver of Nile tilapia juveniles. Fish were exposed to 20, 40, and 100 mg/L of SiO2NPs for 3 weeks. Pairwise comparisons with the control group showed a significant dose-dependent elevation in serum ALP, ALT, and AST enzyme activities as well as blood urea and creatinine levels in SiO2NP-intoxicated groups. Exposure to 100 mg/L SiO2NPs significantly upregulated expression of HSP70, TNF-α, IL-1β, and IL-8 genes in the gills as compared to the control group. Moreover, exposure to 100 mg/L SiO2NPs significantly upregulated the expression SOD, HSP70, IL-1β, IL-8, and TNF-α genes in the hepatic tissues as compared to the control group. Exposure of fish to 20 mg SiO2NPs/L significantly increased the mRNA expression levels of IL-12 in both the gills and liver tissues. Notably, all tested SiO2NP concentrations significantly upregulated the transcription of CASP3 gene in gills and liver of Nile tilapia as compared to the control group. Interestingly, varying histopathological alterations in renal, hepatopancreatic, and branchial tissues were observed to be correlated to the tested SiO2NP concentrations. In conclusion, our results provide additional information on the toxic impacts of SiO2NPs in Nile tilapia at the hematological, tissue, and molecular levels.
Streptococcus agalactiae has been described as one of the most serious bacterial diseases in tilapia culture. This study investigated the isolation and characterization of Streptococcus agalactiae from a condition of mass mortality in farmed Oreochromis niloticus at Baltim region, Kafr El-Sheikh governorate, Egypt during the summer of 2019, and the effectiveness of locally prepared bacterin for prevention of streptococcal disease. Infected fish showed corneal opacity, congestion of spleen, liver, and kidney, the abdominal space filled with watery and bloody ascites, and light-colored nodules on the kidneys, spleen, or liver. Water qualities were measured parallel to the fish sample. S. agalactiae isolates were identified by phenotypic and biochemical VITEK II methods. Ampicillin, Colistin sulfate, would appear as the best antibacterial agents to use in the treatment. The relative level of protection value was 70% in Oreochromis niloticus challenged with a virulent strain of S. agalactiae (10 7 CFU /1 ml) and vaccinated with locally prepared killed bacterin. Histopathological investigations revealed congested blood vessels in all organ's specimens examined, inflammatory cells infiltration, degenerative changes, different stages of necrosis of the liver, and generalized meningoencephalitis of the brain. The current study recommended that S. agalactia induced many problems in tilapia culture in presence of bad water quality during the summer season, and the vaccination program gives good results and high protection which may be a useful method for the prevention and control of streptococcal infection.
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