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Background: The production of secondary metabolites in different strains of microalgae varies and is likely dependent on environmental conditions. Consequently, the production of bioactive substances as secondary metabolites occurs in microalgae to aid their survival in adverse environmental conditions such as salinity stress. Objectives: The purpose of this study is to investigate the antibacterial activity of the methanolic extract of Spirulina platensis algae cultivated under different salinity stresses against Yersinia rukeri, Escherichia coli, Salmonella sp., and Vibrio cholerae. Methods: The broth microdilution method was used to evaluate the growth inhibitory activity of the extracts against Yersinia ruckeri, Salmonella sp., Escherichia coli, and Vibrio cholerae bacteria. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined by this method, and the diameter of the inhibition zone was assessed through the well diffusion method. Results: In the treatment with algae extract grown under 3.5 ppt salinity stress, the concentrations of 50 and 25 mg/mL extract showed the largest inhibition zone diameter against Salmonella sp. compared to other bacteria. Under 7 ppt salinity stress, all studied concentrations of algal extract exhibited a higher inhibition zone diameter against V. cholerae compared to other bacteria. The results of comparing different concentrations of algae extract between the two salinity stresses of 3.5 and 7 ppt for each bacterium showed a significant difference (P < 0.05). As salinity increased, the diameter of the inhibition zone also increased for all bacteria. Conclusions: Our results showed an increase in the antibacterial activity of the methanolic extract of Spirulina platensis with higher salinity stress levels. Therefore, cultivating Spirulina algae in salt water can be a cost-effective and suitable method to produce more secondary metabolites for use in the pharmaceutical industry. [ABSTRACT FROM AUTHOR]

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Background: Fish in aquatic environments are end consumers of the food chain and are widely used for the evolution effects of environmental pollution and their interactions in aquatic ecosystem. Objective: In the present study, common carp (Cyprinus carpio) fingerlings were selected to assess the potential risk and aquatic toxicity of meloxicam as a non‐steroidal anti‐inflammatory and a commonly used pharmaceutical drug. Methods: In order to evaluate meloxicam toxicological effect on haematological, antioxidant status, enzymological and histological parameters, based on its LC50 24 h acute toxicity (10.05 mg L−1), fish fingerlings were exposed to four doses of meloxicam including; 0 (control), 0.1 (low), 1 (medium) and 2 mg L−1 (high) under static bioassay method for 28 days. Results: The results showed that sublethal doses of meloxicam significantly decreased alanine aminotransferase, alkaline phosphatase, superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPX) levels in comparison with the control group after 28 days (p < 0.05). However, red blood cell, haematocrit, haemoglobin and malondialdehyde values in fish exposed to meloxicam significantly increased alongside its concentration (p < 0.05) more than the control group after 28 days. SOD, CAT and GPX mRNA expression levels in gill, liver, kidney and brain organ of fish under meloxicam treatment were significantly down‐regulated compared to the control group (p < 0.05). Histopathological assessment showed the increased vacuolation in hepatocytes in liver of fish exposure to medium and high doses of meloxicam. Conclusion: In conclusion, meloxicam induces oxidative stress in common carp which results a disruption of physiological and health status of this species based on our current findings. [ABSTRACT FROM AUTHOR]

The in vivo effect of 11‐ketotestosterone (11KT) on transcript levels of the gonadotropin receptors (fshr and lhr) and sex differentiation‐related genes (dmrt1 and foxl2) was examined in the ovaries of immature female beluga. For this purpose, six fish were treated with implants containing 2.5 mg 11KT and a placebo group of six females of the same age and gametogenic stage were given a blank implant. The implants were intraperitoneally inserted into 4‐year‐old females at the previtellogenic stage (mean body weight 5580 ± 165 g) and maintained under culture conditions for 8 weeks. Ovary samples for gene expression analysis of lhr, fshr, dmrt1 and foxl2 were collected by biopsy at 3 and 8 weeks post implantation. Diameters of oocytes increased in response to 11KT treatment, both at 3 and at 8 weeks post implantation, but no obvious changes were evident in cytology. Three weeks of 11KT treatment did not affect target gene expression, but a tendency for a time‐dependent decrease of lhr and dmrt1 mRNA levels was observed in both treatment and placebo groups. By 8 weeks of treatment, however, 11KT implants provoked the upregulation of fshr and foxl2 transcript levels. Furthermore, lhr and dmrt1 transcript abundances recovered by 8 weeks of exposure in both blank‐ and 11KT‐implanted beluga. These results suggest that 11KT, either directly or indirectly, may affect gametogenesis and regulate some key components of the reproductive axis in female beluga. [ABSTRACT FROM AUTHOR]