Effects of pyrimidine on cellular and neuronal arrangement, oxidative stress and energy content in the brain of the freshwater catfish, Heteropneustes fossilis.

Fish are facing compromised health with mass mortality due to the decreased water quality of aquatic bodies. The brain, a complex body organ that controls whole body physiology, is influenced first by any kind of water fluctuations, and by keeping it relaxed and nourished, fish health can be improved. Among freshwater fish, catfish Heteropneustes fossilis has importance not only as a rich nutrient source but also due to medicinal significance. This study evaluated the impact of pyrimidine, a well-known organic compound with several therapeutic properties, on the cerebral health of the freshwater catfish H. fossilis as a bioremediation of aquatic environmental threats. In experiments, to get an effective concentration of pyrimidine, fish were incubated with different doses of pyrimidine (10 fg/mL-1 mg/mL) for 24 h, and brain histotexture and fish survival were recorded. As per the results of the previous experiment, an effective concentration of pyrimidine (10 pg/mL) was given for different durations (1-, 5- and 21-day incubation with pyrimidine and recovery; after 21-day treatment in only water for 7 days) along with the control group. Results exhibited that the level of cerebral antioxidant enzymes (catalase, superoxide dismutase, peroxidase) and lipid peroxidation were significantly lower, and macromolecules (carbohydrate, protein and lipid) were increased in pyrimidine-treated fish with duration of pyrimidine treatment as compared to the control group. Histo-neurological analysis of the brain with haematoxylin-eosin and cresyl violet revealed that an effective, nonlethal concentration of pyrimidine supported overall neuronal health without any histopathological changes. However, in the recovery experimental group, results showed reverting of pyrimidine induced positive changes in antioxidative enzyme and energy biomolecule levels, supporting the non-bio-accumulative nature of pyrimidine. However, microphotographs revealed that the neuronal quantity (cresyl violet) and cellular histotexture (haematoxylin-eosin) improvement due to pyrimidine were sustained in the recovery group. The results of this study suggested that effective concentration of pyrimidine improved the brain health of H. fossilis in a duration-dependent manner compared to control fish due to increased metabolism by upregulating energy macromolecule and cellular-neuronal texture along with downregulation of antioxidative stress.