Genomic Instability and Cyto-Genotoxic Damage in Animal Species

Genomic instability is a condition that may be associated with carcinogenesis and/or physiological disorders when genetic lesions are not repaired. Besides, wild, captive, and domesticated vertebrates are exposed to xenobiotics, leading to health disorders due to cytogenotoxicity. This chapter provides an overview of tests to assess cytogenotoxicity based on micronuclei (MNi) formation. Bone marrow micronuclei test (BmMNt), peripheral blood erythrocyte micronuclei test (PBMNt), and lymphocyte cytokinesis blocking micronuclei assay (CBMN) are discussed. The most illustrative studies of these techniques applied in different vertebrates of veterinary interest are described. The values of spontaneous basal micronuclei in captive, experimental, and farm animals (rodents, hamsters, pigs, goats, cattle, horses, fish) are summarized. In addition, a flow cytometry technique is presented to reduce the time taken to record MNi and other cellular abnormalities. Flow cytometry is helpful to analyze some indicators of genomic instability, such as cell death processes and stages (necrosis, apoptosis) and to efficiently evaluate some biomarkers of genotoxicity like MNi in BmMNt, PBMNt, and CBMN. The intention is to provide veterinary professionals with techniques to assess and interpret cytogenotoxicity biomarkers to anticipate therapeutic management in animals at risk of carcinogenesis or other degenerative diseases.

Genotoxicity and Histopathology Effects of Melissa officinalis Aqueous Extract on the Blood and Vital Tissues of Oncorhynchus mykiss Fish

Background: This study was conducted to investigate both the genotoxicity effects of M. officinalis aqueous extract on blood cells and the pathologic changes in the renal, cardiac and splenic tissues of Oncorhynchus mykiss. Methods: 300 fish (Oncorhynchus mykiss) were divided randomly into three groups (N=100 each), consisting of group, 1 (control), and groups 2 and 3 (experimental), which received 450 mg/kg and 1350 mg/kg of body weight the aqueous extract of M. officinalis, respectively. The fish were fed for 30 days, with the experimental groups given three treatments. Micronuclei test and comet assay were used to identify the histopathological damages, simultaneously. Results: We found significantly more micronuclei (33%) in erythrocytes of group 3 than those in group 2 (5%; p<0.05). Similarly, the results of comet assay were consistent with those obtained for the micronuclei test. The recorded DNA damages to erythrocytes was significantly higher in group 3 (35.75%) compared to that for group 2 (7.15%; p<0.05). The pathologic findings in the spleen, kidneys and heart tissues together with those obtained from the micronuclei test and comet assay confirmed the tissue and DNA damages after exposure to the extract. Abundant and severe cystic and atrophic glomeruli, renal tubular degeneration, hemorrhage and focal lymphocytic inflammation in heart, and increased melanomacrophage centers in the kidneys and spleen were observed at significantly higher frequency in group 3 than those in group 2 (p<0.05). Conclusion: The findings of this study demonstrated that the extract of M. officinalis at doses higher than 450 mg/kg per body weight caused toxic effects with severe tissue and DNA damages in O. mykiss fish.