Zebrafish

One of the paradoxes of life on this planet is that the molecule that sustains aerobic life, oxygen is not only fundamentally essential for energy metabolism and respiration, but has been implicated in many diseases and degenerative conditions. In the sequential univalent process by which O2 undergoes reduction, several reactive intermediates (like superoxide radical, singlet oxygen, hydro-peroxyl radical etc.) are formed and these are collectively termed as the reactive oxygen species (ROS). The etiology or development of various diseases involves oxidative stress, a condition where the ROS produced by aerobic metabolism are insufficiently buffered by cell or tissue antioxidant defenses.

Increase in application of nanoparticles in improving

Zebrafish is a good model system and used as a test organism due to similarities in development and cellular composition of major organ systems (Schoenebeck and Yelon, 2007)(Rubin, 2007)(Gupta and Mullins, 2010)(Drummond, 2005) with that of humans. These similarities in organ physiology between zebrafish and other vertebrates also make this a good model system to test various components with potential health benefits for humans. During embryogenesis, their small size, rapid development, optical clarity, ease of care, and ability to obtain large numbers (Westerfield, 2007), make zebrafish an attractive model for rapid screening of developmental and toxicological effects from nanoparticle

Co-treatment of the embryos with CeO-NP and H2O2:Instead of pretreatment, when development of embryos were allowed in presence of both H2O2 and CeONP, only 5µM CeONP was sufficient to completely neutralize the lethal effect of H2O2 (fig. 5.4 B).Thus, both pre- and co-treatment of zebrafish embryos with nano-ceria made them able to survive under huge oxidative stress created by H2O2; co-treatment was more effective, as it required much less amount of CeONP (5µM) for suppressing the deleterious effect of H2O2. Figure 5.4: Reversal of H2O2-exposed embryo killing by treatment with CeONP. A: Pre-treatment; B: Co-treatment.

5.2.4 Reversal of H2O2-mediated malformation of embryos and larvae caused by CeONPs:

Although fig. 5.3 shows that at a concentration below 3.2mM of H2O2¬, embryonic development to larvae appeared to remain unaffected, however the hatched larvae failed to develop normal morphology with various developemental malformations viz., pericardial edema, yolk sac edema, tail and head malformation (fig. 5.5). The incidence of morphological deformities from high to low probability regions was observed as: pericardia > yolk sac > tail > head. Figure 5.5: Different types of morfological deformities generated in embryos in by H2O2¬ treatment.

No such H2O2-mediatedmorphological deformities were observed in larvae hatced out from CeONP pre-treated or co-treated embryos (fig.