Developmental toxicity of two different classes of commercial formulations of insecticides was studied by in ovo treatment of fertilized Rhode Island Red eggs. The first one was a combination of chlorpyrifos and cypermethrin and the second one was spinosad, a fermentation product of soil bacterium, Actinomycetes. In this study, the combination pesticide and spinosad of different concentrations were administered as a single dose in ovo in volumes of 50 μL per each egg on day "0" of incubation. Embryonic growth and development, morphological and skeletal malformations, and hatchability were assessed. The combination insecticide induced explicit alterations in the embryonic growth and development and resulted in malformations particularly to the axial and appendicular skeletal structures, whereas the changes were trivial in case of the spinosad exposure.

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Epimorphic regeneration in vertebrates involves the restoration of lost tissue or organs through the formation of a regeneration blastema and occurs through a complex interaction of a number of molecular signaling pathways. Of the many effectors of successful tail regeneration in the lizard Hemidactylus flaviviridis, one crucial pathway is the cyclooxygenase-2 (COX-2) mediated PGE 2 signaling pathway. The current study was aimed at understanding whether COX-2 signaling plays any role in the expression of Wnt/b-Catenin signaling components during regenerative outgrowth in H. flaviviridis. Etoricoxib-selective inhibitor of the inducible isoform of COX-2-was administered to lizards orally. We tested the expression of b-Catenin during wound epidermis and blastema stages in the regenerating tail and found a reduction in its expression in response to drug treatment. Further, it was observed that the expression of canonical Wnt ligands was greatly altered due to COX-2 inhibition. Our results provide evidence of a cross-talk between the COX-2 induced PGE 2 pathway and Wnt/b-Catenin signaling in the regenerating lizard tail. An understanding of the interaction among various signaling pathways will help elucidate the mechanism underlying epimorphosis in lizards, the only amniotes capable of appendage regeneration.

Caudal fin regeneration in sailfin molly, Poecilia latipinna (Lesueur 1821) involves an initial wound healing stage, followed by blastema that is formed of fast proliferating cells. In order to replicate the lost fin, correct differentiation of the blastemal cells into various tissues is the prime essence. Among the molecular signals governing proper differentiation of blastemal cells, members of the bone morphogenetic protein (BMP) family are crucial. Herein, we investigated the specific effects of inhibition of BMP signaling using LDN193189 on skeletal and connective tissue formation in the regenerating tail fin of P. latipinna during early differentiation phase. It was observed that BMP inhibition leads to reduction in the length of regeneration, which can be correlated with compromised proliferation of blastemal cells. Decreased expression of cell proliferation marker like pcna together with reduced BrdU positive cells consolidate the above observation. Further, histological analysis revealed stunted progression of skeletal tissues and this correlated with the reduced expression of sox9, runx2 and dlx5, Osc and Osn genes in response to BMP inhibition. Also, defective bone patterning was observed due to BMP inhibition, which was associated with diminished levels of shh, ptc-1, gli2 and other BMP ligands. Moreover, histochemical analysis revealed that collagen, one of the most prominent components of connective tissue, was formed below par in treated fin tissues which was subsequently confirmed by biochemical and transcript level analyses. Overall our results highlight the importance of the BMP pathway in proper differentiation of skeletal and connective tissues during the differentiation stage of regenerating caudal fin.

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