The present study is an attempt to elucidate the involvement of insulin-like growth factor (IGF1) in the differentiation and growth of primary follicles in ovarian explant cultures of zebrafish. Ovaries from adult females were cultured in triplicate sets/treatment group for 15 days at 22° in the laboratory. Culture medium was supplemented with either insulin (1 ng/mL) or IGF1 (1 ng/mL) or insulin + IGF1 (Experiment 1) or 0.1 or 1.0 or 10 ng/mL of IGF1 (Experiment 2). Ovaries cultured in medium alone served as controls and those fixed at the beginning of the culture as initial controls. Experiments were repeated. On the 16th day ovarian explants were fixed in Bouin's fluid and processed for paraffin embedding, sections (3 μ m) were cut and stained with hematoxylin-eosin. Follicles were classified into 6 stages and atretic follicles (AF). Previtellogenic, vitellogenic and total follicle number was calculated. At the start of the culture, ovaries contained all stages of growing and degenerating follicles. In cultured control ovaries, vitellogenic follicles underwent atresia, while, primary follicles remained unaffected. Insulin or insulin + IGF1 treated ovaries did not differ significantly while IGF1 exposed ovarian explants had greater (P less than 0.05) number of primary follicles compared to controls. IGF1 also caused an increase in the number and growth of primary follicles in a dose dependent manner although; cultures were not supplemented with gonadotrophic hormones. Results suggest that locally derived intra-ovarian IGF1 may have a role in the differentiation and growth of primary follicles in zebrafish ovary.

Novaluron is an insect growth regulator (IGR) used against fruit-borers and domestic pests. In this study, effects of different concentrations (0.5, 0.75, 1.0, 1.5 microg l(-1)) of novaluron on the tail regeneration, limb development and metamorphosis were examined in Bufo melanostictus. Thyroxine (1.0, 2.0, 3.5, 5.0 microg l(-1)), which promotes amphibian development/metamorphosis, and vitamin A (5, 20, 40, 60 IU l(-1)), which disrupts development and induce polymelia, were used for comparison. Bufo melanostictus tadpoles were raised in the laboratory from eggs collected around Dharwad in August 2007. The tail of tadpoles was amputated at limb-bud stage under ether anesthesia. Ten tadpoles were exposed to each concentration of chemicals in triplicate for 5 days and then reared in conditioned water. Tadpoles were fed on boiled spinach. In controls (tadpoles exposed to ringer solution), the tail regenerated on the 5th day, hind-limbs and fore-limbs appeared on days 15 and 24, respectively; metamorphosis was complete on the 30th day. In 1 and 2 microg l(-1) thyroxine exposed tadpoles, regeneration of tail, development of limbs and metamorphosis were preponed to the 4th, 7th, 11th and 23rd day respectively. Exposure to vitamin A resulted in the regeneration of laterally drooped tails, delay in limb development and arrest of metamorphosis in all the concentrations used. Novaluron at lower dose (0.5 microg l(-1)) was not effective, but at 0.75 microg and higher concentrations it elicited results comparable to those of vitamin A. The study indicates that novaluron interferes with amphibian development if found as contaminant in the water bodies where amphibians live and reproduce.