Comparison of change in body weight between (A) male and (B) female mice intraperitoneally injected for 14 days either with 20 mg or 50 mg/ml saline/ Kg body weight of NiO NPs or with saline solution. Data is expressed as mean ± standard error of mean. P values represent the outcome of two samples t-test calculated between a specific NiO NPs treatment and saline group for each treatment day.