In vitro effect of copper treatments on mitogenic response and superoxide dismutase expression of lead exposed leukocytes from periparturient dairy cows oleh MUNEENDRA KUMAR, HARJIT KAUR, BHUPENDRA TULSIDAS PHONDBA, VEENA MANI, NEELAM GUPTA, AMRISH KUMAR TYAGI, RAJU KUSHWAHA, GULAB CHANDRA