Volatility struck bourses in early afternoon trade as the key benchmark indices once again regained positive zone after sliding in negative zone in mid-morning trade. At 12:30 IST, the barometer index, the S&P BSE Sensex, was up 54.48 points or 0.15% at 36,372.81. The Nifty 50 index was up 18.95 points or 0.17% at 10,905.75. Shares of index heavyweight Reliance Industries rose. Most realty stocks gained.