 ProShares UltraPro Short SP 500 NYSEARCA:SPXU shares were down 7.8 during mid-day trading on Wednesday . The company traded as low as 14.67 and last traded at 14.94, approximately 54,152,003 shares were traded during mid-day trading. An increase of 114 from the average daily volume of 25,354,898 shares. The stock had previously closed at 16.20. ... 