Citrix Systems shares tumble 19% at $74 to lead S&P 500 decliners at the open

Apple shares on track for best daily gain in 6 months on earnings

Wal-Mart shares slip 1% at $66.10 to lead Apple decliners in early trade

Apple contributes more than 40 points to Dow’s early advance

Under Armour price target cut to $20 from $44 at Canaccord Genuity

Nasdaq Composite Index jumps 0.7% to 5,653, bolstered by upbeat Apple results

Under Armour downgraded to hold from buy at Canaccord Genuity