Nasdaq Stock Market ( NDAQ) shares were up after the exchange took a more aggressive stance in its hostile $5.2 billion bid to buy the London Stock Exchange. Nasdaq told LSE shareholders that the value of their investment may fall sharply if the LSE continues to rebuff the offer. Nasdaq also threatened that it might sell off its 29% LSE stake in the face of rejection, which, it warned, would put pressure on the LSE's share price. Nasdaq was gaining 41 cents, or 1.2%, to $33.51. UnitedHealth Group ( UNH) gained after the Minnesota-based insurance giant reiterated its prior 2007 earnings estimates of between $4.14 billion and $4.16 billion on $79.5 billion in revenue. Analysts polled by Thomson Financial are looking for revenue of $78.5 billion. Shares were adding 76 cents, or 1.5%, to $53.31. Axis Capital Holdings ( AXS) rose after a Citigroup analyst upped the insurer's rating to hold from sell. Shares were climbing 28 cents, or 0.9%, to $32.73. CompuCredit ( CCRT) dropped after the Georgia-based lender lowered its fourth-quarter earnings forecast to 20% below its previous outlook of 50 cents a share. Analysts are seeking 51 cents a share. The company added that its 2007 outlook remains unaffected, but shares were losing $1.87, or 4.7%, to $37.55. NovaStar Financial ( NFI) tumbled after an analyst with JMP Securities downgraded the mortgage company to market-perform from outperform. Shares were down $1.35, or 5.4%, to $23.77.