The markets turned negative during the midday with the Dow falling 52 points to 12,065 as European debt concerns continued to weigh on investors. Nasdaq lost 9 points to 2738.

On the upside

Laboratory Corp. of America (NYSE: LH) will pay a premium of approximately $241 million in cash to acquire Medtox Scientific (Nasdaq: MTOX).

Chesapeake Energy (NYSE: CHK) will replace four of its board members.

Credo Petroleum (Nasdaq: CRED) agreed to be acquired by Forestar Group (NYSE: FOR) for a premium of approximately $146 million in cash.

On the downside

Shares of Hovnanian Enterprises (NYSE: HOV) continued falling following a disappointing pending home sales report last week.

A Seeking Alpha contributor recommended shorting Frontline (NYSE: FRO).

Delta's (NYSE: DAL) disappointing May passenger unit revenue report weighed down shares of US Airways (NYSE: LCC) and United Continental (NYSE: UAL).

In the broad market, declining issues outpaced advancers by a margin of more than 5 to 2 on the NYSE and by 3 to 2 on Nasdaq. The Russell 2000 which tracks small cap stocks lost 5 points to 731.