Earnings, analyst actions and a buyout new peppered health stock headlines on largely flat Thursday after losses earlier in the week.

Biotech company Invitrogen ( IVGN) said Thursday it will buy Applera Corp.'s scientific-instrument company Applied Biosystems ( ABI) in a $6.7 billion cash and stock deal. Invitrogen shares gave up 10.7% to $38.73, while Applied Biosystems climbed 5.3% to $34.16.

Invitrogen is a component of the Nasdaq biotechnology index, ended just above the flat line.

Elsewhere, China Medical ( CMED) rose 17.5% to $39.28. The company said that it earned $15 million, or 53 cents per American depositary share, in the recent quarter. It recorded an adjusted profit of 66 per ADS, vs. 44 cents in the year prior. Revenue increased to $40.6 million. Analysts expected $36.8 million, on average, according to Thomson-Reuters.

Looking ahead, China Medical guided to a profit of $2.87 to $2.96 a share, on revenue in a range of $169.7 million to $175.4 million. Analysts expected $2.55 a share on $161.9 million in revenue, on average.

Meanwhile, Chindex International ( CHDX), an American health-care company that provides services, equipment and products to the Chinese marketplace, sank 29.7% to $14.60. The company said revenue rose 40% to $34.6 million in the quarter ended March 31, but reported a loss of $2.7 million, or 20 cents a share, vs. a profit of $665,000, or 6 cents a share, the year prior. Chindex said the results were impacted by certain non-routine year-end adjustments as well as the interest charge related to the conversion of a JPMorgan convertible bond.

A few analyst actions in the health stocks: Citigroup analyst Lucy Lu downgrade BioMarin ( BMRN) to hold from buy and lowered her price target to $37 from $42, after surveying 26 treatment centers on Kuvan, a drug for the genetic disorder phenylketonuria (PKU), and subsequently lowering sales and profit expectations.

The stock traded down 3.3% to $34.47.

Also, HSBC Securities downgraded Novartis ( NVS) to underweight from neutral and lowered its price target to $49 from $52. The stock was off by just 8 cents, or 0.2%, at $50.35.

In other health stocks, Lehman Brothers downgraded Lifepoint Hospitals ( LPNT) to equal-weight from overweight but the stock was seemingly unaffected, adding 83 cents, or 2.9%, to $29.77.

And Tenet Healthcare ( THC) added 39 cents, or 7.4%, to $5.69 after Lehman Brothers analyst Adam Feinstein upgraded the stock to overweight from equalweight, citing new contracts and potential growth despite industry hardships.

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