* Alcoa to report Q2 results after bell; loss expected
* Google to launch operating system; shares rise
* Dow up 0.5 pct, S&P up 0.4 pct, Nasdaq up 0.3 pct
(Updates to mid-morning)
By Rodrigo Campos
NEW YORK, July 8 (Reuters) - U.S. stocks rose on Wednesday as investors scooped up bargains in the commodities sectors a day after Wall Street slid to a 10-week low, but sentiment was dampened by the start of the quarterly earnings season.
Amgen Inc shares shot up 16 percent to $60.59, one day after the biotechnology company reported positive results for its experimental osteoporosis drug. The S&P healthcare index rose 1.2 percent.
Investors were reticent to buy aggressively after Tuesday's selloff as uncertainty over second-quarter earnings loomed. Alcoa Inc, the first Dow component to report, is expected to post its third consecutive quarterly loss after markets close on falling demand for aluminum. Alcoa rose 2.1 percent to $9.61.
After a rally that took the S&P 500 index up 40 percent from 12-year lows in early March, traders are looking for hard evidence that the economy will rebound from a deep recession.
David Sowerby, market strategist for Loomis Sayles in Detroit, said the 2 percent drop in the S&P 500 was prompting tepid buying, but cited anxiousness over earnings.
"Given that the more important economic numbers have been soft the last two weeks, it's been somewhat of a cold shower for earnings expectations," he said.
The Dow Jones industrial average rose 36.42 points, or 0.45 percent, to 8,200.02. The Standard & Poor's 500 Index added 3.64 points, or 0.41 percent, to 884.67. The Nasdaq Composite Index gained 5.31 points, or 0.30 percent, to 1,751.48.
Raw materials was the leading sector in the S&P 500, up nearly 1 percent after a 2.5 percent slide on Tuesday.
Microsoft Corp was the biggest drag on the Dow industrials. Google Inc said it will launch a new operating system in the second half of 2010, taking on Microsoft's core business.
Microsoft shares fell 1 percent to $22.30, while Google rose 1.6 percent to $403.09.
Leaders of the Group of Eight richest nations and the major developing powers gathered for a three-day summit in Italy. They are expected to agree the world's economy is still too weak to remove stimulus measures.