The S&P 500 rose 0.66% to 1,793.21 in afternoon trading Thursday.
The Dow Jones Industrial Average was up 0.57% to 15,992.20, while the Nasdaq was up 0.93% to 3,957.73.
The yield on a 10-year Treasury bond was off 0.07% to 2.79%.
The price of gold was down 1.12% to $1,243.90 per ounce.
Irvine heart valve maker Edwards Lifesciences Corp. rose about 3% to $64.78 for a market value of $7.09 billion. Rival medical device maker Medtronic Inc. reported second-quarter earnings this week that came in slightly above consensus estimates and sales in line with Wall Street analysts.
Shares of Irvine-based molecular diagnostics company CombiMatrix Corp. surged about 69% to $3.95 on news announced Thursday that it will cover diagnostic laboratory services provided through San Diego-based America's Choice Provider Network. CombiMatrix had a recent market value of $18.72 million.
Huntington Beach-based BJ's Restaurants Inc. was up about 4% to $29.18 for a market value of $823.62 million. Restaurant companies, ranging from fast-food to casual dining operators, were generally up on Thursday.