The S&P 500 was down 0.1% in midday trading to 2,180.47.
The Dow Jones Industrial Average was down 0.1% to 18,519.73.
The NASDAQ was down 0.2% to 5,208.22.
The yield on a 10-year Treasury bond was up 0.4% to 1.59%.
The price of gold was down 0.2% to $1,341.
Irvine-based Biolase Inc. was up 13% to $1.43 and an $83 million market cap on above-average volume. The company makes dental lasers.
Santa Ana-based BioLargo Inc. was up 43% to 82 cents and an $80 million market cap on high volume. The company makes water filtration products.