The S&P 500 was down 0.3% in midday trading to 2,173.80.
The Dow Jones Industrial Average was down 0.4% to 18,435.16.
The NASDAQ was down 0.4% to 5,213.62.
The yield on a 10-year Treasury bond was up 0.5% to 1.57%.
The price of gold was down 0.9% to $1,316.
Irvine-based Biolase Inc. was up 9% to $1.80 and a $105 million market cap on high volume. The dental laser maker had by midday traded shares at a rate four times its 90-day average.
Santa Ana-based BioLargo Inc. was up 14% to 87 cents and a $76 million market cap on high volume. The maker of disinfectant products for water and wound healing had by midday traded shares at a rate twice its 90-day average.