captioning sponsored by macneil/lehrer productions >> woodruff: the food and drug administration said today companies may soon have to eliminate artery-clogging artificial trans fats from their products. good evening. i'm judy woodruff. >> ifill: and i'm gwen ifill. also ahead this thursday, wall street's all a-twitter. the social media giant goes public, turning 140-character messages into a company now valued in the tens of billions. >> woodruff: and in one colorado county, health insurance costs are much higher than in the rest of the state, complicating the push to get the uninsured signed up for new plans.