Sen. Bernie Sanders was among eight senators who called Wednesday for regulators to reject Wall Street and financial industry efforts to block federally mandated requirements to end excessive speculation by investors in oil and food.  Such speculation is blamed by many economists for sudden price hikes in gasoline and other essential consumer goods. Congress last year passed legislation directing the Commodity Futures Trading Commission to impose limits on the amount of speculative investment in oil, wheat and other physical commodities.  Wall Street firms are trying to block the new rules before they ever get off the ground.  The commission meets Thursday to discuss how and when to implement so-called position limits on commodities speculators. “We urge you to reject calls to delay the new rules,” according to the letter circulated by Sens. Bill Nelson and Maria Cantwell and signed by Carl Levin, Robert Menendez, Patty Murray, Sheldon Whitehouse and Ron Wyden.