US STOCKS-Sigma-Aldrich, Dresser-Rand among premarket actives

NEW YORK, Sept 22 (Reuters) - Sigma-Aldrich shares were surging on Monday, up 34.4 percent to $137.60 after German drugs and chemicals maker Merck KGaA said on Monday it agreed to acquire Sigma-Aldrich for $17 billion in cash to boost its life science business.