A new CEO and mention of a stock offering lifted two health companies Wednesday while others were scathed by negative news. Medical device company DexCom ( DXCM) climbed 45 cents, or 6.5%, to $7.30 Wednesday after it announced that Terrance Gregg, chief executive at the Canadian biotechnology company Vasogen ( VSGN) and former vice president of Medtronic, will take over as president and chief executive in place of Andy Rasdal, who's stepping down. Gregg will remain chairman of Vasogen's board, and CEO Rasdal who will remain a board member and advisor during the transitio Vasogen, which was down 17 cents, or 6.3%, to $2.53, named former COO and CFO Chris Waddick president and chief executive. On the other end of the spectrum from Vasogen, Protalix BioTherapeutics ( PLX) rocketed 31% after announcing that its board of directors authorized it to prepare a registration statement for the Securities and Exchange Commission for a common stock offering during the second half of 2007. The company gave no hints to the offering's size or price, but its stock price leapt $6.54 to $27.13 regardless.