its true NEW YORK (AP) -- Moody's Investors Service raised its credit rating for Life Technologies Corp. on Tuesday to investment grade. Moody's raised its rating on $2.3 billion of the life science and medical research instrument maker's debt to Baa3 from Ba1, which was speculative, or "junk," status. It changed its outlook for Life Technologies' rating from positive to stable. Moody's said the Carlsbad, Calif., company has reported stable operating performance and reduced its debt over the years, and it may become more aggressive with acquisitions and stock repurchases. Life Technologies shares declined 76 cents to close Tuesday at $45.65 and lost another 13 cents after hours. The company was formed through the combination of Invitrogen Corp. and Applied Biosystems Inc. in November 2008.