WASHINGTON (AP) — Casting its first votes on revamping the nation’s health care system, the Senate rejected a Republican bid Thursday to stave off Medicare cuts and approved safeguards for coverage of mammograms and other preventive tests for women. The first round of votes ended with a fragile Democratic coalition hanging together.Senators voted 58-42 to reject an amendment by Sen. John McCain, R-Ariz., that would have stripped more than $400 billion in Medicare cuts from the nearly $1 trillion measure. It would have sent the entire 2,074-page bill back to the Senate Finance Committee for a redo.