Sept 30 (Reuters) - Wall Street"s main indexes opened higher on Thursday at the end of a bruising month on upbeat economic growth data, while investors focused on funding negotiations in Washington to prevent a government shutdown. The Dow Jones Industrial Average (.DJI) rose 77.26 points, or 0.22%, at the open to 34,467.98. The S&P 500 (.SPX) opened higher by 11.21 points, or 0.26%, at 4,370.67, while the Nasdaq Composite (.IXIC) gained 70.16 points, or 0.48%, to 14,582.60 at the opening bell.