Nikkei gains helped by strong U.S. growth; parliament in focus

* U.S. GDP underpins sentiment * Parliament session may provide catalyst - analysts * SoftBank's M&A news has limited impact on stock By Ayai Tomisawa TOKYO, Sept 29 (Reuters) - Japan's Nikkei share average rose on Monday morning after the weak yen supported sentiment, while risk taking was buoyed after the U.S. economy grew at its fastest pace in 2-1/2 years in the second quarter. The Nikkei share average gained 0.5 percent to 16,310.63 in mid-morning trade after falling 0.