Ryota Murata, the first Japanese boxer to win both an Olympic and professional world championship, said Wednesday he has effectively retired.The 37-year-old middleweight lost his WBA super world belt to IBF champion Gennadiy Golovkin of Kazakhstan last April in a ninth-round technical knockout in their title unification bout."Inside my head I'm thinking, 'that was my last,'" Murata said of the defeat. "I just haven't been able to announce it (until now), but that's how I'm thinking personally."The Nara Prefecture native won silver at the 2011 world championships before seizing an Olympic go…READ FULL ARTICLE