BUZZ-Sainsbury's: strong Christmas performance

** J Sainsbury leads gains among UK supermarketretailers after reporting better than expected Christmasquarter

** Sainsbury's up 4.2 pct, top FTSE 100 riser & 2ndbusiest stock on index with 1/4 of 90-day daily avg volumealready traded

** Stock fallen more than 30 pct over last yr amid loss ofshare to discounters and intensifying industry price war

** Tesco & M&S, set to release Q3 updateson Jan 8, both up more than 2 pct, while Wm Morrison advances 2 pct (RM: tricia.wright1.thomsonreuters.com@reuters.net)