New York, June 21^th (TradersHuddle.com) – Following are some of the top changes in analysts’ ratings before the market open.

Research Firms Initiate:

Niska Gas Storage (NYSE:NKA), the independent owner and operator of natural gas storage assets in North America, was initiated with an Outperform at Credit Suisse.

Upgrades:

Amylin Pharmaceuticals (NASDAQ:AMLN), the biopharmaceutical company that discovers, develops, and commercializes medicines for diabetes and obesity, was upgraded to Hold from Sell at Canaccord.

Andersons (NASDAQ:ANDE), the agricultural distributor and grain merchandiser, was upgraded to Buy from Hold at BB&T.

Diamondrock Hospitality (NYSE:DRH), the upscale hotel REIT, was upgraded to Buy from Hold at Citigroup.

Kforce, Inc. (NASDAQ:KFRC), the full-service, professional staffing firm, was upgraded to Outperform from Neutral at Credit Suisse.

Medical Properties Trust (NYSE:MPW), the healthcare facilities REIT, was upgraded to Market Perform from Underperform at Wells Fargo.

ProLogis (NYSE:PLD), the industrial and distribution space provider, was upgraded to Market Perform from Underperform at Wells Fargo.

QuinStreet (NASDAQ:QNST), the vertical marketing and internet Media Company, was upgraded to Overweight from Market Weight at Thomas Weisel.

Robert Half (NYSE:RHI), the largest specialized staffing services firm in the world, was upgraded to Outperform from Neutral at Credit Suisse.

Thompson Creek Metals (NYSE:TC), the miner and processor of molybdenum, was upgraded to a Buy from Neutral at UBS.

Universal Display (NASDAQ:PANL), high-resolution, full color, light weight Organic Light Emitting Diode (OLED) technology, was upgraded to Outperform from Neutral at Cowen.

Downgrades:

Ameristar Casinos  (NASDAQ:ASCA), the gaming company that owns and operates casinos resorts in several states in the U.S., was downgraded to Hold from Buy at KeyBanc.

FirstEnergy (NYSE:FE), the diversified energy company, was downgraded to a Hold from Buy at Citigroup.

Lazard (NYSE:LAZ), the provider of domestic and international financial advisory services and global transaction execution to corporations, was downgraded to Neutral from Buy at Goldman.

OpenTable  (NASDAQ:OPEN), the restaurant reservation website operator, was downgraded to a Hold from Buy at Citigroup.

Terremark Worldwide (NASDAQ:TMRK), the provider of information technology infrastructure services, was downgraded to Hold at The Benchmark Company.

TreeHouse Foods (NYSE:THS), the food maker, was downgraded to Neutral from Buy at SunTrust.