NEW YORK (TheStreet) -- RATINGS CHANGES

American International Group (AIG - Get Report) was downgraded to hold from buy by Deutsche Bank, which cited valuation, based on a 12-month price target of $64.

Avalanche (AAVL) was downgraded to market perform by William Blair, which set a 12-month price target of $24, saying the company had lower secondary efficacy with its Phase II-a trial.

Corning (GLW - Get Report) was upgraded to outperform by RBC Capital, which set a 12-month price target of $26, saying the company is leveraged to the upcoming 4K television upgrade cycle.

Digital Realty Trust (DLR - Get Report) was upgraded by TheStreet Ratings team. You can view the full analysis from the report here: DLR Ratings Report.

Laboratory Corp. (LH - Get Report) was started at overweight by Keybanc, which set a 12-month price target of $143, saying the company is attractively valued, relative to its accelerating growth.

Methode Electronics (MEI - Get Report) was downgraded to neutral from outperform by Robert Baird, which said the stock has performed well, but to expect growth to decelerate in the coming quarters.

Oaktree Capital (OAK - Get Report) was upgraded to buy by TheStreet Ratings team. You can view the full analysis from the report here: OAK Ratings Report.

Standard Pacific (SPF) was downgraded to neutral from outperform by Credit Suisse, which set a 12-month price target of $9.50, saying the merger with Ryland Group (RYL) carries high integration risk.

Twitter (TWTR - Get Report) was downgraded to neutral from buy by MKM Partners, which set a 12-month price target of $39. MKM said that Twitter has long-term potential and significant upside if the company executes on user experience improvement, but that there are no catalysts for improving sentiment in the next two quarters, besides a possible deal with Google (GOOGL - Get Report).

United Natural (UNFI - Get Report) was downgraded to hold from buy by Argus on expectations of lower margins in the coming quarters.