NEW YORK, March 25 /PRNewswire/ -- Standard & Poor's will make the following changes to the S&P 500, S&P MidCap 400 and S&P SmallCap 600 indices after the close of trading on Wednesday, April 1:

• S&P MidCap 400 constituent Denbury Resources Inc. (NYSE: DNR) will replace Rohm and Haas Co. (NYSE: ROH) in the S&P 500, and Corporate Office Properties Trust (NYSE: OFC) will replace Denbury Resources in the S&P MidCap 400. S&P 100 & 500 constituent The Dow Chemical Corp. (NYSE: DOW) is acquiring Rohm and Hass in a transaction expected to be completed on or about that date.

• S&P SmallCap 600 constituent Cleco Corp. (NYSE: CNL) will replace Belo Corp. (NYSE: BLC) in the S&P MidCap 400, and Pinnacle Financial Partners Inc. (Nasdaq: PNFP) will replace Cleco in the S&P SmallCap 600. As of today's close of trading Belo had a market capitalization of $81 million, ranking it 400th in the index.

Standard & Poor's will monitor these transactions, and post any relevant updates on its website: www.standardandpoors.com.

Denbury Resources is engaged in the acquisition, development, operation and exploration of oil and natural gas properties. Headquartered in Plano, TX, the company will be added to the S&P 500 GICS (Global Industry Classification Standard) Oil & Gas Exploration & Production Sub-Industry index.

Corporate Office Properties is a specialty office real estate investment trust (REIT). Headquartered in Columbia, MD, the company will be added to the S&P MidCap 400 GICS Office REITs Sub-Industry index.

Cleco is a public utility company. Headquartered in Pineville, LA, the company will be added to the S&P MidCap 400 GICS Electric Utilities Sub-Industry index.

Pinnacle Financial operates as a community bank primarily in urban markets. Headquartered in Nashville, TN, the company will be added to the S&P SmallCap 600 GICS Regional Banks Sub-Industry index.