Shares of two media companies rose in their stock market debuts Wednesday after raising more than expected in their initial public offerings.

Shares of Nielsen Holdings, the consumer measurement firm known for its dominance in television ratings, were at $25.28, 9.9 percent above their $23 IPO price in early trading on the New York Stock Exchange, while shares of online media company Demand Media Inc were at $23.50, or 38.2 percent above their $17 IPO price.

Nielsen raised $1.6 billion, 9.5 percent more than expected in its IPO. It also sold $250 million worth of mandatory convertible subordinated bonds alongside the IPO.

Demand Media, an online company that relies on an army of freelance writers to churn out articles and video designed to appear at the top of Web searches, raised $151.3 million, 34.5 percent more than expected.

Nielsen's capital raise is the first of what is expected to be a rush of big private equity-backed IPOs in 2011 and its performance could set a positive tone for other buyout-backed IPO candidates including Toys R Us, hospital operator HCA and pipeline company Kinder Morgan.

Nielsen was taken private in 2006 in a deal worth just over $10 billion by private equity firms Carlyle Group, Blackstone Group LP, Kohlberg Kravis Roberts & Co., Thomas H. Lee Partners, AlpInvest Partners and Hellman & Friedman.

Underwriters on the Nielsen IPO were led by JPMorgan and Morgan Stanley, while Goldman Sachs and Morgan Stanley led the underwriters on the Demand Media IPO.