NEW YORK ( TheStreet) -TheStreet Ratings' stock model upgraded Polycom ( PLCM) to 'Buy' from 'Hold'. This independent videoconferencing company reported record net revenue of $295 million in the second quarter, up from $231 million a year earlier.

TheStreet Ratings released rating changes on eight additional U.S. common stocks for July 15, 2010. In all, six stocks were downgraded and three stocks have been upgraded by our stock model.

Polycom shares sold off on the earnings news as net income contracted to $13 million from $15 in the second quarter of 2009 and the company failed to meet consensus earnings estimates. This may present a more attractive entry point for the stock. The company competes against Cisco Systems ( CSCO) and is in a revenue generating, collaborative network with Microsoft ( MSFT), IBM ( IBM), and Hewlett-Packard ( HPQ).

On the flip side dropping to 'Hold' from 'Buy' is Questar ( STR), a $2.8 billion market cap natural gas utility with pipeline and production units. The shares have trended higher since the announcement of its gas exploration spin-off of QEP Resources prompting the full valuation call by the stock model.

-- Reported by Kevin Baker in Jupiter, Fla.

For additional Investment Research check out our Ratings Research Center.

Kevin Baker became the senior financial analyst for TheStreet Ratings upon the August 2006 acquisition of Weiss Ratings by TheStreet.com, covering mutual funds. He joined the Weiss Group in 1997 as a banking and brokerage analyst. In 1999, he created the Weiss Group's first ratings to gauge the level of risk in U.S. equities. Baker received a B.S. degree in management from Rensselaer Polytechnic Institute and an M.B.A. with a finance specialization from Nova Southeastern University.

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