NEW YORK ( TheStreet Ratings) -- TheStreet Ratings' stock model upgraded Ford Motor ( F - Get Report) to 'Buy' from 'Hold'. Net income at this $57.3 billion market cap, vehicle & parts maker grew by 22.4% to a profit of $2.6 billion compared to in the prior first quarter.

TheStreet Ratings released rating changes on 27 U.S. common stocks for May 11, 2011. In total, 15 stocks were upgraded and 12 stocks were downgraded by our stock model.

In the first quarter, Ford Motor reported $33.1 billion in revenue, an increase of 4.9% compared to the year earlier quarter. Learn more about Ford Motor: Company Profile, Income Statement, Balance Sheet, Stock Ratios, Analyst Ratings.

$3.6 billion market cap, medical device company, Mindray Medical International ADR ( MR - Get Report) was upgraded by our stock model to 'Buy' from 'Hold'. In first quarter results, Mindray Medical International net profit of $37.7 million, up by 4.2% compared to the year earlier quarter. Over the same time period, revenue gained 24% to $181 million. Learn more about Mindray Medical International: Company Profile, Income Statement, Balance Sheet, Stock Ratios, Analyst Ratings.

-- Reported by Kevin Baker in Jupiter, FL.

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Kevin Baker became the senior financial analyst for TheStreet Ratings upon the August 2006 acquisition of Weiss Ratings by TheStreet.com, covering equity and mutual fund ratings. 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.