Stocks making the biggest moves midday: Berkshire Hathaway, Micron, Tyson Foods, Spirit Airlines and more

cnbc.com:

Check out the companies making headlines in midday trading:

Berkshire Hathaway — Class A shares added 0.6% following the release of first-quarter results and the annual shareholders meeting on Saturday. Berkshire posted a 39% yearly jump in operating profit, while cash holdings are approaching $200 billion.

Micron Technology — The Boise, Idaho-based semiconductor company jumped 4.5% following an upgrade from Baird to outperform from neutral. The analyst cited valuation, incrementally positive trends in dynamic random-access memory, or DRAM, pricing and growing demand for high-bandwidth memory.

Spirit Airlines — The discount carrier slid 9% after posting a loss of $1.46 per share in the first quarter, wider than a FactSet consensus estimate from analysts of a $1.45 loss per share. Revenue matched expectations. Spirit also forecast second-quarter revenue between $1.2 billion and $1.34 billion, below a FactSet estimate of $1.46 billion.

Paramount — Shares popped 3.3% following a report that the owner of Paramount Pictures and CBS Entertainment Group began formal acquisition negotiations with a group led by Sony Pictures Entertainment and Apollo. Elsewhere, Warren Buffett said over the weekend that he sold the entire Berkshire stake in Paramount at a loss.

United States Steel — The Pittsburgh-based steelmaker saw its shares rise more than 2% after Morgan Stanley upgraded it to overweight from equal weight. U.S. Steel shares have room to rise due to internal improvements, even if the Nippon Steel buyout deal collapses, Morgan Stanley said in a note.

Medical Properties Trust — Shares dropped nearly 7% after a major tenant of the company's, the physician-owned hospital operator Steward Health Care, filed for Chapter 11