Shares in Gemstar-TV Guide International Inc. slipped 6.8 percent to $4.65 Monday after shares in the media company were downgraded to “market perform” from “buy” by analyst April Horace at Janco Partners Inc. Shares in the Los Angeles-based company slid 16 percent last week after investors showed displeasure with a proposed $2.8 billion acquisition, announced Friday, by media company Macrovision Corp.