Ariel Investments, a Chicago-based personal equity fund, has increased its stake holding in Manchester United beyond 5% of the club's shares after completing a $100 million purchase of A-class shares.Sources have told ESPN, however, that the shares have been acquired through United's listing on the New York Stock Exchange (NYSE) and that the club's American owners, the Glazer family, have not traded any of their shares in the club.Ariel is reported to have assets of $15 billion and the company has been acquiring shares in United over a lengthy period of time. NYSE rules stipulate that they make a regulatory disclosure after taking their stake beyond the 5% threshold.Despite prominent protests against the Glazers by the United fans last season, which included the postponement of a Premier League clash against Liverpool in May after supporters invaded Old Trafford prior to the game, sources have said the the family, who also own Super Bowl champions Tampa Bay Buccaneers, have no plans to end their ownership of the club, which dates back to 2005.The Glazers own virtually all of United's B class shares which carry voting rights, as opposed to the less significant A shares.This summer the Glazers sanctioned a spending spree in excess of £130m ON Raphael Varane, Jadon Sancho and Cristiano Ronaldo.