sao paulo jan 5 reuters  brazilian investment firm mam asset management controlled by tycoon nelson tanure said late on tuesday it plans to make a public acquisition offer for 100 of medical diagnostics company alliar aalr3sa if it reaches a controlling stake in the firm current controlling shareholders of alliar formally known as centro de imagem diagnosticos sa aalr3sa have agreed to sell up to 5275 of the company to tanure but its bylaws determine that any investor to hold a stake of more than 50 is required to present a takeover bid for the whole firm despite the 5275 threshold tanures investment firm noted in a letter that some of the current controlling shareholders will be allowed to remain in the company under the deal implying the poison pill could not be triggered minority shareholders have expressed discontent with the move as tanure would not be necessarily required to also bid for their stakes a substantial part of the current controlling shareholders is formed by doctors who founded alliar or companies acquired by it they have expertise in the industry and thus add value to alliar mam said  though adding they will have the option to sell their stakes to the fund in the future it is certain that if the amount of stocks acquired by the fund implies changing the companys control the fund will immediately present a public acquisition offer as required by the rules it said alliar had previously announced mam will pay the controlling block 2050 reais 361 per share in the company whose stocks closed at 1351 reais on tuesday