▁began ▁his ▁academic ▁career ▁in ▁the ▁U . S . ▁as ▁an ▁assistant ▁professor ▁of ▁surg ery ▁at ▁the ▁University ▁of ▁Minnesota . ▁Five ▁years ▁later , ▁he ▁was ▁promoted ▁to ▁full ▁professor ▁with ▁ten ure . ▁Gru ess ner ▁returned ▁to ▁Europe ▁for ▁one ▁year ▁to ▁become ▁Chair man ▁of ▁the ▁Department ▁of ▁General ▁and ▁Trans plant ▁S urg ery ▁at ▁the ▁University ▁of ▁Zur ich ▁in ▁Zur ich , ▁Switzerland . ▁ ▁In ▁ 1 9 9 9 , ▁Gru ess ner ▁returned ▁to ▁the ▁U . S . ▁to ▁assume ▁the ▁roles ▁of ▁Vice - Ch air ▁of ▁the ▁Department ▁of ▁S urg ery ▁and ▁Vice ▁Chief ▁of ▁the ▁Division ▁of ▁Trans plant ation ▁at ▁the ▁University ▁of ▁Minnesota . ▁While ▁in ▁Minnesota , ▁he ▁and ▁his ▁team ▁performed ▁the ▁state ' s ▁first ▁living ▁don or ▁li ver ▁trans plant , ▁first ▁living ▁don or ▁int est inal ▁trans plant , ▁first ▁combined ▁living ▁don or ▁int est inal ▁and ▁li ver ▁trans plant , ▁and ▁first ▁mult iv is cer al ▁trans plant . ▁His ▁focus ▁on ▁living ▁don or ▁trans plant ation ▁was ▁boost ed ▁in ▁ 1 9 9 6 ▁when ▁he ▁received ▁additional ▁training ▁in ▁living ▁don or ▁trans plant ation ▁at ▁the ▁University ▁of ▁Ky oto ▁in ▁Ky oto , ▁Japan . ▁ ▁In ▁ 2 0 0 7 , ▁Gru ess ner ▁was ▁appointed ▁Chair man ▁of ▁the ▁Department ▁of ▁S urg ery ▁at ▁the ▁University ▁of ▁Arizona . ▁He ▁also ▁served ▁as