FERTILIZATION COMPETENCE OF BOVINE NORMALLY MATURED OR AGED OOCYTES DERIVED FROM DIFFERENT ANTRAL FOLLICLES - MORPHOLOGY, PROTEIN-SYNTHESIS, H1 AND MBP KINASE-ACTIVITY

We have investigated the fertilisation competence, protein synthesis, histone H1 kinase and myelin basic protein (MBP) kinase activities in three categories of bovine oocytes (derived from three size categories of follicles: M - medium, 2.5-5.0 mm; S - small, 1.5-2.5 mm; T - tiny , 1.0-1.5 mm). In contrast to more or less normal meiotic maturation ( 85.6%) and fertilisation (70.8%) of M oocytes cultured for 24 h, the f ertilisation of M oocytes cultured for 40 h was associated with increa sed rates of retarded male pronuclear development and retention of the second polar body. The S and T oocytes cultured for 24 h or 40 h were mostly arrested at defective late diakinesis - metaphase I (77.5-100% ) stage. After fertilisation of S and T oocytes cultured for 24 h no p olar body was extruded and formation of one, three or four female pron uclei, together with mostly normal male pronuclei, was observed. The f ertilisation of S and T oocytes after 40 h culture resulted in a highe r number of female and a decreased number of male pronuclei. A major c hange in the pattern of protein synthesis was associated with the resu mption of meiosis. There were no significant differences in the profil e of protein synthesis between oocyte categories in all groups either matured or fertilised. The H1 kinase activity reached comparable incre ased levels in oocytes of all categories matured for 24 h and decrease d during the 40 h culture, most significantly in M oocytes. The MBP ki nase activity was at approximately the same high level in all categori es of oocytes after 24 h of culture and remained stable until 40 h. Th e fertilisation after 24 h of culture resulted, in M oocytes, in low l evels of both H1 and MBP kinase activities; in S oocytes, only H1 kina se was completely inactivated while MBP kinase activity decreased to s ome extent; in T oocytes, both H1 and MBP kinase activity decreased. F ertilisation of all oocyte categories after 40 h culture resulted in c omplete inactivation of both these kinases to their basal levels.