Fertilisation competence of bovine normally matured or aged oocytes derived from different antral follicles: morphology, protein synthesis, H1 and MBP kinase activity

Abstract

We have investigated the fertilisation competence, protein synthesis, histone HI 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 fertilisation of M oocytes cultured for 40 h was associated with increased 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 polar body was extruded and formation of one, three or four female pronuclei, together with mostly normal male pronuclei, was observed. The fertilisation of S and T oocytes after 40 h culture resulted in a higher number of female and a decreased number of male pronuclei. A major change in the pattern of protein synthesis was associated with the resumption of meiosis. There were no significant differences in the profile of protein synthesis between oocyte categories in all groups either matured or fertilised. The HI kinase activity reached comparable increased levels in oocytes of all categories matured for 24 h and decreased during the 40 h culture, most significantly in M oocytes. The MBP kinase activity was at approximately the same high level in all categories of oocytes after 24 h of culture and remained stable until 40 h. The fertilisation after 24 h of culture resulted, in M oocytes, in low levels of both HI and MBP kinase activities; in S oocytes, only HI kinase was completely inactivated while MBP kinase activity decreased to some extent; in T oocytes, both HI and MBP kinase activity decreased. Fertilisation of all oocyte categories after 40 h culture resulted in complete inactivarion of both these kinases to their basal levels.

Effect of Oocyte Aging on Parthenogenetic Activation with Cycloheximide and A Iteration of the Activity of Maturation Promoting Factor during Aging of Bovine Oocytes.

“…It has been reported that the decrease in MPF activity is involved in the initiation of oocyte activation, i.e. in exit from MII and pronuclear formation [40]. Consequently, it is thought that the reason for the higher activation rate in aged oocytes treated with low concentrations of CHX may be related to the rapid decrease below the limited level of MPF activity sufficient to maintain meiotic arrest, depending on the depression of the capacity of their oocytes to synthesize new cyclin B.…”

Phospho-Signaling at Oocyte Maturation and Fertilization: Set Up for Embryogenesis and Beyond Part I. Protein Kinases

“…Inhibiting an upstream phosphorylation event in the MBPK activation pathway the sea urchin embryo mitotic cycle at metaphase can be blocked (Pesando et al 1999). The MBPK activity was at approximately the same high level in all categories (medium, small and tiny) of bovine oocytes after 24 h of culture and remained stable until 40 h (Pavlok et al 1997;Pelech et al 1988;Sanghera et al 1990). …”

Activation of protein kinase C suppresses fragmentation of pig oocytes aged in vitro

“…The quality of oocytes can be improved by prolonged culture, that is, by culturing an oocyte for some time after it has reached the stage of metaphase II. Cattle oocytes cultured for an additional 16 h were used for in vitro fertilization (Pavlok et al, 1997), human oocytes cultured for an additional 48 h were used for cloning (Hall et al, 2007) or pig oocytes cultured for an additional 12 h were used for the production of parthenogenetic embryos (Jolliff and Prather, 1997). However, a culture prolonged beyond a certain critical period threatens oocytes with the complex process designated as ageing.…”