Bovine oocyte diameter in relation to maturational competence and transcriptional activity

Abstract

The aims of the present series of experiments were to establish a possible relationship between bovine oocyte diameter and follicle size, investigate the developmental ability of oocytes of different diameter groups, and investigate the relationship between oocyte diameter and RNA transcriptional activity of the oocyte. Follicles were recovered from slaughterhouse ovaries by mechanical dissection, measured, and assigned to one of the following size categories: > or = 4 mm, < 3-4 mm, < 2-3 mm, < 1-2 mm, and < 1 mm. Oocytes were liberated from the follicles and their diameters recorded. The correlation coefficient between oocyte diameter and follicle size was 0.32 (P < 0.0001). Oocytes were recovered by aspiration and/or slicing of slaughterhouse ovaries and divided into four groups ( < 100 microns, 100- < 110 microns, 110- < 120 microns, and > 120 microns) based on diameter. Oocytes were processed through standard procedures for in vitro maturation and stained in order to assess nuclear development. Rates of in vitro development to metaphase II were 21.2%, 42.3%, 75.9%, and 80.7%, respectively, for the four groups. On a separate occasion immature oocytes from the above diameter groups were cultured in the presence of 3H-uridine for 45 min and scored for degree of RNA synthesis as indicated by the presence of autoradiographic labeling. Oocytes < 110 microns showed a greater degree of 3H-uridine incorporation than those > or = 110 microns, suggesting that they were involved in RNA synthesis and therefore still in the growth phase.

Temporal detection of caspase-3 and -7 in bovine in vitro produced embryos of different developmental capacity

“…Although previous studies in bovine have linked oocyte diameter and early developmental kinetics with blastocyst formation and viability (Van Soom et al 1992, Grisart et al 1994, Fair et al 1995, Otoi et al 1997, their relation with the incidence of apoptosis during embryo development remains unexplored. Suboptimal culture conditions undoubtedly contribute to embryonic apoptosis, but the intrinsic quality of the oocyte and the embryo may also be a causative factor.…”

Follicular size affects the meiotic competence of in vitro matured prepubertal and adult oocytes in sheep

“…This can be related to defective conditions of oocyte maturation and can also be due to the reduced size of oocytes and follicular population [17] and a small size of volume fractions of mitochondria and cortical granules [25]. Several studies in other domestic species [6,11,23] …”

Impact of pro‐oxidant agents on the morula‐blastocyst transition in bovine embryos

“…Oocyte diameter has been correlated with competence for nuclear maturation (De Smedt et al, 1994) and for early development following fertilization (Crozet et al, 1995;Fair et al, 1995). A positive correlation between oocyte and follicle sizes has been demonstrated (Fair et al, 1995). Oocytes from large follicles have a better developmental competence and embryos derived from these oocytes exhibit an earlier cavitation process than those derived from small follicles (Lequarre et al, 2005).…”