Evaluation of developmental competence, nuclear and ooplasmic maturation of calf oocytes

Abstract

In this study we evaluated nuclear and ooplasmic maturation of prepuberal calf oocytes to determine a possible cause for their low developmental competency. Calf oocytes resumed meiosis and arrested at the MII stage at rates similar to that of adult animals; however, zygotes derived from calf oocytes cleaved and developed at significantly lower rates. Ooplasmic maturation was assessed during oocyte maturation and fertilization. Transmission electron microscopy revealed that a majority of calf oocytes exhibited some delay in organelle migration and redistribution following maturation. Immunofluorescence microscopy showed that following IVF, a higher percentage of calf oocytes had abnormal chromatin and microtubule configurations than those of adult cattle. These anomalies were characterized by delayed formation of sperm aster and asynchronous pronuclear formation. Microfluorometry was used to characterize the Ca2+ responses of calf oocytes to the addition of agonists or after IVF. The addition of thimerosal demonstrated the presence of Ca2+ stores in calf oocytes. Injection of near threshold concentrations of inositol 1,4,5‐trisphosphate (InsP3), used to test the sensitivity of the InsP3R, released significantly less Ca2+ in calf than in cow oocytes, whereas higher concentrations of InsP3 (500 μM) released maximal [Ca2+]i in both oocytes. These results suggested that the Ca2+ content of intracellular stores was similar, but the sensitivity of the InsP3R may be different. Following insemination, calf oocytes exhibiting [Ca2+]i oscillations displayed comparable amplitude and intervals to cow oocytes; however, a significantly higher number of fertilized calf oocytes failed to show oscillations. Our findings suggest that the low developmental competence of calf oocytes can be attributed, at least in part, to incomplete or delayed ooplasmic maturation. © 1996 Wiley‐Liss, Inc.

Effects of cryodevice type and donors' sexual maturity on vitrification of minke whale (Balaenoptera bonaerensis) oocytes at germinal vesicle stage

“…Differences between prepubertal and adult oocytes have been characterized by different patterns in neosynthetic proteins (Khatir et al, 1998) and energy metabolism (Gandolfi et al, 1998), cytoplasmic organelle migration (Damiani et al, 1996) and reduced activity of some enzymes (Driancourt et al, 2001). Thus, a lower capacity to complete meiosis in oocytes derived from prepubertal whales may be supported by these findings.…”

Impact of endocrine disrupters on ovarian function and embryonic development

“…It is characterized by ultrastructural and spatial rearrangements of the ooplasm as well as by chemical changes of the molecules stored therein [58,59]. For this reason, in our recent studies, a set of experiments was designed to examine the effects of the exposure of bovine oocytes to a dose of Aroclor-1254 known to be detrimental to nuclear maturation and subsequent embryo development, on two important aspects of the cytoplasmic maturation of bovine oocytes: modulation of maternal mRNA polyadenylation [60] and cortical granules (CGs) migration and exocytosis [61].…”

The <i>In Vitro</i> Developmental Competence of Oocytes from Juvenile Calves is Related to Follicular Diameter

“…It has been shown that follicular waves already start shortly after the birth of calves [14,15], and follicles of different size harbouring fertilizable oocytes are regularly observed [16,17,18]. Calf o o c y t e s h a v e b e e n s h o w n t o b e l e s s developmentally competent than their adult counterparts [19], and this limits the successful use of juvenile calves for commercial in vitro embryo p r o d u c ti o n w i t h t h e g o al o f r e d u c i n g t h e generation interval and accelerating the rate of genetic gain [20].…”