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Evaluation of developmental competence, nuclear and ooplasmic maturation of calf oocytes
Author(s) -
Damiani P.,
Fissore R.A.,
Cibelli J.B.,
Long C.R.,
Balise J.J.,
Robl J.M.,
Duby R.T.
Publication year - 1996
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/(sici)1098-2795(199612)45:4<521::aid-mrd15>3.0.co;2-z
Subject(s) - biology , oocyte , human fertilization , andrology , gamete , meiosis , insemination , zygote , sperm , polar body , polyspermy , anatomy , embryogenesis , microbiology and biotechnology , embryo , genetics , medicine , gene
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 Ca 2+ responses of calf oocytes to the addition of agonists or after IVF. The addition of thimerosal demonstrated the presence of Ca 2+ stores in calf oocytes. Injection of near threshold concentrations of inositol 1,4,5‐trisphosphate (InsP 3 ), used to test the sensitivity of the InsP 3 R, released significantly less Ca 2+ in calf than in cow oocytes, whereas higher concentrations of InsP 3 (500 μM) released maximal [Ca 2+ ]i in both oocytes. These results suggested that the Ca 2+ content of intracellular stores was similar, but the sensitivity of the InsP 3 R may be different. Following insemination, calf oocytes exhibiting [Ca 2+ ]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.